JP2007144800A - Scan reference signal output apparatus and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a signal used as a reference of scan to be output by specifying the scanning direction with a simple circuit constitution. <P>SOLUTION: When a laser beam is moved for scanning in the outward trip direction with a scan reference signal output apparatus, firstly, the sensor signal from the first light-receiving element PD1 starts to the level higher than a threshold voltage Vth, and a comparison signal of high level is output from a comparator 90, then a gate signal is output by a gate signal forming circuit 84. If the level of the sensor signal from the second light-receiving element PD2 is higher than the one of the sensor signal of the first light-receiving element PD1, the comparison signal C of high level is output from the comparator 88. When the level of the gate signal is high and the level of the comparison signal C from the comparator 88 is also high, the level of a scan start signal becomes high, then the signal is output. On the other hand, when the leaser beam is scanned in the return trip direction, the level of the scan start signal becomes low, then the signal is output. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning reference signal output device and an image forming apparatus, and more particularly, to a scanning reference signal output device that outputs a scanning beam reference signal when a scanned light beam is received, and the scanning reference signal output device. The present invention relates to an image forming apparatus using.

  Conventionally, a laser beam scanning device that scans a laser beam at high speed using a polygon mirror or the like has been widely used in an outer diameter measuring instrument, a laser printer, and the like. As shown in FIG. 13, in the basic configuration of a typical light beam scanning device using a polygon mirror 151, the polygon mirror 151 is rotated at a constant speed by a motor 152, and the light beam emitted from the semiconductor laser 153 is The collimator lens 154 makes a parallel beam that is incident on the surface of the polygon mirror 151, and the light beam is repeatedly moved and scanned on the scanning surface by the rotation of the polygon mirror 151.

  Each surface of the polygon mirror is made to have high flatness, and scanning of each surface is performed with high accuracy. However, since each surface of the polygon mirror has a division error between adjacent surfaces, the scanning range and the scanning start point differ for each surface, and if the scanning start point differs for each surface, The position of the beam cannot be specified, and the vertical line does not become a straight line if a laser printer is used.

  It is impossible to improve the division accuracy so that such a problem does not occur. When a synchronization detector 155 is provided on the scanning start side as shown in FIG. 13 and the laser beam passes through the synchronization detector 155, The scanning position is determined by generating a synchronization detection signal and measuring the time based on this signal. Since the flatness of each surface of the polygon mirror 151 is produced with high accuracy as described above, the scanning for each surface is highly accurate, and the synchronization detector 155 detects the starting point for each scanning and uses it as a reference. As a result, highly accurate scanning is possible as a whole.

  Further, as shown in FIG. 14A, the laser beam 600 passes through the light receiving surface of the synchronization detector 155 of the laser beam scanning reference signal output device, and the output from the synchronization detector 155 as shown in FIG. 14B. Is obtained. Therefore, the output of the synchronous detector 155 is input to a comparator (comparator) using the threshold value shown in the figure as a reference level, and a binarized output as shown in FIG. By measuring the time when the light beam passes, the scanning position can be specified accurately.

Further, in order to improve the detection accuracy of the light beam, light that generates a stable scanning reference signal with little error even if there is a fluctuation in the intensity of the light beam by two light receiving means arranged adjacent to each other in the scanning direction. A beam scanning reference signal output device is known (Patent Document 1).
JP-A-6-148542

  However, in the light beam scanning reference signal output device described in Patent Document 1, it is good for an optical scanning device that scans a light beam in a certain direction. Since the light beam passes through each light receiving means, the scanning reference signal is output, and the separation circuit for separating the scanning reference signal and whether the scanning reference signal is output in the forward or backward beam scanning. There is a problem that a determination circuit or the like for determination is required, and the circuit configuration becomes complicated.

  The present invention has been made in order to solve the above-described problems, and has a simple circuit configuration and is capable of outputting a scanning reference signal by specifying a scanning direction and outputting a scanning reference signal. An object of the present invention is to provide an image forming apparatus.

  In order to achieve the above object, a scanning reference signal output device according to a first invention receives a light receiving element that outputs a reference position signal by receiving a scanned light beam, and receives the light beams in a predetermined order. When a plurality of reference position signal output means arranged in the scanning direction of the light beam and the light receiving element arranged to receive the light beam for the first time, the reference position signal is output. A gate that generates a gate signal having a pulse width exceeding the magnitude from the rising edge of the position signal to the rising edge of the reference position signal output from the light receiving element arranged to receive the light beam after the light receiving element. A signal generation circuit; and the gate signal generated by the gate signal generation circuit and the light receiving element arranged to receive the light beam after the light receiving element. It is configured to include a logical product output circuit for outputting a logical product of the reference position signal output from the optical element as a scan reference signal.

  According to the scanning reference signal output device according to the first aspect of the present invention, when a plurality of light receiving elements arranged in a row scan the light beam so as to receive the light beam in a predetermined order, the light beam is first received. A reference position signal is output from the received light receiving element, and a gate signal is generated by a gate signal generation circuit based on the reference position signal. Then, a reference position signal is output from a light receiving element arranged so as to receive the light beam after the light receiving element that first receives light, and a logical product of the reference position signal and the generated gate signal is output by a logical product output circuit. And a high level scanning reference signal is output.

  On the other hand, when the light beam is scanned so that the plurality of light receiving elements receive the light beams in the order opposite to the predetermined order, the light receiving elements arranged to receive the light beams after the light receiving elements that receive the light first are used. The reference position signal is output, and then the reference position signal is output from the light receiving element arranged to receive the light beam first, and the gate signal generation circuit generates the gate signal. The scanning reference signal at a low level is output.

  Therefore, since it has a simple circuit configuration including a plurality of light receiving elements, a gate signal generation circuit, and a logical product output circuit, and outputs a scanning reference signal only when the light receiving elements receive light in a predetermined order, Even when the beam is reciprocally scanned, the scanning reference signal can be output by specifying the scanning direction.

  An image forming apparatus according to a second aspect of the invention includes a light beam emitting unit that emits a light beam according to image data, a light deflecting unit that deflects the light beam so that the light beam reciprocates, The light receiving element that outputs a reference position signal by receiving the light beam receives the light beam so that the light beam is received in a predetermined order when the light beam is scanned in either the forward direction or the backward direction. A plurality of reference position signal output means arranged side by side in the scanning direction of the beam, when the reference position signal is first output from the light receiving element arranged to receive the light beam, from the rising edge of the reference position signal, A signal having a pulse width exceeding the magnitude until the rising edge of a reference position signal output from the light receiving element arranged to receive the light beam after the light receiving element. A gate signal generation circuit for generating a light signal, and the reference position output from the light receiving element arranged to receive the light beam after the gate signal generated by the gate signal generation circuit and the light receiving element A scanning reference signal output device including a logical product output circuit that outputs a logical product of the signals as a scanning reference signal, and based on the scanning reference signal output by the logical product output circuit, And image forming means for forming an image by emitting a light beam.

