JPH0627892B2 - Automatic focus adjustment device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. 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, with the widespread use of video cameras, automatic focusing devices that enable easy focusing have been put into practical use. Hereinafter, the above-described conventional automatic focus adjusting device will be described with reference to the drawings.

FIG. 3 is a block diagram of a main part of a conventional automatic focus adjusting device, and FIG. 4 is a rear view of FIG.

In FIG. 3, the 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 the 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 the frame 5 and the bimorph retainer 6 and attached by the bimorph retainer screw 7. The bimorph 3 is driven by the AC voltage from the bimorph drive circuit 8 and the solid-state image sensor 4
Is oscillated in the direction of the optical axis 9. The output signal of the solid-state image sensor 4 is connected to the blur detection circuit 10, and the blur detection circuit 10 is vibrated to cause a front focus state (a front focus state) or a rear focus state (a rear focus state). It is configured to drive the focus lens 1 by rotating the focus motor 2 in a direction in which blurring is reduced.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-described configuration, the bimorph is located behind the solid-state image sensor (on the side opposite to the lens), and the electrical connection line for extracting the output signal of the solid-state image sensor is connected to the lens It is necessary to pull out from between the solid-state image pickup elements, and there is a problem in dust prevention during this time, and the total length from the lens front end to the bimorph rear end becomes long, which hinders downsizing of the device. Further, since only the both ends of the rectangular bimorph are supported, the bimorph is liable to warp, and the solid-state imaging device mounted in the center of the bimorph may be tilted with respect to the optical axis of the lens, causing one-sided blurring. Furthermore, since the end surfaces of the bimorph other than both ends are exposed, there is a problem that the bimorph is vulnerable to external impact.

In view of the above-mentioned problems, the present invention facilitates dust prevention between a lens and an image pickup element, shortens the overall length of an optical system, and enables downsizing of the apparatus, and also provides an automatic focusing apparatus having high performance and reliability. It is provided.

Means for Solving the Problems In order to solve the above problems, an automatic focusing apparatus according to the present invention includes a photographing lens for photographing a subject, an imaging means for converting an optical image by the photographing lens into an electric signal, and an outer circumference. A disk-shaped vibrating means having a fixed portion and a central portion vibrating in the optical axis direction of the photographing lens; an opening provided in the substantially central portion of the vibrating means and through which light rays from the photographing lens can pass; A cover member that covers between a surface of the plate-shaped vibrating means close to the taking lens and the taking lens, and the imaging from a side of the disc-like vibrating means that is far from the taking lens. An image pickup means holding member configured to close the opening by attaching a means, a control means for detecting an output signal from the image pickup means and focusing control of the photographing lens, the image pickup means and the Control hand And a conductive member having flexibility for electrically connecting the step and the step.

Working The present invention makes it possible to provide the vibrating means on the lens side of the image pickup means, and it is not necessary to pull out the lead wire of the image pickup means from between the image pickup means and the lens. In addition, the total length of the optical system itself can be shortened. In addition, since it does not form a ring-shaped vibrating means and its outer peripheral part is fixed, it is strong against impact,
Further, the image pickup means can be reliably vibrated only in the optical axis direction.

Embodiment Hereinafter, an automatic focus adjusting device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of the essential parts of an embodiment of the present invention, and FIG.
It is a rear view seen from the arrow A direction of a figure.

In FIG. 1, a focus ring 12 is provided in front of a taking lens 11 for taking an image of a subject, and a gear 1
It is coupled to the focus motor 15 via 3, 14. A solid-state image pickup device 16 such as a charge transfer device (CCD) for converting an optical image into an electric signal is arranged on the imaging surface of the taking lens 11. At the rear of the imaging lens 11,
A disk-shaped metal thin plate 17 having an opening 17a in the substantially central portion
A bimorph 19 in which ring-shaped piezoelectric elements 18a and 18b are adhered to both surfaces of the bimorph 19 is provided. It is firmly held by the outer frame holding screw 21. Further, an inner frame 22 (imaging means holding member) is fixed to the edge of the opening of the thin metal plate 17 by an inner frame holding screw 23, and the inner frame 22 has the solid-state imaging device 16.
The image pickup device holding plate 24 to which the
Is fixed by. The signal terminal 26 of the solid-state image pickup device 16 is made of a thin plate such as polyimide and has a flexible flexible printed board 27 (conductive member) soldered thereto. The other end of the flexible printed board 27 is a focus control circuit. 28 is connected.

The bimorph drive circuit 29 generates an AC voltage of 15 Hz, and causes the bimorph 19 to slightly vibrate, thus taking the photographing lens 1
The solid-state imaging device 16 is slightly driven in the direction of the optical axis 30 of 1.

The focus control circuit 28 has a bandpass filter (for example, a center frequency of 1 MHz) for detecting only high frequency components in the video signal obtained by the solid-state image sensor 16, and the solid-state image sensor 16 vibrates. By comparing the phase and the phase in which the high frequency component changes, it is detected whether it is the front pin or the rear pin, and the rotation direction of the focus motor 15 is determined. Therefore, the focus ring 12 is driven by the rotation of the focus motor 15, and the focus motor 15 is stopped at the point where the high frequency component becomes maximum, and the focusing is completed.

The bimorph drive circuit 29 controls the vibration amplitude of the bimorph 19 according to the aperture value of the taking lens 11, and when the aperture is open, the amplitude is small, and when the aperture is closed, the contact width is increased to increase the screen width. Blurring due to vibration is inconspicuous above, and changes in high frequency components can be detected.

As described above, according to this embodiment, since the ring-shaped bimorph is arranged in front of the solid-state image sensor (lens side) arranged on the image plane of the lens, the total length of the apparatus is equal to the thickness of the vibrating means. Can be shortened. Further, by fixing the entire outer peripheral portion of the bimorph, it is possible to make it resistant to impact. Further, since it is ring-shaped, the central portion vibrates only along the optical axis, and therefore the solid-state image pickup element can vibrate only in the optical axis direction, and one-sided blur can be prevented.

EFFECTS OF THE INVENTION As described above, the present invention includes a photographing lens for photographing a subject,
An image pickup means for converting an optical image by the taking lens into an electric signal, a disk-shaped vibrating means having a fixed outer peripheral portion and a central portion vibrating in the optical axis direction of the image pickup lens, and a substantially central portion of the vibrating means. An opening through which the light rays from the photographing lens can pass, a cover member that covers between the photographing lens and a surface of the disk-shaped vibrating means close to the photographing lens, and is fixed to the edge of the opening. An image pickup means holding member configured to close the opening by attaching the image pickup means from a side of the disk-shaped vibrating means far from the photographing lens, and detecting an output signal from the image pickup means. By providing the control means for controlling the focus of the photographing lens and the conductive member having flexibility for electrically connecting the image pickup means and the control means, the lens and the image pickup means are connected. Dustproof between Becomes, overall length can be shortened, it is possible to prevent the inclination due to side blur of the imaging means, it is possible to impact resistance improving. From this, it is possible to provide an automatic focus adjustment device with high blur detection accuracy and high reliability.

[Brief description of drawings]

FIG. 1 is a block diagram of an essential part of an automatic focus adjusting device according to an embodiment of the present invention, FIG. 2 is a rear view of FIG. 1, FIG. 3 is a block diagram of a conventional automatic focus adjusting device, and FIG. FIG. 4 is a rear view of FIG. 11 ... Shooting lens, 16 ... Solid-state image sensor, 19 ...
Bimorph, 22 ... Inner frame, 28 ... Focus control circuit.

Claims (1)

[Claims] 1. A photographing lens for photographing a subject, and an image pickup means for converting an optical image formed by the photographing lens into an electric signal.
A disk-shaped vibrating means having a fixed outer peripheral portion and a central portion vibrating in the optical axis direction of the photographing lens, and an opening through which a light beam from the photographing lens is provided substantially at the central portion of the vibrating means,
A cover member that covers a space between the photographing lens and a surface of the disc-shaped vibrating unit near the photographing lens, and a side of the disc-shaped vibrating unit that is fixed to the edge of the opening and is far from the photographing lens. An image pickup means holding member configured to close the opening by attaching the image pickup means, a control means for detecting an output signal from the image pickup means and controlling focus of the photographing lens, and the image pickup means. And an electrically conductive member having flexibility for electrically connecting between the control means and the control means.