US4027970A
Expired / Lapsed
US
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Method and apparatus for passive optical fusing and distance measurement
Assignee: Lockheed Martin Corp
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Filing: 1975-10-28
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Granted: 1977-06-07
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Expires: 1995-10-28
Abstract
Abstract Distance measurement is provided by an optical system which includes modulation detection apparatus for determining when the optics are a predetermined distance from an object. This is accomplished by detecting an in-focus condition in terms of the modulation content of a cross-correlated signal. When the device is used as a fuse, a fire control signal is initiated when the ordinance device carrying the fuse is at a predetermined distance from a target. The system includes a stationary cross-correlation grating set at an optimal single spatial frequency based on the resolution and more specifically the modulation transfer function of the optics used. The grating is located at the image plane of an optical imaging system and an optical wedge is mounted for rotation about optical axis of this system so that the image is circularly nutated in the plane of the cross-correlation grating. Light passing through the cross-correlation grating is directed to a detector whose output is then amplified, filtered and rectified to yield a signal proportional to the modulation content of the output signal from the detector, with 100 percent modulation indicating an in-focus condition. This signal is compared, in one embodiment, to the output of a second detector which establishes an adaptive threshold such that when this threshold is exceeded an alarm or fire control signal may be initiated. The threshold level corresponds to a modulation percentage indicative of an acceptable in-focus condition. The cross-correlation grating in a preferred embodiment takes on the form of a multi-apertured disc with the apertures arranged at the apices of a hexagonal pattern.
Inventors
- 👤 Victor A. Misek
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 22:43
CPC Classifications
F; F42; F42C; F42C13/00; F42C13/02; G; G01; G01C; G01C3/00; G01C3/32
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
136 words
A method for detecting when an object is at a predetermined distance from an optical system having predetermined modulation transfer functions at predetermined in-focus and out-of-focus image planes comprising: locating a member having opaque and transparent regions at the image plane of the optical system established by objects at said predetermined distance, with the transparent regions of the member defining a single spatial frequency equal to that at which the difference in amplitude between the in-focus modulation transfer function and the modulation transfer function corresponding to said out-of-focus image plane is substantially maximum, moving the image of the object across the member in a cyclic manner; and detecting percent modulation of the light which has passed through the member whereby a maximum modulation percentage indicates an in-focus condition when said object is at said predetermined distance.
Claim 2
Independent Claim
136 words
A method for detecting when an object is at a predetermined distance from an optical system having predetermined modulation transfer functions at predetermined in-focus and out-of-focus image planes comprising: locating a member having opaque and transparent regions at the image plane of the optical system established by objects at said predetermined distance, with the transparent regions of the member defining a single spatial frequency equal to that at which the difference in amplitude between the in-focus modulation transfer function and the modulation transfer function corresponding to said out-of-focus image plane is substantially maximum, moving the image of the object across the member in a cyclic manner; and detecting percent modulation of the light which has passed through the member whereby a maximum modulation percentage indicates an in-focus condition when said object is at said predetermined distance.
Claim 3
Dependent Claim
23 words
The method of claim 1 wherein said member is maintained stationary with respect to rotation about the optical axis of said optical system.
Claim 4
Dependent Claim
141 words
Apparatus for detecting when an object is at a predetermined range from an optical system comprising: an imaging system having an optical axis, an in-focus modulation transfer function and a modulation transfer function corresponding to the image plane offset for a predetermined range accuracy, a grating having transparent regions defining a single spatial frequency equal to that at which the difference in amplitude between the in-focus modulation transfer function of said imaging system and the modulation transfer function representing the image plane offset for a predetermined range accuracy is substantially maximum; means for locating said grating at the image plane of said imaging system established by objects at a predetermined range; means for moving the image of the object across the grating in a cyclic manner; and means for detecting percent modulation of the light which has passed through the grating.
Claim 5
Dependent Claim
141 words
Apparatus for detecting when an object is at a predetermined range from an optical system comprising: an imaging system having an optical axis, an in-focus modulation transfer function and a modulation transfer function corresponding to the image plane offset for a predetermined range accuracy, a grating having transparent regions defining a single spatial frequency equal to that at which the difference in amplitude between the in-focus modulation transfer function of said imaging system and the modulation transfer function representing the image plane offset for a predetermined range accuracy is substantially maximum; means for locating said grating at the image plane of said imaging system established by objects at a predetermined range; means for moving the image of the object across the grating in a cyclic manner; and means for detecting percent modulation of the light which has passed through the grating.
