JP2006154013A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner capable of limiting the state where light leaks without providing such an independent detector as a detection switch on the door or the like of an apparatus side via a wiring when the light quantity of respective light beams emitted from a light source is adjusted. <P>SOLUTION: A reference voltage Vref and an output signal of a light quantity monitor sensor 42 for emitted light quantity are inputted to a laser diode (LD) drive circuit 52 for controlling the light quantity of the LD, and a light quantity control part 54 controls the light beams so as to have a predetermined light quantity on the basis of the difference between an output signal and the reference voltage Vref. The output signal is inputted also into an abnormality detection circuit 58, an abnormal signal is outputted when a low light quantity light beam is detected and a stop circuit 60 stops the operation of the light quantity control part 54. Thus, an abnormal light emitting due to a failure in a light quantity adjustment does not occur even when a component in an optical scanner enters into the upstream side of the light quantity monitor sensor 42. Further, a light beam as a leaked light is not emitted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical scanning device that scans a surface to be scanned with a plurality of light beams emitted from a light source having a plurality of light emitting points.

  In recent laser beam printers, a laser light source (for example, a surface emitting laser light source) that emits a plurality of light beams from a plurality of light emitting points has been used in order to perform high-speed and high-density image formation. A laser light source that emits a plurality of light beams may have different light emission amounts depending on the position of each light emitting point. For this reason, the light amounts emitted from the plurality of light beams may be uneven. For this reason, in order to eliminate the occurrence of image defects such as uneven density and horizontal streaks, where the amount of light on the scanning surface differs for each light beam, a method of offsetting the difference in the amount of light on the surface to be scanned with multiple mirrors is proposed. (For example, refer to Patent Document 1).

  In this way, when the light beam is folded back by a plurality of mirrors, when an obstacle that blocks the optical path enters, the reflected light from the obstacle deviates from the optical path at the time of design and leaks light that is emitted to the outside of the optical scanning device. May occur. This leaked light is unnecessary for operators such as service personnel and users, and is preferably turned off.

For this reason, a service person or a user monitors the open / close state of the open / close lid by providing an interlock mechanism on the open / close lid provided in the housing when performing internal inspection or maintenance (for example, Patent Document 2). reference). This interlock mechanism detects the opening of the open / close lid during operation and mechanically cuts off the supply of power. Thereby, when the opening / closing lid is opened, it is possible to turn off the leaked light.
JP 2002-23083 A JP 2000-153955 A

  However, when the laser light source is controlled in conjunction with the interlock mechanism, it is necessary to provide both the configuration for turning off the laser light source and the interlock mechanism, and the portion including the apparatus main body and the laser light source. Wiring is necessary. This goes against the recent miniaturization and simplification of the device, resulting in a complicated device and complicated assembly work.

  The present invention has been made in consideration of the above-described facts, and an object thereof is to provide an optical scanning device that can suppress leakage light with a simple configuration.

  In order to achieve the above object, an optical scanning device of the present invention includes a light source that emits a plurality of light beams, a light amount sensor that reflects a part of the light beams emitted from the light sources and detects the light amount of the light beams, and Deflection means for deflecting the light beam emitted from the light source toward the scanned surface, and a plurality of light beams deflected by the deflecting means to refract the light beam and to enter the scanned surface and the scanning end detection sensor. An optical system including a mirror, and when adjusting the amount of light beam emitted from the light source, the amount of light beam detected by the light amount sensor is less than a predetermined value And detecting means for detecting a case as an abnormal light emission state, and limiting means for restricting emission of the light beam from the light source when the detection means detects the abnormal light emission state.

  In the optical scanning device of the present invention, the plurality of light beams emitted from the light source are deflected by the deflecting means toward the surface to be scanned, and are then diffracted multiple times by the plurality of mirrors to be scanned surface or scanning end detection sensor. Is incident on. A part of the light beam emitted from the light source is reflected and incident on a light amount sensor that detects the light amount of the light beam.

