Abstract:
This device is a handheld, battery-operated instrument that utilizes light beams to project visible lines for increasing the accuracy in determining angles. A linear potentiometer is incorporated at the pivot point between the two diodes and measures a voltage change based on the angle between the arms of the device.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
   This patent application claims priority based on provisional application U.S. Ser. No. 60/360,122, filed on Feb. 28, 2002. 

   FIELD OF THE INVENTION 
   An apparatus for measuring the angle between two rays, wherein the apparatus comprises a light source for generating a first light beam and a second light beam, a means for aligning these light beams to determine an angle to be measured. 
   BACKGROUND OF THE INVENTION 
   A goniometer is a device for measuring or setting angles. Prior art goniometers have utilized a number of principles to determine angles. Reference may be had, for example, to The Biomedical Engineering Handbook (Joseph D. Bronzino Ed., CRC Press LLC, 1995) pages 2177-2182. 
   Prior art goniometer designs include the following categories; Universal, Arthroidial, Fluid, Pendulum, Myrin OB, and Electrogoniometer. 
   The Universal Goniometer comprises a protractor-like measuring device with one movable arm and one stationary arm. The two arms are superimposed on the rays of the angle, and the measurement may be read on the protractor. Often, several goniometers of different sizes are required to measure different digits (i.e. a knee versus a finger). Additionally, the increments on the protractor limit the sensitivity of the measurement to the gradations on the instrument. The placement of the arms is also a source of error, as it is difficult to properly align relatively small arms parallel to a large extremity. Providing longer arms on the device may compensate, but this negatively impacts the portability of the device. Reference may be had, for example, to The Biomedical Engineering Handbook (Joseph D. Bronzino Ed., CRC Press LLC, 1995) page 2181. 
   The Arthroidial goniometer is a single protractor, similar to the Universal goniometer, but lacking arms. These instruments likewise suffer the same drawbacks. Reference may be had, for example, to The Biomedical Engineering Handbook (Joseph D. Bronzino Ed., CRC Press LLC, 1995) page 2181. 
   Fluid and Pendulum Goniometers utilize gravity to aid in measuring angles. Fluid goniometers contain a fluid-filled channel with an air bubble that moves as the device changes its angle relative to the gravitational plane. Likewise, Pendulum goniometers contain a pendulum for detecting angular changes. Such goniometers are often more accurate than their universal counterparts, but are additionally more expensive. Reference may be had, for example, to The Biomedical Engineering Handbook (Joseph D. Bronzino Ed., CRC Press LLC, 1995) page 2181. 
   Myrin Goniometers exploit a combination of gravity sensing devices and magnetic field sensing devices that respond to the Earth&#39;s magnetic field. These goniometers are often bulky and useless for measuring the angles associated with small joints, such as the fingers. They additionally suffer to electromagnetic interference. Reference may be had, for example, to The Biomedical Engineering Handbook (Joseph D. Bronzino Ed., CRC Press LLC, 1995) page 2181. 
   Electrogoniometers are physically strapped to the proximal and distal portions of the joint to be measured. These devices are inherently cumbersome and expensive. Each electrogoniometer is designed for specific body parts and they are typically used only as pieces of laboratory equipment. Reference may be had, for example, to The Biomedical Engineering Handbook (Joseph D. Bronzino Ed., CRC Press LLC, 1995) page 2181. 
   By way of further illustration, U.S. Pat. No. 3,634,838 discloses a goniometer arrangement that allows for the digital display of the measured angle. Such a digital display circumvents the difficulties associated with protractor measurements, such as being limited to the increments marked on the protractor. 
   U.S. Pat. No. 4,665,928 of Linial teaches the use of pendulum goniometers to determine angles on a living person. This patent also discloses the use of potentiometers to digitize the measurement, thus avoid protractor-like measurements. 
   U.S. Pat. No. 4,883,069 discloses an electrogoniometer that physically attaches to a joint through the use of straps. 
   U.S. Pat. No. 5,189,799 discloses a goniometer comprised of a single laser to determine the angle of a geographic feature. 
   U.S. Pat. No. 5,832,422 discloses a hand-held measuring device that is capable of measuring angles. The device tracks the angle the device is moved as it proceeds from a first position to a second position. 
