Auto focus control device and method including selecting a zone for detecting an evaluative value for focusing in accordance with photographing direction

Claim 2

An auto focus control device comprising: means for determining if a photographing direction of a video camera is against the light; means for providing, on a picture plane of said video camera, a zone for measuring a distance between said video camera and an object; means for providing an enlarged zone for measuring said distance when said means for determining determines said photographing direction to be against the light, wherein said enlarged zone is larger than said zone; means for detecting an evaluative value for focusing, by detecting a high frequency part of a picture image signal in said enlarged zone when said means for determining determines said photographing direction to be against the light, and by detecting a high frequency part of a picture image signal in said zone when said means for determining does not determine said photographing direction to be against the light; means for moving a focus lens based on an evaluative value for focusing detected by said means for detecting in a zone provided in accordance with said photographing direction; means for judging, for each moving of said focus lens, if an evaluative value for focusing at a current point after moving of said focus lens exceeds, by a predetermined reference value, an evaluative value for focusing at a previous point before moving of said focus lens; and means for positioning said focus lens so that said evaluative value for focusing becomes a maximum, based on a result of said judgment with respect to the increase of an evaluative value for focusing.

Claim 3

An auto focus control device claimed in claim 1, further comprising: means for detecting a brightness of the object, wherein said brightness is different from said evaluative value for focusing; means for detecting the difference in brightness of the object when said evaluative value for focusing is a maximum versus the brightness of said object when said evaluative value for focusing is a minimum; means for deciding if said detected difference in brightness is not within a predetermined level; and means for restarting an auto focus process when said means for deciding decides said detected difference in brightness to be not within said predetermined level, wherein said means for positioning holds said focus lens at a point where said evaluative value for focusing becomes a maximum when said means for judging determines said detected difference in brightness to be within said predetermined level.

Claim 4

An auto focus control device claimed in claim 1, further comprising: an automatic gain control circuit for inputting a picture image signal from a photographing unit of said camera; an amplifier for further amplifying a picture image signal from said automatic gain control circuit, wherein said means for detecting detects said evaluative value for focusing from a picture image signal amplified by said amplifier; and means for reducing a gain of said amplifier, depending on a gain of said automatic gain control circuit.

Claim 5

An auto focus control device claimed in claim 1, further comprising: means for varying said reference value used for said judgement with respect to the increase of said evaluative value for focusing, depending on an opening degree of an iris.

Claim 6

Art auto focus control device claimed in claim 1, further comprising: an automatic gain control circuit for inputting a picture image signal from a photographing unit of said camera, wherein said means for detecting detects said evaluative value for focusing from a picture image signal amplified by said automatic gain control circuit; and means for varying said reference value used for said judgment with respect to the increase of said evaluative value for focusing, depending on a gain of said automatic gain control circuit.

Claim 7

An auto focus control device claimed in claim 1, further comprising: an automatic gain control circuit for inputting a picture image signal from a photographing unit of said camera; an amplifier for further amplifying a picture image signal from said automatic gain control circuit, wherein said means for detecting detects said evaluative value for focusing from a picture image signal amplified by said amplifier; and means for varying said reference-value used for said judgment with respect to the increase of said evaluative value for focusing, depending on a gain of said amplifier.

Claim 8

An auto focus control device claimed in claim 1, wherein said means for determining includes performing multi-divided light measurement.

Claim 9

An auto focus control device claimed in claim 7, further comprising: an automatic gain control circuit for inputting a picture image signal from a photographing unit of said camera; an amplifier for further amplifying a picture image signal from said automatic gain control circuit, wherein said means for detecting detects said evaluative value for focusing from a picture image signal amplified by said amplifier; means for reducing a gain of said amplifier, depending on a gain of said automatic gain control circuit; means for varying said reference value used for said judgment with respect to the increase of said evaluative value for focusing, depending on an opening degree of an iris, the gain of said automatic gain control circuit, and the gain of said amplifier; means for detecting a brightness of the object, wherein said brightness is different from said evaluative value for focusing; means for detecting the difference in brightness of the object when said evaluative value for focusing is a maximum versus the brightness of said object when said evaluative value for focusing is a minimum; means for deciding if said detected difference in brightness is not within a predetermined level; and means for restarting an auto focus process when said means for deciding decides said detected difference in brightness to be not within said predetermined level, wherein said means for positioning holds said focus lens at a point where said evaluative value for focusing becomes a maximum when said means for judging determines said detected difference in brightness to be within said predetermined level.