  When an obstacle that blocks an optical path from the light source to the light quantity sensor enters, there may be a case where light reflected from the obstacle is leaked to the outside of the optical scanning device. Therefore, when adjusting the light amount of each light beam emitted from the light source, the detection unit detects a case where the light amount of the light beam detected by the light amount sensor is less than a predetermined value as an abnormal light emission state. That is, in order to adjust the light amount, for example, a light beam is emitted so as to obtain a light amount equal to or greater than a predetermined value required at the time of image formation. Then, the light quantity sensor detects the light quantity of each light beam emitted from the light source. When the light quantity is less than a predetermined value, there is some abnormality including a situation in which leakage light is generated on the incident side from the light quantity sensor. Is predicted. This state is detected as an abnormal light emission state, and the emission of the light beam from the light source is limited by the limiting means. As a result, it is possible to limit the state in which light leakage occurs in the optical scanning device without providing a separate detector such as a detection switch on the device-side door or the like via a wiring, thereby providing a comfortable environment for the operator. can do.

  The limiting means stops emission of the light beam from the light source.

  When the emission of the light beam from the light source is limited by the limiting means, it is most effective to stop the emission of the light beam from the light source. By stopping the emission of the light beam, the light beam is not emitted from the light source, and no leak light is generated.

  The detecting means detects the total number of light beams having a light amount of the light beam less than a predetermined value, and detects an unstable light emission state when the total light amount of the light beam corresponding to the detected number is less than a specified value, The limiting means does not limit the emission of the light beam from the light source when the unstable light emission state is detected.

  When a plurality of light beams are emitted, when each light beam is weak, it is possible to determine the permissible range up to the total light amount of the light beam group in which the plurality of light beams are gathered as having no influence as leakage light. There is a case. For example, the light quantity and emission time defined in “Class 1” as the exposure limit of laser products can be determined as the allowable range.

  Therefore, the detecting means detects the total number of light beams having a light beam quantity less than a predetermined value, and detects the unstable light emission state when the total light beam quantity corresponding to the detected number is less than a specified value. Based on the detection result, the limiting means does not limit the emission of the light beam from the light source when the unstable light emission state is detected. As a result, a plurality of light beams can be emitted within an allowable range that does not affect the leakage light.

  The detecting means detects the total number of light beams whose light beam intensity is less than a predetermined value, and detects an abnormal light emission state when the total light beam intensity corresponding to the detection number is equal to or greater than a predetermined value. To do.

  As described above, when the allowable range that does not affect the leaked light is exceeded, the probability that the leaked light is generated is high. Therefore, leakage light is generated by detecting the total number of light beams whose light beam amount is less than a predetermined value and detecting the abnormal light emission state when the total light beam amount corresponding to the detected number is equal to or greater than a specified value. Even in this case, it is possible to reliably limit the leakage light.

  The optical system includes a plurality of mirrors that refract a plurality of light beams deflected by the deflecting unit and enter a plurality of scanned surfaces.

  The optical scanning device of the present invention is suitable for use in an image forming apparatus, and the image forming apparatus may be either a single color image or a multicolor image. When forming a multicolor image, it is easy to provide an optical scanning device for each color as the optical scanning device. On the other hand, when downsizing the apparatus, it is preferable to share parts. Therefore, the optical system of the optical scanning device is configured to include a plurality of mirrors that are incident on a plurality of scanned surfaces. Thus, for example, when an optical scanning device is configured for multicolor image formation, a light beam can be incident on a surface to be scanned corresponding to each color, and a single light amount detector can be used for each color. Can do.

  As described above, according to the present invention, when the light quantity of each light beam emitted from the light source is adjusted, the light quantity sensor detects and the light beam emission from the light source is limited based on the detection result. There is an effect that it is possible to limit the state in which leakage light occurs in the optical scanning device without providing a separate detector such as a detection switch on the device-side door or the like via wiring.

