KR0112822Y1 - Apparatus for controlling sensitivity of video camera - Google Patents

Abstract

None.

Description

Automatic sensitivity control of video camera

1 is a detailed circuit diagram of the present invention.

2 is a conventional technical configuration.

* Explanation of symbols for main parts of the drawings

1: gamma correction circuit, 2: automatic gain control circuit (AGC),

3: high frequency gamma (YH) correction circuit 4: automatic sensitivity control circuit,

R ₁ -R ₆ : resistor, Q ₁ : transistor

C ₁ -C ₃ : Capacitor, VR ₁ : Variable resistor.

The present invention relates to an automatic sensitivity control device of a video camera, and to an automatic sensitivity control device of a video camera that is suitable for maintaining a constant image output when the illuminance of a subject to be captured by the video camera is low (less than 10 lux). It is about.

Conventionally, as shown in FIG. 2, the gamma correction circuit 1 and the automatic gain control circuit 2 for determining the sensitivity of the video camera are connected to each other, and the characteristics of the gamma amplifier are improved. In order to maintain the maximum sensitivity by increasing the gain, a gain control switch SW ₁ that applies a reference voltage Vref or makes the gain on state to increase the gain at low illumination to the gamma control of the correction gamma circuit ₁ is provided. The connection is made up. When the gain control switch SW ₁ is shorted to the normal contact to adjust the sensitivity of the video camera, the circuit maintains a constant gain by applying the control voltage of the reference voltage Vref to the gamma control level. When (SW ₁ ) gain reaches the contact, the gamma control voltage becomes 0 volts, which is the maximum of the gamma amplifier.

Conventionally, since the gain control switch SW ₁ is not used to adjust the sensitivity of the video camera, it is not possible to easily determine the change in illuminance in a low illuminance state (illuminance of 10 lux or less). It can not be determined what to switch at any point to gain the ground located on the gain a (SW ₁₎ state case of using the gain of the gain control switch (SW ₁₎ in the general illumination (over 100 Lux illumination) are turned on the captured The video signal is saturated, resulting in deterioration of color reproducibility and sharpness of the subject.

The present invention has been made in order to correct the security of the conventional problems will be described in detail with reference to the accompanying drawings as follows.

As shown in FIG. 1, the automatic sensitivity control circuit 4 detects an image signal of a photographed subject that adjusts a gain of a gamma amplifier, and converts a DC signal converted into an op amp OP ₁ and a transistor Q _1. ) And peripheral devices to automatically adjust the gamma control voltage so that the gain control switch SW _{1 of} FIG. The effect of the circuit configured as described above is as follows. The captured image signal is passed through the gamma amplifier, and the average signal represented by direct current (DC) voltage through the automatic gain control circuit (2) and the automatic gain control detector (AGC-DET). The control voltage is used to determine the characteristics and gain of the primary gamma amplifier by the reference voltage (Vref) and to use the signal output through the automatic gain control detector (AGC-DET) to automatically adjust the gain. Although there is a slight difference depending on the signal processing system, a detection output of about 0.5 volts is obtained in the cap state of the camera lens and about 1.3 volts at high illuminance (about 500 lux or more). The detected voltage is divided by the resistors R ₁ and R ₂ , and the divided voltage is applied to the inverting (-) terminal of the op amp OP ₁ through the resistor R ₃ and the resistor R ₃ ), (R ₄ ) is the op amp (OP ₁ ) gain is determined and the output of the op amp (OP ₁ ) is the voltage applied to the base of the transistor (Q ₁ ) by the variable resistor (VR ₁ ). Adjust

The transistor (Q _1), the voltage being applied to the base when the illuminance of the subject to image capture is low (the signal of 20 lux or less) is set the base voltage of the transistor (Q ₁₎ so that it can be automatically adjust the gain of the gamma amplifier The voltage of the transistor Q ₁ is changed from the reference voltage Vref to the ground potential, and the gain of the gamma amplifier is adjusted to maintain the luminance signal at a constant pevel even for a low light (10 tex or less) signal. Therefore, the sensitivity of the video camera is adjusted automatically.

The present invention uses the automatic sensitivity control circuit (4) to automatically adjust the sensitivity of the video camera in situations where it is difficult to determine the illuminance of the subject, that is, difficult to detect low light conditions, the user is convenient and convenient to use. This is a phenomenon that occurs when the gain control switch (SW ₁ ) is used in the normal state, which is a technical problem of the video camera. It is designed to be convenient for users.

Claims (1)

Gamma correction means for correcting and outputting the gamma according to the luminance of the clipped image signal according to an external control signal, and automatically controlling the gain of the output image signal with gamma correction by the gamma correction means and detecting a gain level. An automatic gain control means for feeding back to the gamma correction means and outputting to the rear stage, an amplifier for inverting and amplifying a gain level obtained by the automatic gain control means, a variable resistor for variably adjusting the voltage output from the amplifier; And a gamma control voltage generating means composed of a transistor which is switched by a variable variable controlled by the variable resistor to output a gamma control voltage of a predetermined level or not to be output. Device.