Abstract:
The present subject matter include methods and apparatus for creating three dimensional digitized models of at least one ear impression, the apparatus comprising a frame, a linear axis mounted to the frame, the linear axis having an axis of motion, a first spindle axis mounted to the frame, the spindle axis having an axis of rotation, wherein the axis of rotation of the first spindle axis is parallel to the axis of motion of the linear axis, a first scanner mounted to the linear axis, the scanner includes a laser for projecting a narrowly localized spot of laser light at a target mounted on the first spindle axis and a sensor array for receiving at least a portion of the laser light reflected from the target and a controller configured to communicate with the first scanner.

Description:
TECHNICAL FIELD 
   This application relates to digital scanning and more particularly to digital scanning to produce three dimensional digital models of ear impressions. 
   BACKGROUND 
   Many hearing assistance devices rely on at least one component residing in the ear canal of the user. A hearing assistance device user&#39;s overall satisfaction with such a device is impacted by the comfort of the device residing in the user&#39;s ear canal. Traditional methods of minimizing discomfort involve a manually intensive process of creating a hearing device housing shell from an impression of the user&#39;s ear canal. Such a process is time consuming and offers the opportunity for the introduction of errors during the manual procedures associated with the process. 
   SUMMARY 
   This document provides method and apparatus embodiments for making a detailed three dimension representation of an ear impression using a compact laser dimension sensor projecting a dot, or a narrowly localized spot, of laser light. The sensor includes both a laser source and line scan sensor within the same housing. The combination laser source and scanner, along with the sensor electronics, allow the sensor to triangulate a reflected dot or narrowly localized spot of laser beam energy generated from the sensor and projected onto the target ear impression, and determine the distance between a reference point and the point at which the laser energy is reflected from the target ear impression. Embodiments of the apparatus further include a spindle axis to rotate the surface of an ear impression within the sensing range of the sensor and a linear axis to move the sensor about one dimension of the ear impression. Additional embodiments include axes of movement to allow the sensor of the system to scan cavities and curves hidden by other structures of the impression or otherwise hidden from the two dimensional movement of the impression and the sensor. Further embodiments include the capacity to build multiple three dimensional models simultaneously such as a matching pair of models for each ear of a patient based on either one impression or a pair of impressions, one from each ear of the patient. A further embodiment of the present subject matter relates to a method of making a three dimensional model of an ear impression, including providing a first spindle, mounting a first ear impression on the first spindle, providing a first scanner for measuring the first object, calibrating the first scanner to provide a reference for measurement of the first ear impression, rotating the first spindle at a predetermined rate of rotation, positioning the first scanner at a first position to begin measurements, wherein the first position locates the scanner to measure the first ear impression near a first end of the ear impression, projecting a first narrowly localized area of laser light from the first scanner toward the first ear impression, recording a first plurality of measurements from the first scanner, processing the first plurality of measurements to generate a first three dimensional data representation of the first ear impression. 
   This Summary is an overview of some of the teachings of the present application and is not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description and the appended claims. The scope of the present invention is defined by the appended claims and their equivalents. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  illustrates one embodiment of a spindle axis according to the present subject matter. 
       FIG. 1B  illustrates two spindle axes assembled as part of a spindle pitch axis according to one embodiment of the present subject matter. 
       FIG. 2  illustrates a linear axis according to one embodiment of the present subject matter. 
       FIG. 3  illustrates a latitudinal axis assembly according to one embodiment of the present subject matter. 
       FIG. 4  illustrates a latitudinal axis assembly mounted to a linear axis according to one embodiment of the current subject matter. 
       FIG. 5  illustrates a frame and assorted control components according to one embodiment of the present subject matter. 
       FIG. 6  illustrates an embodiment of an apparatus adapted to scan and electronically model ear impressions according to the present subject matter. 
       FIG. 7  illustrates one embodiment of a method  751  of generating digitized models of two ear impressions. 
   

   DETAILED DESCRIPTION 
   The following detailed description of the present invention refers to subject matter in the accompanying drawings which show, by way of illustration, specific aspects and embodiments in which the present subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present subject matter. References to “an”, “one”, or “various” embodiments in this disclosure are not necessarily to the same embodiment, and such references contemplate more than one embodiment. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope is defined only by the appended claims, along with the full scope of legal equivalents to which such claims are entitled. 
