JPH052129A - Range-finding device for electronic still camera - Google Patents

Abstract

PURPOSE:To obtain range-finding data by TTL without receiving the effect of photographing magnification. CONSTITUTION:When a zoom ring 3 is turned, a tooth array part 30 formed on a zoom lens barrel 26 is turned. The tooth array part 30 moves a cam plate 36 through a rack 35. By moving the cam plate 36, lenses 5a and 5b comply with the focusing movement of a zoom lens 4, so that the focusing of a light projecting lens 5 is performed. When a light emitting diode 40 is turned on in such a state, range-finding light is formed in a spot state by an aperture 39 and projected from the lenses 5a and 5b. The spot light reflected on an object is formed as a spot image on a CCD 31 through the zoom lens 4. Thus, even though the photographing magnification of the zoom lens is changed, the image height of the spot light made incident on the CCD is always kept constant.

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 a floodlight type electronic still camera.

[0002]

2. Description of the Related Art An electronic still camera having a built-in light-projection type distance measuring device and capable of focusing on an object at a short distance is described in Japanese Patent Application No. 2-238001. Have been described. In this electronic still camera, the distance measuring light projected from the light projecting unit and reflected by the subject is made incident on the distance measuring light receiving element by TTL, and the distance measuring corresponding to the subject distance is made based on the incident position and the size of the incident pattern. Data is being calculated. Furthermore, a solid-state image pickup device, such as a CCD, which converts an object image into an electric signal is used as the distance measuring light receiving element to achieve miniaturization.

[0003]

By the way, when a zoom lens is used as an image pickup lens in the above-mentioned conventional electronic still camera so as to take a close-up image of a subject, the subject distance is constant. However, since the incident position and the size of the incident pattern vary depending on the imaging magnification of the zoom lens, there is a problem that the distance measuring device cannot measure the distance. It is an object of the present invention to provide a distance measuring device for an electronic still camera, in which distance measuring data can be obtained without being affected by the photographing magnification of a zoom lens.

[0004]

In order to achieve the above object, a distance measuring device of the present invention comprises a light projecting lens composed of a plurality of lenses for projecting distance measuring light, and a distance measuring light reflected by an object. Is read by the solid-state image sensor, and a zoom lens that makes a subject image incident on a solid-state image sensor that converts the object image into an electric signal A detection circuit for detecting the size of the incident pattern of the distance measuring light from the electric signal and a calculation unit for calculating the distance measurement data corresponding to the object distance from the size of the incident pattern are provided.

[0005]

FIG. 5 shows an electronic still camera having a built-in distance measuring device according to the present invention. On the front surface of the electronic still camera 2, a zoom lens 4, whose zoom magnification is variable by a zoom ring 4, A light projecting lens 5 for projecting distance light and a strobe light emitting section 6 are provided. A release button 7 is provided on the upper surface, and a loading port 9 for loading a memory cartridge 8 for recording a video signal is provided on the side surface. The reference numerals 10 and 11 indicate the optical axes of the zoom lens 4 and the light projecting lens 5.

FIG. 2 shows a lens configuration of a zoom lens and a light projecting lens. The zoom lens 4 is composed of four lenses 4a to 4d. Also, the projection lens 5 is 2
It is a lens that can be adjusted in focus and is composed of a plurality of lenses 5a and 5b. When the zoom ring 3 described above is rotated,
The lenses 4b and 4c and the lenses 5a and 5b move on the optical axes 10 and 11 as shown by arrows in the figure. The focal lengths of the zoom lens 4 and the projection lens 5 are f ₁ and f ₂ (variables).

