JP2944085B2 - Optical unit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical unit for driving a light emitting element such as a laser in accordance with an image signal to form a latent image on a photoconductor.

(Prior Art) In a laser printer generally used as a printer, an optical scanning system including a semiconductor laser, a polygon mirror, and the like is generally provided 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 or the like, and a polygon mirror deflects the laser beam to form a photoconductor placed outside the optical unit. Expose the drum. The electrostatic latent image formed on the photosensitive drum is printed by electrophotography.

As shown in FIG. 5, the optical unit (printer head) 2 is installed, for example, in the upper part of the laser printer main body 1. FIG. 6 shows an example of a conventional optical unit. Print head case 12 on print head base 11
The substrate 13 for driving the semiconductor laser and the substrate 14 for driving the polygon mirror are mounted. Print head case
12 has two convex portions 12a and 12b. A substrate 15 for mounting a semiconductor laser element is fixed outside the projection 12a. A laser beam emitted from a semiconductor laser element (not shown) is corrected to parallel light by a collimator lens 16 attached to an opening provided in the convex portion 12a, and is further condensed on one deflection surface of a polygon mirror 18 by a cylindrical lens 17. Is done. The laser beam condensed on the deflecting surface is deflected according to the rotation of the polygon mirror 18, passes through the f-θ lens 19 for correcting the optical path, is reflected obliquely downward by the mirror 20, passes through the opening of the optical unit case 12, and passes through the outside. Go out to. On the other hand, deflection (scanning) by the polygon mirror 18
The substrate 22 for generating a synchronization signal for generating a synchronization signal for the start of the optical unit 12 is attached to the projection 12b of the optical unit 12.
At the start of the deflection, the laser beam reflected from the polygon mirror 18 is reflected by the mirror 21 and detected by a photodiode (not shown) on the substrate 22.

(Problems to be Solved by the Invention) In the optical unit of the conventional laser printer,
Generally, the semiconductor laser element, the substrate for the semiconductor laser drive circuit, the synchronization signal detection element, and the substrate for the synchronization signal detection circuit are respectively arranged at the positions where they are most easily arranged in the mechanism configuration. The optical path length from the polygon mirror to the photoconductor is
The optical path length from the polygon mirror to the optical sensor for synchronization detection needs to be almost the same. However, the conventional optical unit is large, and integrating each circuit on one substrate is difficult.
It was impossible optically.

Further, there is one in which one end of an optical fiber is installed at a synchronization signal detection position, the other end is directly guided to a printer control board, and a synchronization signal detection circuit is provided on the control board. Also in this case, each circuit is arranged on another substrate.

However, recent miniaturization of the printing system and improvement of the lens performance have made it possible to make the optical unit compact.

Integrating each circuit with the substrate and attaching it to the optical unit has the advantages of reducing the cost of parts and improving reliability, and also facilitates miniaturization of the optical unit.

It is an object of the present invention to provide a compact optical unit.

(Means for Solving the Problems) An optical unit according to the present invention includes a light emitting element that emits a light beam, a deflector that deflects and scans the light beam emitted from the light emitting element toward a surface to be scanned, An optical unit that directly receives a light beam to be scanned and detects a synchronization signal for synchronization of scanning on the surface to be scanned, and a light emitting element and a synchronization signal detection element are both held. With one substrate, the light beam emitted from the light emitting element is incident on the light receiving surface of the synchronization signal detecting element at a predetermined angle where the optical axis of the light beam is non-parallel to the normal of the light receiving surface, The synchronization signal detecting element is held on the substrate such that the optical axis of the light beam emitted from the light emitting element and the optical axis of the light beam incident on the light receiving surface form a predetermined non-parallel angle.

Preferably, an optical path length from the deflector to the surface to be scanned and an optical path length from the deflector to the light receiving element are optically the same.

(Operation) In the optical unit, the light receiving element and the light emitting element are held and integrated on the same substrate. Thereby, the reliability of the optical unit is further improved, and the optical unit can be made more compact.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a perspective view of an optical unit 100 according to an embodiment of the present invention. In an optical unit case 100, a polygon mirror 102, a cylindrical lens 103, an f-θ lens 10
6, mirrors 108, 109 and 110 (not shown) are arranged.

The optical unit case 101 includes a flat bottom plate 111 and a surrounding wall 112. The upper part of the wall 112 is closed by a flat lid (not shown). The wall 112 includes mounting brackets 113 for mounting the optical unit case 101 to the printer body.

In the optical unit case 101, the polygon mirror 102, the f-θ lens 106, and the mirror 109 are arranged in a row so that the reflected light from the polygon mirror 102 passes through the f-θ lens 106 and is reflected by the mirror 109. The mirror 109 has a rectangular shape and reflects a laser beam deflected in the longitudinal direction in accordance with the rotation of the polygon mirror 102 having a polygonal shape, obliquely downward.
The reflected light goes out through a slit 114 provided in the bottom plate 111 of the optical unit case 101. The wall portion 112 of the optical unit case 101 is provided with 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 109, an optical path of a laser beam including a semiconductor laser element (not shown) 201, a collimator lens 105, a cylindrical lens 103, and a polygon mirror 102 is provided. The laser beam emitted from 201 is condensed and incident on the deflection surface of polygon mirror 102.

For this reason, the wall 112 of the optical unit case 101 is
As shown on the upper right side of the figure, a flat portion 112a is provided, and the substrate 104 is mounted outside the flat portion 112a. 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 synchronization signal are attached to the substrate 104. Therefore, all optoelectronic components 201 and 203 necessary for laser beam exposure are
Installed on 04. In order to form an optical system between the components 201 and 203 on the substrate and the optical components inside the optical unit case 101, the beam emitting side of the semiconductor laser element 201 and the beam incident side of the photodiode 203 are respectively in the plane of the optical unit case 101. Facing the inside of the optical unit case 101 through the holes 115, 116 opened in the portion 112a,
A collimator lens 105 is attached to the opening 115.

For detecting a synchronization signal, a mirror 108 is provided near the scanning start side end of the mirror 109, and further, a mirror 110 (not shown) is used to reflect the reflected light of the mirror 108 to the hole 116.
Is provided in the vicinity of the end of the mirror 109 on the scanning end side.

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 passes through the collimator lens 105 and the cylindrical lens 103, and passes through the first mirror of the polygon mirror 102.
Incident on two surfaces. The beam reflected from this surface is f-
Reflected by the mirror 109 through the θ lens 106, the slit 11
The light exits from the optical unit 100 through 4, enters the photosensitive drum 202, and exposes the photosensitive drum 202. Polygon mirror 1
With the rotation of 02, the emission direction of the beam reflected from one surface of the polygon mirror changes as shown in the figure, and the photosensitive drum 202 is scanned in the axial direction. At the start of scanning to synchronize this axial scanning, the laser beam is
Reflected at 8,110, through aperture 116, photodiode 203
Incident on. When arranging the optical system, the mirrors 108 and 110 and the photodiode 203 are arranged so that the optical path length from the polygon mirror 102 to the photodiode 203 is substantially 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 semiconductor laser element 201. However, due to the recent miniaturization of the printing system (such as the photosensitive drum 202) and the improvement of the lens performance, the semiconductor laser element 201 and the photodiode 203 for detecting the synchronization signal are arranged close to each other on the same substrate while maintaining the same optical path length. It became possible.

FIG. 3 is a diagram of a circuit configured on the substrate 104. This circuit is characterized by including a power supply circuit in addition to a semiconductor laser driving circuit and a synchronizing signal detecting circuit similar to the conventional one. FIG. 4 shows a board on which each circuit component is mounted.
1 shows a perspective view of 104. FIG.

The upper left circuit in FIG. 3 is a power supply circuit for supplying a constant voltage of +5 V to the elements on the substrate. Connector from outside (4th
A voltage of, for example, +12 V is supplied via a 400, and the voltage is supplied to a constant voltage power supply element (for example, a three-terminal regulator (78
05) (voltage specification 5 ± 0.2V) Stabilized at 301. DC-D
A constant voltage power supply element such as a converter may be used. Terminal A to which + 5V voltage is supplied by constant voltage power supply element 301
Is connected to each terminal A 'in the figure, and the GND terminal B is connected to each terminal B' in the figure, respectively.
These connecting lines have been omitted to avoid complicating the drawing.

Since a constant voltage power supply circuit is provided on the substrate 104, the power supply line (+12
Even if an inadvertent surge enters the substrate 104 from V), it is cut off by the constant voltage element 301. Therefore, the semiconductor laser element 201 does not deteriorate. Also, the laser light output is kept constant.

Also, in printer manufacturing, the optical unit 100
If power is supplied to the substrate 104 from an external jig power supply alone and the laser light output is adjusted to a predetermined value, the optical unit 10
Even if 0 is mounted on the printer body (not shown) and the power is supplied from the printer side, the supply voltage does not fluctuate by the constant voltage element 301, so that the adjusted light output is maintained at a predetermined value.

Furthermore, in the market, if it becomes necessary to replace the optical unit 100 due to some factor (such as a failure), it is sufficient to simply replace the optical unit 100 with the one that has already been adjusted and shipped alone. The trouble of making adjustments can be saved.

In FIG. 3, the central part is a semiconductor laser element 201,
It is composed of a light amount adjustment volume 320 and a laser drive IC 300, and constitutes a laser drive and laser light amount control circuit similar to the conventional one. The semiconductor laser element 201 includes a semiconductor laser chip 310 for emitting a laser beam to the outside.
In addition, a photodiode 311 for detecting the light amount of the sub laser beam generated by the semiconductor laser chip 310 is provided. Since the relationship between the output of the semiconductor laser element 201 and the current greatly depends on the temperature, by arranging the photodiode 311 inside, the output drop due to self-heating is corrected and the output is stabilized.

The laser output is controlled by two transistors 306,307. 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 the transistors 306 and 307 are connected to the power supply terminal A 'via resistors. Transistor 30
Reference numeral 7 allows a constant current to flow when the image signal d is at a high level. On the other hand, a current always flows through the other transistor 306 regardless of the presence or absence of the image signal d. If the current flowing through the semiconductor laser chip 306 is switched from 0 only by the transistor 307, the response of the optical output is deteriorated due to the transient characteristics of the optical output. Note that when only the transistor 306 flows a current, the light emitting state is set to a low-level light emitting state that is insufficient for drawing an image on the photoconductor 202.

Further, control for keeping the laser light output constant is performed by increasing or decreasing the current flowing through the transistor 306 in accordance with the amount of light received by the photodiode 311. Photodiode 311
Is connected to a power supply terminal A ′ via a light amount adjusting volume 320 and to a + input terminal of the operational amplifier 302. On the other hand, the other terminal is GND terminal B '
Connected to. After the detection signal of the photodiode 311 is amplified by the operational amplifier 302,
03, is applied to the base of the transistor 306 via a sample and hold circuit including a CR circuit 304 and an operational amplifier 305.
Therefore, when the analog switch 303 is closed, the current flowing through the transistor 306 is controlled so that the laser light output becomes constant. Note that the reference of the current amount is adjusted by a light amount adjustment volume 320 connected in series to the photodiode 311. In addition, the analog switch 303 closes the optical output by the sample hold signal outside the image recording area to make the optical output constant, and opens inside the image recording area to make the current constant,
An image is recorded in the image recording area, but the light output is kept constant because the sampling period is short.

3, the detection signal of the photodiode 203 is input to the comparator 330, and the output voltage of the comparator 330 is output to the printer control system as a synchronization signal.

The power supply circuit including the constant voltage power supply element does not necessarily need to be substantially integrated with the semiconductor laser drive circuit and incorporated on the same substrate 104, but by incorporating it on the same substrate, the size and cost can be reduced. Further, by providing the optical unit case 101 with the flat portion 112a and substantially integrating the substrate 104 with the optical unit case 101,
Useful for downsizing optical units.

(Effect of the Invention) Since each circuit is integrated with the substrate, the cost can be reduced and the reliability is improved. Further, the optical unit can be downsized by substantially integrating the substrate with the optical unit case including the optical components.

[Brief description of the drawings]

 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 a circuit configured on a substrate. FIG. 4 is a perspective view of the substrate. FIG. 5 is a perspective view of a conventional printer. FIG. 6 is a perspective view of a conventional optical unit. 100 optical unit, 101 optical unit case, 102 polygon mirror, 104 substrate, 112a flat surface, 115, 116 opening, 203 synchronous signal detection element, 201 semiconductor laser element ( Light-emitting element).

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tatsuya Eguchi 2-30 Azuchicho, Higashi-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Camera Co., Ltd. (72) Katsuya Oda 2--30 Azuchicho, Higashi-ku, Osaka, Osaka Address Osaka International Building Minolta Camera Co., Ltd. (56) References JP-A-62-38657 (JP, A) JP-A-60-172014 (JP, A) JP-A-62-215227 (JP, A) JP-A Sho-62 JP-A-61-255314 (JP, A) JP-A-59-123826 (JP, U)

Claims (2)

(57) [Claims] A light emitting element for emitting a light beam; a deflector for deflecting and scanning the light beam emitted from the light emitting element toward a surface to be scanned; An optical unit having a synchronous signal detecting element for detecting a synchronous signal for synchronizing scanning on a surface, comprising: a single substrate holding both the light emitting element and the synchronous signal detecting element; A light beam incident on the light-receiving surface of the synchronization signal detecting element at a predetermined angle where the optical axis of the light beam is non-parallel to the normal to the light-receiving surface, and the optical axis of the light beam emitted from the light-emitting element. An optical unit, wherein a synchronization signal detecting element is held on a substrate such that an optical axis of a light beam incident on the light receiving surface forms a predetermined non-parallel angle. 2. An optical path length from the deflector to a surface to be scanned,
The optical unit according to claim 1, wherein an optical path length from the deflector to the light receiving element is optically the same.