  Embodiments of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, in a laser beam printer 12 having an optical scanning device 10 of the present invention, a charging unit 16 and a developer are sequentially developed around the photosensitive member 14 in the rotation direction of the photosensitive member 14 (clockwise direction in the figure). A unit 18, a transfer unit 20, and a cleaner unit 22 are arranged. An intermediate transfer belt 24 is conveyed between the photoconductor 16 and the transfer unit 20. The charging unit 16 is disposed above the photoreceptor 14. The optical scanning device 10 is disposed above the charging unit 16 and emits a light beam to the photosensitive member 14 from between the charging unit 16 and the developing unit 18.

  In this laser printer 12, first, the photosensitive member 14 is uniformly charged by the charging unit 16, and the charged surface of the photosensitive member 14 is scanned with a plurality of light beams by the optical scanning device 10 to form a latent image. Then, the latent image on the photoconductor 14 is developed with toner by the developing unit 18, and the toner image on the photoconductor 14 is transferred to the intermediate transfer belt 24 by the transfer unit 20. Then, untransferred residual toner remaining on the photosensitive member 14 without being transferred to the intermediate transfer belt 24 is removed from the photosensitive member 14 by the cleaner unit 22.

  The optical scanning device 10 of the present embodiment includes a multi-spot laser diode (hereinafter referred to as MSLD) 26 in which a plurality of laser diodes are arranged vertically and horizontally. As shown in FIG. 6, as an example of the MSLD 26, there are 32 laser diodes (LDs) arranged in four rows of light emitting points, and the pitch in the sub-scanning direction (for example, 10.6 μm) The resolution at the time of image formation is determined by the magnification of the optical system. The MSLD 26 corresponds to the light source of the present invention.

  As shown in FIGS. 2 to 4, in the optical scanning device 10, the light exiting side of the MSLD 26 has passed through a collimator lens 28 and a collimator lens 28 that convert a plurality of light beams emitted from the MSLD 26 into parallel light. A cylindrical lens 30 that condenses the light beam in the sub-scanning direction, and a rotary polygon mirror 32 that deflects the light beam condensed by the cylindrical lens 30 are sequentially arranged. On the deflection side of the rotary polygon mirror 32, an Fθ lens 34 that collects the light beam deflected by the rotary polygon mirror 32, and a plurality of light beams collected by the Fθ lens 34 are reflected back and incident on the photosensitive member 14. A mirror group 38 composed of a plurality of mirrors 36 is disposed in order. The photosensitive member 14 is disposed on the exit side of the mirror group 38, and the light beam reflected by the final mirror 36 is interposed between the final mirror 36 and the photosensitive member 14 of the plurality of mirror groups 38. A passing cover glass 39 is provided.

  The optical scanning device 10 of the present embodiment is configured to scan a plurality (two) of the photoreceptors 14 with the light beam of the MSLD 26. That is, the mirror group 38 including a plurality of mirrors 36 includes a mirror 36A in charge of the first photoconductor 14A and a mirror 36B in charge of the second photoconductor 14B. The first photoconductor 14A and the second photoconductor 14B correspond to the colors of the multicolor image. The light beam reflected by the mirror 36A in charge of the first photoconductor 14A passes through the first cover glass 39A and reaches the first photoconductor 14A. The light beam reflected by the mirror 36B in charge of the second photoconductor 14B passes through the second cover glass 39B and reaches the second photoconductor 14B (see FIG. 3). In the following description, the photoconductor 14 and the mirror 36 will be collectively referred to except when a difference is described for a plurality of photoconductors.

  In addition, the optical scanning device 10 receives a light beam that passes through a predetermined position outside the image forming area and detects the writing timing of the light beam, and a light toward the SOS sensor 41. And an SOS pickup mirror 43 that turns the beam back (see FIG. 4). Further, a single sensor is also used as a plurality of light beam detection sensors so that a plurality of light beams are incident on the SOS sensor 41. The plurality of light beams incident on the SOS sensor 41 may be incident simultaneously, or may be synchronous incident incident while synchronizing with a clock or the like. In this case, any configuration may be used as long as the synchronization timing is detected by the SOS sensor 41 and the deviation of the scanning line writing position can be suppressed.