FIG. 1 shows an interlocking mechanism of a zoom lens and a light projecting lens. The lens 4a is held by a focus ring 25, and the focus ring 25 is rotatably attached to a zoom lens barrel 26. When the focus ring 25 is rotated by the motor 27, the lens 4a is moved in the optical axis direction to focus the zoom lens 4. The zoom lens barrel 26 includes lenses 4a ...
It is rotatably attached to a lens barrel (not shown) holding 4d, and cam grooves 28 and 29 for moving the lenses 4b and 4c in the optical axis direction on the peripheral surface thereof, the zoom ring 3 and the tooth row described above. The part 30 is formed. Behind the zoom lens barrel 26, a solid-state image pickup device such as a CCD 31 is arranged. Further, since the code 32 monitored by the reflection type photo sensor 33 is recorded on the zoom lens barrel 26,
The rotation amount of the zoom ring 3 is grasped by a microcomputer described later.

A rack 35 is meshed with the tooth row portion 30, and for example, f ₁ / f ₂ is kept constant corresponding to the focus movement of the zoom lens 4 on the rack 35, and the projection lens 5 is provided. A cam plate 36 for moving the focal point is integrally formed. The cam plate 36 is formed with a pair of cam grooves 36a and 36b. The cam grooves 36a and 36b are engaged with the lenses 5a and 5b guided by a straight guide 37, respectively, and these are moved in the optical axis direction. Moving. A regulating plate 39 having an opening 38 with a diameter L ₂ is arranged behind the lens 5b, and a light emitting diode 40 for emitting distance measuring light is arranged behind the regulating plate 39.

When the light emitting diode 40 is turned on, the distance measuring light is shaped into a spot shape by the opening 38 and then projected from the light projecting lens 5 toward the subject 45 as shown in FIG. The spot light reflected by the subject 45 is a CCD as a spot image with a diameter L _{X that} is blurred by the zoom lens 4.
The image is formed at 31. When projecting the spot light, the lens 4a is moved to the position closest to the lens 4b (hereinafter referred to as the infinity side). This diameter L _X is converged to the diameter L _{1 as} shown in FIG. 1 when the lens 4a is moved to the in-focus position. Therefore, the blur amount at this time is (L _X −L ₁ ). The diameter L ₁ is L ₁ = L ₂ · f
_{It is} derived from the formula ₁ / f _{2 and} is constant regardless of the subject distance.

FIG. 4 showing the electrical construction of the electronic still camera.
At, the spot light reflected by the subject 45 and the light from the subject 45 enter the half mirror 50 fixed at an inclination of 45 degrees via the zoom lens 4. Half of the light that has entered the half mirror 50 is reflected and focused on the focus glass 52 provided on the lower surface of the pentaprism 51. The subject image formed on the focus glass 52 is observed through the viewfinder eyepiece lens 53. The remaining light is transmitted and imaged on the CCD 31.

The CCD 31 is provided with an amplifier 54,
A video signal processing circuit 55 for converting an electric signal into a video signal is connected. The video signal processing circuit 55 has a recording section 56 for writing a video signal in the memory cartridge 8.
A detection circuit 57 is connected which detects the electric charge of the spot light component from the video signal, obtains the diameter L _{X of the} spot image from the electric charge distribution, and outputs it as diameter data. The detection circuit 57 includes a motor 2 for moving the lens 4a to a focus position.
A calculation unit 58 for calculating the rotation amount of 7 is connected. The calculation unit 58 obtains the blur amount from the diameter data and calculates the rotation amount from the blur amount. The microcomputer 59 for controlling the electronic still camera 2 is connected to the calculator 58, and the calculated rotation amount data is sent to the microcomputer 59.

A signal generator 7a for outputting a distance measurement start signal and a release signal to the microcomputer 59 by pressing the release button 7, a lens drive controller 60 for driving the motor 27, and a drive controller for driving the CCD 31. 61
And a light projection control unit 62 for lighting the light emitting diode 40, respectively.

Here, the control performed by the microcomputer 59 will be briefly described. When the distance measurement start signal is output from the signal generator 7a, the microcomputer 59 causes the lens drive controller 6 to operate.
The motor 27 is rotated via 0 to move the lens 4a to the infinity side. After this, the microcomputer 59 further drives the drive control unit 61.
The CCD 31 is driven to accumulate electric charge via the light emitting control unit 62, and the light emitting diode 40 is turned on via the light projecting controller 62 in response to the electric charge accumulation drive. Further, when data is sent from the calculation unit 58, the microcomputer 59 sends the rotation amount data to the lens drive control unit 60, drives the motor 27, and moves the lens 4a to the in-focus position. When the release signal is sent in this state, the microcomputer 59 drives only the drive control section 61 to cause the CCD 31 to accumulate the recording charge.

The operation of the above-described embodiment will be described below. When the distance measurement start signal is output from the signal generator 7a, the microcomputer 59 causes the drive control unit 61 and the light projection control unit 6 to operate.
Drive 2 The drive control unit 61 drives the CCD 31 for charge storage, and the light projection control unit 62 turns on the light emitting diode 40 in accordance with the charge storage time of the CCD 31.

The distance measuring light emitted by turning on the light emitting diode 40 is shaped into a spot shape by the regulation plate 39, and then projected toward the subject 45 by the light projecting lens 5. This spot light is reflected by the subject 45, enters the CCD 31 via the zoom lens 4, and accumulates the electric charge of the spot light component.

The electric signal containing the electric charge of the spot light component is amplified by the amplifier 54, converted into a video signal by the video signal processing circuit 55, and sent to the detection circuit 57. The detection circuit 57 obtains the diameter L _X from the video signal and sends the diameter data to the arithmetic unit 58. The calculation unit 58 calculates the rotation amount of the motor 27 from the diameter data and sends it to the microcomputer 59. The microcomputer 59 outputs the rotation amount data to the lens drive controller 60 and moves the lens 4a to the in-focus position via the motor 27.

In this state, the release button 7 is pressed,
When the release signal is output from the signal generator 14a, the microcomputer 59 drives the drive control unit 61 to cause the CCD 31 to take an image for recording. The electric signal for recording is sent to the video signal processing circuit 55 via the amplifier 54 and converted into a video signal. This video signal is written in the memory cartridge 8 by the recording unit 56. In this embodiment, spot light is projected from the light projecting lens 5 and the focus position is detected from the diameter of the spot image, but the focus position can be detected from the area of the spot image. In this case, the shape of the distance measuring light may be a slit shape. Further, in the above embodiment, the lens 4a was moved to the infinity side when the spot light was projected, but this position may be the farthest position from the lens 4b.

[0018]

As described above in detail, in the range finder for an electronic still camera according to the present invention, the solid-state image pickup device for picking up an image of a subject by adjusting the focus of the projection lens in response to the movement of the focus of the zoom lens. Since the distance-measuring light is projected so that the size of the incident pattern incident on is constant, it is possible to easily obtain the distance-measuring data from the blur amount of the incident pattern.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of a distance measuring device according to the present invention.

FIG. 2 is an explanatory diagram showing a lens configuration of a zoom lens and a light projecting lens.

FIG. 3 is a diagram showing a projection path of spot light.

FIG. 4 is a diagram showing an electrical configuration of an electronic still camera incorporating the distance measuring device of the present invention.

FIG. 5 is a perspective view of an electronic still camera incorporating the distance measuring device of the present invention.

[Explanation of symbols]

 2 electronic still camera 4 zoom lens 5 light projecting lens 30 tooth row 31 CCD 35 rack 36 cam plate 39 regulation plate 45 subject 57 detection circuit 58 arithmetic unit

Claims (1)

Claim: What is claimed is: 1. A projection lens comprising a plurality of lenses for projecting distance measuring light, and a solid-state imaging device for converting the distance measuring light reflected by a subject into an electric signal of the subject. The zoom lens to be incident on, the adjusting means for adjusting the focus of the light projecting lens according to the focus movement of the zoom lens, and the size of the incident pattern of the distance measuring light from the electric signal read by the solid-state image sensor. A distance measuring apparatus for an electronic still camera, comprising a detection circuit for detecting and a calculation unit for calculating distance measuring data corresponding to a subject distance from the size of an incident pattern.