JPH0636569B2 - Imaging device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device that can be used in an optical system of a video camera.

2. Description of the Related Art Conventionally, this type of image pickup device is configured as shown in FIG. 4 or FIG. In FIG. 4, the light that has passed through the imaging lens system 4 including the focusing lens group 1, the zoom lens group 2, the master lens group 3 and the like has an optical path length changing lens 5 and an optical filter as an optical low pass filter. 6 is used to form an image on the solid-state image sensor 7. The optical path length changing lens 5 is held via a thin annular metal plate 8, and annular piezoelectric elements 9a and 9b bonded to both surfaces of the metal plate 8 are used as oscillators 10.
When driven by the signal, the optical path length changing lens 5 vibrates in the direction of the optical axis (A) of the photographing lens system 4 by a small amount, and the optical path length of the light toward the solid-state image sensor 7 changes by a small amount. repeat. The configuration of the fine movement device is described in detail in Japanese Patent Application Laid-Open No. 60-179710 filed by the present applicant.

An output signal obtained by the solid-state image pickup device 7 is amplified by an amplifier 11, and a frequency detector 12 detects a high frequency signal including a vibration frequency component of the piezoelectric elements 9a, 9b. The phase of the signal detected by the frequency detector 12 and the phase of the output signal of the oscillator 10 are compared by the phase comparator 13, the control unit 14 detects the direction of defocus, and the output of the solid-state image sensor 7 is output. The focusing lens group 1 is moved in the direction of the optical axis (A) by the motor 15 so that the voltage reaches the peak value, and the focus is adjusted.

The operation principle of the control system for driving the focusing lens 1 based on the output signal of the solid-state image sensor 7 is described in detail in Japanese Patent Application Laid-Open No. 60-42723 filed by the applicant of the present invention.

In the apparatus shown in FIG. 4, the solid-state image sensor 7 is fixed and the optical path length varying lens 5 is vibrating.
As shown in FIG. 5, there is a structure in which the solid-state imaging device 7 is held by a metal plate 8 having piezoelectric elements 9a and 9b attached on both sides. In FIG. 5, the same reference numerals are given to those having the same operation as in FIG.

Problems to be Solved by the Invention In order to reduce the size and weight of the image pickup apparatus in such a conventional configuration, in the case of FIG. 4 in which the solid-state image pickup element 7 is arranged on the fixed side, the fixed state is fixed. Also in the case of FIG. 5 in which the image pickup device 7 is arranged on the oscillating movable side, the distance B between the optical filter 6 and the solid-state image pickup device 7 is shortened, and a position near the solid-state image pickup device 7 having a close focus point, That is, it is effective to make the optical filter 6 smaller and lighter by making the optical filter 6 act on the light at the position where the light flux is narrowed down. Since the planar shape of the optical filter 6 when viewed from the subject side is a quadrangle as shown in FIG. 6 in the related art, such an optical filter 6 is mounted on the solid-state image sensor 7 as described above.
When the optical filter 6 is brought closer to, the planar quadrangle of the optical filter 6 can be made smaller than that in which the optical filter 6 and the solid-state image sensor 7 are arranged at the interval B as shown in FIGS. 4 and 5. However, under the present circumstances, further weight reduction of the optical filter 6 is required.

An object of the present invention is to further reduce the size and weight of an optical filter without deteriorating the optical characteristics, and to further reduce the size and weight of an imaging device.

Means for Solving the Problems An image pickup apparatus of the present invention includes a photographing lens system for photographing a subject, an image pickup device for converting an optical image formed by the photographing lens system into an electric signal, and a long side of a light receiving window of the image pickup device. Is a linear shape along the two sides, the remaining two sides along the short side of the light receiving window of the image sensor has an outwardly extending arc-shaped planar shape, and the front surface of the light receiving window of the image sensor. A holding unit that holds the optical filter so as to always keep a fixed position at a predetermined position, a vibrating unit that vibrates the image sensor and the optical filter in the optical axis direction of the photographing lens system, and the image sensor. The fixing means is fixed to the vibrating means, and the focusing means for detecting the shift of the focus by using the change of the output signal of the image pickup device caused by the vibrating means.

Operation According to this configuration, the four corners of the optical filter having a quadrangular planar shape that do not affect the optical characteristics of the light flux reaching the light receiving window of the image sensor are removed, so that the optical characteristics are not impaired. The weight can be reduced, and the focus direction of the subject can be reliably detected.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. The photographing lens system and the electric circuit for focus control thereof are the same as in FIG. 5, but the focus control operation will be described in detail here.

The output signal of the solid-state image sensor 7 is amplified by the amplifier 11, and the high frequency component is extracted by the frequency detector 12. Here, the oscillator 10 is oscillating at, for example, 15 Hz, and the frequency detector
The high-frequency component that is the output of 12 is a waveform modulated at 15 Hz. This oscillation frequency of 15 Hz is the solid-state image sensor 7
The image obtained from the output signal of is not limited to this value as long as it has a frequency that does not appear unnatural to human eyes. By comparing the output of the frequency detector 12 and the output of the oscillator 10 in phase by the phase comparator 13, information on whether the subject is currently in front of or behind the subject is obtained, and based on that, the control unit 14 , The direction of movement of the focusing lens group 1 is determined via the motor 15. Then, a control operation is performed to detect that the result of the phase comparison is in focus at the lens position where the vibration of the solid-state image sensor 7 outputs plus or minus.

