JPS6356451A - Laser recorder - Google Patents

Abstract

PURPOSE:To obtain a laser recorder which is capable of more stable and higher quality recording by controlling the bias current and light-emitting current of a semiconductor laser current respectively. CONSTITUTION:If an automatic light quantity adjustment signal 113 is transmitted from a central processing unit 101, a laser light quantity comparison control circuit 102 clears all input signal D1-Dn, B1-Bn to D/A conversion circuits of a light-emitting control circuit 105 and a bias current control circuit 103, and reduces to a sufficiently small value a laser current I1 (light emitting current ID + bias current IB) which passes to a semiconductor laser 108 via a light- emitting constant current circuit 106 and a bias constant current circuit 104. A video signal 116 which is an image signal is set to 'tire', and the gate of a switching circuit 107 is opened so that a light-emitting current may flow to the semiconductor laser 108. The light-emitting current control circuit 105 and the bias current control circuit 103 are provided with a circuit which converts a digital value to an anlong value of a D/A converter, and are capable of changing a laser current I which flows in the laser by an electric value (analog value) which is equivalent to a count up or count down.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser recording device, and more particularly to a laser recording device having an automatic laser light intensity control function.

[Prior Art] Conventionally, a laser beam printer is generally known as this type of laser recording device. This printer forms an electrostatic latent image by exposing and scanning a photoreceptor using laser light that is modulated according to input information, and this electrostatic latent image is developed using a magnetic developer called toner. The image is transferred onto a recording material such as paper.

FIG. 12 shows an example of the conventional laser beam printer mentioned above. In the figure, reference numeral 1 denotes a photosensitive drum having a semiconductor layer such as selenium or cadmium sulfide on its surface, which is rotatably supported in a housing H, and rotates at a constant speed in the direction of arrow A in the figure. 2 is a semiconductor laser that emits laser light, and 2A is a control circuit that controls the amount of laser light and turning on/off of the semiconductor laser 2 in accordance with human power information.

Laser light emitted from the semiconductor laser 2 is incident on the beam expander 3 and becomes laser light with a predetermined beam diameter. This laser light is incident on a polyhedral mirror 4 having a plurality of mirror surfaces. Since this polyhedral mirror 4 is rotated at a predetermined speed by a low-speed rotation motor (scanner motor) 5, the laser beam emitted from the beam expander 3 is reflected by this polyhedral mirror 4 rotating at a constant speed and is directed substantially horizontally. scanned. Next, the laser beam is imaged as a spot light by an imaging lens 6 having an f-θ characteristic onto a photosensitive drum l which is charged to a predetermined polarity by a charger 13.

A beam detector 7 detects the laser beam reflected by the reflecting mirror 8. The timing of the modulation operation of the semiconductor laser 2 to obtain desired optical information on the photosensitive drum 1 is determined by the detection signal of the beam detector 7 described above.

On the other hand, an electrostatic latent image is formed on the photosensitive drum l by the laser light that is imaged and scanned in accordance with the above-mentioned manual information. After this latent image is developed with toner in the developing device 9,
The image is transferred onto a recording material (generally paper) fed from one of the cassettes 10 and 11. Thereafter, this recording material passes through the fixing device 12, so that the image is fixed on the recording material and is discharged to a discharge section (discharge tray) not shown.

By the way, in such a laser beam printer,
The characteristics (1-1 characteristics) of the amount of laser light with respect to the laser current (drive current) of commonly used semiconductor lasers are as follows:
It is as shown in FIG. That is, as shown in FIG. 13, a semiconductor laser does not emit laser light until the laser current I reaches a certain darkness value (Ith), but it emits laser light when the darkness value is exceeded, and in that laser emission state. is the laser light Nfl for the laser current ■
has a certain slope α. This α is called slope efficiency.

In the laser beam printer, the control circuit 2A controls the amount of light from the semiconductor laser 2, and determines the laser current 1 so that the amount of light flT becomes a specified amount. At this time, by driving the laser current (7) at a constant current, the laser beam Rfl is kept constant.

