JP3210758B2 - Display image contrast improvement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the contrast of a displayed image by enhancing peaks and valleys of a luminance distribution curve of an image taken by an image pickup means to improve the contrast of the image.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, an image picked up by an image pickup means 1 such as a CCD two-dimensional camera installed in a front part of a vehicle is provided near a driver's seat so as to assist safe driving when driving a car. Display is performed on a monitor television receiver (hereinafter, simply referred to as a monitor) 2 including an LCD or the like installed.

[0003] The circuit configuration of this type of visibility information providing apparatus is as shown in FIG. 4. An image of the front of the vehicle is taken by an image pickup means 1, and an image pickup signal outputted from the image pickup means 1 is analog. A / D conversion is performed by a digital / digital conversion (hereinafter referred to as A / D conversion) unit 3, and luminance data for each certain frame obtained by the A / D conversion is stored in a frame memory 4. It is processed by the image processing means 5.

[0004] At this time, especially when the vehicle is traveling in the fog at night, the visibility is extremely poor, and the contrast of the image captured by the image capturing means 1 becomes extremely poor.

The normalizing process is a process of enhancing peaks and valleys of the luminance distribution curve by changing the luminance levels of the maximum point and the minimum point of the luminance distribution curve on each horizontal line of the captured image. Thereby, the contrast of the captured image is improved.

[0006] Further, after the above-described normalization processing is performed by the image processing means 5, the processed data is converted to digital / digital data.
The analog / digital conversion (hereinafter referred to as D / A conversion) unit 6
The A-converted image is displayed on the screen of the monitor 2 with the contrast improved.

For example, when an image of a vehicle traveling ahead is imaged in fog and the obtained image is displayed as it is without normalization processing, the contrast is very poor as shown in FIG. The luminance distribution curve on each horizontal line has almost no change in peaks and valleys as shown in FIG. Here, the cross hatching in FIG. 5A represents fog.

However, when the image processing means 5 performs the normalization processing, the maximum point of the luminance distribution curve shown in FIG.
An image in which the luminance level of the minimum point is changed, peaks and valleys of the luminance distribution curve are enhanced as shown in FIG. 6B, and the contrast is improved to a state close to no fog as shown in FIG. 5B Is displayed.

[0009] Next, when there is a bright portion such as the irradiation area of the headlamp of the own vehicle in the captured image at night and in the fog, this image is displayed as it is without normalization processing as shown in FIG. Only bright portions are clearly displayed as described above, but when these portions are too bright and the output of the imaging means 1 is saturated, the luminance distribution curve on the horizontal line including these bright portions is shown in FIG. As shown in a), the saturated region becomes flat.

[0010]

However, even if the captured image during nighttime and in fog shown in FIG.
If there is a portion that is too bright to saturate the imaging signal, there is no normalization effect, and the luminance distribution curve after the normalization processing is normalized as shown in FIG. The image after the normalization processing is not much different from that before the processing, and FIG.
As shown in FIG. 7, the image becomes almost the same as before the normalization processing shown in FIG. 7A, and there is a disadvantage that the contrast cannot be improved.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above points, and it is an object of the present invention to improve the contrast by effective normalization, especially at night and in a fog. And

[0012]

According to the present invention, there is provided a method for improving the contrast of a displayed image, comprising: a monitor for receiving an image obtained by capturing an image of the front of the vehicle during nighttime fog by an image capturing means mounted on the vehicle; When the image is displayed on the image, the image processing unit changes the luminance level of each of the maximum point and the minimum point of the luminance distribution curve on each horizontal line of the image to enhance the peaks and valleys of the luminance distribution curve. This is a method of improving the contrast of a displayed image, which improves the contrast of an image, wherein the process of emphasizing the peaks and valleys of the luminance distribution curve is performed only in an area other than an irradiation area of a headlamp of the own vehicle in the image. It is characterized by:

[0013]

In the present invention, the illuminated area of the headlamp of the vehicle occupying in the captured image at night and in fog is known by checking the captured image in advance as long as the installation position of the imaging means is not changed unless the installation position is determined. Therefore, the effect of normalization can be obtained by performing processing of emphasizing the peaks and valleys of the luminance distribution curve only in the other region excluding the headlamp irradiation region of the own vehicle from the actually obtained captured image, The contrast can be improved.

[0014]

FIG. 1 is a diagram illustrating the operation of an embodiment of a method for improving the contrast of a displayed image according to the present invention, and FIG. 2 is a block diagram of a view information providing apparatus applied to FIG.

The configuration of the visibility information providing device will be described. Since it is basically the same as the conventional configuration shown in FIG.
In FIG. 2, the same reference numerals as those in FIG. 4 denote the same or corresponding components, and the difference from FIG. 4 is that the imaging means 1 is fixedly installed in the front part of the vehicle, so that the imaging means 1 is not changed unless the installation position is changed. Since the positional relationship between the means 1 and the headlamp of the own vehicle is constant, and the irradiation area of the headlamp occupied in the image picked up by the image pickup means 1 is constant, the position data of the irradiation area is checked in advance by checking the picked-up image. Can be derived, the derived position data of the irradiation area is previously input to a memory or the like, and if an ON signal of the headlamp switch 7 is input, the image processing means 5
Based on the position data of the known illuminated area described above, normalization processing is performed only on the other area except the illuminated area in the captured image, and peaks and valleys of a luminance distribution curve of each horizontal line are emphasized to improve contrast. That is what we did.

For example, if it is assumed that a display image as shown in FIG. 1 is obtained when the obtained captured image is displayed without normalization at night and in fog, the own vehicle in the display image is displayed. The normalization process is performed on other regions except the irradiation region H of the headlamp.

Therefore, the effect of normalization can be sufficiently obtained by emphasizing the peaks and valleys of the luminance distribution curve only in a region other than the headlamp irradiation region of the own vehicle in the captured image at night or in fog. And the contrast can be improved.

[0018]

As described above, according to the method for improving the contrast of a displayed image according to the present invention, the other regions except for the irradiation region of the headlamp of the own vehicle, which is previously known from the captured image at night or in fog, are considered. Only the process of emphasizing the peaks and valleys of the luminance distribution curve can provide a sufficient normalization effect, and can improve the contrast. This is effective in improving the quality.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an operation of an embodiment of a display image contrast improving method according to the present invention.

FIG. 2 is a block diagram of a view information providing apparatus applied to FIG. 1;

FIG. 3 is an explanatory diagram of an arrangement of a conventional view information providing device.

FIG. 4 is a block diagram of the device of FIG.

FIG. 5 is an operation explanatory diagram of FIG. 4;

FIG. 6 is an operation explanatory diagram of FIG. 4;

FIG. 7 is an operation explanatory diagram of FIG. 4;

FIG. 8 is an operation explanatory diagram of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Imaging means 2 Monitor 5 Image processing means 7 Headlamp switch

Claims (1)

(57) [Claims] 1. An image processing means for displaying, on a monitor television receiver, an image obtained by capturing an image of the front of a vehicle during nighttime fog by an image capturing means mounted on a vehicle, and displaying each horizontal line of the image by an image processing means. A method of improving the contrast of a display image, comprising: changing a luminance level of each of a maximum point and a minimum point of an upper luminance distribution curve, performing processing for enhancing peaks and valleys of the luminance distribution curve, and improving contrast of the image. A method for improving the contrast of a display image, comprising: performing emphasis processing on peaks and valleys of the luminance distribution curve only in an area other than an irradiation area of a headlamp of the own vehicle in the image.