JPH10185684A - Solid scanning type optical writing device, and method of measuring light quantity thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely measure the output light quantity of each optical chip of a solid scanning type optical writing device by a simple control. SOLUTION: An optical writing head 20 controls ON/OFF of a light by a PLZT optical, shutter module 30 formed of a number of optical shutter chips arranged in a main scanning direction X. The light quantity of each optical shutter chip is controlled by intermittently lighting the optical shutter chips so that at least the adjacent optical shutter chips are not lighted while moving a photoelectric converting sensor 72 having a slit 73a in the main scanning direction at a constant speed. For example, the optical shutter chips of odd numbers are lighted in forward going of the sensor 72 to measure the light quantity, and those of even numbers are lighted in coming to measure the light quantity in return movement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state scanning optical writing apparatus for writing an image (latent image) on a photoreceptor by using a PLZT optical shutter array, an LED array, and the like, and a method for measuring the amount of light.

[0002]

2. Description of the Related Art Conventionally, in order to form an image (latent image) on a photographic paper, a silver halide film, or an electrophotographic photoreceptor using a silver halide photosensitive material, an optical shutter chip such as PLZT is used for each pixel. There have been provided various optical writing devices for controlling on / off of light and for controlling on / off of LED chips. And
In this type of solid-state scanning optical writing device, it is necessary to measure the light amount of each optical chip and obtain light amount correction based on the measured value in order to obtain an even image.

Conventionally, as a method of measuring the light amount of each optical chip, Japanese Patent Application Laid-Open No. 63-272568 discloses a method in which an LED chip is sequentially turned on in a main scanning direction and a light amount detection sensor is opposed to the LED chip by a predetermined distance. A method of moving in a state is disclosed. However, when the LED chips are sequentially turned on in this way, it is necessary to accurately synchronize the scanning speed of the LED chips with the moving speed of the sensor, so that fine adjustment of the start position is required, and an encoder and an accurate feed mechanism are required. Becomes In addition, in the sequential lighting method, the influence of the amount of light leaking from an adjacent optical chip or the like is not reflected in the measurement, and the image unevenness is not sufficiently eliminated when the solid image is reproduced.

Further, in order to realize multi-tone image reproduction, it is necessary to accurately measure the output light amount characteristics of each optical chip. However, as disclosed in Japanese Patent Application Laid-Open No. 61-150286, etc., it is not sufficient to measure the light amount only at the time of ON.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a light quantity measuring method and a solid-state scanning optical writing device capable of accurately measuring the output light quantity of each optical chip by simple control. Still another object of the present invention is to provide a light quantity measuring method capable of measuring the output light quantity characteristics of each optical chip in correspondence with image reproduction with multiple gradations.

Another object of the present invention is to provide a solid-scanning optical writing apparatus which is of a full-color type and can accurately measure the output light quantity of each light source color by simple control.

In order to achieve the above object, the present invention relates to a solid-state scanning optical writing device for controlling on / off of a plurality of optical chips arranged in a main scanning direction based on image data, wherein at least the optical chips are provided. There is provided control means for thinning out the light so that the adjacent optical chips do not light up. Then, a light amount detection sensor having a light receiving slit is moved in the main scanning direction so as to face the optical chip, and the light chips are thinned and lit during this movement, and the light amount of each optical chip is calculated based on the output of the light amount detection sensor. I do.

In the present invention, since the optical chips are thinned and lighted and the output light amount is measured, the light chip is simply moved at a constant speed to identify the optical chip in relation to the thinned light pattern (address). ) To measure the amount of light. Moreover, there is no need to accurately synchronize the scanning speed of the optical chip with the moving speed of the sensor, and control is easy. In addition, since the adjacent optical chip is not turned on, the amount of light leaking from the lit optical chip can be measured from the optical chip in the off state, and the actual amount of light can be accurately calculated. Is effective in eliminating image unevenness.

In particular, if each optical chip is turned on at a predetermined frequency and duty, and the light amount of each optical chip is measured a plurality of times and the peak value is used as the light amount of the optical chip, each optical chip can be scanned in one scan. Can be measured, and the optical chip can be accurately identified. Further, it is also possible to detect an abnormality in the optical writing device or the measuring device from the measured peak value interval.

In the present invention, it is preferable that the light chips are thinned and lighted at substantially the same frequency and duty when measuring the amount of light as during image formation. By performing the light quantity measurement under substantially the same conditions as the actual image formation, the measurement result becomes close to the actual driving, so that the light quantity correction becomes more accurate. Furthermore, if each optical chip is repeatedly turned on under a plurality of driving conditions (duty, voltage, current, etc.) having different output light amounts, the output light amount characteristics of each optical chip can be obtained more accurately, and multi-gradation can be achieved. It is effective for image reproduction.

Further, if the optical writing device is a full-color compatible type in which a plurality of light source colors are switched at a high speed to light an optical chip, driving conditions (duty, voltage, current, etc.) for each optical chip corresponding to each light source color. , It is possible to accurately measure the amount of light for each light source color. In this case, switching of the light source colors is performed at a lower speed during light quantity measurement than at the time of image formation, and by turning on each optical chip a plurality of times for each light source color, multi-step measurement of three colors can be performed in one scan. In addition, the output light amount characteristics of each optical chip can be obtained more accurately, which is effective for image reproduction with multiple gradations.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a solid-state scanning optical writing device and a method for measuring the amount of light according to the present invention will be described below with reference to the accompanying drawings.

(Optical Writing Head) FIG. 1 shows an optical writing head 20 for writing a full-color image on photographic paper using a silver halide photosensitive material. The optical writing head 20 generally includes a halogen lamp 21, a heat insulating filter 22, a color correction filter 23, a diffusion tube 24, an RGB filter 25, an optical fiber array 26, a slit plate 27, an optical shutter module 30, an imaging lens array 35, It is constituted by dustproof glass 36.

The light emitted from the halogen lamp 21 is
The heat rays are cut by the heat-insulating filter 22 and the light quality is adjusted by the color correction filter 23 so as to match the spectral sensitivity characteristics of the photographic paper. The diffusion tube 24 is for improving the light use efficiency and reducing the light amount unevenness. The RGB filter 25 is rotationally driven in synchronization with writing by a PLZT shutter chip described below, and changes the passing color for each line.

The optical fiber array 26 is composed of a large number of optical fibers.
They face each other via the GB filter 25. The other ends 26b are arranged in the main scanning direction indicated by the arrow X, and emit light in a line. Slit end faces 27a, 27a of slit plate 27
Is mirror-finished, and guides light emitted from the optical fiber array 26 to the optical shutter module 30 efficiently. Further, a heater (not shown) for maintaining the PLZT shutter chip at a constant temperature is provided on the slit plate 27, and the temperature is determined based on a detection result of a temperature detecting element (not shown) provided on the module 30. Control is performed.

The optical shutter module 30 has a slit-shaped opening in a ceramic substrate or a PLZT
Is provided, and a driver IC is provided side by side with the shutter chip. Each of the shutter chips is driven only by a driver IC corresponding to a predetermined pixel. A polarizer 33 and an analyzer 34 are provided before and after the module 30. As is well known, PLZT is a light-transmitting ceramic having an electro-optical effect having a large Kerr constant, and light linearly polarized by the polarizer 33 generates an electric field generated by applying a voltage to a shutter chip. The rotation of the polarization plane is caused by the on / off of the
The light emitted from 4 is turned on / off.

The light emitted from the analyzer 34 passes through the imaging lens array 35 and the dust-proof glass 36 to form an image on photographic paper to form a latent image. The printing paper is transported at a constant speed in a direction (sub-scanning direction) orthogonal to the main scanning direction X.

(Light Amount Measuring Device and Measuring Method) FIG. 2 shows a measuring device 70 for measuring the light amount of each optical shutter chip of the optical writing head 20.

The measuring device 70 includes a photoelectric conversion sensor 72.
And a measurement unit 71 having a tool microscope 77 slidably mounted on a guide rod 76. The guide bar 76 is installed in parallel with the main scanning direction (the direction of the arrow X) by the optical shutter module 30, and the measuring unit 71 reciprocates at a constant speed in the direction of the arrow X with the sensor 72 positioned directly above the optical shutter chip. Moving. See Figure 1
As shown in FIG. 1, a male screw is formed on the outer peripheral surface of one guide rod 76a, and a nut (not shown) provided on the measuring unit 71 is screwed to the male screw. Therefore, the measurement unit 71 reciprocates with the forward / reverse rotation of the guide rod 76a.

On the incident side of the sensor 72, a slit plate 73 and a light diffusion plate 74 are provided. The slit plate 73 is 25 to 400% (preferably 50 to 20%) of the width of one pixel.
(0%), and has a slit 73a having a frontage width, and is located on the focal plane F of the imaging lens array 35. The sensor 72 whose spectral sensitivity characteristic is substantially equal to or broader than the spectral sensitivity characteristic of the recording medium is used.

