JPH07110450A - Optical scanner - Google Patents

Abstract

PURPOSE:To make an optical scanner utilizing a semiconductor laser provided with plural light emitting sources compact and light in weight more while a function detecting the light output of every laser beam is secured. CONSTITUTION:A beam shaping means 4 is formed of a prism 3 enlarging or reducing the diameter of the respective laser beams at least in one direction out of a main scanning direction and a sub-scanning direction, a half mirror 9 formed on the light emitting surface of the prism 3 and a condensing means 10 which is integrated with the prism 3 and which exerts a condensing action with respect to light reflected on the mirror 9 and emits the reflected light. Besides, plural photodetectors individually detecting the reflected light which is separated and emitted by the condensing means 10 and which corresponds to the respective laser beams are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device using a semiconductor laser having a plurality of light emitting sources used in an optical writing scanning system such as a laser printer and a digital copying machine.

[0002]

2. Description of the Related Art In recent years, laser technology has been actively used in various fields. One of them is to use a laser light source such as a semiconductor laser for optical writing for image recording. There is. Since the output of such a semiconductor laser has a temperature characteristic, the output (back beam) from the semiconductor laser is received and detected by a light receiving element such as a photodiode, and a feedback control system is used to detect the order of the semiconductor laser. The directional current is controlled so that the semiconductor laser output becomes stable regardless of temperature changes.

By the way, it has been conventionally known that by using a semiconductor laser having a plurality of light emission sources, parallel and simultaneous recording can be performed for a plurality of dots, and the speed of recording scanning can be increased. In the case of such a semiconductor laser having a plurality of light emission sources, the output of each laser beam fluctuates with a change in temperature, so feedback control is necessary.

Therefore, in the prior art, each light emitting source is
Each channel is time-divisionally driven, and its back beam is received by a single light receiving element to be used for output control.

However, there is a problem that the output variation is induced by the heat interference from the adjacent light source with respect to the light source whose output is not controlled, self-heating, etc., and in order to perform stable output control, each light source must be controlled. It can be said that it is desirable to perform output control at the same time. That is, it is considered necessary to individually perform monitor detection with a plurality of light receiving elements so that output control can be performed in real time.

From the above, Japanese Patent Laid-Open No. 60-263
According to Japanese Patent Laid-Open No. 349, there is proposed one in which a back beam of a semiconductor laser is made incident on a microlens to be separated and can be individually detected by a plurality of light receiving elements. Further, according to Japanese Patent Application Laid-Open No. 2-32542, a plurality of back beams and front beams emitted from a semiconductor laser are collectively detected and calculated to detect the light output of each light emitting source. What has been done is proposed. According to Japanese Patent Application No. 5-11602 proposed by the present applicant, a laser beam emitted forward from a semiconductor laser is divided into two by a half mirror or the like, and one of the laser beams is divided into each beam through a lens. It is shown that the light output is detected by separating and forming an image on the corresponding light receiving element.

[0007]

However, due to the structure of the light beam diffused and emitted from the semiconductor laser, the divergence angle of the light beam greatly differs between the polarization direction of the light beam and the direction orthogonal thereto. . Further, considering that the arrangement direction of the plurality of light emitting sources is generally a direction orthogonal to the polarization direction, the spot diameters of the light beams can be well balanced in the main scanning direction and the sub scanning direction. It is necessary to block or reduce the beam diameter in the direction where the divergence angle of the light beam is large, or to enlarge and shape the beam diameter in the direction where the divergence angle of the light beam is small.

According to the conventional light output control method, the compactness and the cost performance (the number of parts and the working efficiency) are excellent while considering the characteristics of the semiconductor laser having such a plurality of light emitting sources. No, there is still room for improvement.

[0009]

According to a first aspect of the present invention, a laser beam emitted from a semiconductor laser having a plurality of light emission sources is collimated by a collimator lens,
In the optical scanning device, the laser beam deflected by the deflecting means is guided through the beam shaping means, and the laser beam deflected by the deflecting means is imaged on the surface to be scanned by the image forming means for optical scanning. Means, the prism for enlarging or reducing the beam diameter of each laser beam in at least one of the main scanning direction and the sub-scanning direction, a half mirror formed on the exit optical path of this prism, and the prism are integrated. A plurality of light beams that are formed by a condensing unit that emits light reflected by the half mirror with a condensing action and that individually detect the reflected lights corresponding to the respective laser beams that are separated and emitted by the condensing unit. A light receiving element was provided.

