JP2005193460A - Scan recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scan recording device which eliminates exposure irregularities in the scanning direction in a laser optics system of the device and realizes a high-quality image recording process by facilitating the elimination of the exposure irregularities. <P>SOLUTION: In the scan recording device which is equipped with a plurality of laser light sources emitting a laser light independently and draws an image by scanning by using the laser lights emitted from the laser light sources, a laser light source for drawing LD1; a laser light source for correction LD2; a scanning means for main scanning with laser lights emitted from the laser light source for drawing LD1 and the laser light source for correction LD2; a drawing means 120 for modulating the laser light emitted from the laser light source for drawing LD1 based on drawing data; and a correction means 130 for correcting the luminescent energy of the laser light emitted from the laser light source for correction LD2 based on correction data, are provided. In addition, this device is constituted in such a way that the laser lights each from the laser light source for drawing LD1 and the laser light source for correction LD2 are shined, in a superimposition fashion, to the photosensitive surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a scanning recording apparatus that forms an image by scanning a laser beam, and more particularly to a scanning recording apparatus that improves image quality by eliminating unevenness of image density in the main scanning direction of the laser beam.

  In a scanning recording apparatus that scans a photosensitive surface while modulating a laser beam to form an image, for example, the laser beam emitted from a laser light source is deflected by a polygon mirror that rotates at high speed, and further passes through an optical system to the photosensitive surface of a photosensitive drum. Irradiation scans in the main scanning direction parallel to the rotation axis of the photosensitive drum. Further, scanning in the sub-scanning direction perpendicular to the main scanning direction is performed by rotating the photosensitive drum around the rotation axis. In such a scanning recording apparatus, exposure unevenness along the main scanning direction of the laser light easily occurs on the photosensitive surface, and density unevenness occurs in the drawn image due to the exposure unevenness. That is, the optical path length from the polygon mirror to the photosensitive surface differs depending on the reflection angle of the laser beam at the polygon mirror, that is, the deflection angle, or the deflected laser beam is scanned on the photosensitive surface at a constant speed. This is mainly due to a difference in optical path length due to a difference in refraction angle in an optical system such as an fθ lens. For this reason, the central portion in the main scanning direction on the photosensitive surface has a laser beam intensity that is several percent or more higher than both end portions, and variations in the laser beam intensity cause uneven exposure. Further, when there is a part having a different transmittance in a part of the optical system, uneven exposure occurs due to the difference in the light intensity of the laser light transmitted through the part with respect to the other part.

  As a technique for improving the exposure unevenness along the main scanning direction of such laser light, the laser light intensity when actually projected onto the photosensitive surface is monitored along the main scanning direction, and based on this monitor output. A technique for performing feedback control of light emission energy such as the intensity of laser light to be exposed and exposure time can be considered. For example, a means for detecting the laser light intensity is provided along the main scanning direction, and the current value and application time of the drive current applied to the laser light source (laser diode) based on the detection output from the laser light intensity detection means are set. The light emission energy is controlled in real time.

As another technique, the technique disclosed in Patent Document 1 measures the laser light intensity distribution in the main scanning direction on the photosensitive surface in advance, and corrects the exposure unevenness from the obtained laser light intensity distribution. Data is calculated and recorded in the memory. When the laser beam is actually scanned, main scanning is performed on the photosensitive surface by adjusting either the laser beam irradiation time or the laser beam intensity based on the recorded correction data to adjust the laser beam emission energy. The laser light intensity in the direction is made uniform, and uneven exposure is eliminated.
JP-A-8-146328

  Among these conventional techniques, the former technique requires a laser beam intensity detecting means for detecting the laser beam intensity along the main scanning direction of the laser beam. The recording apparatus becomes large and expensive. In addition, when the emission energy of the laser light is controlled in real time, extremely high speed feedback control is required, and the control becomes difficult.

