Focus detection device

• US 20060055813A1
• Filed: 09/13/2005
• Published: 03/16/2006
• Est. Priority Date: 09/14/2004
• Status: Active Grant

• Current Assignee: PENTAX RICOH IMAGING COMPANY, LTD.
• Original Assignee: Pentax Corporation (Hoya Corporation)
• Inventors: Iwamoto, Shigeru, Nakata, Masahiro
• Granted Patent: US 7,589,764 B2
• Time in Patent Office: Days
• US Class Current: 348/345
• CPC Class Codes: G02B 7/28 Systems for automatic generation of focusing signals
• CPC Class Codes: H04N 23/672 based on the phase difference signals
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation
• CPC Class Codes: H04N 23/745 Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination

Abstract

A focus detection device includes an AF sensor which converts received object light into electrical charges, integrates the electrical charges, and outputs the integrated electrical charges as a video signal in pixel units; a photometering sensor which converts received light into an electrical signal to output the electrical signal as a photometering signal; a flicker repetition period determining device for determining a flicker repetition period of the received object light from fluctuations of the photometering signal of the photometering sensor; and a controller which causes the AF sensor to start integrating the electrical charges in synchronization with the flicker repetition period.

Claims

1. A focus detection device comprising:

an AF sensor which converts received object light into electrical charges, integrates said electrical charges, and outputs said integrated electrical charges as a video signal in pixel units;

a photometering sensor which converts received light into an electrical signal to output said electrical signal as a photometering signal;

a flicker repetition period determining device for determining a flicker repetition period of said received object light from fluctuations of said photometering signal of said photometering sensor; and

a controller which causes said AF sensor to start integrating said electrical charges in synchronization with said flicker repetition period.

2. The focus detection device according to claim 1, wherein said flicker repetition period determining device detects bottom values of said photometering signal of said photometering sensor, an output level of which fluctuates periodically, to determine said flicker repetition period from a time interval between said detected bottom values.

3. The focus detection device according to claim 2, wherein said controller sets an integration cycle reference point, at which a predetermined period of time elapses when each said bottom values is detected, and causes said AF sensor to start integrating said electrical charges upon an elapsed time from said integration cycle reference point reaching an integer multiple of said flicker repetition period determined by said flicker repetition period determining device.

4. The focus detection device according to claim 1, wherein said flicker repetition period determining device detects peak values of said photometering signal of said photometering sensor, an output level of which fluctuates periodically, to determine said flicker repetition period from an interval between said detected peak values.

5. The focus detection device according to claim 4, wherein said controller sets an integration cycle reference point in time at which a predetermined period of time elapses from the moment at which each said peak values is detected, wherein said controller causes said AF sensor to start integrating said electrical charges upon an elapsed time from said integration cycle reference point reaching an integer multiple of said flicker repetition period determined by said flicker repetition period determining device.

6. The focus detection device according to claim 1, wherein said flicker repetition period determining device detects points in time at which said photometering signal of said photometering sensor, an output level of which fluctuates periodically, reaches a predetermined threshold value to determine said flicker repetition period from a time interval between said points.

7. The focus detection device according to claim 6, wherein said controller sets an integration cycle reference point in time at which a predetermined period of time elapses from the moment at which each said points is detected, wherein said controller causes said AF sensor to start integrating said electrical charges upon an elapsed time from said integration cycle reference point reaching an integral multiple of said flicker repetition period determined by said flicker repetition period determining device.

8. The focus detection device according to claim 2, wherein said flicker repetition period determining device determines that a flicker frequency of said received object light is 50 Hz in the case where said time interval between said detected bottom values is greater than a predetermined time interval, and that said flicker frequency of said received object light is 60 Hz in the case where said time interval between said detected bottom values is one of equal to and smaller than said predetermined time interval.

9. The focus detection device according to claim 4, wherein said flicker repetition period determining device determines that a flicker frequency of said received object light is 50 Hz in the case where said interval between said detected peak values is greater than a predetermined interval, and that said flicker frequency of said received object light is 60 Hz in the case where said interval between said detected peak values is one of equal to and smaller than said predetermined interval.

10. The focus detection device according to claim 6, wherein said flicker repetition period determining device determines that a flicker frequency of said received object light is 50 Hz in the case where said time interval between said detected points is greater than a predetermined time interval, and that said flicker frequency of said received object light is 60 Hz in the case where said time interval between said detected points is one of equal to and smaller than said predetermined time interval.

11. The focus detection device according to claim 1, wherein said AF sensor comprises CCD line sensors.

12. The focus detection device according to claim 1, wherein said photometering sensor comprises a multi-zone photometering IC.

13. The focus detection device according to claim 1, wherein said focus detection device is incorporated in an autofocus camera.

14. A focus detection device comprising:

a phase-difference AF sensor;

a photometering sensor;

a flicker repetition period determining device for determining a flicker repetition period of object light received by said phase-difference AF sensor from fluctuations of an output level of said photometering sensor; and

a controller which causes said phase-difference AF sensor to start performing an integration operation thereof in synchronization with said flicker repetition period.