JP3486796B2 - Image forming method and image forming apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method and an image forming apparatus for recording an image by correcting variations in recording characteristics of each recording element of an array print head having a plurality of recording elements arranged in an array.

[0002]

2. Description of the Related Art Recently, a digital output device has a selfoc lens array on an array print head in which fine light emitting elements are arrayed at a predetermined pitch to obtain a desired resolution for enabling high speed image recording. There is a device for recording a digital image by forming a beam spot on the photosensitive material via the light spot. Such a digital output device needs to be controlled with a gradation of at least 200 levels or more in order to express a gradual gradation such as a person's skin shadow or a skyscape. As a method of reproducing such gradation, the arrayed print head is exposed a plurality of times at a plurality of light emission levels.
A method of performing multi-gradation recording of 00 level or higher has been proposed.

The array-type print head described above is an LE
It is configured by arranging D light emitting elements and vacuum fluorescent tubes, a PLZT print head using an appropriate backlight, an optical shutter array such as a liquid crystal shutter array print head, and semiconductor lasers arranged in an array. The light emitting elements forming the array print head generally have variations in light emitting characteristics. The variations in the light emission characteristics of the respective light emitting elements forming the array print head are recorded as they are as the unevenness of the light and shade of the image. 2 mentioned above
A digital output device that employs a modulation method that reproduces multiple gradations of level 00 or higher becomes a decisive factor for image quality deterioration due to the variation in the light emission characteristics of the light emitting elements described above.
The image recording apparatus using the print head described above has a variation in the amount of light emission for each light emitting element,
Usually, there is an error of about 20% to 40%, and it is necessary to set it to 2% or less at the minimum when reproducing a photograph or the like with continuous gradation, and 1% for recording with higher image quality.
I needed to: In order to achieve the error of 2% or 1% or less, highly accurate measurement technology and calculation accuracy are required, which is very difficult. In order to prevent such a problem, a solid image having a predetermined gradation is output on a photosensitive material, the solid image density of the developed photosensitive material is measured, and the correction amount of the exposure amount for each light emitting element is obtained. The exposure time was corrected.

[0004]

However, in the above-described correction method, the length from end to end of the solid image visualized on the photosensitive material is determined by the number of light emitting elements in the main scanning direction of the array print head. Since the image density data measured by roughly estimating the pixel positions on the image density data that are divided and continuous are associated with each light emitting element of the array print head, the image density data obtained from the densitometer and the array print Since the positions of the respective light emitting elements arranged in the head in the main scanning direction do not match, the exposure amount cannot be accurately corrected. This is considered to be caused by the following.

An array print head has, for example, 300
It is necessary to arrange light emitting elements at a constant interval of about 85 μm in order to obtain a resolution of dpi, but a long array shape in which 2500 or more light emitting elements are mounted at one time for the sake of yield in manufacturing an LED array. Unable to manufacture printhead. Generally, we manufacture short LED array chips,
Such LED array chips are joined together to manufacture a long LED array. Therefore, even if the light emitting elements on the LED array chip are arranged at equal intervals, it is not possible to maintain a constant interval in the joining process, and as a long LED array, the arrangement pitch of the light emitting elements becomes uneven. ing.
Further, although the vacuum fluorescent print head can be manufactured in a long size at a time, it is difficult to manufacture the light emitting elements accurately at regular intervals. Similarly to the above, it is difficult to accurately arrange other light emitting elements at regular intervals. Since it is not possible to detect the exact position of each light emitting element by the position detecting method of the light emitting element obtained by simply dividing the number of light emitting elements into equal parts due to the variation in the arrangement pitch of each light emitting element, it is possible to correct the exposure amount. Has become.

