JPH0591399A - Exposure control device - Google Patents

Abstract

(57) [Summary] [Purpose] Conventionally, in an exposure control device (auto iris) mounted on a video camera, the output of the Hall element that detects the movement amount of the diaphragm blade is temperature-compensated. Since the control signal (driving signal) for the driving source is not temperature-compensated, it is not always possible to perform accurate exposure control with respect to temperature fluctuations. It is an object of the present invention to provide an improved exposure control device that allows more accurate exposure control than this known exposure control device. In the device of the present invention, a variation in the response time of the diaphragm blade is detected, a correction coefficient is calculated based on the magnitude of the variation in the response time, and the drive signal (control signal) is calculated by the correction coefficient. The drive source was controlled by modification.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure control device suitable for optical equipment such as video cameras.

[0002]

2. Description of the Related Art In a conventional video camera system,
Generally, the temperature compensation of the iris uses the temperature characteristic of the diode in order to cancel the temperature difference of the aperture value detection by the hall element which is the iris encoder. As a result,
The aperture value is accurately detected within a certain temperature range. Since the aperture value detection has no temperature dependency, focusing or table search for detecting the aperture value can be performed accurately.

[0003]

However, in the temperature compensation of the iris described above, the response time in which the iris opens and closes with respect to the signal output by the lens microcomputer for driving the diaphragm blades is not temperature-compensated. The main reason for this is that, for example, the magnetic force of the magnet in the iris IG meter (electromagnetic actuator for driving the diaphragm blades) decreases with temperature. Further, mechanical loads (friction force of blades and force of springs) are not always the same in the same type of iris. It is also possible that the mechanical load changes depending on the temperature. Therefore, the response time of the iris changes.

The object of the present invention is to solve the problems existing in the prior art as described above, and to perform the control for compensating for the fluctuation of the response time of the iris caused by the temperature change, so that the operation accuracy and reliability are higher than those of the conventional device. It is to provide an exposure control device having high property.

[0005]

In the exposure control device according to the present invention, the iris response time is measured by opening and closing the iris with respect to the reference iris drive signal, and the optimum response time is obtained from the result. Output drive signal,
The feature is that the iris is controlled.

[0006]

According to the exposure control device of the present invention, the temperature of the response time of the iris can be compensated, and the difference in response time due to mechanical factors can be eliminated. Therefore, an accurate diaphragm operation can be performed.

[0007]

Embodiments of the exposure control device of the present invention will be described in detail below.

FIG. 1 is a schematic view showing an interchangeable lens provided with an exposure control device according to the present invention and a video camera main body corresponding to the interchangeable lens. 1 is an interchangeable lens and 2 is an interchangeable lens. A video camera body (hereinafter simply referred to as a camera) having a lens-compatible configuration. By these electrical contacts arranged on the mount 3,
A communication transmission line 4 is formed for performing various types of communication such as initialization information and control information.

Inside the lens, there is a control microcomputer 5 for controlling all the lens side control (hereinafter referred to as a lens microcomputer) and a camera side microcomputer 6 (hereinafter referred to as a camera microcomputer). Drive control is performed on the basis of the data supplied via the communication transmission line 4.

Next, information regarding the diaphragm is given by the driver 7
To drive the IG meter 8. IG meter 8
A blade 9 for adjusting the amount of light is attached to the. Further, an encoder 10 for detecting the diaphragm amount is attached to the IG meter 8. Reference numeral 11 is a lens for forming an afocal region.

When a camera user operates a power switch (not shown) to turn on the power when using the video camera having the structure shown in the drawing, the lens microcomputer 5 outputs a reference drive signal to the driver 7 to stop the diaphragm. Open and close the blade 9 once,
Measure the response time. The result is stored in the memory of the lens microcomputer 5.

The light entering the interchangeable lens 2 is the IG meter 8
The amount of light is adjusted by the blades 9 and enters the image sensor 12. The image pickup device 12 converts light into an electric signal, the camera signal processing circuit 13 converts the light into a luminance signal, the circuit 14 performs integral detection, and inputs the luminance signal to the camera microcomputer 6. The camera microcomputer 6 transmits to the lens microcomputer 5 the difference between the light amount value input to the image sensor 12 and the proper exposure. The lens microcomputer 5 adjusts the iris drive signal based on the transmitted information and the response time obtained when the power is turned on and outputs the adjusted iris drive signal to the driver 7 to drive the diaphragm until proper exposure.

The operation when the power is turned on is shown in the flowchart of FIG.

