JPH05264891A - Range finder and camera using the same - Google Patents

Abstract

PURPOSE:To calculate an accurate focal distance in a short time without increasing the number of light projecting and light receiving elements, and to attain the miniaturization and the reduction of a cost. CONSTITUTION:When a light projecting means 2 and a light receiving means 3 are moved in a forward direction in front of an object by a scanning driving means (stepping motor) 4 which is controlled by a control circuit 6, light reflected on the object is received by the light receiving means 3 and the peak value of light intensity is detected by a peak detection circuit 8. A position where the peak value is detected is confirmed by counting the driving pulse of the scanning means 4 by a counter 7 and so on, and then, the position is stored in a storage circuit 9. The movement of the light receiving means 3 in a backward direction is stopped at the position where the peak value is detected, a distance to the object is measured by a distance calculation circuit 10. A focusing means 11 is driven so as to feed out a lens and so as to focus by a distance signal measured by such a range finder, and then, an exposure means 12 is driven so as to photograph the object.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type distance measuring device and an automatic focusing camera using the same.

[0002]

2. Description of the Related Art A method of irradiating a subject with infrared light, receiving reflected light from the subject with a PSD (position detecting element), etc., and measuring the distance to the subject by a triangulation method is widely known. There is. In this method, since infrared light is focused into a beam by a projection lens and projected, a so-called hollow phenomenon occurs when two people are lined up, and there is a problem that the background is in focus. there were. Therefore, various proposals have been made to solve this problem.

The first is a method of scanning the inside of the photographing screen,
U.S. Pat. No. 4,470,681 and JP-A-2-12441
No. 9 and so on. Both of these perform distance measurement calculation while scanning. The second method is called a multi-beam distance measuring method, and is disclosed in JP-A-62-223.
As disclosed in Japanese Patent No. 734, 3 to 5 elements for emitting infrared light are provided.

[0004]

In the above-mentioned first conventional method, the more the distance measuring points are increased during the scanning in order to prevent the hollow defect, the longer the distance measuring time of the entire stroke becomes. It has the drawback. In addition, JP-A-2-124419
In addition, in order to rotate the entire ranging unit,
It requires space and is inconvenient to go against the trend of miniaturization of cameras.

According to the above-mentioned second conventional method, Japanese Patent Laid-Open No.
As illustrated in No. 2-223734, the element for receiving light has a special shape and becomes large. Therefore, there is a problem that the distance measuring performance at high brightness becomes disadvantageous or expensive. In addition, there is a drawback that the hollowing-out phenomenon cannot be solved unless an infrared light-emitting element is used infinitely many.

Therefore, the present invention solves the above-mentioned problems, does not significantly lengthen the distance measuring time, does not increase the space, and has high brightness for any object, and prevents the hollow defect phenomenon. An object of the present invention is to provide a distance measuring device for a camera which is prevented.

[0007]

To achieve the above object, a distance measuring apparatus of the present invention comprises a light projecting means for projecting light toward a subject, and a light receiving means for receiving reflected light from the subject. A scanning unit that connects the light projecting element included in the light projecting unit and the light receiving unit included in the light receiving unit to each other to reciprocate within the photographing screen, and the peak of the reflected light intensity received during the forward movement of the light receiving unit. The peak detection circuit that detects the value, the storage circuit that stores the peak value detection position, the control circuit that stops the backward movement of the light receiving unit at the peak value detection position, and the light receiving unit at the peak value detection position. And a distance calculation circuit that measures the distance to the subject when the camera is stopped.

Further, the camera of the present invention comprises the above distance measuring device, a focusing device for focusing the lens by moving the lens according to a distance signal from the distance measuring device, and an exposure device for photographing a subject.

[0009]

An embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 2, on one substrate 1, a light projecting element (hereinafter referred to as “IRED”) 2b that passes a fixed light projecting lens 2a and projects infrared rays toward a subject, and a light projecting element from the subject. A light receiving element (hereinafter referred to as “PSD”) 3b that receives light through a fixed light receiving lens 3a is supported at a predetermined interval. The substrate 1 is driven by a stepping motor 4 (shown in FIG. 1) which is a scanning means so as to reciprocate left and right and front and back by a guide pin and a guide groove (not shown). As shown in FIG. 3, the PSD 3b has currents i1 and i2 flowing from a pair of electrodes according to its light receiving position (illustrated by hatching).

