JP2006181974A - Apparatus and method for laser writing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and method for laser writing, where a light receiving and detecting means can be arranged in proximity to an image information writing start position and also can be downsized by outputting again an auto power control signal after bias adjustment, and by receiving and detecting a laser light beam with this timing. <P>SOLUTION: A laser writing controller 42 provided in the laser writing apparatus 40 outputs an APC signal from an auto power control (APC) controller 43 more than once. After a bias adjustment signal being the signal for a laser driver 8 to adjust a driving start current value of a light source 7 is outputted from the APC controller 43 and just before an image information signal is outputted from an image I/F section 25 and a PWM generator 24, the controller 42 controls operation according to the APC signal outputted from the APC controller 43, such that a beam detector 10 receives and detects a laser light beam in an all lights ON state irradiated from a light source 7, and outputs a writing position reference signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser writing apparatus and a laser writing method.

  In a laser writing device provided in an image forming apparatus using an electrophotographic system, an auto power control that stabilizes the output of laser light emitted from a light source at a timing before image information is written on a photoreceptor of the image forming apparatus ( (Abbreviated as APC), the beam detector (abbreviated as BD) detects the laser beam at the timing of executing APC, performs bias adjustment described later after beam detection by BD, and further detects the beam by BD after bias adjustment. The image information by the laser beam is written with the position separated by a predetermined interval with respect to the position as the image information writing start position for the photoconductor.

Hereinafter, the configuration and operation of a conventional laser writing apparatus will be described.
FIG. 10 shows a simplified configuration of a conventional laser writing apparatus 1 that performs writing as described above. The laser writing apparatus 1 generally includes a laser writing unit 2 and a laser writing control unit 3. The laser writing unit 2 has a polygon mirror 5 that is rotated at a constant speed in the direction of arrow 4 by a motor, a motor driver 6 that is a motor drive circuit that is a drive source of the polygon mirror 5, and the polygon mirror 5. A light source 7 that emits laser light, a laser driver 8 that is a drive circuit for the light source 7, a light amount sensor 9 that detects emitted light behind the light source 7, and a position of the laser light beam emitted forward from the light source 7 BD 10 that receives and detects light, a reflection mirror 11 that further reflects the light emitted forward from the light source 7 and reflected by the polygon mirror 5 to be incident on the BD 10, and condenses the laser light on the photosensitive member 13 of the image forming apparatus. And a lens 12 to be configured.

  The polygon mirror 5 has a polygonal cross-sectional shape perpendicular to the rotation axis, and a light reflecting member is provided on the surface constituting each side of the polygon, and as described above by drive control of the motor driver 6 that is a drive circuit. It rotates at a constant speed in the direction of the arrow 4.

  The light source 7 is, for example, a semiconductor laser, and can emit laser light forward and backward. The laser light emitted forward is mainly used for writing image information on the surface of the photosensitive member 13 and backward. The emitted laser light is used as monitor light for light output control. Laser light emitted forward from the light source 7 is reflected by the polygon mirror 5, further condensed by the lens 12, and irradiated onto the photosensitive member 13. At this time, since the polygon mirror 5 rotates at a constant speed in the direction of the arrow 4, the laser beam applied to the surface of the photoconductor 13 is optically scanned on the photoconductor 13.

  The BD 10, together with the reflecting mirror 11, constitutes a light receiving detection means for detecting the received light of the all-lighted laser beam emitted from the light source 7 and outputting a writing position reference signal serving as an image information writing position reference for the photoconductor 13. To do. The laser beam emitted from the light source 7 and reflected only when the polygon mirror 5 reaches a specific rotational position is further reflected by the reflection mirror 11. The BD 10 is a light receiving detector provided at a position where the reflected beam can be received. When the laser beam is received and detected, the BD 10 outputs the received light detection signal to the laser writing control unit 3 as a writing position reference signal.

  Writing of image information to the photosensitive member 13 is started when a predetermined time has elapsed from the timing at which the laser beam is received and detected by the BD 10. The positional relationship when a predetermined time elapses from the light reception timing by the BD 10 will be described with reference to the position in FIG. 10. As the polygon mirror 5 rotates in the direction of the arrow 4 from the position of the laser beam, the position of the laser beam in which the reflected light from the polygon mirror 5 is further angularly displaced by the angle θ starts writing image information on the photosensitive member 13. It is defined as a position. That is, the detection of the laser beam received by the BD 10 is to detect the reference position for starting the writing of image information on the photosensitive member 13.

  The light emitted backward from the light source 7 is detected by a light amount sensor 9 that outputs a signal corresponding to the amount of received light, and the detection output is input to the laser driver 8. The laser driver 8 drives the output of the light source 7 to a predetermined value according to the detection output of the light amount in a state where the APC signal indicating the APC execution from the APC signal control unit 23 is valid. Usually, the APC of the light source 7 is performed with the light source 7 fully turned on. Here, full lighting refers to a state in which the light source 7 is continuously lit.

  The laser driver 8 drives and controls the output of the laser light emitted from the light source 7 in accordance with the image information based on the operation command from the laser writing control unit 3 as well as the adjustment driving related to the APC of the light source 7. . Further, the laser driver 8 is turned on with a current smaller than that when the light source 7 is turned on during APC, and the current value for driving the light source 7 is controlled based on the amount of light detected by the light amount sensor 9. 7 is bias adjusting means for adjusting the drive start current (bias current) of the light source 7 in the vicinity of the current value at which the laser beam 7 starts to be emitted.

