Focus detecting device for use with cameras

• US 4,636,624 A
• Filed: 01/10/1984
• Issued: 01/13/1987
• Est. Priority Date: 01/10/1983
• Status: Expired due to Term

• Current Assignee: Minolta Camera Kabushiki Kaisha
• Original Assignee: Minolta Camera Kabushiki Kaisha
• Inventors: Hamada, Masataka, Ishida, Tokuji
• Primary Examiner(s): Nelms, David C.
• Application Number:
  US06/570,012
• Time in Patent Office: 1,099 Days
• Field of Search: 250/201, 250/204, 250/209, 250/578, 356/1, 356/4, 354/406, 354/407, 354/408
• US Class Current: 250/201.8
• CPC Class Codes: G02B 7/34 using different areas in a pupil plane

Abstract

A focus detecting device is provided with first and second line sensors and first and second image forming lenses which are located behind a predetermined focal plane of the objective lens to receive the object lights for forming first and second images on the first and second line sensors, respectively. The image signal generated by the first line sensor is divided into a plurality of block signals each consisting of a predetermined number of picture element outputs and each block signal is compared with groups of picture element outputs of the second line sensor, with the groups shifted sequentially, to find a group which best coincides therewith and the distance between the first and second images on the line sensors is calculated in accordance with the shift position of the group thus determined, for calculation of the amount and direction of defocus of the object image on the focal plane. The calculated distance between the first and second images may be corrected in accordance with manual adjustment of adjustable means and magnification data of the first and second images stored in storage means.

Claims

1. A focus detecting device for a camera having an objective lens with an optical axis, comprising:

optical means for receiving light from an object which has passed through said objective lens at two portions of said objective lens distant from the optical axis of said objective lens, to form first and second object images in such a manner that the distance between said first and second object images in a direction perpendicular to said optical axis varies with the focus condition of an object image formed by said objective lens on its predetermined focal plane equivalent to a film exposure plane;

first and second line sensors disposed to receive said first and second object images for generating first and second image signals corresponding to the light intensity distributions of said first and second object images on said first and second line sensors, respectively, each of said line sensors having a plurality of picture element and said first and second image signals being the collective of picture element outputs of said first and second line sensors, respectively;

signal dividing means for dividing said picture element outputs of said first line sensor into a plurality of blocks such that the number of the picture element outputs belonging to each of said blocks is smaller than the number of said picture element outputs of said second line sensor;

correlation calculating means for calculating correlations represented by an equation ##EQU25## wherein L_k+ni represents the (k+ni)-th picture element output of said first line sensor, R_k+j-1 represents the (k+j-1)-th picture element output of said second line sensor, j represents the number of shifts, mi represents a number inherent to the i-th block, and ni represents a number inherent to the i-th block and varying with the value of i;

best correlation finding means for finding a best correlation having a minimum value among the correlations Hi(j) for each of said blocks;

image distance calculating means for determining which of the best correlations found by said best correlation finding means is smallest and calculating the distance between said first and second images on said first and second line sensors in accordance with the number of shifts j which provides the best correlation; and

defocus amount calculating means for calculating the amount of defocus of said object image with respect to said predetermined focal plane in accordance with the distance calculated by said distance calculating means.

2. A focus detecting device as defined in claim 1, wherein said optical means includes first and second image forming lenses for relaying said object image on said predetermined focal plane to form said first and second object images on said first and second line sensors, respectively.

3. A focus detecting device as defined in claim 1, further comprising manually adjustable means for correcting the distance calculated by said distance calculating means in accordance with manual adjustment thereof.

4. A focus detecting device as defined in claim 3, wherein said manually adjustable means includes a semi-fixed resistor.

5. A focus detecting device as defined in claim 1, further comprising storage means for storing magnification data α

which are different from one another in dependence upon the distance between said first and second object images on said first and second line sensors, said defocus amount calculating means is adapted to calculate the amount of defocus in accordance with the distance calculated by said image distance calculating means and corrected by the magnification data α

from said storage means corresponding to the calculated distance.

