JPH03252279A - Automatic contrast enhancing circuit - Google Patents

Abstract

PURPOSE:To increase the contrast variation in a picture to make the picture easy to see by converting a maximum or larger value or a minimum or smaller value of contrast detected by an extreme value detecting circuit to maximum or zero contrast of a device. CONSTITUTION:A console 1 is operated to designate coordinates of a part to be subjected to contrast enhancement in the picture. They are read by a CPU 2 and are inputted to a signal generating circuit 3 and are converted to a turning-on/off signal of a TV system, and this signal is inputted to an extreme value detecting circuit 4. The circuit 4 detects maximum and minimum values of contrast from picture data and supplies them to the CPU, and the processing result is supplied to an enhancing circuit 7. The circuit 7 converts the detected contrast to the maximum contrast of the device or zero contrast when the detected contrast exceeds the maximum contrast or is lower than the minimum contrast.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an auto contrast enhancement circuit that enlarges the maximum contrast value of a captured image within a predetermined range to make the screen easier to view.

[Prior Art] Generally, when an object is photographed under poor lighting conditions, the resulting image has low contrast and is difficult to see. In this case, if it is difficult to identify a subject on the screen, the contrast is manually adjusted so that the contrast of the part to be identified becomes stronger.

[Problems to be Solved by the Invention] However, the contrast characteristics of such a conventional device are as shown in the solid line shown in FIG. 4, where the horizontal axis represents the contrast of the input signal and the vertical axis represents the contrast of the display surface. Now, the lighting conditions are bad, and the part with the highest contrast is the symbol "
If the contrast is emphasized, it will look like the dash-dotted line in the figure. Here, if the part of the subject that you want to observe is within the range of the symbol [mouth J] in the figure, there is a problem that the overall contrast will only move in a state close to parallel movement, and the screen will not be easy to see.

[Means for Solving the Problems] In order to solve such problems, the present invention detects the maximum and minimum contrast values within an area specified by a range specifying means for specifying a search range on a display screen. This device includes an extreme value detection circuit and an enhancement circuit that adjusts the contrast of the entire screen to vary within the range of the maximum and minimum values detected by the extreme value detection circuit.

[Operation j: A detection range is specified, and the maximum and minimum contrast values in that range are detected. And of the screen contrast,
Contrast above the maximum detected value is converted to the maximum contrast of the device, and contrast below the minimum detected value is converted to zero contrast for the device. As a result, the contrast of the entire screen changes between zero and the maximum contrast of the device, and the amount of change in contrast within the screen increases, resulting in a screen that is easy to view.

[Example] FIG. 1 is a block diagram showing one embodiment of the present invention.

First, as shown in Figure 2, 5EII (Xl, Yl)) of the part of the screen where you want to perform contrast enhancement,
(X2.Y2) is specified by operating a predetermined part of the console 1. As a result, the specified coordinate data is read by the CPU 2 and supplied to the television system area signal generation circuit 3, where it is converted into a television system on/off signal.
The signal is supplied to the extreme value detection circuit 4. Further, a signal indicating the frame of the hatched portion in FIG. 2 is written into the overlay memory 5.

The extreme value detection circuit 4 is supplied with image data, and detects the maximum and minimum contrast values within a specified range. In this case, as shown in Figure 2, even if there is a very bright area outside the internal frame, such as a matte finish, this device will ignore that area, so the contrast processing result will be outside the area of interest. is not influenced by contrast information.

The detection result is supplied to the CPU 2 via the CPU boat 6, and the processing result processed there is supplied to the enhancement circuit 7. If the input contrast at this time is as shown by the thin line in Figure 3, and the maximum contrast detected by the extreme value detection circuit is 01 and the minimum contrast is C2, then all contrasts stronger than the maximum contrast (CI) are detected by the device. Converted to maximum contrast CL. Further, all contrasts weaker than the minimum contrast C2 are converted to contrast zero. That is, as shown by the thick line in FIG. 3, the maximum contrast of the designated area becomes the maximum contrast of the device, and the minimum contrast becomes zero contrast.

Since this processing is applied to the entire screen, the contrast of the entire screen will be distributed between zero contrast and the maximum contrast of the device. Therefore, if this correction is not performed, the contrast difference in the range of interest is expanded from the range of symbol "A" in FIG. 3 to the range of symbol "mouth", resulting in an easy-to-read screen. In this case, by changing the designated range in FIG. 2, the maximum and minimum contrast values for any area can be obtained. Therefore, the thick line slope in Figure 3 can be changed depending on the maximum and minimum contrast values within the specified range in Figure 2, and the specified range in Figure 2 can be set to provide the most legible contrast. .

The signal processed by the enhancement circuit 7 is converted into an analog signal by a D/A converter 8 together with the output of the overlay memory 5, and is displayed on a monitor 9.

Therefore, a frame is displayed on the screen as shown in FIG. 2 by the signal output from the overlay memory, and it can be seen at a glance that the area within the frame is the designated area.

[Effects of the Invention] As explained above, the present invention expands the amount of change in contrast of the entire screen based on information in an arbitrary range of input/output contrast characteristics. Even if the contrast is weak, it can be converted to a contrast that is easy to see, so it has the effect of making the screen easy to see.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a leap line showing the range specification state on the screen, Fig. 3 is a graph explaining the contrast conversion state, and Fig. 4 is a block diagram showing an embodiment of the present invention. The figure is a graph showing a conventional contrast change state. 1-...Operation console, 2--CPU, 3--TV area signal creation circuit, 4--Extreme value detection circuit, 6--CPU board, 7--・Enhancement circuit.

Claims (1)

[Claims] A range specifying means for specifying a search range on a display screen, an extreme value detection circuit for detecting the maximum and minimum contrast values within the area specified by the range specifying means, and an extreme value detection circuit. An auto-contrast enhancement circuit comprising: an enhancement circuit that converts contrast greater than the detected maximum value to maximum contrast of the device, and converts contrast less than the minimum value to zero contrast of the device.