JPH0527160A - Range-finder device for electronic still camera - Google Patents

Abstract

PURPOSE:To simplify the constitution of a circuit and to reduce the cost of a range-finder device. CONSTITUTION:Spot light projected from a light projecting part and reflected on an object is made incident on the incident area 22 of a CCD 20 through a lens and a color filter. Since the light projecting part is provided in a direction orthogonally crossed with the horizontal scanning direction of the CCD 20, the area 22 is set to be narrow in the horizontal scanning direction. An electrical signal read out by the CCD 20 is transmitted through an amplifier to a gate circuit, where it is converted to a signal for range-finding where charge other than in the area 22 is removed. The signal for range-finding is corrected in terms of brightness by a brightness correction circuit, and transmitted to a detection circuit. The component charge of the spot light is detected from the signal for range-finding after correction in the detection circuit, and a position signal corresponding to an incident position is transmitted to an arithmetic part. Based on the position signal, range-finding data corresponding to an object distance is calculated in the arithmetic part. Therefore, the brightness correction circuit only corrects the component of remaining charge in terms of brightness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device for an electronic still camera of an active type triangulation type.

[0002]

2. Description of the Related Art Japanese Patent Application No. 2-238001 proposes an electronic still camera which uses an active-type triangulation type distance-measuring device and receives distance-measuring light through an imaging lens. When this method is adopted, the image pickup lens is often located out of the in-focus position at the time of performing distance measurement, so that the image of the subject is captured even if a spot-shaped distance measuring light is projected onto the subject. Distance-measuring light having a skirt-spreading pattern is generally incident on a two-dimensional solid-state image sensor. When distance-measuring light is incident on the solid-state image sensor in such a wide pattern, it is possible to perform almost accurate distance measurement by obtaining the barycentric position of the pattern in the direction of the base line length of the triangulation distance measurement. You can

Further, in order to enable color image pickup by an electronic still camera, a color filter is incorporated in the front surface of the solid-state image pickup device. In this color filter, filters having characteristics of blue transmission, green transmission, and red transmission are generally arranged in a mosaic pattern corresponding to each pixel, and the transmittance for distance measuring light differs depending on the type of filter. Therefore, even if the brightness distribution pattern of the distance measuring light itself reflected from the subject is as shown in FIG. 7, the charge level of the photoelectric signal directly obtained from each pixel of the solid-state image sensor is not necessarily shown in FIG. Not exactly. Therefore, before obtaining the center of gravity of the distance measuring light pattern, it is necessary to perform level correction on the photoelectric signal from each pixel in accordance with the transmittance of the filter located in front of it.

[0004]

However, since the solid-state image pickup device outputs a photoelectric signal for each pixel by horizontal and vertical scanning, if the direction of the baseline length is made to coincide with the direction of horizontal scanning, it is output from each pixel. It is necessary to correct the level of the incoming photoelectric signal and process the calculation for obtaining the center of gravity within one horizontal scanning period. In general, one horizontal scanning period is about 66 μsec, and considering that the range used for distance measurement is about half that per horizontal scanning range, the photoelectric signals output for each pixel during 33 μsec are individually leveled. While performing the correction, the process of obtaining the barycentric position must be performed before the next horizontal scanning is started. Therefore, the signal processing circuit used for this purpose is required to have a high-speed processing function, and it is inevitable that the circuit scale and the processing routine become large and the cost increases.

The present invention has been made in consideration of such circumstances, and it is not necessary to perform high-speed signal processing on the photoelectric signal output for each pixel at the time of distance measurement, and the scale of the signal processing circuit for that purpose is large. An object of the present invention is to provide a distance measuring device for an electronic still camera that does not need to be converted.

[0006]

To achieve the above object, the present invention provides a solid-state image pickup device in which one vertical scanning period is 16.
Focusing on 6 msec, which is longer than one horizontal scanning period,
The photoelectric signal output from the solid-state image sensor for each pixel can be processed based on the vertical scanning period. For this reason, in the present invention, the distance measuring light projecting units are arranged in the vertical direction of the solid-state image sensor so that the direction of the base line length of the triangulation is intersected with the horizontal scanning direction of the solid-state image sensor. is there.

