JPS6037466B2 - Mask plate for improving image sharpness in image scanning recording devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is intended to improve the sharpness of multiple images by emphasizing the details and contrast of images to be reproduced in an image scanning recording device such as a color scanner for plate making or a color facsimile. Regarding the mask plate used.

Conventionally, in this type of device, methods for improving the sharpness of reproduced images include electrical methods and optical methods. The former is known as main signal peaking processing and crisping processing, and the latter is known as main signal peaking processing and crisping processing. This method is known as the unsharpened mask method or the differential mask method.

FIG. 1 shows the principle of detail enhancement using an unsharp mask signal, where A is the main signal and B is the unsharp signal.

The unsharp signal is a so-called blurred image signal whose signal level changes more slowly than the main signal in response to changes in image density.The unsharp signal is a so-called blurred image signal that is used as a mask installed in the incident optical path during photoelectric scanning of the original image, as shown in Figure 3. This can be obtained by making the diameter of the plate 2 larger than the diameter of the main signal mask plate 1, for example, by increasing the diameter by two to three times.

That is, the photoelectric conversion element 2 is transmitted through the main signal mask plate 1.
From the main signal A that has been photoelectrically converted by the intensifier 5 and amplified by the intensifier 5,
Also unsharp signal mask plate 2, photoelectric conversion element 4
, when the unsharp signal B obtained through the intensifier 6 is subtracted by the differential intensifier 7, an unsharp mask signal such as C is obtained. This unsharp mask signal C is added to an adder 9
When added to the main signal A, the difference in density is expanded in a portion of the original image where there is a density change as shown in D, and a detail emphasis effect is produced in the reproduced original image, thereby improving the sharpness of the original image. This effect emphasizes details in both the main scanning and sub-scanning directions. The sliding resistor 8 shown in FIG. 3 is used to adjust the gain of the differential amplifier 7 and vary the mask signal amount. Figure 2 shows the principle of a method for enhancing image contrast and improving sharpness using a differential mask.The aperture of the mask plate used to obtain the blurred signal is made larger than in the case of an unsharpened mask. For example, the aperture of the main signal mask plate 1 is made larger than that of the unsharp mask, for example, the aperture size of the main signal mask plate 1 is two or more needles, but in the same manner as the unsharp mask. It is done. The former improves the sharpness of the image by emphasizing the details on the reproduced screen, that is, the rise and fall of the image, whereas the latter focuses on the visual characteristics. At the same time, the sharpness of the reproduced image is improved by emphasizing the contrast of the image, and it is desirable to apply both methods at the same time in order to obtain a reproduced image that is faithful to the original and has sharp colors.

That is, as shown in FIG. 4, when the unsharp mask signal B obtained from the unsharp mask method and the differential mask signal C obtained from the differential mask method are added to the main signal A, both detail and contrast are improved. An emphasized main signal D that is faithful to the original image and sharp is obtained. Therefore, conventionally, each mask plate for the main signal unsharp mask signal and the differential mask signal is provided independently together with each optical system and processing circuit, and preferably the contrast of the image is enhanced by the differential signal. 1, each mask signal was added to the main signal at a ratio of 3 to 4 to enhance the detail of the image using the unsharp mask signal to improve the sharpness of the duplicated image. However, such a conventional method has the disadvantage that the optical system is complicated and that the positioning of each signal mask plate with respect to the optical axis must be performed with high precision, making it more time consuming than before.

The present invention eliminates the need to separately provide a mask plate for creating an unsharp signal that emphasizes the details of an image and a mask plate for creating a differential mask signal that emphasizes the image in order to improve the sharpness of the reproduced screen, and it is possible to improve the sharpness by itself. It relates to a mask plate from which a blur signal having characteristics of both a mask signal and a differential mask signal can be obtained,
FIG. 5 shows an example of the mask plate.

That is, this mask plate 1 consists of an annular semi-transparent part 12 and an opaque part 13 having a density ratio of 1.5 to 2.0 with respect to the entrance part 11 and the opening part 11, respectively. The ratio of the opening diameter of the closing part to the opening diameter of the main signal mask plate is 2 to 3 times the opening diameter of the main signal mask plate for the closing part 11, and 2 times for the semi-transparent part 12.
．． It's more than a peep sound.

The blur signal obtained from such a mask plate 10 is transmitted through the opening 11
However, due to the influence of the semi-transparent portion 12, as shown in FIG. Fan-sharp signal in Figure 1B and Figure 2B
It has a shape that looks like the sum of the blur signals of . Therefore, if the mask plate 10 shown in FIG. 5 is used in place of the aperture 2 shown in FIG. 3, the unsharp mask signal mask plate and the differential mask signal mask plate can be used in parallel, as in the conventional case. You can get exactly the same effect as if you did.

That is, by subtracting the blur signal shown in FIG. 6B from the main signal shown in FIG. 6A, a mask signal as shown in FIG. 6C is obtained, and by adding the mask signal to the main signal, the detail A main signal with enhanced color and contrast can be obtained. As described above, if the mask plate according to the present invention is used as a mask plate for improving the sharpness of a reproduced screen, the optical system and processing for creating unsharp mask signals and differential mask signals can be There is no need to provide a separate circuit, which simplifies implementation, and the mask plates for creating unsharp mask signals and for creating differential mask signals are provided on the same plane. This has many practical effects, such as the time required for aligning the optical axis to be considerably shortened compared to the conventional method.

[Brief explanation of the drawing]

FIG. 1 shows the principle of image detail enhancement using an unsharp mask signal, FIG. 2 shows the principle of image contrast enhancement using a differential mask signal, and FIG. 3 shows the principle of image contrast enhancement using an unsharp mask signal. The example shown in the figure, FIG. 4, shows waveforms when improving the sharpness of an image using an unsharp mask signal and a differential mask signal.
FIG. 5 shows an example of the mask plate according to the present invention, and FIG. 6 shows waveforms when the mask plate shown in FIG. 5 is used to improve the sharpness of an image. 1...Mask board for main signal, 2...Mask board for creating unsharp mask signal (differential mask board), 5, 6...Mask plate, 7... Differential multiplier, 8... informational resistance, 9... adder,
10...Mask plate, 11...Closing part,
12... Semi-transparent part, 13... Opaque part. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. A main signal is formed by photoelectrically converting the light beam that scanned the original image through a mask plate having a relatively small diameter aperture. When improving the sharpness of multiple images in an image scanning recording device by forming a blur signal using a mask plate having a large-diameter opening and adding and subtracting these two signals as appropriate, the opening of the mask plate for forming the blur signal is The concentration ratio around the opening to the opening is 1.5 to 2.
1. A mask plate for improving image sharpness in an image scanning and recording apparatus, characterized in that a ring-shaped semi-transparent part of 0 is formed to simultaneously enhance detail and contrast of a reproduced image to improve sharpness.