  According to the image forming apparatus of the second invention, the light beam is emitted according to the image data by the light beam emitting means, and the light beam is deflected by the light deflecting means so that the light beam is reciprocally scanned. Here, when scanning is performed on a light receiving element in which a plurality of light beams are arranged in either the forward direction or the backward direction so as to receive the light beams in a predetermined order, the light beams are received first. A reference position signal is output from the arranged light receiving element, and a gate signal is generated by a gate signal generation circuit based on the reference position signal. Then, a reference position signal is output from a light receiving element arranged so as to receive the light beam after the light receiving element that first receives light, and a logical product of the reference position signal and the generated gate signal is output by a logical product output circuit. And a high level scanning reference signal is output.

  On the other hand, when a plurality of light receiving elements scan the light beam in either the forward direction or the backward direction so as to receive the light beams in the order opposite to the predetermined order, the light receiving elements are arranged so as to receive light first. After that, the reference position signal is output from the light receiving element arranged to receive the light beam, and then the reference position signal is output from the light receiving element arranged to receive the light beam first to generate the gate signal. In order to generate a gate signal by the circuit, a low-level scanning reference signal is output by the logical product output circuit.

  Then, the image forming unit forms an image by causing the light beam emitting unit to emit a light beam based on the scanning reference signal.

  Accordingly, the scanning reference signal output device has a simple circuit configuration including a plurality of light receiving elements, a gate signal generation circuit, and a logical product output circuit, and the forward direction so that the light receiving elements receive light in a predetermined order. In addition, since the scanning reference signal is output only when the light beam is scanned in any of the return path direction, the scanning reference signal can be output by specifying the scanning direction even when the light beam is reciprocally scanned.

  Further, the scanning reference signal output device according to the second invention is such that when the reference position signal is finally output from the light receiving element arranged so as to receive the light beam, the light receiving element from the rising edge of the reference position signal. A second gate signal generation circuit for generating a second gate signal having a pulse width exceeding the magnitude until the rising edge of the reference position signal output from the light receiving element arranged to receive the light beam before And a second product of the second gate signal generated by the second gate signal generation circuit and the reference position signal output from the light receiving element arranged to receive the light beam in front of the light receiving element. And a second logical product output circuit for outputting the scanning reference signal, and the image forming means causes the light beam emitting means to emit a light beam based on the scanning reference signal and the second scanning reference signal. Images can be formed.

  According to this configuration, when scanning a light receiving element in which a plurality of light beams are arranged in either the forward direction or the backward direction so as to receive the light beams in a predetermined order, the logical product output circuit performs high level scanning. A certain scanning reference signal is output. The plurality of light receiving elements are arranged to receive the light beam at the end when the light beam is scanned in either the forward direction or the backward direction so as to receive the light beam in the order opposite to the predetermined order. A reference position signal is output from the light receiving element, and a second gate signal is generated by the second gate signal generation circuit based on the reference position signal. A reference position signal is output from the light receiving element arranged to receive the light beam before the light receiving element arranged to receive light last, and this reference position signal and the reference position signal are output by the second AND output circuit. A logical product with the generated second gate signal is obtained, and a second scanning reference signal having a high level is output.

  Accordingly, a scanning reference signal is output when the light beam is scanned in either the forward direction or the backward direction so that the light receiving element receives light in a predetermined order, and the light beam is emitted in either the forward direction or the backward direction. Since the second scanning reference signal is output when scanning is performed, it is specified whether the scanning direction is the forward direction or the backward direction even when the light beam is reciprocated, and the forward direction and the backward direction are determined. A scanning reference signal can be output in each.

  An image forming apparatus according to a third aspect of the invention includes a light beam emitting unit that emits a light beam according to image data, a light deflecting unit that deflects the light beam so that the light beam reciprocates, and scanning. A first light receiving element that outputs a first reference position signal indicating a scanning start position in the forward direction by receiving the light beam that has been scanned in the predetermined order when the light beam is scanned in the forward direction. A plurality of first reference position signal output means arranged side by side in the scanning direction of the light beam so as to receive the light beam, and from the first light receiving element arranged to receive the light beam first, the first. Is output from the first light receiving element arranged to receive the light beam after the first light receiving element from the rising edge of the first reference position signal. First A first gate signal generation circuit for generating a first gate signal having a pulse width exceeding the magnitude until the rising edge of the reference position signal; the first gate signal generated by the first gate signal generation circuit; The logical product of the first reference position signal output from the first light receiving element arranged so as to receive the light beam after the first light receiving element is used as a reference for starting scanning in the forward direction. When the first reference position signal is output from a first AND output circuit that outputs as a first scanning reference signal, and finally from a first light receiving element that is arranged to receive the light beam, From the rising edge of the first reference position signal to the rising edge of the first reference position signal output from the first light receiving element arranged to receive the light beam before the first light receiving element. size A second gate signal generation circuit for generating a second gate signal having a pulse width exceeding the first gate signal, and the second gate signal generated by the second gate signal generation circuit and before the first light receiving element. A logical product with the first reference position signal output from the first light receiving element arranged so as to receive the light beam is output as a second scanning reference signal serving as a reference for the end of scanning in the backward direction. A first scanning reference signal output device having a second AND output circuit that outputs the second reference position signal indicating the scanning end position in the forward direction by receiving the light beam. A second reference position signal output means in which a plurality of elements are arranged in the scanning direction of the light beam so as to receive the light beam in a predetermined order when the light beam is scanned in the forward direction; The optical When the second reference position signal is output from a second light receiving element arranged to receive the beam, the light is transmitted after the second light receiving element from the rising edge of the second reference position signal. A third gate signal for generating a third gate signal having a pulse width exceeding the magnitude until the rising edge of the second reference position signal output from the second light receiving element arranged to receive the beam. And the third gate signal generated by the third gate signal generation circuit and the second light receiving element arranged to receive the light beam after the second light receiving element. A third logical product output circuit for outputting a logical product with the second reference position signal as a third scanning reference signal serving as a reference for the end of scanning in the forward direction, and is arranged so as to receive the light beam at the end. Second received When the second reference position signal is output from an element, the second reference position signal is arranged so as to receive the light beam before the second light receiving element from the rising edge of the second reference position signal. A fourth gate signal generating circuit for generating a fourth gate signal having a pulse width exceeding the magnitude until the rising edge of the second reference position signal output from the light receiving element; and the fourth gate signal generating circuit. Logic between the generated fourth gate signal and the second reference position signal output from the second light receiving element disposed so as to receive the light beam before the second light receiving element. A second scanning reference signal output device including a fourth AND output circuit that outputs a product as a fourth scanning reference signal serving as a reference for starting scanning in the backward direction; and the first to fourth scanning reference signals Based on the scanning reference signal Te is configured to include an image forming means for forming an image by emitting the light beam to the light beam emitting means.

