JPS6356452A - Laser recorder - Google Patents

Abstract

PURPOSE:To obtain a laser recorder which is capable of more stable and higher quality recording by performing current control so that a prearranged propor tional value of a laser current value may be set to a bias current value of the laser current when a light quantity monitor voltage has reached a prear ranged specific voltage level. CONSTITUTION:A semiconductor laser 108 emits a laser beam when a laser current has exceeded a threshold current Ith. Further, a bias current count value XB is counted up to increase an electric current which flows into the semiconductor laser 108. After this, the counting-up of the bias current count value XB is terminated when a monitor voltage VM has reached a specified bias current voltage VBO. At that time, the bias current count value is supposed 'XBO' (specified bias current count value). When there is a condition in which XB is XBO, the laser 108 emits a laser beam and also there are cases that the laser emits a light quantity which is enough t form a latent image on a photosensitive drum 1, the bias current should be equivalent to a value obtained by multiplying the specified bias current count value XBO by a certain fixed rate.

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. 7 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 laser sight and turning on and 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-theta characteristic on the photosensitive drum 1, which is charged with a predetermined polarity by a charger 13.

A beam detector 7 detects the laser beam reflected by the reflection 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 replacement image is formed on the photosensitive drum 1 by the laser light that is image-formed and scanned in response to the above-mentioned manual input (i'f information). After the image is developed, it is transferred onto a recording material (generally paper) fed from either cassette to or 11. Thereafter, this recording anchor material passes through a fixing device 12. The image is fixed on the recording material, and the image is fixed on the recording material.
is discharged.

By the way, in such a laser beam printer,
The characteristic (If characteristic) of the amount of laser light with respect to the laser current (drive current) of a commonly used semiconductor laser is as shown in FIG. That is, as shown in FIG. 8, the semiconductor laser has a laser current I at a certain threshold (It
Until h), laser emission is not performed, but laser emission is performed when the threshold value is exceeded, and in that laser emission state, the laser sight degree C with respect to the laser current I 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 I↑ so that the amount of light becomes a specified amount AT. At that time, the laser current I
By driving 7 with a constant current, the laser beam fc i T
I try to keep it constant.

[Problems to be Solved by the Invention] However, as shown in FIG. 9 in II characteristics, a semiconductor laser initially has a characteristic A, and the laser current must be adjusted to a predetermined prescribed light amount - QTA. ITA
When the semiconductor laser is driven at a constant current, the -1 characteristic changes to B or C as the semiconductor laser chip temperature increases due to current flowing through the semiconductor laser. There is.

Therefore, when the required prescribed light intensity is scanned on the photosensitive drum 1, it is normal, but the I-j2 characteristic changes as shown in Fig. 14, and the laser current changes even though the laser current is When the amount of light decreases to λ B as shown in B, a situation may occur in which the latent image described above is not formed, and when it increases to flTc as shown in C, the laser chip may be destroyed. There is a risk that this may occur.

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 for recording information using a semiconductor laser, and a laser light amount detection means for detecting the light amount of the semiconductor laser as a light amount monitor voltage. In the process of changing the laser current that drives the semiconductor laser, a predetermined percentage value of the current value of the laser current when the light intensity monitor voltage reaches a predetermined specific voltage is determined as the current value of the bias current of the laser current. The present invention is characterized by comprising a laser drive current control means for controlling the current.

[Function] In the present invention, since the laser current is changed and the predetermined ratio at the time when the monitor voltage reaches a specific voltage is set as the laser bias current, the bias current of the semiconductor laser can be controlled more accurately. be able to. Therefore, according to the present invention, as in the fixed bias method, the threshold value rises depending on the temperature characteristics of the semiconductor laser and the bias current does not have a sufficient bias current effect, or the threshold value is too small and the laser There is no situation where light is emitted.

[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, 101 is a central processing unit (CPU) that performs overall control of information recording processing. Reference numeral 102 denotes a laser light intensity comparison control circuit, which is composed of a one-chip microcomputer with a built-in A/D (analog-to-digital) conversion circuit, and controls the laser light intensity as shown in FIG. 2 in accordance with the control procedure shown in FIG. 3, which will be described later. I do. Reference numeral 103 denotes a bias current control circuit having a D/^ (digital-to-analog) conversion circuit connected to one of the outputs B, .about.Bn of the laser light amount comparison control circuit 102. 104 is the circuit 10
This is a bias constant current circuit controlled by 3, and the bias current 2 is input. Further, 105 is a D/D connected to the other outputs D1 to D of the laser light amount comparison control circuit 102.
This is a light emission current control circuit having an A conversion circuit. 106 is a light emitting constant current circuit controlled by the circuit 105, and the light emitting current I is controlled by the light emitting current switching circuit 107.
I) is done manually.

