US5021818A
Expired / Lapsed
US
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Multi-area brightness measuring apparatus
Assignee: Pentax Corp
•
Filing: 1989-07-07
•
Granted: 1991-06-04
•
Expires: 2009-07-07
Abstract
Abstract A multi-area brightness measuring apparatus for a camera, which measures the brightness of an object in a center area of a photographing area and a circumferential area surrounding the center area to detect whether the object in the center area is in follow light state or in back light state in order to correct the exposure value. The exposure also can be controlled in accordance with the magnification, i.e. in accordance with the surface area of a main object occupying the center area.
Inventors
- 👤 Osamu Satoh
- 👤 Isamu Hirai
- 👤 Masahiro Nakata
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 05:40
CPC Classifications
G; G03; G03B; G03B7/00; G03B7/08; G03B7/099; G03B7/081; G03B7/087; G03B7/0993; G03B7/0997; G03B7/09971; G03B7/09972
Claims Analysis
Total Claims: 46
Claim 1
Independent Claim
227 words
A multi-area brightness measuring apparatus of a camera comprising a first brightness measuring sensor which detects a brightness of a center area of a photographing area; a second brightness measuring sensor which detects a brightness of a circumferential area surrounding the center area; detecting means for detecting whether the object in the center area is in follow light state or back light state, based on the outputs of the first and second brightness measuring sensors; first brightness information determining means which operates when the detecting means detects the follow light state to generate an output of a brightness value which is obtained by subtracting a predetermined follow light correcting value corresponding to a brightness value obtained by the output of the first brightness measuring sensor from the brightness value obtained by the output of the first brightness measuring sensor; and, second brightness information determining means which operates when the detecting means detects the back light state and when a brightness value obtained by the output of the first brightness measuring sensor is below a first predetermined reference brightness value to generate an output of a brightness value which is obtained by adding a predetermined back light correcting value corresponding to the brightness value obtained by the output of the first brightness measuring sensor to the brightness value obtained by the output of the first brightness measuring sensor.
Claim 2
Dependent Claim
227 words
A multi-area brightness measuring apparatus of a camera comprising a first brightness measuring sensor which detects a brightness of a center area of a photographing area; a second brightness measuring sensor which detects a brightness of a circumferential area surrounding the center area; detecting means for detecting whether the object in the center area is in follow light state or back light state, based on the outputs of the first and second brightness measuring sensors; first brightness information determining means which operates when the detecting means detects the follow light state to generate an output of a brightness value which is obtained by subtracting a predetermined follow light correcting value corresponding to a brightness value obtained by the output of the first brightness measuring sensor from the brightness value obtained by the output of the first brightness measuring sensor; and, second brightness information determining means which operates when the detecting means detects the back light state and when a brightness value obtained by the output of the first brightness measuring sensor is below a first predetermined reference brightness value to generate an output of a brightness value which is obtained by adding a predetermined back light correcting value corresponding to the brightness value obtained by the output of the first brightness measuring sensor to the brightness value obtained by the output of the first brightness measuring sensor.
Claim 3
Dependent Claim
70 words
A multi-area brightness measuring apparatus according to claim 1, wherein said detecting means detects the follow light state when a brightness value which is obtained by subtracting the brightness value obtained by the second brightness measuring sensor from the brightness value obtained by the first brightness measuring sensor is above a predetermined positive value, and detects the back light state when the subtracted value is below a predetermined negative value.
Claim 4
Dependent Claim
45 words
A multi-area brightness measuring apparatus according to claim 1, wherein said first brightness information determining means outputs, as brightness data, the brightness value obtained by the first brightness measuring sensor when the detecting means detects neither the follow light state nor the back light state.
Claim 5
Dependent Claim
65 words
A multi-area brightness measuring apparatus according to claim 1, wherein said first brightness information determining means determines the follow light correcting value to be half a difference of the brightness value obtained by the first brightness measuring sensor and the brightness value obtained by the second brightness measuring sensor, when the brightness value obtained by the first brightness measuring means is below a predetermined value.
Claim 6
Dependent Claim
42 words
A multi-area brightness measuring apparatus according to claim 1, wherein the follow light correcting value determined by the first brightness information determining means increases as the brightness value obtained by the first brightness measuring means which is above a predetermined value increases.