  According to the image forming apparatus of the third invention, the light beam is emitted according to the image data by the light beam emitting means, and the light beam is deflected by the light deflecting means so that the light beam is reciprocally scanned. When the light beam is scanned in the direction, and the first light receiving element of the first reference position signal output means receives the light beam, the first light receiving element arranged so as to receive the light beam firstly receives the first light receiving element. 1 reference position signal is output, and the first gate signal generation circuit generates the first gate signal. The first reference position signal is output from the first light receiving element arranged to receive the light beam after the first light receiving element arranged to receive light first, and the first AND output The circuit outputs the logical product of the first reference position signal and the first gate signal as a first scanning reference signal that serves as a reference for starting scanning in the forward direction.

  Further, when the second light receiving element of the second reference position signal output means receives the light beam, the second reference position signal is output from the second light receiving element arranged to receive the light beam first. Then, a third gate signal is generated by the third gate signal generation circuit. Then, the second reference position signal is output from the second light receiving element disposed so as to receive the light beam after the second light receiving element disposed so as to receive light first, and the third AND output is performed. The circuit outputs the logical product of the second reference position signal and the third gate signal as a third scanning reference signal that serves as a reference for the end of scanning in the forward direction.

  On the other hand, when the light beam is scanned in the backward direction and the second light receiving element of the second reference position signal output means receives the light beam, the second light receiving element arranged so as to receive the light beam lastly A second reference position signal is output, and a fourth gate signal is generated by a fourth gate signal generation circuit based on the second reference position signal. Then, a second reference position signal is output from the second light receiving element arranged to receive the light beam before the second light receiving element arranged to receive light last, and the fourth logical product The output circuit outputs a logical product of the second reference position signal and the fourth gate signal as a first scanning reference signal that serves as a reference for starting scanning in the backward direction.

  Further, when the first light receiving element of the first reference position signal output means receives the light beam, the first reference position signal is output from the first light receiving element arranged to receive the light beam last. Based on the first reference position signal, the second gate signal generation circuit generates a second gate signal. The first reference position signal is output from the first light receiving element arranged to receive the light beam before the first light receiving element arranged to receive light last, and the second logical product The output circuit outputs the logical product of the first reference position signal and the second gate signal as a second scanning reference signal that serves as a reference for the end of scanning in the backward direction.

  Accordingly, each of the first scanning reference signal output device and the second scanning reference signal output device has a simple circuit configuration including a plurality of light receiving elements, two gate signal generation circuits, and two logical product output circuits. When the light beam is scanned in the forward direction, a first scanning reference signal serving as a reference for starting scanning in the forward direction and a third scanning reference signal serving as a reference for ending scanning are output, and the backward direction is output. When the light beam is scanned, the fourth scanning reference signal serving as a reference for starting scanning in the backward direction and the second scanning reference signal serving as a reference for ending scanning are output. Even in such a case, it is possible to specify whether the scanning direction is the forward direction or the backward direction, and to output a scanning reference signal serving as a reference for scanning start and scanning end in each of the forward direction and the backward direction.

  In the image forming apparatus according to the third aspect of the invention, the forward and backward directions are corrected so as to correct the expansion and contraction of the image formed by the image forming means based on the first scanning reference signal to the fourth scanning reference signal. It may further comprise adjusting means for adjusting the emission of the light beam by the light beam emitting means in the scanning of each light beam in the direction. Thereby, even when the formed image is expanded or contracted due to the variation in scanning of the light beam, the emission of the light beam is adjusted based on the first scanning reference signal to the fourth scanning reference signal, An image can be formed with high accuracy.

  Further, the light deflecting means described above can deflect the light beam so that the light beam is reciprocated by the sine swing of the deflecting surface. Thereby, the light deflection means can be reduced in size.

  As described above, the scanning reference signal output apparatus and the image forming apparatus of the present invention have a simple circuit configuration including a plurality of light receiving elements, a gate signal generation circuit, and a logical product output circuit, and a light beam. Even in the case of reciprocating scanning, it is possible to specify the scanning direction and output the scanning reference signal.

  Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, a case where the present invention is applied to an image forming apparatus will be described as an example.

  As shown in FIG. 1, an image forming apparatus 10 according to the first embodiment of the present invention includes a photosensitive drum 12 that is an image carrier that rotates at a constant speed in the direction of arrow Q in FIG. And an optical scanning device 14 for irradiating the surface of the photosensitive drum 12 with a laser beam based on the data.

  The laser beam emitted from the optical scanning device 14 is irradiated to a predetermined irradiation position A on the photosensitive drum 12 via the reflection mirror 15.

  In the vicinity of the outer periphery of the photosensitive drum 12, the surface of the photosensitive drum 12 is charged with a predetermined charging voltage upstream of the irradiation position A in the rotation direction of the photosensitive drum 12 (in the direction of arrow Q in FIG. 1). A charging unit 16 is provided. In addition, a toner image corresponding to the electrostatic latent image formed by the laser beam irradiated on the surface of the photosensitive drum 12 is disposed on the downstream side in the rotation direction of the photosensitive drum 12 across the irradiation position A of the optical scanning device 14. A developing unit 18 to be formed, a transfer roll 20 for transferring the toner image onto the recording paper P, and a peeling plate 22 for discharging a peeling voltage to the recording paper P in order to facilitate the peeling between the recording paper P and the photosensitive drum 12. And a cleaner 38 for removing residual toner and the like on the surface of the photosensitive drum 12 are sequentially arranged.

  In addition, recording sheets P are stacked at the bottom of the image forming apparatus 10, and these recording sheets P are drawn one by one from the top by a half moon roll 24 and predetermined transported by transport rolls 26, 28 and the like. It is conveyed along the path T. The conveyance path T of the recording paper P is set so as to sequentially pass through a fixing unit 30 including a nip portion N between the photosensitive drum 12 and the transfer roll 20, and a heating roll 32 and a pressure roll 34. Has been.

  Therefore, in this image forming apparatus 10, the surface of the photosensitive drum 12 charged by the charging unit 16 is scanned with a laser beam whose irradiation is controlled based on the image data to be formed, whereby the photosensitive drum. An electrostatic latent image corresponding to the image to be formed is formed on the surface 12. The electrostatic latent image formed here reaches the developing unit 18 by the rotation of the photosensitive drum 12, and a toner image is formed by, for example, negatively charged toner in the developing unit 18. Further, the toner image reaches the nip N between the photosensitive drum 12 and the transfer roll 20 to which a positive high voltage is applied, and the toner image on the photosensitive drum 12 is sufficiently attracted to the transfer roll 20. Similarly, the toner image is transferred to the recording paper P conveyed to the nip portion N. The recording paper P to which the toner image has been transferred is peeled from the photosensitive drum 12 by the peeling discharge by the peeling plate 22 and conveyed to the fixing unit 30. In the fixing unit 30, the toner image is fixed on the recording paper P by the heating roll 32 and the pressure roll 34. The recording paper P on which the toner image fixing process has been completed is peeled off from the heating roll 32 and the pressure roll 34 by the paper peeling finger 36 and discharged to the outside of the image forming apparatus 10 by the transport roll 28 and the like. The surface of the photosensitive drum 12 is cleaned by the cleaner 38 after the transfer of the toner image to the recording paper P is completed, and the remaining toner and the like are removed.

