JPS6083466A - Controller of laser beam printer - Google Patents

Abstract

PURPOSE:To prevent deterioration in image quality by providing a linear image sensor in a no-image area on a photosensitive body and detecting a beam, and controlling the timing of writing to the photosensitive body on the basis of the timing of the detection. CONSTITUTION:The linear image sensor 10 is provided in the no-image area on the photosensitive body 5. Variation in the shape of the laser beam is detected by the sensor 10 in the form of variation in current value, amplified, and converted by an A-D converter 13 into a digital signal, which is sent out to a control circuit 14. The control circuit 14 compares the digital signal with a value determined corresponding to a reference beam value and outputs a control command from an output interface 14e to a driving circuit 15 so that their deviation becomes zero. Further, a rotary polygon mirror 3 is rotated on the basis of another signal inputted to an input interface 14a and a control command is sent to a driving circuit 19 to rotate the photosensitive body 5. A timer circuit 20, on the other hand, inputs the output of an amplifier 12 to modulate the laser beam of a laser 1 according to recording information.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a laser beam that detects the beam diameter of a scanning laser beam, controls the beam diameter, and controls the writing timing on a photoreceptor based on the detection timing. The present invention relates to a control device for a beam printer.

[Prior art]

As a conventional laser beam printer, there is one shown in FIG. 1, for example. This laser beam printer includes a semiconductor laser 1 that emits a laser beam, a collimator lens 2 that converts the beam from the laser into a parallel beam, and a rotating polygon mirror 3 that polarizes and scans the bits from the collimator lens 2 toward a photoreceptor. , an Fθ lens 4 that corrects the deviation of the scanning light point between the center and the end of the laser beam deflected and scanned by the rotating polygon @3, and a photoreceptor 5 whose surface is irradiated with the laser beam of the Fθ lens 4. It is composed of.

In the above configuration, the beam is modulated by controlling the emission and stop of the laser beam of the semiconductor laser l according to the recorded information, and this beam is scanned by the rotation of the rotating polygon mirror 3, and Fθ
After correction by the lens 4, the photoreceptor 5 is irradiated with a beam and exposed.

The electrostatic latent image formed by this exposure is developed with toner by a developing device (not shown), transferred to plain paper, and further fixed to complete printing.

However, with conventional laser beam printers, for example, if plastic lenses are used as collimator lenses and Fθ lenses, which are easy to manufacture with aspherical surfaces and can be made at low cost, the refractive index of the lenses may change depending on temperature, humidity, etc. Since the optical axis changes, the diameter of the laser beam that irradiates the surface of the photoreceptor 5 changes, which may cause image quality to deteriorate.

[Object and structure of the invention]

The present invention has been made in view of the above, and in order to control the laser beam diameter and prevent deterioration of image quality, a linear image sensor is provided in the non-image area of the photoreceptor to detect the beam diameter. The present invention provides a control device for a laser beam printer that completely controls the writing timing on a photoreceptor based on the detection timing.

〔Example〕

Hereinafter, a control device for a laser beam printer according to the present invention will be explained in detail.

FIG. 2 shows an embodiment of the present invention, and the same parts as in FIG. However, the configuration differs from that of FIG. 1 in that it uses a CCD or the like disposed in front of the writing start point at which image signals are written in the main scanning direction, and that it includes a near imaging sensor 10 and a control section to be described in detail below.

The control unit includes a drive circuit 11 and □ that supplies two-phase or three-phase clock pulses to a large number of electrodes in the linear imaging sensor lo, and supplies all power to each element, and an output signal from the linear imaging sensor 1°. (current value according to change in laser beam diameter), 6A-9 conversion 2 and □3 that convert the analog output signal of the □amplifier 12 into a digital signal, and the A-D In response to the change '513° output signal, the laser beam diameter is calculated and the laser 1
A control circuit 14 executes various controls necessary for printing in addition to output control of the rotary multi-ml mirror 3 and photoreceptor 5, etc., and a control circuit 14 that controls the emission and stop of the semiconductor laser 1 and output according to commands from the control circuit. A drive circuit 17 that controls a motor 16 that rotates the multifaceted rotating mirror 3.
, a drive circuit 19 that controls a motor 18 that rotates the photoreceptor 5, and a timer circuit 20 that outputs a write start signal st''6 when a predetermined time period has elapsed after inputting the output signal of the amplifier circuit 12. ing.

