JPS6321616A - Automatic focus adjusting device - Google Patents

Abstract

PURPOSE:To improve defocusing detection accuracy and reliability by using a disk whose outer periphery is held as a vibrating means and also using a flexible printed board for leading a signal out of a solid-state image pickup element. CONSTITUTION:A bimorph material 19 to which ring-shaped piezo-electric elements 18a and 18b are adhered on both surfaces of a ring-shaped metallic thin plate 17 is provided at the back of a photographic lens 11, and the outer peripheral part of the thin plate 17 is fixed by a ring-shaped external frame 20 fixed to the lens 11 and an external frame pressure screw 21. Further, an internal frame 22 is fixed to the inner peripheral part of the thin plate 17 by an internal frame pressure screw 23 and the solid-state image pickup element 16 is adhered to the internal frame 22. One terminal of the flexible printed board 25 is connected to the signal terminal 24 of the element 11 and the other terminal is connected to a focusing control circuit 26. The circuit 26 with a BPF compares the vibration phase of the element 16 with a phase wherein a high frequency component varies to detect a front or rear focus state, thereby determining the rotational direction of a focus motor 15. The motor 15 is stopped where the high frequency component becomes maximum and the focusing operation is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic focus adjustment device that can be used in a video camera or the like using an image sensor.

2. Description of the Related Art In recent years, as video cameras have become popular, automatic focusing devices that enable easy focusing have been put into practical use. Hereinafter, the above-mentioned conventional automatic focusing device will be explained with reference to the drawings.

FIG. 3 is a diagram showing the main parts of a conventional automatic focus adjustment device.
FIG. 4 is a rear view of FIG. 3.

In FIG. 3, a focus lens 1 is configured to be driven by a focus motor 2, and a solid-state image sensor 4 is attached to the center of a bimorph 3. The bimorph 3 has a rectangular outer shape as shown in FIG. 4, and both ends of the bimorph 3 are sandwiched between a frame 6 and a bimorph retainer 6, and are attached by bimorph retainer screws 7. Further, the bimorph 3 is driven by an AC voltage from a bimorph drive circuit 8, and the solid-state image sensor 4
is vibrated in the direction of the optical axis 9. The output signal of the solid-state image sensor 4 is connected to a blur detection circuit 1o, and the blur detection circuit 1o changes between a front focus state (the front is in focus) or a back focus state (the back is in focus) depending on the vibration. The focus motor 2 is rotated in a direction that reduces blurring, and the focus lens 1 is driven.

Problems to be Solved by the Invention However, with the above configuration, both ends of the rectangular bimorph are sandwiched between the frame and the bimorph holder and tightened with screws, making it difficult to press the ends of the bimorph with uniform force. At the same time, since only both ends are held, the bimorph tends to warp, and the solid-state image sensor attached to the center of the bimorph is not perpendicular to the optical axis of the lens, resulting in unilateral blur. Ta.

Furthermore, when an alternating current voltage is applied to the bimorph to make it vibrate,
Since the vibration components are distributed in directions other than the optical axis direction of the lens, the solid-state image sensor vibrates not only in the front and back directions (in the optical axis direction), but also in the vertical and horizontal directions, resulting in a decrease in blur detection accuracy. Furthermore, since the end faces other than both ends of the bimorph are exposed, they are vulnerable to impact, and there is also a concern that the end faces may crack or get scratched.

In view of the above-mentioned problems, the present invention has been developed to provide an automatic focusing device with high performance and reliability, which holds a solid-state image sensor vertically to prevent unilateral blur, and increases blur detection accuracy by vibrating only in the optical axis direction. It provides:

Means for Solving the Problems In order to solve the above-mentioned problems, the automatic focus adjustment device of the present invention fixes the imaging means substantially at the center, fixes the outer periphery, and vibrates the imaging means slightly in the optical axis direction. and a control means for controlling the focusing of the photographic lens so that the high frequency component of the output signal from the imaging means is maximized.

There is no effect, and vibration can be reliably made only in the optical axis direction.

Embodiments Hereinafter, automatic focusing devices according to embodiments of the present invention will be described with reference to the drawings.

Figure 1 is a configuration diagram of the main parts of an embodiment of the present invention, and Figure 2 is a diagram of the main part of an embodiment of the present invention.
FIG. 3 is a rear view seen from the direction of the arrow in the figure.

In FIG. 1, a focus ring 12 is provided at the front of a photographing lens 11 for photographing a subject, and a gear 1
3.14 to the focus motor 15. A solid-state imaging device 16 such as a charge transfer device (GCD) for converting an optical image into an electrical signal is disposed on the imaging surface of the photographic lens 11. At the rear of the photographing lens 11, a bimorph 19 is provided, in which ring-shaped piezoelectric elements 18 & 18b are bonded to both sides of a ring-shaped thin metal plate 17. It is firmly held by a ring-shaped outer frame 20 fixed to 11 and an outer frame holding screw 21. The inner frame 22 is still fixed to the inner periphery of the thin metal plate 17 by inner frame holding screws 23, and the solid-state image sensor 16 is adhered to the inner frame 22.

A flexible printed board 25 made of a thin plate such as polyimide and has flexibility is soldered to the signal terminal 24 of the solid-state image sensor 16.
The other end of 5 is connected to a focus control circuit 26.

The bimorph drive circuit 27 generates an alternating current voltage of 1 sHz, and causes the bimorph 19 to vibrate slightly, thereby slightly driving the solid-state image sensor 16 in the direction of the optical axis 28 of the photographing lens 11. The focus control circuit 26 includes a bandpass filter (for example, a center frequency of 1M) for detecting only high frequency components from the video signal obtained by the solid-state image sensor 16.
It compares the vibration phase of the solid-state image sensor 16 with the phase in which the high frequency component changes to detect whether the focus is on the front or rear focus and determine the rotation direction of the focus motor 1ε. The rotation of the focus motor 16 drives the focus ring 12, and when the high frequency component reaches the maximum, the focus motor 15 is stopped and focusing is completed.

The bimorph drive circuit 27 controls the vibration amplitude of the bimorph 19 according to the aperture value of the photographic lens 11, and reduces the amplitude when the aperture is open and increases the amplitude when the aperture is closed. In the upper part, the blur due to vibration is not noticeable, and changes in high frequency components can be detected.

As described above, according to this embodiment, since the outer periphery of the disk is held all around, when an AC voltage is applied, the center of the disk vibrates in the optical axis direction, and therefore the disk is fixed approximately at the center. It is possible to reliably vibrate the solid-state image sensor only in the optical axis direction, eliminate one-sided blurring, and make it resistant to external shocks. By using a flexible printed board that still has flexibility for extracting signals from the solid-state image sensor, the vibration load on the vibration means is reduced, and the bimorph board can be made smaller.

Although a ring-shaped piezoelectric element was used in this example,
A configuration may also be used in which a complete disk-shaped piezoelectric element is used and a solid-state image sensor is attached on the center of the lens side.

Effects of the Invention As described above, the present invention provides a disc-shaped vibration means that fixes the imaging means substantially at the center and fixes the outer circumference, and slightly vibrates the imaging means in the optical axis direction, and an output from the imaging means. Since the camera is equipped with a control means for controlling the focusing of the photographing lens so that the high frequency component of the signal is maximized, the imaging means can be reliably held in the direction of the optical axis and vibrated, preventing unilateral blurring and It also becomes possible to improve impact resistance.

As a result, blur detection accuracy is increased, and an automatic focus adjustment device with high performance and reliability can be provided.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of the main parts of an automatic focus adjustment device according to an embodiment of the present invention, FIG. 2 is a rear view of FIG. 1, FIG. 3 is a configuration diagram of a conventional automatic focus adjustment device, and FIG. 4 is a rear view of FIG. 3. 11... Photographing lens, 16... Solid-state image sensor, 19... Bimorph, 25...
-Flexible printed board, 26... Focusing control circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure 4

Claims (1)

[Claims] a photographing lens for photographing a subject; an imaging means for converting an optical image formed by the photographing lens into an electrical signal; the imaging means is fixed substantially at the center and the outer circumference is fixed, and the imaging means is slightly vibrated in the optical axis direction. a disc-shaped vibrating means for controlling the image pickup means; a control means for controlling the focusing of the photographic lens so that the high frequency component of the output signal from the image pickup means is maximized; and an electrical connection between the image pickup means and the control means. 1. An automatic focusing device comprising: a flexible connecting member for connecting to the automatic focusing device.