FIG. 1 is a vertical cross-sectional view of the main part in one embodiment of the present invention. In FIG. 1, a solid-state image sensor 7 as an image sensor
Is attached to the movable side holder 16 with screws 17a and 17b,
The movable side holder 16 is attached to the holder 18 via the annular metal plate 8 having the annular piezoelectric elements 9a and 9bb attached on both sides. Reference numeral 19 denotes a ring screwed onto the outer peripheral portion of the tip of the movable side holder 16, and the inner peripheral portion of the metal plate 8 is sandwiched between the ring 19 and the movable side holder 16. Reference numeral 20 is a ring screwed into the inner peripheral portion of the holder 18, and the outer peripheral portion of the metal plate 8 is sandwiched between the ring 20 and the holder 18. The optical filter 21 interposed between the taking lens system 4 and the solid-state image pickup device 7 is closely attached to the solid-state image pickup device 7 by means of adhesion or the like, and the movable side holder 16 is vibrated by the piezoelectric elements 9a and 9b. The solid-state image sensor 7 and the optical filter 21 vibrate integrally in the direction of the optical axis (A).

In FIG. 2, reference numeral 22 denotes a light receiving window of the solid-state image pickup device 7 viewed from the subject side through the optical filter 21, and a side (c) along the long side (a) (b) of the light receiving window 22 of the optical filter 21. (d) is a straight line parallel to the long sides (a) and (b), respectively, and the short side of the light receiving window 22.
The remaining two sides (g) and (h) along (e) and (f) are formed in an outwardly extending arc shape.

As described above, in contrast to the conventional optical filter 6 having a quadrangular planar shape as shown by the phantom line in FIG. 2, the optical filter 21 of the present embodiment has a corner portion (which does not affect the optical characteristics of the solid-state imaging device 7). Since it has a planar shape in which i) to (l) are removed, it can be made smaller and lighter than the rectangular optical filter 6, and the optical characteristics are not impaired.

In the above embodiment, the case where the solid-state image sensor 7 is vibrated as shown in FIG. 5 to change the optical path length for focusing is explained, but the optical filter 21 changes the optical path as shown in FIG. It is similarly effective for downsizing and weight reduction even in an image pickup device in which the lens 5 is vibrated for focusing.

In particular, in the case of FIG. 1 in which the solid-state image pickup device 7 is vibrated to change the optical path length for focusing, the piezoelectric element 9 is used by using the optical filter 21 having a small mass.
The load applied to a and 9b can be reduced. For example, the piezoelectric element 9 when the optical axis (A) is vertically oriented and when it is horizontally oriented.
This is particularly effective in recent miniaturized video cameras, in which the load fluctuations applied to a and 9b can be reduced and the vibration width of the solid-state image sensor 7 can be kept stable regardless of the shooting posture.

Furthermore, by keeping the relative positional relationship between the solid-state image sensor 7 and the optical filter 21 constant at all times,
Since the filter characteristics of the optical filter 21 are not deteriorated even when the lens is vibrated, it is possible to reliably obtain the image signal for focusing.

In each of the above embodiments, the vibrating device 23 for vibrating the optical filter and the image pickup device in the direction of the optical axis (A) of the taking lens system 4 is composed of the metal plate 8 and the piezoelectric elements 9a and 9b. As described above, the vibrating device 23 is a combination of a magnetic plate and a coil facing the magnetic plate. One of the magnetic plate and the coil is connected to the image sensor and the optical filter, or the permanent magnet and the coil are combined. In the same manner, a configuration in which one of the permanent magnet and the coil is coupled to the image sensor and the optical filter can be used in the same manner.

As described above, according to the present invention, by keeping the relative positional relationship between the image sensor and the optical filter always constant, even if the image sensor is vibrated, the filter characteristics of the optical filter are not deteriorated. Therefore, the video signal for focusing can be surely obtained. Further, since the optical filter has a shape in which the four corner portions that do not affect the optical characteristics of the light flux reaching the light receiving window of the image sensor are removed, it is possible to suggest superimposing the optical filters. Therefore, the attitude difference of the vibrating means due to gravity when the photographing lens is directed directly upward and downward is decreased (that is, the attitude difference is decreased as the object vibrated by the vibrating means is lighter), and the image pickup element of the imaging element is decreased. It is possible to reduce the focus change due to the posture difference and also reduce the power consumption of the vibrating means.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a mounting portion of an image pickup device of an embodiment of an automatic focus adjustment device of the present invention, FIG. 2 is an enlarged plan view of the image pickup device in FIG. FIG. 4 is an exploded perspective view of the image sensor and the optical filter of FIG. 1, FIG. 4 is a configuration diagram of a conventional automatic focus adjusting device that vibrates an optical path length changing lens to change the optical path length, and FIG. FIG. 6 is a configuration diagram of a conventional automatic focusing device that vibrates the element to change the optical path length, and FIG. 6 is a perspective view showing the mounting positions of the optical filter and the image pickup element in FIGS. 4 and 5. 4 ... Shooting lens system, 7 ... Solid-state imaging device [imaging device], 21 ... Optical filter, 22 ... Light receiving window, A ... Optical axis, a, b ... Long side, c, d ... Long The sides of the optical filter 21 along the sides a and b, e, f ... Short side, g, h ... Short side e,
The side of the optical filter 21 along f.

Claims (1)

[Claims] 1. A photographing lens system for photographing a subject, an image pickup device for converting an optical image formed by the photographing lens system into an electric signal, and two sides along a long side of a light receiving window of the image pickup device are linear. An optical filter in which the remaining two sides along the short side of the light receiving window of the image sensor have an arc-shaped planar shape with an outward expansion,
Holding means for holding the optical filter so as to always keep a constant position at a predetermined position on the front surface of the light receiving window of the image pickup device, and vibrating the image pickup device and the optical filter in the optical axis direction of the photographing lens system. A vibrating unit, a fixing unit that fixes the image pickup device to the vibrating unit, and a focusing unit that detects a focus shift by using a change in an output signal of the image pickup device caused by the vibrating unit. Image pickup device.