JP6470100B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning device that reciprocally scans an object to be scanned with a light beam and an image forming apparatus including the same.

  Among optical scanning devices provided in image forming apparatuses such as copying machines, printers, facsimiles, and multi-function machines, there are those that reciprocately scan a scanned object such as a photosensitive drum. In the optical scanning device, a light beam emitted from a light source is reflected by a scanning body that performs scanning motion, so that the scanning target is reciprocated. In such an optical scanning device, the scanning motion speed of the scanning body may change due to a change in ambient temperature or the like. When the speed of the scanning motion changes, there is a problem that the writing position of the latent image is shifted.

  For this reason, a technique is known in which a BD (Beam Detect) sensor is provided at both ends of the scanning range, and the scanning motion of the scanning body is controlled based on the timing at which the BD sensor detects the light beam.

  In order to reduce the cost, one of the two BD sensors is replaced with a reflector such as a mirror, and the timing at which the light beam enters the BD sensor without passing through the reflector and the reflector A technique for controlling the scanning movement of the scanning body based on the timing at which the reflected light beam enters the BD sensor is also known. In such an optical scanning device in which one of the BD sensors is replaced by a reflector, the detection signal of the light beam that has entered the BD sensor without passing through the reflector, and the light that has been reflected by the reflector and entered the BD sensor It is necessary to identify the detection signal of the beam, and by performing this identification, it is possible to perform reciprocal scanning.

  Furthermore, in recent years, in order to reduce the size and cost of optical scanning devices, reduce power consumption, heat generation, and noise, and shorten the time required to form the first image, MEMS ( A device using Micro Electro Mechanical System) is known (for example, see Patent Document 1). This conventional optical scanning device is of an electromagnetic type, and the MEMS is bipolar driven in which a current is bidirectionally supplied to one winding. Therefore, in the conventional optical scanning device, based on the polarity of the MEMS drive voltage, the detection signal of the light beam that has entered the BD sensor without passing through the reflector, and the light reflected by the reflector and incident on the BD sensor. A detection signal of the light beam is identified.

JP 2010-128131 A

  However, when an electrostatic MEMS is used in the optical scanning device, the MEMS is unipolarly driven to always apply a voltage in a certain direction to the electrodes, and the polarity of the MEMS driving voltage is constant, so that the conventional optical scanning is performed. In the identification method in the apparatus, the detection signal of the light beam incident on the BD sensor without passing through the reflector and the detection signal of the light beam reflected by the reflector and incident on the BD sensor could not be identified. . For this reason, the conventional optical scanning device cannot use an electrostatic MEMS, and further downsizing, cost reduction, power consumption / heat generation / noise reduction, and time required for image formation of the first sheet are reduced. It was an obstacle to shortening.

  An object of the present invention is to detect a detection signal of a light beam incident on a BD sensor without passing through a reflector, and to reflect the reflected signal on the BD sensor regardless of whether the electromagnetic type or electrostatic type MEMS is used. An object of the present invention is to provide an optical scanning device capable of discriminating a detection signal of an incident light beam and an image forming apparatus including the same.

  The optical scanning device of the present invention reciprocally scans a scanning range including a latent image forming region of a scanning object with a light beam. The optical scanning device includes a light source, a scanning body, a BD sensor, a reflector, and a control unit. The light source emits a light beam. The scanning body scans and moves so as to scan the scanning range by reflecting the light beam emitted from the light source. The BD sensor is disposed at the first end of the scanning range, and outputs a detection signal when a light beam is detected. The reflector is disposed at the second end of the scanning range, and reflects the received light beam toward the BD sensor. The control unit controls the scanning motion based on the detection signal. A first time interval from a timing at which the BD sensor is scanned in the first scanning direction from the reflector to the BD sensor to a timing at which the BD sensor is scanned in the second scanning direction from the BD sensor to the reflector; and a second direction The second time interval from the timing when the reflector is scanned to the timing when the reflector is scanned in the first direction is different.

  In this configuration, if the time interval when the detection signal is input becomes equal to the first time interval, the time interval is scanned from the timing when the BD sensor is scanned in the first scanning direction to the second scanning direction. It can be identified as a time interval up to the timing. Also, if the time interval at which the detection signal is input is equal to the second time interval, the time interval is from the timing when the reflector is scanned in the second scanning direction to the timing when the reflector is scanned in the first scanning direction. Can be identified as the time interval. Accordingly, after the BD sensor is scanned in the first scanning direction and before the BD sensor is scanned in the second scanning direction, the BD sensor is scanned in the second scanning direction and then in the second scanning direction. Before the reflector is scanned, after the reflector is scanned in the second scanning direction until before the reflector is scanned in the first scanning direction, and the reflector is scanned in the first scanning direction. It is possible to identify the scanning position and the scanning direction during the period from the start to the time before the BD sensor is scanned in the first scanning direction.

