JPH02257126A - Image pickup device - Google Patents

Abstract

PURPOSE:To obtain iris operation at the most suitable response speed in any diaphragm changing directions by providing a control means for actually correcting the response speed of each displacing operation which displaces a lens diaphragm member of an optical system and providing a displacement driving means for the diaphragm member. CONSTITUTION:Only the clamped image pickup signals of a photometric part on a screen are extracted at a gate circuit 8 and the extracted signals are supplied to an integrating circuit 12. At the integrating circuit 12, the image pickup signals are integrated into the signals close to direct current signals to make them even and are supplied to a non-linear amplifying circuit 10 as the response speed correction control means through an amplifying circuit 11. At the circuit 10, when the diaphragm 2 changes from release to slight stop- down, and conversely, when it changes from the slight stop-down to the release, the signals which are corrected to have the correct response speed are generated, and a diaphragm mechanism 2a is controlled through the iris driving circuit 9. Thus, the diaphragm operation response speed of the auto-iris system for image pickup devices such as a video camera is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an auto-iris system for an imaging device, particularly a video camera.

[Conventional technology]

In the conventional auto-iris system of this type of video camera, the aperture (iris aperture) changes from wide open to small aperture depending on the brightness of the subject, or conversely from small aperture to wide open. So, in terms of circuit configuration,
They were designed to provide the same gain.

[Problem to be solved by the invention]

However, with such conventional methods, when the subject changes from dark to strong light, for example,
In an auto iris system, when the aperture 2 changes from wide open to a small aperture, the above auto iris loop cane appears, but conversely, when the subject changes from strong light to dark, in other words, in the auto iris system, the aperture 2 is higher than the apparent auto iris loop gain when changing from a small aperture to a wide open state.
The operation response speed when the aperture 2 changes from wide open to small aperture in the former case is different from the operational response speed when the aperture 2 changes from small aperture to wide open in the latter case.

For this reason, if the gain of the circuit is determined to suppress the hunting of the iris when the aperture changes from wide open to a small aperture, the response speed when changing from a small aperture to a small aperture will be extremely slow. There was a problem that the auto iris operation could become slow and unnatural.

The present invention has been made in order to solve the problems of the conventional example described above, and it is an object of the present invention to realize an auto iris system of this type that can obtain an iris operation with an optimal response speed in any direction of change of the aperture. It is an object.

[Means to solve the problem]

Therefore, the auto iris system of the imaging device according to the present invention includes a control means for substantially optimizing the response speed of each displacement operation, regardless of the state in which the aperture member of the lens of the optical system is displaced; The above object is achieved by providing a displacement drive means for the aperture member.

[Effect]

With the configuration of the auto iris system as described above, in the imaging apparatus according to the present invention, a substantially optimal response speed of the aperture operation can be obtained even in response to various changes in the brightness of the subject.

〔Example〕

FIG. 1 shows a block diagram of an embodiment of a video camera having an auto-iris circuit according to the present invention.

(Configuration/Operation) A light image from a subject is formed on an image sensor 3 via an optical system lens 1 and an aperture 2. Depending on this imaging state, an imaging signal is supplied from the imaging element 3 to a sample hold (S/H) circuit 4, where it becomes a sampled and held imaging signal. The imaging signal output from the S/H circuit 4 is supplied to the signal processing circuit 5, where the luminance signal Y and color signal C are extracted as video signals. It is output from the camera section in the form of a signal or the like.

On the other hand, the imaging signal output from the 378 circuit 4 is clamped by a clamp circuit 7, and is used as an aperture control signal for controlling the aperture 2 to obtain appropriate exposure according to the screen brightness state. That is, the gate circuit 8 extracts only the photometric portion of the screen from the clamped imaging signal and supplies the extracted image signal to the integration circuit 12 . This integrating circuit 12 integrates and smoothes the imaging signal into a signal close to a DC signal, and supplies the signal via an amplifier circuit 11 to a nonlinear amplifier circuit 10 as a response speed optimization control means according to the present invention. , even when changing from aperture to a small aperture, or conversely from a small aperture to an aperture, a signal corrected to have an appropriate response speed is generated, and the signal is sent via the iris drive circuit 9. This is to control the aperture mechanism 2a.

FIG. 2 shows a specific circuit example of the non-linear amplifier circuit 10 of the present invention, and FIG. 3 shows a linear amplifier circuit diagram corresponding to this part of a conventional example in comparison. According to the present invention, when a Schottky or diode or other semiconductor device D1 and a resistor R2 are connected in series and connected in parallel between both ends of the resistor R1 in FIG. 3 to form the structure shown in FIG. When the voltage of the human power integral signal (point A) from the input signal (point A) becomes lower than that of the inverting terminal (point B) of the operational amplifier OP, the semiconductor element D1
becomes conductive, and the gain of the inverting amplifier OP is amplified.