The tool microscope 77 is provided integrally with the CCD camera 78. The optical shutter chip is photographed by a CCD camera 78 via a tool microscope 77 and displayed on a monitor television 79. The measurer looks at the image on the monitor television 79 and finely adjusts (focuses and positions) the position of the optical writing head 20 at both ends of the optical shutter chip. That is, the optical writing head 20 is attached to the sensor 72 by a mounting table (not shown) so that the height, inclination, distance from the sensor 72, and the like can be adjusted.

The light quantity measuring device 70 and the optical writing head 20 having the above-described configurations are controlled by a sequencer, and the reciprocating motion of the measuring unit 71 and the timing of light quantity measurement are controlled. The drive mode (drive frequency, lighting duty, blinking data) of the optical writing head 20 is programmed in advance.
Driven by The measuring device 70 is configured to obtain an integrated value of the light amount of each optical shutter chip in synchronization with the driving. Normally, it is set so that sampling and holding are performed several tens of times per chip depending on the relationship between the driving frequency and the driving speed of the sensor 72. The output of the sensor 72 is A /
It is D-converted and transferred to the control unit to perform necessary processing.

The driving mode of the optical writing head 20 is set according to the driving conditions of the actual machine. Optical writing head 20 is 4
A printing density of 00 dpi (the number of dots per inch) and a case where the printer is mounted on a printer driven at 1 kHz (63.5 mm / s) will be described as an example.

First, the odd-numbered light shutter chips are repeatedly turned on, and the sensor 72 is moved forward from an initial position outside the scanning area of the light shutter chips. Then, the sensor output of one line section (1 mm / s) is integrated, the integrated value is sampled / held, A / D converted, and taken into the control unit. When the sensor 72 is moved at a speed of 1 mm / s, in the case of 400 dpi (63.5 μm), sampling / holding is performed 63.5 times per chip (one pixel). After moving the sensor 72 slightly longer than the main scanning length, the control unit stops capturing data and moves the sensor 72 to the initial position. Next, while turning on the even-numbered optical shutter chips, the amount of light is measured in the same manner as described above, and data is fetched. This completes the light quantity measurement of all the optical shutter chips. Of course, the light quantity measurement of the even-numbered optical shutter chips may be performed when the sensor 72 is moved backward, which is more efficient.

An effective measuring method in consideration of light quantity correction is to obtain measured values at four different light quantities for each optical shutter chip. The lighting duty is set to high, medium, and low, and the optical writing head 20 is operated in a drive mode in which light is turned off (off). In this case, sampling / holding per optical shutter chip is about 16 times, and a measured value at four light levels can be obtained by one scan. Of course, 4
The amount of light at each stage may be measured separately for two to four scans.
It is not necessary to be limited to the four-step light quantity measurement.

Sampling per optical shutter chip /
The number of holds can be increased by lowering the moving speed of the sensor 72 or increasing the driving frequency. Although there is no change in the amount of light due to the driving frequency, it is within a practically acceptable level. If the correlation between the driving frequency and the change in the light amount is clearly understood in advance, it is possible to cope with the problem by introducing a correction coefficient.

When the optical writing head 20 is compatible with color printing, it is necessary to perform measurement separately for each light source color (R, G, B). Therefore, the above-described measurement process is performed three times in total for each color while switching the RGB filters 25. The control unit calculates the identification (address) of the optical shutter chip and calculates the maximum value and the minimum value from the peak value of the acquired measurement data. The light quantity of each optical shutter chip is calculated from these values, the measured light quantity at four points is approximated by a cubic curve, and the correction coefficient for each light quantity value (for example, 0-255 steps) is determined.

Next, the principle of light quantity measurement will be described with reference to FIGS. First, the drive signal A is applied to the odd-numbered optical shutter chips. The driving signal A has a frequency and a duty that are the same or close to the driving conditions in the actual machine. An optical output B is emitted from each optical shutter chip, and the same waveform is output from the sensor 72 moving forward in the main scanning direction X. This output is integrated, sampled / held at the end of the ON period, and A / D converted.