In this case, in the invention described in claim 2, the beam shaping means and the plurality of light receiving elements are positioned and fixed on the same support, and in the invention described in claim 3, the semiconductor laser, the beam shaping means, and the plurality of light receiving elements. The light receiving element and the same support were positioned and fixed on the same support.

Further, according to the invention described in claim 4, a detection signal circuit for generating a detection signal according to the amount of light detected by the light receiving element and a drive current for each light emitting source of the semiconductor laser are controlled based on the detection signal circuit. A plurality of light receiving elements were connected and fixed on a circuit board integrally formed with at least a part of the output control circuit.

According to the fifth aspect of the invention, the condensing means is a lens formed by providing a prism with a refractive index distribution.

[0013]

According to the present invention, each laser beam emitted from the semiconductor laser is beam-shaped through the collimator lens, the prism forming the beam shaping means and the half mirror formed on the emission surface thereof, and then deflected. An image is formed on the surface to be scanned through the means and the image forming means. On the other hand, a part of each laser light incident on the prism is reflected by the half mirror and then emitted in a state of being separated corresponding to each laser light by the condensing function of the condensing means, and each individual light receiving element detects the light reception. And is used for controlling the light output of each light emitting source. Therefore, since the half mirror and the condensing means are integrated with the prism mainly composed of the beam shaping means to ensure the dividing and separating function for each laser light, it is necessary for detecting the optical output for each laser light. The number of parts is reduced, work efficiency such as assembly is improved, and downsizing is secured.

According to the second aspect of the invention, since the beam shaping means having such a dividing and separating function is positioned and fixed together with a plurality of light receiving elements on the same support, detection for light output is performed. The relative positional relationship of the optical system can be maintained over time, and stable light output control that is strong against environmental changes and the like can be performed. further,
According to the third aspect of the invention, since the semiconductor lasers are also positioned and fixed on the same support, the assembling workability is good, and the mutual positional relationship can be maintained over time, and the maintainability is also improved. To do.

According to the fourth aspect of the present invention, since the circuit board on which the light receiving element is mounted is integrally formed with a part of the output control circuit and the like, it is resistant to noise and highly accurate output control is possible. Becomes

In the fifth aspect of the present invention, since the condensing means is a lens formed by providing a refractive index distribution in the prism, the beam shaping means can be formed as a flat plate and small in size, and is easy to handle. Is improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. First, an outline of the optical scanning device of this embodiment applied to a laser printer will be described with reference to FIG. There is provided a semiconductor laser 1 having a plurality of light emitting sources each of which emits laser light optically modulated based on an image signal. Next, a collimator lens 2 for converting each laser beam diffused and radiated from the semiconductor laser 1 into a parallel light flux is provided. A prism 3 is provided on the optical path of the parallelized laser light.
The beam shaping means 4 mainly including is provided. The prism 3 is designed to enlarge and shape the beam diameter only in the main scanning direction. A cylinder lens 5 that exerts a predetermined refracting power on these laser beams only in the sub-scanning direction is provided on the optical path emitted from the beam shaping means 4, and enters one surface of a polygon mirror 6 as a deflecting means. Is set. The polygon mirror 6 is rotationally driven at a high speed and deflects and scans each incident laser beam in the main scanning direction. An fθ lens 7 serving as an image forming means is provided on the deflecting exit side of the polygon mirror 6, and an optical path is set so that the deflected scanning light is imaged on the surface of the photoconductor 8 serving as the surface to be scanned.

Here, in the semiconductor laser 1 of this embodiment, it is assumed that the arrangement direction of the plurality of light emitting sources is set to be slightly inclined with respect to the main scanning direction. Therefore, since the divergence angle of the laser light emitted from the semiconductor laser 1 is narrow in the main scanning direction, the prism 3 is configured to expand and shape the beam diameter only in the main scanning direction as described above.

