JPS607592Y2 - Video contour extraction circuit - Google Patents

Description

[Detailed description of the invention] This invention relates to an image processing circuit that uses video signals obtained from a television camera.The purpose of this invention is to extract only the outline of either the leading edge or the trailing edge of the image from the video signal for each horizontal scanning line in real time. The purpose of this invention is to provide a new contour extraction circuit that extracts contours using

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a first embodiment of the invention.

In FIG. 1, a television camera 11 obtains a video signal from a subject.

This video signal is passed through a low pass filter 12 having a cutoff frequency of about 3 MHz.

This low-pass filter 12 is for preventing aliasing errors that occur during sampling processing.

In this example, the sampling frequency is 5 MHz (horizontal resolution 200 nsec).

The video signal that has passed through the low-pass filter 12 becomes as shown in FIG. 2A.

This video signal is input to the pedestal clamp circuit 13.

This pedestal clamp circuit clamps the video signal below the pedestal portion, as shown in FIG. 2B.

This is to prevent the synchronization signal and pedestal from changing depending on the brightness of the subject in preparation for later video signal processing.

The video signal output from the pedestal clamp circuit 13 (
(shown in FIG. 2B) passes through the video amplifier 14, and further,
The signal is level-adjusted by a variable resistor 15 and then input to a differential video amplifier 16 .

The output of the video amplifier 14 is further, for example, 500rI.
The signal is input to the other input terminal of the differential video amplifier 16 via a delay line 17 having a delay time of SeC.

The delay time of this delay line 17 determines the horizontal resolution together with the sampling period.

The two outputs of the differential video amplifier 16 are a rising differential signal and a falling differential signal of the video signal, respectively.

Both differential signals pass through a changeover switch 18, and one of them is input to one input terminal of a comparator 19.

A predetermined reference voltage V3 obtained by a variable resistor 20 is input to the other input terminal of the comparator 19.

A differential signal greater than this reference voltage V3 is output from the comparator 19 and sent to the television monitor 21 and recording device 22.

Next, the operation will be explained in more detail.

Assume now that the output of the video amplifier 14 is as shown in FIG. 3A.

Then, the video signal that has passed through the delay line 17 is delayed by a predetermined time as shown by the opening in FIG.

The differential video amplifier 16 compares both input signals and produces an output only when there is a difference.

In this way, the differential signal of the rising portion of the video signal is generated at one output terminal, and the differential signal 2 of the falling portion of the video signal is generated from the other output terminal.

This signal for the same machine is set to one of the two by the changeover switch 18, inputted to the comparator 19, and the reference voltage V3 is input to the comparator 19.
A signal is detected only when the value exceeds , and thus two contour signals as shown in FIG.

For example, suppose that the television camera 11 photographs an object having a black and white pattern as shown in FIG. 5A.

Then, since the video signal changes rapidly at the boundary between the white pattern and the black pattern, a contour signal is obtained at the intersection of this boundary and the horizontal scanning line.

In the case shown in FIG. 5A, a sudden change in the video signal appears in the three scanning lines (n+1) to (n+3), so the contour signal obtained by the extraction circuit in FIG. When expressed as , it becomes as shown in Fig. 5B.

That is, in FIG. 5B, contour signals are placed at the intersections of the boundaries of today's three scanning lines (n+1) to (n+3).

By the way, as is clear from FIGS. 5A and 5B, when the slope of the contour of the image approaches the horizontal scanning line, the contour signals become spaced apart and are not continuous. This is extremely difficult to see and is also inconvenient for later image processing.

A second embodiment shown in FIG. 4 improves this problem.

In Fig. 4, in addition to the circuit in Fig. 1, a new delay line 41 is added.
A differential video amplifier 42, a changeover switch 43, a comparator 44, a variable resistor 45, and a mixing circuit 46 are added.

The delay line 41 has a delay time corresponding to one horizontal scanning period.

When photographing a subject as shown in Figure 5A, n~(
The video signals generated in each scanning line up to n10 are as shown in FIG. 6A.

The video signal passing through the delay line 41 becomes the video signal on the previous horizontal scanning line.

Therefore, for example, the output from the differential video amplifier 42 on the (n+3) today's scanning line will occur if there is a difference from the video signal on the previous (n+2) today's scanning line, and as shown in FIG. It becomes as shown in .

That is, the differential video amplifier 42 provides a differential output of the video signal in the vertical direction.

The changeover switch 43 is for switching between rising differential and falling differential.

When this differential signal exceeds a predetermined reference voltage Vt set by variable resistor 45, an output is generated from comparator 44.

If this is displayed on the television monitor 21, a horizontally long contour signal will be displayed as shown in FIG. At the same time, the inconvenience caused when tracing the continuity of a nearly horizontal curved contour line is also eliminated.

As described above with respect to the embodiments, the video contour extraction circuit according to the present invention uses a delay circuit that delays a video signal, compares the original video signal and the delayed video signal, and compares the rising and falling portions of the video signal. a differentiating circuit that obtains differential signals having different polarities in different parts; a switching circuit that selectively switches and extracts the differential signal of the rising part and the differential signal of the falling part of the video signal; and the differential signal obtained from the switching circuit. It is characterized by having a comparison circuit that extracts those of which a certain value or more are included, and it is possible to perform contour detection by reducing the amount of information while leaving the position information of the contour signal, so that later information processing can be performed. This not only makes processing extremely easy, but above all, it enables real-time processing.

Further, since the configuration is simple and the device can be made compact, it can be easily installed in a machine tool or the like that requires a device that performs automatic positioning using contour detection signals, and it is also possible to reduce costs.

[Brief explanation of the drawing]

Figure 1 is a block diagram of one embodiment of the present invention, Figure 2A,
B is a waveform diagram showing the signal waveforms at points A and B in Figure 1;
FIG.
B and C are enlarged views, A is a diagram showing the relationship between the subject pattern and the horizontal scanning line, B is a diagram showing the contour signal displayed on the television monitor in Figure 1, and C is a diagram showing the outline signal shown in Figure 4. A diagram showing a contour signal displayed on a television monitor of
Figures 6A and 6B are waveform diagrams for explaining Figure 4.
5A is a waveform diagram showing signal waveforms generated in each of scanning lines n to (n+4) of the subject shown in FIG. 5A, and B is a waveform diagram showing differential outputs generated in today's scanning line (n+3). 11...Television camera, 12...
・Low pass filter, 13...Pedestal clamp circuit, 14...Video amplifier, 16.42
...Song differential hito amplifier, 17,41...Delay line, 18,43...Switch switch, 19.
44・Song・Comparator, 46...Mixing circuit,
21...Television monitor, 22...
・Recording device.

Claims (1)

[Scope of utility model registration request] a delay circuit that delays a video signal; a differentiation circuit that compares the original video signal with the delayed video signal and obtains differential signals having different polarities at the rising and falling portions of the video signal; An image characterized by having a switching circuit that selectively switches and extracts a differential signal and a differential signal of a falling portion, and a comparison circuit that extracts a differential signal of a certain value or more from among the differential signals obtained from the switching circuit. contour extraction circuit.