  Further, the image forming apparatus 10 is provided with a control unit 80 for controlling each part of the image forming apparatus 10.

  As shown in FIG. 2, the optical scanning device 14 includes a semiconductor laser 42 that blinks based on image data and emits a laser beam, a collimator lens 44 that converts the laser beam into a parallel beam, and a laser that is converted into a parallel beam. A cylindrical lens 46 that further shapes and emits the beam and an optical deflection element 40 that swings in a sine manner are provided. The flashing of the laser beam emitted from the semiconductor laser 42 is controlled by the control unit 80.

  As shown in FIG. 3, the light deflection element 40 is a reflecting mirror on one side and has a rectangular shape. The light deflection element 40 is used to vibrate the light deflection element 40 in the torsional direction at the center of both edges in the longitudinal direction. A pair of spring portions 50 made of metal or semiconductor material is disposed as an elastic member, and a coil pattern 52 (hereinafter referred to as a drive coil) is formed on the back surface of the light deflection element 40. The drive coil 52 generates a magnetic field having a component in a direction orthogonal to the wiring portion 54 of the drive coil 52 that is parallel to the side edge in the width direction of the light deflection element 40.

  When an alternating current of frequency f flows through the drive coil 52, a force in accordance with Fleming's left-hand rule is generated in a direction perpendicular to the surface of the light deflection element 40 by the magnetic field of the permanent magnet 56 orthogonal to the current direction. The light deflecting element 40 vibrates in the twist direction at the frequency f by the spring portion 50. In this way, the light deflection element 40 swings sinusoidally, and the laser beam reflected by the reflecting mirror is subjected to a reciprocating deflection action sinusoidally.

  Further, the optical scanning device 14 includes an F arc sine θ lens 60 that converges the laser beam so as to be imaged on the photosensitive drum 12. The deflected laser beam is subjected to an optical path refraction action so as to scan the photosensitive drum 12 at a constant speed.

  Further, the optical scanning device 14 is synchronized as a reflection mirror 62 that reflects a part of the laser beam outside the image scanning range, and a scanning reference signal output device that receives and detects the laser beam guided by the reflection mirror 62. A detection device 82 is provided, and among the laser beams deflected and scanned by the optical deflection element 40, the photosensitive drum 12 is scanned if it is within the image scanning range, and a part of the laser beam outside the image scanning range is obtained. The light is guided to the synchronization detection device 82 by the reflection mirror 62.

  Here, when the power of the optical scanning device 14 is turned on, that is, in the initial state, if the laser beam is emitted from the reflecting mirror of the optical deflection element 40, the laser beam is the most forward path of all deflection angles. The laser beam is deflected so as to travel in the forward traveling direction from a position from the side, and the laser beam reaches the reflection mirror 62. At this time, the laser beam is guided to the synchronization detection device 82, and the synchronization detection device 82 receives the laser beam. Thereafter, if the laser beam is emitted as the reflecting mirror of the light deflecting element 40 sine swings, the angle at which the laser beam irradiates the photosensitive drum 12 is reached by the reflecting mirror of the light deflecting element 40. The laser beam is deflected as follows. Further, when the reflecting mirror of the light deflecting element 40 is swung sine, the laser beam is deflected by the reflecting mirror of the light deflecting element 40 so as to switch from the forward traveling direction to the backward traveling direction, and the laser beam scans on the synchronization detection device 82. Then, the laser beam is received by the synchronization detection device 82.

  Further, as shown in FIG. 4, the synchronization detection device 82 includes a two-divided light receiving element PD as a reference position signal output means, and the two-divided light receiving element PD receives a laser beam to be scanned, thereby receiving a reference position. It is composed of a rectangular first light receiving element PD1 and second light receiving element PD2 that output sensor signals as signals. When the laser beam is scanned in the forward direction, the first light receiving element PD1 and the second light receiving element PD2 are arranged side by side in the scanning direction so as to receive the laser beam in this order.

  The synchronization detection device 82 also includes a comparator 88 that compares the sensor signal of the second light receiving element PD2 with the sensor signal of the first light receiving element PD1, and the sensor signal of the second light receiving element PD2 is the first signal. When the level is higher than the sensor signal of the light receiving element PD1, a high level comparison signal C is output.

  The synchronization detection device 82 also includes a comparator 90 that compares the level of the sensor signal of the first light receiving element PD1 with the threshold voltage Vth, and the level of the sensor signal of the first light receiving element PD1 is higher than the threshold voltage Vth. When the level is reached, a high level comparison signal is output. The synchronization detection device 82 includes a gate signal generation circuit 84 that detects a rising edge of the comparison signal output from the comparator 90 and outputs a gate signal having a certain pulse width, and an AND circuit 86. The AND circuit 86 receives the gate signal output from the gate signal generation circuit 84 and the comparison signal C output from the comparator 88, and the logical product output of these signals starts scanning as a scanning reference signal. It is output as a signal. The pulse width of the gate signal output by the gate signal generation circuit 84 exceeds the magnitude from the rise of the sensor signal of the first light receiving element PD1 to the rise of the sensor signal output from the second light receiving element PD2. It has a pulse width.

  Note that the image forming apparatus 10 only needs to have a general configuration and functions of a conventionally known printer and multifunction peripheral, and detailed description of other configurations and general functions of the image forming apparatus 10 is omitted. .

  Next, the operation of the image forming apparatus 10 according to the first exemplary embodiment of the present invention will be described. First, when a user operates a client PC (not shown) to input a print instruction for image data to the image forming apparatus 10 via a network (not shown), the control unit 80 causes the semiconductor to operate based on the image data. The emission of the laser beam from the laser 42 is controlled. The controller 80 controls the driving of the light deflection element 40, the light deflection element 40 swings in a sine and deflects the laser beam from the semiconductor laser 42, and the laser beam is scanned on the photosensitive drum 12. The laser beam is received by the first light receiving element PD1 and the second light receiving element PD2 of the synchronization detecting device 82 via the reflection mirror 62, and sensor signals are output from each of them. At this time, the sine-swinging optical deflection element 40 outputs a sensor signal in each of the forward path and the backward path in order to reciprocate the laser beam.

  Here, when the laser beam is scanned in the forward direction, as shown in FIG. 5A, the sensor signal from the first light receiving element PD1 rises to a higher level than the threshold voltage Vth, and the comparator A high level comparison signal is output from 90, and a gate signal is output by the gate signal generation circuit 84.

  When the sensor signal from the second light receiving element PD2 becomes higher than the sensor signal from the first light receiving element PD1, the comparator 88 outputs a high level comparison signal C and the gate signal is at high level. In addition, when the comparison signal C from the comparator 88 is at the high level, the scanning start signal is output at the high level.

  Further, when the laser beam is scanned in the backward direction, as shown in FIG. 5B, the sensor signal from the second light receiving element PD2 is at a higher level than the sensor signal from the first light receiving element PD1. When the comparator 88 outputs a high level comparison signal C, and the sensor signal from the first light receiving element PD1 is at a higher level than the sensor signal from the second light receiving element PD2, the comparator 88 compares the signal. Signal C falls to a low level.

  When the sensor signal from the first light receiving element PD1 rises to a higher level than the threshold voltage Vth, a high level comparison signal is output from the comparator 90, and a gate signal is output by the gate signal generation circuit 84. When the gate signal is at the high level, the comparison signal from the comparator 88 is at the low level, so that the scanning start signal is at the low level.

  In this way, the gate signal is output based on the sensor signal of the first light receiving element PD1 that first receives the laser beam in the forward scanning, and the sensor signal and the gate of the second light receiving element PD2 that receives light later. By outputting a logical product output with the signal as a scanning start signal, the scanning start signal is output only in the forward scanning with a simple circuit configuration.

  Then, the control unit 80 specifies the scanning start position in the forward direction based on the output scanning start signal, and controls to output a laser beam from the semiconductor laser 42 based on the image data, so that the photoconductor A laser beam is scanned on the drum 12.

  As described above, according to the image forming apparatus according to the first embodiment, the synchronization detection device has a simple circuit configuration including a plurality of light receiving elements, a gate signal generation circuit, and an AND circuit, and Since the scanning start signal is output only when scanning in the forward direction and light is received in the order of the first light receiving element and the second light receiving element, the scanning direction is specified and the scanning is started even when the laser beam is reciprocated. A signal can be output.

  In addition, the use of a light deflection element that swings in a sine manner can contribute to miniaturization of the optical scanning device.

  Further, the main scanning of the laser beam can be performed with high accuracy by starting the main scanning in the forward direction of the laser beam based on the scanning start signal.

  In addition, if the first light receiving element and the second light receiving element do not sequentially receive the laser beam, the scanning start signal is not output, and it is unlikely that the scanning start signal is output due to noise or the like. An image can be formed with high accuracy by scanning the photosensitive member with a laser beam with high accuracy.

  Next, a second embodiment of the present invention will be described. Note that portions similar to those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The second embodiment is different from the first embodiment in that the synchronous detection device is provided with a three-divided light receiving element instead of a two-divided light receiving element.

  As shown in FIG. 6, the synchronization detection apparatus 182 according to the second embodiment includes a three-divided light receiving element PD10 as a reference position signal output unit, and the three-divided light receiving element PD10 receives a scanned laser beam. Thus, the first light receiving element PD11, the second light receiving element PD12, and the third light receiving element PD13 that output sensor signals are configured. When the laser beam is scanned in the forward direction, the first light receiving element PD11, the second light receiving element PD12, and the third light receiving element 13 are arranged side by side in the scanning direction so as to receive the laser beam. Has been.

  The synchronization detection device 182 also includes a comparator 188 that compares the sensor signal of the third light receiving element PD13 with the sensor signal of the second light receiving element PD12, and the sensor signal of the third light receiving element PD13 is the second signal. When the level is higher than the sensor signal of the light receiving element PD12, a high level comparison signal C is output.

  Further, the synchronization detection device 182 includes a comparator 90 that compares the level of the sensor signal of the first light receiving element PD11 and the threshold voltage Vth, a gate signal generation circuit 84, and an AND circuit 86. The gate signal output from the gate signal generation circuit 84 and the comparison signal output from the comparator 88 are input, and a logical product output of these signals is output as a scanning start signal as a scanning reference signal. It has become. The pulse width of the gate signal output by the gate signal generation circuit 84 exceeds the magnitude from the rise of the sensor signal of the first light receiving element PD11 to the rise of the sensor signal output from the third light receiving element PD13. It has a pulse width.

  Next, the operation of the second exemplary embodiment of the present invention will be described.

  First, when the laser beam is scanned in the forward direction, the sensor signal from the first light receiving element PD11 rises to a high level from the threshold voltage Vth as shown in FIG. A high level comparison signal is outputted from the gate signal, and a gate signal is outputted by the gate signal generation circuit 84.

  Then, when the sensor signal from the second light receiving element PD12 becomes high level, and then the sensor signal from the third light receiving element PD13 becomes higher level than the sensor signal from the second light receiving element PD12, the comparator 188. A high-level comparison signal C is output from the scan start signal when the gate signal is at the high level and the comparison signal C from the comparator 188 is at the high level. Is done.

  When the laser beam is scanned in the backward direction, as shown in FIG. 7B, the sensor signal from the third light receiving element PD13 is higher than the sensor signal from the second light receiving element PD12. When the high level comparison signal C is output from the comparator 188 and the sensor signal from the second light receiving element PD12 becomes higher than the sensor signal from the third light receiving element PD13, the comparison is performed from the comparator 188. Signal C falls to a low level.

  When the sensor signal from the first light receiving element PD11 rises to a higher level than the threshold voltage Vth, a high level comparison signal is output from the comparator 90, and a gate signal is output by the gate signal generation circuit 84. . Since the comparison signal C from the comparator 188 is at a low level when the gate signal is at a high level, the scanning start signal is at a low level.

  In this way, the gate signal is output based on the sensor signal of the first light receiving element PD11 that first receives the laser beam in the scanning in the forward direction, and the sensor signal and the gate of the third light receiving element PD13 that receives light later. By outputting a logical product output with the signal as a scanning start signal, the scanning start signal is output only in the forward scanning with a simple circuit configuration, and the first light receiving element PD11 scans the laser beam. Since the second light receiving element PD12 and the third light receiving element 13 are provided as light receiving elements for specifying the position of the laser beam, the gate signal and the sensor signal are provided. In this case, there is a time difference between the two, and it is possible to prevent a malfunction when outputting the logical product of the sensor signal and the gate signal.

  Next, a third embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the part similar to 1st Embodiment and 2nd Embodiment, and description is abbreviate | omitted.

  The third embodiment is different from the first embodiment in that not only the scanning start signal in the forward direction but also the scanning end signal in the backward direction is output.

  As shown in FIG. 8, the synchronization detection device 282 according to the third embodiment includes a two-divided light receiving element PD, a comparator 88 that outputs a comparison signal C1, a comparator 90 that outputs a comparison signal, and a gate signal G1. A gate signal generation circuit 84 for generating and an AND circuit 86 for outputting a forward scanning start signal are provided.