The control circuit 14 also includes an input interface 14a that takes in other signals from the A-D converter 13 and sensors and sends them to the pass line, and a program and A-D converter 13 for controlling printing. A ROM 14'b (7) stores a program for calculating the total beam diameter based on data output from the CPU 1, which executes predetermined control and calculations according to the program.
4c, a RAM l 4.3 that temporarily stores the calculation results from the cptr 14c and various data input from the input interface 14a, and an output input that outputs the control results to external drive circuits and equipment). 7 Ace I
It consists of a 4G toyorinal microcomputer.

Note that, as shown in FIG. 3, the linear imaging sensor 1o is arranged perpendicular to the main scanning direction, and is provided so that the beam cross section BS is incident on the center portion.

In the above configuration, the principle of printing using a laser beam is as described above, so the explanation will be omitted. However, the shape of the laser beam is detected by the near imaging sensor 10 as a change in current value, and the current value is detected by the amplifier! After being amplified in step 2, it is converted into a digital signal by an A-D converter 13 and sent to a control circuit 14. The control circuit 14 compares a value predetermined as a current value corresponding to the reference beam value and the output value of the A-D converter 13,
output interface 14e so that the deviation is zero.
A control command is sent to the drive circuit 15. In this system, the output signal of the sensor 10 functions as a feedback signal. Further, the control circuit 14 issues a control command to the drive circuit 17 to rotate the rotating polygon mirror 3 based on other signals input to the input interface 14a, and also issues a control command to the drive circuit 19 to rotate the photoreceptor 5. let On the other hand, the timer circuit 20 measures a predetermined time period after inputting the output signal of the amplifier 12, and when the laser beam reaches the writing start point P (FIG. 3), it outputs a writing start signal 5tff and the laser beam of the semiconductor laser l is The beam is modulated according to the recorded information.

Among the above processes, FIG. 4 is a flowchart showing the control of the laser beam diameter of the semiconductor laser 1 (increase/decrease of the control current value input to the semiconductor laser) by the linear imaging sensor 10. In the figure, so is the current equivalent value of the digital signal output from the A-D converter 13, and SR is the control current equivalent value of the reference beam diameter preset in the memory.

Note that since the beam diameter can be directly detected by the near imaging sensor 10, the beam diameter can be known as an actual measurement value.

Although the linear imaging sensor 1o may be of a secondary array type or a secondary array type, the secondary array type is most suitable for the use of the present invention because the cross-sectional shape of the beam can be directly detected.

Further, although the example in which the beam diameter is controlled by varying the laser output direction has been shown, it can also be controlled by moving the lens.

〔Effect of the invention〕

As described above, according to the laser beam printer control device of the present invention, a linear imaging center is provided in the non-image area of the photoconductor to detect the entire beam diameter, and based on the detection timing, the photoconductor is Since the writing timing is controlled, it is possible to prevent deterioration of the image quality based on the control of the laser beam diameter, and it is also possible to align the writing position.

[Brief explanation of the drawing]

Figure 1 shows a conventional laser printer with −<iJ? 2 is a configuration diagram showing an embodiment of the present invention, FIG. 3 is a layout diagram of the 7) near imaging sensor of the present invention with respect to the scanning line, and FIG. 4 is a flowchart showing the processing of the 6th invention. . Explanation of symbols 1... Semiconductor laser, 2... Collimator lens 3
...Rotating polygon mirror, 4...Fθ lens, 5...Photoconductor, 11*15+17+19...Drive circuit, 12.
...Amplifier, 13...A-D converter, 14...Control circuit, 16.18...Motor, 20...Comparison circuit. Figure 1 Continuation of page 1 ■Int, C1, 4 identification symbol Internal office reference number // G
03 G 15/22 103 E-7907-2H@
Inventor: Hiroshi Ishikawa, 2274 Hongo, Ebina City, 0 Inventor: Hiroshi Osawa, 2274, Hongo, Ebina City, 0 Inventor: Masuhisa Hagiwara, 2274 Hongo, Ebina City
Banjo area 1 Fuji Xerox Co., Ltd. Ebinako 1 Fuji Xerox Co., Ltd. Ebinako 1 Fuji Xerox Co., Ltd. Ebinako

Claims (1)

[Claims] A laser beam printer that modulates a laser beam according to recorded information and scans a photoreceptor based on the modulated beam through an optical system having a deflection means to form an electrostatic latent image on the photoreceptor. a linear image sensor that is placed near a non-image area of the body and outputs a beam diameter signal according to the beam diameter of an incident laser beam; and a linear image sensor that outputs a beam diameter signal according to the beam diameter of an incident laser beam; A laser characterized in that the laser comprises a control unit that outputs a write start signal for starting the beam diameter signal, compares the beam diameter signal with a predetermined level, and outputs a control signal for controlling the beam diameter based on the difference. Beam printer control device.