However, the present embodiment is characterized by the configuration in the vicinity of the beam shaping means 4, which will be described with reference to FIG. First, the prism 3, which is the main body of the beam shaping means 4, has an incident surface 3a formed obliquely so that the beam expanding function acts on each laser beam in the main scanning direction.
Further, it has an emission surface 3b which is orthogonal to the optical axis and is emitted as the original writing laser beam toward the cylinder lens 5 and the like, and the half mirror 9 is arranged on the optical axis between the incident surface 3a and the emission surface 3b. The half mirror 9 is formed so as to be inclined with respect to the half mirror 9 so that a part of the laser light can be reflected by the half mirror 9. That is, the half mirror 9 ensures the function of splitting each laser light into the original scanning light and the reflected light for detection.

The end surface 3c of the prism 3 that receives the light reflected by the half mirror 9 (the surface facing the surfaces 3a and 3b)
A concave mirror 10 serving as a light converging means is integrally formed in the. That is, the end surface 3c is formed into a cylindrical shape and a metal coating is formed on the outer surface thereof to form the concave mirror 10 when viewed from the inside. Therefore,
Each reflected light reflected from the half mirror 9 toward the concave mirror 10 is reflected by the concave mirror 10 so as to be condensed and is emitted from the incident surface 3a of the prism 3 to the outside. It will be separated and condensed for each laser beam. That is, the concave mirror 10 ensures the function of separating each laser beam for detection.

A photodetector 11 having light receiving elements (not shown) arranged in an array is provided at a position for individually receiving and detecting each of the laser beams separated and condensed as described above.

Here, the beam shaping means 4 having the function of splitting / separating the laser light by the half mirror 9 and the concave mirror 10 has an optical base (contains and supports a polygon mirror 6, an fθ lens 7 and the like). It is fixed on the (support) 12 by adhesion or the like. Further, the photodetector 11 having a plurality of light receiving elements also has a circuit board 13 integrally formed with a detection signal circuit for generating a detection signal according to the detected light amount.
After being connected and fixed to the above, it is screwed and fixed to the optical base 12. The optical base 12 is integrated with a semiconductor laser 1, a collimator lens 2, and a circuit board 14 and the like in which an output control circuit for controlling the light output of each light emitting source of the semiconductor laser 1 is integrally formed based on a detection signal. The light source unit is also screwed. The circuit board 13,
14 are electrically connected.

Therefore, according to this embodiment, since the half mirror 9 and the concave mirror 10 are integrated with the prism 3 which is the main body of the beam shaping means 4, the laser beam splitting / separating function is also provided. The number of parts required for individual detection for each light can be reduced, the size can be reduced, and the work efficiency of assembly and the like can be improved. In particular, as compared with the case where each of the laser beam division / separation functional members is provided independently, the positional deviation between them is minimized, and stable control is possible. In particular, when considering the concave mirror 10 forming the light condensing means, the labor is saved and the work efficiency is improved as compared with the case where the light condensing lens is independently provided and the cores are aligned and attached to the prism. Further, the beam shaping means 4 and the photodetector 11 constitute a detection optical system, but since they are positioned and fixed on the same optical base 12, their relative positional relationship is maintained over time. It will be possible,
Stable output control can be maintained. Further, in consideration of the signal relationship, since the detection signal circuit is integrally formed on the circuit board 13 for the photodetector 11, the detection signal obtained as an analog signal drives the semiconductor laser 1 in this detection signal circuit. Since it is transmitted to the output control circuit on the side of the circuit board 14 after being converted into a level signal which is a digital signal for controlling the amount of current, it is resistant to noise and highly accurate output control is possible.

Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those shown in the above-mentioned embodiments are designated by the same reference numerals (the same applies to the following embodiments).
Although the beam shaping means 4 in the above-described embodiment enlarges and shapes the beam diameter of the laser light in the main scanning direction, in the present embodiment, the beam diameter of each laser light emitted from the semiconductor laser 1 side is changed in the sub-scanning direction. The beam shaping means 16 mainly including the prism 15 for reduction and shaping is provided. That is, the prism 15 has an entrance surface 15a orthogonal to the optical axis and an exit surface 15b having an inclination with respect to the optical axis so that the beam diameter of the laser light emitted in the sub-scanning direction is reduced. A half mirror 17 is formed between the entrance surface 15a and the exit surface 15b so as to be inclined with respect to the optical axis, and a part of the laser light can be reflected by the half mirror 17. That is, the half mirror 17 ensures the function of dividing each laser light into the original scanning light and the reflected light for detection.