  The synchronization detection device 282 also includes a comparator 288 that compares the sensor signal of the first light receiving element PD1 with the sensor signal of the second light receiving element PD2, and the sensor signal of the first light receiving element PD1 is the second signal. When the level is higher than the sensor signal of the light receiving element PD2, a high level comparison signal C2 is output.

  Further, the synchronization detection device 282 compares the level of the sensor signal of the second light receiving element PD2 with the threshold voltage Vth, and the level of the sensor signal of the second light receiving element PD2 is higher than the threshold voltage Vth. If there is, a high level comparison signal C2 is output. Further, the synchronization detection device 282 detects a rising edge of the comparison signal output from the comparator 290, outputs a gate signal G2 having a certain pulse width, and an AND circuit 286. The AND circuit 286 receives the gate signal G2 output from the gate signal generation circuit 284 and the comparison signal C2 output from the comparator 288, and the logical product output of these signals is used as a backward scan end signal. It is output. The pulse width of the gate signal G2 output by the gate signal generation circuit 284 has a magnitude from the rising edge of the sensor signal of the second light receiving element PD2 to the rising edge of the sensor signal output from the second light receiving element PD2. The pulse width exceeds.

  Next, the operation of the third exemplary embodiment of the present invention will be described.

  First, when the laser beam is scanned in the forward direction, as shown in FIG. 9A, the sensor signal from the first light receiving element PD1 rises to a higher level than the threshold voltage Vth, and the comparator 90 A high level comparison signal is output from the gate signal G1, and the gate signal generation circuit 84 outputs the gate signal G1.

  Further, since the sensor signal from the first light receiving element PD1 is at a higher level than the sensor signal from the second light receiving element PD2, the comparator 288 outputs a high level comparison signal C2.

  When the sensor signal from the second light receiving element PD2 becomes high level and the sensor signal from the second light receiving element PD2 becomes higher level than the sensor signal from the first light receiving element PD1, the comparator 88 outputs high. When the level comparison signal C1 is output, the gate signal G1 is at the high level, and the comparison signal C1 from the comparator 88 is at the high level, the forward scanning start signal is output at the high level. Is done.

  Further, the sensor signal from the second light receiving element PD2 becomes higher than the sensor signal from the first light receiving element PD1, and the comparison signal C2 falls from the comparator 288 to the low level. When the sensor signal from the second light receiving element PD2 rises to a higher level than the threshold voltage Vth, the comparator 290 outputs a high level comparison signal, and the gate signal generation circuit 284 outputs the gate signal G2. The When the gate signal G2 is at the high level, the comparison signal C2 from the comparator 288 is at the low level, so that the backward scanning end signal is at the low level.

  When the laser beam is scanned in the backward direction, as shown in FIG. 9B, the sensor signal from the second light receiving element PD2 rises to a higher level than the threshold voltage Vth, and the comparator 290 A high-level comparison signal is output from, and the gate signal generation circuit 284 outputs the gate signal G2.

  Further, since the sensor signal from the second light receiving element PD2 is at a higher level than the sensor signal from the first light receiving element PD1, the comparator 88 outputs a high level comparison signal C1.

  When the sensor signal from the first light receiving element PD1 becomes high level and the sensor signal from the first light receiving element PD1 becomes higher level than the sensor signal from the second light receiving element PD2, the comparator 288 outputs high. When the level comparison signal C2 is output, the gate signal G2 is at the high level, and the comparison signal C2 from the comparator 288 is at the high level, the return scan end signal is output at the high level. Is done.

  In addition, the sensor signal from the first light receiving element PD1 becomes higher than the sensor signal from the second light receiving element PD2, and the comparison signal C1 falls from the comparator 88 to a low level. When the sensor signal from the first light receiving element PD1 rises to a higher level than the threshold voltage Vth, a high level comparison signal is output from the comparator 90, and the gate signal G1 is output from the gate signal generation circuit 84. The Since the comparison signal C1 from the comparator 88 is at a low level when the gate signal G1 is at a high level, the forward scanning start signal is at a low level.

  In this way, the gate signal G1 is output with reference to the sensor signal of the first light receiving element PD1 that first receives the laser beam in the forward scanning, and the sensor signal of the second light receiving element PD2 that receives light later. The logical product output with the gate signal G1 is output as a scanning start signal in the forward direction, and the gate signal G2 is output with reference to the sensor signal of the second light receiving element PD2 that receives the laser beam later in the scanning in the forward direction. Thus, the output of the logical product of the sensor signal of the first light receiving element PD1 that receives light first in the forward scan and the gate signal G2 is output as the scan end signal in the backward pass, thereby providing a simple circuit configuration. The scanning start signal in the direction and the scanning end signal in the return direction can be separated and output.

  As described above, according to the image forming apparatus of the third embodiment, when the laser beam is scanned in the forward direction so that the first light receiving element and the second light receiving element sequentially receive the laser beam. In order to output the forward scanning start signal and to output the backward scanning end signal when the laser beam is scanned in the backward direction so as to receive the laser beam in the order of the second light receiving element and the first light receiving element. Even when reciprocating scanning is performed, it is possible to specify whether the scanning direction is the forward direction or the backward direction, and to output the forward scanning start signal and the backward scanning end signal.

  In the above embodiment, the case where the synchronization detection device is arranged at the scanning start position in the forward direction has been described as an example. However, the synchronization detection device may be arranged at the scanning end position in the forward direction. In this case, since the forward scanning end signal and the backward scanning start signal are output, the emission of the laser beam may be controlled based on these signals.

  Next, a fourth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the part similar to 1st Embodiment thru | or 3rd Embodiment, and description is abbreviate | omitted.

  The fourth embodiment is different from the first embodiment in that the scanning start signal and the scanning end signal are output in both the forward path and the backward path.

  As shown in FIG. 10, the optical scanning device 314 according to the fourth embodiment is provided with reflection mirrors 62 and 362 that reflect a part of the laser beam outside the image scanning range, and is outside the image scanning range. It is arranged at both ends. Further, a synchronization detection device 282 that receives and detects the laser beam guided by the reflection mirror 62 and a synchronization detection device 382 that receives and detects the laser beam guided by the reflection mirror 362 are provided. Among the laser beams deflected and scanned by 40, the photosensitive drum 12 is scanned if it is within the image scanning range, and a part of the laser beam outside the image scanning range is guided to the synchronization detecting device 282 by the reflecting mirror 62, Further, the light is guided to the synchronization detection device 382 by the reflection mirror 362.