Claim 7
Dependent Claim
51 words
A multi-are brightness measuring apparatus according to claim 1, wherein said second brightness information determining means determines the maximum values of the follow light correcting value and the back light correcting value to be a difference in brightness value between the first brightness measuring sensor and the second brightness measuring sensor.
Claim 8
Dependent Claim
64 words
A multi-are brightness measuring apparatus according to claim 1, wherein said second brightness information determining means determines the maximum values of the follow light correcting value and the back light correcting value to be a predetermined maximum correcting value when a difference in brightness value between the first brightness measuring sensor and the second brightness measuring sensor is above the predetermined maximum correcting value.
Claim 9
Dependent Claim
32 words
A multi-area brightness measuring apparatus according to claim 1, wherein said detecting means, said first brightness information determining means and said second brightness information determining means are constructed by a same CPU.
Claim 10
Dependent Claim
117 words
A multi-area brightness measuring apparatus according to claim 1, further comprising a third brightness information determining means which operates when the detecting means detects the back light state and when a brightness value obtained by the output of the first brightness measuring sensor is below a first predetermined reference brightness value to output, as the brightness data, a brightness value which is obtained by subtracting a magnification correcting value corresponding to a magnification which is obtained by the focal length of a photographing lens and an object distance of the object in said center area from the brightness value obtained by the output of the first brightness measuring sensor when the magnification is within a predetermined range.
Claim 11
Dependent Claim
70 words
A multi-area brightness measuring apparatus according to claim 9, wherein said detecting means detects the follow light state when a brightness value which is obtained by subtracting the brightness value obtained by the second brightness measuring sensor from the brightness value obtained by the first brightness measuring sensor is above a predetermined positive value, and detects the back light state when the subtracted value is below a predetermined negative value.
Claim 12
Dependent Claim
45 words
A multi-area brightness measuring apparatus according to claim 9, wherein said first brightness information determining means outputs, as brightness data, the brightness value obtained by the first brightness measuring sensor when the detecting means detects neither the follow light state nor the back light state.
Claim 13
Dependent Claim
65 words
A multi-area brightness measuring apparatus according to claim 9, wherein said first brightness information determining means determines the follow light correcting value to be half a difference of the brightness value obtained by the first brightness measuring sensor and the brightness value obtained by the second brightness measuring sensor, when the brightness value obtained by the first brightness measuring means is below a predetermined value.
Claim 14
Dependent Claim
42 words
A multi-area brightness measuring apparatus according to claim 9, wherein the follow light correcting value determined by the first brightness information determining means increases as the brightness value obtained by the first brightness measuring means which is above a predetermined value increases.
Claim 15
Dependent Claim
50 words
A multi-area brightness measuring apparatus according to claim 9, wherein said second brightness information determining means determines the maximum values of the follow light correcting value and the back light correcting value to be a difference brightness value between the first brightness measuring sensor and the second brightness measuring sensor.
Claim 16
Dependent Claim
64 words
A multi-area brightness measuring apparatus according to claim 9, wherein said second brightness information determining means determines the maximum values of the follow light correcting value and the back light correcting value to be a determined maximum correcting value when a difference in brightness value between the first brightness measuring sensor and the second brightness measuring sensor is above the predetermined maximum correcting value.
Claim 17
Dependent Claim
42 words
A multi-area brightness measuring apparatus according to claim 9, wherein said magnification within a predetermined range includes X/2 9 magnification, wherein X represent a size (mm) in an image plane of a light receiving area of the first brightness information measuring sensor.
Claim 18
Dependent Claim
88 words
A multi-area brightness measuring apparatus according to claim 9, wherein supposing that the exposure value based on the brightness value obtained by the output of the first brightness measuring sensor is E va , the magnification M v and the magnification correcting value C corresponding to the magnification are given by the following equations: M.sub.v =D.sub.v /2-f.sub.v +10 C=ω(M.sub.v -8)(E.sub.va -8)/32 wherein ω=constant, D v =2log 2 D and f v =log 2 f, [wherein D is an object distance (m) and f is a focal length (mm)].