Claim 6
Dependent Claim
32 words
The apparatus of claim 3 wherein said spatial frequency is that frequency at which the modulation transfer function representing the maximum focus offset for a predetermined range accuracy has a minimum amplitude.
Claim 7
Dependent Claim
19 words
The apparatus of claim 3 wherein said grating is maintained stationary with respect to rotation about said optical axis.
Claim 8
Dependent Claim
18 words
The apparatus of claim 3 wherein said providing means includes an optical wedge rotated about said optical axis.
Claim 9
Dependent Claim
16 words
The apparatus of claim 6 wherein said optical wedge is located ahead of said imaging system.
Claim 10
Dependent Claim
49 words
The apparatus of claim 3 wherein said detecting means includes a detector, means for focusing light which has passed through said grating onto said detector, means for detecting the modulation envelope of the signal from said detector and means for full-wave rectifying the output from said modulation envelope detector.
Claim 11
Dependent Claim
42 words
The apparatus of claim 8 and further including adaptive threshold means responsive to the amplitude of the output of said full-wave rectifying means for producing a signal whenever said full-wave rectifying means output exceeds a predetermined level indicating a predetermined percent modulation.
Claim 12
Dependent Claim
23 words
The apparatus of claim 3 wherein said grating includes an opaque body having transparent regions arranged at the apices of a hexagonal pattern.
Claim 13
Dependent Claim
20 words
The apparatus of claim 3 wherein said grating includes a body having a checkerboard arrangement of transparent and opaque regions.
Claim 14
Dependent Claim
163 words
A passive optical fuse for detonating a charge carried by an ordinance device, when said device is at a predetermined distance from an object comprising: an imaging system having an in-focus modulation transfer function and a modulation transfer function corresponding to the image plane offset for a predetermined range accuracy; a grating having transparent regions definning a single spatial frequency equal to that at which the difference in amplitude between the in-focus modulation transfer function of said imaging system and the modulation transfer function of said imaging system representing the image plane offset for a predetermined range accuracy is substantially maximum; means for locating said stationary grating at the image plane of said imaging system for a predetermined range; means for moving the image of the object across the grating in a cyclic manner; means for detecting percent modulation of the light which has passed through the grating; and means responsive to the percent modulation reaching a predetermined percent for detonating said charge.
Claim 15
Dependent Claim
163 words
A passive optical fuse for detonating a charge carried by an ordinance device, when said device is at a predetermined distance from an object comprising: an imaging system having an in-focus modulation transfer function and a modulation transfer function corresponding to the image plane offset for a predetermined range accuracy; a grating having transparent regions definning a single spatial frequency equal to that at which the difference in amplitude between the in-focus modulation transfer function of said imaging system and the modulation transfer function of said imaging system representing the image plane offset for a predetermined range accuracy is substantially maximum; means for locating said stationary grating at the image plane of said imaging system for a predetermined range; means for moving the image of the object across the grating in a cyclic manner; means for detecting percent modulation of the light which has passed through the grating; and means responsive to the percent modulation reaching a predetermined percent for detonating said charge.
Claim 16
Dependent Claim
141 words
Apparatus for detecting when an object is in focus at a predetermined location with respect to an optical system having a predetermined in-focus modulation transfer function and a modulation transfer function corresponding to the image plane offset for a predetermined range accuracy comprising: a grating at said predetermined location having transparent regions defining a single spatial frequency equal to that at which the difference in amplitude between the in-focus modulation transfer function and the modulation transfer function representing the image plane offset for a predetermined accuracy is substantially maximum; means for moving the image of the object formed by said optical system across said grating in a cyclic manner; and means for detecting the level of a signal formed from the light which has passed through the grating, whereby a maximum in said level indicates an in-focus condition at said location.
Claim 17
Dependent Claim
141 words
Apparatus for detecting when an object is in focus at a predetermined location with respect to an optical system having a predetermined in-focus modulation transfer function and a modulation transfer function corresponding to the image plane offset for a predetermined range accuracy comprising: a grating at said predetermined location having transparent regions defining a single spatial frequency equal to that at which the difference in amplitude between the in-focus modulation transfer function and the modulation transfer function representing the image plane offset for a predetermined accuracy is substantially maximum; means for moving the image of the object formed by said optical system across said grating in a cyclic manner; and means for detecting the level of a signal formed from the light which has passed through the grating, whereby a maximum in said level indicates an in-focus condition at said location.
