JPH09141927A - Image recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the tone reproduction without increasing the memory by regulating the intensity level of an image data based on a data reducing through false gradation thereby facilitating error correction of emission quantity of print head. SOLUTION: When a tone is reproduced using Bayer type dither of 4×4 matrix, for example, 17 intensity levels are possible including O level. When a 8 bit image data is composed of a binary false gradation data, an original data of 0-8 corresponds to 0 and an original data of 9-24 corresponds to 1 in false gradation. Original data of 0-255 is assigned to the output value of false gradation. A data of 256 intensity levels subjected to binary false gradation is delivered through an I/F to an image output system where inter-pixel correction is performed. Subsequently, it is subjected to exposure and development thus producing a high quality image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus for performing continuous gradation recording on a silver halide photosensitive material.

[0002]

2. Description of the Related Art Conventionally, there is an image recording apparatus such as a copying machine using a print head using an LED array, a vacuum fluorescent display tube, a liquid crystal shutter array and the like. In these print heads, a large number of recording elements corresponding to print dots are arranged in a line.

[0003]

However, the image recording apparatus using the print head as described above has a variation in the amount of emitted light for each light emitting element, and the error is usually about 20% to 40%. However, in order to reproduce a photograph or the like in continuous gradation, it is necessary to set the content to at least 2% or less, and to record with higher image quality, it is necessary to set it to 1% or less. In order to achieve the error of 2% or 1% or less, a highly accurate measurement technique and calculation accuracy are required, and it is very difficult.

Further, in order to record in a continuous tone with the increase in output size such as posters and signboards, the temporary image recording memory is increased and the cost is greatly increased.

In view of the above problems, it is an object of the present invention to realize an inexpensive image output device which can easily correct a light emission amount error of a print head, does not cause an increase in memory, has good gradation reproduction. To provide a method of outputting an image.

[0006]

[Means for Solving the Problems] There are the following methods as means for achieving the above object.

(1) A silver halide photosensitive material which is a recording medium which moves in the sub-scanning direction relative to a print head having an array of light sources in which a large number of light emitting elements are arranged in a line in the main scanning direction, An image recording method for recording an image by performing exposure with an exposure amount according to image data having multiple gradations, wherein the exposure amount is based on data obtained by reducing the number of gradations of the image data by a pseudo gradation method. An image recording method characterized by the above.

(2) The amount of light emitted from a large number of light emitting elements of the print head is measured, and the element having the lowest amount of light emission is used to expose the silver halide light-sensitive material to obtain the highest density. Controlling the light emitting element of the print head to perform exposure (1)
Image recording method.

(3) The image recording method according to (1) or (2), wherein recording is performed by the print heads arranged in parallel in the sub-scanning direction.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram of an image output apparatus showing an embodiment for realizing the image recording method of the present invention.

In the image recording apparatus of this embodiment, a control apparatus such as a personal computer uses a pseudo gradation method such as a dither method to reduce the image data in which the number of bits of one pixel is reduced to L.
The ED print heads 111 and 112 and the VFPH print heads 113 to 116 are used as the photosensitive material 30 such as color photographic paper.
This is a device for writing to 1. The photosensitive material supply unit 1 is detachably provided with a magazine 2 in which the photosensitive material 301 is rolled. The photosensitive material 301 is pushed out and conveyed by the accumulator 3 from the conveying section 4 at a constant speed while keeping the feeding stability. Further, the photosensitive material 301 is kept flat in the exposure section 110 by the pressure plates 6 and 7, and can be stably fed to the developing section 10 by the accumulator 8. The photosensitive material 301 is cut into a required length by the cutter unit 9 before being fed to the developing unit 10. The cut photosensitive material 301 is color-developed, bleach-fixed, washed with water and dried in the developing section 10 and discharged to the print output section.

Next, the data flow and the exposure section 110 will be described.

FIG. 2 is a schematic diagram showing a drive circuit of the print head used in the image output apparatus of this embodiment.