  Further, as shown in FIG. 5, the optical scanning device 10 is reflected by the half mirror 40 that reflects a part of the light beam that has passed through the collimator lens 28 to the side opposite to the traveling direction of the light beam, and the half mirror 40. A light amount monitor sensor 42 that receives the light beam and detects the light amount of the light beam is provided. Since the light quantity monitor sensor 42 is provided on the upstream side of the rotary polygon mirror 32, it can always detect without being influenced by the deflection (scanning) by the rotary polygon mirror 32.

  The rotary polygon mirror 32 of the present embodiment corresponds to the deflecting means of the present invention, and the SOS sensor 41 corresponds to the scanning end detection sensor. A system formed by optical elements such as a mirror from the rotary polygon mirror 32 to the cover glass 39 corresponds to the optical system of the present invention.

  The optical scanning device 10 according to the present embodiment includes a control circuit 50 (see FIG. 1). The control circuit 50 is a circuit that controls the driving of the optical scanning apparatus 10 and includes a computer. Further, the control circuit 50 includes an LD drive circuit for driving a plurality of light beams emitted from the MSLD 26, particularly for controlling the amount of light.

  As shown in FIG. 7, an LD drive circuit 52 for performing light amount control for one LD receives a reference voltage Vref set in advance as a reference light amount of a light beam emitted from the MSLD 26, and the light amount. The monitor sensor 42 and the MSLD 26 are connected. The LD drive circuit 52 includes an amplification circuit 56 that amplifies and outputs a detection signal of the light amount monitor sensor 42, and a light amount control unit 54 that controls driving (light amount) of the MSLD 26. The light quantity control unit 54 is a so-called auto power control (APC) circuit that compares the voltage of the detection signal of the light quantity monitor sensor 42 with the reference voltage Vref and controls the MSLD 26 to emit a light beam having a predetermined light quantity. is there.

  The light amount control may be performed at any time, but is generally performed at a time other than image recording (scanning outside the image forming area). This time is generated as an APC signal and input to the LD drive circuit 52. The light quantity control unit 54 can be operated by inputting the APC signal. Note that a signal obtained by superimposing the APC signal on the reference voltage Vref may be input to the LD drive circuit 52 and used as a single signal.

  The input side of the abnormality detection circuit 58 is connected between the light quantity control unit 54 and the amplification circuit 56, that is, the output side of the amplification circuit 56. The output side of the abnormality detection circuit 58 is connected to the light quantity control unit 54 via the stop circuit 60. In addition, an APC signal is input to the abnormality detection circuit 58.

  The abnormality detection circuit 58 of the present embodiment corresponds to the detection means of the present invention, and the stop circuit 60 corresponds to the restriction means.

  The abnormality detection circuit 58 is a circuit for detecting a predetermined voltage such as a window comparator, and a voltage output corresponding to a predetermined light amount of the light beam emitted from the MSLD 26 at a voltage level near the reference voltage Vref is output from the light amount monitor sensor 42. It is detected whether it was obtained as a signal. The abnormality detection circuit 58 receives an APC signal, and the abnormality detection circuit 58 detects an abnormality only when the APC signal is input. For example, when the MSLD 26 abnormally emits light and becomes a high light amount light beam, or when the light beam is not incident on the light amount monitor sensor 42 and becomes a low light amount light beam, the output signal of the amplification circuit 56 is the upper limit value or the lower limit value. Value. Therefore, an abnormality can be detected by detecting these upper limit value or lower limit value. This detection result (abnormal signal) is output to the stop circuit 60.