  On the other hand, in the technique of Patent Document 1, since the emission energy is controlled based on the correction data recorded in advance, such a problem does not occur, but the emission energy is controlled with respect to the laser light modulated by the image signal. Therefore, the control becomes complicated and a problem associated therewith arises. That is, in a normal scanning recording apparatus, modulation is performed by controlling switching of laser light based on an image signal. In this case, when controlling emission time by controlling switching time, one pixel is exposed. It is necessary to decompose and adjust the time to be divided into a plurality of times, so the clock of the image signal must be multiplied several times, the correction resolution is defined by the limit of the clock frequency, and due to the increase of the clock frequency Increased radioactive noise becomes a problem.

  Japanese Patent Application Laid-Open No. 2004-228620 also proposes a technique for correcting the laser beam intensity when controlling the emission energy, but the value of the correction data for the laser beam intensity varies depending on the difference in switching time when performing drawing. The correction data cannot be uniquely determined, and it is necessary to prepare correction data for every combination of the switching time and the laser light intensity, and the memory for recording the correction data requires a large capacity, Correction control using the correction data is also extremely difficult.

  The object of the present invention is to solve such problems in the prior art, and to achieve high-quality image recording by eliminating exposure unevenness in the main scanning direction with a simple configuration and simple control. The scanning recording apparatus is provided.

  The present invention includes a plurality of laser light sources that independently emit laser beams, and a scanning recording apparatus that performs image drawing by scanning the laser beams emitted from the laser light sources. A scanning laser light source composed of a drawing laser light source, a correction laser light source composed of another part of the laser light source, and a scanning that sequentially scans the photosensitive surface with laser light emitted from the laser light source for drawing and the laser light source for correction. Means, a drawing means for modulating the laser light emitted from the drawing laser light source based on the drawing data, and a correcting means for correcting the emission energy of the laser light emitted from the correction laser light source based on the correction data. The laser light from the drawing laser light source and the correction laser light source is exposed to overlap each other on the same photosensitive surface.

  In the present invention, the drawing means performs the scanning based on the modulation based on the image signal as before, while the correction means performs the scanning with the light emission energy corrected by the preset correction data. Since exposure is performed by superimposing the drawing scan and the correction scan on the same photosensitive surface, the correction scanning of the laser beam in the correction means is performed by control based on the correction data uniquely set irrespective of the image data to be drawn. be able to. Therefore, it is not necessary to correct the emission energy in the drawing means, and it is not necessary to prepare correction data for every combination of the switching time of the drawing laser beam and the laser beam intensity, and the memory capacity of the correction table for recording the correction data is A small capacity may be used, and the correction control can be easily performed as a unique control.

  In the scanning recording apparatus of the present invention, the correction data is calculated based on a measurement value measured in advance for the exposure unevenness that occurs along the main scanning direction of the scanning means, and is used as correction data for canceling out the exposure unevenness. Here, the correction means includes a correction table in which correction data is recorded, and is configured to correct the light emission energy of the correction laser light source based on the correction data read from the correction table. In this case, the correction means is configured to control the light intensity of the correction laser light source along the main scanning direction, or to control the exposure time of the correction laser light source along the main scanning direction.

  In the scanning recording apparatus of the present invention, the plurality of laser light sources are composed of 2n (n is an integer of 1 or more) semiconductor lasers in which a plurality of semiconductor lasers are arranged in a direction equivalent to the sub-scanning direction, of which n Each of them is configured to have a one-to-one correspondence as a drawing laser light source and the other n laser light sources for correction.

