JP2000267029A - Optical recorder using multibeams - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an optical recorder constituted so that the printing quality is not deteriorated even when environmental temperature is changed in an optical recorder using an optical fiber. SOLUTION: This optical recorder is provided with an optical system part having plural semiconductor lasers, the optical fiber and a scanning optical system, a laser driving circuit 30 modulating light according to a data signal inputted to the respective semiconductor lasers, a light power detection means detecting the light power of the semiconductor lasers and a temperature detection means TH detecting the temperature of the optical system part. The laser driving circuit is provided with a reference voltage generation means 31 calculating reference voltage based on a signal outputted from the detection means TH and a comparison means comparing the reference voltage and a light power detection signal and deciding the driving current of the semiconductor lasers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording apparatus such as a laser printer which scans and prints a large number of beams, that is, multiple beams emitted from a plurality of semiconductor lasers.

[0002]

2. Description of the Related Art A method using a multi-beam for realizing a high-speed laser printer is effective and important technology.

FIG. 2 shows an example of a laser printer using a plurality of semiconductor lasers, particularly an optical system thereof. Reference numeral 1 denotes a semiconductor laser module, which guides laser light emitted from a semiconductor laser unit 2 to an optical fiber 3. A plurality of optical fibers are arranged in a line in the array arrangement section 4, and a plurality of beams emitted from the optical fiber array are used as a multi-beam for a laser printer. That is, the array-shaped multi-beam emitted from the array arrangement portion is a lens L1,
After passing through L2, L3, and LC1, the light enters the rotary polygon mirror 5, and the rotary polygon mirror scans the photosensitive drum 7 collectively and simultaneously. Reference numeral 6 denotes a scanning lens for narrowing the beam deflected by the rotary polygon mirror as a minute spot on the photosensitive drum 7. Reference numeral 10 denotes a spot row on the photosensitive drum 7, and 15 denotes an optical scanning line. Note that a glass plate 16 is provided at the tip of the optical fiber 3 so that a stable laser beam can be emitted even if dust or the like adheres to the tip of the optical fiber.

FIG. 3 shows an example of an optical system using an optical waveguide 8 as an array arrangement. The optical waveguide 8 is provided on a quartz substrate 14, and the optical fiber 3 is coupled at an optical waveguide input end 9. The synchronization signal generating photodetector 11 is for detecting a multi-beam to be scanned.

FIG. 4 shows a circuit for driving a semiconductor laser. The semiconductor laser LD is housed integrally with the built-in photodetector PD and the case 2, and a part 26 of the laser power emitted from the semiconductor laser is detected by the PD. In order for the synchronization signal generation photodetector 11 to generate a light detection signal, it is necessary to irradiate the synchronization signal generation photodetector 11 with multiple beams. In other words, the laser beam always
It is in the N state. Therefore, the output of the semiconductor laser forming a multi-beam at this timing can be detected by the built-in photodetector PD. The signal 21 gives this timing, and samples and holds the output of the built-in photodetector PD. The sampled and held signal is compared with a reference voltage, and the current level of the current source 25 is determined by the differential amplifier Diff so that these signal levels become the same level. The reference voltage input to the differential amplifier is set by adjusting the voltage VR with the variable resistor 23. SW turns on and off the current flowing through the semiconductor laser LD, and is driven by a data signal 22 input via the digital amplifier D.

By the way, the conventional semiconductor laser driving circuit can always keep the optical power of the semiconductor laser constant. However, in the optical system shown in FIGS. The power changes when the environmental temperature of the apparatus changes, causing unevenness in light intensity between the multiple beams, resulting in a problem of deteriorating printing quality. This is because
This is because, even if the optical power of the semiconductor laser is kept constant, the laser power emitted from the array section 4 fluctuates when the environmental temperature changes.

FIG. 5 shows changes in the ambient temperature of the laser power of each of the multi-beams emitted from the array arrangement section 4. However, the optical power emitted from each semiconductor laser 1 is controlled so as to be constant even if the environmental temperature changes. As can be seen from FIG. 5, when the environmental temperature changes, the fluctuations in the optical power of each of the multi-beams emitted from the array unit 4 are different from each other. The printing quality was degraded. The cause of the fluctuation in the optical power emitted from the array unit 4 is the alignment between the laser light incident on the optical fiber 3 and the optical fiber 3 and, in the optical system of FIG. 3, the alignment between the optical fiber 3 and the waveguide 8. The required accuracy was in the submicron range, and it was found that a slight displacement caused by a change in environmental temperature fluctuated the laser power.

[0008]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an optical recording apparatus using an optical fiber which does not cause deterioration of print quality even when the environmental temperature changes.

[0009]

According to the present invention, there is provided a semiconductor laser module for guiding laser light emitted from a semiconductor laser to an optical fiber and a plurality of lasers emitted from the plurality of semiconductor laser modules. An array arrangement unit for arranging light in an array, a multi-beam emitted from the array arrangement unit, and an optical scanning optical system that enables optical recording on a photosensitive material and are input to each of the plurality of semiconductor lasers A semiconductor laser driving circuit that modulates light according to a data signal, optical power detecting means for detecting optical power of each of the plurality of semiconductor lasers, outputting an optical power detection signal, and temperature detecting means for detecting a temperature of the device. The device used has a reference voltage generating circuit for calculating a reference voltage from a temperature signal output from the temperature detecting means, The driving circuit and determines the driving current of the semiconductor laser by comparing the reference voltage and the optical power detection signal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plurality of semiconductor lasers and a laser printer using an optical fiber or an optical waveguide shown in FIGS. FIG. 1 shows a laser driving circuit of the present invention for driving each semiconductor laser in this optical system.