  The stop circuit 60 is a circuit that stops the operation of the light quantity control unit 54, that is, stops the emission of the light beam from the MSLD 26. In the example of FIG. 7, the output side of the stop circuit 60 is connected to the light amount control unit 54. In this example, it is assumed that the light amount control unit 54 has an input end (operation stop input end) that accepts stop of the light amount control.

  That is, when an abnormality is detected in the abnormality detection circuit 58, an abnormality signal is output to the stop circuit 60, and the stop circuit 60 outputs a stop signal to the operation stop input terminal of the light quantity control unit 54 in response to the input abnormality signal. . As a result, the operation of the light quantity control unit 54 is stopped so that the emission of the light beam from the MSLD 26 is stopped.

  Note that application examples of the stop circuit 60 include the following. The first application example is a power cutoff of the LD drive circuit 52. That is, the LD drive circuit 52 is supplied with power for driving. A switch is provided in a power supply line for supplying the power, and the power supply is cut off by turning off the switch. As a result, the emission of the light beam from the MSLD 26 is stopped. This power shutdown may be performed by an individual circuit (only the light amount control unit 54). The return process can be performed by a separate operation such as initialization or reset of the entire apparatus. The second application example is to set the reference voltage Vref to a predetermined value (for example, 0 V) at which no light beam is emitted from the MSLD 26. In this case, a switching unit for switching to a predetermined value may be provided on the input side of the reference voltage Vref of the light amount control unit 54, and the stop circuit 60 may control the switching unit.

  The optical scanning device 10 of the present embodiment includes an MSLD 26 having 32 LDs. For this reason, as shown in FIG. 8, the control circuit 50 controls the LD drive circuit 52 (FIG. 7) for each LD of the MSLD 26 so as to individually control 32 channels (LD drive circuits 52-1 to 52-1). 52-32). That is, the MSLD 26 is composed of 32 laser diodes (FIG. 6), and can control the light quantity of each LD. The individual circuits of these 32 channels may be controlled by the control circuit 50 so that the light amount adjustment is performed by individually controlling the blinking sequentially, or the light amount adjustment may be performed by simultaneously controlling the blinking of a predetermined number of LDs.

  Next, the operation of the optical scanning device 10 according to the present embodiment will be described.

  The optical scanning device 10 performs light amount adjustment of the light beam emitted from the MSLD 26 at a predetermined time (for example, timing other than the time of image exposure) by the control circuit 50. Specifically, the light amount adjustment is executed while individually controlling the light amount of the LD included in the MSLD 26.

  First, the control circuit 50 outputs an APC signal to the LD drive circuit 52 in order to execute the light amount adjustment. The LD drive circuit 52 designates 1 LD of the MSLD 26 (for example, 1CH), and the light amount control unit 54 outputs a drive signal for driving the LD for light amount adjustment to the MSLD 26. A reference voltage Vref set in advance for the MSLD 26 to emit a light beam having a predetermined light amount is input to the LD drive circuit 52. The reference voltage Vref corresponds to the output signal of the light quantity monitor sensor 42. In the light quantity control unit 54, the difference value between the output signal of the light quantity monitor sensor 42 amplified by the amplifier circuit 56 and the reference voltage Vref is a predetermined value (for example, about The drive signal (for example, current value) of the MSLD 26 is increased or decreased until it becomes zero. By repeating this process, the light amount adjustment of all the LDs of the MSLD 26 is completed.

  Here, when the apparatus is moved or vibration is given to the apparatus, the parts may move inside the optical scanning apparatus 10 or the parts may be damaged. When the moved or damaged part enters the upstream side of the light amount monitor sensor 42 in the optical path of the light beam emitted from the MSLD 26, the light beam propagates through an unintended optical path (or an unexpected optical path) at the time of design. The light beam that has propagated through this unintended optical path has the possibility of being emitted outside the optical scanning device 10 as leakage light.