  Next, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing a schematic configuration of an embodiment in which the present invention is applied to a laser scanning apparatus that scans a photosensitive drum to draw an image as a scanning recording apparatus of the present invention. The laser scanning device 100 includes a semiconductor laser device 101 as a laser light source, a collimator lens 102 that makes the beam shape of the laser beam (laser beam) emitted from the semiconductor laser device 101 a parallel beam, and the beam shape of the laser beam. A shaping lens 103 composed of a cylinder lens for shaping the lens, a polygon mirror 104 rotated at high speed for deflecting the laser beam, and an fθ lens optical for scanning each deflected laser beam at a constant speed on the photosensitive surface A system 105 and a photosensitive drum 106 having a photosensitive surface on which drawing is performed by irradiation with laser light are provided. In this embodiment, the polygon mirror 104 and the fθ lens 105 are defined as scanning means. The laser scanning device 100 is provided with a synchronizing photodiode TPD for receiving a laser beam deflected by the polygon mirror 104 and generating a horizontal synchronizing signal. Further, the laser scanning device 100 is provided with a light emission control circuit 110, and is configured to receive various control signals including an image signal from the external control circuit 200 to control light emission of the semiconductor laser device 101. Yes.

  The light emission control circuit 110 is an image scanning circuit (drawing) that performs drawing by switching the light emission of the semiconductor laser device 101 based on image data of an image signal input as described in detail later with reference to FIG. Means) 120 and a correction scanning circuit (correction means) 130 for correcting uneven exposure during drawing. The laser light from the semiconductor laser device 101 whose emission is controlled by the drawing unit 120 is converted into a parallel light beam by the collimator lens 102, the beam shape is shaped by the shaping lens 103, reflected by the polygon mirror 104, and the fθ lens optical system 105. The main scanning is performed in the direction of the rotation axis on the photosensitive surface of the photosensitive drum 106 at a constant speed. Further, sub-scanning is performed by the rotation of the photosensitive drum 106 around the rotation axis. As a result, exposure corresponding to the image data is performed on the photosensitive surface. In this scanning, a part of the deflected laser light is received by the synchronizing photodiode TPD, and the scanning timing is taken by the horizontal synchronizing signal generated in the external control circuit 200 based on the received light.

  The semiconductor laser device 101 is configured as a multi-beam laser device as schematically shown in FIG. 2, and here, in order to simplify the description, first and second laser diodes (semiconductor lasers). LD1 and LD2 are integrally packaged together with one monitoring photodiode MPD. The first laser diode LD1 is configured as a drawing laser diode for drawing an image, and the second laser diode LD2 is configured as a correction laser diode for correcting the emission energy of laser light. The monitor photodiode MPD receives the back beam of the laser light emitted from the drawing laser diode LD1 and the correction laser diode LD2 and detects the emission intensity. The two laser diodes LD1 and LD2 are arranged in the sub-scanning direction of the laser beam, and the two laser beams are simultaneously aligned with the photosensitive surface of the photosensitive drum 106 in the sub-scanning direction. It is configured to perform main scanning. At this time, the pitch of the two laser beams is set to be equal to the scanning pitch in the sub-scanning direction when scanning the image.

  FIG. 3 is a block diagram of the light emission control circuit 110. Each includes an image scanning circuit 120 and a correction scanning circuit 130 each having an APC function, and a monitor switching unit 140 that switches between the image scanning circuit 120 and the correction scanning circuit 130 and is connected to the monitoring photodiode MPD. The light emission control circuit 110 receives the APC loop switching signal SWapc, the image signal Video, the image clock CLKv, the correction clock CLKc, the first and second sample / hold signals SH1 and SH2, and the switching signal SWT from the external control circuit 200. Is entered. These control signals are generated based on the horizontal synchronization signal obtained by receiving the laser beam with the synchronization photodiode TPD as described above, and input to the light emission control circuit 110. The monitor switch 140 selectively switches and connects the monitoring photodiode MPD to either the image scanning circuit 120 or the correction scanning circuit 130 by the APC loop switching signal SWapc.

