JPS5833367A - Burn preventing system for surface of video camera image pickup element - Google Patents

Abstract

PURPOSE:To reduce the power consumption of a battery and to prevent the burn on the face of an image pickup element, by driving a focusing mechanism for a prescribed time by a driving means after disconnecting the power supply of the focusing mechanism and shifting the face of the pickup element outside the image forming range of the sunbeam, etc. CONSTITUTION:In the normal operation mode of a camera, a power supply switch 6 is turned on to supply the power of a battery 5 to a camera circuit 3. Then a lens 1 converts the image of a subject formed at an image pickup element 2 into the electric signal and delivers it. When the switch 6 is opened, the power of the battery 5 is supplied to a motor 8 that drives a focusing mechanism and a control circuit 7 via an electronic switch 4. Then the circuit 7 detects the open state of the switch 6, and the motor 8 is driven to give a rotary control to the position of the master lens of the lens 1 toward the closest direction. Then the driving of the motor 8 is stopped after a prescribed time, and at the same time the switch 4 is opened. The image forming face of the element 2 is shifted outside the image forming range of the sunbeam, etc. by the control of the circuit 7. Thus the pickup face of the element 2 is protected from burning, and at the same time the power consumption of the battery 5 is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the prevention of burnout of the surface of an image sensor in a video camera due to sunlight or the like.

A configuration in which a spring is connected to the diaphragm blade of a video camera with an automatic iris function, especially a home video camera, and the spring completely closes the diaphragm blade when the power of the video camera is turned off and the image capturing is completed. There are many things that became. This prevents the imaging surface of the video camera's image sensor from being exposed to strong rays of light such as sunlight that form on the lens and cause burnout due to heat generation, making it unusable for further use. This is the method to do it. Although this method completely achieves its purpose in terms of preventing burnout, it has a drawback caused by the structure itself in that the aperture blades are constantly pulled in the closing direction by a spring. In other words, while taking pictures, the diaphragm blades are naturally controlled to be opened to the appropriate extent for optimal imaging in that imaging state, but this control system always drives the spring in the open direction. Must be.

As a result, it is difficult to design a control system, and at the same time, the current required to resist the spring is consumed while the video camera is in use, which accelerates battery consumption.

SUMMARY OF THE INVENTION An object of the present invention is to provide a video camera that eliminates the drawbacks of the prior art, significantly reduces unnecessary battery consumption, and prevents burnout of the imaging surface.

Conventional burnout prevention devices prevent sunlight incident on the lens from reaching the imaging surface by fully closing the aperture when the WlfJl of the video camera is not turned on.The present invention prevents burnout of the imaging surface. It is important to note that this is not caused by sunlight reaching the imaging surface itself, but that even if sunlight reaches the imaging surface, it will not occur unless the image is formed on this surface. In other words, sunlight is considered to be incident light from an infinite distance, so when the power of the video camera is turned off, the lens is driven by a motor to bring the focus point to the closest position, for example 11.
1&, it is possible to prevent burnout due to image formation. However, with normal zoom lenses that focus at the very front of the lens, the depth of focus is deep when the zoom magnification is low, so even if you focus at close range, the imaging range will almost extend to infinity, making it difficult to reach your objective. I can't.

Therefore, by moving all or part of the master lens group at the rear of the lens instead of the frontmost part of the lens as a focusing mechanism, the depth of focus is made constant regardless of the zoom magnification, thereby achieving the objective.

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram showing an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between the lens position and the amount of blur of an object at an infinite distance, that is, the position of the sun in this case.

In Fig. 1, 1 is a lens that performs focusing by moving part or all of the master lens group, 2 is an image sensor, 3 is a camera circuit of a video camera, 4 is an electronic switch, and 5 is the entire device. Battery to supply power, 6 is a power switch that operates the camera's power supply, 7 is an electronic switch when the power switch 6 is closed, and a certain period of time after the switch is closed, the power switch, and the camera are opened. 8 is a control circuit that drives the motor 8 for a certain period of time from the moment the electronic switch is closed and the power switch is opened. 8 is a motor that moves the master lens of the lens 1 from the output button of the control circuit 7. be.

In the configuration shown in the figure, during normal camera operation, switch y-
6 is closed, the camera circuit 3 converts the subject image formed by the lens 1 onto the image sensor 2 into an electrical signal and outputs it. Now, when the power switch y-6 is opened, the camera circuit 3 and battery 5 are disconnected and imaging is stopped, but power is supplied to the control circuit 7 and motor 8 from the battery 5 via the electronic switch 4. It is possible to operate because it is present.

The control circuit 7 detects that the power switch Y-6 is open, and drives the lens 8t to control the rotation of the master lens wall amount of the lens 1 in the near direction. Here, since the master lens position and ω distance object blur line have the relationship shown in FIG. 2 regardless of the zoom magnification of the lens 1, no matter where the master lens position is when the power switch 6 is opened, the motor 8 If it is operated for a time longer than the time when the master lens position exceeds the value shown in Fig. 2, ■ the distance object, in this case sunlight, on the imaging plane of the image sensor 2 will be burnt out. There is not a sufficient amount above B. The control circuit 7 drives the motor for a certain period of time, opens the electronic switch after t, and discharges the battery 5.
from all loads.

As explained above using Figure #11 and Figure 2, the video camera according to the present invention moves the master lens position before turning off the power to prevent sunlight from forming an image on the imaging element, so it is possible to avoid burnout. There is no possibility of this occurring. In this device, as in the conventional case, the diaphragm is used during camera operation.
Rather than consuming power to overcome the negative effects, the power is only driven for a certain period of time, for example, 1 to 2 seconds, when the power is turned off, so unnecessary battery consumption can be minimized. It should be noted that the motor, control circuit, etc. used in the configuration of the device of the present invention are too expensive and heavy to install inside a video camera to avoid solar burnout, which is the direct objective of the present invention. If you share the functions necessary for a video camera, such as the motor, control circuit, or part of the microcomputer already installed for an autofocus device, you can practically reduce the price and weight (which can be realized easily). The effect of the present invention is great because
The purpose of this invention is to move the lens to a position where it is out of focus, so we applied the present invention to a normal zoom lens with the understanding that the objective would not be achieved if the zoom magnification was low.

Needless to say, it's okay to do so.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between the lens position and the amount of blur of an object at an infinite distance. Description of symbols 1...Lens, 2...Image sensor, 3...Camera circuit, 4...Electronic switch, P, 5...Battery, 6...Power switch, H, 7... Control circuit, 8...motor. Representative Patent Attorney Susuki 1) Kosai Toshi 1 Figure

Claims (1)

[Claims] 1) In a video camera equipped with a driving means for electrically driving a lens focusing mechanism, after the operating power is cut off, the driving means drives the focusing mechanism of the lens for a predetermined period of time so that the image sensor surface is aligned with the sun. Placed outside the range of interference such as light 1-Characteristic method to prevent burnout of the video camera element surface.