Claim 18
Dependent Claim
138 words
Apparatus for detecting when an object is in focus at a predetermined location with respect to an optical system having a predetermined in-focus modulation transfer function and a modulation transfer function representing the image plane offset for a predetermined accuracy comprising: a grating at said location with spaced apertures patterned so as to represent a single spatial frequency equal to that at which the difference in amplitude between the in-focus modulation transfer function and the modulation transfer function representing the image plane offset for a predetermined accuracy is substantially maximum; means for causing the image formed by said optical system to cyclically pass by a fixed number of apertures per cycle; and means for detecting percent modulation of the light which has passed through the grating, whereby a maximum modulation percentage indicates an in-focus condition at said location.
Claim 19
Dependent Claim
138 words
Apparatus for detecting when an object is in focus at a predetermined location with respect to an optical system having a predetermined in-focus modulation transfer function and a modulation transfer function representing the image plane offset for a predetermined accuracy comprising: a grating at said location with spaced apertures patterned so as to represent a single spatial frequency equal to that at which the difference in amplitude between the in-focus modulation transfer function and the modulation transfer function representing the image plane offset for a predetermined accuracy is substantially maximum; means for causing the image formed by said optical system to cyclically pass by a fixed number of apertures per cycle; and means for detecting percent modulation of the light which has passed through the grating, whereby a maximum modulation percentage indicates an in-focus condition at said location.
Claim 20
Dependent Claim
23 words
The apparatus of claim 14 wherein said grating is maintained stationary with respect to rotation about the optical axis of said optical system.
Claim 21
Dependent Claim
106 words
Apparatus for detecting when an object is in focus at a predetermined location with respect to an optical system comprising: a grating at said location, said grating having spaced apertures patterned so as to represent a single spatial frequency in the direction of a cyclically moving image thereon and set to maximize the response of said apparatus; means for causing the image formed by said optical system to cyclically pass by a fixed number of said apertures per cycle; and means for detecting percent modulation of the light which has passed through the grating, whereby a maximum modulation percentage indicates an in-focus condition at said location.
Claim 22
Dependent Claim
106 words
Apparatus for detecting when an object is in focus at a predetermined location with respect to an optical system comprising: a grating at said location, said grating having spaced apertures patterned so as to represent a single spatial frequency in the direction of a cyclically moving image thereon and set to maximize the response of said apparatus; means for causing the image formed by said optical system to cyclically pass by a fixed number of said apertures per cycle; and means for detecting percent modulation of the light which has passed through the grating, whereby a maximum modulation percentage indicates an in-focus condition at said location.
Claim 23
Independent Claim
143 words
A method for improving the detection of the distance of an object from an optical system comprising: locating a member having transparent and opaque regions on the image side of the optical system, with the transparent regions of said member defining a single spatial frequency in the direction of a moving image thereon, said spatial frequency being based on the in-focus resolution of the optical system and the resolution of the optical system for a predetermined out-of-focus condition; moving the image of the object across said member so as to cut the transparent regions of said member in a cycle manner; and detecting the level of a signal derived from the light which has passed through said member, whereby a maximum in the level of said signal indicates an in-focus condition and thus a predetermined distance of the object from the optical system.
Claim 24
Independent Claim
143 words
A method for improving the detection of the distance of an object from an optical system comprising: locating a member having transparent and opaque regions on the image side of the optical system, with the transparent regions of said member defining a single spatial frequency in the direction of a moving image thereon, said spatial frequency being based on the in-focus resolution of the optical system and the resolution of the optical system for a predetermined out-of-focus condition; moving the image of the object across said member so as to cut the transparent regions of said member in a cycle manner; and detecting the level of a signal derived from the light which has passed through said member, whereby a maximum in the level of said signal indicates an in-focus condition and thus a predetermined distance of the object from the optical system.
Claim 25
Dependent Claim
19 words
The method of claim 17 wherein said resolution is measured by the modulation transfer function of the optical system.
Claim 26
Dependent Claim
22 words
The method of claim 17 wherein said member is stationary with respect to rotation about the optical axis of said optical system.
