JPH111017A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a quantity of an output light of each optical chip of a solid scanning type optical write head in a condition that the head is built in an image forming apparatus and to form light quantity correction data on a real time basis. SOLUTION: In an image forming apparatus, an image is formed on a photosensitive recording medium such as a photographic paper or an electrophotographic photosensitive body. It comprises a solid scanning type optical write head 20 that controls ON and OFF of multiple optical shatter chips arranged in the main scanning direction X. A light quantity measuring unit 71 housing a sensor for receiving a light emitted from the optional write head 20 is moved in the main scanning direction X and each of the shatter chips is driven by a predetermined condition, then the output light quantity is measured and light correction data is generated.

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 type optical writing head provided with a PLZT optical shutter array, an LED array and the like, and an image (latent) on a photosensitive recording medium (optical recording medium) such as a photosensitive material or a photosensitive member. And an image forming apparatus for writing the image.

[0002]

2. Description of the Related Art Conventionally, in order to form an image (latent image) on a photographic paper or a film or a photoconductor for electrophotography using a silver halide photographic material, light is emitted using an optical shutter chip such as PLZT. Various optical writing heads that perform on / off control for each pixel or on / off control of an LED chip have been provided. In this type of solid-state scanning optical writing head,
In order to obtain an even image, it is necessary to measure the light amount of each optical chip and correct the light amount based on the measured value.

Conventionally, an optical writing head before being incorporated in an image forming apparatus is fixed to a jig, and the output light quantity of each optical chip is measured by a light quantity measuring device including an optical sensor to generate correction data. However, such light quantity correction data is effective only at the initial stage when the optical writing head is incorporated in the device, and when the output characteristics of each optical chip changes over time,
It cannot respond if it changes according to environmental conditions.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to measure the output light quantity of each optical chip of a solid-state scanning optical writing head in a state where it is incorporated in an apparatus, and to be able to create light quantity correction data in real time. An object of the present invention is to provide an image forming apparatus. Another object of the present invention is to provide an image forming apparatus capable of monitoring the light quantity of the optical writing head by a light quantity measuring sensor for creating light quantity correction data when writing an image with the optical writing head.

In order to achieve the above object, an image forming apparatus according to the present invention comprises: a solid-state scanning optical writing head for controlling on / off of a number of optical chips arranged in a main scanning direction based on image data; Conveyance means for moving the photosensitive recording medium in the sub-scanning direction on the imaging surface of light emitted from the optical writing head, an optical sensor for receiving light emitted from the optical writing head, and Moving means for moving in the scanning direction.

Further, another image forming apparatus according to the present invention is characterized in that the solid-scanning optical writing head and a photosensitive recording medium moving in the sub-scanning direction on an image forming point of light emitted from the optical writing head. A deflecting member for deflecting light emitted from the optical writing head, an optical sensor for receiving the light deflected by the deflecting member, and a movement for integrally moving the deflecting member and the optical sensor in the main scanning direction. Means.

In the present invention, when the optical sensor moves in the main scanning direction, the light amount of each optical chip of the solid-state scanning type optical writing head is measured by the optical sensor, and the light amount correction data is created to perform the image writing process. Feedback, that is, since the light amount measuring means is incorporated in the device, it is possible to measure the light amount periodically or at an arbitrary time to update the correction data, and the output characteristics of the optical chip can be changed over time. It is possible to cope with a case in which it changes according to environmental conditions.

In the case where the photosensitive recording medium is a photosensitive material such as photographic paper or film, the optical sensor moves in the main scanning direction on the image forming point of the optical writing head, as in the case of the photosensitive material, or has a focusing lens. Move to the main scanning at a position away from the image point, and measure the light amounts of all the optical chips. Even if the photosensitive recording medium is a photosensitive drum or a photosensitive material such as photographic paper or film, a deflecting member such as a prism or a mirror is provided integrally with the optical sensor, and both are moved in the main scanning direction. To deflect the light in the middle, and measure the light amounts of all the optical chips.

In particular, if the optical writing head, the guide member of the photosensitive recording medium, the optical sensor and the moving means, or the optical writing head, the deflecting member, the optical sensor and the moving means are attached as one unit to the apparatus main body, Before mounting on a unit, it is possible to adjust the position of the optical writing head and measure the amount of light in advance as a unit, thereby improving the productivity and mounting it on the apparatus with a simple positioning mechanism with high accuracy.

