JPS61166085A - Discriminating circuit for life of laser - Google Patents

Abstract

PURPOSE:To determine life corresponding to a laser used precisely by giving a control section an alarm on the life of the laser when the supply voltage of an amplifier in an AOM driver is lowered to voltage lower than a controllable limit value by a predetermined voltage section. CONSTITUTION:When the driving time of a laser-beam generating section 1 is increased and an output P from laser power gradually lowers, modulation efficiency eta augments by the operation of a level control circuit in order to keep the output level Pd of laser beams on the surface D of a photosensitive body constant. That is, the supply voltage Vrf of an optical modulation element (AMO)2 and an amplifier (AMP)22 in a driver 21 also increases simultaneously, and the voltage Vrf is applied to one terminal for a comparator 26, and compared with voltage E1. The reference voltage (E1+E2) of a comparator 20 is set at a value equal to limit voltage Vrf' where modulation efficiency etacan be controlled, but the reference voltage E1 of the comparator 26 is set at a value lower than that by voltage E2. When the output P from laser power lowers and voltage Vrf reaches Vrf>E1, the comparator 26 transmits a laser-life signal through which the expiration of the life of a laser in a short time is messaged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus having a laser beam generating circuit for scanning a photoreceptor at predetermined intervals for recording information, and particularly relates to a device having a laser beam generating circuit for scanning a photoreceptor at predetermined intervals for recording information. The present invention relates to a laser lifespan determination circuit that accurately determines the lifespan of a generated laser using a simple hardware configuration.

For example, in a laser printer, which is one of the printing devices that make up an information processing system, it is necessary to control the level of laser light to a certain size in order to keep the print density constant in the printer. When a laser reaches the end of its lifespan, it becomes impossible to control its output level.

Therefore, it is desired to put into practical use a discrimination circuit that accurately determines the lifespan of a laser with a simple circuit configuration.

[Prior art and problems to be solved by the invention] A laser printer will be explained as an example of the prior art.

Fig. 2 is a diagram of a conventional laser beam level control circuit for a laser printer, Figs. 3 and 4 are waveform diagrams at each point of the laser beam level control circuit, Fig. 5 is a diagram explaining the laser beam detection circuit, and Figs. 6 each shows an explanatory diagram of the operation of the driver of the optical modulation element.

AOM that drives the light modulation element (hereinafter referred to as AOM) 2
The driver 21 has 9 oscillators (hereinafter referred to as O3C) 2
4 (High frequency oscillator such as 80MHz, 200Mtlz)
The output of the control unit (not shown in the figure) is sent to the mixer circuit 2 by the "1" and "0" signals of the printing dot signal sent from the relay.
3, and an amplifier (AMP) 22.
P) Outputs a driving power Prf of 40M2 according to a power supply voltage Vrf of 22. Incidentally, FIG. 3 shows the state of these signal waveforms.

That is, as shown in FIG. 6(B), 80M driver 2
1 internal amplifier (AMP) 22 power supply voltage Vrf and 40M
By controlling the power supply voltage Vrf by utilizing the proportional relationship between the drive power Prf of 40M2 and the drive power Prf of 40M2
The output Pr of the AOM driver 21 is set such that the modulation efficiency η satisfies η≦ηp and the level of the laser beam is constant.
f is controlled.

Next, when the laser beam generator 1 generates a laser beam with an output level PO in response to a control signal ■ from a controller (not shown), the 40M2 modulates this laser beam with a modulation efficiency η1, and outputs a level PO. A laser beam η1 is projected onto the rotating mirror 3. The rotating mirror 3 reflects this laser light and scans the light receiving surface.

On the other hand, the photodetector circuit 4 converts the level PO·η1 of the laser beam scanned by the nine-turn mirror 3 into a voltage value prior to printing, and outputs a voltage VLPI corresponding to the level po·η1. The comparator 12 compares the VLPI with a voltage value Ec corresponding to a predetermined laser light level Pc, and outputs a signal sb when VLPI>Ec.

This signal sb is input to the fall detection circuit 13.