In the light quantity measurement, the slit 73a having substantially the same size as the chip width is scanned in the main scanning direction X at a speed at which lighting is performed a plurality of times per chip, so that the A / D converted output is shown in FIG. As shown. The maximum light amount is obtained when the sensor 72 faces the optical shutter chip 31, and the minimum light amount is obtained between the chips 31. Therefore, the chip position can be identified (addressed) by detecting the peak of the output light quantity. The minimum light amount between the chips 31 varies depending on the MTF of the imaging lens, the slit width, and the like. The minimum light quantity position can be identified by performing peak detection in the same manner as the maximum light quantity, but a value at a half point between the maximum light quantities can also be adopted.

Next, the drive signal A is applied to even-numbered optical shutter chips, and the light quantity is measured in the same manner as described above while the sensor 72 is moved backward. By superimposing the measurement results on the odd-numbered measurement results, the output light amount characteristics of all the chips 31 are determined.

In the above light quantity measurement, the chip position is calculated from the output light quantity, so that the encoder and sensor 7
The detection of the initial position of No. 2 is unnecessary. In the present embodiment, the on-light amount and the off-time light amount are measured simultaneously, and the drive signal is configured to measure the on-period and the off-period alternately.

The off-time light amount (leakage light amount) also integrates the sensor output during the off-period, and performs A / D conversion by sampling / holding at the end of the off-period, similarly to the on-time light amount. Any identification of the chip position is possible by peak detection as in the case of the on-state, but since the output signal is weak, the off-time light amount at the same time as the on-time peak is used. Regarding the determination of the minimum light quantity at the time of ON, it is preferable to experimentally correct by the following equation.

Specific chip light quantity = maximum light quantity of specific chip +
(Sneak light amount-leak light amount) x correction coefficient

The correction coefficient is determined by the lighting pattern and the slit 73.
It is 0.2 to 1.0 depending on the width dimension of a. Further, in the case of a line / dot screen, it is sufficient to perform correction using only the peak value of the specific optical chip, and in the case of reproduction of one dot (specific line / dot screen), the correction of the specific optical chip is performed. It is more preferable to correct only the peak value. Although the measurement method has been described with an example in which the light is turned on for each of the odd-numbered and even-numbered numbers, various lighting patterns can be considered.

Here, the light quantity integration circuit 80 is shown in FIG.
The timing chart is shown in FIG. The light quantity integration circuit 80 has three types of duty, high, medium, and low, and off.
It is for measuring the amount of light in stages, and is composed of four systems (only two systems are shown in FIG. 5). Sensor 72
Is input to each integrator 82 via a polarity inversion amplifier 81, and is further input to a sample hold amplifier 84.
A / D conversion is performed through The optical voltage signal is integrated by the integrator 82 while each analog switch 83 is turned on by the signals AS-1 to AS-4, and is held by the sample and hold amplifier 84 at the falling timing of the signals SH-1 to SH-4. It is converted to a digital signal by a / D converter.

According to the integration circuit 80, four light levels can be measured in one scan. By calculating an approximate expression of the light amount characteristic based on these measured values and creating a light amount correction table, it is possible to perform a good light amount correction for gradation reproduction.

(Configuration and Operation of Driver IC) Next, a driver IC for driving the optical writing head 20 when measuring the light amount by the light amount measuring device 70 will be described. The thinning-out lighting performed at the time of measuring the light quantity of the optical shutter chip can be realized by transferring necessary data from the CPU and driving the optical writing head 20, but the function can be added to the driver IC.

FIG. 7 shows a configuration when a driver IC for reproducing a binary image is used. This driver IC
60 uses n ICs connected by a ladder chain. Each IC is configured to drive 64 dots, and a shift register 61, a latch circuit 62, a gate circuit 63, a level shift circuit 64, It comprises a driver circuit 65.

The image data DATA (A) and (B) are based on a shift clock signal S-CLK based on a shift signal R / L.
, And is transferred to the shift register 61 and latched by the latch circuit 62 with the strobe signal STB. When the gate signal GATE is input to the gate circuit 63, the signal D ₁
To D ₆₄ is the driver circuit 6 via the level shift circuit 64
5 is transferred. The drive voltage Vd is applied to the driver circuit 65, and the signal D ₁ from the level shift circuit 64 is applied.
Output HV ₁ ~HV ₆₄ based on to D ₆₄ is applied to the light shutter elements.