Further, in the present invention, it is preferable that the optical writing head irradiates light to the optical sensor when writing an image with the optical writing head. A dummy optical chip is provided and driven under a certain condition, and its output light is guided to an optical sensor, or light emitted from a light source is guided to the optical sensor via a light guide member. This makes it possible to monitor the light amount of the optical writing head even when writing an image, and to stabilize the image writing by appropriately correcting the light amount after comparing the reference light amounts or by issuing a warning.

Further, in the present invention, it is preferable that the distance by which the moving means moves the optical sensor in the main scanning direction can be changed according to the image recording width. That is, if data is acquired only for the area necessary for the light quantity correction, the light quantity correction data can be created in a short time.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings.

(First Embodiment, see FIGS. 1 to 11) FIG.
1 shows a schematic configuration of a color printer for photographic printing. The color printer includes 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 image forming section 2 is equipped with the solid-state scanning optical writing head 20 shown in FIG. 2 and the light quantity measuring unit 71 shown in FIGS. 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 rotated.
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 exposed photographic paper 4 is developed and stabilized in the processing unit 3, dried, and discharged onto a 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 the exposure, it is likely to cause a synchronization shift. To eliminate such inconveniences, it is preferable to cut the photographic paper 4 by curving it by an appropriate amount, or to adopt a configuration in which the transport path becomes slightly longer but the exposure is started after the cut. If the photographic paper is in the form of a roll and the cutting is performed before exposure, the lamp 2 is used to prevent unnecessary exposure of the photographic paper.
It is necessary to turn off 1 or reduce the brightness to such a level that it is hardly exposed, or to shield the optical writing head 20 from light by mechanical shutter means.

Next, the light amount scanning type optical writing head 20 will be described. As shown in FIG. 2, this optical writing head 20 is roughly composed of a halogen lamp 21 and a heat-insulating filter 2.
2. 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, and a dust-proof 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 driven to rotate in synchronization with writing by an optical shutter chip composed of PLZT 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, the slit plate 27 is provided with a heater (not shown) for maintaining the optical shutter chip at a constant temperature,
Temperature control is performed based on a detection result of a temperature detection element (not shown) provided in the module 30.

The optical shutter module 30 is provided with a PLZT on a slit-shaped opening of a ceramic substrate or a glass substrate.
Is provided, and a driver IC is provided side by side with the optical shutter chip. Each of the optical 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 translucent ceramic having an electro-optic effect having a large Kerr constant, and light linearly polarized by the polarizer 33 is generated by applying a voltage to an optical shutter chip. The rotation of the polarization plane is caused by turning on / off the electric field, and the light emitted from the analyzer 34 is turned on / off. The light emitted from the analyzer 34 passes through the imaging lens array 35 and the dust-proof glass 36 and forms an image on the photographic paper 4 to form a latent image.

Next, the light quantity measuring unit 71 for measuring the light quantity of each optical shutter chip of the optical writing head 20 will be described. As shown in FIGS. 3 and 4A, the light quantity measuring unit 71 includes a photoelectric conversion sensor 72, a slit plate 73, and a light diffusion plate 74, and a guide rod 76.
It is slidably attached to Guide rod 76
Is installed in parallel with the main scanning direction (arrow X direction) by the optical shutter module 30, and the light quantity measuring unit 71 reciprocates at a constant speed in the arrow X direction with the sensor 72 positioned directly above the optical shutter chip. . Another guide rod 76a has an external thread formed on the outer peripheral surface thereof, and a nut (not shown) provided on the light quantity measuring unit 71 is screwed to the external thread. Therefore, the light quantity measuring unit 71 reciprocates with the forward / reverse rotation of the guide rod 76a driven by a motor (not shown).