  In the above-described configuration, the BD sensor and the reflector can be configured to be arranged asymmetrically with respect to the center of the scanning range.

  In this configuration, the first time interval and the second time interval can be easily configured to be different.

  In addition, the control unit causes the light source to sequentially emit light by a plurality of light emission patterns having different light emission timings when the light source emits a light beam, and determines the light emission timing of the light source based on the light emission pattern in which the detection signal is input a predetermined number of times. Can be configured.

  In this configuration, the first time interval from the timing when the BD sensor is scanned in the first scanning direction to the timing when the BD sensor is scanned in the second scanning direction, and the timing from when the BD sensor is scanned in the second scanning direction. A third time interval from the timing when the reflector is scanned in the two scanning directions, a second time interval from the timing when the reflector is scanned in the second scanning direction to the timing when the reflector is scanned in the first scanning direction, And a light emission pattern that repeats light emission at a fourth time interval from a timing at which the reflector is scanned in the first scanning direction to a timing at which the BD sensor is scanned in the first scanning direction. Among these, the control unit holds a plurality of light emission patterns starting from different time intervals. Light emission by each of these light emission patterns is performed following the timing when the detection signal at the time of forced light emission is input. As a result, when the light emission timing in each light emission pattern matches the timing for scanning the BD sensor and the reflector in actual scanning, a predetermined number of detection signals are input. For this reason, it can be determined that the light emission timing in the light emission pattern in which the detection signal is input a predetermined number of times coincides with the timing of scanning the BD sensor and the reflector in actual scanning.

  An image forming apparatus according to the present invention includes a scanned object and the optical scanning device having any one of the above-described configurations.

  In this configuration, if the time interval when the detection signal is input becomes equal to the first time interval, the time interval is scanned from the timing when the BD sensor is scanned in the first scanning direction to the second scanning direction. It can be identified as a time interval up to the timing. Also, if the time interval at which the detection signal is input is equal to the second time interval, the time interval is from the timing when the reflector is scanned in the second scanning direction to the timing when the reflector is scanned in the first scanning direction. Can be identified as the time interval. Accordingly, after the BD sensor is scanned in the first scanning direction and before the BD sensor is scanned in the second scanning direction, the BD sensor is scanned in the second scanning direction and then in the second scanning direction. Before the reflector is scanned, after the reflector is scanned in the second scanning direction until before the reflector is scanned in the first scanning direction, and the reflector is scanned in the first scanning direction. It is possible to identify the scanning position and the scanning direction during the period from the start to the time before the BD sensor is scanned in the first scanning direction.

  According to the present invention, regardless of whether the electromagnetic type or the electrostatic type MEMS is used, the detection signal of the light beam that has entered the BD sensor without passing through the reflector, and the signal reflected by the reflector to the BD sensor. It can be distinguished from the detection signal of the incident light beam.

1 is a diagram illustrating a schematic configuration of an image forming apparatus including an optical scanning device according to a first embodiment of the present invention. It is a figure which shows the relationship between the scanning position by a laser beam, and the time interval which a detection signal inputs. It is a figure which shows the several light emission pattern of a laser beam. It is a flowchart which shows an example of a process of a control part.

  As shown in FIG. 1, the image forming apparatus 1 including the optical scanning device 10 according to the first embodiment includes, in addition to the optical scanning device 10, a photosensitive drum 2, and a charging device, a developing device, and a transfer (not shown). And a fixing device. The photosensitive drum 2 is an example of a member to be scanned by the optical scanning device 10.

  The charging device charges the peripheral surface of the photosensitive drum 2 to a predetermined potential. The photosensitive drum 2 rotates in a predetermined direction. The optical scanning device 10 forms an electrostatic latent image in the latent image forming region E1 on the peripheral surface of the photosensitive drum 2 by exposing the peripheral surface of the photosensitive drum 2 with laser light. The developing device visualizes the electrostatic latent image into a toner image by supplying toner to the peripheral surface of the photosensitive drum 2. The transfer device transfers the toner image on the circumferential surface of the photosensitive drum 2 to a sheet. The fixing device fixes the toner image to the sheet. Laser light is an example of a light beam.

