JPH0918771A - Automatic focusing video camera - Google Patents

Abstract

PURPOSE: To prevent occurrence of a damage to an image pickup element due to shock at collision by providing a buffer member arranged in the vicinity of a moving end point and to which an image pickup means is pressed into contact before the image pickup means collides with a stationary member so as to reduce the shock at collision. CONSTITUTION: A sponge 100 is adhered to a moving part of a shaft mount plate 91 and a sponge 101 is adhered to a center yoke 23 so as to be orthogonal to an optical axis. The sponges 100, 101 have a sufficient elasticity, and a shock at collision with the shaft mount plate 91 due to a gravity exerted by directing the lens upward and a centrifugal force exerted by shaking the camera is sufficiently relaxed at transportation when a power supply of the video camera is turned off. Thus, when the moving part 60 is moved by a external force and butted to other stationary member at both moving ends, the shock is sufficiently realized by the sponges 100, 101, then the shock exerted to a CCD 2, electronic components used to drive the CCD 2, and a voice coil motor 53 is sufficiently suppressed to prevent damage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera and an electronic still camera having an automatic focusing function.

[0002]

2. Description of the Related Art Conventionally, in an automatic focusing apparatus used for an image pickup apparatus such as a video camera, a method of using a video signal itself obtained from an image pickup element for evaluating a focus control state has been favored. Such a method has essentially no parallax, and has many excellent features such as accurate focusing even when the depth of field is shallow or the subject is located at a long distance. doing. Moreover, according to this method, it is not necessary to separately provide a special sensor for autofocus, and the mechanism is extremely simple.

As an example of a focus control method using such a video signal, a control method called a so-called hill-climbing servo system has been conventionally known. An autofocus device using the hill-climbing servo system is described in, for example, Japanese Patent Application Laid-Open No. 63-215268 (H04N5 / 232). Briefly, one screen of the high frequency component of the picked-up image signal, that is, 1 The integrated value of the field period is 1
The focus evaluation value is detected for each field, this focus evaluation value is constantly compared with the one before, and the focus lens position is continuously slightly displaced so that the focus evaluation value always has the maximum value. Is to be detected and held.

In the above-mentioned prior art, as a means for changing the relative position of the lens in the optical axis direction with respect to the image pickup device, a motor such as a stepping motor or a DC motor, and a rotational force obtained by driving this motor are used for the lens or the image pickup device. Since it is composed of a driving force transmission mechanism for converting into a driving force for linear movement, it is difficult to reduce the size and weight of the mechanism, and power consumption becomes a problem.

Therefore, by displacing the lens or the image pickup device with a linear motor, the size and weight of the mechanism can be reduced, and the power consumption can be further reduced. FIG. 2 shows an example of using a linear motor as a drive source in this way.

In FIG. 2, the focus adjusting device of the video camera is configured to move the image pickup element in the optical axis direction by a voice coil motor to adjust the focus. In the following description, the CCD 2 and this CCD are integrated. The member that displaces to is the movable part.

The operation of the lens 1 will be described more specifically.
The image formed by is photoelectrically converted by CCD2,
The image pickup output is converted into a video signal by the image pickup circuit 3, amplified by the amplifier circuit 4 to a predetermined level, and then supplied to the recording system of the VTR and input to the focus evaluation value generation circuit 5.

As shown in FIG. 3, the focus evaluation value generating circuit 5 is a high-pass filter (H which extracts high frequency components of a video signal).
PF) 5a, an A / D converter 5b for converting the HPF 5a output into a digital value, and a gate circuit 5c for passing only the value in the focus area set in the center of the screen in the A / D converted output. , A digital integrator 5 for digitally integrating the gate output over one field period
The output of the focus evaluation value generation circuit 5 is a digital integrated value of the high frequency component of the video signal over one field period, which is used as a focus evaluation value in the arithmetic unit 6 in the subsequent stage.
And output to the memory 50.

In the arithmetic unit 6, as the initial state, a drive signal of the voltage level m is issued to displace the CCD 2 in one direction on the optical axis, while the latest focus evaluation value from the focus evaluation value generating circuit 5 and the memory 50 are stored. The focus evaluation value of the previous field stored is compared to determine the in-focus state of the imaging screen. If the latest focus evaluation value is larger, it is determined that the focus position is in the current movement direction. When the drive signal of the voltage level m is continuously output, and conversely, the focus evaluation value one field before is larger, it is determined that the focus signal is moving away from the focus position, and the drive signal voltage level is changed from m. CC instead of n
The CCD 2 is brought to the in-focus position where the focus evaluation value is maximized by reversing the direction of transition of D2.

The CCD 2 is moved in the direction in which the focus evaluation value increases.
Is moved, and when the focus evaluation value decreases too much past the in-focus position where the focus evaluation value becomes maximum, the moving direction of the CCD 2 is reversed and the arithmetic unit 6 returns to the position where it takes the maximum value and stops. Emit.