The slit plate 73 and the light diffusion plate 74 are
2 on the incident side. The slit plate 73 has a width of 25 to 400% of the width of one pixel (preferably 50 to 200%).
%), 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 light quantity measuring unit 71 having the above configuration
The optical writing head 20 is controlled by a sequencer, and the reciprocating motion of the light quantity measuring unit 71 and the timing of the light quantity measurement are controlled. When measuring the light amount, the optical writing head 20
Is the drive mode (drive frequency,
(Lighting duty, blinking data). The light quantity measuring unit 71 is configured to obtain an integrated value of the light quantity of each optical shutter chip in synchronization with the driving. Normally,
The relationship between the driving frequency and the driving speed of the sensor 72 is set so that sampling and holding are performed ten or more times per chip. The output of the sensor 72 is A / D converted, transferred to the control unit, and performs 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 msec) 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, the light quantity is measured in the same manner as described above while repeatedly turning on the even-numbered optical shutter chips, and data is fetched. This completes the light quantity measurement of all the optical shutter chips. Of course, the light quantity measurement of all the optical shutter chips may be performed when the sensor 72 moves 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 as in the first embodiment, 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.
In the case of a color print compatible head, three types of sensors 72 are prepared corresponding to each of the three primary colors, using white illumination light.
The respective light amounts may be measured.

The control unit calculates the identification (address) and the amount of light of the optical shutter chip from the peak value of the acquired measurement data. When the light amount is measured in four steps, the measured light amount at four points is approximated by a cubic curve, and each light amount value (for example, 0 to 0)
A correction coefficient of 255 steps (multi-gradation) is determined.

Next, the principle of light quantity measurement at the time of thinning-out lighting will be described with reference to FIGS. First, the drive signal A is applied to the odd-numbered optical shutter chips. Drive signal A
Are the frequencies and the duty values that are the same or close to the driving conditions in the actual machine. Light output B 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, by performing the peak detection of the output light amount, the position of the odd-numbered chip 31 can be identified (addressed). The minimum light amount between the chips 31 varies depending on the MTF of the imaging lens, the slit width, and the like. Similarly, the measurement of all the chips is completed by measuring the even-numbered chips 31.

In the light quantity measurement described above, 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. Further, in the first embodiment, the light quantity at ON and the light quantity at OFF can be 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.

When performing light quantity correction, the specific chip light quantity is
It is necessary to consider not only the maximum light quantity at ON, but also the leak light quantity (light quantity at OFF) and the wraparound from the adjacent chip (minimum light quantity at ON), and it is preferable to experimentally correct by the following formula. Specific chip light amount = maximum light amount of specific chip + (wraparound light amount-leakage 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 above-described measurement method has been described with an example in which lighting is performed every other dot, various lighting patterns may be used, for example, thinning-out lighting may be performed at every certain integer, and a lighting chip may be identified from its peak value. . The chip interval is determined in advance at the time of manufacture, and a chip that is not lit can be identified by equally dividing the peak value by the thinning-out lighting interval.

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. 7). 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.

Next, a driver IC for driving the optical writing head 20 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. 9 shows a configuration of the multi-value reproducing driver IC 40, and FIG. 10 shows a timing chart thereof. The driver IC 40 uses n ICs successively in a ladder chain. Each IC 40 is configured to drive 64 dots, and a 6-bit shift register 41 is used.
6-bit latch circuit 42, 6-bit comparator 4
It comprises a 3 and 6-bit counter 44, 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.

[0042] 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 reproducing driver I having the above configuration
When the light quantity measurement mode is executed in C40, the predetermined light quantity is specified by a data signal DATA (dip switch or the like), transferred to the shift register 41, latched by the strobe signal STB, and the duty according to the data signal DATA is set by the comparator 43. And the like, and a predetermined light shutter chip is operated at a predetermined light amount by the gate signal GATE. 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 odd rows and even rows, 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.

The light quantity 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 light quantity 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 when measuring the light quantity (see the dashed line in FIG. 3).

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. 4A). Does not occur. 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 printing paper 4 from rising, and is configured to be pressed against the printing paper 4 by its own weight or by a spring or the like. The slit plate 73 installed in the light quantity measuring unit 71 is set to the same plane as the focus plane F, but is retracted from the transport path of the photographic paper 4 except when measuring the light quantity as described above.

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. If the opening is eliminated, the guide function of the photographic paper 4 is improved. 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. 4B, a lens 75 may be interposed between the imaging lens array 35 and the slit plate 73. By arranging the lens 75, the light quantity measuring unit 71 can be separated from the focus surface F, and it is not necessary to evacuate the light quantity measuring unit 71 during exposure, which contributes to downsizing of the apparatus. In this case, the upper guide plate 1
2 can be formed of a translucent material.

In the present color printer, the RGB color filters 25 of the optical writing head 20 are rotated to switch the light source colors at high speed, and the R, B, and G images are converted to PL 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 measurement of the light amount of the optical shutter chip and its correction (calibration) are performed according to the width of the photographic paper on which it is set. 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.

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 characteristic due to the drive 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 measures is to measure the amount of light by driving the other colors (red and green) with the same voltage as the driving voltage using the optimum voltage (the voltage with the highest transmitted light intensity, also referred to as a half-wavelength voltage) at the time of blue exposure. It is to be. This is because if the optical shutter chip is driven even at the time of exposure of another color with the optimum voltage at the time of exposure in the blue region having a short wavelength, the difference in contrast between the colors can be minimized.

Another means is to measure the amount of light by driving at the optimum voltage of each light source color. However, it is necessary to change the drive voltage at a high speed, and the waveform of the drive voltage may be distorted. Therefore, it is preferable to execute the measurement and the actual photographing using (the same) power supply having the same characteristics.

In the light quantity measuring method based on the thinned-out lighting described above, the address is determined from the peak value of the output light quantity of the thinned-out chip without requiring a special device for determining the address of each optical shutter chip. By counting the number of times of sampling between the peak values, when the optical writing head 20 is used as an inspection device, it is possible to detect an abnormality (pitch error, alignment failure, etc.) of the optical writing head 20. Also, the light amount measurement unit 7
1 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, printing image data read by a film scanner (not shown) 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 the warm-up of the printer.

Further, in the first embodiment, when an image is printed by the optical writing head 20, the optical writing head 20 sends a signal to the sensor 72 of the light quantity measuring unit 71 retracted to the position shown by the one-dot chain line shown in FIG. Light irradiation may be performed. Specifically, a dummy optical shutter chip is added to the optical shutter module 30, and a certain condition (duty,
Frequency) to guide the output light to the sensor 72, or
The light emitted from the halogen lamp 21 is guided to the sensor 72 via a light guide fiber (not shown). With such a configuration, the light amount of the optical writing head 20 can be monitored at the time of writing an image. If the light amount is corrected appropriately or a warning is issued after comparing with the reference light amount, the image writing can be stabilized. Can be achieved.

In the first embodiment, the position of the guide plate 11, the position of the optical writing head 20, and the position of the light quantity measuring unit 71 are adjusted before the optical writing head 20 is incorporated in the printer. Measuring device 70 for that
Is shown in FIG. This measuring device 70 is obtained by incorporating a tool microscope 77 and a CCD camera 78 into the light quantity measuring unit 71. In the first embodiment, the tool microscope 77 and the CCD camera 78 are provided in the light quantity measuring unit 71. However, two sets of the tool microscope and the CCD camera 78 are provided.
A camera may be used, or these may be configured to be movable by another guide member.

The operator measures the CCD through the tool microscope 77
Each member is adjusted based on an image captured by the camera 78 and displayed on the monitor television 79. First, the reference member of the light quantity measuring unit 71 and the position of the microscope 77 are fixed. Here, the microscope 77 is set in the light quantity measuring unit 71 so that the microscope 77 is focused on the height of the slit surface of the light quantity sensor 72. In this state, the guide plate 11 and the optical writing head 20 are connected to the microscope 7.
Then, the guide plate 11 and the optical writing head 20 are moved to and fixed at the specified position in the field of view. That is, the slit surface of the light amount sensor 72, the guide plate 1
The first guide surface and the focus surface of the optical writing head 20 are integrally assembled on the same plane without inclination. Further, if necessary, the optical writing head 20 may be thinned and turned on, and the sensor 72 may be readjusted to a position where the S / N ratio becomes maximum.

As described above, by integrating the optical writing head 20, the guide plates 11, 12 and the light quantity measuring unit 71 into one unit, the unit can be simply assembled to the image forming apparatus main body, and the fine structure after the assembly is obtained. No adjustment is required, and shipping and replacement are possible. Further, a configuration in which the transport roller pairs 6 and 7 are integrally attached to this unit may be employed.

It is also possible to control the measuring device 70 and the optical writing head 20 having the above configuration by a sequencer and measure the light quantity with this device 70. However, it is usual that the light amount measuring unit 71 from which the tool microscope 77 and the like are removed is assembled to the image forming apparatus main body, and the light amount is measured inside the apparatus. Further, photographic paper of various widths can be set in the main body of the image forming apparatus.
Is configured to be writable on photographic paper of the maximum width. Therefore, in the light quantity measurement, the moving distance of the sensor 72 in the main scanning direction is controlled according to the width of the set photographic paper, instead of always measuring the entire writable width. This makes it possible to reduce the measurement time, the calculation time, and the like.