There are two types of data flow, which are roughly divided into image data and a correction value described later. These are sent through the I / F 260 from a personal computer connected to control this circuit. After passing through the I / F 260, the image data is distributed according to each of red, green and blue. The image of the red component is stored in the DRAM 242. The image of the green component is stored in the DRAM 245.
The image of the blue component is stored in the DRAM 248. Then D
The RAMs 242, 245, and 248 use the address bus selectors 243, 246, and 249 to extract image data according to the position of the print head, which will be described later, and
It is sent to the inter-pixel correction circuits 231 to 236, and the exposure control unit 1
20.

As shown in FIG. 2, the exposure section 110 has a central wavelength of luminescence of 660 nm and a resolution of 3 for recording red light.
Large-format output is possible by arranging the LED print heads 111 and the LED print heads 112 having 00 dpi and the number of pixels of 2560 in a zigzag pattern. The reason for arranging them in a zigzag pattern is that it is difficult to manufacture a printhead having a long recording length with high precision when realizing a large size, and even if it is possible, it is very expensive. Therefore, as shown in the present embodiment, it is practically preferable to achieve a large size by arranging print heads for an inexpensive small size printer in a zigzag pattern. When arranging in a staggered pattern, it is preferable to arrange the print heads so that they do not overlap in the main scanning direction in order to effectively use the light emitting elements, but white lines may occur due to expansion and contraction due to temperature, etc. However, it is preferable to install it with an overlapping area of about 5 pixels, and in the overlapping area, it is possible to prevent the occurrence of white lines by performing control so that only the light emitting element of one print head outputs. preferable.

Printheads 113 and 11 for green exposure
4 and the print heads 115 and 116 for blue exposure,
A vacuum fluorescent print head (VFPH) is used, which has a relatively high brightness and a high-speed response and can be easily color-separated by a color filter. By adopting these print heads 113 to 116, the resolution and the number of pixels are the same as those of the LED print heads 111 and 112. A yellow filter is inserted in the optical paths of the green print heads 113 and 114, and a blue filter is inserted in the optical paths of the blue print heads 115 and 116 so that color separation exposure can be performed. The print heads 113 to 116 are the print heads 11 for red.
As with Nos. 1 and 112, they are arranged in a staggered pattern.

Therefore, when the green exposure portion is used as the green print heads 113 and 114, the positional deviation corresponding to the print head interval and the print heads in the conveying direction of the color photographic paper as the photosensitive material 301 (the direction of the arrow in FIG. 2). There is misalignment in the line direction. The correction of these positional deviations is performed by controlling the address bus selector 246 from the image data control CPU 244. The print heads 111 and 112 for red exposure and the print heads 115 and 116 for blue exposure are similarly controlled by the image data control CPUs 241 and 247 of the print heads. The output is synchronized by generating a light emission timing signal by performing frequency division according to the transport speed using a system clock.

The exposure control unit 120 uses the LED driver 22.
1, 222 and VFPH drivers 223 to 226. Since both basically operate with the same configuration, L
The ED driver 121 will be described as an example.

FIG. 3 is a block diagram showing the main configuration of the LED driver.

The image data output from the inter-pixel correction circuit 231 is received line by line in the LED driver 120 having a register. The LED driver 120 causes the print head 111 to emit light. The LED driver 120 includes a data output unit 221A, a light emission control unit 221B, a shift register 221C, and a latch 2 as shown in FIG.
21D and a gate 221E.

FIG. 4 is a timing chart showing the operation of the LED driver 221.

CLOCK1 is a transfer clock of image data, and D is synchronized with the falling edge of CLOCK1.
ATA1 is from the data output unit 221A to the shift register 2
21C. The / LOAD signal is for giving the light emission timing, and the light emission control unit 221B controls the gate 2
21E. The ESTB controls the light emission time and emits light during the ON time, and this light emission time is D
Controlled by setting SW to an arbitrary value, cycle 1
It is the time multiplied by / fclock.

