JPH04371070A - Light beam scanner - Google Patents

Abstract

PURPOSE:To suppress the change in wavelength of a laser beam emitting from a semiconductor laser element 10 which is a light source and to stably perform scanning with the laser beam. CONSTITUTION:A laser beam 11 emitting from a semiconductor laser element 10 provided with an active area 14 and a wavelength control area 15 scans a photosensitive drum 33 by means of a hologram scanner 32. A video pattern signal from a video signal output part 60 to be supplied to an ohmic electrode 16 for oscillating the laser beam in the active area 14 of the semiconductor laser element 10 is passed to a conversion electrode 17 of the wavelength control area 15 in the semiconductor laser element 10 via a low pass filter circuit 70 and a wavelength control driver 71. Current corresponding to the low frequency component of the video pattern signal is supplied to the conversion electrode 17 and the wavelength of the laser beam is changed so that the change in wavelength of the laser beam oscillated from the active area 14 can be compensated.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an optical beam scanning device that uses a hologram to scan a laser beam output from a semiconductor laser element. The present invention relates to a light beam scanning device that stably scans a laser beam.

0002

[Prior Art] Semiconductor laser elements are widely used as light sources for optical disks, optical communications, laser printers, etc., and are particularly small and lightweight semiconductors that can directly modulate the emitted laser beam. The laser element is suitable as a light source for a light beam scanning device of a laser printer.

A laser printer using a semiconductor laser element as a light source uses a light beam scanning device that scans a laser beam emitted from the semiconductor laser element along the surface of a photoreceptor drum. A rotating polygon mirror called a polygon mirror is used in the light beam scanning device for laser printers, but polygon mirrors tend to generate noise when rotating at high speeds, and they also require time and effort to process. There is. For this reason, a light beam scanning device using a hologram lens has been developed in place of such a rotating polygon mirror. A light beam scanning device using a hologram lens has a simple structure, so it can be made smaller and lighter in weight, and it is also cheaper because it can be mass-produced.

FIG. 12 shows an example of a light beam scanning device using a hologram lens. The light beam scanning device includes a hologram scanner 80 in which a disk-shaped hologram disk 81 is fixed concentrically to a rotating shaft 87. The hologram disk 81 is provided with a plurality of hologram lenses 83 called interferometric zone plates (IZP) arranged in a circumferential direction. Each hologram lens 83 is connected to a hologram disk 81
The frequency distribution is different along the circumferential direction, and therefore,
The diffraction direction changes sequentially along the circumferential direction of the hologram disk 81. Hologram scanner 8 like this
0, the hologram disk 8 is rotated by the rotation of the rotation shaft 87.
1 is rotated. Then, each hologram lens 83 of the rotated hologram disk 81 is irradiated with a single longitudinal mode laser beam 85 emitted from a semiconductor laser element serving as a light source.

[0005] The laser beam irradiated onto each of the hologram lenses 83 rotating around the hologram disk 81 is diffracted by each hologram lens 83 and focused onto a photosensitive drum 86 . Since each hologram lens 83 sequentially moves around as the hologram disk 81 rotates, the incident position of the laser beam sequentially changes. Thereby, since each hologram lens 83 sequentially changes the diffraction direction of the incident light, the diffraction direction of the laser beam sequentially changes as one hologram lens 83 moves around. The laser beam diffracted by each hologram lens 83 is transmitted to the photoreceptor drum 8.
The light is focused on 6. Since the direction of diffraction by each hologram lens 83 is along the axis of the photoreceptor drum 86, the laser beam is scanned along the axial direction of the photoreceptor drum 86 by one hologram lens 83. . Therefore, when the hologram disk 81 rotates and the laser beam is sequentially irradiated onto each hologram lens 83, the diffracted laser beam is continuously scanned in the same direction along the axial direction of the photoreceptor drum 85. . As a result, the number of scans of the laser beam on the photosensitive drum 86 by one rotation of the hologram disk 81 becomes equal to the number of hologram lenses 83 .

[0006] In this way, a light beam scanning device using a hologram lens does not require the Fθ lens used in a light beam scanning device using a polygon mirror, and moreover, hologram lenses can be mass-produced using a stamp method. Therefore, the price can be reduced.

