Patent Publication Number: US-10307921-B2

Title: Automated hair cutting system and method of operation thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a national stage application of PCT Application No. PCT/US12/70856, filed Dec. 20, 2012, which claims the benefit of U.S. Provisional Application Ser. No. 61/578,717 filed on Dec. 21, 2011; U.S. Provisional Application Ser. No. 61/610,021 filed on Mar. 13, 2012; and U.S. Provisional Application Ser. No. 61/677,532 filed on Jul. 31, 2012, all filed by Matthew W. Krenik, entitled “Automated Hair Cutting System,” commonly owned with this application and incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This application is directed, in general, to hair-cutting systems and, more specifically, to an automated hair-cutting system. 
     BACKGROUND 
     A very large number of professional barbers, hair stylists, and other professionals provide hair cutting services in most countries of the world. The importance in society of having well-groomed hair is highlighted by significant sums of money and time spent for these services. The substantial cost of a haircut and the time and inconvenience associated with getting one makes the idea of automated hair cutting systems attractive. Today, there are a number of systems available that provide guides, cutters, training materials, and other approaches to make it somewhat easier to cut hair without the need for extensive training. Regrettably, these systems are difficult to use for most people and often strictly limit the number of hair styles possible. Simple hair length guides, mechanical combs mounted on cutter heads, hair cutters mounted on vacuum hoses, and other common approaches do not allow people to generate most of the stylish and well-groomed results they seek. It is therefore desirable to have a system allowing a person without extensive training to accurately cut hair. 
     In light of the benefits an automated hair cutting system provides, several attempts at such a system have been made. In U.S. Pat. No. 3,054,183, Zucker teaches a mechanical guide that adjusts a cutter head as it is moved across a person&#39;s scalp. The simple, mechanical design Zucker offers does not allow a wide variety of hair styles, and its rolling wheels or sliding mechanical guides may tend to smash some hair down, making it harder to access and cut properly. In U.S. Pat. No. 3,413,985, Dlouhy teaches a helmet fitted over a person&#39;s head and aligned with ear retractors that insert into the person&#39;s ears. Multiple cutter heads are used inside the helmet to cut hair. Dlouhy teaches a rigid helmet, many cutter heads and a large, heavy mechanism that would necessarily be expensive, bulky, and uncomfortable to use. 
     In U.S. Pat. No. 4,602,542, Natrasevschi teaches a frame rigidly holding a person&#39;s head and a robotic arm that cuts hair. Hair length is controlled with an adjustable vacuum stretcher tube and rotary cutter tube. Such a system would be necessarily expensive, bulky, and uncomfortable. In addition, the end of Natrasevschi&#39;s hair cutter always touches the person&#39;s head so it may smash hair down and the maximum length that hair may be cut is physically limited by the length of the cutter tube and stretcher tube. Employment of longer tubes would make the hair cutter unwieldy and interchangeable tubes, while perhaps possible, would be inconvenient. In U.S. Patent Application 2004/0004559, Rast teaches a hair cutter with some features similar to Natrasevschi. Rast also suffers from limitations on hair length and the need to make physical contact with a person&#39;s head to position his hair cutter. Rast explains how position of his hair cutter may be determined using electronic sensors, but depends on his mechanical separator sleeve (similar in some sense to Natrasevschi&#39;s stretcher tube) to determine position above the scalp. Hence, hair is always potentially mashed down, and there are clear limitations on possible styles and hair length. 
     It is also noteworthy that the hair cutting devices of Natrasevschi and Rast, like many available on the market today, operate by continuously operating their cutter heads such that any hair that contacts the cutter heads is cut once engaged. Such approaches lead to a noisy environment as the hair cutting device will normally buzz or at least hum through the course of a haircut and the continuous operation of the cutter head leads to additional wear on moving parts and unnecessary consumption of power. 
     SUMMARY 
     One aspect provides an automated hair cutting system. In one embodiment, the system includes: (1) a hair cutting device configured to engage a cutting mechanism to cut the hair on a subject and (2) a positioning structure operable to interact with the hair cutting device to determine a position of the hair cutting device relative to a reference point. 
     Another aspect provides an automated system for cutting hair on a subject. In one embodiment, the system includes: (1) a hair cutting device having a plurality of engagable blades proximate comb teeth and controlled to allow the hair to be combed through the comb teeth and cut by the engagable blades after extension of the hair and (2) a positioning structure operable to interact with the hair cutting device to determine a position of the hair cutting device. 
     Yet another aspect provides a method of employing a hair cutting device to cut hair on a subject to conform to a specified style. In one embodiment, the method includes: (1) associating a positioning structure with the subject, the associating detecting but not impeding movement of the subject, (2) sensing a position of the hair cutting device and (3) engaging a cutting mechanism of the hair cutting device if the position correlates with the specified style. 
    
    
     
       BRIEF DESCRIPTION 
       Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an illustration of one embodiment of an automated hair cutting system including a user, a positioning device, a hair cutting device and an electronic computing device; 
         FIG. 2  is an illustration of one embodiment of a hair cutting device having a straight handle and including some features suitable for use in an automated hair cutting system; 
         FIG. 3  is an illustration of another embodiment of a hair cutting device having a side handle and including some features suitable for use in an automated hair cutting system; 
         FIG. 4  is an illustration of yet another embodiment of a hair cutting device; 
         FIG. 5A  is an illustration of one embodiment of a cutter head for a hair cutting device; 
         FIG. 5B  is an illustration of another embodiment of a cutter head for a hair cutting device having an auxiliary comb; 
         FIG. 5C  is an illustration of yet another embodiment of a cutter head having a bottom comb and cutter knives actuated relative to the teeth of the bottom comb; 
         FIG. 6A  is an illustration of one embodiment of a positioning device having hinges; 
         FIG. 6B  is an alternate illustration of the embodiment of  FIG. 6A  having been folded; 
         FIG. 7A  is an illustration of one embodiment of a positioning device having tubular construction; 
         FIG. 7B  is a top view of the embodiment of  FIG. 7A  illustrating spacing of the positioning device relative to the head of the user; 
         FIG. 7C  is an alternate view of the embodiment of  FIG. 7A ; 
         FIG. 7D  is an alternate view of the embodiment of  FIG. 7A  having been folded; 
         FIG. 7E  is an illustration of another embodiment of a positioning device having tubular construction and an ear support; 
         FIG. 7F  is an illustration of yet another embodiment of a positioning device having tubular construction; 
         FIG. 8A  is an illustration of an embodiment of a positioning device having tubular construction and positioning interfaces extending above a user&#39;s head and behind the head; 
         FIG. 8B  is an alternate illustration of the embodiment of  FIG. 8A  having a hair cutting device; 
         FIG. 9  is an illustration of another embodiment of an automated hair cutting systems having sensor hubs coupled to a wall or mirror; 
         FIG. 10A  is an illustration of one embodiment of an outline of a human scalp; 
         FIG. 10B  is an illustration of another embodiment of an outline of a human scalp; 
         FIG. 10C  is an illustration of how, in one embodiment, locations of positioning interfaces on a positioning device may be determined relative to reference points on a user&#39;s head; 
         FIG. 10D  is an illustration of an X- and Y-axis and positioning interfaces on the embodiment of  FIG. 10A ; 
         FIG. 10E  is an alternate illustration of the embodiment of  FIG. 10A  having a region of thinned hair and a region of a skull irregularity; 
         FIG. 10F  is yet another alternate illustration of the embodiment of  FIG. 10A  having a table providing information specific to hair in specific regions of the scalp; 
         FIG. 11  is an illustration of one embodiment of a three dimensional model of a human head; 
         FIG. 12  is an illustration of one embodiment of a hair dye dispensing device; and 
         FIG. 13  is an illustration of one embodiment of a stylus. 
     
    
    
     DETAILED DESCRIPTION 
     Before describing various embodiments of the automated hair cutting system and method, techniques for controlling and monitoring a position of a hair cutting device will be generally described. 
     It is realized herein that the position of a hair cutting device may be monitored relative to a subject such that it cuts hair at specified locations and times yielding a desired haircut. It is further realized herein that a positioning structure may be used in monitoring the position of a hair cutting device relative to a subject and that various embodiments of a positioning structure are possible. It is further realized herein that such a positioning structure may include a positioning device having positioning interfaces that is coupled to a subject. It is further realized herein that such a positioning structure may include a camera for monitoring a subject, or for monitoring a positioning device, or for monitoring both a subject and a positioning device. It is realized herein that reference points on the subject&#39;s face may be employed to provide greater flexibility in the shape of the positioning device and the precision with which it is coupled to the subject. It is further realized herein the positioning device need only be stable relative to the subject during operation. 
     It is realized herein the positioning structure may interact with the hair cutting device to determine the position and orientation of the hair cutting device relative to the subject. It is realized herein scalp outlines and tables may be employed to provide hair cut information. Hair cut information may include: hair length per region, scalp irregularities, color, presence of thinning hair, or many other hair characteristics. It is further realized herein that an electronic computing device may be employed to carry out computations associated with control of the automated hair cutting system, interact with sensors, and to provide a user interface. It is realized herein the electronic computing device may be a computer, cell phone, computerized tablet or a variety of other devices. 
     It is realized herein a person receiving a haircut may operate the system or have another person operate it. A person operating the system cuts hair by responding to guidance from the system that may be provided through the positioning device, the hair cutting device, the electronic computing device or possibly other devices of the system. 
     It is also realized herein that the automated hair cutting system may be applied to cutting hair on the subject&#39;s scalp and face (moustache and beard hair in addition to scalp hair) and may also be applied to other fields where precise relative alignment of a tool or other device to another object provides benefit. It is realized herein medical surgery systems, drug delivery systems, robotic systems, machine tools, cutting systems, and many other systems may benefit from the teaching of the system and method. 
       FIG. 1  shows an embodiment of an automated hair cutting system  100  including a user  102 , a positioning device  108 , a hair cutting device  200 , and an electronic computing device  106 . Electronic computing device  106  may be embodied as a cell phone, tablet computer, notebook computer, desktop computer, or other computing device. Electronic computing device  106  may include a display screen, touchscreen, buttons, cursor controls, joysticks, cameras  107 , speakers, buzzers, microphones, haptics, indicator lights, software, electronic interfaces, and other elements that may allow electronic computing device  106  to interface to user  102 , positioning device  108 , and hair cutting device  200 . Cameras  107  may be used to provide useful information to other elements of automated hair cutting system  100  and additional cameras may be provided on positioning device  108 , on hair cutting device  200 , or additional stand-alone cameras or cameras mounted on other elements of some embodiments. Electronic computing device  106  may also include wired or wireless electronic interfaces to positioning device  108 , hair cutting device  200 , and possibly to elements not shown in  FIG. 1  such as the Internet, Internet servers, cloud computing elements, or other devices. No wires are shown in  FIG. 1  to avoid clutter; however, wired interfaces between electronic computing device  106 , positioning device  108 , and hair cutting device  200  may provide power and communications. Wired interfaces such as Universal Serial Bus (USB), P1394, Thunderbolt and many other wired interfaces that provide communications or power to the devices in  FIG. 1  are possible. Wireless interfaces between electronic computing device  106 , positioning device  108 , and hair cutting device  200  are also possible and may provide power or communications. Wireless interfaces such as Bluetooth, Bluetooth Low Energy, WiFi (IEEE 802.11), Zigbee, and other wireless interfaces are also possible. Electronic computing device  106 , positioning device  108 , and hair cutting device  200  may receive power over wired or wireless connections, and may also receive power from batteries that may be disposable batteries or rechargeable batteries. 
     In  FIG. 1 , positioning device  108  is secured to the face of user  102  through forehead support  118 , nose support  120 , and mouth support  122 . Certain embodiments of the automated hair cutting system  100  may not include a positioning device  108 . Such embodiments may use cameras observing user  102  or may use other embodiments of positioning structures suitable for monitoring position and/or orientation of hair cutting device  200  relative to user  102 . Forehead support  118  and nose support  120  may employ suction cups, vacuum, textured surfaces, non-slip surfaces, adhesive, tape, two-sided tape (i.e., tape having adhesive on both sides), springs, mechanical structures, or other techniques to secure positioning device  108  temporarily to the face of user  102  so that it remains substantially in place during some operations of automated hair cutting system  100 . Mouth support  122  may be embodied as a tab or other feature that may be contoured or formed to fit comfortably to the teeth of user  102  or other features of the mouth of user  102 . Mouth support  122  may be bitten on by user  102  such that it remains securely aligned to the head of user  102  during some operations of automated hair cutting system  100 . Additional embodiments of positioning device  108  may be secured to the face of user  102  through additional elements contacting the eye sockets, cheeks, temples, ears, or other features of the face of user  102 . Certain embodiments of positioning device  108  may use any combination of forehead support  118 , nose support  120 , or mouth support  122  to secure positioning device  108  to the face of user  102 . Embodiments are also possible in which positioning device  108  is secured to the shoulders, neck, arms, or other parts of the body of user  102 . However, embodiments of positioning device  108  that primarily contact the head of user  102  and maintain alignment and position substantially constant relative to the head, and consequently, the hair and scalp, are also useful. 
     Positioning device  108  as embodied in  FIG. 1  also includes positioning interfaces: a first positioning interface  110 , a second positioning interface  112 , a third positioning interface  114 , and a fourth positioning interface  116 . The positioning interfaces may transmit signals that are received by sensors on hair cutting device  200  so that the position and orientation of hair cutting device  200  may be determined relative to positioning device  108 . The signals transmitted from the positioning interfaces may be radio signals or other electromagnetic signals, acoustic sound signals, audible sound signals, ultrasonic signals, optical signals, light signals, infrared signals, or other possible signals that may be transmitted from the positioning interfaces and received by sensors on hair cutting device  200  such that distances from the positioning interfaces to sensors on hair cutting device  200  may be determined. Analysis of signal propagation time (sometimes referred to as time-of-flight analysis), analysis of signal propagation angles (as is sometimes done in radar, lidar, and sonar systems), or any other method or technique of signal analysis may be used. It is noted that in some cases, the distances determined from, for example, first positioning interface  110  to a sensor on hair cutting device  200  may be a direct line-of-sight distance, or may represent the distance of the path taken by the signal from first positioning interface  110  to the noted sensor on hair cutting device  200 . If acoustic sound signals are used, for example, they will travel around the head of user  102  and may not always provide a line-of-sight distance. Optical signals, light signals, infrared signals, and some other signals, on the other hand, would normally provide a line-of-sight distance, but suffer the disadvantage that they may be blocked by the hands, arms, hair, or head of user  102  or by other possible obstructions to the signal&#39;s path. 
     Likewise, in the embodiment of  FIG. 1 , signals may also be transmitted from transmitters on hair cutting device  200  and received by sensors located at the positioning interfaces. Since computation of the position or orientation of hair cutting device  200  relative to positioning device  108  is desired, the system and method may be served by signals propagating in either direction. Certain embodiments employ some signals transmitted from the positioning interfaces and other signals transmitted from hair cutting device  200 . Other embodiments employ a combination of signals: radio and acoustic sound, audible sound and ultrasonic, optical and light, ultrasonic and infrared, etc. 
     Some embodiments of positioning device  108  may allow the distances between some or all of the positioning interfaces to be determined electronically using signal propagation techniques or other techniques explained in this patent applications, or other techniques available in the prior art. Some embodiments of positioning device  108  may be sufficiently rigid that the distances between some or all of the positioning interfaces are known due to the construction of positioning device  108  (or they could be measured and recorded after positioning device  108  is manufactured). In any case, if the distances between positioning interfaces are known, they may be used in support of computations to determine the position and/or orientation of hair cutting device  200 . For example, in  FIG. 1 , if the distance between first positioning interface  110  and third positioning interface  114  is known, it may be used directly in position and/or orientation calculations. Hair cutting device  200  may contain multiple sensors and the distances between those sensors may be used in position and orientation calculations. 
     Additional signals may also pass between positioning device  108  and hair cutting device  200 . These additional signals may pass through the positioning interfaces to and from hair cutting device  200  or through other wired or wireless interfaces between positioning device  108  and hair cutting device  200 . These additional signals may also pass through or be coordinated by electronic computing device  106 . These additional signals may relate to timing synchronization, system control, system security, system safety, device authentication, device capability, device model numbers, or many other aspects of the operation of automated hair cutting system  100 . 
     Embodiments of automated hair cutting system  100  may employ a wide variety of signals and techniques to compute positions and orientation. These signals and techniques include: orthogonal signals, CDMA (code division multiple access), TDMA (time division multiple access), FDMA (frequency division multiple access), OFDMA (orthogonal frequency division multiple access), ultra-wide band signals, chirp signals, radar signals, sonar signals, lidar signal, and many others. Signals passing to or from the positioning interfaces from or to hair cutting device  200  may be modulated (AM, FM, PSK, FSK, MSK, QAM, or any other possible modulations may be used) or otherwise coded or configured to contain timing, synchronization, control, data, identification of multipath signal components, security codes, information to ensure proper operation, and redundancy. Signals passing to or from the positioning interfaces from or to hair cutting device  200  may include Gold codes, PN codes, M-Sequence codes, Walsh codes, Walsh-Hadamard codes, or any other coding. In certain embodiments, signals passing to or from the positioning interfaces to electronic hair cutting device  200  may include multipath components, Doppler errors due to motion, signal fades, and may at times be blocked or modified by the arms of user  102 , other people, or other objects, making it difficult to accurately determine distance from the positioning interfaces to sensors on electronic hair cutting device  200 . For such embodiments, signal processing techniques and signals may be applied that assist in dealing with multipath, Doppler errors, fading, obstructions, and other non-ideal situations. CDMA signals, for example, may benefit some embodiments regarding multipath, fades, or blocked signal paths. Additionally, signal processing algorithms such as optimal estimators, Kalman filters, and other techniques may be helpful in some embodiments to accurately determine position or orientation of hair cutting device  200 . 
     Power control techniques similar to those used in communications systems may also be employed in an automated hair cutting system  100 . Weak or redundant transmitters (such as transmitters operating in signal paths experiencing fading, or transmitters that are not needed as other transmitters are providing enough signals to substantially ensure accurate information) in positioning interfaces or hair cutting device  200  may be temporarily powered off to reduce interference and also to save power. As hair cutting device  200  may contain multiple sensors, power control signals from hair cutting device  200  to positioning device  108  to control the power levels of the positioning interfaces on positioning device  108  may be employed to provide acceptable signal power at the multiple sensors on hair cutting device  200 . 
     As some embodiments of positioning device  108  may include speakers, acoustic drivers, or other elements that may cause physical motion or vibration, such embodiments may employ techniques to reduce the effect of vibration. Vibration may be uncomfortable to users and physical motion of positioning device  108  may cause errors or loss of precision in position measurements. Positioning interfaces containing audible sound or ultrasound speakers, for example, may employ signaling that randomizes signals, such as CDMA signals or other signal processing techniques. Differential signals may be employed to cancel vibration. Certain embodiments may employ ballast on positioning device  108  to increase its mass to reduce vibration or power control signal processing schemes that minimize the drive level to the positioning interfaces. Positioning interfaces out of range, blocked by the head of user  102 , or otherwise occluded may be powered off to save power and minimize vibration. 
     Automated hair cutting system  100  may also compensate automatically for changes in environmental parameters that may affect signal propagation, and hence, give rise to positioning errors if not accounted for. For example, if ultrasound, audible sound, or other sound signals are used, the propagation speed of sound will change with temperature, air pressure, and humidity. Automated hair cutting system  100  may include temperature, air pressure, and humidity sensors so that the effect of these environmental parameters on positioning accuracy may be compensated to achieve substantially accurate results. Alternatively, positioning device  108  may be constructed so that at least two of the positioning interfaces it contains are substantially rigidly fixed apart from each other at a substantially fixed distance; and for such an embodiment, positioning device  108  may have the ability to directly measure the distance from one positioning interface to the other that is substantially rigidly fixed a known distance from it. In such a case, the distance between the substantially rigidly spaced positioning interfaces can be measured directly by signal propagation and compared to the known rigidly fixed distance. In this way, the effect of environmental parameters may be directly assessed so that appropriate compensations may be determined. Some embodiments of an automated hair cutting system  100  may provide positioning interfaces a known substantially rigidly fixed distance apart on some other structure, besides positioning device  108  as explained here, and determine compensation for environmental parameters in an otherwise similar way. 
     Positioning device  108  may be battery powered with disposable or rechargeable batteries or may be powered through a wired or wireless connection. The positioning interfaces are shown in  FIG. 1  as spheres, but may also be embodied in a wide variety of other shapes and sizes. Special shapes and/or sizes for the positioning interfaces may provide benefit in some embodiments in allowing improvement of transmitted or received signal propagation and to allow easy identification of them if computer vision systems or other image processing is used. For example, if radio signals are used, the positioning interfaces may benefit if they are sized to provide room to allow effective radio antennas to be incorporated inside them or if they are formed to directly provide antenna functions. Positioning interfaces and the circuits and elements they contain may also be configured to enhance signal propagation in specific directions of interest so that reduced power levels, enhanced signal levels, or other benefits may be obtained. It is also noted that while the embodiment of  FIG. 1  makes use of four positioning interfaces, embodiments with more or less positioning interfaces are possible. While it may seem necessary to have at least four positioning interfaces to establish a position in space, it is noted that since operation of some embodiments of automated hair cutting system  100  may be limited to determining position on and/or above a user&#39;s  102  head, embodiments may be possible that use only one or two positioning interfaces, especially if the range of hair styles is limited to simple styles or only some parts of a user&#39;s hair are to be cut (for example, if such an embodiment was intended only as a beard or moustache trimmer). Of course, additional positioning interfaces may provide benefit in more accurately and consistently determining position and orientation. As noted above regarding blocked signal paths and multipath, the incorporation of additional positioning interfaces may provide redundancy that may allow more robust system operation in the face of detrimental conditions. 
     It is also possible to use a camera  107  on electronic computing device  106  or another camera or cameras in automated hair cutting system  100  as elements of a positioning structure to determine the position and/or orientation of hair cutting device  200  relative to the head of user  102 . In such an embodiment, position and/or orientation information from such a camera or cameras may be used separately or in conjunction with positioning information from positioning device  108  for operation of automated hair cutting system  100 . Cameras, in such embodiments, may be incorporated into electronic computing device  106 , positioning device  108 , hair cutting device  200 , or into additional devices not shown in the embodiment of  FIG. 1 . Cameras incorporated in automated hair cutting system  100  may determine position and/or orientation information of the head of user  102  and/or hair cutting device  200  through observation and computational analysis of the head and/or facial features of user  102 , features of positioning device  108 , and possibly through observation of other elements such as features of a room or other features not shown in  FIG. 1 . Special features such as targets, special shapes, symbols, or other features may be incorporated to make the determination of positions and orientations easier and more reliable. For example, the incorporation of easily recognized shapes on positioning device  108  may be helpful (this will be further explained with regard to  FIG. 7E  and  FIG. 7F ). Structured light or other special illumination techniques may also be applied to benefit the determination of features, distances, and other elements that may be helpful in determining positions and orientations. It is noted that use of structured light may be used for illumination of positioning interfaces and other possible features of a positioning device  108 , or structured light may be used to directly illuminate the face or head of a user  102  so that positioning information may be determined directly from analysis of images or video of a user  102  under illumination of structured light. 
     Images and video generated from cameras incorporated into automated hair cutting system  100  may also be displayed on electronic computing device  106  or other electronic displays that may be available (but are not shown in  FIG. 1 ) to assist user  102  in positioning hair cutting device  200  beneficially so that the hair of user  102  may be successfully cut. 
     Some embodiments of positioning device  108  may further include accelerometers or gyroscopes or other sensors that allow automated hair cutting system  100  to monitor motion, orientation, or position of positioning device  108 . Such embodiments may allow automated hair cutting system  100  to pause operation if it is determined through monitoring the accelerometers or gyroscopes or other sensors that positioning device is being moved so rapidly that significant positioning errors may occur. For example, if user  102  shakes their head rapidly, positioning device  108  may bend or flex so that the positioning interfaces move relative to each other and no longer provide correct or consistent information. Rapid motion of the head of user  102  may also cause positioning device  108  to shift in position on the face of user  102 . If such conditions occur, embodiments of positioning device  108  including accelerometers and/or gyroscopes or other sensors may provide benefit in pausing operation, guiding user  102  to move more slowly and/or smoothly, and possibly in guiding user  102  to re-position positioning device  108  if it may have moved from its proper location relative to the head of user  102 . 
     The embodiment of positioning device  108  in  FIG. 1  may provide benefit in that positioning device  108  is formed primarily in the front and sides of the face of user  102 . Such a design may allow user  102  to access their head and hair with their arms and minimizes the degree to which positioning device  108  obstructs access. As will be shown subsequently, many additional embodiments of positioning devices are also possible that offer benefit for some embodiments of automated hair cutting systems  100 . It is also noted that electronic computing device  106  may be placed on a counter, a stand, or affixed to a mirror or wall in front of user  102  so that user  102  has both hands substantially free and may operate hair cutting device  200  with one hand while positioning hair, possibly with a comb or other device, with his or her other hand. Automated hair cutting system  100  may also be configured to provide audible prompts, visible signals, and respond to voice commands and signals from user  102  so that it operates substantially in a hands-free fashion. The structure of positioning device  108  may be provided using metals, tubing, plastics, wood, or other materials and the electronics, switches, buttons, batteries, antennas, microphones, speakers, and other elements needed for various embodiments may be positioned within or on the structure of positioning device  108 . 