[Problems to be Solved by the Invention] However, as shown in FIG. 14 in I-jZ characteristics, a semiconductor laser initially has a characteristic A.
The laser current is adjusted to a predetermined specified light amount uTA.
When driving at constant current with TA, the I-1 characteristic changes to B or C as the semiconductor laser chip temperature rises due to current flowing through the semiconductor laser. Sometimes.

Therefore, when the required prescribed light ff1lTA is scanned on the photosensitive drum l, it is normal, but the I-n characteristic is the 14th
If the changes occur as shown in the figure, and the laser light intensity increases as shown in B and decreases as shown in B despite the laser current (7), a situation may occur in which the latent image described above is not formed. , C, when the amount increases to l1Tc, there is a risk of the laser chip being destroyed.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a laser recording device that can perform more stable and high-quality recording by controlling the bias current and the light emission current of the semiconductor laser.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a recording means 7 for recording information using a semiconductor laser and a photoreceptor, and a drive current channel for driving the semiconductor laser. The bias current and the emission current are each controlled independently, and at least one of the bias current and the emission current is controlled when the photoreceptor is stopped or within a certain period of time before and after the photoconductor is stopped, so that the current flowing to the semiconductor laser is sufficiently controlled. The present invention is characterized by comprising a semiconductor laser drive current control means for reducing the size of the semiconductor laser drive current.

[Function] In the present invention, since the laser current flowing through the semiconductor and laser is made sufficiently small when the photoconductor is stopped or for a certain period of time before and after the photoconductor is stopped, the life of the semiconductor laser can be extended, and the photoconductor is stopped. Even if the door is opened, laser radiation to the outside of the device can be prevented.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the main circuit configuration of an embodiment of the present invention.

In FIG. 1, a central processing unit (CPU) 101 performs overall control of information recording processing. Reference numeral 102 denotes a laser light intensity comparison control circuit, which consists of a one-chip microcomputer with a built-in A/D (analog-digital) conversion circuit. Take control. 103
is one output 81 to B of the laser light amount comparison control circuit 102
This is a bias current control circuit having a D/A (digital-to-analog) conversion circuit connected to n. Reference numeral 104 denotes a bias constant current circuit controlled by the circuit 103, into which a bias current 8 is input. Further, 105 is a light emission current control circuit having a D/A conversion circuit connected to the other output of the laser light amount comparison control circuit 102 and -On. 10
6 is a light emitting constant current circuit controlled by the circuit 105, and the light emitting current 10 is manually supplied via the light emitting current switching circuit 107.

108 is a semiconductor laser, and 109 is a photodiode that receives the laser beam from the laser 108. 110 is a laser light amount monitor circuit supplied with a detection signal from the photodiode 109, and a voltage vM corresponding to the detected light amount
is output to the laser light amount comparison control circuit 102. 111
This is a laser light amount setting circuit that sets the laser light amount. 121 is an AND gate, and 122 is an OR gate.

Next, the operation of the laser light amount comparison control circuit 102 described above will be explained with reference to the flowchart of FIG.

Central! When the automatic light amount adjustment start signal (APC5T) 113 is sent from the A control unit (CPU) 101 (step 201), the laser light amount comparison control circuit 102 performs step 2.
At 02, the input signal [1°~
Clear all Dn%B, ~Bn, and thereby the light emitting constant current circuit 106 and the bias constant current circuit! Through 04,
The laser current ■t (emission current ll1l+bias current ts) flowing through the semiconductor laser 108 is set to a sufficiently small value (for example, the laser current LA is set within the laser generation region). In the next step 203, the video signal (Video (LON) signal) 116, which is an image signal, is
As RIJE (true), the gate of the switching circuit 107 is opened so that a light emitting current flows through the semiconductor laser 108.

Here, the light emission current control circuit 105 and the bias current control circuit 103 have a circuit such as a D/A converter that converts a digital value into an analog value as described above, and the output signal from the laser light amount comparison control circuit 102 is p, ~Do
By counting up or down the digital value constituted by The circuit configuration allows only the amount of electricity (analog value) to be changed.

