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EP0439167A1
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EP
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Focus detection apparatus
Assignee: Canon Inc
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Filing: 1991-01-24
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Granted: —
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Expires: 2011-01-24
Abstract
Abstract This invention relates to a focus detection apparatus for a camera, having a plurality of distance measurement points, for detecting focus states at the respective distance measurement points. In the apparatus of this type, this invention provides a focus detection apparatus wherein as a condition for projecting auxiliary light in a low-contract state, projection/non-projection of the auxiliary light is determined only on the basis of an optical state of a central one of the distance measurement points of the frame, and optimal focusing can be performed for a principal object such as a person.
Inventors
- 👤 Akira C/O Canon Kabushiki Kaisha Akashi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 21:27
CPC Classifications
G; G02; G02B; G02B7/00; G02B7/28; G02B7/34; G02B7/346
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
74 words
A focus detection apparatus comprising: (a) sensor circuits for respectively detecting light beams from different areas of a frame; (b) a determination circuit for determining whether a focus undetectable state occurs on the basis of an output from a sensor circuit corresponding to a specific area of the different areas; and (c) an auxiliary light control circuit for generating a signal for driving an auxiliary light source when the focus undetectable state is determined.
Claim 2
Dependent Claim
31 words
An apparatus according to claim 1, wherein said sensor circuits are arranged in at least right, central, and left portions of the frame, and the specific area is the central area.
Claim 3
Dependent Claim
55 words
An apparatus according to claim 2, wherein said sensor circuit of said central area has first and second sensor portions whose arrangement directions are different from each other, and said auxiliary light control circuit is operated when said determination circuit determines that outputs from said first and second sensor portions both represent focus undetectable states.
Claim 4
Dependent Claim
29 words
An apparatus according to claim 1, further comprising focus detectors for respectively detecting focus states of the different areas on the basis of the outputs from said sensor circuits.
Claim 5
Dependent Claim
22 words
An apparatus according to claim 1, further comprising a specifying circuit for specifying one of the different areas as the specific area.
Claim 6
Dependent Claim
21 words
An apparatus according to claim 5, wherein said specifying circuit specifies an arbitrary area upon operation of a manual operation member.
Claim 7
Dependent Claim
61 words
A camera having a focus detection apparatus, comprising: (a) focus detectors for respectively detecting focus states of different areas of a frame; and (b) an auxiliary light control circuit for driving an auxiliary light source to cause said auxiliary light source to project auxiliary light when a state of a specific area of the different areas is a focus undetectable state.
Claim 8
Dependent Claim
17 words
A camera according to claim 7, wherein the specific area is a central area of the frame.
Claim 9
Dependent Claim
22 words
A camera according to claim 7, further comprising a specifying circuit for specifying one of the different areas as the specific area.
Claim 10
Dependent Claim
21 words
A camera according to claim 9, wherein said specifying circuit specifies an arbitrary area upon operation of a manual operation member.
Claim 11
Dependent Claim
29 words
A camera according to claim 10, further comprising a selector for selecting a predetermined focus state of the focus states of the different areas detected by said focus detectors.
Claim 12
Dependent Claim
23 words
A camera according to claim 11, wherein said selector selects a focus state representing a most rear focus state of the focus states.
Claim 13
Dependent Claim
51 words
A focus detection apparatus having sensor circuits for respectively receiving light beams from a plurality of different areas and for respectively detecting focus states of the different areas, comprising: (a) an inhibition circuit for inhibiting focus state detection of a specific area of the different areas upon projection of auxiliary light.
Claim 14
Dependent Claim
26 words
An apparatus according to claim 13, wherein the specific area is an area in which a sensor circuit not suitable for auxiliary light characteristics is arranged.
Claim 15
Dependent Claim
78 words
A focus detection apparatus having sensor circuits for respectively receiving light beams from a plurality of different areas and a focus state determination circuit for selecting a specific area of the different areas and determining a focus state of the specific area on the basis of an output from said sensor circuit corresponding to the specific area, comprising: (a) an inhibition circuit for inhibiting selection of the specific area of the different areas upon projection of auxiliary light.
Claim 16
Dependent Claim
26 words
An apparatus according to claim 15, wherein the specific area is an area in which a sensor circuit not suitable for auxiliary light characteristics is arranged.
Claim 17
Dependent Claim
39 words
An apparatus according to claim 15, wherein the auxiliary light is pattern-projected, and the specific area is an area in which a sensor circuit which is difficult to detect the pattern of the auxiliary light in principle is arranged.
Claim 18
Dependent Claim
115 words
A focus detection apparatus having a first sensor portion for optimally performing focus detection upon reception of first characteristic light and a second sensor portion for optimally performing focus detection upon reception of second characteristic light different from the first characteristic light, comprising: (a) a focus detector for performing focus detection on the basis of an output from said first sensor portion and/or said second sensor portion; and (b) an inhibition circuit for inhibiting focus detection of said focus detector on the basis of thee output from said second sensor portion when an auxiliary light source projects a light on an object, said light being detected as the first characteristic light by said first sensor.
Claim 19
Dependent Claim
49 words
An apparatus according to claim 18, wherein the auxiliary light source projects the first characteristic light, the first sensor portion is arranged in a direction suitable for the first characteristic light, and said second sensor portion is arranged in a direction different from that of said first sensor portion.
Claim 20
Dependent Claim
94 words
A focus detection apparatus having sensor circuits for respectively receiving light beams from a plurality of areas and for respectively detecting focus states of the areas, comprising: (a) a selector for selecting a predetermined focus state of focus states of the areas, said selector having a first mode and a second mode, a focus state selection condition in the first mode being different from that in the second mode; and (b) a specifying circuit for specifying the first mode upon projection of auxiliary light and the second mode upon non-projection of the auxiliary light.
Claim 21
Dependent Claim
100 words
A focus detection apparatus comprising: (a) sensor circuits for receiving light beams from a plurality of areas of a frame; (b) a focus detector for selecting an output from a sensor circuit corresponding to a predetermined area from sensor circuit outputs of the areas and performing focus detection, said focus detector having a first mode and a second mode, an area selection condition in the first mode being different from that in the second mode; and (c) a specifying circuit for specifying the first mode upon projection of auxiliary light and the second mode upon non-projection of the auxiliary light.
Claim 22
Dependent Claim
93 words
A focus detection apparatus having sensor circuits for respectively receiving light beams from a plurality of areas and for respectively detecting focus states of the areas, comprising: (a) a selector having a manual mode for selecting one of the areas by a manual operation and an automatic mode for automatically selecting a specific area of the areas; and (b) an inhibition circuit for inhibiting selection of the specific area by said selector, said inhibition circuit being operative in the automatic mode upon projection of auxiliary light and being inoperative in the manual mode.
Claim 23
Dependent Claim
91 words
A focus detection apparatus for operating an auxiliary light source in a focus undetectable state to perform a focus detection operation, comprising: (a) a signal accumulation type sensor array having a plurality of pixels; (b) a determination circuit for determining whether a minimum level of signal levels accumulated in the plurality of pixels of said sensor arrays is smaller than a predetermined value; and (c) an inhibition circuit for inhibiting an operation of said auxiliary light source when said determination circuit determines the minimum level is smaller than the predetermined value.
Claim 24
Dependent Claim
52 words
An apparatus according to claim 23, further comprising an accumulation time control circuit for controlling a signal accumulation time of said sensor array until an output from said sensor array becomes the predetermined level, and said determination circuit is operated after accumulation time control is performed by said accumulation time control circuit.
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