  Here, when the power of the optical scanning device 114 is turned on, that is, in the initial state, if the laser beam is emitted from the reflecting mirror of the optical deflection element 40, the laser beam is the most forward path of all deflection angles. The laser beam is deflected so as to travel in the forward traveling direction from a position from the side, and the laser beam reaches the reflection mirror 62. At this time, the laser beam is guided to the synchronization detection device 382, and the synchronization detection device 382 receives the laser beam. Thereafter, if the laser beam is emitted as the reflecting mirror of the light deflecting element 40 sine swings, the angle at which the laser beam irradiates the photosensitive drum 12 is reached by the reflecting mirror of the light deflecting element 40. The laser beam is deflected as follows. Further, when the reflecting mirror of the light deflection element 40 is swung sine, the laser beam is deflected so as to further advance in the forward traveling direction, and the laser beam reaches the reflecting mirror 362. At this time, the laser beam is guided to the synchronization detection device 382, and the synchronization detection device 382 receives the laser beam.

  In addition, when the forward mirror traveling direction is switched to the backward traveling direction by the reflecting mirror of the light deflection element 40, the laser beam is deflected so that the laser beam travels in the backward traveling direction from the position closest to the backward path of all deflection angles, The laser beam reaches the reflection mirror 362 again. At this time, the laser beam is guided to the synchronization detection device 382, and when the synchronization detection device 382 receives the laser beam and the reflecting mirror of the light deflection element 40 further swings in a sine, the laser beam is further advanced in the backward traveling direction. The laser beam reaches the reflecting mirror 62, and the laser beam is guided to the synchronization detection device 282. The synchronization detection device 282 receives the laser beam.

  As described above, when the laser beam is deflected by the reflecting mirror of the light deflecting element 40 and the laser beam scans on the synchronization detection devices 282 and 382, the synchronization detection devices 282 and 382 receive the laser beam in each of the forward path and the return path. . As shown in FIG. 11, the synchronization detection device 282 receives a laser beam to output a scanning start signal in the forward direction and a scanning start signal in the backward direction, and the synchronization detection device 382 includes the synchronization detection device 282. And receiving a laser beam, it outputs a scanning start signal in the backward direction and a scanning end signal in the forward direction.

  Next, the operation of the fourth exemplary embodiment of the present invention will be described.

  At a predetermined timing such as when the power is turned on, the control unit 80 executes a clock frequency correction processing routine shown in FIG.

  First, in step 400, a laser beam is emitted from the semiconductor laser 42, the laser beam is deflected by the optical deflection element 40, and the laser beam is scanned in the forward path and the backward path, and the forward scanning time T1 and the backward scanning time T2 (FIG. 11). Measure). The forward scanning time T1 is measured by the timing when the forward scanning start signal is output from the synchronization detection device 282 and the timing when the forward scanning end signal is output from the synchronization detection device 382, and the backward scanning time T2 is measured by the synchronization detection device. Measurement is performed based on the timing at which the backward scanning start signal is output from 382 and the timing at which the backward scanning end signal is output from the synchronization detection device 282.

  In step 402, the forward scanning time T1 is compared with a reference value T0 of a predetermined scanning time. The reference value T0 is, for example, a scanning time assumed from the specification of the optical scanning device 314, is experimentally or statistically obtained, and is the same value in the forward path and the backward path. Here, if the forward scanning time T1 is smaller than the reference value T0, in step 404, when the laser beam is scanned in the forward direction, the writing clock frequency that is a reference for the timing at which the semiconductor laser 42 blinks the laser beam is increased. Thus, the expansion of the image formed by the forward scanning is corrected, and the process proceeds to Step 408. If the forward scanning time T1 is larger than the reference value T0, in step 406, the writing clock frequency when scanning the laser beam in the forward direction is adjusted to be reduced, and the image formed by the forward scanning is reduced. And the process proceeds to step 408. If the forward scanning time T1 is equal to the reference value T0, the process proceeds to step 408 without adjusting the writing clock frequency.

  In step 408, the backward scanning time T2 is compared with a predetermined reference value T0. If the backward scanning time T2 is smaller than the reference value T0, the write clock for scanning the laser beam in the backward direction is determined in step 410. Adjustment is made to increase the frequency, the expansion of the image formed by the scanning in the backward direction is corrected, and the clock frequency correction processing routine is completed. If the backward scanning time T2 is larger than the reference value T0, in step 412, the write clock frequency when scanning the laser beam in the backward direction is adjusted to reduce the shrinkage of the image formed by the backward scanning. To complete the clock frequency correction processing routine. If the backward scanning time T2 is equal to the reference value T0, the clock frequency correction processing routine is terminated without adjusting the write clock frequency.

  As described above, according to the image forming apparatus according to the fourth embodiment, each of the two synchronization detection devices is simply composed of a plurality of light receiving elements, two gate signal generation circuits, and two AND circuits. When the laser beam is scanned in the forward direction, the forward scanning start signal and the forward scanning end signal are output, and when the laser beam is scanned in the backward direction, the backward scanning start signal and the backward path are output. In order to output a scanning end signal, even if the laser beam is reciprocally scanned, it is specified whether the scanning direction is the forward direction or the backward direction, and scanning starts and ends in each of the forward direction and the backward direction. Can be output as a reference signal.

  In addition, even when the formed image expands or contracts due to variations in the scanning of the laser beam, the writing clock frequency of the laser beam is adjusted based on the forward scanning start signal and the forward scanning end signal. An image can be formed with high accuracy by adjusting the writing clock frequency of the laser beam based on the backward scanning start signal and the backward scanning end signal.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. 1 is a schematic diagram illustrating a configuration of an optical scanning device according to a first embodiment of the present invention. It is a perspective view which shows the structure of the optical deflection | deviation element concerning the 1st Embodiment of this invention. It is a circuit diagram which shows the structure of the synchronous detection apparatus which concerns on the 1st Embodiment of this invention. It is a time chart which shows the mode of the sensor signal in the synchronous detection apparatus which concerns on the 1st Embodiment of this invention, a comparison signal, a gate signal, and a scanning start signal. It is a circuit diagram which shows the structure of the synchronous detection apparatus which concerns on the 2nd Embodiment of this invention. It is a time chart which shows the mode of the sensor signal in the synchronous detection apparatus which concerns on the 2nd Embodiment of this invention, a comparison signal, a gate signal, and a scanning start signal. It is a circuit diagram which shows the structure of the synchronous detection apparatus which concerns on the 3rd Embodiment of this invention. It is a time chart which shows the mode of the sensor signal in the synchronous detection apparatus which concerns on the 3rd Embodiment of this invention, a comparison signal, a gate signal, an outward scanning start signal, and a backward scanning end signal. It is the schematic which shows the structure of the optical scanning device which concerns on the 4th Embodiment of this invention. It is a time chart which shows the mode of the outward scanning start signal, the outward scanning end signal, the backward scanning start signal, and the backward scanning end signal in the synchronous detection apparatus according to the fourth embodiment of the present invention. 10 is a flowchart showing the contents of a clock frequency correction processing routine executed by an image forming apparatus according to a fourth embodiment of the present invention. It is a perspective view which shows the basic composition of the conventional light beam scanning apparatus. It is an image figure which shows the prior art example which produces | generates a scanning reference signal when a light beam passes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Photosensitive drum 14,114,314 Optical scanning device 40 Optical deflection element 42 Semiconductor laser 62,362 Reflection mirror 80 Control part 82,182,282 Synchronization detection device 84,284 Gate signal generation circuit 86,286 and Circuit 382 Synchronization detection device G1, G2 Gate signal PD Two-divided light receiving element PD1, PD2, PD11, PD12, PD13 Light receiving element PD10 Three-divided light receiving element T0 Reference value T1 Forward scanning time T2 Return scanning time

Claims (6)

A reference position signal output means for arranging a plurality of light receiving elements that output a reference position signal by receiving a scanned light beam and arranged in a scanning direction of the light beam so as to receive the light beam in a predetermined order; ,
When the reference position signal is first output from the light receiving element arranged to receive the light beam, the light beam is arranged to be received after the light receiving element from the rising edge of the reference position signal. A gate signal generation circuit for generating a gate signal having a pulse width exceeding the magnitude until the rising edge of the reference position signal output from the light receiving element;
A logical product of the gate signal generated by the gate signal generation circuit and the reference position signal output from the light receiving element arranged to receive the light beam after the light receiving element is output as a scanning reference signal. A logical product output circuit,
A scanning reference signal output device. A light beam emitting means for emitting a light beam according to image data;
Light deflecting means for deflecting the light beam so that the light beam reciprocally scans;
A light receiving element that outputs a reference position signal by receiving the light beam is configured to receive the light beam in a predetermined order when the light beam is scanned in either the forward direction or the backward direction. A plurality of reference position signal output means arranged side by side in the scanning direction of the light beam,
When the reference position signal is first output from the light receiving element arranged to receive the light beam, the light beam is arranged to be received after the light receiving element from the rising edge of the reference position signal. A gate signal generating circuit for generating a gate signal having a pulse width exceeding the magnitude until the rising edge of the reference position signal output from the light receiving element, and the gate signal generated by the gate signal generating circuit and the light receiving element A scanning reference signal output device including a logical product output circuit that outputs a logical product of the reference position signal output from the light receiving element arranged to receive the light beam later as a scanning reference signal;
Image forming means for forming an image by causing the light beam emitting means to emit the light beam based on the scanning reference signal output by the logical product output circuit;
An image forming apparatus including: The scanning reference signal output device comprises:
Finally, when the reference position signal is output from the light receiving element arranged to receive the light beam, the light beam is arranged to be received before the light receiving element from the rising edge of the reference position signal. A second gate signal generating circuit for generating a second gate signal having a pulse width exceeding the magnitude until the rising edge of the reference position signal output from the light receiving element; and generated by the second gate signal generating circuit A logical product of the second gate signal thus generated and the reference position signal output from the light receiving element disposed so as to receive the light beam before the light receiving element is output as a second scanning reference signal. A second logical product output circuit,
The image forming apparatus according to claim 2, wherein the image forming unit forms the image by causing the light beam emitting unit to emit the light beam based on the scanning reference signal and the second scanning reference signal. A light beam emitting means for emitting a light beam according to image data;
Light deflecting means for deflecting the light beam so that the light beam reciprocally scans;
A first light receiving element that outputs a first reference position signal indicating a scanning start position in the forward direction by receiving the scanned light beam is arranged in a predetermined order when the light beam is scanned in the forward direction. A plurality of first reference position signal output means arranged in the scanning direction of the light beam so as to receive the light beam;
When the first reference position signal is output from the first light receiving element arranged to receive the light beam first, the rising edge of the first reference position signal causes the first light receiving element to A first gate signal having a pulse width exceeding a magnitude until the rising edge of the first reference position signal output from the first light receiving element arranged to receive the light beam later is generated. Gate signal generation circuit,
The first gate signal generated by the first gate signal generation circuit and the first light output from the first light receiving element arranged to receive the light beam after the first light receiving element. A first logical product output circuit that outputs a logical product of the first reference position signal as a first scanning reference signal that serves as a reference for starting scanning in the forward direction;
Finally, when the first reference position signal is output from the first light receiving element arranged to receive the light beam, the rising edge of the first reference position signal causes the first light receiving element to A second gate signal having a pulse width exceeding a magnitude until the rising edge of the first reference position signal output from the first light receiving element arranged to receive the light beam previously is generated. Two gate signal generation circuits, and the first gate signal generated by the second gate signal generation circuit and the first light receiving element before the first light receiving element. A first logical product output circuit that outputs a logical product with the first reference position signal output from the light receiving element as a second scanning reference signal serving as a reference for the end of scanning in the backward direction. Scanning reference signal output device and ,
A second light receiving element that outputs a second reference position signal indicating a scanning end position in the forward direction by receiving the light beam is arranged in a predetermined order when the light beam is scanned in the forward direction. Second reference position signal output means arranged side by side in the scanning direction of the light beam so as to receive the beam;
When the second reference position signal is output from a second light receiving element arranged to receive the light beam for the first time, the rising edge of the second reference position signal causes the second light receiving element to A third gate signal having a pulse width exceeding the magnitude until the rise of the second reference position signal output from the second light receiving element arranged to receive the light beam later is generated. Gate signal generation circuit,
The third gate signal generated by the third gate signal generation circuit and the second light receiving element arranged to receive the light beam after the second light receiving element are output from the second light receiving element. A third logical product output circuit that outputs a logical product of the two reference position signals as a third scanning reference signal serving as a reference for the end of scanning in the forward direction;
Finally, when the second reference position signal is output from the second light receiving element arranged so as to receive the light beam, the rising edge of the second reference position signal causes the second light receiving element to A fourth gate signal having a pulse width exceeding the magnitude until the rising edge of the second reference position signal output from the second light receiving element previously arranged to receive the light beam is generated. 4 gate signal generation circuit, and the second gate signal generated by the fourth gate signal generation circuit and the second light receiving element disposed so as to receive the light beam before the second light receiving element. A second AND output circuit that outputs a logical product with the second reference position signal output from the light receiving element as a fourth scanning reference signal serving as a reference for starting scanning in the backward direction. Scanning reference signal output device and ,
Image forming means for forming an image by causing the light beam emitting means to emit the light beam based on the first scanning reference signal to the fourth scanning reference signal;
An image forming apparatus including:   Based on the first scanning reference signal to the fourth scanning reference signal, scanning of the light beam in each of the forward direction and the backward direction so as to correct expansion and contraction of an image formed by the image forming unit. The image forming apparatus according to claim 4, further comprising an adjusting unit that adjusts the emission of the light beam by the light beam emitting unit.   6. The image forming apparatus according to claim 2, wherein the light deflection unit deflects the light beam so that the light beam is reciprocally scanned by a sine swing of a deflection surface. 7.

Images