JPS6324763A - High luminance compressing circuit in color camera - Google Patents

Abstract

PURPOSE:To improve a dynamic range by providing a circuit to slice a video signal at a constant level, gain-controlling the upper part signal and mixing it to the lower part signal. CONSTITUTION:An input video signal to pass through a buffer amplifier 1 is divided up and down by an upper part slicing circuit 2 and a lower part slicing circuit 3. The signal of the upper part is gain-controlled by a gain control amplifier 4 and mixed with the lower part by a mixing amplifier 5. The mixed signal passes through a buffer amplifier 6, is peak-detected by a peak detecting circuit 7, converted to DC, a DC voltage value is reset by a buffer amplifier 8, sent to the gain control amplifier 4 and controls the gain. The DC for the gain control comes to be the output signal and a feeding-back loop, and even when the input signal level is changed, the peak value of the output level is kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high brightness compression circuit in a color camera.

Conventional technology Conventionally, this type of compression circuit compresses the signal by utilizing the forward voltage drop curve of the diode, and is capable of compressing an input of about 400% of the standard state. Met.

FIG. 2 shows its configuration, where 9 is a compression circuit and 10 is a reference voltage generation circuit.

Problems to be solved by the inventionHowever, if there is more than 100% input,
'With conventional circuits, the signal was distorted and the dynamic range of the camera was reduced.

The present invention solves these drawbacks, and aims to provide an excellent dynamic range even at high brightness.

Means for Solving the Problems In order to solve the above problems, the present invention provides a circuit that slices the video signal at a constant level, controls the gain of the upper signal, and mixes the signal into the lower signal. As a result, the output signal can be compressed to a constant level without any fluctuation in the peak point or compression point for input signals up to the input signal level of 800%.

Function: Therefore, even when the brightness is high, the signal is not distorted, which is advantageous for improving the dynamic range of the camera.

Example FIG. 1 shows the configuration of an embodiment of the present invention.

In FIG. 1, 1, 6.8 are buffer amplifiers, 2 is an upper slice circuit, 3 is a lower slice circuit, 4 is a gain control amplifier, 5 is a mix circuit, and 7 is a peak detection circuit. In this configuration, an input video signal that has passed through a buffer amplifier 1 is divided into upper and lower parts by an upper slice circuit 2 and a lower slice circuit 3. The divided upper part signal is sent to a gain control amplifier 4, gain controlled, and mixed with the lower part signal by a mix amplifier 5.

When the mixed signal is output, it passes through a buffer amplifier 6, a peak detection circuit 7 detects the peak, and this is further converted to DC and then a buffer amplifier 8 outputs a DC signal.
The C voltage value is reset and sent to the gain control amplifier 4 to control the gain. The DC for gain control has a feedback loop with the output signal, so that even if the input signal level changes, the peak value of the output level is kept constant.

As a result of experiments, compression of up to 800% of the standard signal level is possible.

In the case of a three-tube type or three-plate color camera, the above circuit is JG.
, H, respectively.

Effects of the Invention As explained above with reference to embodiments, according to the present invention, even when the input video signal level increases at high brightness, the signal does not collapse, and is effective in improving the dynamic range of a color camera. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a high-brightness compression circuit in a color camera according to an embodiment of the present invention, and FIG. 2 is a diagram of a conventional high-brightness compression circuit. This is a diagram. 1.6.8... Buffer amplifier, 2... Upper slice circuit, 3... Lower slice circuit, 4... Gain control amplifier, 5... Mix amplifier, 7... Peak detection circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (3)

[Claims] (1) Based on a circuit that separates a video signal input into those above and below a certain level, a mix circuit that mixes the separated signals, and a peak value of the video signal, A high-brightness compression circuit in a color camera that is equipped with an adjustment circuit that compresses separated video signal inputs above a certain level. (2) The adjustment circuit comprises a circuit that detects the peak of the output of the mix circuit, and a circuit that uses the peak detection output as a gain control signal and compresses the separated video signal of a certain level or higher. High brightness compression circuit in the color camera described. (3) A high-brightness compression circuit in a color camera according to claim 1, wherein the video signal separation circuit, mix circuit, and adjustment circuit are provided in each R, G, and B circuit.