Range finding device

• US 4,469,417 A
• Filed: 01/15/1982
• Issued: 09/04/1984
• Est. Priority Date: 09/29/1977
• 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, Ohwada, Mitsutoshi, Asano, Noriyuki
• Primary Examiner(s): Perkey, William B.
• Application Number:
  US06/339,517
• Time in Patent Office: 963 Days
• Field of Search: 354/25 R, 354/25 A, 354/25 P, 354/25 N, 354/31 F, 354/195, 354/196, 354/139, 354/149, 354/32, 318/601, 318/293, 250/201, 250/204
• US Class Current: 396/128
• CPC Class Codes: G02B 7/30 using parallactic triangle with a base line

Abstract

This invention presents a range finding device when 1st and 2nd detection images of an object are scanned by signal storing type image sensing means to obtain image scan signals, which are quantized by quantization means to produce quantized image data for said 1st and 2nd detection images. On the basis of the thus obtained quantized image data, the location within the 2nd detection images of one set of M successive elements of the 2nd detection image which is most similar to M successive elements of the 1st detection image is detected, and with the aid of the data of this location, the distance between the device and the object is determined. According to this improved device, sequence control means, which controls a series of operations for range finding, will firstly cancel the signals stored in said image sensing means as unnecessary signals, when said series of operations is initiated, and then enables proper storing of image signals in the image sensing means so as to properly control the device.

Claims

1. In a focus control system for automatically focusing objective lens means onto an object, the combination comprising:

(A) means for receiving first and second detection images of the object and for providing image signals corresponding to the first and second detection images;

(B) means for detecting, on the basis of the image signals provided by said image receiving means, the range of the object, said range detection means detecting the object range by detecting, on the basis of the image signals, the relative positional difference between corresponding image portions of the first and second detection images and providing data on the object range;

(C) means operatively associated with said objective lens means for providing data on an adjusted position of the lens means along an optical axis thereof;

(D) means for detecting, on the basis of the object range data provided by said range detection means and the data on the adjusted position of the lens means provided by said position data providing means, deviation of the adjusted position of the objective lens means from an in-focus position, at which the lens means is properly focused onto the object, said deviation detection means providing data on said deviation;

(E) means for driving the objective lens means along an optical axis of the lens means;

(F) means for controlling said driving means on the basis of the deviation data provided by said deviation detection means so as to position the objective lens means to said in-focus position, said drive control means being so arranged that it can continuously operate said driving means; and

(G) means for controlling the driving speed of said driving means on the basis of the magnitude of the deviation indicated by the deviation data, said speed control means including means for comparing the magnitude of the deviation with a predetermined threshold, and being arranged to cause said driving means to drive the lens means toward the in-focus position at a speed which is determined by the result of the comparison performed by said comparing means according to a function which provides a stepwise change between two different speed levels, said speed control means further including means for selecting the threshold.

2. The combination according to claim 1, wherein said speed control means is arranged to cause said driving means to drive the lens means at a first relatively low speed when the magnitude of the deviation is below the threshold and at a second relatively high speed when the magnitude of the deviation is above the threshold.

3. A focus control system for automatically focusing objective lens means onto an object, comprising:

(A) means for detecting deviation of the adjusted position of the objective lens means from an in-focus position at which the lens means is properly focused onto the object, said deviation detection means providing data on the deviation;

(B) means for driving the objective lens means along an optical axis of the lens means;

(C) means for controlling said driving means on the basis of the deviation data provided by said deviation detection means so as to position the objective lens means at the in-focus position; and

(D) means for controlling the driving speed of said driving means on the basis of the magnitude of the deviation indicated by the deviation data, said speed control means including means for comparing the magnitude of the deviation with a predetermined threshold, and being arranged to cause said driving means to drive the lens means toward the in-focus position at a speed which is determined by the result of the comparison performed by said comparing means according to a function which provides a stepwise change between two different speed levels, said speed control means further including means for selecting the threshold.

4. A focus control system according to claim 3, wherein said speed control means is arranged to cause said driving means to drive the lens means at a first relatively low speed when the magnitude of the deviation is below the threshold and at a second relatively high speed when the magnitude of the deviation is above the threshold.