Claim 19
Dependent Claim
39 words
A multi-area brightness measuring apparatus according to claim 9, further comprising a lens correcting means for correcting the brightness obtained by the output of the first brightness measuring sensor in accordance with the kind of the photographing lens used.
Claim 20
Dependent Claim
26 words
A multi-area brightness measuring apparatus according to claim 9, wherein it is mounted to a camera body in which the photographing lens can be detachably attached.
Claim 21
Dependent Claim
33 words
A multi-area brightness measuring apparatus according to claim 19, wherein data of the focal length are input to said third brightness information determining means from the photographing lens mounted to the camera body.
Claim 22
Dependent Claim
25 words
A multi-area brightness measuring apparatus according to claim 19, wherein said photographing lens comprises a memory in which at least focal length information is stored.
Claim 23
Dependent Claim
82 words
A multi-area brightness measuring apparatus according to claim 21, wherein the camera body has a body mount which is provided a group of electrical contacts and wherein said photographing lens has a mount which is provided with a group of electrical contacts which are brought into contact with the electrical contacts of the body mount, so that the focal length information stored in the memory can be input to the third brightness information determining means through the groups of the electrical contacts.
Claim 24
Dependent Claim
31 words
A multi-area brightness measuring apparatus according to claim 22, wherein said camera has at least one movable lens which is movable in the optical axis directions to adjust the focal length.
Claim 25
Dependent Claim
72 words
A multi-area brightness measuring apparatus according to claim 23, wherein the photographing lens comprises a zoom code plate on which the position of the movable lens is coded, a brush which comes into slide contact with the zoom code plate, and a memory in which data of focal length corresponding to the coded information of the code plate representing the contact position of the brush with the zoom code plate are stored.
Claim 26
Dependent Claim
43 words
A multi-area brightness measuring apparatus according to claim 24, wherein the focal length data stored in the memory corresponding to the code information are supplied to the first brightness information determining means or the lens correcting means through the group of electrical contacts.
Claim 27
Dependent Claim
26 words
A multi-area brightness measuring apparatus according to claim 24, further comprising detecting means for detecting the kind of the photographing lens mounted to the camera body.
Claim 28
Dependent Claim
43 words
A multi-area brightness measuring apparatus according to claim 26, further comprising a correcting means for correcting the brightness value obtained by the output of the first brightness measuring sensor, in accordance with the kind of the photographing lens detected by the detecting means.
Claim 29
Dependent Claim
96 words
A multi-area brightness measuring apparatus according to claim 27, wherein when said detecting means detects that the photographing lens has the group of the electrical contacts corresponding to the electrical contacts of the camera body and the memory in which at least the focal length information are stored, the information of the memory are supplied to the detecting means for detecting the follow light state and the back light state and the brightness information determining means through the electrical contacts, so that the follow light correction, the back light correction and/or magnification correction can be effected.
Claim 30
Dependent Claim
60 words
A multi-area brightness measuring apparatus according to claim 28, wherein said detecting means for detecting the follow light state and the back light state, the first brightness information determining means, the second brightness information determining means, the third brightness information determining means, and the detecting means for detecting the kind of the photographing lens are constituted by a same CPU.
Claim 31
Dependent Claim
135 words
A multi-area brightness measuring apparatus of a camera comprising a first brightness measuring sensor which detects a brightness of a center area of a photographing area; a second brightness measuring sensor which detects a brightness of a circumferential area surrounding the center area; detecting means for detecting whether the object in the center area is in follow light state of back light state, based on the outputs of the first and second brightness measuring sensors; and, brightness information determining means which operates when the detecting means detects the back light state and which corrects the outputs of the first brightness measuring sensor and the second brightness measuring sensor in accordance with a magnification which is obtained by the focal length of a photographing lens and an object distance of the object in said center area.
Claim 32
Dependent Claim
135 words
A multi-area brightness measuring apparatus of a camera comprising a first brightness measuring sensor which detects a brightness of a center area of a photographing area; a second brightness measuring sensor which detects a brightness of a circumferential area surrounding the center area; detecting means for detecting whether the object in the center area is in follow light state of back light state, based on the outputs of the first and second brightness measuring sensors; and, brightness information determining means which operates when the detecting means detects the back light state and which corrects the outputs of the first brightness measuring sensor and the second brightness measuring sensor in accordance with a magnification which is obtained by the focal length of a photographing lens and an object distance of the object in said center area.
