JPS61177865A - Imaging device - Google Patents

Abstract

PURPOSE:To attain a high gradation expression with less picture image memory by applying a fine noise generated in accordance with position information of a picture element to read-out picture image data and transferring and printing it on an imaging head. CONSTITUTION:After the position of the picture element changes the gamma transformation table of input picture image data, data is fetched into the picture memory of n2-bits, which means a small number of bits. At this time, the number of reduced bits of data are truncated. At the time of imaging, the read-out data of N2 bits is set to a high level bit, and data of a-bits, which is generated by the position information of the picture element, is set a low level bit, both of which are transferred to the head to be imaged. At this time a difference between the gradation expression resolution of the head and the bit accuracy of the picture image memory is compensated by the appropriate data generated by the position information of the picture element. The appropriate data carries the fine noise on the fetched picture image data, and selects the data which makes a dummy gradation inconspicuous.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a drive circuit for a multi-gradation printing apparatus.

[Conventional technology]

Conventionally, tone correction of image data has been performed using a gamma conversion table. Generally, the pit precision of the Aρ conversion circuit, the bit precision of the two-box collection memory, and the number of bits of the gradation expression capability of the printing head are the same.

[Problem that the invention seeks to solve]

However, the problem with the conventional technology mentioned above is that if you increase the full 1-gradation expression capability and increase the bit precision, the memory for 5 images will increase significantly. have The present invention is intended to solve these problems, and its purpose is to express high gradations with a small amount of image memory.

[Means for solving problems]

The printing apparatus of the present invention includes a 31-bit precision A/D conversion circuit and a sl+αα pit power bn2 bit output (n*
＞nxaα〉0) gamma conversion table memory and Shoku3
It has a head with a bit image memory and a gradation expression capability of %n2+α bits, and the α bit is a value taken out based on pixel position information.

〔Example〕

FIG. 2 is an example of the process of converting image data according to the present invention, and shows the case where n1=6, n2=4, and a=2. This will be explained in conjunction with FIG. 1.

The input image data is converted to n1 = 6 bits through the Aρ conversion circuit.The pixel position counting counter outputs data of 1 bit in the vertical direction and 1 pit in the horizontal direction, and a total of α = 2 bits, as shown in the lower left diagram of Figure 2. The same step is repeated for every 4 positions.N1+α bits of data are input to the gamma conversion table memory at the 0th order.At this time, at pixel position A, the image memory pre-Ei is Among them, numbers 11 to 14 are stored as 16, and numbers 15 to 18 are stored as addition. Also, at the pixel position of B,
12 to 15 are stored as 16, and 16 to 19 are stored as titles.
, if you want to read this to the primary order, which is rounded to the value number 16.

If the heel memory data E is 16 and the pixel position is A.

The value of α=2 bits is manipulated so that this can be read as 12 below the output pixel position, and the data is sent to the latch.

Similarly, the image memory data E is 16 and 5 pixels I[B.

In the case of C and D, the output pixel position G, H, and 13°14
, sends data to the latch so that it can be read as 15.

The method for manipulating the value of α = 2 bits is as follows: The data sent to the latch is % n1 = 6 bit data t - fLx = This is a book that manipulates the value considered as the core value when rounding to 4 pits so that it regenerates. According to the above structure of the invention, as shown in FIG. 1, after changing the gamma conversion table of input image data depending on the pixel position, the data is taken into an n3-bit image memory having a small number of bits.

At this time, the number of bits of data has decreased (n2−
? During printing, the n2-bit data read from the image memory is used as the upper bit, and the α-bit data generated based on the pixel position information is used as the lower bit. The image is transferred to a head capable of expressing bit gradations and printed.

Printing with data with a small bit precision for a head capable of high gradation output will not make full use of the head's capabilities, and the output image will be degraded with fewer gradations and noticeable false contours. Therefore, the difference between the gradation expression ability of the head and the bit f# degree of the image memory is calculated by 2.
It is filled in with appropriate data generated based on pixel position information. Appropriate data to be generated at this time is selected so as to add minute noise to the captured image data to make the pseudo gradations all inconspicuous. Adding noise generated by pixel position information in this way means that the original image information is not correctly expressed when image data is viewed in a minute range. Therefore, in the present invention, as shown in Fig. 2, a value obtained by adding a small amount of noise generated by the position information of two pixels to the image data taken in K, and a value of the image data after IA/D conversion of the input image. The gamma conversion table is changed according to the position information of one pixel so that the difference is minimized. by this,
The error between the input image data and the output image data is equal to the size of the least significant bit of the image memory, and it is possible to obtain a natural image with no noticeable pseudo gradation.

〔Effect of the invention〕

As described above, according to the present invention, the bit precision of one image memory can be reduced compared to the bit precision of the A/D conversion circuit and the bit precision representing the gradation expression ability of the printing head, thereby reducing costs. It has a big effect. Also, by adding minute noise generated according to the position information of one pixel.

A good output image with few false contours can be obtained.

Further, it has the effect that the head's high gradation expression ability can be fully utilized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the printing apparatus of the present invention. FIG. 2 is a diagram showing an example of a process in which image data is converted according to the present invention. that's all

Claims (1)

[Claims] (1) In a printing device that modulates the printing amount for each pixel to express gradation, the drive circuit is an A/D conversion circuit (n
_1 bit precision), gamma conversion table memory, image memory (n_2 bits, n_2<n_1), n_3
A printing head with the ability to express bit gradation (n_3>n_
2), during gamma conversion, the gamma conversion table is switched depending on the pixel position information and is loaded into the image memory;
A printing apparatus characterized in that minute noise generated according to pixel position information is added to the image data read from the image memory and transferred to a printing head for printing.