The focus evaluation value one field before the latest field is stored in the memory 50, and when the comparison operation in the arithmetic unit 6 is completed, the latest focus evaluation value obtained from the focus evaluation value generation circuit 5 is used. The stored contents are updated.

The voice coil motor 53, which is a drive source for the movable portion including the CCD 2, is a kind of linear motor and has a structure as shown in FIGS. 5 and 6 (cross-sectional view taken along the line CC 'in FIG. 5). Basically, it has the same structure principle as the round speaker. That is, each of the four center yokes 23 having a U-shaped cross section is fixed along the four sides of the square to the yoke fixing portion 90a of the fixed base 90 of the camera unit of the video camera. A permanent magnet 24 with one magnetic pole facing is fixed to the inner surface of the yoke 23. Further, the shaft mounting plate 9 is provided in the camera unit in parallel with the yoke fixing portion 90a.
1 is fixed, one end of two guide shafts 51a and 51b extending in the optical axis direction is coupled to the mounting plate 91, and the other end is coupled to the yoke fixing portion 90a.

Lenses 81 and 82 are fixed between the center-yoke 23 and the opening 90e of the fixed base 90.

On the other hand, a quadrangular cylindrical bobbin 22 in which a conductive wire is wound as a drive coil (voice coil) 20 is fixed so as to face the permanent magnets 24 so as to project along the optical axis. A base 52 is arranged in the unit, and fitting holes 52a and 52b are provided on a diagonal line of the movable base 52.
By forming the guide shafts 51a and 51b into the fitting holes 52a and 52b, the movable base 52 is supported in the camera unit so as to be movable back and forth in the optical axis direction. In addition, an opening 52c for allowing incident light to pass through is provided in the front part of the movable base 52 (the side close to the lens).
Is formed, and the CCD 2 is fixed to the rear part (the side far from the lens). Reference numerals 83, 84, and 85 are optical filters, such as an infrared cut filter and an optical LPF, which are arranged in front of the CCD in a normal video camera, and the incident light passing through the lenses 81 and 82 passes through the opening 52c. The signal passes through the optical filters 83, 84 and 85, reaches the CCD 2, is imaged on the CCD, and the signal photoelectrically converted therein is output to the outside of the camera unit via the flexible cable 71 and supplied to the signal processing unit. To be done. Reference numeral 90d denotes a cutout portion formed in the fixed base 90 for guiding the cable 71 to the outside. Further, 97 is a movable base 52
LED 98 fixed to the fixed base 90 is a light receiving unit fixed to the fixed base 90 so as to face the LED, and the pair forms a position detection unit that detects the position of the movable unit 60 in the optical axis direction. doing.

When a current flows through the drive coil 20, the drive coil 20, the bobbin 22, the movable base 52, and the CCD 2
The movable portion 60 is guided by the guide shafts 51a and 51b and integrally moves in the optical axis direction indicated by the arrow.

Here, the drive signal to the voice coil motor 53 has the following characteristics. That is, in the voice coil motor 53, the driving direction of the bobbin 22 changes depending on the direction of the current flowing through the driving coil 20, and the driving speed changes according to the magnitude of the current. Therefore, in order to drive and control the voice coil motor 53 by the output of the arithmetic unit 6, as shown in FIG.
EF is applied, and the drive voltage VD, which is the voltage of the drive signal from the calculator 6, is applied to the other side, and the direction of the current and the magnitude of the current may be changed according to the magnitude relationship of VD with respect to VREF.

By the way, in the example shown in FIG. 2, only the coil 20 is shown for simplification, and the voice coil motor 5 is shown.
The other parts of 3 are omitted in the drawing.

[0018]

In the drive system of the prior art described above, since the linear motor is used as the drive source, for example, even when the gear is stopped and the movable portion is always connected, the teeth of the gear are stopped. It is not a configuration in which the movable part is less likely to be displaced due to such reasons. Therefore, the following problems occur when the power of the video camera is turned off. That is, in the power-off state, no current flows in the drive coil of the voice coil motor, and it becomes impossible to displace the movable part by electromagnetic force and restrict the position at a specific position.
While being supported by 51b, it is in a free state in the optical axis direction, and when an external force in the optical axis direction is applied to the movable part in this power-off state, a current is passed through the driving coil to cancel the external force. Since electromagnetic force cannot be generated, the movable part continues to move as long as external force is applied.

Therefore, when the video camera is transported after the photographing is finished and the power is turned off, the movable portion starts to move in the optical axis direction due to the influence of external force such as gravity and centrifugal force, and the shaft mounting plate and Occurrence of a collision with a center yoke, a fixed base, or the like. Due to this collision, a large impact force is applied to the movable portion, and if the impact is repeatedly applied, the CCD and other electronic components mounted on the movable portion may be damaged, and the driving portion including the voice coil motor may be damaged. May damage the structure of.