Claim 33
Dependent Claim
66 words
A multi-area brightness measuring apparatus according to claim 30, further comprising an additional brightness information determining means which determines the maximum values of the follow light correcting value and the back light correcting value to be a predetermined maximum correcting value when a difference in brightness value between the first brightness measuring sensor and the second brightness measuring sensor is above the predetermined maximum correcting value.
Claim 34
Dependent Claim
42 words
A multi-area brightness measuring apparatus according to claim 30, wherein said magnification within a predetermined range includes X/2 9 magnification, wherein X represents a size (mm) in an image plane of a light receiving area of the first brightness information measuring sensor.
Claim 35
Dependent Claim
88 words
A multi-area brightness measuring apparatus according to claim 30, wherein supposing that the exposure value based on the brightness value obtained by the output of the first brightness measuring sensor is E va , the magnification M v and the magnification correcting value C corresponding to the magnification are given by the following equations: M.sub.v =D.sub.v /2-f.sub.v +10 C=ω(M.sub.v -8)(E.sub.va -8)/32 wherein ω=constant, D v =2log 2 D and f v =log 2 f, [wherein D is an object distance (m) and f is a focal length (mm)].
Claim 36
Dependent Claim
39 words
A multi-area brightness measuring apparatus according to claim 30, further comprising a lens correcting means for correcting the brightness obtained by the output of the first brightness measuring sensor in accordance with the kind of the photographing lens used.
Claim 37
Dependent Claim
26 words
A multi-area brightness measuring apparatus according to claim 30, wherein it is mounted to a camera body in which the photographing lens can be detachably attached.
Claim 38
Dependent Claim
25 words
A multi-area brightness measuring apparatus according to claim 35, wherein said photographing lens comprises a memory in which at least focal length information is stored.
Claim 39
Dependent Claim
82 words
A multi-area brightness measuring apparatus according to claim 36, wherein the camera body has a body mount which is provided a group of electrical contacts and wherein said photographing lens has a mount which is provided with a group of electrical contacts which are brought into contact with the electrical contacts of the body mount, so that the focal length information stored in the memory can be input to the third brightness information determining means through the groups of the electrical contacts.
Claim 40
Dependent Claim
31 words
A multi-area brightness measuring apparatus according to claim 37, wherein said camera has at least one movable lens which is movable in the optical axis directions to adjust the focal length.
Claim 41
Dependent Claim
72 words
A multi-area brightness measuring apparatus according to claim 38, wherein the photographing lens comprises a zoom code plate on which the position of the movable lens is coded, a brush which comes into slide contact with the zoom code plate, and a memory in which data of focal length corresponding to the coded information of the code plate representing the contact position of the brush with the zoom code plate are stored.
Claim 42
Dependent Claim
43 words
A multi-area brightness measuring apparatus according to claim 39, wherein the focal length data stored in the memory corresponding to the code information are supplied to the first brightness information determining means or the lens correcting means through the groups of electrical contacts.
Claim 43
Dependent Claim
26 words
A multi-area brightness measuring apparatus according to claim 40, further comprising detecting means for detecting the kind of the photographing lens mounted to the camera body.
Claim 44
Dependent Claim
43 words
A multi-area brightness measuring apparatus according to claim 41, further comprising a correcting means for correcting the brightness value obtained by the output of the first brightness measuring sensor, in accordance with the kind of the photographing lens detected by the detecting means.
Claim 45
Dependent Claim
96 words
A multi-area brightness measuring apparatus according to claim 42, wherein when said detecting means detects that the photographing lens has the group of the electrical contacts corresponding to the electrical contacts of the camera body and the memory in which at least the focal length information are stored, the information of the memory are supplied to the detecting means for detecting the follow light state and the back light state and the brightness information determining means through the electrical contacts, so that the follow light correction, the back light correction and/or magnification correction can be effected.
Claim 46
Dependent Claim
54 words
A multi-area brightness measuring apparatus according to claim 43, wherein said detecting means for detecting the follow light state and the back light state, the first brightness information determining means, said additional brightness information determining means, and the detecting means for detecting the kind of the photographing lens are constituted by a same CPU.
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