JPS61116313A - Automatic focus detector - Google Patents

Abstract

PURPOSE:To simplify the titled device by fixing a solid-state image pickup element on a fine vibration device, vibrating the fine vibrating device in the optical axis direction and detecting a high frequency component from a video signal to detect focusing state. CONSTITUTION:In the automatic focus detector for extracting a high frequency component from a video signal obtained by photoelectrically converting an optical image made incident on a lens and detecting a focusing signal, the solid-state image pickup element 4 is used as a photoelectric conversion means and the element 4 is supported on the fine vibration device obtained by adhering piezoelectric elements 1, 2 e.g. and supporting and fixing both the ends of the adhered vibrator by outer frames 3 and vibrated in the optical axis direction of the lens to detect the focusing signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic focus detection device for an apparatus using nine solid-state sensors, such as a video camera.

BACKGROUND OF THE INVENTION There are various methods for detecting the focal position of a video camera or the like. Compared to other methods, this method provides images with better focus, does not depend on the distance of the subject image, allows the use of high-magnification lenses, and is cost-effective. This is a so-called blur detection method that measures the amount of high frequency components.

(NHK Technical Research Report, Volume 17, No.-8, Volume 8)
See No. 6, page 21. ) The blur detection method that detects the focal position signal from the video signal involves the so-called hill-climbing method, in which the focal position is found by moving lens groups and comparing the amount of high-frequency components, but it takes time to detect the focal position. Therefore, it has the disadvantage of not being able to follow sudden changes. As a method with improved ability to follow sudden changes, there is a method of changing the optical path length of light entering an image sensor and measuring the amount of high frequency components of a video signal. For example, there are methods in which a prism is placed in front of the image sensor and vibrated to change the optical path length, and a method in which a lens immediately in front of the image sensor is vibrated.

Problems to be Solved by the Invention When vibrating a prism, large vibrations are required, which is impractical; when vibrating a lens, a special structure is required, making it impossible to replace the lens.

An object of the present invention is to provide a focus position detection device that can be easily driven without increasing the size of the device in an autofocus camera using a solid-state image sensor.

Means for Solving the Problems A solid-state image pickup device is fixed to a microvibration device, vibrated in the optical axis direction, and the amount of high frequency components is detected from the video signal to detect the in-focus state.

The working image sensor is small and lightweight and can be easily driven, which simplifies the device. Furthermore, there is no need for a structure that would impede lens exchange.

Embodiment 1.2 in FIG. 1 is a rectangular plate-shaped piezoelectric element having a polarization axis in the thickness direction, and the piezoelectric element is used as a bonded vibrator.

Both ends of this bonded vibrator are supported and fixed to the outer frame 3 to constitute a micro-vibration device. A solid-state image sensor 4 is fixed to the center of the laminated vibrator and arranged perpendicularly to the optical axis A. When a voltage is applied to the bonded vibrator, one piezoelectric element expands, the other piezoelectric element contracts, the bonded vibrator bends perpendicularly to the optical axis A, and the solid-state image sensor 4 changes. Furthermore, when an alternating current voltage is applied, the micro-vibration device vibrates in a direction perpendicular to the optical axis as shown by arrow B, and the solid-state image sensor fixed to the micro-vibration device similarly vibrates on the optical axis.

At this time, the in-focus state can be detected by checking the amount of high frequency components of the video signal from the solid-state image sensor 4.

If a disc-shaped piezoelectric element is used instead of the plate-shaped piezoelectric elements 1 and 2 and its periphery is supported and fixed, a similar effect can be obtained with strong resistance to impact.

FIG. 2 shows another embodiment, in which a metal plate 5, which is sufficiently thinner than the piezoelectric element, is sandwiched and bonded between two piezoelectric elements 1 and 2 to form a bonded vibrator.

By supporting and fixing the peripheral metal plate 6 to the outer frame 3 as shown in Fig. 2, it is possible to obtain excellent shock resistance, operability, mass production, and vibration characteristics similar to the above-mentioned micro-vibration device. .

FIG. 3 shows a case where a voice coil type microvibration device is used. When the solid-state image sensor 4 is attached to the coil 6, the magnet 7 is placed in the center of the coil 6, and an alternating current is passed through the coil 6, the coil 6 vibrates in the direction of the optical axis A, creating a micro-oscillator using a piezoelectric element. A similar result is obtained.

Effects of the Invention As described above, according to the present invention, since a focus signal is detected by vibrating the solid-state image sensor, it is possible to realize an apparatus with a simple structure, low cost, and high productivity.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of an automatic focus detection device using a piezoelectric element according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view of a device using the same voice coil. 1.2...piezoelectric element, 3-...outer frame, 4...
...Solid-state image sensor, 6...Metal plate.

Claims (6)

[Claims] (1) In an automatic focus detection device that extracts high frequency components from a video signal obtained by photoelectrically converting a light image incident through a lens and detects a focus signal, a solid-state image sensor is used as a photoelectric conversion means, An automatic focus detection device characterized in that the solid-state image sensor is supported on a vibrating device, and a focus signal is detected by vibrating the solid-state image sensor in the optical axis direction of the lens. (2) Automatic focus detection according to claim 1, characterized in that two piezoelectric elements are bonded together to form a bimol type vibrator, a solid-state image sensor is fixed thereon, and the vibrator is vibrated. Device. (3) The automatic focus detection device according to claim 1, characterized in that a solid-state image sensor is fixed to a voice-type coil vibrator, and the vibrator is vibrated. (4) A claim characterized in that two rectangular plate-shaped piezoelectric elements having polarization axes in the thickness direction are bonded together, a solid-state image sensor is fixed in the center, and both ends of the piezoelectric element are supported. Second
The automatic focus detection device described in Section 1. (5) Claim 2, characterized in that two disc-shaped piezoelectric elements having polarization axes in the thickness direction are bonded together, a solid-state image sensor is fixed in the center, and the peripheral part is supported and fixed. The automatic focus detection device described in Section 1. (6) A piezoelectric vibrator is formed by laminating a metal plate sufficiently thinner than the thickness of the piezoelectric element between two piezoelectric elements, and the ends of the metal plate are supported and fixed. The automatic focus detection device according to item 2.