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 7-voltage VM corresponding to the detected light amount.
is output to the laser light amount comparison control circuit 102. 111
is a laser light amount setting circuit that sets the laser light amount. 1
21 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.

When the automatic light amount adjustment start signal (APC5T) 113 is sent from the central processing unit (CPU) 101 (step 2
01), the laser light amount comparison control circuit 102 receives input signals from the D/A conversion circuits of the light emission current control circuit 105 and the bias current control circuit 103 in step 202.

〜Do, B, and 〜Bn are all cleared, so that the laser current Iλ(
Luminous current I. +bias current IB) to a sufficiently small value (for example, set laser current 1 within the laser emission region). In the next step 203, a video signal (Video (LON) (number a) 116 which is an image signal)
is set to 1'RUE (true), and 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 for converting a digital value such as a D/8 converter into an analog value as described above, and the output from the laser light amount comparison control circuit 102 is Signal, ~D0
By counting up or down the digital value constituted by The circuit has a circuit configuration that can change the amount of electricity (analog value).

In this embodiment, as shown in FIG. 4(A), the bias count value X8 counted by the bias current control circuit 103 is the output B of the laser light amount comparison control circuit 102.
It is considered to be an n-bit binary number, with bit number being the least significant bit (LSB) and Bn being the most significant bit (MSB), and the bias count value XB is expressed as counting up and counting down. FIG. 4(A) shows a state in which the bias count value X8 is counted up. Here, '0' is Low level: LSE to F (
False), and “1゛′ is Ilight (high) level: T
Set to RUE (true). Furthermore, the relationship between the bias count value xB and the bias current I mentioned above is shown in FIG. 4 (CB), and it is assumed that the bias current 8 increases as the bias count value XB increases. It is also assumed that the light emission count value Xo and the light emission current In have the same relationship as shown in FIG. 4(B).

Furthermore, the light emitting state of the semiconductor laser 108 is determined by the laser device 11.
2 is photoelectrically converted by the photodiode 109 built in, and processed by the laser light amount monitor circuit 110 to produce a monitor voltage V with the scene-voltage characteristic as shown in FIG.
It is fed back to the laser light amount comparison control circuit 102 as M.

Now, after both the bias count value X8 and the emission count value XO are set to "0" in step 202 described above, bias mainstream 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" and the bias current count value xB is counted up by "1°" (step 204).
, and the current (laser current) corresponding to the counted up count value X is caused to flow through the semiconductor laser 108 by the bias constant current circuit 104. A detected value of the laser light amount associated with the laser current is fed back to the laser light amount comparison control circuit 102 through the laser light amount monitor circuit 110.

The semiconductor laser 108 has a laser current equal to the threshold current Itl.
When + is pressed, laser emission is performed. Furthermore, the bias current count value X 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 VBO, the count-up of the bias current count value X8 is ended (step 205).

The bias current count value at this time is defined as Xao (bias current specified count value). In the state where The count value XBO is multiplied by a certain percentage (for example, 80%), and the resulting value is set as X67 (step 206).

A current corresponding to the above-mentioned Xat (bias current setting count value) flows through the laser 108, and the current at this time is defined as a bias setting current 111T. Semiconductor laser 108
Check the monitor voltage vM while the bias setting current IBT is flowing through the voltage VBO.
If it exceeds the value vaoxα multiplied by a certain percentage (α) (step 207), step 202
Return to , clear the bias current count value XB to “0” and set the laser voltage? Stop F and restart bias current control from the beginning. That is, light emission current control is performed with the bias setting current IBT flowing through the semiconductor laser 108. At this time, the Video signal is set to TR11E, the gate of the light emitting current switching circuit 107 is opened, and the light emitting current 10 is kept flowing to the semiconductor laser 108.

Next, Iva. 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 XBT, as shown in region B of FIGS.
This is done with the bias setting current IBT flowing through 08.

The light emitting current count value XO is counted up by "1" from the "0" state (step 208). A current In corresponding to the count value XD obtained by this count-up is applied to a bias specified current I
Add to BT. Therefore, the laser current 1j2 is the bias regulation current rat and the light emission current ■. (
IJ2-1ay+I,).

The amount of laser light accompanying the laser current IJZ 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 XO is set to “1”.
By counting up step by step, the light emitting current ID
increases, and the amount of laser light increases.

