JP2003072139A - Semiconductor laser control apparatus of electrophotographic recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser control apparatus of an electrophotographic recorder capable of accurately controlling a quantity of an emission light of a semiconductor laser device corresponding to characteristic variation of the quantity of the emission light with respect to the driving current of the semiconductor laser device due to self-heating thereof. SOLUTION: The driving current for the semiconductor laser device is controlled based on the driving currents to be applied to at least three semiconductor laser devices and the characteristic point of the quantity of the emission light of each of the semiconductor laser devices.

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor laser control device of an electrophotographic recording apparatus for controlling a light emission amount of a semiconductor laser. 2. Description of the Related Art Conventionally, an electrophotographic recording apparatus using a semiconductor laser has been used for printing characters and line drawings. Therefore, a semiconductor laser is used to keep the density and line width constant. Scanning exposure was performed on the photoreceptor with a constant light emission amount, and stable printing was performed. However, as an application of an electrophotographic recording apparatus using a semiconductor laser in recent years, not only characters and line drawings but also photographic images have been used, and printing with higher image quality is strongly required. It has been demanded. For this purpose, it is necessary to modulate the light emission amount of the semiconductor laser in multiple steps in units of one dot, instead of scanning and exposing the semiconductor laser on the photosensitive member with a constant light emission amount. However, the characteristics of the semiconductor laser fluctuate due to changes in the ambient temperature and deterioration of the device of the semiconductor laser. Therefore, it is necessary to control the modulation current corresponding to the characteristics fluctuation. As an example of this semiconductor laser control method,
Japanese Unexamined Patent Publication No. Hei 8-139869 discloses that the current supplied to a semiconductor laser is stepwise increased, and the light emission amount of the semiconductor laser up to the second stage after exceeding the reference value at that time, and the light emission amount thereof A method is disclosed in which a threshold current and a luminous efficiency of a semiconductor laser are calculated from a proportional relationship between a current and a light emission amount using a value, and a modulation current is controlled from the calculation result. However, high-precision control is difficult with the above control method. The reason will be described below. The characteristic of the amount of emitted light with respect to the drive current of the semiconductor laser is generally linear. However, this is a characteristic when the ambient temperature is constant and when the heat radiation of the semiconductor laser itself is sufficiently performed. However, when a semiconductor laser is actually used, the size of the holder on which the semiconductor laser is mounted is also limited, so that the heat generated by the light emission of the semiconductor laser itself cannot be sufficiently dissipated, resulting in a non-linear characteristic as shown in FIG. Would. Therefore, Japanese Patent Application Laid-Open
If the modulation current is controlled from any two points on the characteristics of the semiconductor laser as described in JP-A-139869, an error will occur in the light emission amount of the semiconductor laser. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electrophotographic recording apparatus capable of controlling the emission light quantity of a semiconductor laser with a high degree of accuracy in response to a characteristic variation of the emission light quantity with respect to a drive current of the semiconductor laser due to heat generation of the semiconductor laser itself. An object of the present invention is to provide a semiconductor laser control device of the device. The object of the present invention is to provide a photoreceptor, a charger for charging the photoreceptor, an exposure optical unit for scanning and exposing the charged photoreceptor with a laser beam, and a semiconductor. A semiconductor laser control device for controlling the light emission amount of the laser,
In a semiconductor laser control device of an electrophotographic recording apparatus having a developing machine for developing a scan-exposed image area and a transfer device for transferring a developed image to a recording material, at least three
This is achieved by controlling the drive current flowing through the semiconductor lasers based on the characteristic points of the drive current flowing through one or more semiconductor lasers and the amount of light emission of the semiconductor laser at that time. Hereinafter, a semiconductor laser control device according to an embodiment of the present invention will be described. First, the configuration and operation principle of a recording apparatus according to an embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 2, the recording apparatus includes a charger 202, an exposure optical unit 203 having a semiconductor laser controller, a developing machine 204, a transfer unit 205, and a cleaner 2.
06 and an eraser 207 are arranged.
The photoconductor 201 is uniformly charged by the charger 202, and the image data 2 sent from the host 210 by the exposure optical unit 203.
11, the photosensitive member 201 is scanned and exposed. Next, the toner charged by the developing device 204 is developed into an image area, and then the toner is transferred onto the paper 209 by the transfer device 205. Photoconductor 201 with cleaner 206
The toner remaining on the upper surface is removed, the charge is uniformly removed by the eraser 207, and the charge returns to the initial charge. On the other hand, the toner transferred on the sheet 209 is fixed on the sheet 209 by the fixing device 208. The above is the description of the configuration and operation principle of the recording apparatus according to one embodiment of the present invention. Next, the configuration and operation principle of the exposure optical unit 203 according to one embodiment of the present invention will be described with reference to FIG. As shown in FIG. 3, the exposure optical unit 203 includes a semiconductor laser controller 301, a semiconductor laser 302, a rotating polygon mirror 303, and a beam detector 304. The semiconductor laser controller 301 supplies an appropriate drive current ID to the semiconductor laser 302 based on the image data 211. The semiconductor laser 302 emits light based on the drive current ID, and the laser beam is deflected by the rotary polygon mirror 303 to scan and expose the photoconductor 201. At this time, the laser beam immediately before writing is led to the beam detector 304 to align the writing position, and the writing position detection signal B
DT has been obtained. Further, a current IP proportional to the amount of emitted light flows from the photodetector for measuring the amount of emitted light contained in the semiconductor laser 302 to the semiconductor laser control device 301. The above is the exposure optical unit 203 according to one embodiment of the present invention.
Is a description of the configuration and operation principle of the first embodiment. Next, the configuration and operating principle of the semiconductor laser control device 301 according to one embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the semiconductor laser control device 301 includes switches 101 and 105 and an APC circuit 10.
2, 103, 104, D / A converters 106, 10
7, adder 108, bias current constant current circuit 109,
It is composed of a driver IC 110. The semiconductor laser 302 generally has a drive current I
Even if D is constant, the amount of emitted light fluctuates due to ambient temperature and deterioration of the element. Therefore, the light emission amount of the semiconductor laser 302 is measured by the photodetector PD built in the semiconductor laser 302, and the target light emission amount is compared with the actual light emission amount. The control is performed so as to increase the drive current flowing through the motor, and when the light emission amount is larger than the target value, the control is performed so as to decrease the drive current. By performing such control, the semiconductor laser 302 can emit light with a stable light emission amount. Such control is generally performed by APC (Automatic P
owerControl). Normally, APC is performed outside the print area for each scan. In this embodiment, this APC is performed at arbitrary three points PL, PM and PH as shown in FIG. First, the PD and the APC circuit 102 are connected by the switch 101 of FIG. 1, and only the switch 105 is turned on by the image data 211 so that the light emission amount of the semiconductor laser 302 becomes the target value P.
Drive current IL by the APC circuit 102 so that
To perform APC. At this time, the adder 108
Since the output voltage values from the / A converters 106 and 107 are 0, the voltage value output from the switch 105 is output to the driver IC 110 as it is. Driver IC 11
A value of 0 causes a current proportional to the input voltage value to flow through the semiconductor laser. Next, PD and APC are performed by the switch 101.
The driving current IM is connected to the switch 103 and the D / A converter 106 by image data 211 so that the light emission amount of the semiconductor laser 302 becomes the target value PM. To perform APC. At this time, adder 1
08 adds the voltage value output from the switch 105 and the output voltage of the D / A converter 106, and
Output to 0. By the way, D / A converter 106 is AP
The voltage value output from the C circuit 103 is stored in the image data 211.
Is to be divided according to Next, the PD and the APC circuit 104 are connected by the switch 101, and the switch 105 and the D / A converters 106 and 107 are connected by the image data 211.
Turns on all the data input to the semiconductor laser 30
APC circuit 10 so that the light emission amount of LED 2 becomes target value PH.
4 controls the drive current IH to perform APC. At this time, the adder 108 adds the voltage value output from the switch 105 and the output voltages of the D / A converters 106 and 107, and outputs the result to the driver IC 110. By the way, D / A
The converter 107 divides the voltage value output from the APC circuit 104 according to the image data 211. The bias current constant current circuit 109 is a constant current generating circuit for flowing a bias current IB set to a threshold current Ith or less to the semiconductor laser 302.
Next, actual printing will be described. First, the image data 21
The switch 105 of FIG. 1 is controlled by the least significant bit of 1. If the least significant bit of the image data 211 is 1,
The light emission amount of the semiconductor laser 302 is PL. Also, D
The light emission amount of the semiconductor laser 302 can be controlled from PL to PM by the image data 211 input to the / A converter 106. If all the data input to the D / A converter 106 are 1, the light emission of the semiconductor laser 302 can be controlled. The light amount is PM. Also, the D / A converter 107
The amount of light emitted from the semiconductor laser 302 can be controlled from PM to PH by image data input to the D / A.
If all the data input to the converter 107 are 1, the light emission amount of the semiconductor laser 302 becomes PH. As described above, the light emission amount of the semiconductor laser 302 can be controlled with high accuracy even if the characteristic of the light emission amount with respect to the drive current of the semiconductor laser 302 is nonlinear from PL to PH. According to the present invention, by controlling the drive current flowing through at least three or more semiconductor lasers and the characteristic point of the light emission amount of the semiconductor laser at that time, the drive current flowing through the semiconductor laser is controlled. The light emission amount of the semiconductor laser can be controlled with high accuracy in response to the characteristic fluctuation of the light emission amount with respect to the drive current of the semiconductor laser due to the heat generated by the semiconductor laser itself.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a semiconductor laser control device according to one embodiment of the present invention. FIG. 2 is a configuration diagram of a recording apparatus according to an embodiment of the present invention. FIG. 3 is a configuration diagram of an exposure optical unit including the semiconductor laser control device of FIG. 1; FIG. 4 is a diagram showing the relationship between the drive current of a semiconductor laser and the amount of emitted light. FIG. 5 is a diagram illustrating a relationship between a driving current of a semiconductor laser and an amount of emitted light. [Description of Signs] 101, 105 ... switch, 102, 103, 104 ... A
PC circuit, 106, 107 ... D / A converter, 108 ...
Adder, 109 ... constant current circuit for bias current, 110 ...
Driver IC, 201 photoconductor, 202 charger, 20
3 ... exposure optical unit, 204 ... developing machine, 205 ... transfer unit, 2
06 ... cleaner, 207 ... eraser, 208 ... fixing device,
209: paper, 210: host, 211: image data,
Reference numeral 301 denotes a semiconductor laser control device, 302 denotes a semiconductor laser, 303 denotes a rotating polygon mirror, and 304 denotes a laser beam detector.

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Claims (1)

Claims: 1. A photoreceptor, and a charger for charging the photoreceptor,
An exposure optical unit that scans and exposes the charged photoreceptor with laser light, a semiconductor laser control device that controls the amount of light emitted by the semiconductor laser, a developing machine that develops an image area that has been scanned and exposed, and a developing device that covers the developed image. In a semiconductor laser control device of an electrophotographic recording apparatus having a transfer device for transferring to a recording material, a driving current flowing through at least three or more semiconductor lasers and a driving current flowing through the semiconductor laser from a characteristic point of a light emission amount of the semiconductor laser at that time. A semiconductor laser control device for an electrophotographic recording device, which controls a current.