RELATIVE BACK FOCUS MONITORING METHOD AND APPARATUS

• US 3,652,164 A
• Filed: 05/01/1970
• Issued: 03/28/1972
• Est. Priority Date: 05/01/1970
• Status: Expired due to Term

• Current Assignee: Ernest W. Long, Faramarz Faramarzpour
• Original Assignee: Ernest W. Long, Faramarz Faramarzpour
• Inventors: Faramarzpour, Faramarz, Long, Ernest W.
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): Clark, Conrad
• Application Number:
  US05/033,612
• Time in Patent Office: 697 Days
• Field of Search: 356/125 250/204
• US Class Current: 356/125
• CPC Class Codes: G01M 11/00 Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
• CPC Class Codes: G01N 21/956 Inspecting patterns on the surface of objects contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G03B 21/32 Details specially adapted for motion-picture projection with film moving continuously through the gate G03B41/02
• CPC Class Codes: G03C 7/14 Additive processes using lenticular screens; Materials therefor; Preparing or processing such materials

Abstract

The subject invention generally provides a method and apparatus for determining the relative back focus of each of a plurality of lenticules or the like and, more particularly, provides for the determination of the relative back focus of each of a plurality of lenticules comprising a lenticular film which is disposed along one surface of a supporting web. The relative back focus of each lenticule or the like may be generally defined as the distance from the focus of said lenticule or the like to a reference which, in the case of a web supported lenticular film, is the surface of the web opposite the lenticular film. Briefly, collimated light is passed through each of the lenticules and is focused by a moving microscopic objective which is positioned outward of the surface of the web opposite the lenticular film. The objective is moved toward and away from the web so as to vary the focal plane of the image received from one of the lenticules. When the image of said one lenticule is focused at a predetermined point, it is detected by a photo-detector which provides an electrical output pulse indicative thereof. Means are provided for determining the position of the microscopic objective at the time of said pulse. A source of light of a wavelength different from that of said collimated light is provided and transmits light, through said microscopic objective to the non-lenticulated side of said web such that it is reflected therefrom. This reflected light is brought to focus remote from said web by said microscopic objective. The microscopic objective is moved with respect to the web until said reflected light is brought to said same predetermined focus as said collimated light. When the reflected light is brought to said predetermined focus, it is detected by a second photo-detector which will provide an electrical output pulse in response thereto. The position of the microscopic objective is determined at the time of the electrical output pulse responsive to said reflected light and the distance traversed by said microscopic objective and, hence, the relative back-focus of the particular lenticule being monitored, may be readily determined.

Claims

1. Apparatus for monitoring a plurality of serially arranged lenticulations, including:

a source of light for illuminating each of said lenticulations and being focused thereby;

lens means having an optical axis and spaced therealong from said lenticulations and a reference for sequentially imaging the focus of said light by each of said lenticulations to positions along said optical axis;

means for cyclically varying the distance between said lens means and such lenticulations during said imaging;

photoresponsive means for detecting the imaged foci of said light by said lenticulations and for generating a signal in response thereto; and

means responsive to said signal for determining the distances between said reference and the foci of said lenticulations.

2. Apparatus for monitoring a plurality of lenticules or the like, including:

a source of light for illuminating each of said lenticules or the like and being focused thereby means for detecting the focus of light by each of said lenticules or the like, including lens means having an optical axis dispOsed in cyclically variable spaced relation along said optical axis with respect to a reference; and

means for detecting and comparing the relative positions along said optical axis of said lens means and said reference and determining the distance therebetween in response to each sequentially detected focus to thereby determine the distance between each said focus and said reference.

3. The invention as related in claim 2, wherein said reference is at least partially reflective to at least one wavelength of light and further including a second source of light for illuminating said reference whereby light will be reflected from said reference;

said lens means being adapted to receive at least a portion of the light reflected from said reference to form an image thereof at a first focus and sequentially so positioned with respect to each of said lenticules or the like so as to form an image of the light focused by each lenticule or the like thereby at a second focus;

whereby movement of said lens means along said optical axis will alternately effect the movement of said first and second foci to a preselected position.

4. The invention of claim 3, further including first detecting means for detecting coincidence between said first focus and said preselected position and second detecting means for determining coincidence between said second focus and said preselected position.

5. The invention of claim 4, wherein said detecting and comparing means includes means connected to said lens means and to said first and second detecting means for determining the position of said lens means upon effecting coincidence between said first focus and said preselected position and between said second focus and said preselected position;

and means for detecting the distance between the positions of said lens means so determined.

6. The invention as recited in claim 5, further including means positioned with respect to said lens means so as to pass to said first and second detecting means a portion of the light focused by said lens means;

said transmitted portion being a maximum with respect to the image of said reference when said second focus is coincident with said preselected position and with respect to the image of said scanned lenticule or the like when said first focus is coincident with said preselected position.

7. The invention as related in claim 6, wherein said means for transmitting a portion of the light focused by said lens means comprises an aperture plate disposed transversely the optical axis of said lens means and located at said preselected position.

8. The invention as set forth in claim 7, wherein said first-mentioned source of light provides collimated light of one wavelength and said second source of light provides non-collimated light of a different wavelength.

9. The invention as set forth in claim 8, additionally including:

means for receiving light from said second source of light and reflecting at least a portion thereof through said lens means to said reference and for receiving light focused by said lens means and transmitting at least a portion thereof through said aperture plate; and

means for receiving light transmitted through said aperture plate and reflecting a portion thereof to one of said first and second detectors and transmitting a portion thereof to the other of said first and second detectors.

10. The invention described in claim 9, additionally including means for transmitting light of only one of said wavelengths to one of said first and second detectors and for transmitting only light of the other of said wavelengths to the other of said first and second detectors.

11. In combination with a film comprising a plurality of lenticules or the like disposed along one surface of a supporting web, apparatus for detecting the relative back-focus of at least a preselected one of said lenticules or the like, including:

means for transmitting light of one wavelength through said preselected lenticule or the like;

a lens suitably positioned with respect to the surface of the web opposite said film for focusing said transmitted light and movable toward and away from said web so as to vary the focus of the image received from said lenticule or the like;

means for detecting said image when it is focused at a predetermined plane;

means for determining the position of said lens when said image is focused at said predetermined plane;

a source of light of a wavelength different from that of said first-mentioned source for transmitting light through said lens to one surface of said web such that light is reflected therefrom and brought to a variable focus by said lens;

means for detecting said reflected light when it is focused at said predetermined plane by said lens;

means for determining the position of said lens when said reflected light is focused at said predetermined plane; and

means for comparing the position of said lens when said light of one wavelength is focused at said predetermined plane with that of said lens when said light of said different wavelength is focused at said predetermined plane and determining the relative back-focus of said lenticule or the like therefrom.

12. The invention of claim 11, further including means for detecting only the light of said one wavelength when it is focused at said predetermined plane and means for detecting only light of said different wavelength when it is focused at said predetermined plane.

13. The invention as set forth in claim 12, wherein said position determining means includes means connected to said lens for continually monitoring the position thereof;

and means connected to said detecting means and said monitoring means for sampling the output of said monitoring means in response to actuation of each of said detecting means.

14. The invention as stated in claim 13, wherein said monitoring means comprises a linear voltage/distance transducer and said sampling means comprises a pair of sample and hold networks each connected to said linear voltage/distance transducer and responsive to the actuation of one of said detecting means so as to sample the output of said linear voltage/distance transducer in response to such actuation and provide a DC-level output signal indicative of the position of said lens.

15. The invention as set forth in claim 14, additionally including means for sinusoidally driving said lens toward and away from the non-lenticulated surface of said web;

means connected to said sample and hold networks for passing only such portions of their respective outputs as are temporarily coincident; and

means for determining the difference between said temporarily coincident outputs and providing an output signal indicative of the relative back-focus of said preselected lenticule or the like.

16. Apparatus for determining the relative back-focus of the lenticules or the like comprising a layer mounted on one surface of a supporting web the other surface of which is at least partially reflective to light, including:

a source of illumination of a first wavelength suitably disposed for illuminating at least a preselected one of the lenticules or the like with light which is focused by at least one of said lenticules or the like to form an image of said source;

a lens positioned with respect to said web for receiving the image of said source and bringing it to a predetermined focus;

means connected to said lens for cyclically moving said lens toward and away from said web;

means connected to said lens for continually monitoring the position of said lens and providing an output signal linearly responsive thereto;

a source of light of a second wavelength;

a first beam splitter for reflecting light of said second wavelength through said lens to the non-layered surface of said web from whence it is reflected back to said lens which will bring the image of said second source to said predetermined focus at some point in its movement With respect to said web;

said first beam splitter serving to pass at least a portion of the light of said first wavelength and said second wavelength focused by said lens;

an aperture plate positioned at said predetermined focus and serving to pass a portion of said light of said first wavelength and said second wavelength which is focused thereat;

a second beam splitter for reflecting a portion of the light focused at said aperture plate in one direction and transmitting a portion of said light focused at said aperture plate in another direction;

a first photo-detector for receiving a portion of said illumination reflected by said second beam splitter which is of one of said first and second wavelengths and providing an output signal when light of its received wavelength is focused by said lens at said predetermined focus;

a second photo-detector for receiving a portion of said light transmitted by said second beam splitter corresponding to the other of said first and second wavelengths and providing an output signal when light of the other of said first and second wavelengths is focused by said lens at said predetermined focus; and

means connected to said monitoring means for comparing the output signals therefrom at the times of the respective output signals from said first and second photo-detectors and generating a signal corresponding to the distance between the focus of said preselected lenticule or the like and the non-lenticulated surface of said web.

17. A method for sequentially measuring the distance between the focus of each of plural serially arranged lenticules or the like and a predetermined reference comprising the steps of:

illuminating each said lenticule or the like with light such that said light will be brought to a first focus by said lenticule or the like;

sequentially imaging each such first focus to a predetermined second focus by cyclically moving a lens toward and away from each said lenticule or the like in turn;

determining the position of said lens when each said first focus is imaged at said predetermined second focus;

illuminating said reference and reflecting light therefrom;

cyclically moving said lens with respect to said lenticule or the like and said reference so as to bring said reflected light to said predetermined second focus;

determining the position of said lens when said reflected light is brought to said predetermined second focus; and

sequentially determining the change in position of said lens in imaging each said first focus to said predetermined second focus and in bringing said reflected light to said predetermined second focus.

18. The method of claim 17, wherein said lenticule or the like is illuminated with light of one wavelength and where light of another wavelength is reflected from said reference.

19. Apparatus for monitoring a plurality of optical focusing means, including:

a source of light for illuminating each of said focusing means and being focused thereby;

lens means having an optical axis and disposed in cyclically variable spaced relation with respect to a reference along said axis for sequentially scanning said plurality of focusing means and sequentially imaging the focus of said light by each said focusing means to a predetermined position;

first photoresponsive means for detecting the presence of each said image at said predetermined position;

means for illuminating said reference and imaging same at said predetermined position;

second photoresponsive means for detecting the presence of said image of said reference at said predetermined position; and

means for comparing the relative positions of said lens means and said reference and determining the distance therebetween in response to signals from said first and second photoresponsive means, respectively, to thereby determine the distance between the focus of said light of each said optical focusing means and said reference.

20. The iNvention as described in claim 19, wherein each said focusing means is illuminated with light of one wavelength and light of a different wavelength is reflected from said reference;

and further including means for allowing light of only one of said wavelengths to reach a predetermined one of said photoresponsive means and only light of the other of said wavelengths to reach the other of said photoresponsive means.

21. The invention as recited in claim 20, further including means positioned with respect to said lens means so as to transmit to said first and second photoresponsive means a portion of the light focused by said lens means;

said transmitted portion being a maximum with respect to the image of said reference when the focus of said reference image is coincident with said predetermined position and with respect to the image of the focus of each focusing means when each said focusing means'"'"''"'"' image is coincident with said predetermined position.

22. The invention as described in claim 1, further including means positioned with respect to said lens means so as to transmit to said photoresponsive means a portion of the light imaged by said lens means;

said portion being a maximum when said imaged light is focused at a predetermined position.