In this embodiment, as shown in FIG. 4(A), the bias count value xIl counted by the bias current control circuit 103 is the output 8
It is considered to be an n-bit binary number with 1 as the least significant bit (LSD) and Bo as the most significant bit (MSB), and an expression of counting up and down by bias count value x 8 is used. FIG. 4(A) shows a state in which the bias count value XB is counted up. here,
°゛0” OW (low) level: FALSE
and °°1” is the old gh (high) level: TRIIE
(true). Furthermore, the relationship between the bias count value XB and the bias current 8 described above is as shown in FIG. 4(B).
shall increase. Also, the luminescence count value XI) and the luminescence current ■. It is assumed that the relationship is similar to that shown in FIG. 4(B).

Furthermore, the light emitting state of the semiconductor laser 108 is determined by the laser device 11.
The photoelectric conversion is carried out by the photodiode 109 built in the laser light intensity monitor circuit 110, and the light intensity-voltage characteristic monitor voltage as shown in FIG.
4, it is fed back to the laser light amount comparison control circuit 102.

Now, in step 202 described above, the bias count value XB and the emission count value X are determined. After both are set to "0", bias current control is performed in steps after step 203.

In the bias current control, the light emitting current count is X, as shown in area A in FIGS. 2(A) and 2(B). is set to “0”, bias current count value x11 is set to “1’°
(step 204)
), a current (laser current) corresponding to the counted up count value XB is caused to flow through the semiconductor laser 108 by the bias constant current circuit 104. The detected value of the amount of laser light associated with the laser current is fed back to the laser light amount comparison control circuit 02 through the laser light amount monitor circuit 110.

The laser current of the semiconductor laser 108 is the threshold current Ith.
ei! When A is reached, laser light is emitted. Furthermore, the bias current count value X8 is counted up to increase the current flowing through the semiconductor laser 108. Thereafter, when the monitor voltage vM reaches the bias current regulation voltage vno, the count-up of the bias current count value Xa is ended (step 205).

The bias current count value at this time is defined as Xao (bias current specified count value). When XI is XaO, the laser 108 is emitting laser light, and there are cases where the amount of light is sufficient to form a latent image on the photosensitive drum 1. Therefore, the bias current is within the bias current specification. The count value xBo is multiplied by a certain percentage (for example, 80%), and the resulting value is set as XIIT (step 206).・The laser 108 is the above-mentioned Xa
A current corresponding to the bias current setting count value) is flowing, and the current at this time is defined as a bias setting current 1117. While the bias setting current 18T is flowing through the semiconductor laser 10B, monitor voltage VM is checked, and the absolute value of the value obtained by subtracting the monitor voltage vM from the bias current specified voltage VBO is a certain percentage (α) that is equal to the voltage VBo. If the multiplied value exceeds ■8°×α (step 207
), return to step 202, set the bias current count value x 5 to "0", stop the laser current, and restart the bias current control from the beginning. That is, with the bias setting current I.T flowing through the semiconductor laser 108, Perform light emission current control. At this time, TR
IJE, the gate of the light emitting current switching circuit 107 is opened, and the light emitting current]. is kept flowing to the semiconductor laser 108.

Next, lva. If the calculation formula -VM l≦VB×α is established, the process proceeds from step 207 to step 208.

The light emission current control at this time is performed by setting the bias current count value X8 to the bias current setting count value x8, as shown in area B of FIGS. 2(A) and (B), and
This is done with the bias setting current IBT flowing through 08.

Light emitting current count value X. is counted up by "1" from the "0" state (step 208).The current I corresponding to the count value XO obtained by this count-up is
. The bias specified current TB is set by the light emitting constant current circuit 106.
Add it to the ding. Therefore, the laser current IJ2 is equal to the bias regulation current IBT and the light emission current l. (L
2・181+io).

The amount of laser light accompanying the laser current 1j2 is determined by the photodiode 10 built in the semiconductor laser device 112.
9, and the laser light amount monitor circuit 110 feeds back to the laser light amount comparison control circuit 102. Therefore, the light emitting current count value XD is set to “1”.
By counting up the luminescent current I.

increases, and the amount of laser light increases.

Next, monitor voltage ■ to see if the laser light intensity has increased. Detected by an increase in That is, the light emitting current count value XO is counted up, the current flowing through the laser 108 is increased, and the monitor voltage VM becomes the light emitting light amount specified voltage (2). At the point in time, the count up of the light emitting current count value XO is terminated (step 209).