  Here, the adjustment of the bias current will be briefly described. FIG. 11 is a schematic diagram for explaining adjustment of the bias current. In FIG. 11, the horizontal axis represents the drive current supplied to the semiconductor laser as the light source, and the vertical axis represents the light output from the semiconductor laser. The semiconductor laser does not emit light, that is, does not output light when energization is started, but does not emit light until a certain current value, for example, the threshold value 102 which is the rising portion of the line 101 representing the oscillation characteristics of the semiconductor laser in FIG. Is output.

  Therefore, if the current value for energizing the semiconductor laser is zero (0) as the driving start value, there is a problem that the response of the laser light pulse for controlling the gradation of the image information is not good. Therefore, bias adjustment is performed in which the bias current is set near the threshold value 102.

  One method for adjusting the bias is to set the bias current to a fixed value. By setting the bias current BI1 as a fixed value in the vicinity of the threshold value 102, the response of the pulse is improved. However, the oscillation characteristics of the semiconductor laser, that is, the line 101 shifts depending on the operating environment such as temperature and changes with time. For example, when the line 101 is shifted to the line 103 which is the oscillation characteristic on the higher current side, and the threshold value is also shifted to another threshold value 104 on the higher current side, the following is obtained when the bias current BI1 is fixed: There is a problem like this.

  The threshold value is the portion corresponding to the brightest gradation of the image information that is written on the photoconductor with the laser light emitted from the semiconductor laser, and the light output exceeds the threshold value. The bright gradation portion of the image information is written by the laser light pulse at the rising edge of the. Therefore, when the bias current BI1 is a fixed value and the threshold value fluctuates, the intensity of the laser light pulse fluctuates even if the drive current with the bias current BI1 as a reference is the same. There is a problem that the linearity between the two becomes worse.

  Therefore, there is an apparatus that performs auto-bias that variably sets the bias current in accordance with fluctuations in the oscillation characteristics of the semiconductor laser. In this auto bias, a bias current BI 2 is set for the threshold 102 and a bias current BI 3 is set for the other threshold 104. Bias currents BI2 and BI3 are set to values smaller than threshold value 102 and another threshold value 104 by an offset current. According to such an auto bias, the linearity between the drive current based on the bias current and the laser light pulse intensity, that is, the gradation can be improved. The bias adjustment in this specification means this auto bias.

  The bias adjustment is executed in the laser driver 8 as follows, for example. For example, at the slope portion of the line 101 which is the oscillation characteristic of the semiconductor laser, the correspondence data between the drive current and the optical output is measured at least two points, and the drive current value at which the optical output becomes 0 by extrapolation from the data at the two points Ask for. A value obtained by subtracting the offset current from the obtained drive current value can be used as the bias current. Therefore, the laser driver 8 is not only a drive circuit for the light source 7 but also a processing circuit for performing the bias adjustment described above.

  Returning to FIG. 10, the configuration of the laser writing control unit 3 will be described. The laser writing control unit 3 includes a pixel clock generation synchronization control unit 21, a motor control unit 22, the APC control unit 23, a pulse width modulation (PWM) generation unit 24, and an image interface (I / F) unit. 25.

  The pixel clock generation synchronization control unit 21 is a timer unit and a timer signal generator unit. Based on the timing signal output from the pixel clock generation synchronization control unit 21, the above APC, bias adjustment, and image information writing operations are executed using, for example, the time of detection of the laser light beam by the BD 10 as a time reference. The motor control unit 22 is a power supply control circuit that outputs electric power and an operation control command to the motor driver 6 that rotationally drives the polygon mirror 5.

  The APC control unit 23 outputs an APC signal that instructs the execution timing of APC to the laser driver 8 in synchronization with the clock from the pixel clock generation synchronization control unit 21. The APC control unit 23 outputs a bias adjustment signal that is a signal for instructing the timing for the laser driver 8 to perform bias adjustment. That is, the APC control unit 23 is also a bias adjustment signal generating unit.

  The PWM generator 24 is an image information output unit that outputs a signal of image information to be written to the photosensitive member 13 and generates a laser light pulse corresponding to the gradation of the image information. The PWM generator 24 outputs an operation command as image information to the laser driver 8 and oscillates a laser light pulse from the light source 7 by controlling the drive current with reference to the bias current. An image information signal, which is an original signal for generating a laser light pulse, is given from the image processing unit 26 provided in the image forming apparatus to the PWM generating unit 24 via the image I / F unit 25. The APC control unit 23 and the PWM generation unit 24 that respectively output adjustment and writing operation commands based on the time signal output from the pixel clock generation synchronization control unit 21 are electrically connected to the pixel clock generation synchronization control unit 21. The

  Next, various adjustments and image information writing operations in the conventional laser writing apparatus 1 will be described. FIG. 12 is a timing chart for explaining the operation of the conventional laser writing apparatus 1. In addition, in FIG. 12, it illustrates about the case where the light source 7 is single.

  In the conventional laser writing apparatus 1, the APC is performed by turning on the light source 7, and the laser light beam is detected by the BD 10 using the all-on laser light beam at the APC, that is, the image information writing position reference is detected. Further, the bias adjustment is performed at the timing after the laser beam detection by the BD 10 and before the image information is written on the photoconductor 13 in accordance with the image information writing position reference detected by the BD 10.