  That is, the optical scanning device 10 of the present embodiment is configured separately from the MSLD 26 by providing the light quantity monitor sensor 42 of the MSLD 26 on an optical path branched from the emission optical path of the MSLD 26. Therefore, the optical path on the upstream side of the light quantity monitor sensor 42 is an independent optical path, and if a part or the like enters the optical path, a problem occurs in the light quantity adjustment. Further, if the optical path of the reflected light from the entry component is directed to the outside of the apparatus, the light beam is emitted to the outside of the optical scanning apparatus 10.

  Therefore, in the present embodiment, during the light amount adjustment (APC operation) of the MSLD 26, the output signal of the light amount monitor sensor 42 is monitored to predict the occurrence of leakage light, and the light beam from the MSLD 26 is predicted from the prediction result. Stop the injection. That is, the output signal of the light amount monitor sensor 42 amplified by the amplifier circuit 56 is input to the abnormality detection circuit 58, and the abnormality detection circuit 58 sets the predetermined light amount of the light beam emitted from the MSLD 26 according to the voltage level in the vicinity of the reference voltage Vref. It is detected whether or not a corresponding voltage output is obtained as an output signal of the light quantity monitor sensor 42. For example, when the abnormal light emission of the MSLD 26 or the light beam is not incident on the light quantity monitor sensor 42, the abnormality is detected by detecting that the output signal of the amplifier circuit 56 becomes the upper limit value or the lower limit value.

  When abnormality is detected, an abnormality signal is output to the stop circuit 60, and the stop circuit 60 stops the operation of the light quantity control unit 54. Thereby, the emission of the light beam from the MSLD 26 is stopped.

  Thus, the output signal of the light quantity monitor sensor 42 is monitored, and when an abnormality is detected, the emission of the light beam from the MSLD 26 is stopped. As a result, even if a component that has moved or is damaged inside the optical scanning device 10 enters the upstream side of the light amount monitor sensor 42 in the optical path of the light beam emitted from the MSLD 26, the light amount adjustment failure Abnormal light emission due to will not occur. In addition, a light beam traveling toward the outside of the optical scanning device 10 is not emitted as reflected light by a component entering the optical path, that is, leakage light.

  In the above embodiment, the case where the LD drive circuit 52 has 32 channels of individual LD drive circuits and each has an abnormality detection circuit or the like has been described. When it is complicated to have these abnormality detection circuits individually, it is possible to configure only one abnormality detection circuit or the like. FIG. 9 shows an example having one abnormality detection circuit 58 and stop circuit 60 for the MSLD 26.

  The LD drive circuit 52 shown in FIG. 9 includes individual circuits (light quantity control units 54-1 to 54-32) of 32 channels for each LD of the MSLD 26 as the light quantity control unit 54. The output signal of the light amount monitor sensor 42 is input to the abnormality detection circuit 58 via the amplifier circuit 56, and the stop circuit 60 outputs a signal for stopping or maintaining the light amount control unit 54 according to the result.

  The operation of the LD drive circuit 52 of FIG. 9 is the same as that of the above embodiment, but is different in that the abnormality is not detected individually by the light quantity control unit 54 but by a single abnormality detection circuit 58. Since the light amount adjustment is performed individually for 32 channels, it is possible to share the light amount.

  By the way, there is a case where a single light beam is a weak light amount and may not be treated as leakage light. However, a light source that emits a plurality of light beams, such as the MSLD 26, may emit a plurality of light beams at the same time, and the total light amount may be a light amount sufficient for leaking light depending on the number used.

  That is, when the number of light beams increases, the specified value changes corresponding to the number. For example, when the amount of light is allowed up to 566 μW when normally lit (class 1), when one is about 100 μW, up to five lasers (light beams) is in the allowable range.

  As for the MSLD 26 used in the optical scanning device 10, laser safety is one that can be adopted as a reference as leakage light. In this laser safety, the exposure limit of light beam exposure is defined as energy. For example, the reference value that is a problem in laser safety is 5.04 mJ (10 seconds or less). Considering this value with a laser having a total light amount of 3 mW, an emission time of 0.168 seconds is allowed.