FIG. 4 shows gain characteristic diagrams (output level/human power level ratio) 14 and 13 of the conventional inverting amplifier and the nonlinear inverting amplifier 13 of the present invention, respectively. That is, by configuring the amplifier gain to have a non-linear characteristic as shown in 13 instead of having the linear characteristic 14 as in the conventional configuration shown in FIG. It becomes possible to achieve a substantially appropriate response speed.

(Other Embodiments) Next, FIG. 5 shows a diagram corresponding to FIG. 1 of the second embodiment of the present invention, which is the same as that in FIG. 1 of the first embodiment.
Components are represented by the same reference numerals.

In this embodiment, as the response speed optimization control means, the first
In place of the nonlinear amplifier circuit 10 of the first embodiment shown in the figure,
A predetermined correction signal is output by a microcomputer 19 (hereinafter abbreviated as "microcomputer") using an aperture value (opening degree) detection means (for example, a Hall element 15).

That is, as in the first embodiment, the image signal output from the image sensor 3 is smoothed by the integrating circuit 12, and then smoothed by the amplifier circuit 1.
1 and then output. The output signal is sent to the A/D circuit 21
The analog value is converted to a digital value, and the microcomputer 19
is man-powered.

On the other hand, the opening state of the diaphragm 2 is detected by the Hall element 15, and the aperture state is detected by the Hall element 15.
Power is applied to circuit 17. Here, the analog value is converted into a digital value and manually inputted to the microcomputer 19. Further, the reference voltage V raf is also converted from an analog value to a digital value by the A/D circuit 20, and is input to the microcomputer 19, where it is subjected to predetermined correction.

The operation of the microcomputer 19 will be explained based on the sequence flowchart shown in FIG.

First, in steps S1 and 82, the digital value Y of the imaging signal output from the A/D circuit 21 and the digital value R of the reference voltage V ref output from the A/D circuit 20 are calculated.
ef, and in step S3 both digital values Y and R are acquired.
Find the difference signal of ef and set it as Y. Similarly, in step S4, the digital value H of the Hall element voltage output from the A/D circuit 17 is taken in.

Next, in step S5, this digital signal compares H with the previously captured Hbefore and determines that Hbefore<
When H, gain table B, which will be described later, is set in step S6.
is selected, and when Hbafore≧H, Kane table A is selected in step S7. These gain tables A and B are shown in Table 1. Predetermined correction values according to the output value of the Hall element, that is, the aperture value, are stored in advance, and the correction values of the gain tables are used as described above. The difference signal Y is multiplied by Y, and drive data Dr is output in step S8. At this time, in order to make the response speed from the aperture to the small aperture and the response speed from the small aperture to the aperture substantially appropriate, the gain table A is set in the gain table A or Table 1. Gain table B is a gain table when responding from wide open to small aperture. Eliminates hunting due to small aperture,
In order to achieve an optimal response speed, the gain is lowered in the small aperture region of gain table B than in the small aperture region of gain table A for correction.

In this embodiment shown in Table 1, the F value is divided into eight stages, but it is also possible to determine and correct the gain in any appropriate stage.

Next, the output signal Dr corrected as described above is processed in step S
9, the digital value is converted into an analog value by the D/A circuit 18 in FIG.
drive to an appropriate response speed.

As described above, since the optimum response speed can be corrected, it is possible to sufficiently absorb variations in IG meters and the like.

(Effects of the Invention) As described above, according to the present invention, it is possible to optimize the response speed of the aperture operation in the auto-iris system of an imaging device such as a video camera using a simple circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a configuration of an embodiment of a video camera according to the present invention, FIG. 2 is a specific example of the nonlinear amplifier circuit shown in FIG. 1, FIG. 3 is an example of a conventional linear amplifier circuit, and FIG. 3/4 is a comparison diagram of each gain characteristic of the circuit, FIG. 5 is a circuit configuration block diagram of another embodiment, and FIG. 6 is an operation sequence flowchart of the microcomputer shown in FIG. 5. 1...Optical system lens 2...Aperture 2a...Aperture mechanism 3---Image sensor 9---Iris drive circuit

Claims (3)

[Claims] (1) In an auto iris system of an imaging device, a smoothing means for converting a video signal into a DC signal, a control means for optimizing the response speed of each displacement operation of an aperture member of an optical system lens, and the aperture An imaging device comprising: a drive means for displacing a member. (2) The imaging apparatus according to claim 1, wherein the control means for optimizing the response speed comprises a nonlinear amplification means using a semiconductor element. (3) The control means for optimizing the response speed includes a detection means for detecting the opening degree of the aperture member, and a correction means for making a predetermined correction according to the output of the detection means. The imaging device according to claim 1, characterized in that: