JPH01281962A - Led element drive circuit for optical unit - Google Patents

Abstract

PURPOSE:To enable an optical unit to adjust a light output independently by providing a constant voltage power supply section which supplies a constant voltage to a drive circuit connected to an external power supply, in a light-emitting element drive circuit of a laser printer. CONSTITUTION:A substrate 104 which becomes a drive circuit for an optical system such as a polygon mirror and a semi-conductor laser element 201 are assembled in an enclosure of an optical unit. On this substrate 104, a constant voltage power supply element 301 is mounted, and for instance, a 12V voltage is supplied from the outside through a connector 400 to supply a +5V constant voltage to each element such as a semi-conductor laser element 201 on the substrate from a terminal A and a GND terminal B. The semi-conductor laser element 201 consists of a semi-conductor laser chip 310 and a photodiode 311 which detects the amount of light energy of the auxiliary laser beam from the semi-conductor laser chip 310 and generates heat itself to stabilize its output. The semi-conductor laser element 201 is driven by a laser drive IC 300 and is subjected to the adjustment of the amount of light energy by a volume 320. Thus the light output need not be readusted when a light-emitting element drive circuit is incorporated in a printer, after the light output is is adjusted by the optical unit alone.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an optical unit for forming a latent image on a photoreceptor by driving a light emitting element such as a laser according to an image signal;
More specifically, the present invention relates to a light emitting element drive circuit incorporated into an optical unit.

(Prior Art) In a laser printer that is commonly used as a printer, an optical scanning system including a semiconductor laser, a polygon mirror, etc. is usually installed as a unit. In this type of optical unit, a semiconductor laser element emits a laser beam in response to an image signal from an external image reader, etc., and a polygon mirror deflects the laser beam to a photoreceptor installed outside the optical unit. Expose the drum. The electrostatic latent image formed on the photosensitive drum 2 is printed by electrophotography.

As shown in FIG. 5, an optical unit (installed at the top of the print head I) is installed at the top of the print head I. FIG. 6 shows an example of a conventional optical unit. 12 and semiconductor laser drive circuit blocking plate 1
3 and the substrate 14 for driving the polygon mirror are removed.The print head case 12 has two protrusions 12a
, 12b.

A substrate 15 for mounting a semiconductor laser element is fixed to the outside of the convex portion 12a. A laser beam emitted from a semiconductor laser element (not shown) is corrected into parallel light by a collimating lens 16 attached to an aperture provided in the convex portion 12a, and is further corrected into parallel light by a nolindrical lens I7 on one deflection surface of a polygon mirror 18. The light is focused on. The laser beam focused on the deflection surface is deflected according to the rotation of the polygon mirror 18, and is then deflected by the f-0 lens 19 for optical path correction.
The light is reflected diagonally downward by the mirror 20, and exits through the opening of the optical unit case 12 to the outside. On the other hand, a synchronization signal generation substrate 22 for generating a synchronization signal for the start of deflection (scanning) by the polygon mirror 18 is attached to the protrusion +2b of the optical unit 2. , a laser beam reflected from the polygon mirror 18 (reflected by the J1 mirror 21 and detected by a photodiode (not shown) on the substrate 22).

The optical unit also includes a linear L E as a light emitting element.
Some use D array elements. In this case no optical beam deflection is required. An image is written on a photoreceptor by causing an element (pixel) corresponding to an image signal to emit light.

(Problems to be Solved by the Invention) Power for the semiconductor laser drive circuit to the optical unit 1 is supplied from the power source of an external Ronok circuit.

By the way, semiconductor laser devices are extremely weak in terms of static electricity and Zahn current due to their characteristics, and if a current exceeding a predetermined current value flows even momentarily, the device will deteriorate or even be destroyed. A filter made of C or the like is inserted into the power supply line of the drive circuit to prevent Zahn from entering from the power supply line.

By the way, the adjustment to set the laser light output to a predetermined value (") is performed by supplying power from an external jig power supply to the optical unit assembled independently in the production of laser links. Next, adjustment is performed. The power supply voltage of the printer body has an error within a range of ±5%, and the power supply voltage of the printer body may vary depending on the optical output. The voltage of the power source for the adjustment jig is not necessarily completely equal to the voltage, and furthermore, due to the voltage drop due to the electric wire from the power source, the optical output of the semiconductor laser when the optical unit is installed in the printer body may be lower during adjustment. For example, even if the voltage of the power supply for the jig is exactly 5.OV, the power supply voltage of the printer body with the optical unit installed may be different. If the value is 48 cm due to the double error, the optical output of the semiconductor laser will be lower than the set value and readjustment will be required.

Furthermore, when the optical unit is replaced due to a failure of the optical unit, readjustment is similarly required.

In the case of an optical unit using a linear L E I) array element, there is no effect of surges in the power supply, but there is a problem in that fluctuations in the power supply voltage C' cause variations in the amount of light (therefore, the diameter and diameter).

SUMMARY OF THE INVENTION (J) An object of the present invention is to provide a light emitting element drive circuit for an optical unit that does not require adjustment of light output when incorporated into a printer body.

(Means for Solving the Problems) A light emitting element driving circuit for an optical unit according to the present invention is an optical unit for a printer which is formed by unitizing a scanning system that scans output Q and J beams from a light emitting element on a photoreceptor. A drive circuit for a light emitting element mounted on a unit, the drive circuit including:
It is characterized in that it is provided with a constant voltage power supply unit that is connected to an external power supply and supplies a constant voltage to the drive circuit.

(Function) In the optical unit for the printer, a constant voltage circuit section is installed in the light emitting element drive circuit. Therefore, the power supply voltage supplied to the drive circuit remains constant even if different external power supplies are used, such as the jig power supply or the printer main power supply.Therefore, the light output of the light emitting element is also maintained at a predetermined value. I'll come.

(Example) Hereinafter, the present invention will be described in detail with reference to the attached drawings.

FIG. 1 is a perspective view of an optical unit +00 according to an embodiment of the present invention. Inside the optical unit case 101, there are a polygon mirror 102, an optical lens +03, an f4 lens 106, mirrors 108 and 109, and I]0.
(not shown) is arranged.

The optical unit case +01 consists of a planar bottom plate part 111 and a surrounding wall part 112. The upper part of the wall part 112 is sealed by a planar lid part (not shown). The wall portion 112 is used to attach the optical unit case 101 to the printer body (-1').
Bracket part for 1.3, 113.
Equipped with.

Inside the optical unit case +01, there is a polygon mirror 10.
The reflected light from 2 passes through r-O lens +06 to mirror 1.
Polygon mirror 102, f-0 so that it is reflected at 09
The lens 106 and the mefy-109 are arranged in a row. The mirror 109 has a rectangular shape, and deflects the laser beam, which is deflected in the elongated direction as the polygonal mirror 102 rotates, obliquely downward. This reflected light is transmitted through a slit 11 provided in the bottom plate portion I11 of the optical unit case 101.
4 and exit to the outside. Optical unit case 10
The wall portion 112 of 1 includes these optical components 102, 106,
It has a shape that can accommodate 109.

Further, on the side of the optical path from the polygon mirror 102 to the mirror 1°9, a semiconductor laser element (not shown) 201,
Collimator lens 105, Norindrical lens +03
, a laser beam optical path consisting of polygon mirrors Io2 is provided, and the laser beam emitted from the semiconductor laser element 201 is focused onto the deflection surface of the polygon mirror 102 and is incident thereon.

Therefore, the wall portion II2 of the optical unit case +01 is
As shown in the upper right side of FIG. 1, it includes a flat part 112a,
A board +04 is placed on the outside. As will be described later, a semiconductor laser element (not shown) 201 for emitting light and a photodiode (light receiving element) 203 for detecting a synchronizing signal are attached to this substrate 104.

Therefore, all optoelectronic components 201, 203 necessary for laser beam exposure are mounted on the same substrate 104. Since an optical system is formed between the components 201, 203 of the substrate 1- and the optical components inside the optical unit case 1.01, the beam exit side of the semiconductor laser element 201 and the beam incidence side of the photodiode F' 203 are 7= are respectively the flat part 11 of the optical unit case 101
The opening +15 is located inside the optical unit case 101 through the holes 115 and 116 opened at the opening +15.
The collimator lens 105 is attached 1:I.

In order to detect the synchronization signal, a mirror 108 is installed near the end of the mirror +09 on the scanning start side i-1.
10 (not shown) is provided near the end of the scanning end of the mirror 109.

FIG. 2 shows the operation of the optical system in the optical unit 100. The laser beam emitted from the semiconductor laser element 201 in response to the drive signal is transmitted through the collimator lens 105.
The light passes through the irradiating lens 103 and enters one surface of the polycon mirror 102 . The beam reflected by this surface passes through the f-0 lens 106, is reflected by the mirror 109, exits the optical unit 100 from the slit 14, enters the photoreceptor drum 202, and enters the photoreceptor drum 202.
Expose 02. As the polygon mirror 102 rotates = 8, the direction of the beam reflected from one surface of the polygon mirror changes as shown in the figure, and the beam is directed toward the photoreceptor 1.2.
02 in the axial direction. The same jυ of this axial scan
At the start of scanning to capture I, the laser beam is reflected by the mirrors 108 and 110, passes through the aperture 1116, and enters the photodiode 203.The arrangement of the optical system? Kara Hototaio 1
- The mirror 108° 110 and the photodiode 1s' 203 are arranged so that the optical path length up to 203 is approximately equal to the optical path length from the polygon mirror 102 to the photosensitive drum 202. Conventionally, it has been impossible to arrange a synchronization signal detection element near the T, J, and semiconductor laser elements 201. However, in recent years, with the miniaturization of printing systems (such as the photoconductor tram 202) and improvements in lens performance, it has become possible to keep both optical path lengths equal (S) while placing the semiconductor laser element 201 and the photodiode 1' 203 for synchronization signal detection in close proximity. This made it possible to arrange them on the same substrate.

FIG. 3 ('') is a diagram of the circuit configured on board +04.

This circuit is characterized by comprising a semiconductor laser driving circuit and a synchronization signal detection circuit similar to the conventional circuit, and also includes a power supply circuit. In addition, in Fig. 4, each circuit component is taken (t j
A perspective view of a three-dimensional substrate 104 is shown.

The circuit on the upper left side of FIG. 3 is a power supply circuit that supplies a constant voltage of +5cm to the elements on the substrate. Connector (4th
For example, a voltage of +12V is supplied through the voltage (see figure) 400, and is stabilized by the voltage (J constant voltage power supply element (for example, 3-terminal regulator (7805) (voltage specification 5 ± 0, 2V) 301.D C-DC A constant voltage power supply element such as a converter may be used.The constant voltage power supply element 301
The terminal Δ to which a voltage of 5V is supplied is connected to each terminal A' in the figure.
Furthermore, the GND terminal B is connected to each terminal B° in the figure, but these connecting lines are omitted in FIG. 3 to avoid complicating the drawing.

Since a constant voltage power supply circuit is installed on the board 1041m, even if an accidental surge enters the board I04 from the power line (-12V), there is no need to remove the LC filter like in the past. It is cut off by the constant voltage element 301. subordinate
;F 1-body laser element 201 or deteriorated 4-rokoto (
3.Also, keep the laser light output constant.

Also, in printer manufacturing, optical unino 1-10
By supplying power from an external jig power source to the substrate 107I with 0 alone and adjusting the optical output of the laser to a predetermined value -4', the Optical Unisol I-100 is mounted on the printer body (not shown), Even if power is supplied from the printer side, the supplied voltage does not fluctuate due to the constant voltage element 301).
The amount is maintained at a predetermined value.

Furthermore, even in the market, if it becomes necessary to replace the Optical Unisol l-100 due to some reason (such as a malfunction), even though the Optical Unit +00 has already been adjusted and shipped as a single unit, there is no need to replace it/l+: This improves the performance and saves you the trouble of readjusting the field.

In FIG. 3, the central part (J semiconductor laser element 201
, light amount adjustment volume 320 and laser drive IC 3
00, and constitutes a laser drive circuit and a laser light amount control circuit similar to the conventional one. The semiconductor laser element 201 includes a semiconductor laser chip 310 that emits a laser beam to the outside, and a photodiode 311 that detects the amount of a sub laser beam generated by the semiconductor laser beam 310. Since the relationship between the output and current of the semiconductor laser element 201 is significantly dependent on temperature, by arranging the phototire auto 311 inside, the output decrease due to self-heating is corrected and the output is stabilized.

The laser output is controlled by two transistors 306 and 307. The cathode terminal of the semiconductor laser chip 310 is connected to the GND terminal B', and the other terminal is connected to the collector terminals of the transistors 306 and 307. On the other hand, the plate terminals of both transnostars 306 and 307 are respectively connected to the power supply terminal A' via a resistor.

The transnostar 307 allows a constant current to flow when the image signal d is at a high level. On the other hand, current is always passed through the other transnostar 306 regardless of the presence or absence of the image signal d. Since the current flowing through the semiconductor laser chip 306 was switched from O using only the transistor 307 (J
This is because the responsiveness of the optical output deteriorates due to the transient characteristics of the optical output. It should be noted that the setting is such that when the current is applied to the tranostar 306 (J), the light is emitted at a low level that is insufficient to draw an image on the photoreceptor 202.

Furthermore, the control to keep the laser light output constant is to control the current flowing through the lannostar 306 to the photodiode 1;' 31
] by increasing or decreasing the amount of light received. The cathode terminal of the photodiode 311 is connected to the power supply terminal Δ′ via the polycomb 320 for adjusting the amount of light, and
It is connected to the ten input terminal of the operational amplifier 302. Meanwhile, the other terminal should be connected to GNI) terminal +3'. Then, the detection signal of the photo tie auto 1 is amplified by an operational amplifier 302, and then applied to the head of the toranonostar 306 through a hold circuit consisting of an analyte circuit 303, a crimp circuit 304, and an operational amplifier 305.

Therefore, when the analog switch 303 is closed, the current flowing through the trannostar 306 is controlled so that the laser light output is constant. Note that the current amount is adjusted by the light amount adjusting polycomb 320 connected in series to the standard (J, potdiode 1' 311) of the current amount.Also, the analogue isoji 303 is closed by the sample halt signal outside the image recording area to keep the light output constant and record the image. It opens in the recording area to keep the current constant and records an image in the image recording area, but since the sample period is short, the light output is kept constant.

In the synchronization signal detection circuit shown on the lower right side of FIG. 3, the detection signal of photodiode 1' 203 is input to comparator 3'30, and the output voltage of comparator 330 is output as a synchronization signal to the printer control system. .

The power supply circuit including the constant voltage power supply element does not necessarily have to be substantially integrated with the semiconductor laser drive circuit and incorporated into the same substrate 104, but by incorporating it into the same substrate, it can be made smaller and lower in cost. Further, by installing the flat portion 112a in the optical unit case 101 and substantially integrating the substrate 104 into the optical unit case 101, it is possible to reduce the size of the optical unit.

(Effects of the Invention) The light emitting element drive circuit for an optical unit according to the present invention has a constant voltage circuit section, and when incorporated into the printer body after performing optical output adjustment independently. There is no need for readjustment. Furthermore, even in the event of a failure, the optical unit can be simply replaced, reducing the burden on service.

[Brief explanation of the drawing]

FIG. 1('' is a perspective view of the optical unit. FIG. 2 is a perspective view of the optical system. FIG. 3' is a diagram of the circuit configured on the board. FIG. 4 is a perspective view of the optical unit. FIG. 5 is a perspective view of a conventional printer. FIG. 6 is a perspective view of a conventional optical unit. +00 Optical unit, 101-Optical unit case, 102 Polygon mirror, 104 ・Nail plate, 11
2a Plane part, 115, 116 Opening, 203
Synchronous signal detection element, =15-201 semiconductor laser element, 202 photosensitive drum, 3013 terminal power supply element.

Claims (1)

[Claims] (1) A drive circuit for a light-emitting element mounted on an optical unit for a printer, which is formed by unitizing a scanning system that scans an emitted beam from a light-emitting element on a photoreceptor, and the drive circuit is connected to an external power source. 1. A light emitting element drive circuit for a printer, characterized in that a constant voltage power supply unit is connected to the drive circuit and supplies a constant voltage to the drive circuit.