[0007]

[Problems to be Solved by the Invention] In a light beam scanning device using a hologram lens, a single longitudinal mode refractive index guided semiconductor laser element is used to focus the laser beam on the photoreceptor drum 86. is necessary. However, conventional F. P. In an index-guided semiconductor laser device, a phenomenon called mode hopping occurs in the emitted laser beam. This mode hopping is a phenomenon in which the oscillation wavelength jumps to adjacent longitudinal modes separated by, for example, about ±0.3 nm due to changes in ambient temperature, drive current, pulse width of the drive current, and the like. In the optical beam scanning device using the hologram lens shown in FIG. 12, when a mode hopping phenomenon occurs in the laser beam oscillated from the semiconductor laser element, the laser beam 85 diffracted by the hologram lens 83 changes as shown by the broken line. , the image formation position on the photoreceptor drum 86 is shifted and scanned.

For example, assuming that the wavelength of the semiconductor laser is λ, the angle of incidence of the laser beam on the hologram scanner 80 is θ1, the interference fringes on the hologram are perpendicular to the plane of incidence, the spatial frequency is f, and the angle of incidence of the laser beam on the hologram scanner 80 is f. When the diffraction angle is θ2, the following relationship holds true.

[0009] sin θ1=f・λ−sin θ1 Therefore,
The change Δθ2 in the diffraction angle when the wavelength λ changes by Δλ is as follows: Δθ2=f·Δλ/cosθ2. In semiconductor laser devices used as light sources,
In reality, a wavelength fluctuation of about 0.5 nm occurs, so the wavelength change of the laser beam Δλ=0.5×10−
6 (mm), the spatial frequency f = 1800 (lines/m
m), when the diffraction angle θ2 of the laser beam is 45 (deg), Δθ2 = 1.27 x 10-3 (rad), and the diffraction angle changes by 1.27 x 10-3 (rad). . In a laser printer, the photosensitive drum 86 is usually 300 mm away from the laser beam incident position on the hologram scanner 80.
The deviation Δx in the scanning direction of the laser beam above is Δx=300·Δθ2=0.38 (mm).

As described above, in a laser printer, the oscillation wavelength of the semiconductor laser element used as a light source is 0.
A variation of about 5 nm causes a positional deviation of the laser beam on the photosensitive drum 86 of about 0.38 mm with respect to the scanning direction. As a result, the quality of images such as characters formed on the photoreceptor drum 86 deteriorates. For this reason, it is required to suppress the oscillation wavelength of the semiconductor laser element to about 0.5 nm or less.

A semiconductor laser element in a laser printer is normally driven by an oscillating current based on a video pattern signal, which is a rectangular wave pulse signal, as shown in FIG. As described above, when the oscillation current fluctuates in a pulsed manner, the internal temperature of the semiconductor laser element fluctuates, and the wavelength of the laser beam emitted from the semiconductor laser element fluctuates. Even if the oscillation wavelength fluctuates even slowly due to a change in the internal temperature of the semiconductor laser element, the laser beam will be diffracted by the hologram lens 83 and imaged on the photoreceptor drum 86, resulting in aberrations at the imaging position. As a result, the quality of images such as characters formed on the surface of the photoreceptor drum 86 deteriorates.

[0012] As described above, in a light beam scanning device for a laser printer that utilizes diffraction by a hologram lens, it is necessary to suppress deterioration in image quality due to fluctuations in the wavelength of the laser beam.

In order to solve this problem, Japanese Patent Laid-Open No. 61-90123 discloses a hologram equipped with a temperature control circuit that equalizes the amount of heat generated by a semiconductor laser element during laser beam oscillation and non-oscillation. A light beam scanning device based on this method is disclosed. However, such a configuration has problems in that temperature control is not easy and the structure of the control circuit is complicated.

The present invention solves these problems, and its purpose is to highly accurately stabilize the wavelength of a laser beam emitted from a semiconductor laser element used as a light source with a simple configuration. The object of the present invention is to provide a light beam scanning device that can perform the following steps.

[0015]

[Means for Solving the Problems] The optical beam scanning device of the present invention includes an active region that oscillates a laser beam at a wavelength corresponding to an injected current, and a laser beam injected with a wavelength corresponding to the wavelength of the laser beam oscillated in the active region. a semiconductor laser element having a wavelength control region that changes and emits light in response to a current;
A plurality of hologram lenses that diffract reproduced waves emitted from the semiconductor laser element and scan the diffracted waves on a surface to be scanned, and a hologram disk in which the hologram lenses are arranged side by side in the circumferential direction and are rotated in a predetermined direction. and means for controlling the current injected into the wavelength control region based on the current injected into the active region of the semiconductor laser element, thereby achieving the above object. be done.