To solve this problem, turn off the power
In such a case, it may be possible to provide a mechanism for holding the movable part in a fixed position, but this would lead to an increase in the size of the device and an increase in production cost.

[0021]

SUMMARY OF THE INVENTION The present invention is an autofocus video camera of the type in which a CCD is displaced in the optical axis direction with respect to a lens by a driving means, and the movement end point of the CCD in which a fixed member is arranged is buffered. It is characterized by including a member, and further characterized in that the driving means is a linear motor.

[0022]

Since the present invention is constructed as described above, when the image pickup element is forcibly moved in the optical axis direction by applying an external force with the power source to the driving means cut off, the movement end is reached. Immediately immediately before, the shock absorbing member cushions the shock at the time of collision between the fixed member and the image pickup device at the moving end, by the shock absorbing member.

[0023]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a structural view of a camera unit of a video camera according to this embodiment, and FIG. 4 is a sectional view taken along the line CC '.
The same parts as those of the conventional technique shown in FIGS. 5 and 6 are designated by the same reference numerals and the description thereof will be omitted.

The difference from the conventional camera unit shown in FIG. 5 is that the sponge 10 is provided on the movable portion side of the shaft mounting plate 91.
0 is adhered, and the sponge 101 is also adhered to the center yoke 23 so as to be orthogonal to the optical axis.
These sponges 100, 101 have sufficient elasticity,
During transportation of the video camera in the power-off state, the movable base 52 to which the CCD 2 is fixed is supported by the guide shafts 51a and 51b due to gravity applied by turning the lens side upward and centrifugal force applied by shaking the camera. While moving in the optical axis direction, the movable base 52 moves the lens 8
When the movable base 52 reaches a position immediately before one moving end in which the movable base 52 comes into contact with the shaft mounting plate 91 by moving in the direction away from 2 (the direction of arrow A), the movable base 52 moves to the sponge 1
00, the sponge 100 is deformed, and the impact force at the time of collision with the shaft mounting plate 100 is sufficiently relaxed.

On the contrary, the movable base 52 is moved in a direction (direction of arrow B) in which the movable base 52 approaches the lens 82 by gravity or centrifugal force applied by making the lens side downward.
When the bobbin 22 disposed integrally with the bobbin 2 reaches the position immediately before the other moving end that abuts the center yoke 23, the bobbin 2
The tip of 2 comes into contact with the sponge 101 so that the sponge 10
1 is deformed, and the impact force at the time of collision with the center yoke 23 is sufficiently relaxed.

As described above, when the movable portion 60 is moved by an external force and collides with other fixed members at both moving ends, the impact force is sufficiently alleviated by the sponges 100 and 101, so that the CCD 2 and the like. The electronic components that drive the CCD 2 and the voice coil motor 53 can be sufficiently suppressed from impacts and damage can be prevented.

In the above embodiment, the sponges 100 and 101 are used as the cushioning member, but the cushioning member is not limited to this, and soft rubber or the like which can absorb impact can be substituted.

[0028]

As described above, according to the present invention, an external force in the direction of the optical axis is applied to the image pickup means in a state where the driving means is inoperative,
When the imaging means moves and reaches the moving end and collides with another member, the imaging means comes into contact with the cushioning member before the collision to sufficiently reduce the impact at the time of collision, and the impact at the time of collision causes the imaging element It is possible to prevent damage. Further, when a linear motor that moves integrally with the image pickup means is used as the driving means, it is possible to prevent damage to the linear motor due to the impact at the time of collision.

[Brief description of the drawings]

FIG. 1 is a structural explanatory view of a camera unit according to an embodiment of the present invention.

FIG. 2 is a block diagram of a CCD drive type autofocus video camera.

FIG. 3 is a block diagram of a main part of FIG.

FIG. 4 is a sectional view taken along the line C-C ′ of the embodiment of the present invention.

FIG. 5 is a structural explanatory view of a conventional camera unit.

FIG. 6 is a sectional view of a conventional camera unit.

[Explanation of symbols]

 81 lens 2 CCD 53 voice coil motor 52 movable base 91 shaft mounting plate 23 center yoke 100 sponge 101 sponge

Claims (2)

[Claims] 1. An image pickup device having an image pickup device for photoelectrically converting light incident through a lens, a driving device for displacing the image pickup device in the optical axis direction with respect to the lens, and a moving end point of the image pickup device. An autofocus video camera comprising: a fixed member that is arranged; and a buffer member that is arranged near the moving end point and that is in contact with the image pickup unit before the image pickup unit collides with the fixed member. 2. The autofocus video camera according to claim 1, wherein the driving means is a linear motor.