Claim 10

An auto focus control method comprising the steps of: determining if a photographing direction of a video camera is against the light; providing, on a picture plane of said video camera, a zone for measuring a distance between said video camera and an object: providing an enlarged zone for measuring said distance when said determining step determines said photographing direction to be against the light, wherein said enlarged zone is larger than said zone; detecting an evaluative value for focusing, by detecting a high frequency part of a picture image signal in said enlarged zone when said determining step determines said photographing direction to be against the light, and by detecting a high frequency part of a picture image signal in said zone when said determining step does not determine said photographing direction to be against the light; moving a focus lens based on an evaluative value for focusing detected by said detecting step in a zone provided in accordance with said photographing direction; judging, for each moving of said focus lens, if an evaluative value for focusing at a current point after moving of said focus lens exceeds, by a predetermined reference value, an evaluative value for focusing at a previous point before moving of said focus lens; and positioning said focus lens so that said evaluative value for focusing becomes a maximum, based on a result of said judging step.

Claim 11

An auto focus control method comprising the steps of: determining if a photographing direction of a video camera is against the light; providing, on a picture plane of said video camera, a zone for measuring a distance between said video camera and an object: providing an enlarged zone for measuring said distance when said determining step determines said photographing direction to be against the light, wherein said enlarged zone is larger than said zone; detecting an evaluative value for focusing, by detecting a high frequency part of a picture image signal in said enlarged zone when said determining step determines said photographing direction to be against the light, and by detecting a high frequency part of a picture image signal in said zone when said determining step does not determine said photographing direction to be against the light; moving a focus lens based on an evaluative value for focusing detected by said detecting step in a zone provided in accordance with said photographing direction; judging, for each moving of said focus lens, if an evaluative value for focusing at a current point after moving of said focus lens exceeds, by a predetermined reference value, an evaluative value for focusing at a previous point before moving of said focus lens; and positioning said focus lens so that said evaluative value for focusing becomes a maximum, based on a result of said judging step.

Claim 12

An auto focus control method claimed in claim 9, further comprising: detecting a brightness of the object, wherein said brightness is different from said evaluative value for focusing; detecting a difference in a brightness of the object when said evaluative value for focusing is a maximum and a brightness of said object when said evaluative value for focusing is a minimum; deciding if said detected difference in brightness is not within a predetermined level; and restarting an auto focus process when said deciding step determines said detected difference in brightness to be not within said predetermined level, wherein said positioning step maintains said focus lens at a point where said evaluative value for focusing becomes a maximum when said deciding step determines said detected difference in brightness to be within said predetermined level.

Claim 13

Art auto focus control method claimed in claim 9, further comprising: inputting a picture image signal from a photographing unit of said camera via an automatic gain control circuit; further amplifying a picture image signal from said automatic gain control circuit, wherein said detecting step detects said evaluative value for focusing from a picture image signal amplified by said amplifying step; and reducing a gain of said amplifying step, depending on a gain of said automatic gain control circuit.

Claim 14

An auto focus control method claimed in claim 9, further comprising: varying said reference value used for said judging step with respect to the increase of said evaluative value for focusing, depending on an opening degree of an iris.

Claim 15

An auto focus control method claimed in claim 9, further comprising: inputting a picture image signal from a photographing unit of said camera via an automatic gain control circuit, wherein said detecting step detects said evaluative value for focusing from a picture image signal amplified by said automatic gain control circuit; and varying said reference value used for said judging step with respect to the increase of said evaluative value for focusing, depending on a gain of said automatic gain control circuit.

Claim 16

An auto focus control method claimed in claim 9, further comprising: inputting a picture image signal from a photographing unit of said camera via an automatic gain control circuit; further amplifying a picture image signal from said automatic gain control circuit, wherein said detecting step detects said evaluative value for focusing from a picture image signal amplified by said amplifier; and varying said reference value used for said judging step with respect to the increase of said evaluative value for focusing, depending on a gain of said amplifying step.

Claim 17

An auto focus control method claimed in claim 9, wherein said determining step includes performing multi-divided light measurement.

Claim 18

An auto focus control device claimed in claim 15, further comprising: inputting a picture image signal from a photographing unit of said camera via an automatic gain control circuit; further amplifying a picture image signal from said automatic gain control circuit, wherein said detecting step detects said evaluative value for focusing from a picture image signal amplified by said further amplifying step; reducing a gain of said further amplifying step, depending on a gain of said automatic gain control circuit; varying said reference value used for said judging step with respect to the increase of said-evaluative value for focusing, depending on at least one of an opening degree of an iris, the gain of said automatic gain control circuit, and the gain of said amplifier; detecting a brightness of the object, wherein said brightness is different from said evaluative value for focusing; detecting a difference in brightness of the object when said evaluative value for focusing is a maximum and the brightness of said object when said evaluative value for focusing is a minimum; deciding if said detected difference in brightness is not within a predetermined level; and restarting an auto focus process when said deciding step determines said detected difference in brightness to be not within said predetermined level, wherein said positioning step maintains said focus lens at a point where said evaluative value for focusing becomes a maximum when said deciding step determines said detected difference in brightness to be within said predetermined level.