  The image scanning circuit 120 records image data of an image signal Video input from the outside, reads out image data based on the image clock CLKv, and outputs an image data signal, and the image data signal A drawing APC control / LD driving unit 122 that receives the video and the first sample / hold signal SH1 and controls the drawing laser diode LD1 to emit light is provided. As shown in FIG. 4, the drawing APC control / LD driving unit 122 controls the current source I of the drawing laser diode LD1 by the driving voltage Vd and converts it into a driving current Id to be applied to the drawing laser diode LD1. A V / I conversion circuit 11 for converting the light emission detection current Ir of the monitor photodiode MPD for detecting the laser light emitted from the drawing laser diode LD1 into a light emission detection voltage Vr; The converted light emission detection voltage Vr is compared with the reference voltage Vref1, and an APC voltage Vapc is output so that the light emission output of the drawing laser diode LD1 is constant based on the difference between the light emission detection voltage Vr and the reference voltage Vref1. A comparator circuit 13 composed of an analog computing unit and an output APC voltage Vapc as a first sample / hold signal Sample-and-hold to and a sample and hold (S / H) circuit 14 for outputting a drive voltage Vd which is the by H1. The V / I conversion circuit 11 is ON / OFF controlled by the image data signal, and supplies the drive current Id to the drawing laser diode LD1 when turned ON.

  The correction scanning circuit 130 records correction data measured in advance, and D / A converts the correction table 131 including a memory capable of reading the correction data recorded based on the correction clock CLKc, and the read correction data. And a D / A converter 132 that converts the reference voltage Vref2 into a reference voltage Vref2, and a correction APC / LD driving unit 133 that operates with the reference voltage Vref2 from the D / A converter 132. The correction APC control / LD drive unit 133 has the same configuration as the drawing APC control / LD drive unit 122 shown in FIG. 4, but is connected to drive the correction laser diode LD2, and The sample and hold circuit 14 is operated by the second sample and hold signal SH2, and Vref2 is used as a reference voltage. The V / I conversion circuit 11 is ON / OFF controlled by a switching signal SWT, and supplies a drive current Id to the correction laser diode LD2 when turned on.

  The operation of the light emission control circuit 110 having the above configuration will be described with reference to the timing chart of FIG. When the main scanning laser beam is received by the synchronization photodiode TPD, and the APC loop switching signal SWapc becomes H level in synchronization with a horizontal synchronization signal (not shown) generated in the external control circuit 200 based on the received light. The monitor switch 140 switches the monitor photodiode MPD to the image scanning circuit 120. At the same time, the first sample / hold signal SH1 becomes H level and the sampling operation is performed. Therefore, the light emission detection current Ir obtained by receiving the laser beam of the drawing laser diode LD1 by the monitor photodiode MPD is converted into the light emission detection voltage Vr by the I / V conversion circuit 12, and the light emission detection voltage Vr is compared with the comparison circuit. 13 is compared with the reference voltage Vref1, and the APC voltage Vapc is generated and output from the comparison circuit 13 so that the light emission output of the drawing laser diode LD1 is an output corresponding to the reference voltage Vrer1. The APC voltage Vapc is held in the sample / hold circuit 14. Thereafter, when the first sample and hold signal SH1 changes to L level, the laser beam starts main scanning with respect to the photosensitive surface of the photosensitive drum 106 by the polygon mirror 104 at a predetermined timing from the horizontal synchronizing signal. Since the V / I conversion circuit 11 is on / off controlled based on the data signal, the held APC voltage Vapc is supplied to the drawing laser diode LD1 as the drive current Id at the on timing. As a result, the drawing laser diode LD1 emits light with a light emission output that is APC controlled following the reference voltage Vref1 based on the image data signal, and executes drawing on the photosensitive drum 106 by the deflection operation of the laser scanning device 100. It will be.