  Therefore, by extending the above-described abnormality detection to the number of light beams, the MSLD 26 can be used to the maximum extent possible.

  When anomaly detection is extended to the number of light beams, it is necessary to measure the number of light beams. Here, assuming that the abnormality detection circuit 58 of FIG. 9 has a control unit having a computer configuration, the abnormality detection circuit 58 executes the processing routine shown in FIG. In this case, it is preferable that the abnormality detection circuit 58 individually outputs a light amount adjustment instruction signal to each channel of the light amount control unit 54.

  In step 100 of FIG. 10, initialization for starting light amount adjustment (n = 0: n is a variable indicating the number of light beams) is performed, and in the next step 102, light amount adjustment is instructed for one LD in the MSLD 26. To do. In response to this instruction, the light amount control unit 54 operates a light amount control unit (for example, 1CH) for any one LD to cause the LD to emit light. By this light emission, a light beam is emitted and incident on the light amount monitor sensor 42.

  In the next step 104, the light quantity measurement (value I) is performed by reading the output signal that is the light quantity value of the light beam incident on the light quantity monitor sensor 42. In the next step 106, it is determined whether I <Ith. This determination is to determine whether or not the light amount of the target light beam has reached the light amount corresponding to the reference voltage Vref. Therefore, the value Ith is an output value of the light quantity monitor sensor 42 when a light quantity corresponding to the reference voltage Vref is incident. This output value can define an allowable range.

  If the result in Step 106 is negative, it is assumed that there is a possibility that an intruding object exists on the optical path of the current LD on the upstream side of the light amount monitor sensor 42 without obtaining the predetermined light amount. Increment variable n. On the other hand, if the result in step 106 is affirmative, the process proceeds to step 110 as it is.

  The above light quantity measurement processing is executed for all the LDs of the MSLD 26. When the execution is completed (Yes in Step 110), it is determined in Step 112 whether n> n0. The constant n0 is the number of light beams whose total light amount is sufficient for the leaked light, and the number is predetermined. If the result in step 112 is affirmative, there is a possibility that leakage light may be generated. Therefore, the process proceeds to step 116 to shift to the abnormality detection mode and output an abnormality detection signal. The anomaly detection mode is a weak light amount with a single light beam, and safety is ensured even if it becomes leaked light, but safety is impaired when it becomes leaked light by combining multiple light beams. This is a state where an environment that is expected to be detected is detected. In this abnormality detection mode, by outputting an abnormal signal to the stop circuit 60, the stop circuit 60 outputs a stop signal to the light amount control unit 54. As a result, the emission of the light beam from the MSLD 26 is stopped.

  When the stop signal of the stop circuit 60 is output, the stop signal is output to the light amount control units 54 (54-1 to 54-32) of all the LDs included in the light amount control unit 54, and the entire light beam is emitted from the MSLD 26. It may be stopped or only the corresponding LD may be stopped. Stopping only the corresponding LD can be achieved by independent wiring from the stop circuit 60 to the light amount control unit of each channel. In addition, when the light quantity control unit 54 grasps the LD whose light quantity is being adjusted, and receives the notification from the stop circuit 60 by the light quantity control unit 54-i (1 ≦ i ≦ 32) of the currently grasped LD, It can also be achieved by stopping sequentially.

  On the other hand, if the result in step 112 is negative, it can be predicted that there is a possibility of leakage light, but safety can be ensured. Therefore, the process proceeds to step 114, and the process proceeds to the prediction mode without outputting an abnormality detection signal. End the routine. Prediction mode means that the total light quantity of multiple light beams is a weak light quantity, and safety is ensured even if it becomes leaking light at the present time, but it is predicted that it will become leaking light that will impair safety in the future. The state where the environment to be detected is detected. In this prediction mode, since no abnormal signal is output to the stop circuit 60, the light quantity control unit 54 continues normal operation. In addition, when the request | requirement which ensures more safety | security increases, the process similar to the said abnormality detection mode can be performed in prediction mode.