  When the APC signal, which is an operation command for APC, is output from the APC control unit 23 at time t1 based on the time signal output from the pixel clock generation synchronization control unit 21, the laser driver 8 operates and the light source 7 All lights up. Accordingly, the APC that sets the output of the light source 7 to a predetermined value as the laser light quantity shown in FIG. 12 (e) rises to a light quantity during normal printing from time t1 to t2 with a slight delay time (= t2-t1). Be started. This APC is executed, for example, for 2 μsec from time t1 to time t4.

  At time t3 during the execution of APC from time t1 to time t4, the BD 10 detects the laser light beam output from the light source 7 that is fully lit. At time t7 when a predetermined time has elapsed from time t3 when the laser beam is detected by the BD 10, the laser driver 8 operates in accordance with a command from the PWM generator 24, and the light source 7 is driven to transfer image information to the photoconductor 13. The operation to write to is started. Here, the predetermined time (= t7−t3) is an angle from the position where the reflected light of the polygon mirror 5 is incident on the reflecting mirror 11 by the rotation of the polygon mirror 5 to the image information writing start position on the photosensitive member 13. This is the time required for angular displacement by θ.

  In the conventional laser writing apparatus 1, the bias adjustment is executed by the laser driver 8 during the predetermined time (= t7−t3). The execution timing of the bias adjustment is also set in advance based on the time signal output from the pixel clock generation synchronization control unit 21. In the example of FIG. 12, after time t3 when the laser beam is detected by the BD 10, bias adjustment is performed at time t5 with a laser light amount that is smaller than that during APC execution, and for example 1 μsec from the image writing start time t7. Before the bias adjustment ends.

  As in the conventional laser writing apparatus 1, when the bias adjustment is performed after the detection of the laser beam by the BD 10, that is, the detection of the image writing position reference, the image writing start position is shifted at least by the time required for the bias adjustment. become. Therefore, if the bias adjustment is performed between the detection of the laser beam by the BD 10 and the start of the writing of the image information, in order to ensure the angular displacement time that is the time used for the bias adjustment, the reflection mirror 11 for detecting the laser beam is detected. The distance between the installation position and the image information writing start position must be increased to some extent, which is a factor that hinders downsizing of the laser writing apparatus 1. Conversely, if it is attempted to reduce the distance from the installation position of the reflection mirror 11 for laser light beam detection to the image information writing start position, it is not possible to secure time for performing the bias adjustment.

  Some laser writing apparatuses mounted on an image forming apparatus use a two-beam light source in order to improve the writing speed of monochrome image information. FIG. 13 is a diagram illustrating a typical example of the two-beam light source 31. The two-beam light source 31 has two first and second light emitting points 32 and 33 (hereinafter referred to as first and second light sources 32 and 33 for convenience) in an integrated element. A certain first beam 34 and second beam 35 can be emitted in the same direction.

  Since the formation positions of the first and second light sources 32 and 33 provided in the two-beam light source 31 can be determined as design values, even if there are two laser light beams emitted from the light source, The position of both beams 34 and 35 can be detected by detecting only one of them with the BD 10. FIG. 13 illustrates a configuration for detecting the first beam 34.

  FIG. 14 is a timing chart for explaining the operation in the laser writing apparatus provided with the two-beam light source 31. The operation of the laser writing apparatus including the two-beam light source 31 is basically the same as that of the one-beam light source 7, and the APC and bias adjustment of the two light sources 32 and 33 are performed in series.

  When the laser light beam is detected by the BD 10 at time t8, which is the timing at which the first light source 32 is turned on and APC is performed, after the laser light beam is detected, the bias adjustment of the first light source 32, the APC of the second light source 33, and Since the image information writing is started at time t10 after the bias adjustment is performed, it takes a long time to start writing the image information after detecting the laser beam. Accordingly, FIG. 14 exemplifies performing laser light beam detection at time t9 when APC of the second light source 33 is performed, then adjusting the bias, and starting writing image information at time t10. Even in this case, there is no difference from the case of a single light source that it takes time for bias adjustment after detecting the laser beam at time t9.

  For this reason, in order to bring the detection position of the laser beam and the image information writing start position closer, the light source 7 or 31 is turned on by the image information writing signal output from the PWM generator 24, and the laser beam However, since there is a step of adjusting the phase of the reference clock of the image information write signal immediately after detecting the laser beam, the image information write signal itself may be disturbed. It is difficult to perform laser light beam detection using signals. Further, it is conceivable to turn on the light source 7 or 31 with a bias adjustment signal and detect the laser light beam. However, since the bias adjustment causes the light source 7 or 31 to output light with a drive current smaller than full lighting, it is sufficient from the BD 10. A high output voltage value cannot be obtained, and the accuracy of laser light beam detection cannot be obtained.

  Since the image forming apparatus is demanded to be compact, the laser writing apparatus mounted on the image forming apparatus is naturally required to be compact. Therefore, various proposals have also been made for the laser writing apparatus for the purpose of downsizing and cost reduction. For example, in order to perform APC of a plurality of light beams, a light receiving means for detecting the light amount for only one light beam is provided, and the light detecting means for detecting a synchronization signal is also used for the other light beams. Accordingly, there is a configuration in which it is not necessary to provide a light receiving detection unit for each of a plurality of light beams, and there is a proposal for reducing the cost and reducing the installation space of the light receiving unit (see Patent Document 1).

