Patent US3743427A successfully refreshed from Google Patents.
US3743427A
Expired / Lapsed
US
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Modulation transfer function measurement system and method
Assignee: WEISER ROBODYNE CORP
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Filing: 1971-06-29
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Granted: 1973-07-03
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Expires: 1991-06-29
Abstract
Abstract A constant speed rotating drum having a plurality of circumferentially spaced bar patterns of different discrete spatial frequencies is employed to measure the modulation transfer function (MTF) of a lens or other optical unit under test. A slit image input is degraded by the unit under test which thereby produces a spread function in its output plane. The spread function is scanned by a bar pattern and detected by a photosensor to provide an electrical square wave signal which is distorted to a degree determined by the spread function. Each bar pattern generates a different square wave frequency which is passed by a respective narrow bandpass filter tuned to its fundamental frequency. Each filter is gated on only when its associated bar pattern is rendered operative to scan the spread function. The amplitude of the passed fundamental frequency is then detected as a measure of the MTF. Scanning by the bar pattern may be at either the input or output of the unit under test.
Inventors
- 👤 S Weiser
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 20:10
CPC Classifications
G; G01; G01M; G01M11/00; G01M11/02; G01M11/0292
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
230 words
A device for determining the image-forming quality of an optical system by employing bar patterns of different spatial frequencies, said device comprising in combination: a drum rotating at constant speed; partially transparent bar patterns of different spatial frequencies mounted in spaced relation along the circumference of said drum; means for projecting an image of a slit by the optical system whose image-forming quality is to be determined onto and through said rotating drum so that said bar patterns perform a scanning of said slit image and produce optical signals; a photoelectric receiver energized by said optical signals produced by the scanning operation for converting said optical signals into electrical signals; means for amplifying said electric signals; a plurality of signal paths connected in parallel to receive said electrical signals, each signal path including a narrow band electrical filter tuned to a respective temporal frequency which is equal to the spatial frequency of a respective bar pattern multiplied by a factor determined by the speed of said drum; synchronized signal interruption means disposed in each signal path for permitting signal flow through only one signal path at a time; means for detecting output signals from said signal paths to provide voltages which are proportional to the modulation functions of said optical system; means for displaying the relative values of said voltages for obtaining a relative comparison of said modulation transfer function.
Claim 2
Independent Claim
230 words
A device for determining the image-forming quality of an optical system by employing bar patterns of different spatial frequencies, said device comprising in combination: a drum rotating at constant speed; partially transparent bar patterns of different spatial frequencies mounted in spaced relation along the circumference of said drum; means for projecting an image of a slit by the optical system whose image-forming quality is to be determined onto and through said rotating drum so that said bar patterns perform a scanning of said slit image and produce optical signals; a photoelectric receiver energized by said optical signals produced by the scanning operation for converting said optical signals into electrical signals; means for amplifying said electric signals; a plurality of signal paths connected in parallel to receive said electrical signals, each signal path including a narrow band electrical filter tuned to a respective temporal frequency which is equal to the spatial frequency of a respective bar pattern multiplied by a factor determined by the speed of said drum; synchronized signal interruption means disposed in each signal path for permitting signal flow through only one signal path at a time; means for detecting output signals from said signal paths to provide voltages which are proportional to the modulation functions of said optical system; means for displaying the relative values of said voltages for obtaining a relative comparison of said modulation transfer function.
Claim 3
Independent Claim
246 words
A system for measuring the modulation transfer function of an optical unit under test, said system comprising: means for directing a slit of light along an optical path extending through said unit under test to provide an image of said slit formed by said unit; means for modulating said image of said slit of light by passing a series of bar patterns at constant speed through said optical path, each bar pattern comprising a series of alternating opaque and transparent bars spaced with a discrete spatial frequency, each bar pattern having a different spatial frequency; photosensitive means at the end of said path for receiving the modulated image of said slit of light and converting it into electrical signals of amplitude proportional to the intensity of the received light; a plurality of electrical signal paths connected in parallel to receive said electrical signals, one signal path for each of said bar patterns, each signal path including a bandpass filter, each filter being tuned to a different frequency equal to the modulation frequency produced by a corresponding bar pattern moving across said optical path at said constant speed; synchronized signal interruption means disposed in each signal path for permittiNg signal flow through only one signal path at a time; and means for detecting the signal passed by the selected filter to provide a measure of the modulation transfer function of the unit under test at the spatial frequency of the bar pattern corresponding to the selected filter.
