FOCAL POINT DETECTION DEVICE AND CAMERA SYSTEM

• US 20100080547A1
• Filed: 09/23/2009
• Published: 04/01/2010
• Est. Priority Date: 09/26/2008
• Status: Active Grant

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Corporation
• Inventors: Yanada, Takashi
• Granted Patent: US 8,175,450 B2
• Time in Patent Office: Days
• US Class Current: 396/101
• CPC Class Codes: G03B 13/34 Power focusing

Abstract

A focal point detection device includes: a rate conversion section which converts a transmission rate of an image signal, which is associated with a subject image imaged via an imaging lens on a part of a receiving surface of an imaging device, such that the image signal input to the rate conversion section at a first transmission rate is output from the rate conversion section at a second transmission rate that is slower than the first transmission rate; a filter which extracts a frequency component from the image signal output at the second transmission rate from the rate conversion section; and an evaluation value calculation section which calculates an evaluation value of a focus state of the imaging lens, based on a signal of the frequency component that is extracted by the filter.

Claims

1. A focal point detection device comprising:

a rate conversion section which converts a transmission rate of an image signal, which is associated with a subject image imaged via an imaging lens on a part of a receiving surface of an imaging device, such that the image signal input to the rate conversion section at a first transmission rate is output from the rate conversion section at a second transmission rate that is slower than the first transmission rate;

a filter which extracts a frequency component from the image signal output at the second transmission rate from the rate conversion section; and

an evaluation value calculation section which calculates an evaluation value of a focus state of the imaging lens, based on a signal of the frequency component that is extracted by the filter.

2. The focal point detection device according to claim 1,

wherein the rate conversion section includes a memory that stores the image signal, and

the rate conversion section performs writing of the image signal to the memory at a timing that is defined by a first clock corresponding to the first transmission rate, and performs reading of the image signal from the memory at a timing that is defined by a second clock corresponding to the second transmission rate.

3. The focal point detection device according to claim 1,

wherein the rate conversion section includes a memory that stores the image signal, and

the rate conversion section of timings that are defined by a predetermined clock, performs writing of the image signal to the memory at a timing corresponding to the first transmission rate, and performs reading of the image signal from the memory at a timing corresponding to the second transmission rate.

4. A focal point detection device comprising:

a decimation section that outputs a second image signal in which a part from a first image signal associated with a subject image imaged via an imaging lens on a receiving surface of an imaging device is eliminated;

a filter which extracts a frequency component from the second image signal output from the decimation section; and

an evaluation value calculation section which calculates an evaluation value of a focus state of the imaging lens, based on a signal of the frequency component that is extracted by the filter.

5. The focal point detection device according to claim 4, further comprising

a luminance signal generation section that generates a luminance signal from the first image signal,

wherein the decimation section outputs as the second image, a signal in which a part from the luminance signal is eliminated.

6. The focal point detection device according to claim 4,

wherein a Bayer filter in which color filters of a plurality of colors are arranged in the Bayer arrangement, is attached to the light receiving surface of the imaging device,

and the decimation section outputs as the second image, a signal in which a signal corresponding to a predetermined color is eliminated from the first image signal constituted by a signal corresponding to the plurality of colors associated with the subject image imaged via the imaging lens on the receiving surface of the imaging device. device;

7. A camera system comprising:

an imaging lens which images a subject image on a light receiving surface of an imaging

a first focal point detection device, comprising;

a rate conversion section which converts a transmission rate of an image signal, which is associated with a subject image imaged via an imaging lens on a part of a receiving surface of an imaging device, such that the image signal input to the rate conversion section at a first transmission rate is output from the rate conversion section at a second transmission rate that is slower than the first transmission rate;

a filter which extracts a frequency component from the image signal output at the second transmission rate from the rate conversion section; and

an evaluation value calculation section which calculates an evaluation value of a focus state of the imaging lens, based on a signal of the frequency component that is extracted by the filter;

a second focal point detection device, comprising;

a decimation section that outputs a second image signal in which a part from a first image signal associated with a subject image imaged via an imaging lens on a receiving surface of an imaging device is eliminated;

a filter which extracts a frequency component from the second image signal output from the decimation section; and

an evaluation value calculation section which calculates an evaluation value of a focus state of the imaging lens, based on a signal of the frequency component that is extracted by the filter;

a selection section which selects either one of first or second two focal point detection devices; and

a lens driving section which drives the imaging lens so as to adjust a focal position, based on the evaluation value output from the selected focal point detection device.