Further, for example, in an array print head for outputting a digital image with a resolution of 300 dpi, light emitting elements having a pixel size of 80 μm in the element array direction are arranged at intervals of 85 μm. If recorded, the pixel position can be detected because it basically corresponds to the peak of the density data. However, the image forming optical system of the array print head forms an image on the photosensitive material at intervals of several mm to several tens of mm by the image forming optical system composed of SELFOC lenses, and the photosensitive material is silver halide. In the case of a photosensitive material, unlike a photosensitive drum used in an electrophotographic process, distortion of the photosensitive material is likely to occur during transport due to the influence of the stiffness of the support, etc. It tends to appear as a gap. Such defocus causes noise of the image density of the patch image after being visualized, and sometimes the peak corresponding to the light emitting element cannot be detected.

Further, when the light-sensitive material is a silver halide color photographic paper, since it has a reflective support, the light transmitted through the photosensitive layer is reflected from the boundary surface with the reflective support or from the back surface to expose the photosensitive layer. Since the beam spot is bleeding due to halation, the peak may not be detected due to the bleeding of the visualized patch image.

When an array in which light emitting elements larger than the pixel pitch are arranged in a staggered pattern is used, the peaks of the density data cannot be detected because the images of adjacent pixels overlap each other.

For the above reasons, there has been a problem that an accurate exposure amount correction amount cannot be obtained for each light emitting element of the array print head.

In view of the above technical problems, an object of the present invention is to
An object of the present invention is to provide an image forming method that can accurately correct density unevenness.

[0011]

The above object can be achieved by the following constitutions.

(1) Recording characteristics of each recording element are recorded by recording an image on a photosensitive material based on image data using a print head in which a plurality of recording elements are arranged in an array and measuring the density of the image. And an image forming method for recording an image using the correction amount, wherein the image is an image recorded with a gap of at least one recording element in the recording element array direction. Image forming method.

The image forming method of (1) is provided with the above configuration, and the pixel position of the patch image density data and each light emission of the array print head are not affected by defocus of the beam spot and halation by the beam spot. It is possible to obtain a correction amount for each light emitting element by accurately matching the element position.

(2) The image is a periodic image having a constant period in the recording element array direction (1)
Image forming method. With the above configuration, since the recorded image has periodicity, the peak detection algorithm can be simplified, speeded up, and highly accurate.

(3) In obtaining the correction amount, the correction amount is calculated after converting the density measurement data of at least two positions at different positions in the recording element array direction for each recording element into exposure amount data. The image forming method according to (1) or (2), which is characterized. With the above configuration, the exposure amount calculation can be performed with high accuracy and simplification.

(4) The image forming method according to (3), wherein a characteristic curve of the photosensitive material is used in converting the density measurement data into exposure amount data. With the above configuration, the exposure amount calculation can be performed with high accuracy and simplification.

(5) The image forming method according to any one of (1) to (4), wherein the photosensitive material is a silver halide photosensitive material.

(6) The image forming method according to (5), wherein the photosensitive material has a reflective support.

FIG. 10 is a schematic diagram showing print heads arranged in an array.

The array shape mentioned here includes not only the linear shape as shown in FIG. 10A, but also the Kurile array as shown in FIG. 10B and the array as shown in FIG. 10C. In addition, the numbers as shown in the drawing are assigned to the respective recording elements, and the adjacent element in the recording element array direction indicates the element adjacent to the number.

(7) A printhead in which a plurality of recording elements are arranged in an array, and a printhead control means for driving and controlling the printhead based on image data,
An image forming apparatus comprising: a print head, a recording medium, or a conveyance unit that conveys both, an image forming mode in which the print head control unit controls the print head based on image data, and an array of the recording elements. An image forming apparatus having a correction mode for driving at least every other recording element in a direction. By providing the above-described configuration, the influence of drooping of the recorded image due to focus shift and scattering is less likely to occur, so that the peak detection for each recording element on the recorded image becomes accurate.

(8) The image forming apparatus according to (7), wherein the image data is a periodic image having a constant period in the recording element array direction. By providing the above configuration,
Since the recorded image has periodicity, the peak detection algorithm can be simplified, speeded up, and highly accurate.

(9) In obtaining the correction amount, it is necessary to calculate the correction amount after converting the density measurement data of at least two positions at different positions in the recording element array direction for each recording element into exposure amount data. The image forming apparatus according to (7) or (8), which is characterized. With the above configuration, the exposure amount can be calculated with high accuracy, and the correction amount can be accurate.

(10) The image forming apparatus according to (9), wherein the characteristic curve of the photosensitive material is used in converting the density measurement data into exposure amount data. With the above configuration, the exposure amount calculation can be performed with high accuracy and simplification.

(11) The image forming apparatus according to any one of (7) to (10), wherein the photosensitive material is a silver halide photosensitive material.

(12) The image forming apparatus according to (11), wherein the photosensitive material has a reflection support.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an image forming method and an image forming apparatus used therefor according to the present invention will be described below with reference to the drawings.

The image forming method will be described prior to the description of the image forming apparatus.

In the image forming method according to the present embodiment, print heads 30a to 30c in which a plurality of light emitting elements, which are recording elements, are arranged in an array are driven by image data having a predetermined gradation, and printing is performed as a recording medium. Imagewise expose on paper 20,
Based on the image density of the patch image obtained by developing the photographic printing paper 20, the variation in the exposure amount, which is the recording characteristic of the light emitting elements forming the print heads 30a to 30c, is corrected,
It forms an image. The procedure of such an exposure amount correction method will be described with reference to FIGS.

FIG. 1 is a flow chart showing a method of correcting the exposure amount of the print head in this embodiment.
FIG. 4 is a schematic diagram showing a patch image for exposure amount correction, FIG. 3 is a graph showing reproduction density with respect to image data value DSW of one light emitting element, and FIG. 4 is a graph showing sampled density data. FIG. 5 is a schematic diagram showing a method of converting density data into light amount data.

First, the image forming apparatus exposes the exposure amount correction patch image as shown in FIG. 2 on the printing paper (step 1 shown in FIG. 1). This step 1 will be described in more detail.

When the light emitting elements are numbered from 1 in the arrangement direction (X direction), only the odd elements are exposed by the same DSW (see the first stage of FIG. 2). Similarly, the even
Exposure with W (see second step). Also, the number of the light emitting element is divided by 4, and only 1 element is exposed by the DSW (see the third stage). Similarly, with only the remaining 2 elements, the DSW
Exposure (see 4th step)
Exposing with W (5th step), with only the element with no remainder, the DS
It is exposed with W (see the sixth step). Further, all the recording elements are simultaneously exposed by the DSW (see the seventh step).

It should be noted that, in this case, each element in each of the above stages has a DS.
W has the same value, and the average density of the 7th step is about 1.0.
The value is

The photographic paper 20 is conveyed to the developing device, and the exposure amount correction patch image is visualized on the photographic paper 20 by the developing process.

The exposure amount correction patch image formed on the photographic printing paper is markedly measured by a densitometer (step 2 shown in FIG. 1). The densitometer sequentially measures the concentration in the range of 5 μm in the X direction and 1 mm in the Y direction at a pitch of 5 μm in the X direction from the end of each step.

FIG. 4 is a graph in which a part of the density data obtained by measuring a certain step of the exposure amount correction patch image is plotted in the array arrangement direction and connected by a curve.

FIG. 4A shows an array print head in which recording elements having a size of 80 μm in the recording element arrangement direction are arranged at intervals of 85 μm in the recording element arrangement direction to obtain a resolution of, for example, 300 dpi. ), The image density from the patch image for exposure amount correction obtained by emitting light is shown by a solid line, and corresponds to the first or second step in FIG. FIG. 4B shows, for example, an array print head in which light emitting elements having a size of 80 μm in the recording element arrangement direction are arranged at intervals of 85 μm in the recording element arrangement direction in order to obtain a resolution of 300 dpi, every 3 pixels (recording elements). The image density measured from the exposure amount correction patch image obtained by light emission is shown by a solid line, and corresponds to the third to sixth rows in FIG. FIG. 4C shows an exposure amount obtained by emitting all light from an array print head in which recording elements having a size of 80 μm in the recording element arrangement direction are arranged at intervals of 85 μm in the recording element arrangement direction in order to obtain a resolution of 300 dpi, for example. The image density measured from the correction patch image is shown by a solid line and corresponds to the seventh row in FIG.

The curve shown by the dotted line shows the density according to the individual exposure dose from each recording element of the array print head, and the solid line shows the density data measured by the densitometer. The density data shown by the solid line is larger than the density data shown by the dotted line. This is because it overlaps with the adjacent pixel due to halation or the like due to irregular reflection of the printing paper. 4 (a) and 4 (c)
It can be seen that the density data shown in (3) shows that the density of each pixel is high due to the overlap. The density data in FIG. 4B is obtained by turning on the light emitting element every three images as described above, but it can be seen that the density data is not affected by the overlap.

In the density data of the graph shown in FIG. 4 (c), peaks cannot be detected due to overlap. However, the concentration data in the graphs shown in FIGS. 4A and 4B can distinguish the peak level. The peak position of such density data coincides with the image formed on the photographic paper in the vicinity of the center of the light emitting elements forming the array print head. The position can be detected. Therefore, by specifying the peak position, it is possible to obtain an accurate exposure amount of each light emitting element from the pixel density near the peak position. A method for accurately detecting such a peak position will be described below.

The sampled concentration data group is shown in FIG.
As shown in (a), the high and low densities of the density data are in the non-linear region, so that the density shown in FIG. 5 (a) cannot be accurately converted into the light quantity. In order to solve such a problem, in the present embodiment, the density data is log-logged by using the characteristic curve (see FIG. 5B) of the photographic paper which is a photosensitive material.
Convert to E. As a result, the density data can be converted into logE from low density to high density. This is shown graphically in FIG. 5 (c). Further log
The exposure amount E is obtained from E. This is shown graphically in FIG. 5 (d) (step 3 shown in FIG. 1). The average exposure amount is calculated from such an exposure amount E data group, and the point where the average exposure amount and the exposure amount E data cross (S ₁ in FIG. 5D,
S ₂ , S ₃ , S ₄ ) etc. are obtained, and the central position of the area where the exposure amount between two adjacent points of these is larger than the average exposure amount (P ₁ , P ₂ etc. in FIG. 5D) ) As the center position of the light emitting element is performed remarkably (step 4 shown in FIG. 1).

Next, the obtained light amount data of the central position and the light amount data of the left and right fixed widths are integrated to obtain exposure amount data of each light emitting element. Here, the exposure data of the central position and the right and left 8 points are integrated (step 5 shown in FIG. 1).

Exposure amount data E of each element obtained next
The average value E ₀ of the exposure amount data of all the elements is obtained from _i (i is the element number), and this is used as the reference exposure amount, and the ratio C _i between the exposure amount of each recording element and the reference exposure amount is the exposure amount of each element. (Step 6 shown in FIG. 1). Where C _i = E ₀ / E _i
Is. The reference light amount is not limited to the average value and may be any value.

The obtained exposure correction amount C _i of each element is
An exposure amount correction circuit 100 stores an image in which variations in the exposure amount of each recording element are corrected by multiplying the exposure amount of each pixel corresponding to the time of image output with the converted image data (FIG. 1). Step 7) shown in.

The above is the method of correcting the exposure amount of the print head in this embodiment.

As a concrete patch image, 1 in FIG.
The correction amounts of all the pixels can also be obtained by outputting only the second stage and the second stage. In addition, 3 to 6 in FIG.
By outputting only the stage, the correction amounts of all the elements can be obtained from these four stages.

Further, as described above, not only a periodic image such as an image with every other pixel but an image with every three pixels is used, and a patch image of a pattern which is not recorded by an adjacent element may be output and used in a required number of steps.

It is preferable that the patch image is an image having a constant cycle as shown in FIG. 2, because the process of determining the approximate pixel position can be simplified and the speed can be increased.

The DSW of the patch image is set so that the average density of all pixel output stages (7th stage in FIG. 2) is 1.0 as in this example, but it is not limited to this, but it is preferable. The average concentration is 0.5 to 1.5, more preferably 0.1.
The DSW in the range of 7 to 1.3 can use the linear portion of the characteristic curve of the photosensitive material when converting the density data into the exposure amount data, which is advantageous in that the conversion process can be simplified.
It is also possible to output a plurality of different DSW stages and use these to obtain the correction amount.

Next, a digital output device equipped with an array print head suitable for the exposure scanning method of the present embodiment will be described with reference to FIGS.

FIG. 6 is a block diagram showing a schematic configuration showing an example of the image forming apparatus, and FIG. 7 is a block diagram of a print head control circuit.

The print head may be one having a plurality of recording elements arranged in one row or a plurality of rows at a predetermined pitch in order to obtain a desired resolution, and one having LED light emitting elements or vacuum fluorescent tubes arranged or an appropriate one. PLZT with backlight
A printhead, an optical shutter array such as a liquid crystal shutter array printhead, an array of semiconductor lasers arranged in an array, and a thermal head. An apparatus capable of forming an image of multiple gradations, such as an apparatus for recording on a silver halide photosensitive material with various recording element arrays or an apparatus for recording with a thermal head using sublimable ink, is particularly preferable. The print heads as described above may be appropriately combined and used as the print heads 30a to 30c. When a liquid crystal shutter and a light emitter are used, there is a high possibility of two-dimensional arrangement in addition to the array arrangement, which is particularly suitable for speeding up recording and enlarging an image. In the case of a two-dimensional array,
Even if the recording time of each element is long, it is possible to prevent the overall image output speed from slowing down, and the gradation discontinuity caused by recording multiple times on the same pixel is small, and good gradation is achieved. Becomes Also, LED array, VFP
The H and ferroelectric liquid crystal shutters have high-speed switching characteristics, and the gradation discontinuity caused by recording a plurality of times on the same pixel is small, resulting in good gradation. Further, in this embodiment, the highest effect can be obtained by using a light-sensitive material having a soft gradation characteristic such as a silver halide light-sensitive material as a recording medium, and the effect of controlling the light emission time becomes the density control of a minute region. Since the image is a faithful density-modulated image, smooth and pictorial image quality can be obtained.

In the following embodiments, the LED arrays and VF are used as the print heads 30a to 30c for convenience of explanation.
Description will be made assuming that PH is adopted.

The image forming apparatus conveys a color photographic printing paper (hereinafter simply referred to as photographic printing paper) 20 fed from a roll by a supporting drum 1 rotated by a driving source (not shown) in the direction of a white arrow and driven by a drive circuit 200. The exposure amount of the red print head 30a, the green print head 30b, and the blue print head 30c is controlled according to the image data to sequentially expose each color at a predetermined position of the photographic printing paper 20.
After forming a latent image of a color image on the photographic paper 20, the photographic paper 2
0 is conveyed to the developing device by the support drum 1.

The image data is sent from the personal computer through the I / F 1. After passing through the I / F 1, the image data is distributed by the R, G, B data distributor 3 in accordance with each of red, green and blue. The image of the red component is stored in the DRAM 4. The image of the green component is stored in the DRAM 5.
The image of the blue component is stored in the DRAM 6. Then CPU
After the image data 2 is taken out from the DRAMs 4, 5 and 6 according to the position of the print head, it is sent to the exposure amount correction circuit 100 and sent to the drive circuit 200.

Each of the print heads 30a to 30c is an array-like light source of one row or a plurality of rows. The red recording print head has a central wavelength of emission of 660 nm and a resolving power of three.
The LED print head 30a has 00 dpi and the number of pixels is 5120. GaAlAs in LED array
The element made of GaAsP or GaAsP has a high luminous efficiency, and particularly the element having a steep emission wavelength peak at 650 to 680 nm can selectively and efficiently expose the red light-sensitive layer of the silver halide color light-sensitive material. It is possible. Further, high-speed on / off control is possible on the order of several nsec of light emission time of the element, which is particularly suitable for strict exposure time control.

The green exposure print head 30b and the blue recording print head 30c are vacuum fluorescent print heads (Vacuum Fluoresc) which can be easily separated by color filters with relatively high brightness and high speed response.
ent Print Head and hereinafter referred to as VFPH). VFPH is one type of phosphor material that emits light in a wide spectral range from blue to green.
The blue and green light-sensitive layers of the silver halide color light-sensitive material can be selectively made to emit light in combination with a color filter. Further, since the light emission efficiency is relatively high and the temperature change at the time of light emission is small, the light emission peak transition due to the temperature change is small, and the exposure efficiency to the silver halide photosensitive material having high wavelength selectivity is stable.

The print head 30b for green recording has a position shift corresponding to the print head interval and a position shift in the print element array direction of the print head in the conveying direction of the color printing paper 20 (direction of arrow in FIG. 7). Correction of these positional deviations is performed by controlling from the CPU 2. The print head 30a for red exposure and the print head 30c for blue recording are also CP.
It is controlled by U2 to correct the positional deviation. The output is synchronized by using the system clock and dividing the frequency according to the carrier speed to generate a light emission timing signal.

The photographic printing paper 20 is not limited to the roll shape, and may be cut paper. The means for moving the photographic printing paper 20 may be another means such as a means for transporting the photographic printing paper 20 on a belt. The photographic paper may be fixed and the print head may be moved, or both may be moved. The conveying direction and the recording element arrangement direction may be oblique. Although the color photographic printing paper 20 is used as the exposure photosensitive material, any so-called silver halide photosensitive material can be applied. Further, the print head may be one that matches the color sensitivity of the light-sensitive material, and in the case of color, three-color control in which light sources for three colors are arranged may be used.

The exposure amount correction circuit 100 is a circuit for correcting variations in light emission for each recording element of the array print head, and the correction amount obtained by the above-described method is sent and recorded. The exposure amount correction circuit 100 corrects the image data by sequentially converting the image data sent from the DRAM into the exposure amount and then multiplying the image data of each image by the correction amount of the corresponding recording element. , To the data output unit 210.

FIG. 8 is a block diagram showing the main structure of the drive circuit.

The image data output from the exposure amount correction circuit 100 is received by the drive circuit 200 having a register for each line. The drive circuit 200 causes the print head 30a to emit light. Drive circuit 200
As shown in FIG. 8, it comprises a data output section 210, a light emission control section 220, a shift register 230, a latch 240, and a gate 250.

The data output unit 210 sets and starts a count initial value for counting pixels for one line, and based on the count value, 12 bits × 1 line of image data is stored in a line memory (not shown). Write. When the data output unit 210 finishes writing the image data of the first line to the line memory, MSB to LSB of the image bit data of the first line are sequentially output from the line memory and transferred to the shift register 230. on the other hand,
The data output unit 210 writes the image data of the second line in the line memory. As described above, while the image data of the current line is being transferred to the shift register 230, the image data of the next line is expanded and written in the other line memory repeatedly. The image data of can be continuously output by the expansion process without stagnation in time.

The light emission control unit 220 adjusts the light emission characteristics of each print head by controlling the generation timing of the enable signal. Specifically, it is set to 1 for each color.
When the image data is input with a 2-bit digital value, it is converted into serial digital image data for one line pixel corresponding to each light emitting element, and a set pulse for transferring the image bit data to the latch 240. When,
The enable signal for controlling the light emission time is generated and output to the print head 30. Here, the image bit data is specific bit data of the image data.

The light emission control section 220 comprises a gate circuit including an enable signal and set pulse generating circuit (not shown) and a counter (not shown), and a CPU, and counts the transfer time of the image bit data. And outputs a count-up signal to the set pulse generation circuit, the set pulse generation circuit outputs image data to the print head 30.
The set pulse is generated and output to the print head 30a at the timing when the transfer to a is completed, and the set pulse is also output to the enable signal generation circuit.

On the other hand, when the light emission control section 220 counts the enable time corresponding to the exposure amount previously assigned to each of the 12 bits and outputs it to the enable signal generating circuit, the enable signal generating circuit indicates the exposure amount. 12
An enable signal having an enable time corresponding to the bit is generated from the MSB (most significant bit) of the bit in response to the generation of the set pulse, and is output to the print head 30a. Then, the CPU 2 receives this and controls the counter to generate the next set pulse. By repeating such a series of operations, the set pulse, the enable signal, and the image bit data are sequentially timed from the MSB to the LSB for each line, and the print head 30a is sequentially timed.
Is output to.

The data output unit 210 first transfers MSB (most significant bit) data to the shift register 230 as image bit data for one line, and then the light emission control unit 22.
For 0, the set pulse is input to the latch 240, and the data of the MSB is latched for one line in the latch 240 in synchronization with the set pulse. Then, the light-emission control unit 220 inputs an enable signal corresponding to the gradation to the drive circuit 200, so that each light-emitting element of the light-emitting elements arranged in an array of one column or a plurality of columns in the time width section of the enable signal. Drive control is performed to emit light according to the latched image data. That is, the latched data is "1"
The drive circuit 200 selectively sends a drive signal to the print head 30a to cause the element which is a light emitting element to emit light for the time width of the enable signal. The irradiation light forms an image on the printing paper 20 via the SELFOC lens array 35 to form a latent image. By performing such a process sequentially from MSB to LSB (least significant bit) for all bits, recording for one line is completed. The order of bits may start from LSB or may be another order, and is not limited. Although one color has been described above, similar control is performed for all three colors.

VFPH having emission characteristics in green and blue components
In the lower part of the SELFOC lens array 35, green and blue color separation filters (not shown) are arranged. The drive circuit 200 conveys the image data transferred for each color to the photographic printing paper 20. Since the three print heads 30 perform recording control while sequentially shifting the exposure timing so as to perform recording at a predetermined position of
A proper color image can be recorded. As a filter for the green light source, a yellow filter may be used instead of the green filter. The drive circuit 200 performs recording control on the print head 30a so that recording of one line is performed by 50% or more while the photographic printing paper 20 is being moved by the support drum 1, so that recorded images between lines continue. As a result, unevenness can be prevented and smooth continuous gradation can be realized by density modulation.

FIG. 9 is a timing chart showing the operation of the drive circuit.

CLOCK is a transfer clock of image data, and DAT is synchronized with the falling edge of CLOCK.
A is a pixel obtained by expanding one pixel transferred from the data output unit 210 to the shift register 230 into a density value of 12 bits. The / LOAD signal indicates the output timing of the set pulse. Shift register 23
It is shown that a set pulse is output to the latch 240 every time bit transfer to 0 is performed. The light emission timing is given and is given from the light emission control unit 220 to the gate 250. STB indicates the light emission timing of the enable signal, and indicates that the enable signal is generated for each bit transfer to the shift register 230. Light is emitted during the ON time, and this light emission time is controlled by setting DSW to an arbitrary value, and is a time obtained by multiplying the cycle 1 / fclock.

The exposure of multi-valued image data can be achieved by decomposing the image data of one pixel bit by bit and exposing a plurality of times. For example, when an output level of 8 bits is desired, the DATA value is read into the shift register 230 in order from the upper bit, and DSWn (n is the number of times of light emission required to record one pixel) corresponding to the bit is stored in the ROM or the like. It can be achieved by reading from, and exposing the lower bit DATA in order.

MSB to LSB for one light emitting element
The maximum exposure time is the maximum exposure time and the maximum density is given when the latch data, that is, the bit value for all the enable signals up to 1 is "1" and light emission is caused. The interval time between enable signals is set to 48 μsec. Similar control is performed for the other print heads 30b and 30c.

[0072]

According to the first aspect of the present invention, by providing the above configuration, the pixel position of the patch image density data and the arrayed print head are affected by the defocus of the beam spot and the halation caused by the beam spot. Since it is possible to accurately adjust the position of each light emitting element and obtain a correction amount for each light emitting element, it is possible to accurately correct unevenness in density.

According to the sixth aspect of the present invention, since the above configuration is provided, it is unlikely to be affected by drooping of the recorded image due to focus shift or scattering, so that the peak detection for each recording element on the recorded image becomes accurate. .

[0074] The invention according to claim 2 and 7 is provided with the above-described configuration, simple algorithm of the peak detector for recording image has a periodicity, speed, can higher accuracy.

According to the third and eighth aspects of the present invention, since the exposure amount calculation can be performed with high accuracy by providing the above configuration, the correction amount becomes accurate.

[0076]

The inventions described in claims 4 and 9 are more effective by having the above-mentioned configuration.

The invention described in claims 5 and 10 can obtain a further great effect by having the above-mentioned structure.

[Brief description of drawings]

FIG. 1 is a flowchart showing a method of correcting an exposure amount of a print head according to this embodiment.

FIG. 2 is a schematic diagram showing a patch image for exposure amount correction.

FIG. 3 is a graph showing reproduction density with respect to DSW of one light emitting element.

FIG. 4 is a graph showing sampled density data.

FIG. 5 is a schematic diagram showing a method of detecting a pixel position from density data.

FIG. 6 is a block diagram showing a schematic configuration showing an example of an image forming apparatus.

FIG. 7 is a block diagram of a printhead control circuit.

FIG. 8 is a block diagram showing a main configuration of a drive circuit.

FIG. 9 is a timing chart showing the operation of the drive circuit.

FIG. 10 is a schematic view showing print heads arranged in an array.

[Explanation of symbols]

2 CPU 3 R, G, B data distributor 4, 5, 6 DRAM 30a to 30c array print head 100 Exposure correction circuit 200 drive circuit 210 Data output section 220 Light emission control unit 230 shift register 240 latch 250 gates

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Claims (10)

(57) [Claims] 1. An image is recorded on a photosensitive material based on image data by using a print head in which a plurality of recording elements are arranged in an array, and the density of the image is measured,
In the image forming method of obtaining the correction amount of the recording characteristic of each recording element and recording the image using the correction amount,
At least every other element in the array direction of the recording elements is described above.
It is an image recorded by driving the recording element , and in determining the correction amount, the density measurement data for each recording element is converted into exposure amount data using the characteristic curve of the photosensitive material, and then the correction amount is calculated. An image forming method characterized by calculating. 2. The image forming method according to claim 1, wherein the image is a periodic image having a constant period in the recording element array direction. 3. When obtaining the correction amount, the correction amount is calculated after converting the density measurement data of at least two positions at different positions in the printing element array direction for each printing element into exposure amount data, respectively. The image forming method according to claim 1 or 2. 4. The light-sensitive material is a silver halide light-sensitive material.
It is any one of Claim 1-Claim 3 characterized by being
The image forming method according to item 1 . 5. The light-sensitive material has a reflective support.
The image forming method according to claim 4, wherein 6. A printer having a plurality of recording elements arranged in an array.
The print head and print head are based on image data.
Print head control means for controlling the drive based on
Conveying means for conveying a lint head, a recording medium, or both
In the image forming apparatus having the
Control means controls the print head based on image data.
The image forming mode to control and the arrangement direction of the recording elements
Photosensitive material by driving at least every other recording element
By recording the image on the
Correction mode that calculates the correction amount of the recording characteristics of each recording element
And to obtain the correction amount, for each recording element
Density measurement data using the characteristic curve of the photosensitive material
Calculate the correction amount after converting each to exposure amount data
An image forming apparatus characterized by the above. 7. The image has a constant period in the recording element array direction.
7. A periodic image having
The image forming apparatus. 8. When determining the correction amount, each recording element
At least at different positions in the recording element array direction for each child
Converts the density measurement data from two locations into exposure data
7. The correction amount is calculated after the calculation,
The image forming apparatus according to claim 7 . 9. The photosensitive material is a silver halide photosensitive material.
9. Any one of claims 6 to 8 characterized in that
The image forming apparatus according to item 1 . 10. The photosensitive material has a reflective support.
The image forming apparatus according to claim 9, wherein: