JPS6386993A - Detection signal for peak value of video signal - Google Patents

Abstract

PURPOSE:To speedily detect a peak at high accuracy without using a large memory by providing an A/D converter connected to a video camera, a horizontal counter, a vertical counter, latch circuits connected to the both counters, and a comparator. CONSTITUTION:The A/D converter 2 converts a video signal from the video camera 1 into a digital signal, which is inputted to the latch 3 and the terminal A of the comparator 4. The horizontal and vertical counters 5 and 7 detect the current horizontal and vertical positions and output them to the latches 6 and 8. The comparator 4 compares the output of the A/D converter 2 with the a video signal fetched to the latch 3 as the peak value of a previous video signal. If the former is larger than the latter, the comparator 4 simultaneously outputs a fetch signal to the latches 3, 6 and 8. Thus they fetch the video signal from the converter 2 and the current horizontal and vertical positions. This action continues for one frame, whereby the peak of one screen is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a video signal peak detection circuit used in object shape recognition devices, contour detection devices, and the like.

(Prior art) Conventional video signal peak detection circuits include: ■ Processing the video signal as an analog signal using a peak follower etc. and detecting its maximum illumination value; Some devices search for the position and value of maximum illuminance after converting and storing it in memory.

However, in the former ■, when detecting the position of maximum illuminance, the time,
Problems arise with accuracy, etc. In addition, the latter (3) has the disadvantage that the memory becomes large and the search takes time.

(Objective) It is an object of the present invention to provide a video signal peak detection circuit that eliminates the above-mentioned drawbacks and can perform peak detection of a video signal at high speed and with high accuracy without requiring a large memory.

(Configuration) The present invention includes an analog/digital converter, a comparator, a horizontal position counter, a vertical position counter, and a latch,
The video signal is converted from analog to digital by an analog/digital converter and compared with the signal previously captured in the latch by a comparator.

The horizontal position counter detects the screen horizontal position of the video signal by counting the number of clocks synchronized with the video signal, and the vertical position counter detects the screen horizontal position of the video signal by counting the number of horizontal synchronization signals of the video signal. Detect. The latch receives the outputs of the analog/digital converter, horizontal position counter, and vertical position counter using the output signal of the comparator.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the invention.

The analog video signal Vi from the video camera device t
eo, a sampling clock CLK synchronized with this video signal, a horizontal scanning synchronization signal +1D, and a frame signal FLM representing one screen are transmitted. The video signal Video from the video camera device 1 is analog/digital (A/D
) Converter 2 I converts it into digital data with the required precision and inputs it to the latch 3 and the A terminal of the comparator 49.Meanwhile, in the horizontal position, the counter 5 counts the sampling clock CLK from the video camera device 1. It is reset by the horizontal scanning synchronization signal +10 from the video camera device 1, and constantly detects the current horizontal position and outputs it to the latch 6. Also, the vertical position counter 7 is equipped with a video camera [
The horizontal scanning synchronizing signal HD from 1 is counted, and the current vertical position is always detected and output to the latch 8. Here, the comparator 4 compares the digital video signal input from the A/D converter 2 to the A terminal and the video signal that has been taken into the latch 3 as the peak value of the previous video signal and input to the B terminal. However, when the input signal at the A terminal is larger than the input signal at the B terminal, the signals No. 43 are simultaneously output to the latches 3 and 6.8. At this time, the latches 3 and 6.8 are connected to the video signal from the A/D converter 2, the current horizontal position detected by the horizontal position counter 5, and the current value detected by the vertical position counter 7 according to the input signal from the comparator 4. By continuing this operation over one frame, the peak (the position showing the maximum illuminance and the value of the maximum illuminance) in one screen is detected. The control circuit 9 synchronizes the video camera device 1 with external command signals, controls the data bus 10, etc.

FIG. 2 shows a portion of another embodiment of the invention.

In this embodiment, the threshold value is set in the above embodiment, and the output signal of the A/D converter 2 is compared with the threshold value. The AND gate 12 ANDs the output signal of the comparator 4 and the output signal of the threshold circuit 11. (2) When a new capture signal is not output for a frame, or when it is output several times, the control circuit 9 detects this from the output signal of the AND gate 12 and outputs a signal to the outside to shorten the processing time.

FIG. 3 shows a portion of another embodiment of the invention.

In this embodiment, a circuit is added to the above embodiment to clamp the video signal Video from the video camera device 1 at zero potential before A/D conversion by the A/D converter 2 to improve accuracy. The additional circuitry consists of a barrier amplifier +3.14, a switching element 15 and a capacitor 16 of a suitable capacity.

Ordinary video signals are often output through AC coupling as shown in FIG. 4(A), and the peak value PK changes depending on the overall shape in one horizontal scanning section. Therefore, by using the horizontal scanning synchronization signal HD shown in FIG. 4(B) and clamping the video signal only in that section as shown in FIG. 4(C), the peak value can be detected with high accuracy.

In this embodiment, the video signal from the video camera device 1 is input to the A/D converter 2 via the buffer amplifier 13, the capacitor 6, and the buffer amplifier 14. When the switching element 15 is turned on, it is clamped to zero potential.

Contour detection, area search, moving (stationary) object detection, etc., which are currently performed in image processing, can be performed at high speed by applying the present invention.

(Effects) As described above, according to the present invention, the peak of the video signal is detected in real time and digitally, so the peak of the video signal can be detected at high speed and with high precision.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIGS. 2 and 3 are block diagrams showing parts of other embodiments of the present invention, and FIG. 4 is a timing diagram of the embodiment shown in FIG. It is a chart. 2... A/D converter, 3, 6.8... latch,
4...Comparator, 5...Horizontal position counter, 7...Vertical position counter. Figure 1/vFJZ diagram δ

Claims (1)

[Claims] A circuit that detects peaks between one frame of a video signal includes an analog/digital converter that converts the video signal from analog to digital, and a comparator that compares the output signal of the analog/digital converter with the previously captured signal. , a horizontal position counter that detects the screen horizontal position of the video signal by counting the number of clocks synchronized with the video signal, and a vertical position counter that detects the screen vertical position of the video signal by counting the number of horizontal synchronization signals of the video signal. A video signal peak detection circuit comprising: a position counter; and a latch that receives the outputs of the analog/digital converter, the horizontal position counter, and the vertical position counter based on the output signal of the comparator.