     Hair cutting device  200  will be described later and multiple embodiments and features will be shown. In the embodiment of  FIG. 1 , hair cutting device  200  is held by user  102  or another person and is manually positioned to collect and cut the hair of user  102 . As illustrated in  FIG. 1 , hair cutting device  200  may collect a region of hair  160  and extend it so that automated hair cutting system  100  may actuate the cutter head of hair cutting device  200  at a substantially precise point of time when the region of hair  160  is at a substantially correct length. Through repeated operation of selecting and extending regions of hair so that they may be cut, user  102  or another person manually positioning hair cutting device  200  may substantially cut the hair of user  102  to create a desired hair style. It is noted with regard to  FIG. 1  that hair cutting device  200  may operate to cut the hair of user  102  responsive to signals and/or information from a positioning device  108 , from inputs from a user  102 , and possibly also from an electronic computing device  106 . With this basic understanding of hair cutting device  200 , operation of automated hair cutting system  100  may be further described. 
     Operation of automated hair cutting system  100  may embody many different sequences and approaches that may provide benefit depending on the nature of user&#39;s  102  hair and the style and hair length he or she is seeking. In order to illustrate some possible embodiments, an embodiment of operation of automated hair cutting system  100  is now explained. User  102  may first clean their hair and comb it to avoid tangles. For some individuals or hair styles, wetting hair with water, gel, or other solutions may be beneficial. Electronic computing device  106  may then be enabled and consulted for potential styles that may be applied. A camera  107  on electronic computing device  106  may collect images of user  102  and assess their present hair length and style and determine what styles and lengths are possible with user&#39;s  102  hair. User  102  may also measure their hair and input that information into electronic computing device  106 . Automated hair cutting system  100  may be used to aid or automate measurement of user&#39;s  102  hair. User  102  may also input information about the type or shape of scalp or skull they have. Electronic computing device  106  may show user  102  examples of how she might look after their haircut is complete. User  102  may also receive options for modifications or combinations of styles and may select these through electronic computing device  106 . Once user  102  determines a style and hair length using the interfaces on electronic computing device  106 , electronic computing device  106  may prompt user  102  to secure positioning device  108  to their face and turn it on. Electronic computing device  106  may then prompt user to turn on hair cutting device  200 . Electronic computing device  106  may then temporarily disable the cutting action of hair cutting device  200  and direct user  102  to touch the idle cutter head of hair cutting device  200  to reference points on the user&#39;s  102  head. Reference points may be used to determine the location of first positioning interface  110 , second positioning interface  112 , third positioning interface  114  and fourth positioning interface  116  relative to the head and hair of user  102 . These reference points may include the tops of user&#39;s ears  152 , the back of user&#39;s neck at a collar line  154 , the tops of user&#39;s eyebrows  150 , and other reference points that are of specific interest in properly fitting a given hairstyle to a user&#39;s  102  head and facial features. Other reference points might include the front or back of a user&#39;s ears, the sides of a user&#39;s  102  eye sockets, the user&#39;s  102  hair line (the point at which the user&#39;s  102  hair scalp ends and skin without thick hair begins) at various points around the user&#39;s  102  scalp, desired locations for hair parts (the common meaning of a hair part is used here, that is, where the hair is combed apart in different directions to create a line-like feature in the hair), where hair jewelry is worn, where hair dye is present, or other features of specific hair styles, and other reference points. Additional reference points may be touched by user  102  at direction from electronic computing device  106  to help electronic computing device  106  determine the size and shape of user&#39;s  102  head and determine the location of first positioning interface  110 , second positioning interface  112 , third positioning interface  114  and fourth positioning interface  116  relative to the head and hair of user  102 . It is noted that for the purpose of determining the location of positioning interfaces, use of reference points such as the tops of the user&#39;s ears  152 , the tops of the user&#39;s eyebrows  150 , and other reference points that are substantially consistent may be favored over use of reference points like the location of hair dye, hair parts, and other reference points that may vary depending on hair growth, combing, or other variable factors. Alternatively, instead of using hair cutting device  200  for mapping the reference points as noted, a stylus  1302  (an embodiment of such a stylus  1302  is shown in  FIG. 13 ), different hair cutting device, or other reference device may be used to provide reference point positions. Reference points may be established through a user touching a hair cutting device  200 , stylus  1302 , or other suitable device to the predefined reference point on their head or face and acknowledging (through a button press, audible sound, or other suitable signal—or alternatively, automated hair cutting system  100  may observe the user and determine from computer vision analysis when a reference point has been touched) to automated hair cutting system  100  that the reference point is being touched. The use of reference points allows precise information regarding the location of a specific region of hair on user  102  to be determined relative to reference point features of user  102  without the need for positioning device  108  to be precisely positioned relative to the face of user  102  (positioning device  108  need only be stable relative to the face of user  102  through the course of a haircut). Consequently, embodiments of automated hair cutting system  100  including the use of reference points as described, may provide convenience to people using them (since positioning device  108  need not be precisely aligned to their face, but only needs to be stable for the duration of a haircut) and also allow for a wide range of shapes, sizes, and other configurations of positioning device  108 . With the information of the reference points determined, electronic computing device  106  may then map the chosen hair style to specific locations on the head of user  102  so that the hair length needed to create the chosen hair style is now defined based on location on user&#39;s  102  head. Electronic computing device  106  may now direct user  102  to engage hair cutting device  200  to specific locations on user&#39;s  102  head, to engage the cutter head of hair cutting device  200  into user&#39;s  102  hair, and to pull hair cutting device  200  substantially away from user&#39;s  102  head so that hair is extended from the specific location. 
     Alternatively, electronic computing device  106  may allow user  102  to select any location on their scalp to begin, measure that position, and determine the length of hair needed specific to that location for subsequent cutting. While user  102  extends their hair for cutting, positioning device  108  may continue to monitor the position and orientation of hair cutting device  200  to ensure that user  102  is extending their hair sufficiently so that accurate cutting may take place. In the event that user  102  is not suitably extending the hair in the cutter head of hair cutting device properly, automated hair cutting system  100  may perform computations to correct for errors that would otherwise occur, or automated hair cutting system  100  may alert user  102  to try again. As user  102  extends their hair engaged in hair cutting device  200 , electronic computing device  106  may monitor the distance of the cutter head  202  of hair cutting device  200  from the head of user  102  and enable cutting action when the hair of user  102  specific to that location is at a substantially correct length for a specific chosen hair style and length that was previously selected so that hair in the cutter head  202  of hair cutting device  200  is cut substantially to a correct length. Once the hair specific to that location has been cut, electronic computing device  106  again disables cutting action of hair cutting device  200  and directs user  102  to engage hair in another location. Through repeated selection, engagement, extension, and cutting of hair, user&#39;s  102  hair is cut to fit the chosen style and length. It is noted that electronic computing device  106  may also direct user  102  to roll their head and use their free hand (the one not being used to hold hair cutting device  200 ) to most conveniently keep loose hair away from the cutting operation and avoid inadvertently cutting hair that should be kept longer for the desired style and hair length. Since positioning device  108  is affixed to the face of user  108 , a key benefit of the system and method is that user  102  is free to move their head in the course of a haircut without compromising positioning or orientation information of hair cutting device  200  relative to positioning device  108 . 
     The process of repeated selection, engagement, extension, and cutting of hair, as described above, offers benefit that hair cutting device  200  need not continuously operate its cutter head. That is, the cutter head may be kept idle during the selection, engagement, and extension of hair and the cutter head need only be actuated to cut hair at times when the position of hair cutting device  200  is beneficial for cutting specific hair at substantially desired lengths. The ability to only operate the cutter head of hair cutting device  200  at times when hair cutting device  200  is properly positioned to cut specific hair allows energy consumption, noise levels, and cutter head wear to all be reduced. 
     It is very common for hair cutting professionals to measure hair length with their fingers or using a comb or scissors handle as a reference. As a hair cutting professional works across the head of a person, they alter the length of cut to create the style they plan to achieve. Automated hair cutting system  100  works in a way very similar to how human barbers have cut hair for a very long time. It is also possible for automated hair cutting system  100  to operate in different ways. For example, if a user  102  is shaving the back of their neck with hair cutting device  200 , automated hair cutting system  100  may prompt them on how to position hair cutting device  200  and what direction to move it. From there, automated hair cutting system  100  may enable the cutter head of hair cutting device  200  as user  102  properly moves hair cutting device  200  and may disable the cutter head of hair cutting device  200  if user  102  moves it incorrectly. In this way, automated hair cutting system  100  ensures that user  102  cuts their hair properly while allowing hair cutting device  200  to be moved smoothly across the back of their neck or other regions of their scalp where a shaving or other hair cutting technique benefits from smooth motion of hair cutting device  200 . Still other modes of operation of automated hair cutting system  100  are possible. As an additional example, consider the well-known “flat top” men&#39;s hair style. In this style, hair across the top of a man&#39;s head is cut to be as flat as possible, without regard to the specific length of hair for each specific region of the man&#39;s scalp. For such a hair style, automated hair cutting system  100  may actuate the cutter head of hair cutting device  200  to cut hair when it has been collected and extended to the right point to substantially create a flat top instead of with regard to the precise length of hair for each scalp region. 
     Since hair cutting device  200  has a cutter head of a significant width, it is possible for hair cutting device  200  to have hair in the cutter head that should be cut at different lengths for any given operation (the operation as noted above of selecting a location, engaging some hair, extending the hair, and cutting it to a substantially correct length). In such cases, electronic computing device  106  may direct hair cutting device  200  to cut the hair in the cutter head only when all hair in the cutter head has been extended so that it is all at either a correct length for cutting or at a longer than needed length. In this way, additional cycles of selecting, engaging, extending, and cutting may be used to further reduce the length of hair that was previously cut longer than desired, but no hair is substantially ever cut too short. This form of operation is important especially for locations on the head of a user  102  where the surface of the user&#39;s  102  scalp curves rapidly, or for hair styles in which hair length changes rapidly from one location to another. In  FIG. 5C , an embodiment of a cutter head capable of cutting subsets of hair contained in it at different times is shown. Such a cutter head allows embodiments of automated hair cutting system  100  to cut specific hair collected in hair cutting device  200  at specific times, providing benefit in dealing with the situation as described in this paragraph. It is also possible for automated hair cutting system  100  to provide additional guidance or instructions to user  102  to control hair cutting device  200  so that most of the hair contained in cutter head of hair cutting device  200  for a specific operation may be suitably cut at the same time to the length needed. In this way, a user  102  who may operate automated hair cutting system  100  more skillfully may be able to produce an accurate haircut in fewer operations than a user  102  who uses automated hair cutting system  100  substantially without such additional guidance or instructions or who disregards such additional guidance or instructions. 
     Once user  102  has completed cutting their hair in the fashion described and possibly combed it to exhibit the desired style, a camera on electronic computing device  106  or other camera may be used to collect images of user&#39;s  102  hair. These may be shown to user  102  and user  102  may direct electronic computing device  106  that they desire some modification to their hair. For example, user  102  may desire slightly shorter hair above their eyebrows (shorter bangs), a slightly higher collar line in back, or other features. Once user  102  has selected modifications, electronic computing device  106  may again direct user  102  to cut their hair in a manner similar to that previously described to achieve the desired effect. A camera on electronic computing device  106  or other camera may also monitor user  102  through the course of their haircut to ensure that user  102  is operating automated hair cutting system  100  properly and is achieving acceptable results. In such a case, electronic computing device  106  may process images from such a camera or cameras and determine if user  102  should be provided with additional guidance as they cut their hair. 
     Before the hair cutting process is completed, electronic computing device  106  may ask user  102  if they would like to store some or all of the information about the size and shape of their head, reference point information regarding the location of their ears, eyebrows, etc., their preferred styles, the specific style they chose for this just-completed haircut and perhaps the modifications to that style that were ultimately selected, or other information. If user  102  so desires, this and other information may be stored for future use either directly in electronic computing device  106 , or possibly in a network server, cloud computing element, or other device or computing element. 