6. A focus detecting device as defined in claim 1, wherein said first and second line sensors include first and second CCDs respectively, said first and second CCDs have a plurality of picture elements storing electric charge in accordance with the intensity of light incident thereon and a transfer section receiving the electric charges stored in said picture elements to transfer the same for formation of said first and second image signals, respectively.

7. A focus detecting device as defined in claim 6, further comprising a CCD driver for driving said first and second CCDs and focus detection initiating means for making said focus detecting device operative, said CCD driver including a transfer pulse generator for generating transfer pulses which cause said transfer section to transfer the electric charges received thereby and means for controlling the period of said transfer pulses in such a manner that the period of said transfer pulses generated during an initializing operation of said CCDs immediately after said focus detection device is made operative is shorter than that of said transfer pulses generated after the initializing operation of said first and second CCDs.

8. A focus detecting device as defined in claim 7, wherein said first and second CCDs are formed on a common chip as a single CCD.

9. A focus detecting device for a camera having an objective lens with an optical axis, comprising:

optical means for receiving light from an object which has passed through said objective lens at two portions of said objective lens distant from the optical axis of said objective lens, to form first and second object images in such a manner that the distance between said first and second object images in a direction perpendicular to said optical axis varies with the defocus condition of an object image formed by said objective lens on its predetermined focal plane equivalent to a film exposure plan;

first and second line sensors disposed to receive said first and second object images for generating first and second image signals corresponding to the light intensity distributions of said first and second object images on said first and second line sensors, respectively, each of said first and second line sensors having a plurality of picture elements and said first and second image signals being the collective of picture element outputs of said first and second line sensors, respectively;

difference output producing means for producing first and second difference outputs which are represented by equations l_i =L_i -L_i+p and r_i =R_i -R_i+p, respectively, wherein L_i, L_i+p represent the i-th and (i+tp)-th picture element outputs of said first line sensor, R_i, R_i+p represent the i-th and (i+p)-th picture element outputs of said second line sensor and p represents a number other than zero;

signal dividing means for dividing said first difference outputs into a plurality of blocks such that the number of said first difference outputs belonging to each of said blocks is smaller than that of said second difference output;

correlation calculating means for calculating correlations represented by an equation ##EQU26## wherein l_k+ni represents the (k+ni)-th first difference output, r_k+j-1 represents the (k+j-11)-th second difference output, j represents the number of shifts, mi represents a number inherent to the i-th block, and ni represents a number inherent to the i-th block and varying with the value of i;

best correlation finding means for finding a best correlation having a minimum value among the correlations Hi (j) for each of said blocks;

image distance calculating means for determining which of the best correlations found by said best correlation finding means is smallest and calculating the distance between said first and second images on said first and second line sensors in accordance with the number of shifts j which provides the best correlation, and

defocus amount calculating means for calculating the amount of defocus of said object image with respect to said predetermined focal plane in accordance with the distance calculated by said distance calculating means.

10. A focus detecting device as defined in claim 9, wherein said optical means includes first and second image forming lenses for relaying said object image on said predetermined focal plane to form said first and second object images on said first and second line sensors, respectively.

11. A focus detecting device as defined in claim 9, further comprising storage means for storing magnification data α

which are different from one another in dependence upon the distance between said first and second object images formed on said first and second line sensors, said defocus amount calculating means is adapted to calculate the amount of defocus in accordance with the distance calculated by said image distance calculating means and corrected by the magnification data α

from said storage means corresponding to the calculated distance.

12. A focus detecting device for a camera having an objective lens with an optical axis, comprising:

optical means for receiving light from an object which has passed through said objective lens at two portions of said objective lens distant from the optical axis of said objective lens, to form first and second object images in such a manner that the distance between said first and second object images in a direction perpendicular to said optical axis varies with the focus condition of an object image formed by said objective lens at its predetermined focal plane equivalent to a film exposure plane;

first and second line sensors disposed to receive said first and second object images for generating first and second image signals corresponding to the light intensity distributions of said first and second object images on said first and second line sensors, respectively, each of said line sensors having a plurality of picture elements and said first and second image signals being the collective of picture element outputs of said first and second line sensors, respectively;

correlation calculating means for calculating correlations between the picture element outputs of said first and second line sensors while repeatedly shifting the picture element outputs of said second line sensor relative to those of said first line sensor to provide a plurality of correlations, the number of which is identical with the number of the shifts;

best correlation finding means for finding a best correlation having a minimum value among the plurality of correlations;

image distance calculating means for calculating the distance between said first and second object images on said first and second line sensors in accordance with the number of the shifts which provides the best correlation found by said best correlation finding means;

manually adjustable means for correcting the distance calculated by said distance calculating means in accordance with manual adjustment thereof; and

defocus amount calculation means for calculating the amount of defocus of said object image formed by said objective lens on its predetermined focal plane, in accordance with the calculated distance thus corrected.

13. A focus detecting device as defined in claim 12, wherein said optical means includes first and second image forming lenses for relaying said object image on said predetermined focal plane to form said first and second object images on said first and second line sensors respectively.

14. A focus detecting device as defined in claim 13, wherein said manually adjustable means includes a semi-fixed resistor.

15. A focus detecting device for a camera having an objective lens with an optical axis, comprising:

optical means for receiving light from an object having passed through said objective lens at two portions of said objective lens distant from the optical axis of said objective lens, to form first and second object images in such a manner that the distance between said first and second object images in a direction perpendicular to said optical axis varies with the focus condition of an object image formed by said objective lens on its predetermined focal plane equivalent to a film exposure plane;

first and second line sensors disposed to receive said first and second object images for generating first and second image signals corresponding to the light intensity distributions of said first and second object images on said first and second line sensors, each of said line sensors consisting of a CCD which includes a plurality of picture elements storing electric charge in accordance with the intensity of light incident thereon and a transfer section receiving the electric charges stored in said picture elements to transfer the same for formation of said first and second image signals as the collective of picture element output of said first and second line sensors, respectively;

focus detection initiating means for making said focus detecting device operative;

a driver means for driving said line sensors, said driver means including a transfer pulse generator for generating transfer pulses which cause said transfer section to transfer the electric charges received thereby and means for controlling the period of said transfer pulses in such a manner that the period of transfer pulses generated during an initializing operation of said CCDs inmediately after said focus detecting device is made operative is shorter than that of said transfer pulses generated after the initializing operation of said CCDs;

correlation calculating means for calculating correlations between the picture element outputs of said first and second line sensors while repeatedly shifting the picture element outputs of said second line sensor relative to those of said first line sensor to provide a plurality of correlations, the number of which is identical with the number of the shifts;

best correlation finding means for finding a best correlation having a minimum value among the plurality of correlations;

image distance calculating means for calculating the distance between said first and second object images on said first and second line sensors in accordance with the number of the shifts which provides the best correlation found by said best correlation finding means; and

defocus amount calculation means for calculating the amount of defocus of said object image on said predetermined focal plane in accordance with the distance calculated by said distance calculating means.

16. A focus detecting device as defined in claim 15, wherein said first and second CCDs are formed on a common chip as a single CCD.

17. A focus detecting device as defined in claim 15, wherein said focus detection initializing means includes a manuable actuatable switch.

18. A focus detecting device for a camera having an objective lens for forming an image of an object, comprising:

optical means for forming displaced first and second object images so that the distance between the first and second object images vary with the focus condition of the object image formed by the objective lens;

first and second sensors positioned to receive the first and second object images for generating first and second image signals corresponding to the position of the object images on the first and second sensors, respectively, each of the sensors include a plurality of individual sensing elements capable of providing individual output signals;

signal dividing means for dividing the first and second image signals into a predetermined number of block signals including a predetermined number of output signals of the individual sensing elements;

comparison means for comparing the block signals of the first image signals with the output of the second signals to determine a matching of a least one of a plural number of first image block signals with at least one of a second block signal;

focus detecting means for determining the focus condition of the objective lens relative to the position of the first and second images on the first and second sensors; and

means for manually adjusting the displacement between the first and second images on the first and second sensors to calibrate the focus detecting device.