The light emitting current count value at this time is assumed to be X0 (light emitting current setting count value). A current corresponding to XDT (light emission current setting count value) flows through the semiconductor laser 108, and the light emission current at this time is defined as the light emission setting current IDT. The monitor voltage vM is checked while the emission setting current IDT is flowing through the semiconductor laser 108. That is, if the monitor voltage v2 is not within a certain range (for example, ±5%) with respect to the light emitting light amount regulation voltage vo (step 2
1O), the light emitting current count value X111 is cleared (step 211), and the light emitting current I is cleared. stop, step 2
Return to step 08 and perform the light emitting current control again.

When the monitor voltage vM is within a certain range with respect to the light emitting light amount regulation voltage VD, and the PC5T signal from the central processing unit 101 is FALSE, the light emitting current setting count value XD'r and the bias current setting While holding the count value Xat, the gate of the light emitting current switching circuit 107 is closed, and the current to the semiconductor laser 108 is set to only the bias setting current IBT. In addition, the above A
When the PC5T signal is TRIIE, the gate of the light emitting current switching circuit 107 is left open and the A
The gate is closed when the PC5T signal becomes FALSE.

The above-mentioned emission light amount regulation voltage V is determined as follows.

First, the laser light amount setting voltage v0 is determined by the laser light amount setting circuit 111. This voltage ■.

As shown in FIG. 6, a voltage based on resistance division can be considered. A set voltage V input to the laser light amount comparison control circuit 102. is corrected by the difference in laser sensitivity of the photosensitive drum 1 in the recording apparatus. The sensitivity of the photosensitive drum 1 is determined from the central processing unit 1 by C3EN1. It is input as a signal 11'4 indicated by C3EN2. The correction value for vo is, for example, +10% or -10% with respect to the central value of vo.
The corrected value is set as the emitted light amount regulation voltage v0.

Furthermore, as shown in FIGS. 7(A) and (B), the laser current IL is increased by counting up the bias count value xIS, and the bias count value x8
Even at time T8 when the current IBM has reached its maximum value (MAX), if the monitor voltage V does not reach the bias current specified voltage v6°, the current IBM
(current when the current reaches AX) or a predetermined ratio value of the current IBMMAX is set as the bias current.

Further, the light emitting current is controlled in a state where a predetermined bias current is flowing in the light emitting current. By counting up the light emission count value xD, the laser current is increased, and the time point T when the light emission count value XO reaches the maximum value is reached.
Also at D, monitor voltage V. If the light emission amount does not reach the specified voltage Vo, the light emission current control is ended while the current IDMAX (the light emission current when the light emission count value reaches MAX) is flowing.

FIG. 8 shows the laser drive current control circuit 50 detailed in FIG.
1 shows a circuit configuration of an embodiment other than 1.

In this figure, 503 is a scanner motor control circuit;
4 is a photosensitive drum rotation control circuit, and 505 is a photosensitive drum detection circuit. Central processing unit (cpu) t is the well-known P
A scanner motor control circuit 503 and a photosensitive drum rotation control circuit 504 are controlled using a control integrated circuit such as LL.
, and a photosensitive drum detection circuit 505 using a microswitch, a photointerrupter, and the like. In addition, CPII 101 is a print control signal (PRINT) 50 from an external control device such as a control console or reader.
6, a video signal (Video) 507, and a test signal (MLON) 508 from an external control device, and according to these signals, the laser drive current control circuit 501 is controlled as shown in FIG. ing.

Next, the control operation of the CPU 101 described above will be explained with reference to the timing chart of FIG. 9 and the flowchart of FIG. 1O.

First, in step 601, a signal P is sent from an external control device.
If RIN 7506 is input, in step 602, the drum drive signal ([1RIID) 513 and scanner motor drive TBJ signal (5CNON) 509 are set to Tl1tl.
Make it E. Next, in step 603, a signal 5CN indicating that the scanner motor 5 is ready is sent.
After confirming that RflY510 has become TRIJE,
In the following step 604, automatic light amount adjustment starts No. 8 (APC
5T) Set +13 to TRLIE.

Then, in step 605, the laser light amount comparison control circuit 102 of the laser drive current control circuit 501 automatically adjusts the light amount of the semiconductor laser 108, as described in detail above. After that, the drum drive signal (DRMD) 5i3 is
LSE state or scanner motor rotation ready signal (
SCNRY) 510 becomes F-Sε (step 606), in the next step 607, the bias count value x8 and the emission count value xo are cleared through the laser light amount comparison control circuit 102, and the current flowing through the semiconductor laser 108 is control so that it is sufficiently small.

At this time, the drum drive signal (DRMD) 513 is FAL.
The process in step 607 may be performed at the time when SE becomes SE or during a certain period of time before and after becoming FALSE.

Further, during continuous printing, the signal APC5T 113 becomes TRIIE during the period between prints, that is, in the non-image area between sheets of paper, and the automatic light amount adjustment is completed during the non-image area. Also, for a certain period of time T
If there is no timing at which the signal APC5T 113 is generated beyond APC, automatic light amount adjustment is performed after that TAPC time. Signal TOPER601 in FIG. 11 indicates the above-mentioned non-image area.

[Effects of the Invention] As explained above, according to the present invention, the laser current flowing through the semiconductor laser is sufficiently reduced when the photoreceptor is stopped or during a certain period of time before and after the photoreceptor is stopped, thereby extending the life of the semiconductor laser. Furthermore, even if there is a door oven or the like when the photoreceptor is stopped, the effect of preventing laser radiation to the outside of the apparatus can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the laser drive current control circuit according to the embodiment of the present invention, FIG. 2 is a characteristic diagram showing the operation of the laser drive current control circuit of FIG. 1, and FIG. A flowchart showing the operation of the light amount comparison control circuit; FIGS. 4(A) and 4(B) are diagrams showing the relationship between the bias count value (or light emission count value) and the bias current (or light emission current) in the embodiment of the present invention; FIG. 5 is a characteristic diagram showing the relationship between the laser light amount and monitor voltage in the embodiment of the present invention, FIG. 6 is a circuit diagram showing a configuration example of the laser light amount setting circuit of FIG. 1, and FIGS. 7(A), (B) ) is a characteristic diagram showing the operation of the laser light amount comparison control circuit shown in FIG. 1, FIG. 8 is a block diagram showing the configuration of other circuits according to the embodiment of the present invention, and FIG. 9 is an output signal of the circuit shown in FIG. 8. 10 is a flowchart showing the operation of the central processing unit of FIG. 8, FIG. 11 is a timing chart of the output signal of the circuit of FIG. 8, and FIG. FIG. 13 is a characteristic diagram showing the relationship between the amount of light and the current of the semiconductor laser; FIG. 14 is a characteristic diagram showing the relationship between the amount of light and the current of the semiconductor laser. 101...Central processing unit, 102...Laser light comparison ho 1'' control circuit, 103...
- Bias current control circuit, 104... Bias constant current circuit, 105... Light emission current control circuit, 108... Light emission constant current circuit, 107... Light emission current switching circuit, 108...
Semiconductor laser, 109... Photodiode, 110... Laser light amount monitor circuit, 111... Laser light amount setting circuit, 501... L noser control circuit (laser drive current control circuit), 503... Scanner motor Control circuit, 504... Photosensitive drum rotation control circuit, 505... Photosensitive drum detection circuit. MSB Xs72-t=1 1 ------- 7 7
7 ability-filled Xβ and b-1 engineering Xo and Io μI system Σ
[Fig. 4] Monitor groove E 1 shows the actual output μ'.
Fig. 5: Block diagram of 9-constant 1 circuit/1 point Rotating printing I gamma cut special / 1 raw diagram Figure 7 staff and child 1 jq middle history πV village showing the flow of the equipment Figure 1 Figure 13: Bamboo pressure map of light t against -L-The Takumi

Claims (1)

[Scope of Claims] A recording means for recording information using a semiconductor laser and a photoreceptor; a bias current and a light emitting current among drive currents for driving the semiconductor laser are each independently controlled; semiconductor laser drive current control means for controlling at least one of the bias current and the light emitting current to sufficiently reduce the current flowing through the semiconductor laser when the laser is stopped or within a certain period of time before and after the stop. A laser recording device characterized by: