Phase-difference detector using an analog arithmetic correlation device

• US 5,068,738 A
• Filed: 03/10/1989
• Issued: 11/26/1991
• Est. Priority Date: 03/10/1988
• Status: Expired due to Term

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Miida, Takashi
• Primary Examiner(s): Orsino, Joseph A.
• Assistant Examiner(s): Jackson, Jill
• Application Number:
  US07/321,851
• Time in Patent Office: 991 Days
• Field of Search: 354/408, 250/201 PF, 250/201.8, 358/227
• US Class Current: 348/345
• CPC Class Codes: G02B 7/34 using different areas in a pupil plane

Abstract

A phase-difference detector for use with an auto-focus detecting apparatus of a camera, the detector is capable of performing an arithmetic correlation process for detecting a phase-difference at a high speed with high accuracy. This detector uses an analog correlation arithmetic device for carrying out an analog correlation arithmetic process which generates correlative values associated with a pair of analog electric signals outputted from a pair of optical sensors. An A/D converter converts the generated correlative values outputted from the analog correlation arithmetic device into digital signals. The correlation arithmetic operation is done by directly using the analog signals generated during a photoelectric conversion, and the correlative values obtained by this computation are converted into digital signals, thereby allowing the arithmetic process to be performed at a high speed. Also, since there is substantially no rounding error incidental to a digital correlation arithmetic process because the digital conversion takes place after the correlation process, highly accurate arithmetic results can be obtained.

Claims

1. A phase-difference detector for discriminating a focusing state of an objective lens by detecting relative positions of a pair of optical images from an optical axis comprising:

sensor means for sensing the pair of optical images and sequentially outputting a first analog signal corresponding to one of the pair of optical images and a second analog signal corresponding to another of the pair of optical images at predetermined intervals in a non-destructive manner and for shifting phases of said first and second analog signals with respect to each other, said first and second analog signals being generated by photoelectric conversion of said pair of optical images;

analog correlation arithmetic means, operatively connected to said sensor means, for performing an analog correlation arithmetic operation to obtain analog correlative values from said first and second analog signals outputted from said sensor means; and

an A/D converter, operatively connected to said analog correlation arithmetic means, for converting said analog correlative values outputted from said analog correlation arithmetic means into digital correlative values;

said sensor means including,

a first light receiving unit essentially consisting of a group of photoelectric conversion elements arrayed to optically receive one of the pair of optical images and outputting first charge signals corresponding to charges induced in said first light receiving unit,

a first signal readout unit, operatively connected to said first light receiving unit, for transferring said first charge signals in a predetermined array-direction and for outputting said first analog signals corresponding to said first charge signals in parallel through floating gates,

a second light receiving unit essentially consisting of a group of photoelectric conversion elements arrayed to optically receive another of the pair of optical images and outputting second charge signals corresponding to charges induced in said second light receiving unit,

a second signal readout unit, operatively connected to said second light receiving unit, for transferring said second charge signals in a predetermined array-direction and for outputting said second analog signals corresponding to said second charge signals in parallel through floating gates, and

control means, operatively connected to said first and second signal readout units, for outputting at predetermined intervals both said first and second analog signals out of phase with each other.

2. A phase-difference detector for discriminating a focusing state of an objective lens by detecting relative positions of a pair of optical images from an optical axis comprising:

sensor means for sensing the pair of optical images and sequentially outputting a first analog signal corresponding to one of the pair of optical images and a second analog signal corresponding to another of the pair of optical images at predetermined intervals in a non-destructive manner and for shifting phases of said first and second analog signals with respect to each other, said first and second analog signals being generated by photoelectric conversion of said pair of optical images;

analog correlation arithmetic means, operatively connected to said sensor means, for performing an analog correlation arithmetic operation to obtain analog correlative values from said first and second analog signals outputted from said sensor means; and

an A/D converter, operatively connected to said analog correlation arithmetic means, for converting said analog correlative values outputted from said analog correlation arithmetic means into digital correlative values;

said analog correlation arithmetic means including,

a switched capacitor integrator including,

a plurality of capacitor elements, and

a group of switching elements for connecting

and disconnecting said capacitor element;

said switched capacitor integrator being supplied with said first and second analog signals;

said group of switching elements being controlled so as to turn ON and OFF according to a difference in magnitude between said first and second analog signals by detecting said difference in magnitude therebetween;

said analog correlative values of said first and second analog signals being computed by generating, in said switched capacitor integrator, an electric charge corresponding to an integrated value of an absolute value of said difference in magnitude between said first and second analog signals every time said first and second analog signals are out of phase.