It detects the falling edge of the pulse of signal sb and outputs signal sb'. Further, the output voltage VLPI of the photodetector circuit 4 is waveform-shaped by the logic signal conversion circuit 11 and becomes a pulse signal Sa. Further, the signal Sa is sent to the rising edge detection circuit 14 and output as a signal Sa'.

The signal Sb' and the signal Sa' are connected to a flip-flop (hereinafter referred to as F).
J of 15 (referred to as F) is sent to the terminal, and F and F15 that receive this are reset by the signal Sa' (output "0").
level) and set by signal Sb' (output “
1” level).

The photodetection circuit 4 is activated every time the laser beam reaches the scanning start position by the rotating mirror 3, that is, every scanning period T of one line on the light receiving surface as shown in FIG. Since the level of the laser light is detected at every detection cycle 4', the signal Sa' is output in synchronization with the scanning cycle T. This means that F and F15 are reset every cycle T (the output waveform status is
(shown in figure).

In addition, FIG. 5 shows a situation in which the light receiving surface D (the light receiving surface D is from point xi to point x2) is scanned.
Scan from point to x3 points. Further, the starting position of the light-receiving surface is detected by a light detection circuit 4' located between the xO point and the x1 point.

Next, when VLPI>EcO, the signal sb' is output,
The output Sc of the Q output terminal of F, F15 becomes "1", which turns on the OR circuit 16.17, and a reverse voltage is applied between the base and emitter of transistor Qa, turning off transistor Qa, while turning off the base of transistor Qb. .

A forward voltage is applied between the emitters, turning on the transistor Qb.

As a result, the capacitor Ca is discharged via the resistor Rh. Furthermore, when the signal Sa' is output, F and F15 are reset, and when VLPI < Ec, the signal Sb' is not output, so the outputs of F and F15 remain at "0 level", thereby causing the OR circuit 16. 17 is turned off, transistor Qa is turned on, and transistor Qb is turned off.

Capacitor Ca is charged with voltage Vcc via resistor Ra.

That is, the capacitor Ca remains in a charged state until the open signal Sb' with period T is detected, and is in a discharged state from the time the signal sb' is detected until the next signal Sa' is detected. Note that the capacitor Ca is charged with a time constant of Ra.Ca and discharged with a time constant of Rh-Ca.

The terminal voltage V of the capacitor Ca controlled in this way
a is the Han impedance circuit 18. Amplifier (AMP)
19 through the AOM driver 21 internal amplifier (AM
P) is converted into the power supply voltage Vrf of 22.

As a result, the AOM driver 21 outputs power Prf according to the voltage Vrf and controls the modulation efficiency η of 40M2 so that a constant laser light level PO·η1 is obtained.

Next, when looking at the relationship between the modulation efficiency η and the power Prf of the AOM2, it is found that there is a limit value as shown in FIG. 6(A). That is, the modulation efficiency η varies in proportion to the power Prf, but becomes inversely proportional with the modulation efficiency ηp corresponding to the power Prf' being the maximum. Therefore.

The controllable range of modulation efficiency η is Prf < Prf ' (i.e., Vrf < Vr
f').

Therefore, in the comparator 20, an amplifier (8 MP) 22
Controllable limit value Vrf of power supply voltage Vrf and modulation efficiency η
When Vrf=Vrf', a signal is sent to the OR circuits 16 and 17, which are turned on and controlled to discharge the capacitor Ca.

The laser light generating section l that generates the laser light used in such important parts is equipped with a laser (for example, He-
Ne laser) is used. This laser has a standard lifespan of approximately 10,000 hours.

Conventionally, the driving time was measured by an hour meter 25.

That is, the lifetime of the laser has been predicted by measuring, using the hour meter 25, the amount of time that the control signal (2) from a control section (not shown) is on. However, since the lifespan of lasers generally varies widely, there is a problem in that simply measuring the driving time using the hour meter 25 does not allow accurate determination of the lifespan.

[Means for solving problems]

An object of the present invention is to realize a novel laser life determination circuit that solves the above-mentioned problems. A predetermined voltage lower than the drive input voltage by Δ voltage is set as a reference voltage, and a comparison means is provided for comparing the reference voltage and the input voltage for driving the light modulation element, and the input voltage for driving the light modulation element is set as the reference voltage. This problem is solved by the laser life determination circuit according to the present invention, which identifies the laser constituting the laser light generating section as having reached the end of its life when the voltage exceeds the voltage.