Next, an increase in the amount of laser light is detected by an increase in the monitor voltage vM. That is, the light emitting current count value XD is counted up, the current flowing through the laser 108 is increased, and the monitor voltage VM becomes the light emitting light amount regulation voltage V. 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 X. T (emission current setting count value). A current corresponding to XDT (emission current setting count value) flows through the semiconductor laser 108, and the emission current at this time is called the emission setting current I. Set it to 7. While the emission setting current IDT is flowing through the semiconductor laser 108, the monitor voltage VM is checked. That is, the monitor voltage VM is the light emission amount regulation voltage V. If it is not within a certain range (for example, ±5%) (Step 2
10), clear the light emitting current count value xD (step 211), stop the light emitting current It, and perform step 20.
Return to step 8 and redo the light emitting current control.

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 XDT and the bias current setting count value While holding XIIT, 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 1117. Also, the APC5T signal mentioned above is TRL! In case E, the gate of the light emitting current switching circuit 107 is left open,
APC5T (Close the gate when No. 3 becomes FALSE.

The above-mentioned light emitting light amount regulation voltage Vo is determined as follows.

First, the laser light intensity is set by the laser light intensity setting circuit 111.
rEVO is determined. This voltage V.

As shown in FIG. 6, a voltage based on resistance division can be considered. Setting voltage ■ 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 input from the central processing unit 1 as signals 114 indicated by C3ENI and C3EN2. The correction value for vo is, for example, a value of +10% or =10% with respect to the center value Vo, and the value obtained by correcting Vo is the emitted light amount regulation voltage (■). shall be.

[Effects of the Invention] As explained above, according to the present invention, since the laser current is changed and the predetermined ratio at the time when the monitor voltage reaches a specific voltage is set as the first laser bias current, It is possible to accurately control the bias current of the semiconductor laser. Therefore, according to the present invention, as in the fixed bias method, the threshold value rises depending on the temperature characteristics of the semiconductor laser and the bias current does not have a sufficient bias current effect, or the threshold value is too small and the laser There is no situation where light is emitted.

[Brief explanation of the drawing]

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 optical two comparison control circuit, FIG. 4 (8), CB) shows the bias count value (or light emission count value) and bias current (
5 is a characteristic diagram showing the relationship between the laser light amount and the monitor voltage according to the embodiment of the present invention. FIG. 6 is a circuit showing an example of the configuration of the laser light amount setting circuit shown in FIG. 1. Figure 7 is a perspective view showing the configuration of a conventional laser recording device, Figure 8 is a characteristic diagram showing the relationship between the light amount and the current of the semiconductor laser, and Figure 9 shows the relationship between the optical device and the current of the semiconductor laser. It is a characteristic diagram. lot...Central processing unit, 102...Laser light amount comparison control circuit, 103...Bias current control circuit, +04...Bias constant current circuit, +05...Emission current control circuit, 106...Light emission constant TL current circuit, 107... light emitting current switching circuit, ioa...
Semiconductor laser, 109... Photodiode, 110... Laser light amount monitor circuit, 11! ...Laser light intensity setting circuit. MSB Xa72-t=1 7 ------- 7 1 1
Fig. 4 shows the μ line system of tr +
Sutoku・Darazu 15V Kabo Ig'J /l L-The most common ax 9 stab circuit 0 Hug=
Figure 6 Figure 7 Block diagram of ``J''
Figure 9

Claims (1)

[Scope of Claims] 1) Recording means for recording information using a semiconductor laser; Laser light amount detection means for detecting the light amount of the semiconductor laser as a light amount monitor voltage; and Changing the laser current for driving the semiconductor laser. a laser drive that performs current control such that a predetermined percentage value of the current value of the laser current when the light amount monitor voltage reaches a predetermined specific voltage is set as the current value of the bias current of the laser current in the process of increasing the light intensity; 1. A laser recording device comprising current control means. 2) A laser recording device according to claim 1, wherein the specific voltage is a light amount monitor voltage corresponding to the light amount of a laser emitting region of the semiconductor laser. 3) In the device according to claim 1 or 2, the predetermined ratio value is 100% or less, and when the bias current is applied to the semiconductor laser, the semiconductor laser becomes a laser beam. A laser recording device characterized by a value that does not emit light. 4) In the device according to any one of claims 1 to 3, when the laser drive current control means sets the bias current to be outside the laser emission region, . A laser recording apparatus, characterized in that when the light amount monitor voltage exceeds the characteristic voltage or a predetermined ratio of the specific voltage, current control is performed to sufficiently reduce the laser current. 5) In the device according to any one of claims 1 to 3, when the laser drive current control means sets the bias current to be outside the laser emission region, A laser recording device characterized in that when the light amount monitor voltage exceeds the specific voltage or a predetermined ratio of the specific voltage, the bias current is adjusted again after the laser current is sufficiently reduced.