  However, in Patent Document 1, it is possible to adjust the bias between the start of writing image information after the detection of the laser light beam, the installation position of the reflection mirror 11 and the BD 10 that are the detection means of the laser light beam, and the image information. Since the separation distance from the writing start position is increased to hinder downsizing of the device, there is no suggestion about the problem of solving this problem and downsizing of the device, and the solution means is also disclosed. Not.

Japanese Patent Laid-Open No. 10-161049

  The object of the present invention is to output the auto power control signal again after the bias adjustment, and detect the laser light beam at this timing, thereby installing the light receiving detection means close to the image information writing start position, It is an object to provide a laser writing apparatus and a laser writing method capable of downsizing.

The present invention provides a laser writing apparatus that is provided in an image forming apparatus using an electrophotographic method and writes image information by irradiating a photosensitive member with a laser beam.
A light source that emits laser light;
A light amount sensor that outputs a signal corresponding to the amount of laser light emitted from the light source;
Auto power control signal generating means for outputting an auto power control signal instructing adjustment of laser light emitted from the light source according to the output of the light amount sensor;
Image information output means for outputting a signal of image information to be written on the photoreceptor;
A laser that adjusts the output of the laser light emitted from the light source according to the output of the light quantity sensor according to the instruction of the auto power control signal, and controls the output of the laser light emitted from the light source according to the output of the image information output means Driving means;
A light receiving detection means for receiving and detecting a laser light in a fully lit state emitted from a light source and outputting a writing position reference signal serving as an image information writing position reference for the photosensitive member;
Bias adjusting means for adjusting a bias current, which is a current value at which the light source starts driving, by controlling a driving current applied to the light source;
Outputs the auto power control signal multiple times, adjusts the laser light output by the output of the auto power control signal, adjusts the bias by operating the bias adjusting means, and then outputs immediately before the image information signal is output Control means for controlling the operation of each of the means so that the light receiving detection means receives the laser light emitted based on the auto power control signal and outputs a writing position reference signal. Laser writing device.

In the present invention, the light source includes first and second black and white image forming laser light sources for forming a black and white image, a yellow image forming laser light source that is a color image forming laser light source, a magenta image forming laser light source, and a cyan image. A laser light source for forming,
When a monochrome image is formed, the auto power control signal generating means used for any one of the color image forming laser light sources is either the first monochrome image forming laser light source or the second monochrome image forming laser light source. The automatic power control signal generating means is operated.

The present invention also provides a laser writing method for writing image information by irradiating a photosensitive member with a laser beam when an image is formed using an electrophotographic method.
An auto power control step of detecting the amount of laser light emitted from the light source and adjusting the output of the laser light emitted from the light source based on the amount of light;
A bias adjustment step of adjusting a bias current, which is a current value at which the light source begins to emit laser light, by controlling a drive current applied to the light source;
A writing position reference detecting step for detecting the reception of laser light emitted from the light source and detecting the image information writing position reference for the photosensitive member;
An image information output step for outputting a signal of image information to be written on the photoreceptor,
The auto power control step is executed a plurality of times. Among the auto power control steps executed a plurality of times, the auto power control step is executed after the bias adjustment step and before the image information output step is executed. The laser writing method is characterized in that a writing position reference detecting step is executed.

  According to the present invention, the control means provided in the laser writing device outputs an auto power control signal for adjusting the output of the laser beam emitted from the light source a plurality of times, and outputs the laser beam by the output of the auto power control signal. After adjusting the output and operating the bias adjustment means to adjust the bias, the light receiving detection means detects the laser light emitted based on the auto power control signal output immediately before the image information signal is output. Then, the operation of each means is controlled so as to output the writing position reference signal. As a result, it is possible to install the light receiving detection means for receiving and detecting the laser light in the fully lit state emitted based on the auto power control signal close to the image information writing start position. It becomes possible to reduce the size of the apparatus.

  According to the present invention, the auto power control signal generating means used for any one of the yellow, magenta, and cyan color image forming laser light sources when the black and white image is formed is provided with the first black and white image forming laser light source. Alternatively, the circuit scale can be reduced because it is operated as the auto power control signal generating means for either one of the second black and white image forming laser light sources.

  Further, according to the present invention, after the bias adjustment, the position as a reference for starting the writing of the image information is detected at the time of auto power control before the image information to be written on the photoconductor is output. A laser writing method can be provided in which devices that perform the operation steps can be concentrated and arranged in a small space and can contribute to downsizing of the device.

  FIG. 1 is a diagram showing a simplified configuration of a laser writing device 40 according to a first embodiment of the present invention. In the laser writing device 40 of the present invention, the internal configuration of an auto power control (APC) control unit 43 provided in the laser writing control unit 42 is different, and the laser writing unit 41 is used as an image information writing position reference. The position of the reflection mirror 11 constituting the light receiving detection means for outputting the writing position reference signal is very close to the image information writing start position, and the angular displacement from the position of the reflection mirror 11 to the image information writing start position. Except for the fact that the amount θx is small, the configuration is the same as that of the laser writing device 1 shown in FIG. 10 described above, and therefore the same parts are denoted by the same reference numerals and description thereof is omitted.

  The laser writing device 40 is a control unit including an APC control unit 43 having a characteristic in the internal configuration, and outputs an APC signal a plurality of times and outputs an image information signal after bias adjustment is performed. Laser writing control for controlling the operation so that the BD 10 serving as a light receiving detection unit detects and outputs a writing position reference signal for a fully lit laser beam emitted based on the APC signal output immediately before. The unit 42 is provided.