     It is noted that each time a user  102  makes use of automated hair cutting system  100 , positioning device  108  may be positioned to a slightly different position on their face. Additionally, positioning device  108  may be of a slightly different shape if it was folded (see the embodiments of  FIG. 6B  and  FIG. 7D  for reference) for storage or was slightly deformed, bent, or modified since its prior use. In such cases, automated hair cutting system  100  may need to ask user  102  to re-enter the reference point information noted above so that it may properly fit a desired hair style to the head of user  102 . Also, prior to cutting features in a user&#39;s  102  hair that demand very precise alignment, such as cutting around the ears or ensuring a feature is precisely aligned to a part of a user&#39;s  102  face, automated hair cutting system  100  may prompt user  102  to touch and reestablish some reference points specific to the operation about to be undertaken, ensuring substantially precise alignment. In some cases and with some embodiments, if automated hair cutting device  100  has stored information regarding reference points, the size and shape of a user&#39;s head, and possibly other information for user  102  from prior use of automated hair cutting system  100 , automated hair cutting system  100  may be able to account for changes in precise positioning and shape of positioning device  108  with fewer reference points entered than may otherwise be required. 
     The display function and computational functions of electronic computing device  106  may be embodied into positioning device  108  or even into hair cutting device  200 . Alternate embodiments of automated hair cutting system  100  may also include electronic displays, touchscreens, keyboards, or similar human interface functions. In certain embodiments, instructions, queues, information, and directions to the user  102  from electronic computing device  106  (or as noted other devices in the system whether electronic computing device  106  is present or not) may be delivered visually on electronic displays, with audible signals, with indicator lights, with haptic signaling, or through other techniques. 
     In other embodiments, a robotic arm under automated control could either grip hair cutting device  200  or be otherwise fitted with a cutter head so that it may directly cut the hair of user  102 . Further robotic arms could also be applied to comb hair or position it for cutting. In such a fashion, a robotic system could provide automated hair cutting services. 
     In alternate embodiments automated hair cutting system  100  may have multiple modes of operation and may provide different commands, guidance or information depending on whether user  102  is using automated hair cutting system  100  to cut their own hair, if another person is using automated hair cutting system  100  to cut a user&#39;s  102  hair, or whether automated hair cutting system includes other elements such as Internet access (which would allow additional modes of operation, instructions, etc. to be downloaded). The information provided by automated hair cutting system  100  in the course of a haircut may also be varied depending on the skill level of the person operating it and the type of haircut being provided. For example, novice users of automated hair cutting system  100  may desire more complete guidance especially if they are attempting a complex or challenging hair style. 
     Those skilled in the art will recognize that the teachings of the system and method may be applied to create robotic or otherwise automated systems for a wide variety of uses where a wide variety of tools (such as cutting devices, grinders, polishers, material dispensing devices, imagers, video cameras, and other possible tools) may be beneficially tracked or monitored relative to another structure, such as a positioning device, so that those tools may be applied to objects with known position and/or orientation relative to such a structure to achieve desired results. A key benefit of the system and method is the ability to accommodate changes in such objects so that they do not need to be substantially identical (as is normally the case for many modern manufacturing or other such systems). As an example, such an automated system may allow a person holding a device or tool to substantially precisely locate it by hand for the application of makeup, hair dye, hair tints, hair highlights, cosmetic surgery, and many other possible functions. And those skilled in the art will further recognize that the teachings of the system and method may be applied to fabrication of mechanical devices, formation of sculpture, fabrication of physical models with modeling clay or other materials, operations such as cutting, grinding, ablating, polishing, clamping, hammering, puncturing, drilling, mixing, painting, coating, imaging, illuminating, robotic micro-surgery, eye surgery, drug delivery, dental work, dental surgery, cutting tools, machine tools, and in wide variety of other applications. 
       FIG. 2  is an illustration of an embodiment of hair cutting device  200  including handle  206 , body  204 , cutter head  202 , sensors  208 , accelerometer  210 , indicator lights  212 , recessed region  214 , camera  216  and illumination source  218 . Body  204  and handle  206  may contain operation and control electronics, batteries, power electronics, a motor to drive cutter head  202 , and other functions. Cutter head  202  may be typical of hair cutter heads found on commonly available hair clippers, trimmers, shavers, or other devices, or may be of special construction for beneficial use in an automated hair cutting system  100 . Cutter head  202  may be configured so that it is removable from hair cutting device  200  for cleaning or replacement. Certain embodiments may employ interchangeable cutter heads such that one cutter head may be designed to cut longer hair and it could be interchanged with a trimming cutter head that could be used for detailed trimming, shaving or other functions. Indicator lights  212  may be of various colors, sizes, and locations and may be visible to user  102  in the course of a haircut especially if viewed into a mirror in front of user  102  in the course of a haircut. Indicator lights may help to signal a user on how best to orient, position, and move hair cutting device  200  for substantially better or faster results. Hair cutting device  200  may also contain audible speakers, buzzers, bells, chimes, haptic devices, displays, and other devices to help guide, signal, or provide information to user  102 . Indicator lights  212  and audible speakers, buzzers, bells, chimes, haptic devices, displays, and other devices to help guide, signal, or provide information to user  102  on hair cutting device  200  may operate in conjunction with information that user  102  may receive from electronic computing device  106  or from positioning device  108 . 
     Accelerometer  210  may be monitored by hair cutting device  200  to determine its position and orientation and to ensure that it has not been suddenly jerked or rapidly moved before cutter head  202  is enabled to cut the hair it contains. In this way, hair may not be incorrectly cut if sudden user  102  motions exceed the ability of automated hair cutting system  100  to sufficiently determine position and orientation. Hair cutting device  200  may also contain a gyroscope or other position or orientation monitoring sensors and electronics to ensure hair is only cut when it should be and to determine the position and orientation of hair cutting device  200 . Accelerometer  210  is shown on the surface of hair cutting device  200  for clarity, but accelerometer  210 , gyroscopes, and other possible sensors may be contained inside body  204  and may not be visible on the outside of hair cutting device  200 . 
     The embodiment of hair cutting device  200  shown in  FIG. 2  includes three sensors  208  that are operable, as shown in  FIG. 1 , with the first positioning interface  110 , second positioning interface  112 , third positioning interface  114 , and fourth positioning interface  116  to determine the position and orientation of hair cutting device  200  relative to positioning device  108  as already described. These three sensors  208  as embodied in  FIG. 2  are shown at the end of handle  206  and in body  204  near each end of cutter head  202 . Such placement of sensors  208  as far from each other as reasonably possible on hair cutting device  200  may be beneficial in providing accurate information about the precise location and orientation of hair cutting device  200 . Alternate embodiments may employ alternative placement of sensors  208 , for example, placing sensors  208  to avoid obstruction by arms or hands of a user  102  or other people. Other embodiments may place sensors  208  in still other locations and may even place sensors  208  on posts, supports, or other features that adjoin body  204 , handle  206 , or other elements of hair cutting device  200  and allow sensors  208  to be located beneficially. Having accurate information regarding the orientation of hair cutting device  200  and the location of sensors  208 , an accurate determination of the position of cutter head  202  is possible. 
     Depending on the types of signals used for first positioning interface  110 , second positioning interface  112 , third positioning interface  114 , and fourth positioning interface  116  shown in  FIG. 1 , sensors  208  may include antennas, microphones, light sensors, infrared sensors, or other types of sensors. Certain embodiments may use transmitters in place of sensors  208  on hair cutting device  200  and sensors on positioning device  108  with similar effect and with signals simply propagating from hair cutting device  200  to positioning device  108  instead of in the other direction. While three sensors  208  are shown in the embodiment of  FIG. 2 , any number of sensors  208  may be applied in various embodiments. A single sensor  208 , for example, may be used in conjunction with accelerometer  210  and possibly with additional gyroscopes or other sensors to achieve good results. And embodiments with two, three, four, or more sensors  208  may provide benefit in offering robust results and accurate positioning and orientation information potentially in the face of blocked signals, multipath or other detrimental aspects of signal interfaces as described above. 
     Some embodiments of hair cutting device  200  may include a recessed region  214 , as shown in  FIG. 2 , containing a camera  216  and possibly also an illumination source  218 . Alternative embodiments may include other physical features to house camera  216  or illumination source  218  such as additional housings or fittings. In certain embodiments employing a recessed camera  216  or illumination source  218 , the surface of hair cutting device  200  is kept substantially free of obstructions. Camera  216  may be employed to observe features of the head, face, and hair of a user including reference points that may especially be used to determine locations on a user&#39;s scalp or face, to observe features of a positioning device, or to observe other things of benefit in the operation of automated hair cutting system  100 . An illumination source  218 , may provide illumination to augment operation of camera  216  and may also provide colored light or structured light to augment the ability of automated hair cutting system  100  to analyze images provided by camera  216 . Structured light is a well-known concept and will not be discussed in detail here. For purposes of this disclosure, “structured light” is defined as one or more beams of light (incoherent or coherent) that are shaped or arranged relative to one another to form a defined pattern (such as a grid, lines, dots or geometric primitives) and projected so as to illuminate one or more objects to allow distances to specific points on the one or more objects to be ascertained by analyzing images of the one or more objects taken (typically by one or more cameras) under the illumination of the predefined pattern of light. Embodiments of hair cutting device  200  that contain multiple cameras  216 , and/or multiple illumination sources  218 , and/or multiple sources of structured light, are possible. 
     Hair cutting device  200  may also include a manual operation mode in which its position is not tracked, but in which it operates as a conventional hair cutter or trimmer such as those commonly available prior to the teaching herein. Such a manual operation mode may be entered through actuation of a switch, button, voice command, or any other type of control. When operating in such a manual operation mode, hair cutting device  200  may continuously actuate cutter head  202  or cutter head  202  may be actuated when a button is pressed, a voice command is given, or through any other type of control. 
       FIG. 3  shows an additional embodiment of a hair cutting device. In  FIG. 3 , a hair cutting device with side handle  300  is shown. Hair cutting device with side handle  300  includes sensors  208 , indicator lights  212 , accelerometer  210 , and cutter head  202  that all perform functions substantially equivalent to those described for hair cutting device  200  already described. Hair cutting device with side handle  300  also includes a side handle  306  and body  304  that are shaped in a way that some people may find beneficial or more comfortable for cutting hair. The embodiment of hair cutting device with side handle  300  in  FIG. 3  is shown primarily to call attention to the ability to incorporate the system and method into a very wide variety of shapes and styles of hair cutting devices. In addition to the embodiments of hair cutting device  200  and hair cutting device with side handle  300 , the system and method may be applied to a very wide variety of hair cutters, clippers, trimmers, shavers, and other devices and may also be applied to devices that shave or trim beards, eyebrows, facial hair, and other hair in addition to hair on a user&#39;s  102  scalp as shown in  FIG. 1 . 
     In addition to the straight handle  206  of hair cutting device  200  and side handle  306  of hair cutting device with side handle  300 , many other embodiments of handles, knobs, levers, supports, and other possible structures may be used so that a person may position a hair cutting device. Handles including pivots so they may be rotated, hinges so they may be tilted, flexible members, telescoping members, adjustable features, rubber grips (or grips made from other materials), contours, or any other enhancements may be applied to embodiments of handles for hair cutting devices. 
     Hair cutting device with side handle  300  as shown in  FIG. 3  may also include touch sensor  308  on the portion of body  304  that may contact user&#39;s  102  scalp when hair cutting device with side handle  300  is operated. Touch sensor  308  may be a simple switch, electronic touch sensor, or other contact sensor that signals to hair cutting device with side handle  300  that it has contacted user&#39;s  102  scalp, so that hair cutting device with side handle  300  may determine and record its position and orientation. In this way, hair cutting device with side handle  300  may substantially precisely determine the location of user&#39;s  102  scalp and compare that on an ongoing basis to where computation from previously determined reference points as described with regard to  FIG. 1  indicated user&#39;s  102  scalp is expected to be. In this way, automated hair cutting system  100  may monitor its operation and determine if it is sufficiently accurately determining position and orientation of hair cutting device with side handle  300 . If user  102 , for example, inadvertently bumps, moves, or otherwise disturbs positioning device  108  so that the relative position of positioning device  108  is changed with regard to user&#39;s  102  hair, hair cutting device with side handle  300  may detect this as described, stop cutting hair, and request the user  102  to reestablish reference points so that automated hair cutting system  100  may ensure accurate hair cutting. Of course, minor errors in scalp position determined when touch sensor  308  signals that it has contacted user&#39;s  102  scalp may be ignored or used to calibrate or otherwise improve automated hair cutting system&#39;s  100  estimates of the shape and size of user&#39;s  102  scalp. Only one touch sensor  308  is shown in the embodiment of  FIG. 3 , but two or more are possible and they may be positioned along the length of body  304  near cutter head  202  for beneficial effect, or in other beneficial locations. Embodiments where no touch sensor  308  is employed but where accelerometer  210  or positioning information determined from sensors  208  are monitored to determine when user&#39;s  102  scalp has been contacted are also possible. 
     In certain embodiments of automated hair cutting systems  100 , touch sensor  308  includes radar, sonar, or other electronic or electro-mechanical system to determine the distance from the bottom surface of cutter head  202  to the scalp of user  102 . The distance from the bottom surface of cutter head  202  to the scalp of user  102  may be employed in some embodiments to determine the location or orientation of hair cutting device with side handle  300  and may also be employed to determine when cutter head  202  should be activated to cut hair it contains. Use of a touch sensor  308  is not limited to a hair cutting device with side handle  300 , but may be applied to hair cutting device  200 , or other possible embodiments of hair cutting devices. 
       FIG. 4  is an illustration of an embodiment of a manually driven hair cutter  400  that includes sensors  208 , accelerometer  210 , indicator lights  212 , and cutter head  202  that perform similar functions to those of hair cutting device  200 . Manually driven hair cutter  400  also includes fixed handle  402 , pivot  408 , body  404 , and movable handle  406 . Fixed handle  402  and movable handle  406  are similar to handles on a pair of scissors, and motion from moving the moveable handle  406  could be transferred to cutter head  202  to actuate cutter head  202  and cut hair it may contain. Since some embodiments of the system and method involve cutting hair at substantially precise times so that hair is cut to substantially precise lengths, it is also possible to store energy from motion of movable handle  406  in a spring or other energy storage device and to release that energy through electronic controls to actuate cutter head  202  at substantially precise points in time. In this way, moveable handle  406  may cock a spring or other mechanism or device and the associated energy may be released under control from electronics inside manually driven hair cutter  400  or from signals received from electronic computing device  106 , positioning device  108 , or from other elements that may be present in some embodiments. It is noted that while moveable handle  406  may be used to provide some of the energy needed to operate manually driven hair cutter  400 , that manually driven hair cutter  400  may also receive energy from wired connections, batteries, or other or combinations of energy supplying or energy storage elements. One possible embodiment would be for the cutter head  202  on manually driven hair cutter  400  to be driven with energy from motion of moveable handle  406  and for other elements of manually driven hair cutter  400  to be powered from batteries or a wired or wireless power connection. 
     In addition to storing energy from motion of moveable handle  406  in a cocked spring or other element, it is also possible for moveable handle  406  to directly actuate cutter head  202  so that cutter head  202  cuts the hair in it directly when handle  406  is moved (much as a scissors cuts items in its blades when the handles are moved). In such an embodiment, the user  102  may be signaled by automated hair cutting system  100  as to when moveable handle  406  should be moved. Such a signal may be audible, haptic, visual, or through other techniques. Several alternative embodiments for a manually driven hair cutter  400  are possible including a very wide variety of handles, levers, knobs, etc. for how a user may manually drive a hair cutter. 
       FIG. 5A  shows a cutter head  500  that may be employed for cutter head  202  shown in  FIGS. 2-4 . Front edge of cutter head  502  is formed from cutter head comb teeth  504 , and cutter head  500  operates when blade  506  is actuated back and forth through the openings shown in cutter head comb teeth  504 . Blade  506  may be actuated with a linear actuator, rotary motor, piezo motor, magnetic motor, or other types of motors or actuators. When blade  506  actuates back and forth any hair sufficiently inside cutter head comb teeth  504  that it contacts blade  506  may be cut. Cutter heads formed from adjoining cutting blades that move back and forth, rotary cutters, laser cutting devices, and other types of cutters may be adapted to work with the system and method. Cutter head  500  may be employed such that contact with a person&#39;s hands, a comb, or with other tools for positioning hair does not cause injury or damage. Spacing of comb teeth  504  and other possible design considerations may be taken into account in providing a substantially safe design for cutter head  500  that substantially avoids injury or damage if inadvertent contact is made with it. 
       FIG. 5B  shows a cutter head having an auxiliary comb  550 . Cutter head with auxiliary comb  550  includes front edge of cutter head  502 , cutter head comb teeth  504 , and blade  506 . These elements perform the same functions as the cutter head  500  shown in  FIG. 5A . Cutter head with auxiliary comb  550  also includes auxiliary comb teeth  552  that may be spaced over and above cutter head comb teeth  504  so that auxiliary comb teeth  552  also engage and substantially contact hair collected in cutter head with auxiliary comb  550 . Some embodiments of the system and method may employ auxiliary comb teeth  552  to provide additional friction making it easier to control hair in cutter head with auxiliary comb  550  versus other possible types of cutter heads. A user  102 , for example, that has curly hair or other types of hair may find that their hair springs free from the cutter head before it can be cut unless auxiliary comb teeth  552  or some other means is used to provide additional friction. Auxiliary comb teeth  552  may be formed from plastics, metals, or other materials and may be textured, serrated, coated, or otherwise finished so that they provide a desirable level of friction to hair collected in cutter head with auxiliary comb  550 . In addition, auxiliary comb teeth  552  may be fixed in place above cutter head comb teeth  504 , or may be actuated and may serve to grab or latch hair into cutter head with auxiliary comb  550 . If auxiliary comb teeth  552  are actuated, they may move together or individually in response to electrical or mechanical mechanisms and may move sideways, up and down, or in other directions. Embodiments in which auxiliary comb teeth  552  may be adjusted to achieve a desired level of friction, interchanged with other embodiments of auxiliary comb teeth to adjust friction, or retracted or removed if no additional friction is desired are also possible. It is also possible that cutter head teeth  504  be specially formed, coated, textured, serrated, or otherwise finished so that they also provide the function of providing sufficient friction for convenient control of hair. Embodiments in which cutter head teeth  504  may be specially formed, coated, textured, serrated, or otherwise finished to provide sufficient friction may be applied whether or not auxiliary comb teeth  552  are present in those embodiments. 
     The embodiment of cutter head with auxiliary comb  550  shown in  FIG. 5B  may also offer benefit in gripping hair after it has been cut so that it may be moved to a place suitable for disposal and released. If auxiliary comb teeth  552  are actuated under control from a user  102 , under automatic electronic control, or through another control method, some embodiments may allow user  102  to manually (or through voice commands, etc.) signal when to release auxiliary comb teeth  552  so that cut hair is released. Alternative embodiments of hair cutting devices such as hair cutting device  200  shown in  FIG. 2  may include the ability to connect a vacuum such that cut hair may be suctioned away. Other embodiments contain features to allow cut hair to be temporarily stored (possibly after grinding it for more compact storage) before it is discarded. 
       FIG. 5C  shows an embodiment of a cutter head with bottom comb  560 . Bottom teeth  562  are spaced to allow hair to enter and to be combed in a conventional way (that is, like a common comb is used). Cutter knives  564  are positioned on top of bottom teeth  562  so that they do not interfere with the function of the bottom comb, allowing regions of hair to be engaged and extended. Cutter knives  564  may then be actuated so that they slide over the regions between bottom teeth  562  and cut hair that may be present. Cutter knives  564  may be actuated together as a single element, or some embodiments may allow them to be actuated in groups or to be actuated individually. If cutter knives  564  can be actuated in groups or individually, it is possible for automated hair cutting system  100  to actuate them so that the hair collected between individual bottom teeth  562  is optimally cut, potentially providing improved accuracy versus a cutter head that cuts all the hair collected in it at once. Cutter knives  564  are not shown present on top of end bottom teeth  566 , but some embodiments may include them. Putting cutter knives  564  on top of end bottom teeth  566  may not be necessary as cutter knives  564  above adjacent bottom teeth  562  may cut the hair collected near them. It is also possible to eliminate cutter knives  564  from alternate bottom teeth  562  across the entire cutter head with bottom comb  560  if the cutter knives  564  present can actuate in both directions and cut hair in both the adjacent gaps between bottom teeth  562  they adjoin. 
       FIG. 6A  shows an embodiment of a foldable positioning device  600 . Foldable positioning device  600  operates similarly to the embodiment of positioning device  108  shown in  FIG. 1  and includes a forehead support  610 , a nose support  618 , connecting members  608 , and four positioning interfaces  616 . Foldable positioning device  600  also includes two body housings  612  and four hinges  614 . Foldable positioning device  600  is shown affixed to the face of a user  602 . Communications and control electronics, batteries, buttons, speakers, microphones, wireless interfaces, wired interfaces, and other functions may be incorporated in body housings  612 . Hinges  614  allow foldable positioning device  600  to be folded so that it can be compactly stored or transported. Foldable positioning device may be fabricated from metals, plastics, woods, other suitable materials and combinations of materials. 
       FIG. 6B  shows foldable positioning device  600  from  FIG. 6A  after it has been folded at hinges  614  for compact storage. It is noted that in addition to hinges  614  as shown, foldable positioning device  600  may include flexible members, telescoping shafts, and other elements to allow it to be compactly folded. In addition to folding for storage, a positioning device  108  or foldable positioning device  600  may include elements allowing it to be adjusted to fit a range of faces of different possible users. For example, one embodiment of a positioning device  108  or foldable positioning device  600  allows adjustment to properly fit a small face of a child and also a relatively large face of an adult. A positioning device  108  or foldable positioning device  600  may also be configured for specific hair styles (i.e., such that positioning device  108  or foldable positioning device  600  provides sufficient positioning information for a specific hair style and having less weight, material, space, or is more convenient or cost effective, or provides other additional benefits than it would if it were intended for other hair styles). 
       FIG. 7A  is an illustration of an embodiment of a positioning device with tubular construction  700 . Ear supports  714  and a head band  708  support a main tube  704  of positioning device with tubular construction  700  around the face and head of user  702 . Band connectors  706  may allow head band  708  to be adjusted in length and in position along main tube  704 . Main tube  704  supports positioning interfaces  712  that may operate and function in a fashion similar to those shown in  FIG. 1 . The embodiment of  FIG. 7A  has six positioning interfaces  712  visible and a seventh positioning interface blocked from view by the neck of user  702  (end positioning interfaces  710  are also considered positioning interfaces  712  for this count, indeed, end positioning interfaces  710  are only separately numbered to call attention to their specific location). Additional embodiments of positioning device with tubular construction  700  may support larger or smaller numbers of positioning interfaces  712 . While positioning interfaces  712  in  FIG. 7A  are shown as enlarged regions of main tube  704 , some embodiments may make use of a main tube  704  large enough that positioning interfaces  712  are fully contained inside it and are not externally visible. In such embodiments, main tube  704  may appear to be smooth and may not show external features where positioning interfaces  712  are present. Ear supports  714  and head band  708  may be adjustable in position along main tube  704 , in length, in orientation relative to main tube  704 , and in other aspects. Hinges  716  are shown that allow main tube  704  to be folded for storage (this will be explained further with regard to  FIG. 7D ). Certain embodiments may employ hinges, flexible tubing, telescoping tubing, adjustable screws, springs, elastic materials, fasteners, and other techniques to allow positioning device with tubular construction  700  to be folded or otherwise made compact for storage or adjusted to better fit user  702 . End positioning interface  710  and end housing  718  are shown at one end of main tube  704  and a similar end positioning interface and end housing on the other end of main tube  704  are blocked from view by the neck of user  702 . End housing  718  and main tube  704  may contain batteries, electronics, computing devices, signal processing devices, and other functions to enable operation of positioning device with tubular construction  700  as a positioning device as described with regard to positioning device  108  of  FIG. 1  and other embodiments shown in this patent application. Positioning device with tubular construction  704  may receive power and interface signals from batteries and/or wired or wireless interfaces. End housing  718  may allow some of the heavier elements of positioning interface with tubular construction  700  to be positioned below and behind the ears of user  702  so that they provide balance to positioning interface with tubular construction  700  and provide leverage from ear supports  714  to help keep head band  708  in place against the forehead of user  702 . The embodiment of end housing  718  shown in  FIG. 7A  is shown as a conical structure, but many other shapes and sizes are possible including cubic structures and cylindrical structures. Some embodiments of positioning device with tubular construction  704  may lack end housings  718  as their electronics and other needed elements may be contained entirely inside main tube  704  or in other areas inside or upon positioning device with tubular construction  700 . 
     Positioning device with tubular construction  700  has regions of narrow tubing  705  in which main tube  704  is substantially reduced in diameter. Certain embodiments may employ regions of narrow tubing  705  to allow hair cutting devices to be more easily applied and operated in regions of the face and head of user  702 . In  FIG. 7A , regions of narrow tubing  705  are shown in areas where positioning device with tubular construction  700  passes in front of the ears of user  702 . Other embodiments may employ regions of narrow tubing  705  to allow more precise trimming of sideburns and other features of haircuts just above and in front of the ears of a user  702 . Certain embodiments may also include regions of narrow tubing or other features to allow improved convenience in or on other parts of positioning device with tubular construction  700 . 
     Positioning device with tubular construction  700  as embodied in  FIG. 7A  may be employed to provide a simple and attractive design that is easy to store, clean, and maintain. Positioning device with tubular construction  704  may be constructed from plastics, metals, wood, ceramics, rubber or other materials and may be constructed to be easy to clean and may employ materials that resist the formation of bacteria and germs. Positioning device with tubular construction  700  may be designed to be submersible in water so that it may be easily rinsed clean. 
     Certain embodiments of positioning device with tubular construction  700  employ an enlarged open region in front of the eyes of user  702  so that user  702  may wear eyeglasses while operating automated hair cutting system  100 . While eyeglasses may interfere with cutting hair on some parts of the head of a user  702 , some users may prefer to cut some or most of their hair with their eyeglasses on and only remove their eyeglasses to cut those portions of their hair obstructed by their eyeglasses. Alternate embodiments employ a positioning device that allows a user  702  to wear their eyeglasses and also to remove and replace their eyeglasses without disrupting operation of the positioning device. While certain embodiments of positioning devices may be configured to allow operation with eyeglasses in place, positioning device with tubular construction  700 , as shown embodied in  FIG. 7A , allow for easier access because of the large opening it provides in front of the eyes of user  702 . 
     Main tube  704  and regions of narrow tubing  705  may be composed of flexible materials that may be bent and formed such that positioning device with tubular construction  700  may be properly and comfortably fit to the head of user  702 . Alternatively, main tube  704  and regions of narrow tubing  705  may be composed of rigid or semi-rigid materials and may be formed to include smooth curves. Main tube  704  and regions of narrow tubing  705  may also be composed of materials that provide tension or spring function so that positioning device with tubular construction  700  applies an acceptable level of compression against the face of user  702  through ear supports  714  and head band  708  so that they more easily grip the face of user  702 . Ear supports  714  and head band  708  may employ coatings, adhesives, paste, tape, texturing, or other techniques to improve their grip to the face of user  702  or improve comfort. Ear supports  714  may also be coated, textured, or otherwise finished so that eyeglasses resting over the top of ear supports  714  may more easily grip ear supports  714 . Main tube  704  and regions of narrow tubing  705  may have a circular, square, triangular, hexagonal, or other cross-section. Normally, main tube  704  and regions of narrow tubing  705  will include a hollow center so that wiring, circuitry, electronics, and other elements may be formed or placed inside them. However, embodiments in which main tube  704  and regions of narrow tubing  705  have solid cross-sections without a hollow center are also possible. 
       FIG. 7B  shows a top view of an embodiment of a positioning device with tubular construction  700 . Ear supports  714 , end housings  718 , end positioning interfaces  710 , positioning interfaces  712 , and main tube  704  are shown around the head of user  702 . The end of the nose  703  of user  702  is also shown in  FIG. 7B  to avoid any possible confusion regarding the orientation of this top view of user  702 . Distance  711  from head  702  to main tube  704  in  FIG. 7B  is shown to call attention that keeping a gap between the main tube  704  of positioning device with tubular construction  700  and the head of user  702  provides a substantially less obstructed path between positioning interfaces  712  and sensors  208  on hair cutting device  200  (or other embodiments of hair cutting devices) than may be possible if main tube  704  were in close proximity to the head of user  702 . Maintaining a distance  711  from head  702  to main tube  704  may also be beneficial as it allows positioning device with tubular construction to be applied and fit to users  702  of different ages and with different sized and shaped heads. Distance  711  may be selected for different embodiments based on multiple factors including size, weight, comfort, and other factors but may generally be in the range of one to several inches. It is also noted that in  FIG. 7B , the sections of positioning device with tubular construction  700  behind the ears of user  702  including end housings  718  and end positioning interfaces  710  are oriented slightly outward, away from the back of the head of user  702 . In some embodiments, sections of positioning device  700  may be oriented outward behind the ears of user  702 , as shown, providing easier access to the back portions of user&#39;s  702  head and scalp. Other embodiments employ positioning devices kept partially or fully in close contact with the face and head of user  702 . 
       FIG. 7C  shows positioning device with tubular construction  700  from  FIG. 1  in which user  702  is omitted such that an unobstructed view of positioning device with tubular construction  700  is possible. The elements of  FIG. 7C  are identically numbered to those in  FIG. 7A  with the addition of ear hooks  715  (ear hooks  715  are not numbered in  FIG. 1  as view of them is almost entirely obstructed by the ears of user  702 ). Ear hooks  715  as shown in the embodiment of  FIG. 7C  provide support by hooking over the tops of the ears of a user wearing positioning device with tubular construction  700  and also allow some tension to be developed between the back of the ears of a user to the head band  708 . In this way, head band  708  may fit the forehead of a user with some tension so that it is less likely to slip. Head band  708  may be formed from or include rubber, plastics, springs, or other elastic materials so that it may maintain tension against the forehead of a user. Head band  708  may also be adjusted in length and in position along main tube  704  using band connectors  706 . Ear supports  714  may also be formed from materials that are able to be flexed so that some pressure may be maintained against the back of the ears of a user wearing positioning device with tubular construction  700 . Additional embodiments of positioning device with tubular construction  700  are possible in which other support features or techniques are incorporated instead of or in addition to head band  708  and ear supports  714 . For example, positioning device with tubular construction may be supported with features that contact the temples, checks, ear lobes, inside the ears, in front of the ears, below the ears, behind the ears, above the ears, eye sockets, nose, mouth, and other regions of the face and head of a user. Ear hooks  715  may be fabricated from metals, plastics, wire, or other materials. Flexible ear hooks  715  made from loops of string, wire, or other materials that partially or fully encircle the ear of a user are also possible. 
       FIG. 7D  shows an embodiment of positioning device with tubular construction  700  from  FIG. 1  folded at hinges  716  for compact storage. The regions of positioning device with tubular construction  700  near ear supports  714  have been folded across each other and the region of positioning device with tubular construction  700  near head band  708  has been folded downwards. Hinges  716  in the embodiment shown include special construction to allow for both pivoting and folding for the embodiment as shown in  FIG. 7D  to be possible. Alternate embodiments of positioning device with tubular construction  700  or other possible positioning devices may contain many combinations of hinges, pivots, telescoping elements, ball joints, flexible materials, elastic materials, actuators, and other possible elements to fold or otherwise be re-configured conveniently. 
     Before describing  FIGS. 7E and 7F , it should be noted that, in addition to observing a positioning device through a camera (with or without structured light), embodiments of positioning structures are possible in which the user may also be “directly” observed. Direct observation of the face or head of a user may be used in conjunction with a positioning device (and in conjunction with accelerometers, gyroscopes, etc.) to compute position and/or orientation of a hair cutting device. It is also possible to have embodiments of positioning structures that do not use a positioning device (as noted in the Detailed Description with reference to  FIG. 1 ) and that determine position and/or orientation only through direct observation of the user (again, with or without structured light and potentially in conjunction with use of accelerometers, gyroscopes, etc.). Cameras may also be used to ensure substantially proper placement of a positioning device on a user&#39;s face, and to detect if a positioning device has moved from correct placement. Cameras may be the camera  107  of  FIG. 1 , a camera or cameras mounted on hair cutting devices such as camera  216  mounted on hair cutting device  200  of  FIG. 2 , or could be cameras in sensor hubs  904  ( FIG. 9 ), or other cameras. 
       FIG. 7E  is an illustration of an embodiment of a positioning device with easily visible features  701 . Ear supports  714 , head band  708 , band connectors  706 , main tube  704 , regions of narrow tubing  705 , and user  702  are all visible and provide similar functions to like numbered elements in  FIG. 7A . However, unlike the embodiment of  FIG. 7A , the embodiment of positioning device with easily visible features  701  of  FIG. 7E  has first visible positioning interface  720 , second visible positioning interface  722 , third visible positioning interface  724 , and end visible positioning interface  726  that are larger and of various shapes versus the smaller spherical positioning interfaces  712  of  FIG. 7A . First visible positioning interfaces  720  are cubical, second visible positioning interface  722  is pyramidal, third visible positioning interfaces are spherical, and end visible positioning interfaces  726  are hexagonal. Certain embodiments of positioning devices employ easily visible and distinguishable positioning interfaces (such as first visible positioning interface  720 , second visible positioning interface  722 , third visible positioning interface  724  and end visible positioning interface  726 ) and cameras (such as camera  216  on hair cutting device  200 , or camera  107  on electronic computing device  106 ). By observing first visible positioning interface  720 , second visible positioning interface  722 , third visible positioning interface  724 , and end visible positioning interface  726  through a camera and performing analysis with computer vision algorithms, the relative positions of first visible positioning interface  720 , second visible positioning interface  722 , third visible positioning interface  724 , and end visible positioning interface  726  may be easily distinguished and used to make a determination of the position and orientation of the camera relative to positioning device with easily visible features  701 . Embodiments employing such a camera allow the calculation of position and orientation of hair cutting device  200  relative to positioning device with easily visible features  701 . In alternate embodiments, first visible positioning interface  720 , second visible positioning interface  722 , third visible positioning interface  724 , and end visible positioning interface  726  may also provide the function of positioning interfaces as described in  FIG. 1 , where signals and propagation delay computations for are employed for determining position or orientation. Certain embodiments employ positioning interfaces as visible features that may be observed by cameras, video cameras, imagers, or other elements capable of generating video or images from which position or orientation may be computed. Other embodiments employ positioning interfaces as signal transmission or reception functions from which propagation delay computations may be used to determine position or orientation. Yet other embodiments employ a combination. 
     In  FIG. 7E , bearing  721  and handle  717  are also shown. Bearing  721  may be a simple bearing consisting of an axle and cylindrical sleeve, a roller bearing, a ball bearing or other types of bearing. Certain embodiments couple ear support  714  to main tube  704 , end housing  718 , and other elements of a positioning device through a bearing  721  to allow the positioning device to pivot at the bearing  721 . Consequently, ballast or weight from batteries, electronics, and other elements within end housing  718  act as a lever force over bearing  721  to keep head band  708  against the forehead of user  702 , improving the stability of head band  708  on the forehead of user  702 . Rotary springs, springs, elastic, rubber bands, or other elements could further be used to pull ear supports  714  against the back of the ears of user  702  by pulling against ear support  714  relative (in a forward direction so as to create pressure on the back of the ears of user  702 ) to other portions of a positioning device. Handle  717  is shown attached to ear support  714  and configured to allow user  702  or another person to rotate ear support  714  in bearing  721 . Handle  717  or other embodiments of handles, tabs, knobs, levers, extensions, or other features allowing a person to easily rotate ear support  714  may benefit some embodiments as they may allow user  702  or another person to more easily put on and position positioning device with easily visible features  701  or other possible positioning devices more easily. 
     In  FIG. 7F , an embodiment of a positioning device with easily visible features  703  is shown in which like numbered elements perform substantially identical functions to those of positioning device with easily visible features  701 , shown in  FIG. 7E . Positioning device with easily visible features  703  as shown in  FIG. 7E  does not include bearing  721  or handle  717  (although some embodiments of it do), but employs ear support  714  as was shown for positioning device with tubular construction  700 . Additionally, positioning device with easily visible features  703  includes dots  730 , stripes  732 , and stripes  734 . Dots  730 , stripes  732 , and stripes  734  are the result of illumination with structured light from a light source such as illumination device  218  on hair cutting device  200  as shown in  FIG. 2 . Visible features from structured light such as dots  730 , stripes  732 , and stripes  734  offer additional information as the application of structured light may allow distance and orientation to be determined from analysis of the dots  730 , stripes  732 , stripes  734 , or other features resulting from structured light. For example, the center-to-center distance between dots  730  may provide an indication of how far they are away from the structured light illumination source (and, hence, how far away they are from hair cutting device  200  if the illumination source is mounted on hair cutting device  200 ). 
     A positioning interface may be a visible or invisible feature, specifically, the positioning interface may be any possible feature or element that could be observed or interacted with to generate position information. The positioning interface may be a physical marking, a decal, an image, a paint mark, an indentation, a recognizable physical feature, a recognizable physical structure, an electronic transmitter, an electronic receiver, an antenna, a speaker, a microphone, a transducer, a sensor, a sensing point, or any other possible feature or structure or combination of features or structures that may be detected in some fashion, whether visible or not, so that position information may be determined. 
       FIG. 7F  also includes auxiliary positioning device  740  around the neck of user  702 . Auxiliary positioning device  740  includes positioning interfaces  742  and may include all types of positioning interfaces that have been described. Auxiliary positioning device  740  provides an example and shows that positioning devices may be broken into multiple parts that interact with each other, with hair cutting devices and other possible elements of an automated hair cutting system  100  through wired or wireless interfaces. It is noted that auxiliary positioning device  740  is around the neck of user  702 , so it would not normally move with the movement of the head and face of user  702 . However, through interaction with positioning device with easily visible features  703 , the position and orientation of auxiliary positioning device  740  may be computed allowing positioning interfaces  742  to provide beneficial information to automated hair cutting system  100 . Many different types of auxiliary positioning devices are possible that may be affixed to a user  702  in a wide variety of positions and orientations so that a wide range of benefits may be delivered. 
       FIG. 8A  shows an embodiment of a positioning device with tubular construction in which some positioning interfaces extend above a user&#39;s head  802  or extend behind. In  FIG. 8A , upper positioning interface  812  is shown above top reference line  806  that extends over the top of user&#39;s head  802  so that substantially all regions of the top user&#39;s head  802  have a line of sight connection possible to upper positioning interface  812 . Lower positioning interface  810  is shown behind back reference line  804  that extends behind user&#39;s head  802  so that substantially all regions of the back of user&#39;s head  802  have a line of sight connection possible to lower positioning interface  810 . Embodiments such as the one of  FIG. 8A  in which some regions of user&#39;s head  802  have line of sight connections possible to some positioning interfaces may offer benefit of additional accuracy. This may be especially true if light, optical, infrared or other signals that propagate in straight lines are used as positioning signals in an automated hair cutting system  100 . 
       FIG. 8B  shows the embodiment of  FIG. 8A  of a positioning device with tubular construction in which some positioning interfaces either extend above user&#39;s head  802  or extend behind; and further illustrates how sensors  824  may be placed on a hair cutting device  820  so that obstruction from the hands and arms of a person operating the hair cutting device  820  may be minimized. In  FIG. 8B , sensors  824  are placed substantially near the cutter head of hair cutting device  820  and an extended handle  822  is provided so that hands and arms may be kept substantially away from the path between sensors  824  and at least some of the positioning interfaces shown in the embodiment. As is visible in  FIG. 8B , the hand or arm of a person on handle  822  of hair cutting device  820  may be easily kept away from a line of sight from the sensors  824  shown on hair cutting device  820  to upper positioning interface  812 . Similarly, sensors  824  may benefit from reduced obstruction due to hands and arms of a person on the handle  822  of hair cutting device  820  to lower positioning interface  810  when hair cutting device  820  is positioned behind user&#39;s head  802 . While the embodiment of a hair cutting device  200  shown in  FIG. 2  included a sensor  208  on handle  206  for the benefit of maximum spacing of the sensors  208 ,  FIG. 8B  illustrates that certain embodiments minimize obstruction from the hands and arms of people operating automated hair cutting system  100  if sensors  824  are kept substantially away from handle  822  of hair cutting device  820  as shown. 
       FIG. 9  shows an embodiment of an automated hair cutting system in which sensor hubs  904  contribute to operation of the automated hair cutting system and in which sensor hubs  904  are affixed to a wall, mirror  902 , or are otherwise mounted near a user  102 . Certain embodiments employing sensor hubs  904  offer improved accuracy of automated hair cutting system  100 , or may reduce size, weight, or complexity of a positioning device  108 . Positioning device  108  may communicate with sensor hubs  904  through wired or wireless interfaces. Sensor hubs  904  may be battery operated or receive power through wires. Sensor hubs  904  may be affixed to mirror  902  or other surfaces with adhesive, tape, suction cups, or other techniques. Sensor hubs  904  may contain positioning interfaces  712  (as previously described), cameras, imagers, radar, sonar, lidar, structured light illumination sources, scanning lasers, or other electronic elements that allow sensor hubs  904  to monitor the position, orientation, hand position, arm position, head position, hair position, hair style, and/or other aspects of user  102 . Sensor hubs  904  may also contain indicator lights, buzzers, chimes, speakers, microphones, gesture recognition devices, time-of-flight monitors, or other elements that allow sensor hubs  904  to communicate with user  102 . Information may be exchanged between multiple sensor hubs  904 , user  102 , positioning device  108 , electronic computing device  106  (not shown in  FIG. 9 ), hair cutting device  200  (not shown in  FIG. 9 ), and other possible elements of automated hair cutting system  100  to provide guidance, control and other information that may be beneficial in the operation of automated hair cutting system  100 . The embodiment of  FIG. 9  shows three sensor hubs  904 , but embodiments with other numbers of sensor hubs  904  are also possible. 
       FIG. 10A  is an illustration of one embodiment of an outline  1002  of a first type of human scalp. Human scalp outline  1002  may be formed by flattening a three-dimensional model of a human scalp to form a two-dimensional outline as shown in  FIG. 10A . Flattening a three-dimensional model of a human scalp to form a two-dimensional human scalp outline may involve some stretching and/or compression of some parts of the model and such an operation may mean that the distances between points on outline  1002  may not correspond precisely with distances between the same represented points on a corresponding three-dimensional model (much as two dimensional maps of the earth include some stretching or expansion versus distances on an earth globe). For many hair styles a substantially smooth translation of hair length from one region of a person&#39;s scalp to another is employed and so, such distortions in the modeling process may not cause problems in achieving an acceptable haircut. Different human beings have different scalps. Certain aspects of outline  1002  shown in  FIG. 10A  include a front peak  1010 , a side burn  1004 , an ear opening  1008 , and a flat back  1006 . Outlines such as outline  1002  in  FIG. 10A  may be employed in some embodiments of automated hair cutting systems  100  as a user  102  of such a system may provide information about the type of scalp they have or through use of automated hair cutting system  100 , information about the type of scalp user  102  has may be determined directly by measurements, camera images, and other techniques. The information may be employed to determine possible hair styles, modifying or adjusting styles for beneficial results, fitting particular hair styles to a specific user  102 , or for other purposes. 
       FIG. 10B  is an illustration of another embodiment of a human scalp outline  1022 . Outline  1022  is an example of a human scalp having a flat front  1024 , a side peak  1028 , a side burn  1004 , an ear opening  1008 , and a back peak  1026 . Various embodiments of an automated hair cutting system  100  provide many different human scalp outlines that may be associated to specific users. Some of these human scalp outlines may be specific to males and females, while others may be applicable to people of either sex. 
       FIG. 10C  is an illustration of how the location of positioning interfaces on a positioning device may be determined relative to reference points on the head of a user  1130 . The embodiment of  FIG. 10C  is based on signal propagation times from positioning interfaces to sensors on a hair cutting device or stylus. Additional embodiments are possible that include position or orientation measurements based on camera images, radar, sonar, lidar, images taken under illumination by structured light, and by other techniques. First positioning interface  1134 , second positioning interface  1136 , third positioning interface  1138 , and fourth positioning interface  1140  are mounted on main tube  1132 . Additional positioning interfaces, head bands, ear supports, hinges, other supports and other possible features of some embodiments of a positioning device are not shown in  FIG. 10C  to avoid cluttering the figure. In  FIG. 10C , main tube  1132  and the positioning interfaces as shown are part of an embodiment of a positioning device. First reference point  1150  at front center of user&#39;s  1130  scalp, second reference point  1152  at top center of user&#39;s  1130  scalp, third reference point  1154  at lower end of side burn of user&#39;s  1130  scalp, fourth reference point  1156  at top of user&#39;s  1130  ear, and fifth reference point  1158  at back center of user&#39;s  1130  scalp are shown in  FIG. 10C  as circles with cross hairs inscribed. Positioning interface locations may be established relative to reference points by prompting a user  1130  or other person operating automated hair cutting system  100  to position hair cutting device  200 , stylus  1302 , or other suitable device to a desired reference point and provide an acknowledgement to automated hair cutting system  100  that the hair cutting device  200 , stylus  1302 , or other suitable device is properly positioned at the reference point, so that the distances from each sensor  208 , located on such a stylus  1302 , hair cutting device  200 , or other suitable device to each positioning interface, may be determined. Distance ranges  1160  from the positioning interfaces to the reference points in  FIG. 10C  may be substantially precisely measured as explained previously from signal propagation measurements or other described techniques. As shown in  FIG. 10C , multiple distance ranges  1160  are shown from each reference point to each positioning interface. In certain embodiments it is not possible to measure the distance range  1160  from every reference point to every positioning interface as the head of user  1130 , or other obstructions may block some signal paths. However, certain embodiments will allow a sufficiently large number of distance ranges  1160  to be measured so that automated hair cutting system  100  may operate.  FIG. 10C  also shows positioning interface distance ranges  1162  that represent the distance from one positioning interface to another. Depending on the design of a specific positioning device, the distance from various positioning interfaces to other positioning interfaces may or may not be precisely known. A specific embodiment of a positioning device may contain hinges, flexible members, telescoping members, or other features that allow the dimensions between various positioning interfaces to vary from one use to a next. Some embodiments of positioning devices may allow the distance between various positioning interfaces to be determined electronically. As shown in  FIG. 10C , the distance between some of the positioning interfaces may be known and those known positioning interface distance ranges  1162  may also be used in computations to determine positioning device locations based on reference points. Multiple distance ranges  1160  or positioning interface distance ranges  1162  from each reference point to each positioning interface, or between positioning interfaces, allow substantially precise locations of positioning interfaces to be computed relative to the reference points as shown in  FIG. 10C . If reference point locations are known, then the locations of positioning interfaces may be determined from them as described. If the reference points of the embodiment of  FIG. 10C  are established on a scalp outline such as human scalp outline  1002 , human scalp outline  1022 , or other possible human scalp outlines, then the location of first positioning interface  1134 , second positioning interface  1136 , third positioning interface  1138 , and fourth positioning interface  1140  may also be substantially projected on the scalp outline. Reference point locations may also be determined with reference to solid models such as three-dimensional model  1102  shown in  FIG. 11 . In certain embodiments three or more distance ranges  1160  or positioning interface distance ranges  1162  are needed to determine the location in three dimensional space of a positioning interface relative to the locations of the reference points from which those distance ranges  1160  were determined. Embodiments of automated hair cutting systems  100  may employ multiple sensors  208  on hair cutting devices  200  or on stylus  1302 , so several distance ranges  1160  between the various sensors and positioning interfaces may be measured. Embodiments employing such an over-determined system may mitigate sensors or positioning interfaces being blocked at various times by the hands or arms of user  1130 , other people or covered with hair or other items (such as combs, brushes, etc.). Such an over-determined system may also allow embodiments of the system and method to accommodate a range of users with various sized and shaped heads. In embodiments employing three-dimensional models, three-dimensional mathematics may be applied and substantially precise locations of the various sensor interfaces relative to the reference points of the scalp of a user  1130  may be determined. In embodiments employing two-dimensional scalp outlines, various distortions and approximations are involved to transform a three-dimensional human scalp to a flat plane human scalp outline. With regard to the positioning interfaces shown in  FIG. 10C , for example, their positions may be projected to a human scalp outline by determining their perpendicular projection to a plane tangential to the scalp or head of user  1130 . 
     If all users  1130  of an automated hair cutting system  100  had the same size and shape of head then reference point locations could be measured and used for all possible users of automated hair cutting system  100 , and the embodiment of  FIG. 10C  would then be closely analogous to GPS (Global Positioning System) (since there is only one Earth inside the GPS satellite constellation). Certain embodiments accommodate many different users  1130  with a large range of head sizes and shapes, ear locations, and scalp sizes. Certain embodiments assume a standard head model, such as three-dimensional model  1102  with reference point locations that are substantially precisely known in three-dimensional space. It is then possible to vary the assumptions of the size, shape, and other features of the standard head model so that the distance ranges  1160  measured result in self-consistent computations for the locations of the positioning interfaces, regardless of which distance ranges are used to compute the location of a specific positioning interface. For example, if a specific user  1130  has a smaller head than an assumed standard head model, then the distance range  1160  measured from first reference point  1150  to first positioning interface  1134  may be inconsistently long relative to the measured distance range  1160  from fourth reference point  1156  to first positioning interface  1134 . This concept applies to many distance ranges  1160  that may be inconsistent if an assumed standard head model does not sufficiently match the shape and size of the head of the specific user  1130  using the automated hair cutting system  100 . Alternate embodiments are possible where adjustment of the size assumptions of the standard head model will allow the many distance ranges  1160  measured to become sufficiently self-consistent; and once this is accomplished, the locations of each positioning interface may be sufficiently computed. Recursive algorithms, analytic algorithms, search algorithms, and other types of algorithms may be employed to determine a correct head model with reference point locations that match those of the specific user  1130  to acceptable tolerances. 
     Other embodiments employ alternate approaches to determine and fit reference points of a specific user to a model so that consistent positioning interface locations may be computed and hair styles may be fitted to those models. These approaches include direct measurement to determine the size and shape of the head of a specific user  1130 , analysis of camera images of a specific user  1130 , analysis of camera images of a specific user  1130  taken under illumination with structured light, precision measurement of the locations of reference points of a specific user  1130  using a substantially precise three-dimensional measurement system, solid modeling techniques, or Lidar scanning. 
     Since embodiments may exist in which positioning interface locations are substantially over-determined by reference point locations and measured distance ranges  1160 , as previously explained, it is also possible to favor certain reference point locations and measured distance ranges  1160  for the determination of a specific positioning interface location. For example, third positioning interface  1138  is near the ear of user  1130  in  FIG. 10C , so some embodiments may favor signals from third positioning interface  1138  in determining the position and orientation of hair cutting device  200  for hair cutting operations near the ear of user  1130 . Certain embodiments may favor reference points near the ear of user  1130  in determining the location of third positioning interface  1138 , so that more precise hair cutting may be substantially achieved. In other words, use of third reference point  1154 , fourth reference point  1156  and fifth reference point  1158  may be favored for the determination of the location of third positioning interface  1138 , as shown in  FIG. 10C , versus other possible reference points. 
     Some hair cutting operations may benefit if certain positioning interface locations are substantially more precise relative to certain reference points, and that other hair cutting operations may benefit if those same positioning interface locations are substantially more precise relative to other reference points. Consequently, certain embodiments are possible in which positioning interface locations are recomputed from more favorable reference points specific to hair cutting operations about to be undertaken. In this fashion, positioning interface locations may be recomputed multiple times during a haircut to improve precision. 
     In certain embodiments, a mathematical correction may be employed in orientation measurements using the stylus  1302 , hair cutting device  200  or other device. Such corrections may include use of accelerometers or other orientation, tilt, or gravity sensing devices. 
     Signal propagation times from a positioning device to multiple sensors on a stylus  1302 , hair cutting device  200 , or other device may be used to measure reference points in some embodiments. Errors in orientation using signal propagation measurements, arising before reference points and positioning interfaces have been substantially determined, may be managed by using sensors and positioning interfaces for orientation measurement that are normally positioned to be insensitive to precise sensor or positioning interface location. Alternatively, relatively minor errors may be accommodated without compensation. 
       FIG. 10D  shows the outline of a first type of human scalp from  FIG. 10A  where positions on the human scalp outline  1002  may be designated by coordinates relative to an embodiment of an x-axis  1040  and a y-axis  1042 . Incorporation of an x-axis  1040  and a y-axis  1042  may allow any point on the scalp of a user of an automated hair cutting system  100  to be referenced relative to the x-axis  1040  and/or the y-axis  1042  with numerical coordinates. These numerical coordinates may provide distances in quantified measures such as millimeters, centimeters, inches, etc., or in relative distance as a percentage of the size of human scalp outline (for example, as a percentage of the total dimension of human scalp outline  1002  along the y-axis  1042 ). The location of the positioning interfaces shown in  FIG. 10C  are shown projected onto the coordinate system shown in  FIG. 10D . As noted in the description of  FIG. 10C , such a projection may be computed as a perpendicular projection from a positioning interface to the surface of the scalp or head of a user, but other projections are also possible. As  FIG. 10C  was a side view of the head of user  1130 , only four positioning interfaces were visible; whereas the scalp outline of  FIG. 10D  includes the additional four positioning interfaces around the head of user  1130  that were not visible in  FIG. 10C . The positioning interfaces of  FIG. 10C  are shown like numbered for the left and right sides of  FIG. 10D  (that is, left and right of the y-axis  1042 ) and first positioning interface  1134 , second positioning interface  1136 , third positioning interface  1138 , and fourth positioning interface  1140  are shown. Many alternate systems of coordinates and axes are possible in addition to the rectangular coordinates shown in  FIG. 10D . For example, a polar coordinate system based on angles from a reference vector and distance from a center point may also be used. A very wide range of coordinate systems are possible and may be applied. 
       FIG. 10E  shows the outline of a first type of human scalp from  FIG. 10A  in which a region of thinned hair  1052  and a region of a skull irregularity  1050  are designated relative to an embodiment of an x-axis  1040  and a y-axis  1042 . Human&#39;s may have regions of their scalp with especially thick or thin hair, regions of coarse hair, bald spots, regions with gray or graying hair, or other irregularities in their hair. Humans may have regions of their skull that are normally shaped, but have depressions, ridges, or other irregularities. By noting these regions as shown by example in  FIG. 10E , certain embodiments of automated hair cutting system  100  may account for them and make adjustments to hair styles and recommendations to users of the system so that they achieve potentially beneficial results. The region of thinned hair  1052  and the region of a skull irregularity  1050  in  FIG. 10E  may be encoded with coordinates relative to the x-axis  1040  and the y-axis  1042 . 
       FIG. 10F  shows an embodiment of a table  1060  that provides information specific to hair in specific regions of a first type of human scalp outline  1002  where the specific regions are designated by coordinates relative to an embodiment of an x-axis  1040  and a y-axis  1042 . Title row  1061  of table  1060  provides representative column headings that are optional and may not be present in all embodiments. Each row of table  1060  below the title row  1061  includes a coordinate in a first column  1062  that references x-axis  1040 , and a coordinate in a second column  1064  that references y-axis  1042 . For each row in table  1060 , the remaining columns provide information about the hair in the region referenced by the coordinates in the first column  1062  and second column  1064  as follows: a third column  1066  provides a present length (designated P-L in table  1060 ), a fourth column  1068  provides a desired length (designated D-L in table  1060 ), a fifth column  1070  specifies an accuracy tolerance to which hair should be cut (designated Tol in table  1060 ), and a sixth column  1072  provides an indicator of the thickness of hair (designated Typ and denoted: TH for thin, M for medium in table  1060 ). First reference line  1074  shows how a specific region on human scalp outline  1002  is mapped to the first row of table  1060 . Second reference line  1076  shows how a specific region on human scalp outline  1002  is mapped to the second row of table  1060 . Third reference line  1078  shows how a specific region on human scalp outline  1002  is mapped to the third row of table  1060 . Fourth reference line  1080  shows how a specific region on human scalp outline  1002  is mapped to the fourth row of table  1060 . 
     Mapping from human scalp outline  1002  to table  1060  as shown in  FIG. 10F  allows all regions of human scalp outline  1002  to be mapped such that a substantially complete tabular record of human scalp outline  1002  may be created in table  1060  through the addition of rows to table  1060 . It is clear that each row of table  1060  contains specific information regarding how hair is to be cut in that specific region and that with other aspects of the system and method, specific hair styles may be represented for specific people so that acceptable results may be achieved. Table  1060  may also include other or additional columns to provide information regarding hair types (bristly, curly, straight, etc.), hair color (gray, white, blond, brown, etc.), skull irregularities (may be noted as higher or lower regions with deviations from nominal provided as quantified measurements), or any other features of hair relative to specific regions of human scalp outline  1002 . In certain embodiments, table  1060  may be represented in a computer as an array of numbers, as a spreadsheet, or through other electronic computing techniques. It is noted that the numerical values presented in table  1060  are for example purposes only and, apart from the first column  1062  and second column  1064  that correspond to locations of human scalp outline  1002  as already shown and explained, the numerical values in table  1060  do not convey numerical information of specific interest. 
     Human scalp outline  1002  and table  1060  as presented in  FIG. 10F , may substantially contain the information needed by automated hair cutting system  100  to determine the length hair should be cut to for a user  102 . It was explained in the description of  FIG. 1  that user  102  may be asked to place hair cutting device  200  or a stylus  1302  on reference points so that positions on the head and scalp of user  102  may be accurately referenced by positioning device  108 . Referring again to  FIG. 1 , these reference points may include the tops of user&#39;s ears  152 , the back of user&#39;s neck at a collar line  154 , the tops of user&#39;s eyebrows  150 , and other reference points that are of specific interest in properly fitting a given hairstyle to a user&#39;s  102  head and facial features. Other reference points might include the front and back of a user&#39;s ears, the sides of a user&#39;s  102  eye sockets, the user&#39;s  102  hair line (the point at which the user&#39;s  102  hair scalp ends and skin without thick hair begins) at various points around the user&#39;s  102  scalp, and other reference points. Those skilled in the art will recognize that by determining reference points as described, the human scalp outline  1002  and table  1060  of  FIG. 10F  may be referenced to specific locations on the head of a user  102  for a specific placement of positioning device  108  on the head of user  102 . And in this way, table  1060  may be used to provide substantially precise information for how long to cut the hair at each region of a user&#39;s  102  scalp so that automated hair cutting system  100  may achieve acceptable results. 
       FIG. 11  is an illustration of an embodiment of a three-dimensional model  1102  of a human head. Three-dimensional model  1102  partitions the surface of a human head into specific regions  1104 . Three such specific regions  1104  are numbered for reference in  FIG. 11 , but all the rectilinearly defined regions may be specifically referenced. Since certain regions of the human head may not be of interest in the operation of an automated hair cutting system  100 , no rectilinearly defined regions are defined for the eye socket area  1108  and the ear area  1106 . Certain embodiments of automated hair cutting system  100  may employ a three-dimensional model  1102  of a human head instead of the two-dimensional scalp outlines that were explained in  FIGS. 10A-10F . Other embodiments employ coordinate axes and tabular information as was explained in  FIGS. 10A-10F  extended to a three-dimensional model  1102  such as the one shown in  FIG. 11  and may be used in a similar fashion in support of operation of automated hair cutting system  100 . 
       FIG. 12  is an illustration of one embodiment of a hair dye dispensing device  1202  including sensors  208 , indicator lights  212 , accelerometer  210 , body  1206 , handle  1204 , comb  1208 , and dispensing slot  1210 . Hair dye dispensing device  1202  provides an example of an alternative device to a hair cutting device  200  that may be used in conjunction with an automated hair cutting system  100  to provide a function besides cutting hair. Sensors  208 , indicator lights  212 , and accelerometer  210  provide analogous functions to those described with regard to  FIG. 2  regarding hair cutting device  200 . Handle  1204  allows a user  102  to grip and position hair dye dispensing device  1202 . Body  1206  may contain a container of hair dye; motors, valves, piping, and other elements to dispense hair dye; electronics and computing elements to control hair dye dispensing device  1202 ; and other functions. Comb  1208  allows specific hair to be gathered so that it may receive application of dye at the precise locations desired. And dispensing slot  1210  may spray, squeeze, or otherwise dispense hair dye at precise times and locations under control of automated hair cutting system  100 . Embodiments of hair dye dispensing device  1202  may include the ability to dispense multiple dye types or colors of dye so that specific hair in specific locations on a user&#39;s  102  head may be dyed to create interesting styles. 
       FIG. 13  shows an embodiment of a stylus  1302  that may be used for providing reference point information. As previously described, reference points such as those shown in  FIG. 1  (top of ear  152 , back of user&#39;s  102  neck at a collar line  154 , etc.) may be used to allow automated hair cutting system  100  to accurately determine precise locations on a user&#39;s  102  head even if position device  108  (or other embodiments of positioning devices) is not precisely located on user&#39;s  102  head. While hair cutting device  200  may be used for determining reference points with its cutter head  202  disabled, a light weight stylus  1302  such as the one shown in  FIG. 13  may be easier to use. Sensors  208  shown on stylus  1302  allow precise location of tip  1306  to be determined while a user  102  holds it by handle  1304  and positions it to specific reference points as desired. Additional sensors  208  may be incorporated into stylus  1302  on the side not visible in  FIG. 13 . Stylus  1302  may contain a button, switch, or other element (these are not shown in  FIG. 13 ) to allow a user to acknowledge to stylus  1302  that a reference point is being properly touched. Stylus  1302  may be battery operated or powered from a wired connection. It may also include wireless or wired interfaces to allow it to communicate to other elements of automated hair cutting system  100 . Stylus body  1304  may be constructed from wood, metal, plastics, or other materials. Some embodiments of hair cutting device  200  or other hair cutting devices shown in this patent application may employ a stylus  1302  built into their structure. That is, a physical element, stylus tip  1306 , or other feature suitable for the purpose of touching reference points may be present on such a hair cutting device or may extend through electronic control or manual extension from the structure of such a hair cutting device so that the benefit of higher precision in using a stylus for determining reference points may be achieved without the need for a separate stylus. 
     Those skilled in the art to which this application relates will appreciate that other and further additions, deletions, substitutions and modifications may be made to the described embodiments.