Distance detector using a photopotentiometer and a continuous detecting system

• US 4,445,029 A
• Filed: 04/28/1981
• Issued: 04/24/1984
• Est. Priority Date: 06/16/1980
• Status: Expired due to Term

• Current Assignee: Seiko Precision Incorporated (Seiko Group)
• Original Assignee: Seiko Koki Kabushiki Kaisha
• Inventors: Nagaoka, Shinji, Satoh, Koji
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Brophy, J. J.
• Application Number:
  US06/258,517
• Time in Patent Office: 1,092 Days
• Field of Search: 356/1, 356/4, 33/125 A, 250/201, 250/211 K, 250/363 S, 250/368
• US Class Current: 250/201.4
• CPC Class Codes: G01C 3/10 using a parallactic triangle with variable angles and a base of fixed length in the observation station, e.g. in the instrument
• CPC Class Codes: G01S 17/46 Indirect determination of position data

Abstract

A distance detector capable of measuring the distance between the range detector and an object by directing a light emitted from a light emission element to the object and receiving the reflected light and advantageously adaptable particularly to small-sized cameras.

The light reflected on the object is received by a single light-receiving element. The reflected light is condensed by a condenser and concentrated on the light-receiving element. The light-receiving element comprises an element, for example a photopotentiometric element, varying in the electric output according to the position of the light spot of the reflected light. The output of the element in the form of electric signal continuously varies in proportion to the distance between the range detector and the object.

Claims

1. A distance detector for use with a camera having a movable photographing lens movable during a focusing operation to focus an image of an object to be photographed to an image plane, the distance detector comprising:

a light emission element and an optical system both disposed on a first optical axis for radiating an object to be photographed, a condensing optical system and a semiconductor position detector both disposed on a second optical axis which is separate from said first optical axis by a base length and parallel to said first optical axis, the semiconductor position detector comprising a photodiode operable to continually produce during the focusing operation a continuous electrical output signal proportional to the spot at which the light impinges thereon which is reflected by the object along the second optical axis, and a signal processing circuit connected to continuously receive the continuous electrical output signal from said semiconductor position detector and operative to develop therefrom during the focusing operation a continuous electrical object distance signal representative of the distance between the distance detector and the object.

2. A distance detector as set forth in claim 1, including means for comparing the continuous electrical object distance signal provided by said signal processing circuit as a reference signal and a signal generated by movement of the photographing lens of the camera and responsive to a favorable comparison to stop the photographing lens at an in-focus position.

3. A distance detector as set forth in claim 1 or 2, wherein said light emission element comprises a near infra-red rays emission diode.

4. A distance detector as set forth in claim 1 or 2, including an A/D converter connected to receive the output signal of said signal processing circuit for converting the output signal into a corresponding digital signal, and means responsive to the digital signal for digitally displaying information representative of the object distance.

5. In a camera having a movable photographing lens movable during a focusing operation to focus an image of an object to be photographed on an image plane, and actuatable stopping means operative when actuated to stop the movement of the photographing lens and releasably hold the photographing lens in the stopped position:

a distance detector for detecting the distance from the camera of the object to be photographed and continually producing during the focusing operation an electrical output signal representative of the object distance, the distance detector comprising light-emitting means for emitting and directing light to the object to be photographed, and light-receiving means for concentrating the reflected light from the object and converting the concentrated light into a continual electrical object distance signal representative of the object distance, the light-receiving means comprising an elongate photodiode having electrodes at opposite end portions thereof and having an output voltage characteristic which varies in accordance with the spot between the electrodes at which the concentrated light impinges on the photodiode;

lens position signal generating means for continuously producing during the focusing operation a continual electrical lens position signal corresponding to the position of the photographing lens during its focusing movement; and

actuating means receptive of the continual object distance and lens position signals for comparing the two signals and operative in response to a favorable comparison for actuating the stopping means to thereby stop the movement of the photographing lens at a position wherein the image of the object is focused on the image plane.

6. A camera according to claim 5;

wherein the actuating means comprises a voltage comparator for comparing the voltage levels of the continual object distance and lens position signals and exhibiting a first output state in response to an unfavorable comparison and exhibiting a second output state in response to a favorable comparison.

7. A camera according to claim 5;

wherein the light-receiving means comprises a signal processing circuit connected to the electrodes of the photodiode for processing the currents flowing through the electrodes to produce the continual electrical object distance signal.

8. A camera according to claim 7;

further including an analog-to-digital converter for converting the continual electrical object distance signal into a corresponding digital signal; and

display means connected to the converter for digitally displaying information representative of the object distance.

9. A camera according to claim 5;

further including an analog-to-digital converter for converting the continual electrical object distance signal into a corresponding digital signal; and

display means connected to the converter for digitally displaying information representative of the object distance.