   The subject matter of this document provide apparatus and methods for creating timely three dimensional modeling of single and complementary ear impressions, or otoplasties, for the automated manufacture of hearing assistance devices. Upon modeling the patient&#39;s ear impression, the shell of the hearing assistance device or complimentary devices can be designed. The electronic ear impression models allow efficient and flexible electronic design manipulation. Efforts to design the internal features and accommodate internal devices of the hearing assistance device become less burdensome with the use of the electronic models. Computer manipulations of the three dimensional models allow designers to develop and visually review several configurations of internal structures of the shell in a short period of time. The electronic models also allow development and visual review of the design and placement of external features such that a more comfortable and beneficial hearing assistance device is produced. Additionally, the resulting electronic models and configurations are easily duplicated, in part, so as to quickly configure a user&#39;s complimentary hearing assistance device or, to create a library of hearing assistance device characteristics that are electronically portable and selectable when configuring future devices. A machine tool, or series of machine tools, produce physical representations of the hearing assistance device using software that generates the machine tool commands from processing the electronic models originating from the scanned ear impressions. A typical machine tool is a multi-axis, computer controlled machine. A machine tool will normally control a set of tooling to remove material from a blank piece of stock or a cast or mold. Some machine tools remove the material using various bits and routers. Other machine tools use lasers to shape the object of manufacture. Some machine tool use multiple forms of tooling including bits, routers and lasers through the use of tool changers. Modeling of the user&#39;s ear begins with creating an impression of the ear canal. There are several methods of producing an ear impression that are well known in the art. The exterior contours of the resulting impression define the internal contours of a patient&#39;s ear canal. Traditionally, the impression would be used to make a mold and the mold would be used to make a shell for hearing assistance device of the patient. Such a process would normally take several weeks from the time the impression was made until a mold was produced. The subject matter of the present document provides apparatus and methods for using a single laser displacement sensor where a laser source and line scan camera are packaged in a small mountable format. In various embodiments, the Acuity AccuRange 200™ is an example of a laser displacement sensor according to the present subject matter. 
     FIG. 1A  illustrates one embodiment of a spindle axis  100  according to the present subject matter. The spindle axis is used to hold the ear impression and rotate it while the ear impression is scanned for modeling. The illustrate embodiment shows an encoder device  101 , a motor  102 , and a coupling  103  connecting the motor to the shaft  104  of the mounting device. The mounting device is hidden from view in  FIG. 1A  by superimposed images of a test object  105  and an ear impression  106  mounted on the spindle axis  100 .  FIG. 1B  illustrates the two spindle axes  100 A,  100 B assembled as part of a spindle pitch axis  110  according to one embodiment of the present subject matter. The use of two spindles allows the simultaneous scan of a pair of ear impressions  106 A,  106 B. In various embodiments, the tilt axis assembly allows the axis of rotation of the spindles and, therefore, the orientation of the ear impressions to be adjusted with respect to the scanner such that difficult contours of a particular impression may be more accurately scanned. In various embodiments, the motor  102  is a servo motor. In various embodiments, the motor  102  is a stepper motor. 
     FIG. 2  illustrates a linear axis  211  according to one embodiment of the present subject matter. The linear axis supports and moves the scanner sensor used to scan the ear impression mounted on the spindle axis. The illustration shows an encoding device  201 , a motor  202 , a coupler  203  providing a connection between the motor  202  and a lead screw  207 .  FIG. 2  also shows a linear carriage  208  incorporating a nut threaded upon the lead screw  207 . In addition to the lead screw  207 , the carriage&#39;s linear motion and primary support is provided by a guide assembly  209 . In various embodiments, bearings incorporated into the carriage  208  and the nut provide smooth and low friction motion of the carriage  208  within the guide assembly  209  and along the lead screw  207 . 
     FIG. 3  illustrates a latitudinal axis assembly  312  according to one embodiment of the present subject matter. The latitudinal axis assembly is mounted to and moved by the linear axis ( FIG. 2 ) according to commands of a controller. The embodiment of  FIG. 3  shows two laser dimensional sensors  313 A,  313 B, a linear rail  314 , a carriage  315  and a linear motor including a magnet tube  316  and corresponding motor winding module  317 . The latitudinal axis assembly  312  allows positioning of one or more laser dimensional scanners along a path substantially perpendicular to the axis of rotation of the spindle axes and substantially perpendicular to the path of motion defined by the linear axis. When fully assembled, the laser beam of each laser dimensional sensor is directed toward an object mounted on the corresponding spindle axis as depicted in the embodiment of  FIG. 6 . 