  2 is a diagram showing an outline of the configuration of the APC control unit 43, FIG. 3 is a diagram showing the internal configuration of the APC control unit 43 shown in FIG. 2, and FIG. 4 is a timing for explaining the operation of the APC control unit 43. It is a chart.

  The APC control unit 43 generally includes a main scanning timing counter 51, a basic APC generation block 52, and an open collector buffer 53.

  The main scanning timing counter 51 includes a pixel clock that is a timing signal output from the pixel clock generation synchronization control unit 21 and a laser light beam detection signal (image information written by the BD 10) via the pixel clock generation synchronization control unit 21. Input position reference signal, hereinafter referred to as a BD signal). The main scanning timing counter 51 operates so as to once clear the pixel clock every time a BD signal is input and newly start timing, and the pixel clock that is repeatedly counted every time the BD signal is input is counted as a counter value (abbreviated as CNT). ) To the basic APC generation block 52.

  The basic APC generation block 52 includes a start timing setting register 54, an end timing setting register 55, a first comparator 56, a second comparator 57, and an RS flip-flop (abbreviated as RS-F / F) 58. .

  The start timing setting register 54 holds the setting of the CNT at which the APC control unit 43 starts to output the operation start command signal for starting the driving of the laser driver 8. In FIG. 3, CNT = 1503 is illustrated as an example of timing setting for starting APC. The end timing setting register 55 holds the setting of the CNT at which the APC control unit 43 starts to output the operation end command signal for ending the driving of the laser driver 8. In FIG. 3, CNT = 2 is illustrated as an example of timing setting for terminating APC.

  The first and second comparators 56 and 57 compare the CNT input from the main scanning timing counter 51 with the set and held timing value, and turn on when the input CNT and the set timing value match. Signals are output to the RS-F / F 58, respectively.

  The RS-F / F 58 starts pulse output in response to the ON signal output in accordance with the start timing setting by the first comparator 56 and is output in accordance with the end timing setting by the second comparator 57. It operates to end the pulse output in response to the ON signal. The pulse output from the RS-F / F 58 is converted into a buffer output through the open collector buffer 53 and is given to the laser driver 8.

  As described above, since the timings of both APC and bias adjustment are set and held in the start and end timing setting registers 54 and 55, the RS-F / F 58 and the open collector buffer 53 provide APC control and bias adjustment. The operation command signal is output with the timing shifted. Therefore, in FIG. 2, two output systems are shown in order to make it easy to understand that an operation command signal for APC and bias adjustment can be output from the APC control unit 43.

  FIG. 4 illustrates an operation command signal for APC, that is, an operation for generating an APC signal, among the operation command signal generation operations by the APC control unit 43. FIG. 4A shows a BD signal by the BD 10 input to the main scanning timing counter 51. FIG. 4B shows a counter value (CNT) output by the main scanning timing counter 51. At each time t14 and t12 when the BD signal is input, CNT is cleared to 0 and output as a new CNT. The

  4 exemplifies the APC signal generation operation, the first comparator 56 shown in FIG. 4C is turned on when CNT is “12503” which is the set value of the start timing setting register 54, that is, at time t11. 4D, the second comparator 57 shown in FIG. 4D outputs the ON signal pulse 60 when CNT is “2” which is the set value of the end timing setting register 55, that is, at time t13. Output.

  As shown in FIG. 4 (e), the RS-F / F 58 starts outputting a pulse 61 at time t 11 in response to the pulse output 59 of the first comparator 56, and outputs a pulse output 60 of the second comparator 57. Accordingly, the output of the pulse 61 is terminated at time t13. As shown in FIG. 4 (f), the open collector buffer 53 inverts the output pulse 61 of the RS-F / F 58 and outputs it to the laser driver 8 as a low-active APC signal pulse 62.

  The fact that the BD signal is detected at times t14 and t12 indicates that it is repeatedly detected according to the rotation of the polygon mirror 5. That is, every time a BD signal is input to the main scanning timing counter 51, CNT is cleared, and APC and bias adjustment are repeatedly executed according to CNT that is cleared and newly counted.

  FIG. 5 is a timing chart for explaining the operation of the laser writing device 40. In the embodiment shown in FIG. 5, the APC signal is output twice, the bias adjustment signal is output between the two APC signals, and the fully lit laser light beam emitted based on the second APC signal is output. The BD 10 detects the received light, detects the writing position reference of the image information, and starts writing the image information to the photosensitive member 13 at the image information writing start position determined according to the writing position reference.

  5A shows an APC signal output from the APC control unit 43, FIG. 5B shows a bias adjustment signal output from the APC control unit 43, and FIG. 5D is detected by the BD 10. Represents a BD signal. FIG. 5C shows image information output from the image I / F unit 25 to be written on the photosensitive member 13, and FIG. 5E shows the front of the light source 7 during APC, bias adjustment, and image information writing. This represents the amount of laser light emitted to.

