JP2599124B2 - Optical servo circuit of video camera - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical servo circuit of a video camera.

[Summary of the Invention]

The response characteristic of the drive circuit that drives the optical drive means in the lens unit depends on the presence or absence of a signal related to the drive position from the optical drive circuit of the lens unit that occurs at the connector terminal attached to the lens unit attached to the video camera. The optical system drive (iris control and zoom control) is performed when any lens unit is used.

[Conventional technology]

2. Description of the Related Art A video camera is provided with an auto iris circuit that detects an image level and controls an iris motor so that an average luminance of an image is substantially constant irrespective of the brightness of a shooting target. The iris mechanism is attached to the lens unit. When the lens unit is mounted on the camera, the iris motor and the auto iris circuit inside the camera are connected via a connector. Information on the iris position and the zoom position is also sent to the camera body via the connector, and displayed on a viewfinder or the like.

[Problems to be solved by the invention]

The response characteristics of the iris mechanism may differ for each type of lens unit. In other words, the iris mechanism differs depending on the difference in the lens diameter and the magnification, and the iris response characteristics of the same type of lens unit may change due to a design change between the old type and the new type. Also in the case of a zoom lens, the zoom speed may be different for each unit. Conventionally, every time a lens unit is replaced, it is necessary to change a constant of a servo system in the camera body.

In view of this problem, an object of the present invention is to automatically correct response characteristics and the like when a lens unit is converted.

[Means for solving the problem]

An optical system servo circuit of a video camera according to the present invention is a video camera in which a lens unit 1 including an optical system and an optical system drive unit for adjusting the optical system is made detachable. The control signal is supplied from the optical drive circuit in the camera body to the drive unit by being provided in the camera body to be attached and electrically connecting them in a united state, and from the optical drive unit of the lens unit. A connector for supplying a signal relating to the drive position to the camera body; and an optical drive circuit including an amplifier circuit for amplifying an input control signal and supplying a control signal to the optical drive means via the connector. From the optical drive means generated at a predetermined pin terminal of the connector on the camera body side. A discriminating means (sense amplifier 9) for discriminating the presence / absence of a signal relating to the drive position, and the feedback circuit 8 of the amplifier circuit in the optical system drive circuit are intermittently operated by the discrimination signal from the discriminating means, whereby Switching means for switching a response characteristic of a servo system including the optical system driving means to a first response characteristic and a second response characteristic, and a signal for deriving a signal relating to the driving position to a predetermined pin terminal of the connector. Determine whether it is a unit or a lens unit that is not derived,
The optical system drive means is driven with servo response characteristics according to the lens unit attached according to the result of the determination.

[Action]

Since the type of lens unit is determined by the presence or absence of a signal related to the drive position from the optical system drive means that occurs at a predetermined pin terminal of the connector, a special signal or data dedicated to lens determination or a pin terminal of the connector dedicated to determination is used. The type of lens can be determined with a simple configuration that is not used.
When the response characteristics of the optical system servo system composed of the optical system drive means in the unit and the corresponding optical system drive circuit in the camera body differ depending on the type of the lens unit to be exchanged, the optical system drive circuit is determined by the lens discrimination. Since the response characteristic of the optical system drive means is automatically corrected on the side, it is not necessary to change the constant of the optical servo system every time the lens unit is replaced.

〔Example〕

FIG. 1 shows an auto iris circuit of a video camera according to one embodiment of the present invention. The lens unit 1 includes a lens system 10,
An iris 11, an iris motor 12, a drive amplifier 13, and a connector 14 are provided. When the lens unit 1 is mounted on the camera body having the image pickup tube 2, the connector 14 and the internal circuit are connected.

The video output of the image pickup tube 2 is led to the camera process circuit via the preamplifier 3, and is also supplied to a peak detection circuit 4 (or an average value detection circuit). Here, the DC-converted video signal is supplied as an optical system control signal from the connector 14 to the drive amplifier 13 via the adder 5 and the amplifier 6 and compared with a reference value ref.
Is driven. By this auto iris loop, a bright object is controlled in a direction in which the iris is closed, and a dark object is controlled in a direction in which the iris is opened, so that the brightness of the screen is kept substantially constant.

The amplifier 6 of the auto iris circuit in the main body has a feedback resistor 7 and a feedback impedance 8 from the output to the input. The impedance 8 may be, for example, a high-pass circuit including a resistor R and capacitors C1 and C2 as shown in FIG. A switch SW, which is a response characteristic switching means, is provided in series with the impedance 8, and the response characteristic of the iris servo system is adjusted by turning on / off the switch. The switch SW is a sense amplifier 9 that receives a lens determination signal from the pin terminal 15 of the connector 14 of the lens unit 1.
Is controlled by

In the case of a lens system having a 12-pin connector, an iris position signal indicating a driving position of a driving system of +2 to 7 V is given to the pin terminal 15 of the connector 14, and this signal is transmitted from the pin terminal 15 to the inside of the main body. To the iris position display circuit. This iris position signal is detected by the sense amplifier 9 constituting a discriminating means for discriminating the type of the lens unit, and the switch SW is turned off by the output thereof. As a result, feedback due to the time constant is not applied to the amplifier 6, and normal response characteristics are given.

On the other hand, in the case of a lens system having a 6-pin connector,
The pin terminal 15 of the connector 14 is opened. Therefore, there is no output from the sense amplifier 9, and the switch SW is turned on.
Then, negative feedback is applied to the amplifier 6 via the impedance 8, the high-frequency gain of the servo system is reduced, and hunting of the iris inherent to this lens system is prevented.

〔The invention's effect〕

As described above, according to the present invention, even if the response characteristics of the optical system servo system including the optical system drive means in the unit and the corresponding optical system drive circuit in the camera body are different depending on the type of the lens unit to be replaced, the connector The type of lens unit is determined based on the presence or absence of a signal related to the drive position from the optical system drive means that occurs at a predetermined pin terminal of the lens, so a special signal or data dedicated to lens determination or a pin terminal of a connector dedicated to determination is used With a simple configuration, the response characteristic of the optical system drive means can be automatically corrected on the optical system drive circuit side, eliminating the need for complicated work of changing the constant of the optical servo system every time the lens unit is replaced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an auto iris circuit of a video camera to which the present invention is applied, and FIG. 2 is a circuit diagram of the feedback impedance of FIG. DESCRIPTION OF SYMBOLS 1 ... Lens unit 2 ... Image pickup tube 4 ... Peak detection circuit 6 ... Amplifier 8 ... Feedback impedance 9 ... Sense amplifier 10 ... Lens system 11 ... Iris 12 ... Iris motor 13 ... Drive amplifier 14 … Connector 15 Pin terminals.

Claims (1)

(57) [Claims] 1. A video camera in which a lens unit including an optical system and an optical system drive means for adjusting the optical system is detachable, provided in the lens unit and a camera body to which the lens unit is attached, respectively. By electrically connecting the two in the combined state, a control signal is supplied from the optical system drive circuit in the camera body to the drive unit, and a signal relating to the drive position of the lens unit is transmitted from the optical system drive unit to the camera body. To the optical system drive circuit including an amplifier circuit for amplifying an input control signal and supplying a control signal to the optical system drive means via the connector; and a predetermined pin of the connector on the camera body side. The presence / absence of a signal relating to the drive position from the optical drive means generated at the terminal is determined. Determining the response characteristics of the servo system including the optical system drive circuit and the optical system drive unit by interrupting a feedback circuit of the amplifier circuit in the optical system drive circuit based on the determination signal from the determination unit. Switching means for switching between the first response characteristic and the second response characteristic, and discriminating between a lens unit that derives a signal relating to the drive position and a lens unit that does not derive the signal at the predetermined pin terminal of the connector, and a result of the discrimination An optical system servo circuit for a video camera, wherein said optical system drive means is driven with a servo response characteristic corresponding to a lens unit attached by the camera.