  As described above, the number of light beams of the LD that is highly likely to be abnormal is measured, and the abnormality is detected using the number of light beams that matches the total light amount determined in consideration of safety as a threshold. Even if a part that has moved or is broken inside the optical fiber 10 enters the upstream side of the light quantity monitor sensor 42 in the optical path of the light beam emitted from the MSLD 26, the MSLD 26 can be used when safety can be ensured. Can operate. For this reason, the MSLD 26 can be used as effectively as possible.

  As described above, the optical scanning device 10 according to the present embodiment detects an abnormality by monitoring the output signal of the light quantity monitor sensor 42 when adjusting the light quantity of the light beam emitted from the MSLD 26 without providing an external switch. The emission of the light beam from the MSLD 26 is stopped at the above time. As a result, it is possible to execute the countermeasure for suppressing the leakage light by the optical scanning device 10 alone. In addition, since the number of light beams corresponding to the total light quantity serving as a safety standard is used as a threshold for determination of light beam emission stop, leakage light is suppressed while ensuring safety, and the MSLD 26 is efficiently used. be able to.

It is a figure which shows schematic structure of a color laser printer provided with the optical scanning device of this embodiment. It is a perspective view which shows the optical scanning device of this embodiment. It is a side view which shows the outline of the optical scanning device of this embodiment. It is a perspective view which shows the optical scanning device of this embodiment. It is a top view which shows the outline of the optical scanning device of this embodiment. It is an external view of MSLD. FIG. 3 is a conceptual block diagram of an LD drive circuit for performing LD light amount control according to the embodiment of the present invention. It is a block diagram which shows an example which has an abnormality detection circuit and a stop circuit in LD drive circuit for every LD of MSLD. It is a block diagram which shows an example which has one abnormality detection circuit and a stop circuit with respect to MSLD. It is a flowchart which shows the flow of the execution process of an abnormality detection circuit.

Explanation of symbols

10 optical scanning device 14 photoconductor (scanned surface)
26 MSLD (light source)
32 Rotating polygon mirror (deflection means)
36 mirror 40 half mirror 41 SOS sensor 42 light quantity monitor sensor 43 SOS pickup mirror 52 LD drive circuit 54 light quantity control unit 58 abnormality detection circuit 60 stop circuit

Claims (5)

A light source that emits a plurality of light beams;
A light amount sensor that reflects a part of the light beam emitted from the light source and detects the light amount of the light beam;
A deflecting unit that deflects the light beam emitted from the light source toward the scanned surface, and a plurality of light beams deflected by the deflecting unit to be refracted a plurality of times and enter the scanned surface and the scanning end detection sensor. An optical system including a mirror;
An optical scanning device comprising:
Detecting means for detecting an abnormal light emission state when the light amount of the light beam detected by the light amount sensor is less than a predetermined value when adjusting the light amount of each light beam emitted from the light source;
Limiting means for limiting the emission of the light beam from the light source when the abnormal light emission state is detected by the detection means;
An optical scanning device comprising:   The optical scanning device according to claim 1, wherein the limiting unit stops emission of the light beam from the light source. The detection means detects the total number of light beams with a light amount of the light beam less than a predetermined value and detects an unstable light emission state when the total light amount of the light beam corresponding to the detection number is less than a specified value,
3. The optical scanning device according to claim 1, wherein the limiting unit does not limit emission of the light beam from the light source when the unstable light emission state is detected. 4.   The detecting means detects the total number of light beams whose light beam intensity is less than a predetermined value, and detects an abnormal light emission state when the total light beam intensity corresponding to the detection number is equal to or greater than a predetermined value. The optical scanning device according to claim 1 or 2.   5. The optical system according to claim 1, wherein the optical system includes a plurality of mirrors that refract a plurality of light beams deflected by the deflecting unit to enter a plurality of scanned surfaces. The optical scanning device described.

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