US5325146A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Auto focus control system for a rear-focus lens apparatus
Assignee: Fujifilm Corp
•
Filing: 1992-09-04
•
Granted: 1994-06-28
•
Expires: 2012-09-04
Abstract
Abstract A differential value of a characteristic curve of a focus distance of a zooming lens versus a position of a focus lens is calculated or found from a table in a contrast or phase difference type auto focus mechanism by detecting a high frequency part of an image signal. A follow-up speed of a focus lens is stepped or continuously changed based on the differential value. A focus position of a focus lens can therefore be changed smoothly corresponding to displacement of a focus distance of a zooming lens. A current brightness and a brightness when the evaluative value is peak is compared. If a brightness difference is large, a peak is not recognized and processing is repeated. Also, a gain of an amplifier is reduced corresponding to a linear-, step- or curve characteristic of a focus position of the focus lens versus a focus distance of the zooming lens when a gain of an AGC circuit is relatively high, so that noise is a high frequency part is reduced. If an iris of the apparatus is relatively closed a gain of the AGC or an amplifier is relatively high, noise increases and the reference value therefore increases to judge a peak of an evaluative value certainly. If the iris is relatively opened, a gain of the AGC and the amplifier is relatively low and noise decreases wherein a peak is rapidly detected without the focus lens passing a focus point.
Inventors
- 👤 Shigeo Toji
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 13:42
CPC Classifications
G; G02; G02B; G02B7/00; G02B7/02; G02B7/04; G02B7/10; G02B7/102
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
74 words
A contrast auto-focus control apparatus comprising: auto-focus means having a focus lens provided behind a zooming lens; detection means for detecting a differential value of a predetermined characteristic curve of a relationship between a focus distance of said zooming lens and a position of said focus lens; and control mean for varying follow-up speed of said focus lens to position said focus lens with respect to said focus distance based on said differential value.
Claim 2
Dependent Claim
74 words
A contrast auto-focus control apparatus comprising: auto-focus means having a focus lens provided behind a zooming lens; detection means for detecting a differential value of a predetermined characteristic curve of a relationship between a focus distance of said zooming lens and a position of said focus lens; and control mean for varying follow-up speed of said focus lens to position said focus lens with respect to said focus distance based on said differential value.
Claim 3
Dependent Claim
124 words
The contrast auto-focus control apparatus of claim 1, further comprising: evaluation means for detecting an evaluative value for focusing by detecting a high frequency part of a signal of a picture image; positioning means for positioning the focus lens at a point where said evaluative value peaks; brightness means for detecting a brightness of an object of the picture image; comparison means for comparing the brightness of the object when said evaluative value peaks and a current brightness of the object to determined a displacement of brightness; and judgement means for judge a peak of said evaluative value as reliable when the displacement of brightness is within a predetermined level and as unreliable when the displacement of brightness is not within said predetermined level.
Claim 4
Dependent Claim
108 words
The contrast auto-focus control apparatus of claim 1, further comprising: automatic gain control means for controlling a gain of an image signal of a picture image of an object generated by photographing means; evaluation means for detecting an evaluative value for focusing by detecting a high frequency part of an output signal from said automatic gain control mean; positioning means for positioning the focus lens at a point where said evaluative value peaks; wave detecting means for detecting said high frequency part in accordance with a gain value of said automatic gain control means; and reduction means for reducing the gain value used by said wave detecting means.
Claim 5
Dependent Claim
84 words
The contrast auto-focus control apparatus of claim 1, further comprising: evaluation means for detecting an evaluative value for focusing by detecting a high frequency part of an image signal of a picture image; positioning means for positioning the focus lens at a point where said evaluative value peaks; and reference value varying means for varying a reference value depending on an opening degree of an iris, wherein a displacement of said evaluative value is judged as reliable or unreliable based on said reference value.
Claim 6
Dependent Claim
112 words
The contrast auto-focus control apparatus of claim 1, further comprising: automatic gain control means for controlling a gain of an image signal of a picture image of an object generated by photographing means; evaluation means for detecting an evaluative value for focusing by detecting a high frequency part of an output signal of said automatic gain control means; positioning means for positioning the focus lens at a point where said valuation value peaks; and reference value varying means for varying a reference value depending on a gain value of said automatic gain control means, wherein a displacement of said evaluative value is judged as reliable or unreliable based on said reference value.
Claim 7
Dependent Claim
114 words
The contrast auto-focus control apparatus of claim 1, further comprising: extraction means for picking up a high frequency part of an image signal of a picture image of an object generated by photographing means; wave detecting means for detecting said high frequency part; evaluation means for detecting an evaluative value for focusing based on an output of said wave detecting means; positioning means for positioning the focus lens at a point where said evaluative value peaks; and reference value varying means for varying a reference value depending on a gain value of said wave detecting means, wherein a displacement of said evaluative value is judged as reliable or unreliable based on said reference value.
Claim 8
Dependent Claim
72 words
A contrast auto-focus control method for an auto-focus apparatus having a focus lens provided behind a zooming lens comprising the steps of: detecting a differential value of a predetermined characteristic curve of a relationship between a focus distance of the zooming lens and a position of the focus lens; and varying follow-up speed of the focus lens to position the focus lens at the focus distance based on the detected differential value.
Claim 9
Dependent Claim
72 words
A contrast auto-focus control method for an auto-focus apparatus having a focus lens provided behind a zooming lens comprising the steps of: detecting a differential value of a predetermined characteristic curve of a relationship between a focus distance of the zooming lens and a position of the focus lens; and varying follow-up speed of the focus lens to position the focus lens at the focus distance based on the detected differential value.
Claim 10
Dependent Claim
113 words
The contrast auto-focus control method of claim 7, comprising the further steps of: determining an evaluative value for focusing by detecting a high frequency part of an image signal of a picture image; positioning the focus lens at a point where the evaluative value peaks; detecting a brightness of an object of the picture image; comparing the brightness of the object when the evaluative value peaks and a current brightness of the object to determine a displacement of brightness; and judging a peak of the evaluative value as reliable when the displacement of brightness is within a predetermined level and as unreliable when the displacement of brightness is not within the predetermined level.
Claim 11
Dependent Claim
94 words
The contrast auto-focus control method of claim 7, comprising the further steps of: automatically controlling a level of gain of an image signal of a picture image of an object generated during photography; determining an evaluative value for focusing by detecting a high frequency part of the gain controlled image signal; positioning the focus lens at a point where the evaluative value peaks; wave detecting the high frequency par tin accordance with the gain level used during said step of automatically controlling; and reducing the gain level sued during said step of wave detecting.
Claim 12
Dependent Claim
81 words
The contrast auto-focus control method of claim 7, comprising the further steps of: determining an evaluative value for focusing by detecting a high frequency part of an image signal of a picture image; positioning the focus lens at a point where the evaluative value peaks; and varying a reference value depending on a degree of opening of an iris of the auto-focusing apparatus, wherein a displacement of the evaluative value is judged as reliable or unreliable based on the reference value.
Claim 13
Dependent Claim
98 words
The contrast auto-focus control method of claim 7, comprising the further steps of: automatically controlling a level of gain of an image signal of a picture image of an object generated during photography; determining an evaluative value for focusing by detecting a high frequency part of the gain controlled image signal; positioning the focus lens at a point where the evaluative value peaks; and varying a reference value depending upon the gain level used during said step of automatically controlling, wherein a displacement of the evaluative value is judged as reliable or unreliable based on the reference value.
Claim 14
Dependent Claim
99 words
The contrast auto-focus control method of claim 7, comprising the further steps of: extracting a high frequency part of an image signal of a picture image of an object generated during photography; wave detecting the high frequency part; determining an evaluative value for focusing based on the wave detected high frequency part; positioning the focus lens at a point where the evaluative value peaks; and varying a reference value depending upon the gain level sued during said step of wave detecting, wherein a displacement of the evaluative value is judged as reliable or unreliable based on the reference value.
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) | 1997-06-27 | 1997-12-27 | 1998-06-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-06-27 | 2001-12-27 | 2002-06-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-06-27 | 2005-12-27 | 2006-06-28 | $7700.00 | Window Closed / Lapsed |