The semiconductor laser LD is housed in the case 2 integrally with the built-in photodetector PD. The semiconductor laser LD emits laser light from both ends of the element, and one light 26
Is used to detect the optical power emitted from the semiconductor laser. The built-in photodetector PD is a light power detecting means for detecting the light 26, and is integrated with the semiconductor laser LD in the case 2
It is built in. In order for the synchronization signal generating photodetector 11 to generate a photodetection signal, it is necessary to irradiate the synchronization signal generating photodetector with multiple beams. That is, the laser beam is always in the ON state at this location. Therefore,
At this timing, the output of the semiconductor laser forming a multi-beam can be detected by the built-in photodetector PD. The signal 21 gives this timing, and samples and holds the output of the built-in photodetector PD. The sampled and held signal is compared with a reference voltage, and a differential amplifier Dif serving as comparison means is set so that these voltage levels become the same level.
The current level of the current source 25 is determined by f. Differential amplifier Di
The reference voltage input to ff is initially adjusted by the variable resistor 23, but the voltage supplied to the variable resistor 23 so that the optical power of the multi-beam does not fluctuate even when the apparatus operates and the environmental temperature fluctuates. The level is automatically changed by the reference voltage generation circuit 31. The reference voltage generating circuit 31 supplies the respective reference voltages to all the semiconductor laser driving circuits constituting the multi-beam through the output line 24.

Next, this principle will be described with reference to FIG. TH is a thermistor or a thermocouple as temperature detecting means, and detects the temperature of the optical system. The temperature detection data is amplified by the amplifier A, digitized by the A / D converter, and input to the control circuit MC. The control circuit MC reads a current to be driven by each semiconductor laser from the data memory M in accordance with the digitized temperature data,
The signal transmitted to the / A converter and output from the D / A converter is used as a reference voltage for each semiconductor laser drive circuit. S
W is for turning on and off the current flowing through the semiconductor laser LD, and is driven by the data signal 22 input via the digital amplifier D.

The temperature detecting means TH is connected to the array
If it is provided in the vicinity of the array arrangement section 4 so that the temperature can be detected, the influence of the environmental temperature change can be reduced.

In the optical system shown in FIG. 3, a temperature detecting means TH may be provided in the vicinity of the array section 4 or the quartz substrate 14 may be provided.
In this case, the temperature at the junction with the array arrangement section 4 can be accurately detected.

[0015]

When the optical system according to the present invention is used, the alignment between the laser beam incident on the optical fiber and the optical fiber and the alignment between the optical fiber and the waveguide are slightly shifted due to a change in environmental temperature. Even if the laser power of each of the multi-beams emitted from the array unit fluctuates, by adopting a control method that has a function to correct the fluctuation characteristics of the environmental temperature and the laser power, the multi-beams can also be adjusted for environmental temperature changes. An optical recording apparatus in which the laser power does not change and the printing quality does not deteriorate can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a multi-beam semiconductor laser drive circuit according to one embodiment of the present invention.

FIG. 2 is a schematic diagram of a laser printer optical system using a multi-beam.

FIG. 3 is a schematic diagram of a laser printer optical system using a multi-beam.

FIG. 4 is a block diagram of a conventional semiconductor laser drive circuit.

FIG. 5 is a graph showing the relationship between the optical power of a semiconductor laser and the ambient temperature.

FIG. 6 is a block diagram of a reference voltage generation circuit used in a multi-beam semiconductor laser drive circuit.

[Explanation of symbols]

1: semiconductor laser module, 2: semiconductor laser unit,
3: optical fiber, 4: array arrangement part, 5: rotating polygon mirror,
6: scanning lens, 7: photosensitive drum, 8: optical waveguide, 9:
Joint between optical fiber and optical waveguide, 10: spot array, 1
1: photodetector for synchronizing signal generation, 15: optical scanning line, L1,
L2, L3: spherical lens, LC1: cylindrical lens, LD:
Semiconductor laser, PD: built-in light detector, 23: variable resistor, 26: laser light incident on PD, VC: supply voltage,
SH: sample hold circuit, Diff: differential amplifier,
D: digital amplifier, SW: switch circuit, TH: temperature detection means, 31: reference voltage generation circuit, 25: current source,
30: semiconductor laser drive circuit, A: amplifier, A / D: A
/ D converter, MC: control circuit, M: data memory.

Claims (2)

[Claims] 1. An optical fiber for guiding a plurality of semiconductor lasers and a laser beam, an array arrangement portion in which laser light emitting portions of the optical fiber are arranged in an array, and scanning for scanning a laser beam to perform optical recording on a photosensitive material. An optical system section having an optical system, a laser drive circuit for optically modulating according to the data signal input to each of the semiconductor lasers, and an optical power detection for detecting the optical power of each of the semiconductor lasers and outputting an optical power detection signal Means, and an optical recording apparatus having a temperature detecting means for detecting a temperature of the optical system unit, a reference voltage generating circuit for calculating a reference voltage from an output signal of the temperature detecting means, and comparing the reference voltage and the optical power detection signal. An optical recording apparatus using a multi-beam, wherein a comparison means for determining a drive current of the semiconductor laser is provided in the laser drive circuit. 2. The optical recording apparatus according to claim 1, wherein a temperature detecting means is provided near the array arrangement part, and detects the temperature of the array arrangement part.