  First, the APC control unit 43 outputs the CNT output from the main scanning timing counter 51 based on the time signal output from the pixel clock generation synchronization control unit 21, and the APC signal held in the start timing setting register 54 and the end timing setting register 55. The first APC pulse 65, which is the first APC signal, is output from time t21 to time t22 in accordance with the start / end set value. The first APC pulse 65 is input to the laser driver 8, and the light source 7 is fully turned on (continuously emits light) by the drive control of the laser driver 8. At this time, the light amount sensor 9 detects the amount of light emitted backward from the light source 7, feeds back the detected output to the laser driver 8, and adjusts the output of the laser light emitted from the light source 7 to a predetermined value.

  Next, after the output of the first APC signal is completed, the CNT output from the main scanning timing counter 51, the start timing setting register 54, and the end timing setting register 55 are held in the same manner as the generation of the APC signal. The bias adjustment pulse 66, which is a bias adjustment signal, is output from time t23 to t24 according to the start / end setting value of the bias adjustment signal. The bias adjustment pulse 66 is given to the laser driver 8 from the APC control unit 43, and the laser driver 8 drives and controls the light source 7 so as to emit light with a light amount smaller than that of APC. While the bias adjustment pulse 66 is being output, the laser driver 8 adjusts a bias current that is a current value at which the light source 7 starts to drive.

  When this bias adjustment is completed, the second APC signal, which is a feature of the present invention, is output. The second generation of the APC signal is output in the same manner as in the first time, but starts in one cycle from when the CNT of the main scanning timing counter 51 is cleared to the next time by the BD signal. This can be realized by presetting the generation timing of the APC signal a plurality of times in the timing setting register 54 and the end timing setting register 55.

  The second APC pulse 67, which is the second APC signal, is output from time t25 to t27, and at this time, the laser driver 8 performs drive control so that the light source 7 is fully lit. When the light source 7 is fully turned on based on the second APC signal, the light beam 7 is emitted from the light source 7 and reflected by the polygon mirror 5, and further reflected by the reflection mirror 11, and the laser beam enters the BD 10. As a result, the BD 10 can detect the laser light beam in the APC state with high light intensity, and therefore can detect the image information writing position reference with high accuracy.

  The BD signal detected by the BD 10 is supplied to the main scanning timing counter 51 of the APC control unit 43 via the pixel clock generation synchronization control unit 21 to clear CNT and generate PWM via the pixel clock generation synchronization control unit 21. The time required for the PWM generator 24 to shift the laser beam reflected by the rotating polygon mirror 5 by an angle θx from the time t26 corresponding to the BD signal detection after a predetermined time has elapsed. At time t28 after the lapse, image information to be written on the photosensitive member 13 is output. This image information is given to the laser driver 8, and the laser driver 8 drives and controls the light source 7 so that the laser light output is gradation-controlled according to the image information.

  In this way, after the bias adjustment, the second APC signal is output, and during the second APC, the fully lit laser light beam is detected, that is, the BD signal is obtained to detect the writing position reference of the image information. By starting writing based on the detection result, the BD signal detection unit and the image information writing start position can be brought very close to each other, and the apparatus can be downsized.

  FIG. 6 is a diagram showing a configuration of the APC control unit 71 provided in the laser writing apparatus according to the second embodiment of the present invention. Since the laser writing apparatus according to the present embodiment is similar to the laser writing apparatus 40 according to the first embodiment, only the APC control unit 71 provided in the laser writing control unit is illustrated with the entire configuration diagram omitted. Corresponding portions are denoted by the same reference numerals and description thereof is omitted.

  The laser writing device 71 of this embodiment is an example of a laser writing device mounted on a full-color image forming apparatus. As a light source, the first and second black and white image forming for forming a two-beam black and white image is used. A laser light source; a cyan image forming laser light source that is a color image forming laser light source; a magenta image forming laser light source; and a yellow image forming laser light source. Therefore, the basic APC generation block 72 of the APC control unit 71 is also composed of a basic APC generation block 74 for black and white image formation (a first black and white image formation basic APC generation block 74a and a second black and white image formation basic APC generation block 74b), A basic APC generation block 75 for cyan image formation, a basic APC generation block 76 for magenta image formation, and a basic APC generation block 77 for yellow image formation are included. The APC control unit 71 includes an open collector buffer 73 connected to each basic APC generation block.

  Although the APC control unit 71 of the laser writing apparatus of this embodiment includes a plurality of basic APC generation blocks, the operation of each basic APC generation block is provided in the laser writing apparatus 40 of the first embodiment. Since this is the same as the basic APC generation block 52 of the APC controller 43 to be executed, description thereof is omitted.

  FIG. 7 is a timing chart for explaining the operation at the time of black-and-white image formation in the laser writing apparatus including the APC control unit 71 shown in FIG. As described above, each basic APC generation block operates in the same manner as the basic APC generation block 52 of the first embodiment. Therefore, in this embodiment, the description of the operation of the basic APC generation block is omitted, and the APC signal, Only the timing of the bias adjustment signal, BD signal detection, and image information writing start will be described.

  First, a first first APC signal 81 is output for APC of the first black-and-white image forming laser light source, and then a first bias adjustment signal 82 is output for bias adjustment of the first black-and-white image forming laser light source. The Thereafter, a second APC signal 83 is output for APC of the second black-and-white image forming laser light source, and then a second bias adjustment signal 84 is output for bias adjustment of the second black-and-white image forming laser light source.

  After the output of the second bias adjustment signal 84 is completed, a second first APC signal 85 is output again for APC of the first black-and-white image forming laser light source. Based on the second APC signal 85 for the second time, the laser driver 8 fully lights up the first black-and-white image forming laser light source, and the BD 10 detects the first black-and-white image-forming laser light beam in the fully lit state. An information writing position reference is obtained, and writing of image information by both the first and second black and white image forming laser light sources is started at an image information writing start position determined according to the writing position reference.