[0007]

FIG. 6 shows an electronic still camera incorporating the distance measuring device of the present invention. On the front surface of the electronic still camera 2, an image pickup lens 3, a stroboscopic light emitting portion 4 and a light projecting optical axis are provided. A light projecting unit 5 for projecting distance measuring light is provided along 5a. A release button 6 is provided on the upper surface, and a loading port 8 for loading a memory cartridge 7 for recording a video signal is provided on the side surface. The light projecting unit 5 is arranged in the electronic still camera 2 above the lens 3 and on a vertical line passing through the center of the lens 3. The projection optical axis 5
The distance between a and the optical axis 3a is the baseline length H of the electronic still camera 2.

FIG. 1 showing the electrical configuration of the electronic still camera.
In the light projecting section 5, the projecting lens 5 and the regulating plate 12
And a light emitting diode 13 that emits distance measuring light. The distance-measuring light is shaped into a spot by the regulation plate 12 and then projected by the light projecting lens 10 toward the subject 14. Spot light reflected by the subject 14 and the subject 14
Light from the lens enters the half mirror 15 fixed at an inclination of 45 degrees via the lens 3. This half mirror 15
Half of the light incident on is reflected and focused on the focus glass 17 provided on the lower surface of the pentaprism 16. The subject image formed on the focus glass 17 is observed through the viewfinder eyepiece lens 18. Further, half of the light is transmitted and is incident on a solid-state image sensor, such as a CCD 20, provided behind the half mirror 15, and an image is formed on an incident area 22 shown by a chain double-dashed line in FIG.

In FIG. 2 showing the CCD, an image pickup surface 2
0a is a charge storage element 21 that constitutes the 400,000 pixels.
The effective pixels (see FIG. 3) are arranged in, for example, 488 rows × 768 columns. The charge storage element 21 stores charges according to the illuminance of incident light. The charges stored in the charge storage element 21 are horizontally scanned from the bottom to the top of the CCD 20 every other row and read out by 488 horizontal scanning signals. Each horizontal scanning signal includes 768 pixel data, which corresponds to the horizontal scanning line of the television.

Since the light projecting portion 5 is provided on the vertical line passing through the center of the lens 3, the above-mentioned incident area 22 has its shape,
It can be set to an elongated rectangle along the base length direction.
The incident area 22 is composed of 244 rows × 7 columns of charge storage elements 21, as shown in FIG. In addition, in order to extract color information on the front surface of the imaging surface 20a, R,
A color filter 25 composed of three colors G and B, for example, a vertical stripe filter shown in FIG. 5 is attached.

The CCD 20 is connected to the CCD 20 via an amplifier 26.
A video signal processing circuit 27 for converting 488 horizontal scanning signals (hereinafter referred to as electric signals) into video signals is connected. A recording unit 28 is connected to the video signal processing circuit 27, and the video signal is A / D converted here,
It is written in the memory cartridge 7. Further, a gate circuit 29 for extracting a distance measurement signal corresponding to the incident area 22 from the electric signal is connected to the amplifier 26. This distance measuring signal is obtained by deleting the pixel data in the shaded area shown in FIG. 4 from the electrical signal, and is composed of 244 horizontal scanning signals having 7 pixel data corresponding to the incident area 22.

By the way, since the brightness information of the distance measuring signal is affected by the color filter 25 and does not correspond to the brightness of the subject, a brightness correction circuit 30 for removing the effect of the color filter 25 is connected to the gate circuit 29. Has been done. The brightness correction circuit 30 corrects the brightness of seven pixel data for each horizontal synchronization period of 244 horizontal scanning signals. Further, the brightness correction circuit 30 is connected to a detection circuit 34 that detects a high charge area protruding from the surroundings from the corrected distance measurement signal and specifies the spot light incident position. The detection circuit 34 sends a position signal to the calculation unit 35 corresponding to the incident position of the spot light. The calculation unit 35 calculates distance measurement data corresponding to the subject distance based on the position signal, and sends the distance measurement data to the microcomputer 36 that controls the electronic still camera 2.

The microcomputer 36 includes a signal generator 6a which outputs a distance measurement start signal and a release signal when the release button 6 is pressed, a lens drive controller 43 which drives a motor 41 which moves the lens 3, and the CCD 20. A drive control unit 45 for driving and a light projecting control unit 47 for lighting the light emitting diode 13 are respectively connected.