     FIG. 4  illustrates a latitudinal axis assembly mounted to a linear axis according to one embodiment of the current subject matter. The illustration shows an encoding device  401 , a motor  402 , a lead screw  407 , a guide assembly  409 , two laser dimensional sensors  413 A,  413 B, a linear rail  414 , carriage  415  and a linear motor including a magnet tube  416  and corresponding motor winding module  417 . 
     FIG. 5  illustrates a frame and assorted control components according to one embodiment of the present subject matter. The illustration includes the main base plate  518 , the linear axis base plate assembly  519  and the side plates  520  for the supporting the pitch axis. With respect to the pitch axis side plates,  FIG. 5  includes the pitch axis motor  521  attached to one side plate  520  and a pitch axis bearing and housing  522  attached to the other side plate  520 . 
     FIG. 6  illustrates an embodiment of an apparatus adapted to scan and electronically model ear impressions according to the present subject matter. The illustrated apparatus is adapted to scan and model up to two ear impressions simultaneously. The apparatus includes a main base plate  618 , a pitch axis  610  with two spindle axes supported by two side plates  620 , and a latitudinal axis  612  with two laser dimensional sensors  613 A,  613 B. In  FIG. 6 , an ear impression  606  and a test object  605  are shown superimposed on each other and mounted to each of the spindles. The latitudinal axis is mounted on a linear axis. The linear axis includes a linear axis guide assembly  609  and a lead screw  607 . The linear axis is mounted to a linear axis base plate assembly  619 . 
   In general, a three dimensional model of an ear impression is completed by mounting an ear impression to the apparatus and allowing the sensor to scan and the entire surface of the impression. According to the present subject matter, both the impression and the scanner are moved under the direction of a controller, such that the orientation of the impression with respect to the scanner can facilitate scanning sample points over the entire surface of the impression. A sample point is obtained by recording the position of each axis of the apparatus as well as the dimension communicated from laser dimension sensor. The laser dimension sensor measures the distance of a reflected point of laser light from a reference point associated with the sensor. The reference point is determined during calibration and is further referenced to a fixed point relative to the axes. As each dimension is communicated to the controller, the controller in turn captures the dimension of the rotary impression mount axis and the linear axis. The combined measurements allow precise determination of the position of the reflected point of laser energy within a three dimensional frame of reference. 
   In various embodiments, the apparatus includes a linear axis, one spindle axis and one scanner from which measurement data is collected. In such an embodiment, three measurements, one from each of the above devices, allow determination of a point, within three dimensional space, on the surface of the impression with respect to a point of reference. The accumulation of all the measurements collected in a full scan, provide a point cloud or three dimensional model of the ear impression surface. Embodiments with additional axes are capable of modeling more complex surface features of an impression such as crevices and features blocked by appendages of the impression, such as the portion of the impression corresponding to the most inner portion of an ear canal. The point cloud data is processed by at least one software application for visual display and production of a shell for a hearing assistance device housing. 
     FIG. 7  illustrates one embodiment of a method  751  of generating digitized models of two ear impressions. Prior to scanning the first ear impression, the apparatus must be calibrated to insure that collected measurement axis data can be processed to produce accurate position data representing detected points on the surface of an ear impression mounted and moved by the rotary ear impression axis. Manufacturing of the frame and assorted mounted fixtures according to a design will provide a rough calibration provided the design dimensions are correct and have been adhered to during assembly of the apparatus. 
   Prior to scanning the ear impressions, initialization of the axes  752  is performed to establish a point of reference for the system, subsequent measurements and captured axis data. In various embodiments, the linear and rotary impression mount axes, or spindle axes, include incremental encoding devices to provide precise feedback of each axes&#39; movement. Prior to initialization, the encoding devices do not provide predictable indication of the location of the axes as the initial values of the controller counters associated with each axis are typically not referenced to any reference point associated with each axis. Once initialized, the value of the axes incremental control counters provide an offset from a known reference point in a reference frame common to the entire system based on the system&#39;s prior calibration. Incremental devices do not retain reference information, therefore, initialization will need to be completed after power has been removed and re-established to either the encoder or the controller to assure an accurate model results from subsequently scanned ear impressions. 