  The optical scanning device 10 includes a MEMS mirror 11, a light source 12, a BD sensor 13, a reflection mirror 14, a MEMS driving unit 16, and a control unit 17.

  The light source 12 emits laser light toward the MEMS mirror 11. For example, a laser diode is used as the light source 12.

  The MEMS mirror 11 reflects the laser beam emitted from the light source 12 toward the photosensitive drum 2 while performing a scanning motion that oscillates in a direction away from and in contact with the photosensitive drum 2.

  The scanning direction of the MEMS mirror 11 changes the reflection direction of the laser light emitted from the light source 12, and the scanning range E <b> 2 including the latent image forming region E <b> 1 of the photosensitive drum 2 by the laser light emitted from the light source 12. Are reciprocally scanned. The MEMS mirror 11 is a scanning body of the present invention.

  The BD sensor 13 and the reflection mirror 14 are disposed outside the latent image forming area E1 of the photosensitive drum 2 and within the scanning range E2. The BD sensor 13 is disposed at the first end of the scanning range E2, and the reflection mirror 14 is disposed at the second end of the scanning range E2. The reflection mirror 14 is an example of a reflector according to the present invention.

  The BD sensor 13 outputs a detection signal when detecting the laser beam.

  A first scanning direction from the reflection mirror 14 toward the BD sensor 13 is defined as an A direction. A second scanning direction from the BD sensor 13 toward the reflection mirror 14 is defined as a B direction.

  The BD sensor 13 is scanned at the end position of scanning in the A direction and the start position in the B direction. The reflection mirror 14 is scanned at the end position of the scanning in the B direction and the start position in the A direction.

  The MEMS drive unit 16 controls the scanning motion of the MEMS mirror 11. The control unit 17 comprehensively controls each unit device of the optical scanning device 10 including the MEMS driving unit 16.

  The MEMS drive unit 16 is an electrostatic type, is unipolarly driven, and the polarity of the drive voltage that vibrates the MEMS mirror 11 is constant. For this reason, from the polarity of the drive voltage that vibrates the MEMS mirror 11, the detection signal of the laser light that has entered the BD sensor 13 without passing through the reflection mirror 14, and the light reflected by the reflection mirror 14 and incident on the BD sensor 13. The detection signal of the laser beam cannot be distinguished.

  Therefore, even in the electrostatic type, the detection signal of the laser beam incident on the BD sensor 13 without passing through the reflection mirror 14 and the detection signal of the laser beam reflected by the reflection mirror 14 and incident on the BD sensor 13 are discriminated. A possible configuration will be described.

  In the optical scanning device 10, the BD sensor 13 and the reflection mirror 14 are disposed asymmetrically with respect to the center C of the scanning range E2.

  As shown in FIG. 2, in steady APC (Automatic Power Control) of the light source 12, the laser light incident on the BD sensor 13 without passing through the reflecting mirror 14 is detected by the BD sensor 13, and the detection signals BD1, BD2, BD3, BD4... Are output. The laser light reflected by the reflection mirror 14 and incident on the BD sensor 13 is also detected by the BD sensor 13 and detection signals MR1, MR2,.

  Here, the time interval from the timing when the BD sensor 13 is scanned in the A direction to the timing when the BD sensor 13 is scanned in the B direction is defined as a first time interval T1. A time interval from the timing when the BD sensor 13 is scanned in the B direction to the timing when the reflecting mirror 14 is scanned in the B direction is defined as a third time interval T3. A time interval from the timing when the reflecting mirror 14 is scanned in the B direction to the timing when the reflecting mirror 14 is scanned in the A direction is defined as a second time interval T2. A time interval from the timing when the reflecting mirror 14 is scanned in the A direction to the timing when the BD sensor 13 is scanned in the A direction is defined as a fourth time interval T4.

  The optical scanning device 10 is configured such that at least the first time interval T1 and the second time interval T2 are different. As described above, in the optical scanning device 10, the BD sensor 13 and the reflection mirror 14 are disposed asymmetrically with respect to the center C of the scanning range E2, thereby the first time interval T1 and the second time interval T2. Are different from each other.

  As shown in FIG. 3, the control unit 17 starts from the time of input of a detection signal by forced light emission that continuously causes the light source 12 to emit light, that is, at the time of initial detection. The light source 12 is caused to emit light in order by a plurality of different light emission patterns.

  The plurality of light emission patterns are light emission patterns that repeat light emission for a predetermined short period of time at a first time interval T1, a third time interval T3, a second time interval T2, and a fourth time interval T4. It is the light emission pattern which starts from a mutually different time interval among time intervals T1-T4.

  For example, as shown in FIG. 3A, the first light emission pattern causes the light source 12 to emit light at the first time interval T1, the third time interval T3, and the second time interval T2 starting from the fourth time interval T4. It is a light emission pattern. As shown in FIG. 3B, the second light emission pattern starts from the first time interval T1 and causes the light source 12 to emit light at the third time interval T3, the second time interval T2, and the fourth time interval T4. It is. As shown in FIG. 3C, the third light emission pattern starts from the third time interval T3 and causes the light source 12 to emit light at the second time interval T2, the fourth time interval T4, and the first time interval T1. It is. As shown in FIG. 3D, the fourth light emission pattern starts from the second time interval T2 and causes the light source 12 to emit light at the fourth time interval T4, the first time interval T1, and the third time interval T3. It is.

  If the detection signal of the initial detection is a result of scanning the reflection mirror 14 in the A direction, the BD sensor 13 in the A direction and the B direction is emitted by emitting the light source 12 with the first light emission pattern from the time of the initial detection. At the time of scanning, the detection signals BD1, BD2, MR1 and MR2 should be inputted at all timings when the reflecting mirror 14 is scanned in the B direction and the A direction. That is, the detection signal should be input four times in one cycle of the scanning movement of the MEMS mirror 11. On the other hand, even if the light source 12 emits light with the second to fourth light emission patterns starting from the initial detection time, the number of detection signals input in one cycle of the scanning movement of the MEMS mirror 11 does not reach four. From this, the optical scanning device 10 shifts to steady APC as follows.

  As shown in FIG. 4, the control unit 17 defines 1 in the algebra N (S1), forcibly emits light from the light source 12 (S2), and when a detection signal is input (S3), The light source 12 emits light with the first light emission pattern starting from the time of input, that is, the time of initial detection (S4). The algebra N is an integer.

  When the detection signal is input a predetermined number of times obtained based on a value obtained by dividing the monitoring time for emitting the light source 12 with the first light emission pattern by the scanning motion cycle (S5), the control unit 17 detects the detection input by the initial detection. It can be identified that the signal is due to scanning of the reflecting mirror 14 in the A direction, and the routine proceeds to steady APC (S6).

  When the number of detection signal inputs during the monitoring time when the light source 12 emits light in the first light emission pattern does not reach the predetermined number, the control unit 17 defines N + 1 as the algebra N (S7), and the algebra N is 4 If it is below (S8), the process returns to S2. If the algebra N is 5 or more, a predetermined error process is performed as a detection error in which the BD sensor 13 cannot detect the laser beam (S9).

  When switching to a different light emission pattern, such as switching from the first light emission pattern to the second light emission pattern, the control unit 17 starts the period of scanning movement of the MEMS mirror 11 from the time of initial detection during monitoring of the first light emission pattern. The light source 12 is emitted immediately before the detection signal so that the detection signal is input after the integral multiple of the time. That is, the time interval between the initial detections of different light emission patterns is set to an integral multiple of the scanning motion cycle.

  The control unit 17 performs initial detection again after a time that is an integral multiple of the period of the scanning motion from the time of initial detection of the first light emission pattern, and emits the light source 12 with the second light emission pattern from the time of this initial detection as a starting time. Get the number of input of the detection signal.

  The control unit 17 sequentially monitors the first to fourth light emission patterns. When the number of detection signal inputs during the monitoring time reaches a predetermined number, the control unit 17 proceeds to steady APC.

  As described above, the scanning position and the scanning direction can be identified depending on whether or not the number of detection signals input during the monitoring time has reached a predetermined number, and even when using either an electromagnetic type or electrostatic type MEMS, reflection is possible. The detection signals BD1, BD2, BD3, and BD4 of the laser light incident on the BD sensor 13 without passing through the mirror 14 and the detection signals MR1 and MR2 of the laser light reflected on the reflection mirror 14 and incident on the BD sensor 13 Can be identified.

  The optical scanning device according to the second embodiment sequentially performs monitoring by all the first to fourth light emission patterns, then selects a light emission pattern whose detection signal has been input a predetermined number of times, and performs initial detection. Starting from, the light source 12 emits light with a selected light emission pattern, thereby shifting to steady APC.

  By executing monitoring with all light emission patterns, the number of detection signal inputs in all light emission patterns can be confirmed, and the risk of erroneous determination due to stray light or noise can be reduced.

  In the optical scanning device according to the third embodiment, instead of the configuration in which monitoring is performed by the first to fourth light emission patterns, the detection signal is surely input by forced light emission, and the time interval at which the detection signal is input is the first time interval. When the time interval is equal to the time interval T1, the time interval is identified as the time interval from the timing when the BD sensor 13 is scanned in the A direction to the timing when the BD sensor 13 is scanned in the B direction. Further, when the time interval at which the detection signal is input is equal to the second time interval, the time interval is the time interval from the timing when the reflecting mirror 14 is scanned in the B direction to the timing when the reflecting mirror 14 is scanned in the A direction. Is identified.

  The forced light emission ensures that the detection signals BD1, BD2, MR1, and MR2 are input at all timings when the BD sensor 13 is scanned in the A direction and the B direction and when the reflection mirror 14 is scanned in the B direction and the A direction. become. For this reason, it can transfer to steady APC in a short time.

  It is conceivable to construct a new embodiment by combining the technical features of the above-described embodiments.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 2 ... Photosensitive drum (to-be-scanned body)
DESCRIPTION OF SYMBOLS 10 ... Optical scanning device 11 ... MEMS mirror (scanning body)
12 ... Light source 13 ... BD sensor 14 ... Reflection mirror (reflector)
16 ... MEMS drive unit 17 ... Control unit

Claims (5)

An optical scanning device that reciprocally scans a scanning range including a latent image forming region of a scanned object with a light beam,
A light source that emits a light beam;
A scanning body that scans and moves so as to reflect the light beam emitted from the light source and scan the scanning range;
A BD sensor disposed at a first end of the scanning range and outputting a detection signal when a light beam is detected;
A reflector disposed at a second end of the scanning range for reflecting the received light beam toward the BD sensor;
A control unit for controlling the scanning movement based on the detection signal,
A first time from the timing when the BD sensor is scanned in the first scanning direction from the reflector toward the BD sensor to the timing when the BD sensor is scanned in the second scanning direction from the BD sensor toward the reflector. An interval and a second time interval from a timing at which the reflector is scanned in the second scanning direction to a timing at which the reflector is scanned in the first scanning direction are different from each other .
The control unit causes the light source to sequentially emit light by a plurality of light emission patterns having different light emission timings when the light source emits a light beam, and determines the light emission timing of the light source based on a light emission pattern in which a detection signal is input a predetermined number of times , Optical scanning device. An optical scanning device that reciprocally scans a scanning range including a latent image forming region of a scanned object with a light beam,
A light source that emits a light beam;
A scanning body that scans and moves so as to reflect the light beam emitted from the light source and scan the scanning range;
A BD sensor disposed at a first end of the scanning range and outputting a detection signal when a light beam is detected;
A reflector disposed at a second end of the scanning range for reflecting the received light beam toward the BD sensor;
A control unit for controlling the scanning motion based on the detection signal;
With
A first time from the timing when the BD sensor is scanned in the first scanning direction from the reflector toward the BD sensor to the timing when the BD sensor is scanned in the second scanning direction from the BD sensor toward the reflector. An interval and a second time interval from a timing at which the reflector is scanned in the second scanning direction to a timing at which the reflector is scanned in the first scanning direction are different from each other.
The control unit causes the light source to sequentially emit light by a plurality of light emission patterns having different light emission timings when the light source emits a light beam, and based on a detection result of the BD sensor for the plurality of light emission patterns, An optical scanning device that identifies a scanning direction. Wherein A BD sensor and the reflector, are arranged asymmetrically relative to the center of the scanning range, the optical scanning device according to claim 1 or 2. When the control unit causes the light source to continuously emit light and the time interval when the detection signal is input is equal to the first time interval, this time interval is the timing when the BD sensor is scanned in the first scanning direction. If the time interval from which the detection signal is input is equal to the second time interval, the time interval is determined to be the second scanning direction. the reflector is identified as the reflector in a first scanning direction from the timing scanned is the time interval from the timing scanned, the optical scanning apparatus according to any one of claims 1 to 3 in. A scanned object;
An image forming apparatus comprising the optical scanning device according to claim 1.

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