Device for focus detection or distance detection

• US 4,257,705 A
• Filed: 03/20/1979
• Issued: 03/24/1981
• Est. Priority Date: 03/23/1978
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Niwa, Yukichi, Tsunekawa, Tokuichi, Hosoe, Kazuya, Masunaga, Makoto, Asano, Noriyuki, Owada, Mitsutoshi
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US06/022,368
• Time in Patent Office: 735 Days
• Field of Search: 356/1, 356/4, 354/25, 250/201
• US Class Current: 356/3.07
• CPC Class Codes: G02B 7/30 using parallactic triangle with a base line

Abstract

This invention relates to a device for focus detection or distance detection in which one or more images of a target formed by an optical system are received by photoelectric light receiving means to obtain a photoelectric output regarding the imaging condition of the image of the target and this photoelectric output is electrically processed through a processing circuit to thereby provide an electrical output representing the focus adjusted condition of the optical system with respect to the target or the distance to the target. According to the improvements of the present invention, such device is provided with projector means for illuminating a limited part of the detection view field determined by the focal length of the optical system and the dimensions of the effective light receiving surface of the photoelectric light receiving means, detection means for detecting whether or not the signal put out by the photoelectric light receiving means regarding the imaging condition of one or more images of the target is a sufficiently proper signal to ensure accurate focus detection or distance detection by the processing circuit, and control means for controlling the projector means in accordance with the detection output from the detection means. When proper detection is not ensured during the focus detection or the distance detection, the projector means is driven by the control means in accordance with the detection output of the detection means and the projection image of the projected light formed thereby on the target is utilized to effect focus detection or distance detection.

Claims

1. A system comprising:

(A) means for forming one or more images of an object;

(B) means for receiving said one or more images to provide one or more electrical outputs indicative of said one or more images, said image receiving means being signal integration type image sensing means for providing, as the outputs thereof, one or more integrated image signal integrated within an integration time period;

(C) means for receiving and processing said one or more electrical outputs of said image receiving means to detect the imaging condition of said one or more images formed by said image forming means;

(D) means for locally illuminating said object to form an optical mark on said object;

(E) means for detecting whether or not said one or more electrical outputs of said image receiving means are sufficiently proper outputs to ensure accurate imaging condition detection by said processing means, said detection means producing a detection signal when said one or more electrical outputs of the image receiving means are outputs which cannot ensure accurate imaging condition detection by the processing means;

(F) said system further comprising means for controlling the integration time period of said image sensing means, said control means producing a control signal indicative of the integration time period of the sensing means;

(G) means responsive to said detection signal produced by said detection means to actuate said illuminating means, said actuating means being responsive to said control signal produced by said control means to actuate said illuminating means for a time period corresponding to the integration time period of said image sensing means in accordance with said control signal and said detection signal produced by said detection means.

2. The system according to claim 1, wherein

said image forming means is arranged to form first and second images of the object with a relative positional difference corresponding to the distance to the object;

said image receiving means is arranged to receive said first and second images to provide, as the outputs thereof, image element signal on each image element of the first and second images;

said processing means includes;

quantization means for quantizing the image element signal generated for each image element by said image sensing means; and

circuit means to receive quantized data from said quantization means and detect, on the basis of said quantized data, the relative positional difference between M successive image elements of the first image and M successive image elements of the second image corresponding to the M successive image elements of the first image so as to provide for data regarding to the range of the object;

said detection means includes;

quantization state detection means for detecting whether or not among quantized data from said quantization means, all of the quantized data regarding at least said M successive image elements of the first image are one and the same value, said quantization state detection means producing a detection signal when all of the quantized data regarding at least the M successive image elements of the first image are one and the same value; and

said actuating means is reponsive to said detection signal produced by said quantization state detection means to actuate said illuminating means in accordance with said detection signal.

3. The system according to claim 2, wherein said quantization means converts the image element signal generated for each image element by said image sensing means into binary data of "1" or "0", on the basis of a predetermined threshold level, and said quantization state detection means detects whether or not all of the binary data at least on said M successive image elements of the first image among binary data from said quantization means are "1" or "0" and produces said detection signal when it detects that all of the binary data at least on the M successive image elements of the first image are "1" or "0".

4. The system according to claim 2 or 3, wherein

said circuit means in said processing means includes:

a detection circuit for detecting, within the second image, one set of M successive image elements corresponding to the M successive image elements of the first image by the successive comparison of the quantized data on the M successive image elements of the first image with the quantized data on each of different sets of M successive image elements of the second image; and

said detection means further includes;

means for evaluating, on the basis of the quantized data, the degree of similarity to the M successive image elements of the first image of said one set of M successive image elements of the second image which has been deemed to correspond with the M successive image elements of the first means by said detection circuit, said evaluating means compares said degree of similarity with a predetermined constant degree and produces a detection signal when the degree of similarity is lower than said predetermined constant degree; and

said actuating means is also responsive to the detection signal produced by said evaluating means to actuate said illuminating means in accordance with at least one of said detection signal produced by said evaluating means and said detection signal produced by said quantization state detection means.

5. The system according to claim 4, wherein said detection circuit in said circuit means includes:

a coincidence detection circuit for detecting, on element by element basis, the coincidence of the quantized data on the M successive image elements of the first image with the quantized data on each set of M successive image elements of the second image;

a counter circuit for obtaining, on the basis of the quantized data, the degree of similarity of each set of the M successive image elements of the second image to the M successive image elements of the first image by counting the coincidence output of said coincidence detecting circuit; and

a memorizing circuit for memorizing the maximum value of the counted value of said counter circuit;

said evaluating means evaluates the degree of similarity by comparing said maximum value of the counted value memorized in said memorizing circuit with a predetermined constant value and produces said detection signal when said maximum value is below said predetermined constant value.

6. The system according to claim 1, wherein

said image forming means is arranged to form first and second images of the object with a relative positional difference corresponding to the distance to the object;

said image receiving means is arranged to receive said first and second images to provide, as the outputs thereof, image element signal on each image element of the first and second images;

said processing means includes;

quantization means for quantizing the image element signal generated for each image element by said image sensing means; and

circuit means to receive quantized data from said quantization means and detect, on the basis of said quantized data, the relative positional difference between M successive image elements of the first image and M successive image elements of the second image corresponding to the M successive image elements of the first image so as to provide with data regarding the range of the object, said circuit means having detection circuit for detecting, within the second image, one set of M successive image elements corresponding to the M successive image elements of the first image by the successive comparison of the quantized data on the M successive image elements of the first image with the quantized data on each of different sets of M successive image elements of the second image; and

said detection means includes;

means for evaluating, on the basis of the quantized data, the degree of similarity to the M successive image elements of the first image of said one set of M successive image elements of the second image which has been deemed to correspond with the M successive image elements of the first means by said detection circuit, said evaluating means compares said degree of similarity with a predetermined constant degree and produces a detection signal when the degree of similarity is below said predetermined constant degree; and

said actuating means is responsive to the detection signal produced by said evaluating means to actuate said illuminating means in accordance with said detection signal produced by said evaluating means.

7. The system according to claim 6, wherein said detection circuit in said circuit means includes:

a coincidence detection circuit for detecting, on element by element basis, the coincidence of the quantized data on the m successive image elements of the first image with the quantized data on each set of M successive image elements of the second image;

a counter circuit for obtaining, on the basis of the quantized data, the degree of similarity of each set of the M successive image elements of the second image to the M successive image elements of the first image by counting the coicidence output of said coincidence detecting circuit; and

a memorizing circuit for memorizing the maximum value of the counted value of said counter circuit;

said evaluating means evaluates the degree of similarity by comparing said maximum value of the counted value memorized in said memorizing circuit with a predetermined constant value and produces said detection signal when said maximum value is below said predetermined constant value.

8. The system according to claim 2 wherein,

said image receiving means is signal integration type image sensing means for providing, as the outputs thereof, integrated image element signals integrated within an integration time period;

said system further comprises means for controlling the integration time period of said image sensing means, said control means producing a control signal indicative of the integration time period of the sensing means; and

said actuating means is responsive to said control signal produced by said control means to actuate said illuminating means for a time period corresponding to the integration time period of said image sensing means in accordance with said control signal and said detection signal produced by said detection means.

9. A range detecting device for detecting the range of an object, comprising:

(A) image sensing means positioned to receive first and second detection images of said object and to provide an image element signal on each image element of the first and second detection images;

(B) quantization means for quantizing the image element signal generated for each image element by said image sensing means;

(C) circuit means to receive quantized data from said quantization means and detect, on the basis of said quantized data, the relative positional difference between M successive image elements of the first detection image and M successive image elements of the second detection image corresponding to the M successive image elements of the first detection image so as to provide for data regarding the range of the object;

(D) quantization state detection means for detecting whether or not among quantized data from said quantization means, all of the quantized data regarding at least said M successive image elements of the first detection image are one and the same value, said quantization state detection means producing a detection signal when it detects that all of the quantized data at least on the M successive image elements of the first detection image are one and the same value;

(E) illuminating means for locally illuminating said object to form an optical mark on said object; and

(F) actuating means responsive to said detection signal produced by said quantization state detection means to actuate said illuminating means.

10. The device according to claim 9, wherein said quantization means converts the image element signal generated for each image element by said image sensing means into binary data of "1" or "0", on the basis of a predetermined threshold level, and said quantization state detection means detects whether or not all of the binary data at least on said M successive image elements of the first image among binary data from said quantization means are "1" or "0" and produces said detection signal when it detects that all of the binary data at least on the M successive image elements of the first image are "1" or "0".

11. The device according to claim 9 or 10, wherein

said image sensing means is signal integration type image sensing means providing integrated image element signals integrated within an integration time period;

said device further comprises;

means for controlling the integration time period of said image sensing means, said control means producing a control signal indicative of the integration time period of the sensing means; and

said actuating means is responsive to said control signal produced by said control means to actuate said illuminating means for a time period corresponding to the integration time period of said image sensing means in accordance with said control signal and said detection signal produced by said quantization state detection means.

12. A range detecting device for detecting the range of an object, comprising:

(A) image sensing means positioned to receive first and second detection images of said object and to provide an image element signal on each image element of the first and second detection images;

(B) quantization means for quantizing the image element signal generated for each image element by said image sensing means;

(C) circuit means to receive quantized data from said quantization means and detect, on the basis of said quantized data, the relative positional difference between M successive image elements of the first detection image and M successive image elements of the second detection image corresponding to the M successive image elements of the first detection image so as to provide for data regarding the rangeof the object, the circuit means including detection means for detecting, within the second detection image, one set of M successive image elements corresponding to the M successive image elements of the first detection image by the successive comparison of the quantized data on the M successive image elements of the first detection image with the quantized data on each of different sets of M successive image elements of the second detection image;

(D) means for evaluating on the basis of the quantized data, the degree of similarlity to the M successive image elements of the first detection image of said one set of M successive image elements of the second detection image which has been deemed to correspond with the M successive image elements of the first detection means by said detection means, said evaluating means comparing said degree of similarity with a predetermined constant degree and producing a detection signal when the degree of similarity is lower than said predetermined constant degree;

(E) illuminating means for locally illuminating said object to form an optical mark on said object; and

(F) actuating means responsive to said detection signal produced by said evaluating means to actuate said illuminating means.

13. The device according to claim 12, wherein said detection means includes

a coincidence detection circuit for detecting, on element by element basis, the coicidence of the quantized data on the M successive image elements of the first image with the quantized data on each set of M successive image elements of the second image;

a counter circuit for obtaining, on the basis of the quantized data, the degree of similarity of each set of the M successive image elements of the second image to the M successive image elements of the first image by counting the coincidence output of said coincidence detecting circuit; and

a memorizing circuit for memorizing maximum value of the counted value of said counter circuit;

said evaluating means evaluates the degree of similarity by comparing said maximum value of the counted value memorized in said memorizing circuit with a predetermined constant value and produces said detection signal when said maximum value is below said predetermined constant value.

14. The device according to claim 12 or 13, wherein

said image sensing means is signal intergration type sensing means providing integrated image element signals integrated within an integration time period;

said device further comprises;

means for controlling the integration time period of said image sensing means, said control means producting a control signal indicative of the integration time period of the sensing means; and

said actuating means is responsive to said control signal produced by said control means to actuate said illuminating means for a time period corresponding to the integration time period of said image sensing means in accordance with said control signal and said detection signal produced by said evaluating means.