  On the other hand, when the APC loop switching signal SWapc is changed to L level, the monitor switching unit 140 switches the monitoring photodiode MPD to the correction scanning circuit 130. At the same time, the second sample / hold signal SH2 changes to the H level. Therefore, the light emission detection current Ir obtained by receiving the laser beam with the monitoring photodiode MPD is converted into the light emission detection voltage Vr by the I / V conversion circuit 12, and the light emission detection voltage Vr is compared with the reference voltage Vref2 in the comparison circuit 13. To be compared. At this time, the correction data of the reference voltage Vref2 is read from the correction table 131 in synchronization with the correction clock CLKc, and becomes a reference voltage corresponding to the correction data in the D / A converter 132. For example, as shown in FIG. 6A, on the photosensitive surface of the photosensitive drum 106 of the laser scanning device 100, the laser in the central portion in the main scanning direction due to various factors in the optical system such as the polygon mirror 104 and the fθ lens 105. In the case of a distribution characteristic such that the light intensity is high and both ends are low, the reference voltage Vref2 corresponds to this laser light intensity distribution, and as shown in FIG. 6B, the center in the main scanning direction. The reference voltage of the part is lower than that of both ends. Therefore, the APC voltage Vapc is generated and output from the comparison circuit 13 so that the light emission output of the correction laser diode LD2 is an output corresponding to the reference voltage Vrer2. Further, while the APC loop switching signal SWapc is output at the L level, the switching signal SWT is continuously output, and the drive current Id is constantly output from the V / I conversion circuit 11 to the correction laser diode LD2. doing. In this case, as described above, the APC voltage at the central portion in the main scanning direction is low, and both ends are high. The APC voltage Vapc maintains the sampled state during one main scan in which drawing is performed in the sample and hold circuit 14, converts the APC voltage Vapc into a driving current Id, and supplies the driving current Id to the correction laser diode LD2. Therefore, the intensity of the laser light emitted from the correction laser diode LD2 is low at the center portion of the main scanning and high at both ends.

  7 schematically shows the exposure state of the laser beam on the photosensitive surface, the laser beams LB1 and LB2 of the drawing laser diode and the correction laser diode are in the sub-scanning direction on the photosensitive surface of the photosensitive drum 106. Since the main scanning is performed while shifting the drawing laser beam by one pitch in the sub-scanning direction because the pixel is shifted by one pitch, each pixel drawn on the photosensitive surface has the laser beam from the correction laser diode and the drawing. The laser beam from the laser diode is exposed in a superimposed manner, and the total exposure amount in each pixel, that is, the light emission energy is the sum of the laser intensities of both diodes. Here, in the first main scan as shown in FIG. 7A, only the laser beam LB2 of the correction laser diode LD2 is scanned on the main scan line ML1, and the second scan as shown in FIG. 7B. During main scanning, drawing is performed on the main scanning line ML1 with the laser beam LB1 of the drawing laser diode LD1, and at this time, only the laser beam LB2 of the correction laser diode LD2 is scanned on the main scanning line ML2. Subsequently, as shown in FIG. 7C, in the third main scanning, drawing is performed on the main scanning line ML2 by the laser beam LB1 of the drawing laser diode LD1, and at this time, the main scanning line ML3 is displayed on the correction laser diode LD2. Only the laser beam LB2 is scanned. As a result, the main scanning lines ML1 and ML2 are scanned by superimposing the drawing laser beam LB1 and the correction laser beam LB2 preceding by one scanning line in the sub-scanning direction. Therefore, as described above, the intensity distribution of the laser beam scanned with the correction laser beam LB2 of the correction laser diode LD2 is the distribution in the main scanning direction on the photosensitive surface of the photosensitive drum 106 as shown in FIG. As shown in FIG. 6C, exposure is performed with uniform laser light intensity at the center and both ends in the main scanning direction, and uneven exposure is eliminated.

  As described above, in the light emission control circuit 110 according to the first embodiment, the drawing scanning circuit 120 only needs to perform APC control to draw an image based on the image data, as in the conventional laser scanning device. . Further, the exposure unevenness in the main scanning direction that occurs during the drawing can be corrected by main-scanning the photosensitive surface with the laser beam of the correction laser diode LD2 with the light intensity corrected by preset correction data. Therefore, the scanning of the correction laser beam can be performed by control based on the correction data uniquely set regardless of the image data to be drawn. Therefore, it is not necessary to prepare correction data for every combination of switching time and laser light intensity, the memory capacity of the correction table for recording correction data may be small, and correction control is easy as a unique control. It becomes possible to do. Further, the rate of change of the laser intensity distribution in the main scanning direction is a sufficiently long and gentle change compared to the period (frequency) of the image data, so that correction is performed when main scanning is performed on the photosensitive surface with the correction laser diode LD2. The timing for reading data, that is, the correction clock CLKc can be sufficiently delayed as compared with the image clock CLKv for reading the image data signal of the drawing laser diode LD1, and radiation noise due to an increase in clock frequency can be reduced. It becomes.

  FIG. 8 is a block circuit diagram of the second embodiment of the light emission control circuit 110 when the present invention is applied to the laser scanning device of FIG. 1, and the same reference numerals are given to the parts equivalent to the first embodiment. The light emission control circuit 110 includes the drawing scanning circuit 120 and the correction scanning circuit 130 as in the first embodiment. In particular, the drawing scanning circuit 120 has the same configuration as that in the first embodiment. On the other hand, the correction scanning circuit 130 is configured to time-control the laser beam here, and based on the correction table 131 in which correction data similar to that in the first embodiment is recorded and the correction data read from the correction table 131. A PWM modulator 134 for controlling the pixel exposure time, that is, the pulse width, is provided, and the APC control / LD driving unit 133 is controlled to switch based on the PWM signal from the PWM modulator 134. The switching operation in the APC control / LD driving unit 133 is the same as the operation in the APC control / LD driving unit 122 shown in FIG.

  In the second embodiment, as shown in the timing chart of FIG. 9, the correction scanning circuit 130 controls the light emission time of the correction laser diode LD2. That is, when the APC loop switching signal SWapc synchronized with the horizontal synchronizing signal outputs L level, the monitor switching unit 140 switches the monitoring photodiode MPD to the correction scanning circuit 130. At the same time, the second sample and hold circuit SH2 changes to H level. Therefore, the light emission detection current Ir obtained by receiving the laser beam with the monitoring photodiode MPD is converted into the light emission detection voltage Vr by the I / V conversion circuit 12, and the light emission detection voltage Vr is compared with the reference voltage Vref2 in the comparison circuit 13. To be compared. Therefore, the APC voltage Vapc is generated from the comparison circuit 13 so that the light emission output of the laser diode LD2 is an output corresponding to the reference voltage Vref2. The PWM modulator 134 controls the switching time and the pulse width corresponding to one pixel corresponding to the correction data read from the correction table 131 in synchronization with the correction clock CLKc. For example, in the same manner as in the first embodiment shown in FIG. 6A, on the photosensitive surface of the photosensitive drum 106, when the laser light intensity at the center in the main scanning direction is high and the both ends are low, the pulse width is the laser width. As shown in FIG. 9 in which the laser light intensity in FIG. 6B corresponds to the pulse width, the pulse width at the center in the main scanning direction is smaller than both ends. For this reason, the exposure amount of the laser light emitted from the correction laser diode LD2 and applied to the photosensitive surface is small at the central portion of the main scan and large at both ends.

  Since each laser beam of the correction laser diode LD2 and the drawing laser diode LD1 is shifted by 1 pitch in the sub scanning direction on the photosensitive surface of the photosensitive drum 106, the main scanning is performed by shifting the drawing by 1 pitch in the sub scanning direction. As a result, the pixels drawn on the photosensitive surface are exposed by overlapping the laser beam from the correction laser diode and the laser beam from the drawing laser diode, as shown in FIG. 6C. In addition, the total exposure amount in each pixel is the sum of the exposure amounts by both diodes. Therefore, if the exposure amount of the laser beam scanned by the correction laser diode LD2 corresponds to the distribution in the main scanning direction on the photosensitive surface of the photosensitive drum 106, uniform exposure is performed at the center and both ends in the main scanning direction. In this way, exposure unevenness is eliminated.