(Second Embodiment, FIGS. 12, 13 and 14)
12 and 13 show a main part of a color printer which forms an image by electrophotography using the photosensitive drum 100. FIG. The photoconductor drum 100 is driven to rotate in the direction of arrow a, and the same optical writing head 20 as shown in FIG. 2 is used for printing an image. Around the photosensitive drum 100, a charging charger (not shown), a developing device,
A transfer charger and the like are arranged. These elements are well known, and their description is omitted.

The light quantity measuring unit 71 basically has the configuration shown in FIG.
Are used, and a prism 65 (which may be a mirror or another deflecting member) for deflecting light is added. This light quantity measurement unit 71
Denotes an image forming area D of the photosensitive drum 100 (see FIG. 13)
The guide rod 76a driven by a motor (not shown) moves from the retracted position in the main scanning direction X.
It is possible to move forward. At the time of measuring the amount of light, the light output from the optical writing head 20 is reflected by the prism 65 and enters the sensor 72 through the slit plate 73 and the light diffusion plate 74. The method of measuring the light amount by the sensor 72 is shown in FIGS.
This is as described in FIG. Also, the optical writing head 2
The drive mode of 0 is the same as that of the first embodiment.

Also, in the second embodiment, when an image is printed by the optical writing head 20, the light quantity of the optical writing head 20 is monitored by the sensor 72 of the light quantity measuring unit 71 at the retract position. May be.
Also in this case, a dummy optical shutter chip is added and driven under certain conditions (duty, frequency), and the output light is guided to the sensor 72 or the light emitted from the halogen lamp 21 is transmitted to a light guide fiber (not shown). What is necessary is just to guide to the sensor 72 via a.

In the second embodiment, the optical writing head 20, the prism 65, the light quantity measuring unit 71, and the reciprocating mechanism thereof are configured as one exposure unit 110. Similarly to the first embodiment, before the exposure unit 110 is incorporated into the frame 120 of the printer, the adjusted position of the optical writing head 20 and the like are adjusted in advance. Simply by assembling to the frame 120, shipping is possible without the need for fine adjustment after assembling.

FIG. 14 shows a measuring apparatus 130 for adjusting the exposure unit 110 before assembling, and corresponds to the measuring apparatus 70 shown in FIG. This measuring device 13
Numeral 0 denotes an adjustment jig 131 in which a tool microscope 132 having a CCD camera 133 is accommodated so as to be movable in a main scanning direction by a guide rod 134, and an image captured by the CCD camera 133 is displayed on a monitor television 135. Adjusting jig 1
The mounting surface 131a of the frame 31 is the same as the mounting surface 120a of the frame 120 shown in FIGS. 12 and 13, and the exposure unit 110 is mounted on the mounting surface 131a. The focal point 132a of the tool microscope 132 is the photosensitive drum 1
When the optical writing head 20 is set at a predetermined position, the output light forms an image at the focal point 132a.

The tool microscope 132 is moved in the main scanning direction while driving the optical writing head 20 to adjust the tilt so that the light is positioned at the center of the visual field. Is moved in the direction of arrow b to perform focus adjustment. The focus of the optical writing head 20 can be adjusted automatically based on the output of the CCD camera 133 by driving the optical shutter chip by the thinning-out lighting method described above.

Next, the position of the sensor 72 is adjusted by moving the light quantity measuring unit 71 itself in the direction of arrow c. This adjustment is performed so that the output S / N ratio of the sensor 72 is maximized. Normally, the position of the sensor 72 is not so subtle, and this adjustment may be omitted.

The configuration in which a member for deflecting light is added is not limited to a printer that forms an image by an electrophotographic method using a drum-shaped photosensitive member, and the image is formed by using the above-described photographic paper or film. It can also be applied to forming devices.

(Other Embodiments) The image forming apparatus according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the invention. In particular, as a solid-scan type element used for optical writing, PLZT
LED (Light Emitting Diode), LCS (Li
quid Crystal Shutter), DMD (Deformable Mirror)
Device), FLD (Fluorescent Device) and the like can be used.

The modulation of the optical shutter module with multiple gradations may be performed by a method of modulating the pulse intensity in addition to the method of modulating the pulse width. Various methods other than the thinning-out lighting method can be adopted as a method of measuring the light amount. Further, the present invention can be applied to an image projection apparatus on a display, in addition to an image formation apparatus for photographic paper and an electrophotographic photosensitive member using a silver halide photosensitive material.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a color printer according to a first embodiment of the invention.

FIG. 2 is a perspective view showing a solid-state scanning type optical writing head mounted on the color printer.

FIG. 3 is a perspective view showing a light amount measurement unit mounted on the color printer.

FIG. 4 is an explanatory diagram showing a positional relationship between an optical writing head and a light quantity measuring unit.

FIG. 5 is a waveform diagram of an analog signal at the time of light amount measurement.

FIG. 6 is a waveform diagram of a digital signal at the time of light quantity measurement.

FIG. 7 is a block diagram of an integration circuit used for light quantity measurement.

FIG. 8 is a timing chart showing the operation of the integration circuit.

FIG. 9 is a block diagram showing a multivalued image reproduction driver IC.

FIG. 10 is a timing chart showing the operation of the multivalued image reproduction driver IC.

FIG. 11 is a schematic configuration diagram showing a measuring device before assembling the optical writing head.

FIG. 12 is a schematic configuration diagram illustrating a main part of a color printer according to a second embodiment of the invention.

FIG. 13 is a plan view of FIG. 12;

FIG. 14 is a schematic configuration diagram showing a measuring device before assembling the optical writing head for a color printer according to the second embodiment.

[Explanation of symbols]

 Reference Signs List 4: printing paper 5, 6, 7: transport roller pair 11, 12: guide plate 20: optical writing head 30: optical shutter module 40: driver IC 65: prism (deflecting member) 71: light quantity measuring unit 72: photoelectric conversion sensor 75: lens 76a: guide rod 100: photosensitive drum

Claims (14)

[Claims] 1. A solid-state scanning type optical writing head for controlling on / off of a plurality of optical chips arranged in a main scanning direction based on image data, and on an imaging point of light emitted from the optical writing head. Transport means for moving the photosensitive recording medium in the sub-scanning direction, an optical sensor for receiving light emitted from the optical writing head, and moving means for moving the optical sensor in the main scanning direction. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein said optical sensor is evacuated to the outside of a photosensitive recording medium when an image is written by said optical writing head. 3. The image forming apparatus according to claim 2, wherein the optical writing head irradiates light to the optical sensor evacuated outside the photosensitive recording medium. 4. The optical sensor according to claim 1, wherein the optical sensor includes a lens for condensing light, and is movably installed in a main scanning direction at a position distant from an image forming point of the optical writing head. 2. The image forming apparatus according to 1. 5. The optical recording medium according to claim 1, further comprising a guide member for positioning a photosensitive surface of a photosensitive recording medium at an image forming point of said optical writing head. Image forming apparatus. 6. The image forming apparatus according to claim 5, wherein the optical writing head, the guide member, the optical sensor, and the moving unit are attached to the apparatus main body as one unit. 7. The apparatus according to claim 1, wherein the optical writing head, the transporting means, the optical sensor, and the moving means are attached to the apparatus main body as one unit.
The image forming apparatus according to claim 3. 8. The image forming apparatus according to claim 7, wherein said conveying means has a roller member for moving the photosensitive recording medium at a constant speed. 9. The image forming apparatus according to claim 7, wherein said conveying means has a guide member for positioning a photosensitive surface of a photosensitive recording medium at an image forming point of said optical writing head. 10. 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-emitting element on an imaging point of light emitted from the optical writing head. A photosensitive recording medium that moves in the sub-scanning direction; a deflecting member that deflects light emitted from the optical writing head; an optical sensor that receives the light deflected by the deflecting member; An image forming apparatus, comprising: a moving unit for moving in a main scanning direction. 11. The image forming apparatus according to claim 10, wherein said deflecting member and said optical sensor are retracted outside an image forming area of a photosensitive recording medium when said optical writing head writes an image. 12. The image forming apparatus according to claim 11, wherein the optical writing head irradiates light to the light sensor evacuated outside the image forming area of the photosensitive recording medium. 13. The image forming apparatus according to claim 10, wherein the optical writing head, the deflecting member, the optical sensor, and the moving unit are attached to the apparatus body as one unit. apparatus. 14. The image forming apparatus according to claim 1, wherein a distance by which the moving unit moves the optical sensor in the main scanning direction can be changed according to an image recording width.