At A1, the driver 7 receives a reference drive signal (from the aperture stop to the opening direction C--O) from the lens microcomputer 5.
Output to. At A2, the aperture blade 9 measures the response time from the aperture stop to the opening. At A3, the response time (C-
O) is stored in the lens microcomputer 5. Next, in A4, the lens microcomputer 5 outputs a reference drive signal (from the open state to the stop cutting direction OC) to the driver 7. At A5, the time from when the aperture blade 9 is opened to when it is fully apertured is measured. At A6, the response time (O−C) is stored in the lens microcomputer 5. Therefore, in A7, the coefficient to be corrected is calculated from the two response times. This coefficient is stored in the lens microcomputer 5 at A8.

The relationship when the response time changes is that, for example, when the temperature rises and the magnetic force of the magnet decays, the response time becomes slow. Therefore, as shown in FIG.
For the iris drive signal, the response time shifts entirely above the reference value. Conversely, when the temperature drops, the response time becomes faster. That is, with respect to the iris drive signal, the response time shifts entirely below the reference value. Therefore, if only a certain point is set for the drive signal for opening and closing, the overall response speed will be made uniform. This determines the coefficient.

Next, FIG. 4 shows a flow chart when the exposure control is performed.

First, in the camera section, in S1, the camera microcomputer outputs the light amount difference to the lens microcomputer and at the same time inputs the aperture value from the lens microcomputer. Next, in S2, the light amount difference is calculated. The result is stored in the register transmitted to the lens microcomputer in S3.

Next, in the lens section, the aperture value is output to the camera microcomputer in S4, and at the same time, the light amount difference is input. Then, in S5, the aperture amount is calculated using the light amount difference and the coefficient stored when the power is turned on. Next, the aperture amount is output to the driver in S6, and the aperture value is input from the iris encoder in S7. Finally, in step S8, the aperture value is stored in the register sent to the camera microcomputer.

Further, S5 for calculating the aperture amount is shown in the flowchart of FIG.

At B1, a table of aperture values is selected from aperture values. At B2, the aperture amount corresponding to the light amount difference is selected from the aperture amount table. Finally, multiply the aperture amount by a coefficient at B3,
Correct the aperture value.

[Other Embodiments] FIG. 6 shows another embodiment.
The coefficient for correcting the drive signal of the iris is not limited to being obtained when the power is turned on. For example, if the recording or energizing time is long, the drive circuit itself also generates heat. Therefore, the temperature condition may change. As a result, the response time of the iris may change. Therefore, the timing for calculating the correction coefficient of the iris drive signal shown in FIG.
This flowchart is shown in FIG. After the power is turned on at C1, the coefficient is calculated at C2. In C3, normal exposure control using the coefficient obtained in C2 is performed. It is judged at C4 whether or not recording is in progress. If recording is not in progress, the process returns to C3 to perform exposure control. If recording is in progress, exposure control is performed in C5 using the coefficient obtained in C2, and it is determined in C6 whether recording has ended. If recording is in progress, exposure control is performed using the coefficient obtained in C2. If recording is finished, press C2 again.
In step 1, the coefficient is calculated, and thereafter, the exposure is controlled using the recalculated coefficient. By operating in this way, the exposure control can be corrected as accurately as possible without turning off the power.

[0022]

By measuring the response time of the iris and correcting the iris drive signal, the influence of the temperature on the response time of the iris can be removed, and the mechanical load difference can be removed.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a lens interchangeable video camera equipped with an exposure control device according to the present invention.

2 is a flowchart showing a part of a control operation of a microcomputer in the interchangeable lens of the video camera shown in FIG. 1 and main functions of the exposure control apparatus of the present invention.

FIG. 3 is a diagram showing driving characteristics of diaphragm blades used in the exposure control device of the present invention.

4 is a flowchart showing the exposure control operation of each of the microcomputer in the camera body and the microcomputer in the interchangeable lens of the video camera shown in FIG.

FIG. 5 is a flowchart showing an aperture blade control operation in the exposure control device of the present invention.

FIG. 6 is a flowchart of exposure control operation in another embodiment of a video camera equipped with the exposure control device of the present invention.

[Explanation of symbols]

1 ... Lens 2 ... Video camera main body 3 ... Mount section 4 ... Communication transmission line 5 ... Lens microcomputer 6 ... Camera microcomputer 7 ... Driver 8 ... IG meter 9 ... Aperture blade 10 ... Encoder 11 ... Afocal lens 12 ... Imaging element 13 ... Camera signal processing circuit 14 ... Integral detection circuit

Claims (1)

[Claims] 1. An exposure control device comprising a light amount adjusting member such as a diaphragm blade, a drive source for driving the light amount adjusting member, and a control means for controlling the drive source, wherein the control device comprises the light amount adjusting member. Based on the storage means for storing the response time of the member at the reference temperature, and the difference between the response time of the light amount adjusting member at any time and the response time at the reference temperature stored in the storage means. And a correction coefficient calculation means for calculating a correction coefficient of the control signal for the drive source.