Claim 4
Independent Claim
246 words
A system for measuring the modulation transfer function of an optical unit under test, said system comprising: means for directing a slit of light along an optical path extending through said unit under test to provide an image of said slit formed by said unit; means for modulating said image of said slit of light by passing a series of bar patterns at constant speed through said optical path, each bar pattern comprising a series of alternating opaque and transparent bars spaced with a discrete spatial frequency, each bar pattern having a different spatial frequency; photosensitive means at the end of said path for receiving the modulated image of said slit of light and converting it into electrical signals of amplitude proportional to the intensity of the received light; a plurality of electrical signal paths connected in parallel to receive said electrical signals, one signal path for each of said bar patterns, each signal path including a bandpass filter, each filter being tuned to a different frequency equal to the modulation frequency produced by a corresponding bar pattern moving across said optical path at said constant speed; synchronized signal interruption means disposed in each signal path for permittiNg signal flow through only one signal path at a time; and means for detecting the signal passed by the selected filter to provide a measure of the modulation transfer function of the unit under test at the spatial frequency of the bar pattern corresponding to the selected filter.
Claim 5
Dependent Claim
47 words
The system according to claim 2 wherein said bar patterns are disposed circumferentially about a drum rotating at constant speed, each bar pattern being spaced from its preceding and succeeding bar pattern by an opaque region considerably wider than the bars in any of said bar patterns.
Claim 6
Dependent Claim
33 words
The system according to claim 3 wherein said signal interruption means includes means for permitting signal flow through said only one signal path during at least one complete rotation period of said drum.
Claim 7
Dependent Claim
35 words
The system according to claim 4 wherein said signal interruption means includes means for automatically changing the one signal path through which signal is permitted to flow after each complete rotation period of said drum.
Claim 8
Dependent Claim
31 words
The system according to claim 3 wherein said signal interruption means includes manually actuable means for selecting one signal path to pass signal for multiple successive rotation periods of said drum.
Claim 9
Dependent Claim
46 words
The system according to claim 3 wherein said means for detecting includes: a storage circuit for storing the detected signal for measurement purposes; and means for clearing said storage circuit of its stored signal prior to the next passing of signal through a selected signal path.
Claim 10
Dependent Claim
83 words
The system according to claim 7 further comprising: means for counting rotations of said drum; means for automatically selecting successive signal paths to pass signal during successive rotations of said drum according to the rotation count; an x-y recorder; means for driving the y-input of said recorder with the detected peak of signal passed by the selected signal path; and means for driving the x-input of said recorder with a signal having an amplitude which is a predetermined function of the rotation count.
Claim 11
Dependent Claim
38 words
The system according to claim 8 wherein said predetermined function relates the rotation to the spatial frequency of the bar pattern corresponding to the selected signal path to provide a linear spatial frequency scale on said x-y recorder.
Claim 12
Dependent Claim
55 words
The system according to claim 3 further comprising calibration means for providing an absolute calibration of said system, said calibration means comprising means for terminating rotation of said drum and chopper means for alternately blocking and passing light along said optical path at a frequency equal to the tuned frequency of one of said filters.
Claim 13
Dependent Claim
51 words
The system according to claim 3 further comprising means for enabling both tangential and sagittal measurements of said modulation transfer function to be performed on said unit under test, said last mentioned means comprising means for rotating said slit of light and said drum each by 90* about said optical path.
Claim 14
Dependent Claim
33 words
The system according to claim 3 further comprising a microscope positioned in said optical path to permit viewing of the image of said slit of light as passed through said unit under test.
Claim 15
Dependent Claim
49 words
The system according to claim 3 wherein said means for directing a slit of light includes a rotatable slit member interposed in said optical path, said rotatable slit member including a vernier control for accurately controlling the rotational position of said slit of light relative to said optical path.