Claim 27
Dependent Claim
135 words
Apparatus for detecting the distance of an object from an optical system comprising: a member having transparent and opaque regions, with the transparent regions of said member defining a single spatial frequency in the direction of the movement of an image thereon, said spatial frequency being based on the in-focus resolution of the optical system and the resolution of the optical system for a predetermined out-of-focus condition; means for locating said member at a location on the image side of said optical system; means for moving the image of said object across said member; and means for detecting the amount of modulation of the light which has passed through said member, whereby a maximum in the amount of modulation indicates an in-focus condition and thus a predetermined distance of an object from the optical system.
Claim 28
Dependent Claim
135 words
Apparatus for detecting the distance of an object from an optical system comprising: a member having transparent and opaque regions, with the transparent regions of said member defining a single spatial frequency in the direction of the movement of an image thereon, said spatial frequency being based on the in-focus resolution of the optical system and the resolution of the optical system for a predetermined out-of-focus condition; means for locating said member at a location on the image side of said optical system; means for moving the image of said object across said member; and means for detecting the amount of modulation of the light which has passed through said member, whereby a maximum in the amount of modulation indicates an in-focus condition and thus a predetermined distance of an object from the optical system.
Claim 29
Dependent Claim
19 words
The apparatus of claim 20 wherein said resolution is measured by the modulation transfer function of the optical system.
Claim 30
Dependent Claim
26 words
The apparatus of claim 20 and further including means for maintaining said member stationary with respect to rotation about the optical axis of said optical system.
Claim 31
Dependent Claim
191 words
In an optical system having means for detecting when an object is in-focus and thus at a predetermined distance from the focusing means thereof, in which said system includes a grating and means for moving the image of the object produced by the focusing means across the grating in a cyclic manner, the focusing means having a modulation transfer function for an image plane established by an in-focus object, and a modulation transfer function for an image plane which is offset from the in-focus image plane by an amount corresponding to a predetermined difference in location between an in-focus object and an out-of-focus object, a method for optimizing the response of said system, comprising the steps of: providing a grating having opaque and transparent regions defining a single spatial frequency, the spacing of said transparent regions being such that the spatial frequency of said grating is equal to that at which the difference in amplitude between said in-focus modulation transfer function and said offset modulation transfer function is substantially maximum, whereby said grating is matched to the resolution of said optical system, and locating said grating at said in-focus image plane.
Claim 32
Dependent Claim
191 words
In an optical system having means for detecting when an object is in-focus and thus at a predetermined distance from the focusing means thereof, in which said system includes a grating and means for moving the image of the object produced by the focusing means across the grating in a cyclic manner, the focusing means having a modulation transfer function for an image plane established by an in-focus object, and a modulation transfer function for an image plane which is offset from the in-focus image plane by an amount corresponding to a predetermined difference in location between an in-focus object and an out-of-focus object, a method for optimizing the response of said system, comprising the steps of: providing a grating having opaque and transparent regions defining a single spatial frequency, the spacing of said transparent regions being such that the spatial frequency of said grating is equal to that at which the difference in amplitude between said in-focus modulation transfer function and said offset modulation transfer function is substantially maximum, whereby said grating is matched to the resolution of said optical system, and locating said grating at said in-focus image plane.
Claim 33
Independent Claim
78 words
A method of optimizing the performance of a focus detection system utilizing a grating, focusing means, and means for causing the image produced by said focusing means to cyclically traverse the grating comprising: providing a gratng with apertures defining a single spatial frequency in the direction of the cyclical traverse of the image and, matching the single spatial frequency to the resolution of the focusing means in terms of in-focus and out-of-focus MTF characteristics for the focusing means.
Claim 34
Independent Claim
78 words
A method of optimizing the performance of a focus detection system utilizing a grating, focusing means, and means for causing the image produced by said focusing means to cyclically traverse the grating comprising: providing a gratng with apertures defining a single spatial frequency in the direction of the cyclical traverse of the image and, matching the single spatial frequency to the resolution of the focusing means in terms of in-focus and out-of-focus MTF characteristics for the focusing means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-06-06 | 1980-12-06 | 1981-06-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-06-06 | 1984-12-06 | 1985-06-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-06-06 | 1988-12-06 | 1989-06-07 | $7700.00 | Window Closed / Lapsed |