In the driver IC 60, when the light quantity measurement mode is commanded, the data signal DATA is transferred to the shift register 61 in synchronization with the shift clock signal S-CLK, and is latched by the latch circuit 62 with the strobe signal STB. When the gate signal GATE is driven with a predetermined duty, the optical shutter chip can be operated with a predetermined light amount. The thinning lighting is performed by the data signal D
This can be realized by operating the ATA and a signal obtained by dividing the frequency of the shift clock signal S-CLK under AND conditions. 1/2
If the frequency is divided, it becomes 1 on / 1 off. The signal for thinning-out lighting is a repetitive signal. If a gate signal GATE having a plurality of duties is prepared, the light quantity measurement mode can be executed without a printer controller. If the optical shutter chip is divided into odd rows and even rows, one row of DAs
After setting TA to “H” and transferring DATA equal to or more than the number of chips for at least one row to the shift register 61, latching it with the strobe signal STB, and performing the above control,
1 ON / 1 OFF can be realized more easily. Further, a TEST input terminal is provided in the gate circuit 63 so that the gate circuit 63
If a predetermined duty signal is transferred to this terminal by adding a function of forcibly turning on the power supply, the light quantity measurement mode can be easily executed.

More specifically, as shown in FIGS. 8 and 9,
The basic clock signal CLK oscillated from the oscillator 66 is converted to an appropriate frequency by the frequency divider 67, and becomes a shift clock signal S-CLK and a counter count signal. The line cycle counter 68 counts a line cycle and generates a strobe signal STB. That is, the one-shot multivibrator is operated by counting up to generate the strobe signal STB, and at the same time, the counter 68 is reset, so that the strobe signal STB is output at a constant cycle. The duty can be changed by making the specified value of the counter 68 selectable. The shift amount counter 69 determines the number of data to be transferred to the shift register 61. In order to generate an output during counting, the shift amount counter 69 is operated under the AND condition with the clock signal CLK to generate the shift clock signal S-CLK.

The data signal DATA is the clock signal CL
Various patterns can be generated from K.
If a signal obtained by dividing the frequency by 使用 is used, a signal for thinning-out lighting of 1 on / 1 off can be generated. Other patterns can be generated by a simple logic circuit. In a configuration in which the optical shutter chip is divided into an odd-numbered column and an even-numbered column, the shift amount counter 69 is not necessary, and the circuit is further simplified. That is,
What is necessary is just to make the data signal DATA always "H" and continuously output the shift clock signal S-CLK.

(Color Printer) FIG. 10 shows a schematic configuration of a color printer for photographic printing. This color printer comprises a photographic paper storage unit 1, an image forming unit 2, and a processing unit 3. The printing paper 4 is accommodated in the accommodation unit 1 in a roll shape. The optical writing head 20 shown in FIG.
The measuring unit 71 shown in FIG.
7, the CCD camera 78 is omitted). Further, the image forming section 2 is provided with a pair of transport rollers 5, 6, 7 for the photographic paper 4, a cutter 8 and transport guide plates 11, 12.

The photographic paper 4 is introduced into the image forming unit 2 from the pair of transport rollers 5 with the photosensitive surface facing downward, and when the photographic paper 4 is fed by a predetermined length, the rotation of the pair of rollers 5 is stopped and the cutter 8 is stopped.
It is cut by operating. The cut photographic paper 4 is conveyed at a constant speed by the roller pairs 6 and 7.
When the printing paper 4 passes over the optical writing head 20, the printing paper 4 is exposed through an opening formed in the guide plate 11 to form an image (latent image).
Is formed. The photographic paper 4 after the exposure is developed and dried in the processing unit 3 and discharged onto the tray 15.

The photographic paper 4 is conveyed to the exposure section so that the start of writing by the optical writing head 20 and the start position of image writing on the photographic paper 4 are synchronized, and during the writing period, is continuously conveyed at a predetermined speed. You. However, the transport in the exposure unit may be intermittently performed at a pitch corresponding to the density in the sub-scanning direction, instead of being continuous.

If the cutting of the photographic paper 4 is performed during exposure, it is likely to cause a synchronization shift. In order to eliminate such a problem, a configuration is adopted in which the photographic paper 4 is cut by bending it by an appropriate amount before exposure, or the exposure is started after the transport path is slightly longer but cut straight. Is preferred. When the photographic paper is in the form of a roll, it is necessary to turn off the light source lamp 21 or to shield the optical writing head 20 from light with a mechanical shutter so as not to be exposed at the time of cutting.

As shown in FIG. 11, the measuring unit 71 is installed at a position facing the optical writing head 20 so as to be able to reciprocate in the main scanning direction X with forward and reverse rotation of the driving guide bar 76a. The measuring unit 71 measures the light quantity of each optical shutter chip of the optical writing head 20 as described above before exposing the photographic paper 4 to light. The measuring unit 71 is retracted outside the conveyance path of the photographic paper 4 so as not to interfere with the photographic paper 4 being conveyed except during the light quantity measurement (see a two-dot chain line in FIG. 11).

The guide plate 11 is set so that the guide surface 11 'coincides with the focus surface F of the optical writing head 20 (see FIG. 12A). Absent. The conveying roller pairs 6 and 7 are controlled at a constant speed by a pulse motor (not shown) so as to make the sub-scanning speed constant. The upper guide plate 12 is for preventing the photographic paper from floating, and is configured to be pressed against the photographic paper by its own weight or by a spring or the like. Although the slit plate 73 provided in the measurement unit 71 is set to the same plane as the focus plane F, as described above, the slit plate 73 is evacuated from the photographic paper transport path except when measuring the light amount.

At the time of measuring the amount of light, the optical writing head 20
The light emitted from the sensor enters the sensor 72 through the openings of the guide plates 11 and 12. The guide plate 11 does not need to be provided with an opening if the whole or the light passage portion is formed of a light-transmitting material such as glass or acrylic. Eliminating the opening improves the guide function of the photographic paper. The upper guide plate 12 may be configured to be retracted from the guide position when measuring the amount of light without providing an opening.

On the other hand, as shown in FIG. 12B, a lens 75 may be interposed between the imaging lens array 35 and the slit plate 73. By arranging the lens 75, the measurement unit 71 can be separated from the focus plane F, and it is not necessary to evacuate the measurement unit 71 during exposure, which contributes to downsizing of the apparatus. In this case, the upper guide plate 12 can be formed of a translucent material.

In the present color printer, the RGB filter 25 of the optical writing head 20 is rotated to switch the light source color at a high speed, and the R, B, and G images are PL-lined for each line.
Writing is performed by turning on / off the ZT optical shutter chip. The printer is usually turned on by a timer, and controls the temperature of the developer. During this warm-up period, the light amount measurement of the optical shutter chip and its correction (calibration) are performed. As described above, the calibration is a step of driving the optical writing head 20 under substantially the same conditions as the exposure, and performing light amount correction based on the output light amount, and obtains a good gradation image without unevenness.

In the case of a full-color device, first, only the odd-numbered chips are driven at a specified frequency (determined by the pixel density in the sub-scanning direction) and the amount of light (duty or intensity), and the light source color is switched in synchronization therewith. At the same time, measuring unit 7
1 is moved forward, and the RGB light amounts and the light amounts at a plurality of gradations are measured. At the time of the backward movement, similarly, the RGB light amounts and the light amounts at a plurality of gradations of the even-numbered chips are measured.

In order to properly perform light quantity correction, measurement in four steps including the off light quantity (leakage light quantity) is effective, and the light source color switching speed is reduced to one-fourth (１ ／) the number of measurement steps in actual use. The measurement is performed at four light levels per color. That is, 1
The amount of light at 12 points (RGB × 4) per chip is measured in one scan. After sampling / holding the integrated value of the optical voltage output of the sensor 72 and performing A / D conversion, the control unit calculates an approximate curve of the output light amount characteristic from the four light amount values and performs light amount correction. The light quantity correction is performed based on the optical shutter chip having the smallest measured light quantity. The content of the light amount correction is stored in a memory element for a lookup table (for example, a flash ROM).

Note that the light source color switching speed may be substantially the same as that in actual use. In this case, the drive frequency is increased and a plurality of light quantity measurements are performed for each color. If the driving frequency is the same as that in the actual use, a plurality of light amounts may be measured by a plurality of scans.

In this embodiment, the measurement of the light amounts of all the chips is completed in one reciprocating scan. However, it is also possible to separately measure each gradation or each light source color. In this case, although the number of scans is increased, it is slightly disadvantageous in terms of time, but has advantages such as simplification of the light amount integration circuit.

The number of gradations in the light quantity measurement depends on the output characteristics of the optical shutter chip. If the linearity is good, practical use is possible even with two-point measurement. Furthermore, if the amount of leakage light is zero, one-point measurement is possible. However, normally, the output characteristics of the optical shutter chip do not match the ideal linearity, so that any chip can be measured by measuring at four points. As for the light source color, if the output characteristics for each color are the same, correction can be performed by measuring one color. In addition, even if there is a slight difference in characteristics, the correction may be performed by measuring one color of green or white as long as it is acceptable on the image.