As shown in FIGS. 1 and 6, the stepping motor 4 is controlled by a release switch 5 by a control circuit (hereinafter referred to as “CPU”) 6 which is turned on, and its drive pulse is counted by a counter 7. .. By the forward rotation of the motor 4, the board 1 moves from the right to the left in FIG. 2 in the forward direction, and the light emitted from the IRED 2b toward the subject moves from the left to the right in FIG. Optical scanning is performed along the scan line A. The reflected light from the subject is PS
The light is received by D3b. The currents i1 and i2 output from the PSD 3b based on the reflected light are added (i = i1 + i2
) Will be done. The photocurrent i is proportional to the light intensity, and as shown in FIG. 5, changes with time t depending on the distance between the IRED 2b and the subject. Therefore, the peak value of the photocurrent i is detected by the peak detection circuit 8. The peak value is obtained at the position of the object closest to the substrate on the scan line A, that is, at the point O (shown in FIG. 4) to which the focal length should be adjusted during imaging. The detection position of the peak value is stored in the storage circuit 9 in the form of, for example, the number of drive pulses of the stepping motor 4 (6 pulses to the position of the point O).

After the primary scanning is completed, the stepping motor 4
2 is driven in the reverse direction and the substrate 1 moves in the backward direction from the left to the right in FIG. 2, the number of drive pulses “6” which is the peak value detection position previously stored in the memory circuit 9 is detected. When the substrate 1 is returned to the position of, the motor 4 is controlled by the control circuit 6 and stops. This position is the position of the point O in FIG. 4 that captures the subject to be focused.

Here, a normal distance measuring operation is performed. In other words, the distance calculation circuit 10 calculates the distance from the current i1 and i2, which is obtained by projecting an object from the IRED 2b of the light projecting means 2 and receiving the reflected light by the PSD 3b of the light receiving means 3. (I1 -i2) / (i1 + i2)} is performed to measure the distance.

This distance signal is sent from the CPU 6 to the focusing means 11
The lens feed amount is determined in accordance with the distance signal, the lens is driven, and the in-focus state is achieved.

Finally, the CPU 6 issues an exposure command to the exposure means 12 to complete the photographing of the subject.

In order to detect the peak value by the peak detection circuit 8, it is sufficient to add the output currents i1 and i2 from the PSD 3b, so the time required for the calculation is extremely short. On the other hand, in order to obtain the distance to the subject by the distance calculation circuit 10, it is necessary to use the coefficient k based on the principle of triangulation and to calculate k × (i1 −i2) / (i1 + i2). It takes time. Therefore, if the distance calculation is performed during the scanning of the light projecting element and the light receiving element as in the prior art, it takes a long time for the distance measuring process. However, according to the present invention, the first scan can be performed in a short time by only calculating i1 + i2, and the distance calculation is performed only once in the second scan (the distance calculation at the position of the drive pulse "6" in the above embodiment). However, the time required for the distance measuring process can be shortened to about 20 to 40% of the conventional time, and the speed of the photography operation can be increased.

Although the scanning line pattern is V-shaped in the above embodiment, the shape of the guide groove may be appropriately set to make the scanning line an appropriate pattern such as a zigzag shape or an arc shape. Further, the same action and effect can be obtained by using a combination of a DC motor and an encoder instead of the stepping motor.

[0017]

According to the distance measuring apparatus of the present invention having the above-described structure, the peak value of the light intensity received during the movement of the light receiving means in the forward direction is detected, the detected position is stored, and the backward direction is detected. Since the movement is stopped at the peak value detection position and the distance to the subject is measured here, the accurate focal length can be calculated in a short time. Further, since it is not necessary to increase the number of light projecting and light receiving elements and further to rotate the entire distance measuring unit, it is possible to achieve downsizing of the camera and cost reduction.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a camera using a distance measuring device of the present invention.

FIG. 2 is a partial cross-sectional front view showing a moving configuration of a light projecting element and a light receiving element in the distance measuring device of the present invention.

FIG. 3 is a plan view of a light receiving element in the distance measuring device of the present invention.

FIG. 4 is a front view showing a scanning line of light within an imaging range and a peak position of received light intensity.

FIG. 5 is a graph showing the light intensity received by the primary scanning and the drive pulse of the step motor.

FIG. 6 is a flowchart of a photograph taking operation of the camera of the present invention.

[Explanation of symbols]

 2 light emitting means 2b light emitting element (IRED) 3 light receiving means 3b light receiving element (PSD) 4 scanning means (stepping motor) 6 control circuit 8 peak detection circuit 9 memory circuit 10 distance calculation circuit 11 focusing means 12 exposure means

Claims (2)

[Claims] 1. A light projecting means for projecting light toward a subject, a light receiving means for receiving reflected light from the subject, a light projecting element included in the light projecting means, and a light receiving included in the light receiving means. Scanning means for connecting the elements to each other to reciprocate within the photographing screen, a peak detection circuit for detecting a peak value of reflected light intensity received while the light receiving means is moving in the forward direction, and a position for detecting the peak value. And a control circuit for stopping the movement of the light receiving means in the backward direction at the peak value detection position, and when the light receiving means stops at the peak value detection position A distance measuring device having a distance calculating circuit for measuring a distance. 2. A camera comprising: the distance measuring device according to claim 1; a focusing device that extends a lens according to a distance signal from the distance measuring device; and an exposure device that photographs a subject.