JP2008076496A - Light beam scanner and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid generation of an abnormal image by making it possible to detect the abnormal emission of an LD, beforehand. <P>SOLUTION: The light beam scanner detects the abnormal emission of the LD, by changing the gain to the output signal of a synchronous detection sensor. Furthermore, LD lighting by data is avoided at the detection of the abnormal emission of the LD. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for detecting in advance an abnormal LD light emission in an image forming apparatus of a scanning recording system using a combination of a laser diode (hereinafter referred to as LD) and a polygon mirror.

  Conventionally, in a scanning recording type image forming apparatus using a combination of a laser diode (hereinafter referred to as LD) and a polygon mirror, when writing operation is started, the LD is turned on for synchronization, and the LD light hits the light receiving element to detect synchronization. A signal is obtained.

  Since the LD is completely lit at the timing when the LD light is incident on the synchronization detection unit, the synchronization detection signal is normally output regardless of the magnitude of the LD offset light emission.

Here, a power control device that controls the light emission power of the laser light source based on the target value of the light emission power of the laser light source in the optical pickup and the monitor signal (FSPD signal) that detects the actual light emission power of the laser light source. The ALSI to be configured includes a VGA amplifier, a reproduction detection system amplifier and a recording detection system amplifier as an amplification circuit for amplifying the monitor signal, and a temperature detection amplifier for detecting the temperature in the ALSI. Based on the temperature detection signal, each of the amplifiers that amplifies the monitor signal from the optical pickup by setting and giving signals Ofs1 to Ofs3 for removing the offset component to each amplifier using a correlation coefficient obtained in advance. A technology that can remove the offset component of the amplifier circuit and always accurately control the emission power of the laser light source is disclosed. (For example, see Patent Document 1).
JP 2005-228433 A

  However, in the prior art, even if the offset light emission amount is large when the LD is abnormal, there is no means for detecting the abnormality other than viewing the image output result.

  Accordingly, an object of the present invention is to detect abnormal LD light emission in advance and to avoid the occurrence of abnormal images.

  The invention according to claim 1 is an optical beam scanning device that detects abnormal LD light emission by switching the gain with respect to the output signal of the synchronous detection sensor.

  According to a second aspect of the present invention, there is provided a light beam scanning device for detecting abnormal LD light emission by switching a reference voltage of a comparator with respect to an output signal of a synchronous detection sensor.

  According to a third aspect of the present invention, there is provided a light beam scanning device for detecting abnormal LD light emission by A / D converting an output signal of a synchronous detection sensor.

  According to a fourth aspect of the present invention, in the light beam scanning device according to the first or second aspect, when the abnormal LD light emission is detected, the LD lighting based on the data is not performed.

  A fifth aspect of the present invention is an image forming apparatus equipped with the light beam scanning apparatus according to the first to fourth aspects.

  According to the present invention, abnormal LD light emission can be detected in advance, and an abnormal image can be avoided.

  Next, the configuration of the first exemplary embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a writing unit of the image forming apparatus.

  In FIG. 1, in a laser diode unit (LDU) 1, a laser beam emitted from a laser diode (LD) is converted into parallel rays by a collimator lens (not shown), and then a rotating polygon mirror (hereinafter referred to as a polygon mirror) 2 Then, an image is formed on the charged surface of the drum-shaped photosensitive member (photosensitive drum) 5 by the imaging lens composed of the F-θ lens 3 and the like and the reflecting mirror 4.

  This laser beam is modulated on the basis of an image signal, repeatedly turned on and off, and repeatedly scanned in the main scanning direction indicated by an arrow in the figure. At the same time, the photosensitive member 5 rotates and performs sub-scanning to thereby rotate the photosensitive member. An electrostatic latent image is formed on 5.

  The electrostatic latent image formed on the photoconductor 5 is developed with a charged developer (toner), and a transfer material such as transfer paper to which a charge opposite to the developer is applied to the photoconductor 5 is applied to the photoconductor 5. The developer is transferred to the transfer material by being in close contact.

  Then, after the transfer material is separated from the photoreceptor 5, the developer is fused and fixed on the transfer material by being heated and pressurized in the fixing unit.

  Therefore, in this embodiment, the photoconductor 5, the developer, the transfer unit, and the fixing unit constitute an image forming unit, and image formation is performed by a known electrophotographic method.

  Further, the light receiving element 7 detects the laser beam by the reflected light from the synchronization detecting mirror 6 arranged outside the scanning region on the photoconductor 5, and the LD control unit 8 receives the synchronization detection signal obtained by the light receiving element 7. It has a timing generation circuit that performs various signal processing on the basis.

  In a scanning recording type image forming apparatus using a combination of a laser diode (hereinafter referred to as LD) and a polygon mirror, when a writing operation is started, the LD is turned on for synchronization, and the LD light strikes the light receiving element 7 to detect synchronization. Is obtained. Since the LD is completely lit at the timing when the LD light is incident on the synchronization detection unit, the synchronization detection signal is normally output regardless of the magnitude of the LD offset light emission. In the present embodiment, it is possible to detect minute light emission when the LD is not lit by data by the output of the synchronization detection sensor.

  A block diagram of the synchronization detection sensor is shown in FIG. The current output from the PD (photodiode) is set to a higher amplification factor than usual by the gain switching signal connected to the synchronization detection sensor from the I / O control unit controlled by the program operating on the CPU.

  Next, the LD control unit cancels the LD extinguishing state with respect to the LD driver IC, and shifts to a state where the LD can be turned on by the image data. At this time, if the output of the synchronization detection sensor is ON even if no image data is given, it is determined that the LD is emitting abnormal light.

  Thereafter, the image forming apparatus notifies the controller unit of an error without performing image formation.

  Next, the processing operation of the present embodiment will be described in detail with reference to the drawings.

  First, the LD is initialized (S201). Therefore, it is determined whether there is an LD error (S202), and if there is (S202 / Yes), error processing is executed.

  On the other hand, if not (S202 / No), the gain of the synchronous detection sensor is switched to detect the abnormal LD light emission (S203).

  It is determined whether or not a synchronization signal is output (S204), and if there is (S204 / Yes), error processing is executed as abnormal light emission (S205).

  On the other hand, if there is not (S204 / No), the gain of the normal synchronization detection sensor is switched (S207) with no abnormal light emission (S206).

  Next, the configuration of the second exemplary embodiment of the present invention will be described with reference to the drawings. In the first embodiment described above, the gain is switched within the circuit built in the synchronization detection sensor. However, in this embodiment, the gain setting for the synchronization detection output signal is not changed, and FIG. As shown in the figure, by switching the reference voltage of the comparator circuit provided outside the synchronization detection sensor, it is possible to detect whether the LD is in an abnormal light emission state based on whether a synchronization detection output is generated when the LD bias light is emitted. .

  Next, the structure of the 3rd Embodiment of this invention is demonstrated with reference to drawings. Without changing the gain setting for the PD analog output signal, using the A / D conversion circuit provided outside the synchronization detection sensor as shown in FIG. 5, the synchronization detection output when the LD is completely turned off, It is possible to detect whether the LD is in an abnormal light emission state by comparing the synchronization detection output at the time of LD bias light emission numerically.

  In each of the above embodiments, the synchronization detection signal is generated only when there is an abnormal LD light emission by not performing LD forced lighting or APC lighting control for synchronization detection performed in a normal writing operation. It may be to be output.

  Each of the above-described embodiments is a preferred embodiment of the present invention, and various modifications can be made without departing from the scope of the present invention.

1 is a configuration diagram of a writing unit of an image forming apparatus according to a first embodiment of the present invention. It is a block diagram of the synchronous detection sensor of the 1st Embodiment of this invention. It is a flowchart which shows the processing operation of the 1st Embodiment of this invention. It is a figure which shows the structure of the 2nd Embodiment of this invention. It is a figure which shows the structure of the 3rd Embodiment of this invention.

Explanation of symbols

1 Laser diode unit (LDU)
2 Polygon mirror 3 F-θ lens 4 Reflection mirror 5 Photosensitive drum D
6 Sync detection mirror 7 Light receiving element

Claims (5)

  An optical beam scanning device for detecting abnormal LD light emission by switching a gain with respect to an output signal of a synchronization detection sensor.   An optical beam scanning apparatus for detecting abnormal LD light emission by switching a reference voltage of a comparator with respect to an output signal of a synchronization detection sensor.   An optical beam scanning apparatus for detecting abnormal LD light emission by A / D converting an output signal of a synchronous detection sensor.   3. The light beam scanning apparatus according to claim 1, wherein when the abnormal LD light emission is detected, the LD is not turned on by data.   An image forming apparatus equipped with the light beam scanning device according to claim 1.

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