The optical shutter chip of the PLZT changes its spectral transmission characteristics due to the driving voltage. Therefore, it is preferable to set the same drive voltage waveform at the time of light quantity measurement and at the time of actual shooting. One of the means is to measure the amount of light by driving the other colors (red and green) with the same voltage while using the optimum voltage at the time of blue exposure as a driving voltage. Another means is to measure the amount of light by driving with the optimum voltage of each light source color. In the present embodiment, it is necessary to change the drive voltage at a high speed, and the waveform of the drive voltage may be distorted. Therefore, the measurement and the actual photographing are performed using (the same) power supplies having the same characteristics. Is preferred.

According to the light quantity measuring method described above, FIG.
As described with reference to above, the number of samplings between the peaks is counted in order to determine the address from the peak value of the output light amount without requiring a special device for determining the address of each optical shutter chip. By doing so, when the optical writing head 20 is used as an inspection device, it is possible to detect abnormalities (pitch errors, alignment errors, etc.) of the optical writing head 20. In addition, when the measurement unit 71 is mounted on an actual device, a movement failure of the measurement unit 71 can be detected. In this case, an abnormality is displayed / warned and the operation of the printer is stopped. Further, it is possible to correct the light amount corresponding to the deterioration of the optical shutter chip over time.

On the other hand, image data read by a film scanner is developed on a bit map memory of an image memory. The information on the bitmap memory is transferred to the driver of the optical shutter module 30 in a state where the input image data is corrected with reference to a look-up table storing the light amount correction content, and is switched at a predetermined speed. It is reproduced with the same light source color as the original image.

The measurement and correction of the light quantity can be executed at any time other than at the time of warming up the printer.

(Structure and Operation of Driver IC) FIGS. 13 and 14 show the structure and timing chart of the driver IC 40 for multi-value reproduction. The driver IC 40 includes n I
C is used continuously in a ladder chain. Each IC is configured to drive 64 dots, a 6-bit shift register 41, and a 6-bit latch circuit 42, 6
Bit comparator 43, 6-bit counter 44,
It comprises a gate circuit 45 and a driver circuit 46.

The image data DATA (A) and (B) are based on a shift clock signal S-CLK based on a shift signal R / L.
Is transferred to the shift register 41 in synchronism with the data, and is latched by the latch circuit 42 with the strobe signal STB. Thereby, the number of gradations of each pixel is set. Clock signal C
-CLK is counted by the counter 44, the comparator 43 compares the latched value with the counter value, and the gate circuit 45 stops the output when the two match. The counter 44 is cleared by the clear signal CL.

[0063] The driver circuit 46 are applied drive voltage Vd, so that the output HV ₁ ~HV ₆₄ based on the signal D ₁ to D ₆₄ from the gate circuit 45 is applied to the light shutter elements. That is, each pixel turns on the optical shutter chip for a time (pulse width) corresponding to the image data DATA.

The multi-value reproduction driver I having the above configuration
Even when the light quantity measurement mode is executed in C40, basically the same control as that of the above-described binary reproduction driver IC 60 is performed. The predetermined amount of light is specified by a data signal DATA (dip switch or the like), transferred to the shift register 41, latched by the strobe signal STB, a duty corresponding to the data signal DATA is generated by the comparator 43 or the like, and is specified by the gate signal GATE. Is operated at a predetermined light amount. Such a signal for thinning-out lighting is a repetitive signal and can be realized by a relatively simple circuit.

When the optical shutter chip is divided into an odd-numbered row and an even-numbered row, if one row of data is set to "H", the thinned-out lighting can be easily realized and the control is further simplified. . In order to change the light amount, the setting of a dip switch or the like may be changed.

(Other Embodiments) The optical writing device and the method for measuring the light amount thereof according to the present invention are not limited to the above-described embodiments, but can be variously modified within the scope of the invention. In particular, as a solid-scanning element used for optical writing, besides PLZT, an LED (Light Emitting
Diode), LCS (Liquid Crystal Shutter), DMD
(Deformable Mirror Device), FLD (Fluorescent
Device) can be used.

Further, the modulation of the optical shutter module in multi-gradation may be a method of modulating the pulse intensity in addition to the method of modulating the pulse width. Further, the present invention can be applied to an image writing device for a silver halide film or an electrophotographic photosensitive member or an image projection device on a display, in addition to an image writing device for photographic paper using a silver halide photosensitive material. It is.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an optical writing head used in a light quantity measuring method according to the present invention.