Claim 16
Independent Claim
207 words
A method for measuring the modulation transfer function of an optical unit under test, said method comprising: directing a slit of light along an optical path extending through said unit under test; modulating said slit of light by passing a series of spaced bar patterns at constant speed through said optical path, each bar pattern comprising a series of alternating opaque and transparent bars spaced with a discrete spatial frequency, each bar pattern having a different spatial frequency; recEiving the modulated slit of light and converting it into electrical signals of amplitude proportional to the intensity of the received light; passing said electrical signals to a plurality of signal paths connected in parallel, one signal path for each of said bar patterns, each signal path including a respective bandpass filter, each filter being tuned to a different frequency equal to the modulation frequency produced by its corresponding bar pattern moving across said optical path at said constant speed; selectively interrupting all but one selected signal path; and detecting the signal passed by the selected signal path to provide a measure of the modulation transfer function of the unit under test at the spatial frequency of the bar pattern corresponding to the filter in the selected signal path.
Claim 17
Independent Claim
207 words
A method for measuring the modulation transfer function of an optical unit under test, said method comprising: directing a slit of light along an optical path extending through said unit under test; modulating said slit of light by passing a series of spaced bar patterns at constant speed through said optical path, each bar pattern comprising a series of alternating opaque and transparent bars spaced with a discrete spatial frequency, each bar pattern having a different spatial frequency; recEiving the modulated slit of light and converting it into electrical signals of amplitude proportional to the intensity of the received light; passing said electrical signals to a plurality of signal paths connected in parallel, one signal path for each of said bar patterns, each signal path including a respective bandpass filter, each filter being tuned to a different frequency equal to the modulation frequency produced by its corresponding bar pattern moving across said optical path at said constant speed; selectively interrupting all but one selected signal path; and detecting the signal passed by the selected signal path to provide a measure of the modulation transfer function of the unit under test at the spatial frequency of the bar pattern corresponding to the filter in the selected signal path.
Claim 18
Dependent Claim
59 words
The method according to claim 14 wherein said bar patterns of different frequency are spaced along a continuous path arranged to pass through said optical path; and wherein said step of selectively interrupting includes the step of passing signal through only the selected signal path during a complete cycle of passage of said continuous path through said optical path.
Claim 19
Dependent Claim
27 words
The method according to claim 15 wherein the selected signal path is automatically changed for successive cycles of passage of said continuous path through said optical path.
Claim 20
Dependent Claim
30 words
The method according to claim 15 wherein the selected signal path is selected to pass signal for plural successive cycles of passage of said continuous path through said optical path.
Claim 21
Dependent Claim
28 words
The system according to claim 1 further comprising means for automatically changing the signal path through which signal flow is permitted during successive rotation cycle of said drum.
Claim 22
Dependent Claim
33 words
The system according to claim 1 wherein said signal interruption means is operative to limit signal flow to said only one signal path for at least a complete rotation cycle of said drum.
Claim 23
Dependent Claim
46 words
The system according to claim 1 wherein said means for detecting includes: a storage circuit for storing the detected signal for measurement purposes; and means for clearing said storage circuit of its stored signal prior to the next passing of signal through a selected signal path.
Claim 24
Dependent Claim
83 words
The system according to claim 20 further comprising: means for counting rotations of said drum; means for automatically selecting successive signal paths to pass signal during successive rotations of said drum according to the rotation count; an x-y recorder; means for driving the y-input of said recorder with the detected peak of signal passed by the selected signal path; and means for driving the x-input of said recorder with a signal having an amplitude which is a predetermined function of the rotation count.
Claim 25
Dependent Claim
49 words
The system according to claim 1 further comprising means for providing an absolute calibration of said system including chopper means, operable upon termination of drum rotation, for alternately blocking and passing light to said photoelectric receiver at a frequency equal to the tuned frequency of one of said filters.
Claim 26
Dependent Claim
22 words
The system according to claim 1 further comprising a microscope positioned to permit viewing of the image of the slit of light.
References Cited (Backward Citations)
US3438713A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-02 | 1977-01-01 | 1977-07-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-02 | 1981-01-01 | 1981-07-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-02 | 1985-01-01 | 1985-07-03 | $7700.00 | Window Closed / Lapsed |