19. A focus detecting device for a camera having an objective lens for forming an image of an object, comprising:

optical means for forming displaced first and second object images so that the distance between the first and second object images vary with the focus condition of the object image formed by the objective lens;

first and second sensors positioned to receive the first and second object images for generating first and second image signals corresponding to the position of the object images on the first and second sensors, respectively, each of the sensors includes a plurality of individual sensing elements capable of providing individual output signals;

driver circuit means for initiating an enabling state for the first and second sensors and for transferring an image signal from the first and second sensors including a pulse generator for generating transfer pulses to the individual sensing elements and means for controlling the timing period of the transfer pulses so that the period of the transfer pulses during the initiation of the enabling state are shorter than the period of the transfer pulses subsequently generated to transfer the image signal for focus detection;

signal dividing means for dividing the first and second image signals into a predetermined number of block signals including a predetermined nunber of output signals of the individual sensing elements;

comparison means for comparing the block signals of the first image signals with the output of the second signals to determine a matching of a least one of a plural number of first image block signals with at least one of a second block signal; and

focus detecting means for determining the focus condition of the objective lens relative to the position of the first and second images on the first and second sensors.

20. A focus detecting device for a camera having an objective lens, comprising:

optical means for forming first and second object images so that the distance between said first and second object images vary with the focus condition of an object image formed by said objective lens on a predetermined focal plane equivalent to a film exposure plane;

first and second line sensors positioned to receive said first and second object images for generating first and second image signals corresponding to the position of the object images on said first and second line sensors, respectively, each of said line sensors having a plurality of picture elements and said first and second image signals representing picture element outputs of said first and second line sensors respectively, said first and second line sensors include first and second CCDs respectively, said picture elements of said first and second CCDs accumulating an electric charge in accordance with the intensity of light incident thereon;

transfer means for receiving the electric charges from in said picture elements to transfer the same for formation of said first and second image signals, respectively;

signal dividing means for dividing said first and second images signals into a plurality of block signals, each comprising a predetermined number of picture element outputs of said respective line sensor;

comparison means for comparing each of said first line sensor block signals with said block signals of said picture element outputs of said second line sensor, with said picture elements of at least said first line sensor being varied for each comparison cycle;

coincidence finding means for finding, for each of said block signals, one of said groups from one sensor which provides the most appropriate match to a group in said other sensor;

image distance calculating means for determining which of the groups found from all of said block signals by said coincidence finding means is most opposite for subsequently calculating the distance between said first and second object images on said first and second line sensors; and

defocus amount calculating means for calculating the amount of defocus of said object image with respect to said predetermined focal plane in accordance with the distance calculated by said distance calculating means.

21. A focus detecting device as defined in claim 20, wherein said optical means includes first and second image forming lenses for relaying said object image on said predetermined focal plane to form said first and second object images on said first and second line sensors, respectively.

22. A focus detecting device as defined in claim 20 further comprising manually adjustable means for correcting the distance calculated by said distance calculating means in accordance with a manual adjustment thereof.

23. A focus detecting device as defined in claim 22, wherein said manually adjustable means includes a semi-fixed resistor.

24. A focus detecting device as defined in claim 20, further comprising storage means for storing predetermined magnification data which are different from one another in dependence upon the distance between said first and second object images on said first and second line sensors, said defocus amount calculating means is adapted to calculate the amount of defocus in accordance with the distance calculated by said image distance calculating means and corrected by the magnification data from said storage means corresponding to the calculated distance.

25. A focus detecting device as defined in claim 20, wherein said first and second line sensors include first and second CCDs, respectively, said first and second CCDs have a plurality of picture elements capable of storing an electric charge is accordance with the intensity of light incident thereon and a transfer section for receiving the electric charges stored in said picture elements and to transfer the same for formation of said first and second image signals, respectively.

26. A focus detecting device as defined in claim 25, further comprising a CCD driver means for driving said first and second CCDs, a focus detection initiating means for making said focus detecting device operative, said CCD driver means includes a transfer pulse generator for generating transfer pulses which cause said transfer section to transfer the electric charges received thereby and means for controlling the period of said transfer pulses in such a manner that the period of said transfer pulses generated during an initializing operation of said CCDs immediately after said focus detection device is made operative is shorter than that of said transfer pulses generated after the initializing operation of said first and second CCDs.

27. A focus detecting device as defined in claim 26, wherein said first and second CCDs are formed on a common chip.