FIG. 2 is a schematic configuration diagram showing a light quantity measuring device.

FIG. 3 is a waveform diagram of an analog signal at the time of measuring the amount of light.

FIG. 4 is a waveform diagram of a digital signal at the time of light quantity measurement.

FIG. 5 is a block diagram of an integration circuit used for light quantity measurement.

FIG. 6 is a timing chart showing the operation of the integration circuit.

FIG. 7 is a block diagram showing a binary image reproduction driver IC.

FIG. 8 is a block diagram showing a circuit for generating a signal transferred to the binary image reproducing driver IC.

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

FIG. 10 is a schematic configuration diagram showing a color printer including an optical writing head according to the present invention.

FIG. 11 is a perspective view showing a light quantity measuring unit mounted on the color printer.

FIG. 12 is an explanatory diagram showing a positional relationship between an optical writing head and a light quantity measuring unit.

FIG. 13 is a block diagram showing a multivalued image reproduction driver IC.

FIG. 14 is a timing chart showing the operation of the multivalued image reproduction driver IC.

[Explanation of symbols]

 Reference Signs List 20 optical writing head 30 optical shutter module 31 optical shutter chip 40, 60 driver IC 70 light intensity measuring device 71 measuring unit 72 photoelectric conversion sensor 73a slit 80 integrating circuit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G01J 1/44

Claims (11)

[Claims] 1. A light amount measuring method for a solid-state scanning type optical writing device for controlling on / off of a plurality of optical chips arranged in a main scanning direction based on image data, comprising: a light amount detecting sensor having a light receiving slit; The optical chip is moved in the main scanning direction so as to face the chip, and when the light amount detection sensor moves in the main scanning direction, the optical chip is thinned out so that at least the adjacent optical chip does not light up, and based on the output of the light amount detection sensor. Calculating a light amount of each optical chip by using the light amount measuring method. 2. The optical chip according to claim 1, wherein each optical chip is lit at a predetermined frequency and duty, and the light quantity of each optical chip is measured a plurality of times, and the peak value is used as the light quantity of the optical chip. Light intensity measurement method. 3. Counting the number of times of light quantity measurement between the peak value of the output light quantity of the optical chip and the peak value of the output light quantity of another optical chip, and warning an abnormality if the count value is other than a predetermined value. The light amount measuring method according to claim 2, wherein: 4. The method according to claim 1, wherein the optical chips are thinned and lighted every odd number and every even number, and the light amount is calculated at the time of forward movement or backward movement, or at the time of forward movement and backward movement of the light amount detection sensor. The light quantity measuring method according to claim 1, wherein 5. The light quantity measuring method according to claim 1, wherein each optical chip is repeatedly turned on under a plurality of driving conditions having different output light quantities. 6. A light quantity when the specific optical chip is turned on, a leak light quantity when the specific optical chip is turned off, and a wraparound light quantity are measured, a value obtained by subtracting the leak light quantity from the wraparound light quantity is multiplied by a correction coefficient, and a peak light quantity when the specific optical chip is turned on is added. 2. The light amount measuring method according to claim 1, wherein the light amount of the specific optical chip is determined by the method. 7. A solid-state scanning type optical writing head for controlling on / off of a number of optical chips arranged in the main scanning direction based on image data, and a light receiving slit. A light amount detection sensor movable in a scanning direction; a driving unit for thinning out the optical chip so that at least an adjacent optical chip does not light up when the light amount detection sensor moves in the main scanning direction; and an output of the light amount detection sensor. And a calculating means for calculating the light quantity of each optical chip based on the following. 8. The solid-state scanning optical writing device according to claim 7, wherein said driving means thins out and lights each optical chip at substantially the same frequency and duty as during image formation. 9. The optical writing head is a full-color compatible type in which a plurality of light source colors are switched at a high speed to light an optical chip, and the driving means thins out and lights each optical chip at a frequency corresponding to each light source color. The solid-state scanning optical writing device according to claim 7, wherein: 10. The optical writing head performs light source color switching at a lower speed than at the time of image formation at the time of light quantity measurement, and the driving unit turns on each optical chip a plurality of times for each light source color. The solid-state scanning optical writing device according to claim 9. 11. In a solid-state scanning optical writing device for controlling on / off of a number of optical chips arranged in a main scanning direction based on image data, the optical chips are thinned out so that at least an adjacent optical chip is not turned on. A solid-state scanning optical writing device comprising a control unit for lighting.