US3786184A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Focusing
Assignee: Image Analysing Computers Ltd
•
Filing: 1972-02-04
•
Granted: 1974-01-15
•
Expires: 1992-02-04
Abstract
Abstract An automatic focusing system particularly adaptable for use with optical microscopes in which a final image is formed on the photo sensitive target of a television camera. Two objects are spaced by different amounts from the reflecting surfaces associated with the specimen under examination such that the reflected images are equally out of focus when the specimen image is in focus on the camera target.
Inventors
- 👤 L Pieters
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 07:27
CPC Classifications
G; G02; G02B; G02B27/00; G02B27/40
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
307 words
An automatic focusing system for obtaining a correctly focused image of a specimen mounted on a carrier, comprising a first optical system including at least one lens, two objects spaced by different amounts from a first surface disposed on said carrier, said first surface being light reflective, means for producing a single light beam for illuminating said two objects which are positioned in the path of said single beam, a subsidiary optical system for forming an image of said two objects, a lens of said first system forming part of said subsidiary system, a single photosensitive surface onto which the images of said two objects is reflected by said light reflective surface, means for scanning said photosensitive surface and for generating a video signal corresponding thereto, means for deriving from said video signal a first signal whose magnitude corresponds to the degree of sharpness of focus of one of said objects in said image and a second signal whose magnitude corresponds to the degree of sharpness of Focus of the other of said objects in said image, the degree of sharpness of focus of said first and second objects being determined by the spacing between the carrier and said lens which is common to said two optical systems, the spacing between each of said two objects and said photosensitive surface being such so that said two objects are equally de-focused in said image when the spacing between said carrier and said first optical system is such that said specimen is correctly focused, circuit means for generating an electrical error signal whose magnitude is proportional to the difference between said magnitudes of said first and second signals and focus adjusting means operable in response to said error signal for altering the spacing between said carrier and said first optical system to reduce the magnitude of said error signal.
Claim 2
Dependent Claim
307 words
An automatic focusing system for obtaining a correctly focused image of a specimen mounted on a carrier, comprising a first optical system including at least one lens, two objects spaced by different amounts from a first surface disposed on said carrier, said first surface being light reflective, means for producing a single light beam for illuminating said two objects which are positioned in the path of said single beam, a subsidiary optical system for forming an image of said two objects, a lens of said first system forming part of said subsidiary system, a single photosensitive surface onto which the images of said two objects is reflected by said light reflective surface, means for scanning said photosensitive surface and for generating a video signal corresponding thereto, means for deriving from said video signal a first signal whose magnitude corresponds to the degree of sharpness of focus of one of said objects in said image and a second signal whose magnitude corresponds to the degree of sharpness of Focus of the other of said objects in said image, the degree of sharpness of focus of said first and second objects being determined by the spacing between the carrier and said lens which is common to said two optical systems, the spacing between each of said two objects and said photosensitive surface being such so that said two objects are equally de-focused in said image when the spacing between said carrier and said first optical system is such that said specimen is correctly focused, circuit means for generating an electrical error signal whose magnitude is proportional to the difference between said magnitudes of said first and second signals and focus adjusting means operable in response to said error signal for altering the spacing between said carrier and said first optical system to reduce the magnitude of said error signal.
Claim 3
Dependent Claim
40 words
A system as set forth in claim 1 wherein said circuit means generates an error signal which is of a polarity indicative of whether said spacing is to be increased or decreased so as to reduce the error signal magnitude.
Claim 4
Dependent Claim
47 words
A system as set forth in claim 1 wherein said two objects are gratings having parallel alternate narrow and wide slits and wherein said two gratings are positioned so that the narrow slits of one are aligned with the wide slits of the other and vice versa.
Claim 5
Dependent Claim
18 words
A system as set forth in claim 1 in which said first surface is surface of said specimen.
Claim 6
Dependent Claim
25 words
A system as set forth in claim 1 in which said specimen is mounted on a light reflecting backing material which constitutes the reflecting surface.
Claim 7
Dependent Claim
20 words
A system as set forth in claim 1 in which a polished surface of said carrier constitutes the reflecting surface.
Claim 8
Dependent Claim
56 words
A system as set forth in claim 3 in combination with an incident light microscope including an incident light illumination system, in which the two gratings are positioned one on either side of the field stop of the illumination system so that they just extend into the area of the field stop along one edge thereof.
Claim 9
Dependent Claim
30 words
A system as set forth in claim 7 in combination with a television camera in which the focussed image of the specimen is formed on the target of the camera.
Claim 10
Dependent Claim
39 words
A system as set forth in claim 8 in which the images of the gratings are also formed on the camera target and the gratings are orientated so that the slits are perpendicular to the direction of line scanning.
Claim 11
Dependent Claim
54 words
A system as set forth in claim 9 further comprising gating means for gating the video signal obtained by line scanning in synchronism with the scan so as to release as two separate electrical signals the amplitude excursions of the video signal corresponding to the two sets of narrow slits in the two gratings.
Claim 12
Dependent Claim
44 words
A system as set forth in claim 10 wherein means for deriving first and second signals corresponding to the degree of sharpness comprises means for generating an average value of said amplitude excursions during each frame scan for each of said two separate signals.
Claim 13
Dependent Claim
130 words
A system as set forth in claim 3 in combination with a transmission illumination microscope including a source of illumination for illuminating the specimen from below and a secondary illumination system for illuminating the specimen from above in which the two gratings are positioned one on either side of the field stop of the secondary illumination system so that they just extend into the area of the field stop along one edge thereof; the secondary illumination system having a light source producing a radiation of different wavelength from that employed to produce the light for illuminating the specimen from below and said reflecting surface disposed on said carrier comprising a wavelength-selective optical coating which transmits the illumination from the source below the specimen but reflects that from the secondary system.
Claim 14
Dependent Claim
38 words
A system as set forth in claim 12 in which the focussed image of the specimen and the de-focussed images of the gratings are formed on the target of a television camera which is sensitive to Both wavelengths.
Claim 15
Dependent Claim
51 words
A system as set forth in claim 12 including wavelength selective means for separating the transmitted light from the reflected light, a first television camera to which one of the separated beams of light is fed and a second television camera to which the other separated beam of light is fed.
Claim 16
Dependent Claim
40 words
A system as set forth in claim 1 in which said objects have a distinct shape and wherein said image or said two objects formed by said subsidiary optical system corresponds in shape to the distinct shape of said objects.
Claim 17
Dependent Claim
57 words
A system as set forth in claim 15 wherein each of said objects is shaped so that the video signal produced by scanning said image of said two objects on said photosensitive surface has a high frequency component and wherein said means for deriving includes means for separating out said high frequency component of said video signal.
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) | 1977-01-14 | 1977-07-16 | 1978-01-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-14 | 1981-07-16 | 1982-01-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-14 | 1985-07-16 | 1986-01-15 | $7700.00 | Window Closed / Lapsed |