[Effect]

That is, before the power supply voltage Vrf of the amplifier in the AOM driver reaches the controllable limit value Vrf' of the AOM,
Voltage E lower by a predetermined voltage than the controllable limit value Vrf'
1 and the power supply voltage Vrf using a comparator, +Vrf
> El, by issuing a laser life warning to the control unit, it becomes possible to accurately know the lifespan depending on the laser being used.

〔Example〕

The gist of the present invention will be specifically explained below with reference to an embodiment shown in FIG.

FIG. 1 is a block diagram showing an embodiment of a laser life determination circuit according to the present invention.

The same reference numerals indicate the same objects throughout the figures.

9. In this embodiment, a laser (
For example, a lifespan determination circuit is added for a ) le-Ne laser), and the operation of this embodiment will be explained below, focusing on the added lifespan determination circuit.

When the laser power P of the laser beam generator 1 is initially PO, the modulation efficiency η of the AOM2 required to make the output level of the laser beam on the photoreceptor surface Pd (constant value) is η0
and an amplifier (AMP) corresponding to the modulation efficiency ηO 22
The power supply voltage Vrf of is assumed to be VrfO. Incidentally, Pd is determined by the following equation (1).

Pd = POXη0 ... (1) When the driving time of the laser light generating section l increases and the laser power output P decreases 'ζ, the output level Pd of the laser light on the photoreceptor surface is maintained constant. In order to, the modulation efficiency η
increases due to the operation of the level control circuit.

That is, the voltage Vrf also increases at the same time, and this voltage Vrf is sent to one terminal of the comparator 26 and compared with the voltage El. Note that the reference voltage of the comparator 20 (El
+E2) is the limit voltage Vr at which the modulation efficiency η can be controlled.
The reference voltage E1 of the comparator 26 is set to a value equal to f', but the reference voltage E1 of the comparator 26 is set lower by the voltage E2.

The output P of the laser power decreases, and the voltage Vrf decreases to Vrf.
>fil, the comparator 26 sends a signal ■ to a control section (not shown). This signal■ is.

This signal is identified as a laser life signal indicating that the laser life is nearing its end, and a control unit (not shown) performs display processing to request replacement of the laser.

〔Effect of the invention〕

According to the present invention as described above, there is an effect that the lifespan depending on the laser being used can be accurately determined with a simple circuit configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a laser life determination circuit according to the present invention. FIG. 2 is a conventional laser beam level control circuit diagram of a laser printer. 3 and 4 are waveform diagrams at each point of the laser light level control circuit. FIG. 5 is a diagram illustrating a laser light detection circuit. FIG. 6 is an explanatory diagram of the operation of the driver of the optical modulation element. are shown respectively. In fig. ■ is the laser beam generator, 2 is the AOM. 3 is a rotating mirror, and 4 is a light detection circuit. 11 is a logic signal conversion circuit. 12.20.26 is a comparator. 13 is a falling detection circuit, and 14 is a rising detection circuit. 15 is F, P, 16.17 is an OR circuit. I8 is a high impedance circuit. 19.22 is an amplifier (AMP), 21 is AOM
driver. 23 is a mixer circuit, and 24 is an oscillator (O5C). 25 is the hour meter. are shown respectively. Fu 3 Mimika 4 Agony f 5th 6th scream

Claims (1)

[Claims] a laser beam generator that generates a laser beam with a predetermined power; and a light modulator that modulates the laser beam output from the laser beam generator according to recorded information and changes the level of the laser beam with a predetermined modulation efficiency. In the apparatus, a predetermined voltage lower by Δ voltage than a maximum drive input voltage that provides the maximum modulation efficiency of the light modulation element constituting the light modulation section is set as a reference voltage, and the light modulation element is driven with the reference voltage. A laser comprising comparison means for comparing the input voltage with an input voltage, and when the input voltage for driving the light modulation element exceeds the reference voltage, the laser constituting the laser light generating section is identified as having reached the end of its life. lifespan determination circuit.