The exposure of multi-valued image data having more than two values can be achieved by dividing the image data of one pixel bit by bit and exposing the image data a plurality of times. For example, if you want an output level of 8 bits, start with DATA from the upper bit.
Achieved by reading the value in the shift register 221C into the shift register 221C, reading the DSWn (n is the number of times of light emission required to record one pixel) corresponding to that bit from the ROM, etc., and exposing the lower bit DATA in order. It is possible to

[0024]

【Example】

Example 1 Red, green, blue, 8 bits for each color on a personal computer
The image of (256 gradations) is binarized and transferred to the I / F 260.

FIG. 7 is a schematic view showing a Bayer type dither matrix.

As a binarization method, an error diffusion method or a dither method is generally used. As a means of such pseudo gradation conversion, an imaging part 1 (edited by the Electrophotographic Society, Photo Industry Publishing Co., Ltd.) is used. A method using a dither method or an error diffusion method is generally known as shown on pages 30 to 43 of the publication, and this method is also used here.

For example, when gradation expression is performed using a Bayer-type dither method with a 4 × 4 matrix, as shown in FIG. 7, 17-level gradation expression is possible including 0 level where nothing is printed. is there. When 8-bit image data is used to create binary pseudo gradation data using this method,
It can be realized by allocating to gradation data. For example, when the original image data is 0 to 8, it is 0 by the pseudo gradation method,
When the original image data is 9 to 24, it is 1 by the pseudo gradation method.
As described above, the original data of 0 to 255 is assigned to the output value by the pseudo gradation method. This allocation method differs depending on the desired gradation characteristics, and the allocation is determined based on the data actually output by the pseudo gradation method.

In this way, the data of 256 gradations is 2
The image data subjected to the pseudo gradation process to the value is sent to the image output device via the I / F 260, and the inter-pixel correction process is performed, and then the exposure process and the development process are performed to obtain an image.

Here, a method of setting correction values in the inter-pixel correction circuits 231 to 236 will be described.

When the above-mentioned recording method is used as shown in the problem, the array print head has a variation in light emission from pixel to pixel, and it is necessary to perform a correction operation. In the binary system as shown in this embodiment, it is preferable to record by one emission in the above-mentioned device for the purpose of cost reduction and simplification of the device, and the method will be described.

FIG. 5 is a schematic diagram showing a step chart for correcting the light emission amount of a binary system.

As the simplest method, as shown in FIG. 5, the output in which the set value of DSWn (n = 0 to 7) is changed is performed, and there is no unevenness visually, and the highest density is obtained. The value is selected and used as the value of DSWn (n = 0 to 7). In FIG. 5, when DSWn is n = 5, there is no unevenness at 3072, and the maximum density is reproduced. However, considering the deterioration characteristics of the head over time, the value should be set to a value 20% or more larger than that. Is preferred, in this case the DSW is 370
It was set to 0.

However, although the above method is simple, it involves visual judgment, which causes a factor including a setting error, and a standardized start-up method is required at the time of shipping.

FIG. 8 is a schematic view showing a jig for measuring the light emission amount of the print head.

For standardized start-up at the time of shipment, etc., refer to FIG.
Photometry is performed using the photo sensor 401 as shown in FIG. The photometry is performed by moving the photo sensor 401 using the sensor moving table 402 for each light emitting point, driving the print head 111 to emit light, and converting the output from the photo sensor 401 into a voltage for analog / digital conversion. Be seen. The DSW is determined so that the product of the minimum value of the voltage values obtained at this time and the DSW becomes a certain value or more.

As a result of image output using such a system, it becomes possible to obtain a simple and high-quality image by the simple correction method between pixels as described above. The output by such a method becomes more effective as the output size increases.

Embodiment 2 Next, as a pseudo gradation method, a method of increasing the number of gradations per pixel to be more than two and expressing more gradations will be described.

FIG. 6 shows the reproduced density of one light emitting element with respect to the DSW.