  Here, in the second embodiment, the laser beam LB2 of the correction laser diode LD2 shown in FIG. 7 is controlled in its exposure amount by PWM modulation for each dot when correction is performed. The light LB1 is preferably exposed in a state where it overlaps each dot of the laser light LB2. Therefore, the correction clock CLKc is configured as a clock synchronized with the same frequency as the drawing clock CLKv. In FIG. 9, the correction clock CLKc is generated at a frequency that matches the minimum cycle of the image data Video drawn by the image clock. . That is, the laser beam LB2 of the correction laser diode LD2 corresponding to one period of the correction clock CLKc is PWM-modulated dot by dot, as shown in the timing waveform in which a part of the correction clock CLKc is enlarged on the lower side of FIG. Exposure is performed with an exposure amount, and LD light emission of image data is performed so as to overlap each dot.

  As described above, the drawing laser diode LD1 only needs to perform APC control and draw an image based on the image data in the same manner as the conventional laser scanning devices. Regarding the exposure unevenness in the main scanning direction in the laser scanning device, when the correction laser diode LD2 is main-scanned on the photosensitive surface, scanning is performed with pulse width control corrected by preset correction data. The laser beam scanning control can be uniquely performed regardless of the image data to be drawn. Therefore, it is not necessary to prepare correction data for all combinations of switching time and pulse width, the correction table for recording the correction data may be of a small capacity, and correction control can be easily performed. Further, since the rate of change of the laser intensity distribution in the main scanning direction is a sufficiently long and gentle change in proportion to the period (frequency) of data, the PWM modulation that controls the light emission time of the correction laser diode LD2 The device 134 can be configured by preparing a plurality of correction clocks CLKc having different duty ratios and switching them. Therefore, it is not necessary to increase the clock frequency more than necessary, and it is possible to reduce radiated noise due to an increase in the clock frequency.

  Here, if each exposure by the drawing laser diode and the correction laser diode in the present invention can be performed on the same pixel on the photosensitive surface, the scanning of the correction exposure by the correction laser diode is performed by the drawing laser diode. It may be performed either before or after the drawing scan by.

  In the first and second embodiments, the case of using a multi-beam semiconductor laser device composed of two laser diodes has been described for the sake of simplicity. However, a multi-beam semiconductor laser composed of four or more laser diodes has been described. The present invention can be similarly applied to an apparatus. In general, in the case of a multi-beam semiconductor laser device composed of 2n (n is an integer of 1 or more) laser diodes, n laser diodes are used for drawing and other n laser diodes are used for correction. Used for. In such a case, the scanning pitch in the sub-scanning direction differs depending on the arrangement state of these laser diodes. For example, when two drawing laser diodes and two correction laser diodes are arranged in this order, the main scanning may be performed while being sent in units of two pitches in the sub-scanning direction.

  Further, a configuration may be adopted in which one or a smaller number of correction laser diodes than the drawing laser diodes are used for a plurality of drawing laser diodes. For example, as shown in FIG. 10, when two drawing laser diodes LD11 and LD12 and one correction laser diode LD21 are used, the laser light from the correction laser diode LD21 is transmitted by a cylinder lens 107 or the like. The laser beam width is almost doubled in the sub-scanning direction, and the correction exposure scanning is simultaneously performed simultaneously on a region extending over two main scanning lines in which drawing scanning is performed by the two drawing laser diodes LD11 and LD12. May be performed.

  The present invention is not limited to the laser scanning device as described in the embodiments, and a laser scanning device that causes qualitative exposure unevenness in the main scanning direction when scanning the laser beam, or scans the laser beam. The present invention can be similarly applied to any scanning recording apparatus that records information.