   U.S. Pat. No. 6,428,490 discloses a series of resistive bend sensors that may be built into a garment to measure the range of motion for computer animation, for example. Such a suit would be undesirable for simple medical measurements due to the size of the device, its complexity, and its cost. 
   In spite of the substantial amount of prior art disclosing goniometers, these prior art goniometers suffer from a number of disadvantages. Many of the prior art instruments utilize manual, as opposed to digital, measurements, which inherently limit the precision of the measurements to the gradations on the protractor. Additionally, many prior art angle-measuring devices must use long arms in order to accurately visualize the rays of the angle to be measured. These long arms make these devices cumbersome and unsuitable for use with small joints. Additionally, many of the prior art goniometers are expensive, and difficult to transport, diminishing their usefulness as everyday instruments. 
   The instant invention seeks to overcome all of these disadvantages and provide a measuring device that utilizes light beams in place of traditional goniometer arms. The longer the arms of a traditional goniometer, the easier it becomes to estimate the position of the ray of the angle to be measured. However, longer arms make the device less portable. The instant invention replaces the physical arms of prior art goniometers with a beam of light. The long light beams mimic the advantageous function of long arms without requiring a large volume of space. Specifically, one light beam may be aligned along the length of one section of an extremity (i.e. lower leg), while the second light beam may be aligned along the length of a second section of the same extremity (i.e. upper leg). The goniometer may read the angle between the two beams throughout the flexion and extension of the extremity. In this manner, a range of motion may be determined. 
   It is an object of this invention to provide a lightweight, portable, hand-held goniometer. 
   It is another object of this invention to provide a goniometer that can easily, and accurately estimate the position of the two rays of an angle. 
   It is yet another object of this invention to provide a goniometer that digitally displays an angle measurement with a high degree of precision. 
   It is another object of this invention to provide a goniometer that is useful on both large joints and small joints. 
   SUMMARY OF THE INVENTION 
   In accordance with this invention, there is provided an apparatus for measuring the angle formed between a first beam of light and a second beam of light, wherein said apparatus is comprised of a first light source, a second light source movably connected to said first light source, and means for determining the angle formed between said first beam of light and said second beam of light. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described by reference to the specification, and the drawings, in which like numerals refer to like elements, and in which: 
       FIG. 1  is topside view of one embodiment of the light projecting goniometer, in its open position, being used to measure to angle of a joint, for example, a knee; 
       FIG. 2  is a perspective view of one embodiment of the light projecting goniometer in its closed position; 
       FIG. 3  is a perspective view of one embodiment of the light projecting goniometer in its open position; 
       FIG. 4  is a partially transparent view of one embodiment of the light projecting goniometer showing the inner structure of one arm of the device; 
       FIG. 5  is a schematic block diagram illustrating one embodiment of the invention; and 
       FIG. 6  is a schematic view of an alternative embodiment of the present invention. 
   

   DEFINITION OF TERMS 
   As used in this specification, the following terms have the meanings described hereinbelow. 
   The term “angle” refers to the geometric shape or arc that is defined by the intersection of two geometric rays. The term “vertex” refers to the point of intersection. 
   The term “ray” refers to one of the two imaginary geometric rays in an angle, extending outward from that angle&#39;s vertex. In a Universal goniometer, the two rays of an angle are visually approximated by the two arms of the goniometer. In the instant invention, one or more of the rays of an angle are visually approximated with the aid of a light beam. 
   Reference for these definitions may be had to, for example, The McGraw-Hill Encyclopedia of Science &amp; Technology (Daniel N. Lapedes, Ed. McGraw-Hill, 1977) volume 1, page 427. 
   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a schematic of device  10 , one preferred embodiment of the instant invention. As is illustrated in  FIG. 1 , with the device of this invention one may measure any angle. To measure any angle, such as angle  24  in  FIG. 1 , one may place a measuring device (not shown) at vertex  22 . Rays  26  and  28  then define the angle  24 . In the embodiment depicted in  FIG. 1 , it is often difficult to define rays  26  and  28  when the objects with which they are aligned are relatively small. 
   Referring again to Figure, device  10  is one preferred goniometer of this invention. It will be seen that such device  10  preferably comprises means to emit light or similar radiant energy beams  16  and  18 . In the embodiment depicted, these means are disposed within arms  12  and  14 , respectively. Arms  12  and  14  are preferably pivotally connected to each other at pivot point  45  by means of a pivoting means  44  (not shown in  FIG. 1 , but see FIG.  3 ). The pivotal connection provided by the pivoting means  44  allows one to superimpose the light beams  16 / 18  over the imaginary rays  26 / 28  of the angle  24  to be measured. 
   In the preferred embodiment depicted in  FIG. 1 , the angle  24  to be measured corresponds to the bend of a knee joint  68 , defined by angle  20 . 
   In one embodiment, discussed elsewhere in this specification, the pivoting means  44  is connected to a means (not shown in  FIG. 1 ) for determining the extent to which such means  44  has been pivoted. In one embodiment, the means for determining the angle maybe a linear potentiometer (not shown in  FIG. 1 , but see FIG.  5 ). In another aspect of this embodiment, the angle detected by this latter means is displayed in a display area  32 . 
   Referring again to  FIG. 1 , the assembly  10  is comprised of a power switch  34  and a reset/calibrate switch  36 . 
     FIG. 2  is a perspective view of the device  10  of  FIG. 1 , shown it in its closed position. Referring to  FIG. 2 , it will be seen that, in the embodiment depicted, the arm  12  is of an appropriate size and configuration to fit inside of arm  14 . Thus, the device may conveniently be stored in a “closed” position when not in use; in such closed position, it forms a substantially rectangular assembly. In one embodiment of the invention, the device is approximately 3 inches in height, 1.75 inches in width and 0.75 inches in thickness and weighs less than 0.5 kilogram. In another embodiment, the device is approximately 1 inch in height, 0.5 inches in width, and 0.25 inches in thickness and weighs less than 0.25 kilograms. In another embodiment the device is less than 1 cm in height, less than 0.5 inches in width, less than 0.25 inches in thickness, and weighs less than 50 grams. 
   Referring again to  FIG. 2 , and in the preferred embodiment depicted therein, a control panel  30  is mounted on arm  14 . In the embodiment depicted, the control panel  30  is mounted atop arm  14 . In another embodiment, not shown, the control panel  30  is mounted on the side of arm  14 . Additionally, the control panel may comprise means to control the intensity of the light beams, means to indicate a low battery, and means to relay the measured angle to a data storage device. 
   Referring again to  FIG. 2 , it will be seen that disposed on and within control panel  30  are a plurality of device controls and displays, including, for example, reset switch  36 , power switch  34 , and display  32 . Visible on the side of the device is light emission point  40 . In one embodiment reset switch  36  is used to “zero” the device such that display  32  reads an angle of zero degrees. In another embodiment, power switch  34  is used to turn the light sources off so as to prolong the lifetime of the power source. 
     FIG. 3  is a schematic illustration of the device  10 .  FIG. 3  depicts the device  10  in one of its “open” positions. Control panel  30  is visible in this configuration. In this embodiment, disposed within control panel  30  are power switch  34 , reset switch  36 , and display  32 . 
   The display  32  may be any device for displaying the measured angle, such as a liquid crystal display, a light-emitting diode display or any of a number of display types employed in personal digital devices such as cellular phones, etc. 
   Referring again to  FIG. 3 , and in the embodiment depicted, the control panel  30  is mounted atop arm  14 . Housed within arm  14  is a light source  46  (not shown in  FIG. 3 , but see  FIG. 4 ) which projects a beam of light from light emission point  40 . Arm  12  is likewise equipped with a light source  47  (not shown in  FIG. 3 , but see  FIG. 4 ) that preferably projects a beam of light from light emission point  38 . The light emission point  40  may be a hole in the housing of the arm  14 , or other means for delivering light, such as, for example, a fiber optic cable (not shown). 
   Referring again to  FIG. 3 , it will be appreciated that, housed within arm  14  is a power supply (not shown) disposed behind access panel  42 , which may be, for example, a battery. The power supply is preferably adapted to deliver from about 1 to about 12 volts of direct current. It is preferred that an access panel  42  be removable so as to allow replacement of the power supply. Access panel  42  may be secured to device  42  by securing means, such as frictionally restrained by snap locks or securing by screws. 
   In another embodiment, not shown, a power supply may be used that is disposed external to arm  14  and to device  10  and connected to circuitry therein via a wire lead and jack as is commonly known for portable devices. 
   Referring again to  FIG. 3 , arm  12  and arm  14  are pivotally connected to one another by pivot means  44  (not shown in  FIG. 3 , but see  FIG. 4 ) at pivot point  45 . The pivoting means may be, for example, a hinge (not shown in  FIG. 3 , but see  44  in FIG.  4 ). 
     FIG. 4  is a schematic view of goniometer  10 . Referring to  FIG. 4 , and the embodiment depicted therein, it will be seen that device  10  includes of a beam splitter  48 . 
   In the embodiment depicted in  FIG. 4 , the light source  46  preferably provides at least one light beam  50 . In one aspect of this embodiment, the light beam  50  has a wavelength of from about 600 nanometers to about 700 nanometers. 
   As is known to those skilled in the art, a beam splitter is an optical device for dividing a beam into two or more separate beams. As will be apparent, the beam splitter  48  allows one to redirect a light beam so as to project light on a surface directly in front of the device. This allows the beams  52 / 53  to be easily visualized on the surface  55  and greatly aids in visualizing the two rays  72 / 74  of the angle  70  to be measured. An example of such redirection may be seen in FIG.  4 . 
   Referring again to  FIG. 4 , it will be seen that, in the embodiment depicted, light source  46  emits a beam of light in the direction of arrow  50 . When the beam contacts redirection means  48 , the path of the light is altered such that some of the light is projected in the direction of arrow  52 . Additionally, as is illustrated in  FIG. 4 , such redirection may also include spreading of the light  50 , so that a line  52 , as opposed to a single point, may be produced on the surface  55  where the beam strikes in front of the device  10 . 
   Such beam splitters and expanders are well known within the art and may be comprised of a wide variety of materials, including, but not limited to, mirrors, plastics, glass etc. Reference may be had to U.S. Pat. Nos. 5,822,124; 4,645,302; 4,125,864. 
     FIG. 5  is a schematic block diagram of an electronic circuit for detecting the angle between the first and second light beams. As may be seen in  FIG. 5 , and in the embodiment depicted therein, linear response potentiometer  76  provides an analog signal  77  to an analog/digital (A/D) converter  78 . Analog signal  77  is proportional to the angle  70  between rays  72  and  74 . The A/D converter  78  produces digital signal  79 , which is provided to multiplexer  80 . Multiplexer  80  routes digital signal  79  to memory location  84  (“current angle”) if reset switch  90  is not activated. Alternately, if reset switch  90  is depressed, multiplexer  80  stores the value of signal  79  in memory location  82  (“zero angle”). Subtractor  86  then calculates the difference between the value currently in memory location  82  (“zero angle”) and memory location  84  (“current angle”) and continuously displays the result in angle display  88 . It will be appreciated that although described as a “digital” storage and manipulation device, the present invention may be implemented using equivalent analog devices to store/zero and measure the angle between the beams. It should be further appreciated that the present invention may be adapted to include additional data storage and/or display capability in order to facilitate its use in a variety of situations by physical therapists and the like. 
   In an alternative embodiment depicted in  FIG. 6 , only one light source is used. In this embodiment a single light source  46  generates a light beam  60  that is split into two or more independent beams  64  and  66 . Such splitting means may include, for example, a beam splitter  62 , a reflective surface, and/or fiber optic cables  63 . The device is adapted to measure the angle  70  between the two light beams, irrespective of the fact that the two beams originated from the same light source. 
   The larger the goniometer is, the more difficult is its use for measuring small angles, such as those found on digits or fingers. It may be advantageous to minimize the size of the goniometer so as to make it useful with small joints. It should be noted that the instant goniometer is useful for a wide range of joint sizes. The small size of the device allows it to be used at small joints, such as fingers. Likewise, its long light beams, which serve the function of arms, are suitable for use at large joints such as the knee, elbow, hip, etc. 
   It is understood that the aforementioned description is illustrative only and that changes can be made in the apparatus, in the components and their proportions, and in the sequence of combinations and process steps, as well as in other aspects of the invention discussed herein, without departing from the scope of the invention as defined in the following claims.