AUTOMATED OPTICAL COMPARATOR

• US 3,737,856 A
• Filed: 03/06/1970
• Issued: 06/05/1973
• Est. Priority Date: 03/06/1970
• Status: Expired due to Term

• Current Assignee: John C. Holme, Raymond A. Robertson, Stanley Lehrer
• Original Assignee: John C. Holme, Raymond A. Robertson, Stanley Lehrer
• Inventors: Lehrer, Stanley, Robertson, Raymond A., Holme, John C.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Boudreau, Leo H.
• Application Number:
  US05/017,054
• Time in Patent Office: 1,187 Days
• Field of Search: 340/146.3 250/219WD,22MX,22M,222R,223R,223B 356/141,154,156-160,163-170,206,240
• US Class Current: 382/214
• CPC Class Codes: G01B 11/245 using a plurality of fixed, simultaneously operating transducers G01B11/2408 - G01B11/2425, G01B11/255 take precedence

Abstract

Apparatus for automating the determination of the dimensional measurements of an object having its silhouette displayed on an optical comparator and providing a digital representation of those measurements. The apparatus utilizes a plurality of photodetector arrays, each of which includes a plurality of photodetectors, which operate in circuit with electronic storage and comparison means to convert the output from the photocells into a digital indication of the deviation of the dimensions of the object from the dimensions of a reference part. In one embodiment, a pair of photodetector arrays are adjustably secured to a translucent viewscreen on the optical comparator. The arrays sense the position of the shadow edge of the image of the object and provide signals which indicate the location of that edge. A signal corresponding to the output from the photodetector arrays which was produced in response to the silhouette of a standard object is stored within a standard register. A signal corresponding to the output generated by the photodetector arrays for the dimensions of the object to be measured is compared with the signals stored in the standard register to provide a digital readout which represents the deviation of the object from the standard. Each of the photodetector arrays includes a plurality of photocells which are secured in a linear spaced relationship within an array housing. The housing is slidably secured to a track member attached to one side of the viewscreen. Thus, the array may be adjusted with respect to the silhouette of the object displayed on the viewscreen to accommodate a wide range of dimensions. In other embodiments, a plurality of arrays are secured to the viewscreen for multi-dimensional or profile measurement. Circuit means are also provided for indicating when the boundary of the object is outside of the limits of the array. Means are also disclosed for electronically focusing and for automatically positioning the array module.

Claims

1. An optical apparatus for automating the determination of the deviation from a stored reference standard of the dimensions of an object having its magnified silhouette displayed at an image plane on a screen member and providing an output signal representative of said deviation with an accuracy at least on the order of 1 X 10 4, comprising the combination of:

first means including said screen member for defining an image plane for receiving the projected silhouette of an object to be measured, said first means receiving said magnified silhouette of said object to enhance the accuracy of said determination, a plurality of linear arrays of radiation-sensitive detectors, each of said linear arrays comprising a plurality of substantially aligned, closely adjacent, radiation-sensitive detectors spaced apart on the order of about 0.004 inches for providing a signal representative of locations of the silhouette of said object as a function of the impingement of radiation on each of said arrays of detectors, said detectors being located at said image plane, second means for securing each of said plurality of arrays of detectors substantially in said image plane; and

circuit means, including memory means for storing a digital reference signal representative of the reference standard of the dimensions of said object and comparator means for comparing a digital first signal from said plurality of detectors representing the silhouette of said object with said digital reference signal, said circuit means being in operative association with each of said detectors for providing a digital signal which represents a digital comparison of said first signal produced by said plurality of detectors in response to the projection of said silhouette with said reference signal stored in said storage means.

2. The apparatus as defined in claim 1 wherein said first means includes an optical comparator of the type comprising a source of light and means for interposing an object with respect to said source of light so that a magnified image of said object is focused upon said image plane and wherein said detectors are photodetectors.

3. The apparatus as defined in claim 2 wherein said screen member is translucent.

4. The apparatus as defined in claim 3 wherein said second means includes a plurality of housing members, means for securing an array of a plurality of said photodetectors in each of said housing members, and means for securing each of said housing members to said screen member in such a manner that said photodetectors are located substantially in said image plane and are capable of determining the edge of said silhouette.

5. The apparatus as defined in claim 4 wherein said screen member defines at least one opening in register with at least one of said housing members so that portions of the edge of said silhouette are projected upon said photodetectors without passing through said screen member.

6. The apparatus as defined in claim 4 wherein said first means is further characterized in that each of said plurality of housing members is releasably secured to said screen member.

7. The apparatus as defined in claim 4 wherein said first means includes a body member and means for securing said body member to said screen member, said body member defining a recess for receiVing each of said plurality of housing members.

8. The apparatus as defined in claim 7 wherein said body member further defines a slot in communication with said recess and securing means having a portion thereof located in said slot for releasably securing said housing member in said recess.

9. The apparatus as defined in claim 1 further including means for adjustably securing each of the photodetector arrays at about said image plane.

10. The apparatus as defined in claim 9 wherein said securing means comprises a member defining a channel for receiving each of said photodetector arrays and further including means for permitting the adjustment of each of the photodetector arrays within said channel.

11. The apparatus as defined in claim 10 wherein each of said photodetector arrays includes a threaded recess and said apparatus further includes a thumb screw having a threaded projecting member capable of coacting with said threaded recess, and said member defines an opening communicating with said channel for receiving said projecting member so that each of said arrays may be secured within said channel by the cooperation of said securing member and said projecting member.

12. The apparatus as defined in claim 11 wherein said screen member defines an opening which is substantially in register with said channel.

13. The apparatus as defined in claim 1 wherein each of the photodetectors arrays is arranged substantially in a planar configuration and wherein said screen member defines said image plane, the cooperation of said array and said screen member being such that the planar array of photodetectors is arranged substantially in the image plane of said screen member.

14. The apparatus as defined in claim 1 wherein each of said arrays is arranged to permit the measurement of the deviation of an irregular profile of an object from a reference standard representing said irregular profile.

15. The apparatus as defined in claim 1 further including a plurality of photodetector arrays which are fixably secured to said screen member, each of said plurality of arrays further including a plurality of photodetectors in a linear array, said plurality of arrays being arranged to permit multidimensional measurement of an object.

16. In a guaging apparatus, the combination of:

a plurality of arrays, each comprising a plurality of linearly spaced, closely adjacent photodetectors for providing a first plurality of signals representing the location of a projected magnified silhouette of an object, said photodetectors being spaced apart on the order of 0.004 inches, means for receiving said first plurality of signals and providing a first digital signal representative thereof, said first digital signal being represented by a first number of counts, means for storing a second digital signal representative of the dimensions of a standard object in a first register, said second signal being represented by a second number of counts, means for storing said first signal representative of the dimensions of an object to be measured in a second register, wherein said means for storing said signals includes multiplexing means in circuit with each of said arrays of photodetectors for converting the outputs from said plurality of arrays of photodetectors from parallel to serial form, a source of clock pulses, and means in circuit with said source of clock pulses and said multiplexing means for controlling the readout sequence from each of said plurality of arrays of photodetectors, means for comparing said first signal stored in said second register and said second signal stored in said first register to provide a representation of the quantitative difference therebetween, means for introducing a number of counts in the second register to make the number of counts stored in each of said first and second registers equal, and means in circuit with said comparing means for providing a digital readout of the quantitative difference betwEen said first signal and said second signal, the last named means further including control means for providing counts to a display output which corresponds to the number of counts added when the number of counts in said second register is less than the number of counts in said first register to make said register equal, and which corresponds to the number of counts generated which are in excess of the number of counts in said first register when said second signal generates a count greater than the count in said first register.

17. The circuit as defined in claim 16 further including means for electronically focusing the image projected on said plurality of arrays of photodetectors.

18. The circuit as defined in claim 16 further including means for indicating that the edge of the projected image of the object to be measured is outside of the lateral extent of at least one array of photodetectors.

19. The circuit as defined in claim 16 further including means for interrupting the digital readout when the outline of said object does not intersect at least one of the arrays of photodetectors.