When recording 9 values (4 bits are required) per pixel, 8 divisions are performed on the reproduction density axis, the minimum density (Dmin) is set to 0, and the rest are allocated at even intervals so that the DSW axis is displayed. As shown, it is divided into areas from 0 to 8. Normally, when the area is divided in this way, the 9-level DSWs 0 to 8 are set so as to be the midpoint of this area. However, by allowing the density variation within this area, the allowable range of the inter-pixel correction is widened, and the accuracy of the inter-pixel correction operation can be recognized even outside the accuracy of 1% to 2%. The pixel-to-pixel correction can be realized by using the output of the photosensor of the first embodiment and setting the inverse of the standardized value for the minimum light amount to DSW. For this purpose, in terms of accuracy, the DS can be freely set between 0 and 4095.
It is necessary to be able to change W, and this can be achieved by the following method. For example, DSW0 is 2048, DSW1
= 1024, DSW2 = 512, DSW3 = 256, D
SW4 = 128, DSW5 = 64, DSW6 = 32, D
SW7 = 16, DSW8 = 8, DSW9 = 4, DSW1
By setting 0 = 2 and DSW11 = 1, these D
This can be realized by combining SWn (n = 0 to 11) and exposing a plurality of times.

FIG. 9 is a schematic diagram showing an example of a matrix for performing the pseudo gradation method used in the second embodiment.

In the personal computer, data is entered according to the rules shown in FIG. 9. Basically, it is the same as the Bayer type of the dither method, and 2 is filled when it is filled with 1.
Insert When it is filled with 2, it is set to be filled with 3, and so on. In the example of FIG. 9, the input represents the original 8-bit image.

The data which has been subjected to the pseudo gradation processing is I / F 260.
It was possible to obtain a high-quality image by printing, exposing, and developing.

[0043]

According to the invention of claim 1 or 2, even if a large RAM capacity which is disadvantageous in cost is not used,
It is possible to obtain a high-quality photographic image with a simple configuration, and it is particularly effective for an apparatus that uses a photographic process to output a large size such as a poster that has conventionally required a large RAM capacity. According to the third aspect of the invention, it is possible to output a large size image using a small print head.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image output apparatus showing an embodiment for realizing an image recording method of the present invention.

FIG. 2 is a schematic diagram showing a drive circuit of a print head used in the image output apparatus of this embodiment.

FIG. 3 is a block diagram showing a main configuration of an LED driver.

FIG. 4 is a timing chart showing the operation of the LED driver 221.

FIG. 5 is a schematic diagram showing a step chart for binary light emission amount correction.

FIG. 6 is a graph showing reproduced density of one light emitting element with respect to DSW.

FIG. 7 is a schematic diagram showing a Bayer type dither matrix.

FIG. 8 is a schematic view showing a jig for measuring the light emission amount of the print head.

FIG. 9 is a schematic diagram showing an example of a matrix for performing the pseudo gradation method used in the second embodiment.

[Explanation of symbols]

 115,116 VFPH print head for blue image recording 120 Exposure control unit 221 LED driver 221A Data output unit 221B Light emission control unit 221C Shift register 221D latch 221E gate 222 LED driver 223 to 226 VFPH driver 231 to 236 Inter-pixel correction circuit 243,246 , 249 Address bus selector 241, 244, 247 Image data control CPU 242, 246, 248 DRAM 250 R, G, B data distribution circuit 260 I / F 270 Printer control CPU 301 Photosensitive material 401 Photo sensor 402 Sensor movement table

Claims (3)

[Claims] 1. A silver halide light-sensitive material, which is a recording medium that moves in the sub-scanning direction relative to a print head having an array of light sources in which a large number of light emitting elements are arranged in a line in the main scanning direction, In an image recording method for recording an image by performing exposure with an exposure amount according to image data that is a gradation,
The image recording method, wherein the exposure amount is based on data obtained by reducing the number of gradations of the image data by a pseudo gradation method. 2. The quantity of light emitted from a large number of light emitting elements of the print head is measured, and the quantity of light emitted from the element having the lowest quantity of light emitted from the measurement exposes the silver halide light-sensitive material to obtain the highest density. The image recording method according to claim 1, wherein the light emitting element of the print head is controlled to perform exposure. 3. The image recording method according to claim 1, wherein recording is performed by the plurality of print heads arranged in parallel in the sub-scanning direction.