   In various embodiments, an axis uses an absolute encoder. Embodiments with an absolute encoder and corresponding controls, including absolute encoding devices such as an absolute resolver or absolute encoder. Initialization is required only after an absolute encoding device is initially installed onto the axis. In embodiments with absolute encoding devices, the operation of the absolute encoding device allows automatic initialization of an axis without movement of the axis, even after power is removed and re-established from the device or the control. 
   In the illustrated method, the ear impressions are mounted to the spindle axes  753  after the axes are initialized. In various embodiments, the ear impressions are mounted to the spindle axes prior to the initialization of the axes. 
   In various embodiments, after initialization of the axes, calibration may be verified  754  and, if needed, adjusted to compensate for changes, for example, from wear of bearings and dimensional changes resulting from the environment, such as temperature. In various embodiments, verification includes mounting an object of known dimension on each spindle axis and scanning a model of the object. The scanned model is then compared to the model&#39;s verified dimensions. Calibration parameters of the system are adjusted such that the scanned model fits the model of the verified object. In various embodiments, the verification process includes scanning verified objects specially made such that each axis or device, such as the laser dimension sensor, may be verified individually over the full range of each axes&#39; motion. This type of verification allows precise calibration, for example, of the straightness of the linear axis over that axis&#39; full travel, the radial play of the spindle bearings, as well as, the alignment of the linear axis with the axis of rotation of the spindles. If the verification process can not rectify the calibration of these or other calibration parameters, the system raises an alert such that inspection and physical adjustment of the system can be performed. The verification measurements will be used with a second, future set of measurements to assist in deriving the final point cloud of each ear impression. 
   After the system is verified, a scan of an ear impression begins. The controller triggers the spindle axes to accelerate and begin rotating at a predetermined and constant speed  755 . In various embodiments, when the rotary axes reach a steady state speed at or near the predetermined speed, the controller triggers the laser dimension sensors to communicate measurement data. The data is communicated to the controller at a rate of up to 1250 measurements per second using various communication protocols and hardware. In various embodiments, the communication uses a serial network, such as RS232 or RS422. Other communication formats may also be used, for example, a direct analog input, Ethernet, ControlNet, DeviceNet, or ProfiBus. In various embodiments, the recording of measurements includes simultaneously capturing the positions of both the linear axis and the rotary impression mount axes. The measurement and positions are recorded for future processing. 
   The actual scan of the ear impressions begin with positioning each axis such that the narrowly localized area of laser light from each sensor  757  is directed at the ear impression, usually at or near one extreme of the impression with respect to the linear axis  756 . 
   In various embodiments, after measurements have been recorded for at least one revolution of each impression  758 , the controller moves the linear axis incrementally toward the other extreme of the impression  760 , stops the linear axis, and records measurements and positions for another rotation of the impression. This pattern of, measure for a rotation of each impression, move linear axis and repeat, continues until the entire impression is scanned  761 . The rotational speed of the spindle axes is maintained throughout the scanning process  759 . In one embodiment of the present subject matter, the controller begins a continuous movement of the linear axis toward the other extreme of the impression after the initial scan of the first revolution of the impression is complete. As the linear axis travels toward the other extreme of the impression. the controller continuously captures measured data and corresponding position information until the entire impression is scanned. Once the actual scan of the ear impression is complete, the system makes a second scan of the calibration device  762  for use in deriving the point cloud and correcting for rotational orientation errors in the collected data. 
   In various embodiments, the system collects two arrays of data throughout the scanning process. The data arrays include an array of position measurements and corresponding timestamps of the measurements, and an array of laser measurements and corresponding timestamps of the laser measurements. In various embodiments, a scanner communicates  1250  measurements per second. Using such a scanner, a 14,000 point “point cloud” is derived from as many as 75,000 measurements collected in each of the arrays. Upon derivation of the point cloud, a surface is electronically fitted to the point cloud and is built into a electronically storable Stereolithography Tessellation Language (STL) computer file  763 . In various embodiments, the measurements, derivation and surface fitting is completed in less than 180 seconds. In various embodiments, the finished model is accurate to within 0.001 inch of the actual impression. 
   This application is intended to cover adaptations or variations of the present subject matter. It is to be understood that the above description is intended to be illustrative, and not restrictive. The scope of the present subject matter should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.