  Also in the laser writing apparatus of the present embodiment, the APC is executed twice for the first black-and-white image forming laser light source, the BD signal 86 is detected during the second APC, and the bias adjustment is not performed after the detection. Since the writing of the image information is started, the same effects as those of the laser writing apparatus according to the first embodiment can be obtained.

  The operation at the time of color image formation in the laser writing apparatus of this embodiment is as follows. During color image formation, a first black-and-white image forming laser light source, a cyan image forming laser light source, a magenta image forming laser light source, and a yellow image forming laser light source are used. Accordingly, APC and bias adjustment are performed for the first black-and-white image forming laser light source, APC and bias adjustment are performed for the cyan image forming laser light source, and APC and bias adjustment are performed for the magenta image forming laser light source and yellow image forming is performed. After performing APC and bias adjustment for the laser light source, APC is executed again for the first black-and-white image forming laser light source, the BD signal is detected during this APC, and then the writing position by the BD signal without performing bias adjustment. Writing of image information is started based on the reference.

  The mutual arrangement of the cyan image forming laser light source, the magenta image forming laser light source and the yellow image forming laser light source, and the first black and white image forming laser light source is determined by the second black and white image forming laser light source and the first black and white image forming Similar to the mutual arrangement with the laser light source, the design information can be determined in advance. Therefore, even when a color image is formed, the image information document of each light source can be detected only by detecting the BD signal from the first black-and-white image forming laser light source. It is possible to determine the start position of loading.

  FIG. 8 is a diagram showing a configuration of the APC control unit 91 provided in the laser writing apparatus according to the third embodiment of the present invention. The laser writing apparatus according to the present embodiment is similar to the laser writing apparatus according to the second embodiment, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.

  It should be noted in the laser writing device of this embodiment that the APC control unit 91 provided in the laser writing control unit has a basic APC generation block 74a for the first black-and-white image forming laser light source and an open collector buffer 73 connected thereto. Are electrically connected to the basic APC generation block 75 for the cyan image forming laser light source and the open collector buffer 73 connected thereto to generate an APC signal used for the cyan image forming laser light source. The basic APC generation block 75 and the open collector buffer 73 connected thereto are operated as the basic APC generation block 74a of the first black-and-white image forming laser light source and the open collector buffer 73 connected thereto.

  FIG. 9 is a timing chart for explaining the operation at the time of monochrome image formation in the laser writing apparatus including the APC control unit 91 shown in FIG. Also in this embodiment, each basic APC generation block operates in the same manner as the basic APC generation block 52 of the first embodiment. Therefore, the description of the operation of the basic APC generation block is omitted, and an APC signal, a bias adjustment signal, Only the timing of BD signal detection and image information writing start will be described.

  First, a first APC signal 92 is output from the first black and white image forming basic APC generation block 74a for APC control of the first black and white image forming laser light source. At this time, the open collector buffer 73 connected to the first black and white image forming basic APC generation block 74a and the open collector buffer 73 connected to the cyan image forming basic APC generation block 75 are electrically connected. The APC signal 92a and the APC signal are received from both the open collector buffer 73 connected to the first monochrome image formation basic APC generation block 74a and the open collector buffer 73 connected to the cyan image formation basic APC generation block 75. 92b are output as APC signals.

  Next, a first bias adjustment signal 93 is output for bias adjustment of the first black-and-white image forming laser light source. Thereafter, a second APC signal 94 is output for APC of the second black-and-white image forming laser light source, and then a second bias adjustment signal 95 is output for bias adjustment of the second black-and-white image forming laser light source.

  After the output of the second bias adjustment signal 95 is completed, in this embodiment, a cyan APC signal 96 for APC of the cyan image forming laser light source is output. The open collector buffer 73 connected to the first black and white image forming basic APC generation block 74a and the open collector buffer 73 connected to the cyan image forming basic APC generation block 75 are electrically connected. The APC signal 96 is received from both the open collector buffer 73 connected to the first monochrome image forming basic APC generation block 74a and the open collector buffer 73 connected to the cyan image forming basic APC generation block 75. 96a and APC signal 96b are output.

  In the APC control unit 91 of the present embodiment, although the APC signal is not generated twice from the first black and white image forming basic APC generation block 74a, the cyan image formation is performed after the second bias adjustment signal 95 is generated. Since the cyan APC signal 96 generated from the basic APC generation block 75 is output to the laser driver 8 as the first APC signal for the second time, it is substantially twice from the basic APC generation block 74a for first black and white image formation. It works in the same way as generating an APC signal.

  Accordingly, the cyan APC signal 96 is used as the first APC signal 96 a for the second time, and the first black-and-white image forming laser light source is fully lit. Thus, the image information writing position reference is obtained, and writing of the image information by both the first and second black and white image forming laser light sources is started at the image information writing start position determined according to the writing position reference. .

  As described above, in the laser writing apparatus according to the present embodiment, when forming a black and white image, the basic APC generation unit 75 used for the cyan color image forming laser light source is replaced with the first black and white image forming laser light source. Since it can be operated as the basic APC generation unit 74a, the circuit scale can be reduced.