On the end face 15c of the prism 15 which receives the light reflected by the half mirror 17, a grating lens 18 which serves as a light collecting means is integrally formed. Therefore,
Each reflected light reflected from the half mirror 17 toward the grating lens 18 is
It will be emitted to the outside so that it will be condensed by
In this process, each laser beam is separated and focused on the photodetector 11 having each light receiving element. That is, the grating lens 18 ensures the function of separating each laser beam for detection.

Also in the case of this embodiment, basically the same effect as that of the above embodiment can be obtained.

Further, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, first, the collimator lens 2
Instead of the above, a microlens 19 is provided as a collimator lens, is arranged in the package 20 for the semiconductor laser 1, and is configured to make a parallel light flux and emit it.
The package 20 is provided so as to be housed and supported in a recess in a support body 21, and the semiconductor laser 1 thereof is connected and fixed onto a circuit board 22 including a drive circuit and the like.
Further, a beam shaping means 24 mainly composed of a prism 23 on which a parallel light flux from the microlens 19 is incident is provided on the support 21 by being fixed thereto by adhesion or the like. The prism 23 has an incident surface 23a formed obliquely so that a beam expanding function acts on each laser light in the main scanning direction, and the original laser light for writing is directed toward the cylinder lens 5 or the like. Has a light emitting surface 23b orthogonal to the optical axis, and a half mirror 25 is formed between the light incident surface 23a and the light emitting surface 23b so as to be inclined with respect to the optical axis. Mirror 2
It is configured to be able to reflect at 5. That is, the half mirror 25 ensures the function of dividing each laser light into the original scanning light and the reflected light for detection.

A lens 26 is formed inside the end face 23c of the prism 23 that receives the light reflected by the half mirror 25 as a light condensing means. That is, the lens 26 is formed by providing a refractive index distribution from the partial surface of the end face 23c to the inside of the prism 23, and a metal coating or the like is applied to the surface of the end face 23c to form a reflecting surface 27. Therefore, each reflected light reflected from the half mirror 25 toward the lens 26 is reflected by the lens 26 and the reflecting surface 27 so as to be condensed, and further, the end surface 2 of the prism 23.
The light is reflected by 3d and emitted from the other part of the end face 23c orthogonal to the optical axis to the outside, but in this process, each laser beam is separated and condensed. That is, the lens 26 ensures the function of separating each laser beam for detection.

A photodetector 11 in which light receiving elements are arranged in an array is provided at a position for individually receiving and detecting each of the laser beams separated and condensed in this way. More specifically,
An opening and a recess are formed in the support 21 in correspondence with the emission position of the detection light from the end face 23e, and the photodetector 11 is positioned and fixed to the support 21 by using this recess. The photodetector 11 is connected and fixed on the circuit board 22. In this circuit board 22, a detection signal circuit that generates a detection signal according to the amount of light detected by each light receiving element in the photodetector 11 and a drive for each light emitting source of the semiconductor laser 1 based on this detection signal. An output control circuit for controlling current is integrally mounted.

In the case of this embodiment as well, basically the same effect as that of the above-mentioned embodiment can be obtained, but in particular, as the lens 26 formed by condensing means having a refractive index distribution in the prism 23. Therefore, as compared with the case where the concave mirror 10 and the grating lens 18 are used, the beam shaping means 2
Since 4 is a flat plate and can be formed in a small size, it is easy to handle in terms of mounting and positioning. In addition, since the semiconductor laser 1, the beam shaping means 24, and the light source section including the photodetector 11 and the detection system optical section are positioned and fixed on the same support body 21, the mutual alignment and the positional relationship are maintained. Is easy, and the workability in assembling is good and the maintainability is excellent. Further, since the detection signal circuit and the output control circuit are integrally mounted on the circuit board 22, noise-resistant and highly accurate output control is possible.

[0031]

According to the first aspect of the invention, the laser light emitted from the semiconductor laser having a plurality of light emitting sources is collimated by the collimator lens and then is guided to the deflecting means through the beam shaping means. Then, in the optical scanning device in which the laser light deflected by the deflecting means is imaged on the surface to be scanned by the image forming means to perform optical scanning, the beam shaping means is used to control the beam diameter of each laser light. A prism for enlarging or reducing in at least one of the scanning direction and the sub-scanning direction, a half mirror formed on the exit optical path of this prism, and a prism integrated with the prism to collect light reflected by the half mirror. And a plurality of light receiving elements for individually detecting the reflected light corresponding to each laser beam emitted by being separated by this condensing means. Thus, since the beam shaping means secures the division and separation functions for each laser beam, the number of parts required for detecting the optical output of each laser beam can be reduced, and the work efficiency of assembly and the like can be improved, Miniaturization can be secured.

In this case, according to the second aspect of the invention, the beam shaping means to which the dividing and separating functions are added is positioned and fixed together with the plurality of light receiving elements on the same support, so that the detection optical system for light output is provided. It is possible to maintain the relative positional relationship as described above over time, and to perform stable light output control that is resistant to environmental changes and the like.

According to the third aspect of the present invention, the semiconductor laser, the beam shaping means, and the plurality of light receiving elements are positioned and fixed on the same support, so that the assembling workability is good and the positional relationship between them is aged. It can be maintained for a long time, and the maintainability can be improved.

Further, in the invention described in claim 4, a detection signal circuit for generating a detection signal according to the amount of light detected by the light receiving element and a drive current for each light emitting source of the semiconductor laser are controlled based on the detection signal circuit. Since a plurality of light receiving elements are connected and fixed on a circuit board integrally formed with at least a part of the output control circuit, the detection signal obtained as an analog signal controls the drive current amount of the semiconductor laser in this detection signal circuit. Since it can be transmitted to the output control circuit after being converted into a level signal that is a digital signal to be output, it is possible to perform highly accurate output control that is resistant to noise.

Further, in the invention according to claim 5, since the condensing means is a lens formed by providing a refractive index distribution in the prism, the beam shaping means can be formed as a flat plate and small in size, The handleability can be improved.

[Brief description of drawings]

FIG. 1 is a partially cutaway plan view showing an essential part of a first embodiment of the present invention.

FIG. 2 is a schematic plan view showing the overall configuration.

FIG. 3 shows a second embodiment of the present invention, (a) is a plan view and (b) is a side view.

FIG. 4 is a horizontal sectional view showing a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 semiconductor laser 2 collimator lens 3 prism 4 beam shaping means 6 deflecting means 7 image forming means 8 scanned surface 9 half mirror 10 light collecting means 12 support 13 circuit board 15 prism 16 beam shaping means 17 half mirror 18 light collecting means 19 Collimator lens 21 Support 22 Circuit board 23 Prism 24 Beam shaping means 25 Half mirror 26 Condensing means

Claims (5)

[Claims] 1. A laser beam emitted from a semiconductor laser having a plurality of light emission sources is collimated by a collimator lens into a parallel light flux, and then guided to a deflecting means via a beam shaping means,
In the optical scanning device in which the laser beam deflected by the deflecting unit is imaged on the surface to be scanned by the image forming unit to perform optical scanning, the beam shaping unit controls the beam diameter of each laser beam in the main scanning direction. And a prism that expands or contracts in at least one of the sub-scanning direction, a half mirror formed on the outgoing optical path of this prism, and a prism that is integrated with the prism and has a condensing effect on the reflected light by this half mirror. The optical scanning device is provided with a plurality of light receiving elements which are formed by a condensing means for indicating and emit, and individually detect reflected light corresponding to each laser beam emitted by being separated by the condensing means. . 2. The optical scanning device according to claim 1, wherein the beam shaping means and the plurality of light receiving elements are positioned and fixed on the same support. 3. The optical scanning device according to claim 1, wherein the semiconductor laser, the beam shaping means, and the plurality of light receiving elements are positioned and fixed on the same support. 4. At least one of a detection signal circuit for generating a detection signal according to the amount of light detected by the light receiving element and an output control circuit for controlling a drive current for each light emitting source of the semiconductor laser based on the detection signal. 4. The optical scanning device according to claim 1, wherein a plurality of light receiving elements are connected and fixed on a circuit board which is partially formed integrally. 5. The optical scanning device according to claim 1, wherein the condensing means is a lens formed by providing a refractive index distribution in a prism.