Here, the control performed by the microcomputer 36 will be briefly described. When the power of the microcomputer 36 is turned on, the microcomputer 36 drives the lens drive controller 43 to move the lens 3 to the initial position of infinity. Then, when the distance measurement start signal is output from the signal generator 6 a, the microcomputer 36 charges the CCD 20 via the drive control unit 45 for charge accumulation, and turns on the light emitting diode 13 via the light emission control unit 47. Further, when the distance measurement data is input, the microcomputer 36 sends it to the lens drive controller 43 to move the lens 3 to the in-focus position. In this state, when the release signal is input, the microcomputer 36 drives only the drive controller 45,
The CCD 20 is made to capture an image for recording.

The operation of the electronic still camera of the present invention will be described below. When the distance measurement start signal is output from the signal generator 6a, the microcomputer 36 drives the drive control unit 45 and the light projection control unit 47, respectively. This drive control unit 45
Drives the CCD 20 to accumulate charges. Further, the light emission control unit 4
7 turns on the light emitting diode 13 in accordance with the charge storage time of the CCD 20.

The distance measuring light emitted from the light emitting diode 13 is projected toward the subject 14 by the light projecting lens 10. This spot light is reflected by the subject 14 as shown in FIG. The spot light reflected by the subject 14 enters the incident area 22 via the lens 3. The electric signal at the time of distance measurement is amplified by the amplifier 26 and then sent to the gate circuit 29. The gate circuit 29 extracts a signal for distance measurement from the electric signal and sends it to the brightness correction circuit 30. The brightness correction circuit 30 removes the influence of the color filter 25 from the distance measurement signal and sends it to the detection circuit 34. The brightness correction circuit 30
Since it is sufficient to correct the brightness of seven pixel data in one horizontal synchronization period, it is not necessary to increase the processing speed. Therefore, the distance measuring device of the present invention can have a simple circuit configuration.

The detection circuit 34 detects the incident position of the spot light from the corrected distance measurement signal and sends a position signal corresponding to this to the arithmetic unit 35. The calculation unit 35 calculates distance measurement data corresponding to the subject distance from the position signal and sends it to the microcomputer 36. When this distance measurement data is sent from the microcomputer 36 to the lens drive control unit 43, the lens drive control unit 43
Drives the motor 41 to move the lens 3 to the in-focus position. In this way, the preparation for distance measurement is completed.

In this state, the release button 6 is pressed,
When the release signal is output from the signal generator 6a, the microcomputer 36 drives only the drive control unit 45, and the CCD 20
Let the camera take an image for recording. Then, the electric signal for recording is sent to the video signal processing circuit 27 via the amplifier 26 and converted into a video signal. This video signal is recorded in the recording unit 28.
Is digitized by and written in the memory cartridge 7. After that, when the lens 3 is moved to the initial position by the lens drive control unit 43, preparation for the next distance measurement is completed.

[0019]

As described above in detail, in the range finder for an electronic still camera according to the present invention, since the light projecting portion is provided in the direction orthogonal to the horizontal scanning direction of the solid-state image sensor,
Since the incident area on which the distance measuring light is incident can be set narrow in the horizontal scanning direction, it is possible to reduce the number of luminance data processed in one horizontal synchronization period. Therefore,
This distance measuring device does not need to have a high processing speed as compared with the conventional one, so that the circuit configuration can be simplified.

[Brief description of drawings]

FIG. 1 is a diagram showing an electrical configuration of an electronic still camera.

FIG. 2 is a diagram showing an incident area of a CCD.

FIG. 3 is an enlarged view of the incident area of FIG.

FIG. 4 is a diagram showing an image pickup area of a CCD for reading out a distance measurement signal.

FIG. 5 is a diagram showing a vertical stripe filter.

FIG. 6 is a perspective view of an electronic still camera.

FIG. 7 is a diagram showing a distribution of electric charges accumulated at spots on which spot light is incident.

[Explanation of symbols]

 2 electronic still camera 3 lens 5 light emitting unit 13 light emitting diode 14 subject 20 CCD 29 gate circuit 30 brightness correction circuit 34 detection circuit 35 arithmetic unit 36 microcomputer

Claims (1)

Claims: 1. Distance-measuring light emitted from a light projecting unit and reflected by a subject is passed through an imaging lens together with a subject image.
In a range finder for an electronic still camera, which is adapted to be incident on a three-dimensional solid-state image sensor, the light-projecting section is arranged in the vertical direction of the solid-state image sensor,
A distance measuring device for an electronic still camera, wherein a direction of a base line length of triangulation is intersected with a horizontal scanning direction of a solid-state image pickup device.