5. An automatic focusing system for controlling an adjustable focusing means to focus on an object, which focusing means includes a movable optical element, said system comprising:

means for repetitively performing an operation for the production of an indication of the deviation between the actual position of the movable element and a required in-focus position thereof relative to the object;

means for driving the movable element so as to adjust the focusing condition of the focusing means; and

control means for controlling said driving means in accordance with the repetitively produced deviation indications, said control means including means for comparing the magnitude of the deviation with a predetermined threshold and means for selecting the threshold level, said control means being arranged to cause said driving means to move the movable element toward the in-focus position at a speed which is determined by the result of the comparison performed by said comparing means according to a function which provides a stepwise change between two different speed levels.

6. A focusing system according to claim 5, wherein said control means is arranged to cause said driving means to drive the movable element at a first relatively low speed when the magnitude of the deviation is below the threshold and at a second relatively high speed when the magnitude of the deviation is above the threshold.

7. An automatic focusing system according to claim 5, wherein said driving means comprises an electric motor coupled to drive the optical element and a motor power circuit including switching means controllable according to the result of the comparison to change the power supplied to said motor between two levels corresponding to the two speed levels.

8. An automatic focusing system according to claim 5, wherein said comparing means is arranged to compare a digital representation of the deviation with a digital representation of the threshold.

9. An automatic focusing system for controlling an adjustable focusing means to focus on an object, which focusing means includes a movable optical element, said system comprising:

means for repetitively performing an operation for the production of an indication of the deviation between the actual position of the movable element and a required in-focus position thereof relative to the object;

means for driving the movable element so as to adjust the focusing condition of the focusing means; and

control means for controlling said driving means in accordance with the repetitively produced deviation indications and being arranged to reduce the driving speed of the movable element by said driving means in a region in the vicinity of the in-focus position with respect to the driving speed in a region outside thereof, said control means including means for adjusting the speed reducing region.

10. A system for discriminating the focusing state of an image forming optical means relative to an object, comprising:

(A) first and second sensing means for respectively sensing first and second radiations emanated from the object and for respectively producing first and second electrical indications respectively indicative of distributions of the first and second radiations on said first and second sensing means, the relative positions of the first and second radiation distributions on said first and second sensing means being varied in accordance with the change in the focusing condition of the optical means relative to the object and having a predetermined relation when an in-focus condition of the optical means relative to the object is attained;

(B) detecting means for detecting, on the basis of the first and second electrical indications, the relative positions of the first and second radiation distributions on said first and second sensing means, said detecting means providing data representing said relative positions; and

(C) discriminating means for discriminating the focusing condition of the optical means relative to the object on the basis of the data representing the relative positions, said discriminating means including means for comparing the data with reference data representing the predetermined relation of the relative positions of the first and second radiation distributions on said first and second sensing means and being arranged to discriminate the focusing condition among the in-focus, near focus, and far focus conditions based on the result of the comparison.

11. A system according to claim 10, wherein each of said first and second sensing means includes a linear array of a plurality of radiation sensitive elements, and said detecting means is arranged to provide the data representing the relative positions expressed in terms of a number of elements.

12. A system according to claim 11, wherein the reference data is expressed in terms of a number of elements and representing a predetermined number of elements.

13. A system for focusing an image forming optical means relative to an object, comprising:

(A) first and second sensing means for respectively sensing first and second radiations emanated from the object and for respectively producing first and second electrical indications respectively indicative of distributions of the first and second radiations on said first and second sensing means, the relative positions of the first and second radiation distributions on said first and second sensing means being varied in accordance with the change in the focusing condition of the optical means relative to the object and having a predetermined relation when an in-focus condition of the optical means relative to the object is attained;

(B) detecting means for detecting, on the basis of the first and second electrical indications, the relative positions of the first and second radiation distributions on said first and second sensing means, said detecting means providing data representing said relative positions;

(C) discriminating means for discriminating the focusing condition of the optical means relative to the object on the basis of the data representing the relative positions, said discriminating means including means for comparing the data with reference data representing the predetermined relation of the relative positions of the first and second radiation distributions on said first and second sensing means and being arranged to discriminate the focusing condition among the in-focus, near focus, and far focus conditions based on the result of the comparison; and

(D) adjusting means for adjusting the optical means based on the result of the discrimination performed by said discriminating means so that the relative positions of the first and second radiation distributions on the first and second sensing means substantially has the predetermined relation.

14. A system according to claim 13, wherein each of said first and second sensing means includes a linear array of a plurality of radiation sensitive elements, and said detecting means is arranged to provide the data representing the relative positions expressed in terms of a number of elements.

15. A system according to claim 14, wherein said reference data is expressed in terms of a number of elements and representing a predetermined number of elements.