  Note that the operation at the time of color image formation in the laser writing apparatus of the present embodiment is performed except that the APC of the first black-and-white image forming laser light source and the cyan image forming laser light source is executed in an overlapping manner. This is the same as the laser writing device of the second embodiment.

  Although the APC for the first black-and-white image forming laser light source and the cyan image forming laser light source are executed in an overlapping manner, a light amount sensor and a laser driver are provided for each light source, so the overlapping execution is possible. It is. Also, when APC is performed with all the cyan image forming laser light sources turned on, the laser light beam emitted from the cyan image forming laser light source is emitted from the first black and white image forming laser light source without entering the BD 10. Since the arrangement is determined so that only the laser beam incident on the BD 10 is incident on the BD 10, the BD signal error due to the overlapped APC of the first black-and-white image forming laser light source and the cyan image forming laser light source is executed. There is no detection problem.

It is a figure which simplifies and shows the structure of the laser writing apparatus 40 which is 1st Embodiment of this invention. FIG. 3 is a diagram illustrating an outline of a configuration of an APC control unit 43. It is a figure which shows the internal structure of the APC control part 43 shown in FIG. 4 is a timing chart for explaining the operation of an APC control unit 43. 3 is a timing chart for explaining the operation of the laser writing device 40. It is a figure which shows the structure of the APC control part 71 with which the laser writing apparatus which is the 2nd Embodiment of this invention is provided. It is a timing chart explaining the operation | movement at the time of monochrome image formation in a laser writing apparatus provided with the APC control part 71 shown in FIG. It is a figure which shows the structure of the APC control part 91 with which the laser writing apparatus which is the 3rd Embodiment of this invention is equipped. It is a timing chart explaining the operation | movement at the time of monochrome image formation in a laser writing apparatus provided with the APC control part 91 shown in FIG. It is a figure which simplifies and shows the structure of the conventional laser writing apparatus. It is a schematic diagram explaining adjustment of a bias current. 6 is a timing chart for explaining the operation of the conventional laser writing apparatus 1; 2 is a diagram illustrating a typical example of a two-beam light source 31. FIG. 6 is a timing chart for explaining an operation in a laser writing apparatus including a two-beam light source 31.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 Polygon mirror 6 Motor driver 7 Light source 8 Laser driver 9 Light quantity sensor 10 Beam detector 11 Reflection mirror 12 Lens 13 Photoconductor 21 Pixel clock generation synchronous control part 22 Motor control part 24 PWM generation part 25 Image I / F part 26 Image processing part 40 Laser Writing Device 41 Laser Writing Unit 42 Laser Writing Control Unit 43, 71, 91 APC Control Unit 51 Main Scan Timing Counter 52, 72 Basic APC Generation Block 53, 73 Open Collector Buffer 54 Start Timing Setting Register 55 End Timing Setting register 56, 57 Comparator 58 RS-F / F

Claims (3)

In a laser writing apparatus that is provided in an image forming apparatus using an electrophotographic method and writes image information by irradiating a photosensitive member with a laser beam,
A light source that emits laser light;
A light amount sensor that outputs a signal corresponding to the amount of laser light emitted from the light source;
Auto power control signal generating means for outputting an auto power control signal instructing adjustment of the output of the laser beam emitted from the light source according to the output of the light amount sensor;
Image information output means for outputting a signal of image information to be written on the photoreceptor;
A laser that adjusts the output of the laser light emitted from the light source according to the output of the light quantity sensor according to the instruction of the auto power control signal, and controls the output of the laser light emitted from the light source according to the output of the image information output means Driving means;
A light receiving detection means for receiving and detecting a laser light in a fully lit state emitted from a light source and outputting a writing position reference signal serving as an image information writing position reference for the photosensitive member;
Bias adjusting means for adjusting a bias current, which is a current value at which the light source starts driving, by controlling a driving current applied to the light source;
Outputs the auto power control signal multiple times, adjusts the laser light output by the output of the auto power control signal, adjusts the bias by operating the bias adjusting means, and then outputs immediately before the image information signal is output Control means for controlling the operation of each of the means so that the light receiving detection means receives the laser light emitted based on the auto power control signal and outputs a writing position reference signal. Laser writing device. The light source includes first and second black and white image forming laser light sources for black and white image formation, a yellow image forming laser light source that is a color image forming laser light source, a magenta image forming laser light source, and a cyan image forming laser light source; Have
When a monochrome image is formed, the auto power control signal generating means used for any one of the color image forming laser light sources is either the first monochrome image forming laser light source or the second monochrome image forming laser light source. 2. The laser writing apparatus according to claim 1, wherein the laser writing apparatus is operated as an automatic power control signal generating means. In a laser writing method for writing image information by irradiating a photosensitive member with a laser beam when forming an image using an electrophotographic method,
An auto power control step of detecting the amount of laser light emitted from the light source and adjusting the output of the laser light emitted from the light source based on the amount of light;
A bias adjustment step of adjusting a bias current, which is a current value at which the light source begins to emit laser light, by controlling a drive current applied to the light source;
A writing position reference detecting step for detecting the reception of laser light emitted from the light source and detecting the image information writing position reference for the photosensitive member;
An image information output step for outputting a signal of image information to be written on the photoreceptor,
The auto power control step is executed a plurality of times. Among the auto power control steps executed a plurality of times, the auto power control step is executed after the bias adjustment step and before the image information output step is executed. A laser writing method, wherein a writing position reference detecting step is executed.

Images