1 is a plan view of a schematic configuration of a laser scanning device to which the present invention is applied. It is a typical block diagram of a semiconductor laser apparatus. FIG. 3 is a block circuit diagram of a light emission control circuit according to the first embodiment. It is a block circuit diagram of an APC control / LD drive circuit. FIG. 6 is a timing waveform diagram for explaining the operation of the first embodiment. It is a figure for demonstrating light intensity correction | amendment in a photosensitive surface. It is a schematic diagram of the laser beam scanning for demonstrating correction | amendment operation | movement in a photosensitive surface. 6 is a block circuit diagram of a light emission control circuit of Example 2. FIG. FIG. 6 is a timing waveform diagram for explaining the operation of the second embodiment. It is a schematic block diagram for demonstrating a modification.

Explanation of symbols

LD1 1st laser diode (laser diode for drawing)
LD2 Second laser diode (correction laser diode)
MPD Photodiode for monitoring TPD Photodiode for synchronization 10 Laser drive circuit 11 V / I conversion circuit 12 I / V conversion circuit 13 Comparison circuit 14 Sample and hold circuit 100 Laser scanning unit 101 Light source unit 104 Polygon mirror 105 fθ lens optical system 106 Photosensitive drum 110 Light emission control circuit 120 Image scanning circuit 121 Image memory unit 122 APC control / LD driving unit 130 Correction scanning circuit 131 Correction table 132 D / A conversion circuit 133 APC control / LD driving unit 134 PWM circuit 200 External control device

Claims (8)

In a scanning recording apparatus that includes a plurality of laser light sources that independently emit laser light and that scans the photosensitive surface with the laser light emitted from the laser light source to draw an image, one of the plurality of laser light sources. The drawing laser light source composed of a part, the correction laser light source composed of another part of the laser light source, and the laser light emitted from the drawing laser light source and the correction laser light source are sequentially applied to the photosensitive surface in sequence. Scanning means for scanning, drawing means for modulating laser light emitted from the drawing laser light source based on drawing data, and correction of emission energy of the laser light emitted from the correction laser light source based on correction data Correcting means for performing exposure by superimposing the respective laser beams from the drawing laser light source and the correcting laser light source on the same photosensitive surface. Scanning recording apparatus according to symptoms. 2. The correction data according to claim 1, wherein the correction data is correction data for calculating the exposure unevenness generated along the main scanning direction of the scanning unit based on a measurement value measured in advance and canceling out the exposure unevenness. The scanning recording apparatus according to the description. The scanning recording according to claim 2, wherein the correction unit includes a correction table in which the correction data is recorded, and corrects the light emission energy of the correction laser light source based on the correction data read from the correction table. apparatus. The scanning recording apparatus according to claim 1, wherein the correction unit controls the light intensity of the correction laser light source along a main scanning direction. The scanning recording apparatus according to claim 1, wherein the correcting unit controls an exposure time of the correcting laser light source along a main scanning direction. The plurality of laser light sources are composed of 2n (n is an integer of 1 or more) semiconductor lasers in which a plurality of semiconductor lasers are arranged in a direction equivalent to the sub-scanning direction, of which n are other laser light sources for drawing. 6. The scanning recording apparatus according to claim 1, wherein the n laser light sources for correction have a one-to-one correspondence with each other. The scanning unit is configured to first expose one of the drawing laser beam and the correction laser beam and the other after the same pixel on the photosensitive surface. The scanning recording apparatus according to claim 1, wherein: A laser diode for monitoring the laser light emitted from the laser light source for drawing and the laser light source for correction, wherein the drawing means and the correcting means are laser beams of the laser light source detected by the photodiode for monitoring; 8. The scanning recording apparatus according to claim 1, wherein the light emission outputs of the drawing laser light source and the correction laser light source are feedback-controlled in accordance with the intensity.

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