The light beam scanning device of the present invention includes a wavelength fluctuation detection means for detecting wavelength fluctuation of a laser beam emitted from the semiconductor laser element, and a wavelength fluctuation detection means for detecting a wavelength fluctuation of the laser beam emitted from the semiconductor laser element, and a wavelength fluctuation detection means for detecting a wavelength fluctuation of the laser beam emitted from the semiconductor laser element. The device further includes control means for controlling the current injected into the active region of the device.

Furthermore, the optical beam scanning device of the present invention includes an active region that oscillates a laser beam at a wavelength corresponding to the injected current, and a wavelength of the laser beam oscillated in the active region that corresponds to the injected current. a semiconductor laser element having a wavelength control region that changes and emits light; a plurality of hologram lenses that diffract a reproduced wave emitted from the semiconductor laser element and scan the diffracted wave on a surface to be scanned; and each hologram lens. a hologram scanner having a hologram disk arranged in parallel in a circumferential direction and rotated in a predetermined direction; a wavelength fluctuation detection means for detecting a wavelength fluctuation of a laser beam emitted from the semiconductor laser element; control means for controlling the current injected into the wavelength control region based on the wavelength control region, thereby achieving the above object.

[0018]

In the optical beam scanning device of the present invention, a laser beam is oscillated by a current injected into the active region of a semiconductor laser element. At this time, a current controlled based on the current injected into the active region is injected into the wavelength control region of the semiconductor laser element to compensate for wavelength fluctuations of the laser beam emitted from the wavelength control region. A laser beam emitted from a semiconductor laser beam is diffracted and scanned by a hologram scanner.

In addition to controlling the current in the wavelength control region, the wavelength fluctuation of the laser beam emitted from the semiconductor laser element is detected by the wavelength fluctuation detection means, and the wavelength fluctuation detected by the wavelength fluctuation means is detected. The current injected into the active region of the semiconductor laser device is controlled to compensate.

Furthermore, in the light beam scanning device of the present invention,
When a wavelength fluctuation of a laser beam emitted from a semiconductor laser element is detected by a wavelength fluctuation detector, a current injected into a wavelength control region of the semiconductor laser element is controlled so as to compensate for the wavelength fluctuation.

[0021]

【Example】

<Embodiment 1> A first embodiment of a light beam scanning device for a laser printer according to the present invention will be described below. As shown in FIG. 1, this optical beam scanning device includes a semiconductor laser device 10 as a light source, and a hologram scanner 32 that diffracts the laser beam emitted from the semiconductor laser device 10.
and a photosensitive drum 33 on which the laser beam diffracted by the hologram scanner 32 is focused. The semiconductor laser element 10 is a distributed reflection type (
DBR: Distributed-Bragg Ref
(1) A semiconductor laser device is used. A single longitudinal mode laser beam 11 emitted from the semiconductor laser 10 is imaged and scanned by a hologram scanner 32 on the surface of a photosensitive drum 33, which is a surface to be scanned. The hologram scanner 32 includes a hologram disk 34 fixed concentrically to a rotating shaft 35, and a plurality of hologram lenses 36 arranged in parallel in the circumferential direction of the hologram disk 34. Each hologram lens 36 has an interferometric zone plate (
IZP) is used, and each hologram lens (IZP) is used.
P) By sequentially changing the incident position of the laser beam at 36, the diffraction angle of the laser beam changes sequentially. By rotating the hologram disk 34,
When the incidence plate of the laser beam to each hologram lens 36 is sequentially changed, the diffracted light is transferred to the photoreceptor drum 33.
The surface is scanned along the axial direction. Then, by rotating the hologram disk 34, one hologram lens 3
When the laser beam is incident on the next hologram lens 36, the diffracted laser beam scans the surface of the photoreceptor drum 33 in the same direction.

As shown in FIG. 2, the distributed reflection semiconductor laser device 10 used as a light source has an active region 14 and a wavelength control region 15 independently provided on one semiconductor substrate 13. There is. The semiconductor laser device 1
0 is made of, for example, an AlGaAs-based material, and in the active region 14, a cladding layer 2 is formed on the semiconductor substrate 13.
0, an active layer 21, a cladding layer 22, and a contact layer 23 are sequentially laminated, and an ohmic electrode 16 is provided on the contact layer 23. Further, in the wavelength control region 15, a cladding layer 24 is laminated on the semiconductor substrate 13, and a guide layer 25 having a diffraction grating 26 is laminated on the cladding layer 24. A laser beam oscillated in the active region 21 is guided through the guide layer 25 . A cladding layer 27 is laminated on the guide layer 25, and a conversion electrode 17 is formed on the cladding layer 27. An electrode 12 is provided on the back side of the semiconductor substrate 13 over the entire active region 14 and wavelength control region 15 .

In the semiconductor laser device 10 having such a structure, a laser beam is oscillated from the active layer 21 by an oscillation current flowing from the ohmic electrode 16 of the active region 14. While the laser beam oscillated from the active layer 21 is guided through the guide layer 25 in the wavelength control region 15, its wavelength is changed by the wavelength control current Ic injected from the conversion electrode 17, and the wavelength of the laser beam is changed by the wavelength control current Ic injected from the conversion electrode 17. The light is emitted from the emission surface. As shown in FIG. 3, the wavelength λ of the laser beam emitted from the semiconductor laser device 10 is inversely proportional to the wavelength control current Ic injected into the conversion electrode 17 of the wavelength control region 15. I see, the wavelength becomes continuously shorter. Further, as shown in FIG. 4, such a distributed reflection type semiconductor laser device 10 has a temperature range of 5 to 60° C., which is the environmental temperature of a normal optical beam scanning device.
The mode hopping phenomenon in which the wavelength changes rapidly does not occur, and the wavelength changes continuously due to temperature changes.

Semiconductor laser device 10 having such a configuration
is controlled by the control circuit shown in FIG. A laser driver 61 is connected to the ohmic electrode 16 provided in the active region 14 of the semiconductor laser device 10, and the laser driver 61 receives a video signal which is a rectangular wave pulse signal output from the video signal input section 60. Controlled by pattern signals. Therefore, the laser driver 61 injects a predetermined pulse current into the ohmic electrode 16 of the semiconductor laser device 10 in accordance with the video pattern signal output from the video signal output section 60. Further, the output of the video signal output section 60 is also given to a low-pass filter circuit 70, and the output of the low-pass filter circuit 70 is given to a wavelength control driver 71. The low-pass filter circuit 70 includes a resistor 73 connected to the output terminal of the video signal output section 60, a comparator 72 to which the resistor 73 is connected to the + input terminal, and a connection point between the comparator 72 and the resistor 73. The output of the comparator 72 is applied to the input terminal of the comparator 72 and also to the wavelength control driver 71. The output of the wavelength control driver 71 is the output of the semiconductor laser element 10.
A current controlled by a wavelength control driver 71 is input to the conversion electrode 17 provided in the wavelength control region 15 .

The wavelength of the laser beam 11 oscillated from the semiconductor laser device 10 changes due to changes in the internal temperature of the semiconductor laser device 10. It has been newly discovered that the frequency is approximately proportional to the low frequency component contained in the pulsed video signal output from the 60. For example, if the pulse signal input from the laser driver 61 to the ohmic electrode 16 is dense due to the video pattern signal,
Since the amount of heat dissipated is small compared to the amount of heat generated inside the semiconductor laser element 10, the temperature inside the chip rises.
The refractive index in the waveguide of the semiconductor laser device 10 changes, and the wavelength of the emitted laser beam 11 changes to the longer wavelength side.

In this embodiment, the wavelength of the laser beam emitted from the semiconductor laser element 10 is compensated based on the low frequency component contained in the video signal. A pulsed video signal output from the video signal output unit 60 applies current to the ohmic electrode 16 in the active region 14 of the semiconductor laser device 10, and a laser beam is oscillated from the active layer 21 of the active region 14. . On the other hand, the video pattern signal output from the video signal output section 60 is input to a low-pass filter circuit 70,
The low-pass filter circuit 70 extracts only low frequency components in the video pattern signal. The low-pass filter circuit 70 outputs a signal proportional to the low frequency component to the wavelength control driver 71. Then, the wavelength control driver 71 applies a current based on the output of the low-pass filter 70 to the wavelength control region 15 in the semiconductor laser device 10.
to the conversion electrode 17. As a result, the wavelength control region 15 in the semiconductor laser device 10 controls the wavelength of the laser beam oscillated in the active region 14 so as to suppress wavelength fluctuations of the laser beam due to temperature changes occurring inside the semiconductor laser device 10. change.

In this way, the semiconductor laser device 1 is controlled by the video pattern signal outputted from the video signal output section 60.
At the same time, the wavelength fluctuation due to the increase in internal temperature of the semiconductor laser device 10 is predicted based on the low frequency component of the video pattern signal, and the wavelength of the laser beam oscillated in the active region 14 is compensated. , wavelength control region 1
A current is applied to 5. As a result, the semiconductor laser element 1
The laser beam 11 oscillated from 0 is emitted in a stable state in which wavelength fluctuations due to changes in the internal temperature of the semiconductor laser element 10 are compensated for. Moreover, the semiconductor laser element 10 has no wavelength fluctuation due to mode hopping, and the emitted laser beam is transmitted to the hologram scanner 3.
2, the photosensitive drum 33 is stably scanned.

In the above embodiment, a distributed reflection type (DBR) semiconductor laser element is used as the semiconductor laser element 10, but the present invention is not limited to this. For example, a distributed feedback type (DBF) shown in FIG.
ak) A semiconductor laser device 10' can also be used. This distributed feedback semiconductor laser device 10' includes a cladding layer 20' and an active layer 21 on a semiconductor substrate 13 in an active region 14'.
A cladding layer 25' having a diffraction grating 26' and a diffraction grating 26' are sequentially laminated, and a contact layer 23' and a cap layer 28' are sequentially laminated on the cladding layer 25'. Then, an ohmic electrode 16 is placed on the cap layer 28'.
' is provided. Moreover, in the wavelength control region 15',
A cladding layer 24' and a guide layer 2 are formed on the semiconductor substrate 13'.
5' and a cladding layer 27' are sequentially laminated,
A conversion electrode 17' is provided on the cladding layer 27'. An electrode 12' is provided on the back surface of the semiconductor substrate 13' over both the active region 14' and the wavelength control region 15'.

[0029] Such a semiconductor laser device also has 5
In the temperature range of ~60° C., there is no risk of mode hopping occurring, and therefore, the wavelength of the laser beam does not vary due to mode hopping. And Figure 1
A control circuit similar to the control circuit shown in Figure 1 can compensate for variations in the wavelength of the emitted laser beam due to changes in internal temperature.

<Embodiment 2> FIG. 6 is a schematic diagram of a second embodiment of the light beam scanning device of the present invention. In this example, a distributed reflection semiconductor laser device 10 shown in FIG. 2 is used as a light source.
is used and has an active region 14 and a wavelength control region 15. A video pattern signal output from a video signal output section 60 is applied to the ohmic electrode 16 provided in the active region 14 via a laser driver 61. The laser beam oscillated in the active region 14 by the oscillation current based on the video pattern signal has its wavelength converted by the wavelength control region 15 and is emitted.

The laser beam 11 emitted from the semiconductor laser device 10 is collimated by a collimator lens 30 and is incident on a half mirror 31 . The laser beam incident on the half mirror 31 is split into two, one laser beam 11a passes through the half mirror 31, and the other laser beam 11b passes through the half mirror 31.
is refracted almost at right angles. The laser beam 11a that has passed through the half mirror 31 is applied to the photosensitive drum 33 via the hologram scanner 32. The hologram scanner 32 has the same configuration as the hologram scanner 32 in the first embodiment, so a description thereof will be omitted. Laser beam 11 refracted by half mirror 31
b is diffracted into a parallel beam by the parallel hologram 40, and the first-order diffracted light is reflected by the condensing lens 41.
Each light receiving surface 43 and 44 of the two-split photodiode 42
The light is focused on. The light-receiving surfaces 43 and 44 of the two-split photodiode 42 are positioned so that when a laser beam of a predetermined wavelength is irradiated, the amount of light received by each light-receiving surface 43 and 44 is equal. By varying the wavelength of the laser beam, each light-receiving surface 4
3 and 44, the amount of light received varies.

The two-split photodiode 42 outputs a signal corresponding to the amount of light received by each light-receiving surface 43 and 44, and each output signal is provided to a differential amplifier 50. The differential amplifier 50 is designed to calculate the difference between input signals and amplify and output the result, and its output is as follows.
The signal processing circuit 52 is provided with the signal processing circuit 52 . The signal processing circuit 5
The output of 2 is transmitted to the conversion electrode 17 in the wavelength control region 15 of the semiconductor laser device 10 via the wavelength control driver 71.
is given to. The signal processing circuit 52 compares the output of the differential amplifier 50 corresponding to the difference in the amount of light received by the light receiving surfaces 43 and 44 of the two-split photodiode 42 with a preset reference value, and determines the difference between the two. If there is a difference,
The wavelength of the laser beam corresponding to the difference is calculated, and a predetermined signal is output to the wavelength control driver 71 so that the difference disappears, so that the laser beam from the wavelength control driver 71 has a predetermined wavelength. A predetermined current is output to the conversion electrode 17 of the wavelength control region 15 in the semiconductor laser device 10. Thereby, the wavelength of the laser beam emitted from the semiconductor laser element 10 is set to a predetermined value.

[0033] In the light beam scanning device having such a configuration,
The output from the semiconductor laser element 10 is sent to the half mirror 31
The laser beam 11a that has passed through the hologram scanner 32 scans the surface of the photoreceptor drum 33. On the other hand, the laser beam 11b refracted by the half mirror 31 is diffracted by the parallel hologram 40 at a diffraction angle corresponding to its wavelength, and after being focused by the lens 41, the laser beam 11b is refracted by the parallel hologram 40, and then focused by the lens 41. and 44. Each light receiving surface 43 and 44 outputs a signal corresponding to the amount of light received. The difference between the outputs of the divided light receiving surfaces 43 and 44 is calculated and amplified by a differential amplifier 50 and input to a signal processing circuit 52 . The signal processing circuit 52 calculates a wavelength based on the difference in the amount of light received by each light receiving surface 43 and 44, and compares the calculated wavelength with a reference wavelength. When the wavelength of the laser beam is equal to the reference wavelength, the signal processing circuit 52 does not output a signal for driving the wavelength control driver 71.

On the other hand, for example, due to a change in the internal temperature of the semiconductor laser element 10, the output laser beam 1
1 fluctuates and deviates from the reference wavelength, the laser beam 11b refracted by the half mirror 31 becomes
The diffraction angle by the parallel hologram 40 changes, and the condensing position on the two-split photodiode 42 is moved by the condensing lens 41. As a result, each light receiving surface 4 of the two-split photodiode 42
The amount of light received by the light receiving surfaces 43 and 44 varies, and the wavelength calculated based on the difference in the amount of light received by the light receiving surfaces 43 and 44 is different from the reference wavelength preset in the signal processing circuit 52. be in a different state. In this case, the signal processing circuit 52 outputs a predetermined signal to the wavelength control driver 71 so that the wavelength of the laser beam becomes equal to the reference wavelength. Then, the wavelength control driver 71 controls the conversion electrode 1 in the wavelength control region 15 in the semiconductor laser device 10.
A predetermined current is applied to the semiconductor laser 10, and the wavelength of the laser beam 11 generated from the semiconductor laser 10 is changed.

In this way, fluctuations in the wavelength of the laser beam due to changes in the internal temperature of the semiconductor laser device 10 are compensated for, and the wavelength of the laser beam is always kept constant. By keeping the wavelength of the laser beam constant, the half mirror 3
The wavelength of the laser beam 11a that passes through 1 also becomes constant,
There is no fear that the laser beam 11a, which is diffracted by the hologram scanner 32 and scans the photosensitive drum 33, will shift with respect to the scanning direction. As a result, a laser printer having such a light beam scanning device can form clear images without distortion at high speed.

Note that the distributed feedback semiconductor laser device shown in FIG. 5 can also be used in this embodiment.

<Embodiment 3> FIG. 7 is a schematic diagram of a main part of a third embodiment of the optical beam scanning device of the present invention. In this example,
A distributed reflection type (DBR) semiconductor laser device 10 shown in FIG. 2 is used as a light source, and the semiconductor laser device 10
The oscillation current output from the laser driver 61 is applied to the ohmic electrode 16 of the active region 14 in . The laser driver 61 is driven by a video pattern signal, which is a rectangular pulse signal output from the video signal output section 60, and is controlled by the output of the signal processing circuit 52, as will be described later. The conversion electrode 17 of the wavelength control region 15 in the semiconductor laser device 10 is supplied with a wavelength control current output from the wavelength control driver 71 . The wavelength control driver 71 is controlled by the output of a low-pass filter circuit 70 that extracts low frequency components of the video pattern signal output from the video signal output section 60.

The laser beam emitted from the semiconductor laser device 10 is irradiated onto a half mirror 31 via a collimator lens 30, as in the second embodiment, and the laser beam 11a transmitted through the half mirror 31 is The photoreceptor drum 33 is scanned by the hologram scanner 32 . Further, the laser beam 11b refracted at a substantially right angle by the half mirror 31 is irradiated onto each of the light receiving surfaces 43 and 44 of the two-split photodiode 42 via the parallel hologram 40 and the condensing lens 41. Then, the difference in output corresponding to the amount of light received by each light receiving surface 43 and 44 of the photodiode 42 is determined by the differential amplifier 5.
0 and is amplified, and the signal processing circuit 52 calculates the wavelength of the laser beam based on the difference in the amount of light received by each of the light receiving surfaces 43 and 44. The calculated wavelength is compared with a reference wavelength, and the laser driver 61 is controlled based on the difference between the two. Thereby, the ohmic electrode 16 in the active region 14 of the semiconductor laser device 10 is controlled, and the oscillation wavelength of the laser beam in the active region 14 is changed.

As described above, in this embodiment, the wavelength fluctuation caused by the temperature change inside the semiconductor laser element 10 that occurs based on the low frequency component of the video pattern signal output from the video signal output section 60 is controlled by the wavelength control current. In addition to compensating by changing the
Compensation is performed by calculating based on the laser beam emitted from zero and changing the oscillation current.

In the semiconductor laser device 10 of this embodiment, as shown in FIG. 8, the wavelength control applied to the conversion electrode 17 of the wavelength control region 15 in the semiconductor laser device 10 is proportional to the low frequency component in the video pattern signal. Current Ic
is changed. As shown in FIG. 9, the wavelength of the laser beam emitted from the semiconductor laser element 10 is inversely proportional to the magnitude of the wavelength control current Ic, and the wavelength becomes shorter as the wavelength control current Ic becomes larger. Further, the relationship between the oscillation current Is applied to the ohmic electrode 16 of the active region 14 in the semiconductor laser device 10 and the wavelength of the laser beam output from the semiconductor laser device 10 is as shown in FIG. In the case of a constant value, it is proportional in a region larger than the threshold current, and the larger the oscillation current is, the larger the output wavelength becomes. In the semiconductor laser device 10, as shown in FIG. 11, when the wavelength control current Ic is kept constant and the oscillation current Is is applied to the ohmic electrode 16 to oscillate a laser beam, the output wavelength changes over time due to internal heat generation. However, in this embodiment, by capturing the laser beam actually emitted from the semiconductor laser device 10, calculating its wavelength fluctuation, and changing the oscillation current Is given to the ohmic electrode 16, the semiconductor laser device 1
It also compensates for wavelength fluctuations that occur over time.

In this embodiment as well, the distributed feedback semiconductor laser device shown in FIG. 5 can be used as a light source.

[0042]

As described above, the optical beam scanning device of the present invention can reduce the wavelength fluctuation of the laser beam caused by the oscillation current applied to oscillate the laser beam from the semiconductor laser element by using the current applied to the wavelength control region. Since the wavelength fluctuation is controlled and compensated for, a laser beam with suppressed wavelength fluctuation is emitted from the semiconductor laser element. As a result, it is stably scanned by the hologram scanner. Furthermore, even if the wavelength fluctuation cannot be completely suppressed by compensation based on changes in the wavelength control current, the wavelength fluctuation is detected based on the actually emitted laser beam, and the oscillation wavelength current is adjusted based on the detection result. Since the wavelength is changed, fluctuations in the wavelength of the emitted laser beam can be suppressed more reliably.

[0043]Furthermore, since wavelength fluctuation is detected based on the laser beam emitted from the semiconductor laser element and the wavelength control current is controlled based on the detection result, wavelength fluctuation occurs in the emitted laser beam. However, even if the laser beam is scanned stably, the fluctuation is reliably suppressed and the laser beam can be scanned stably.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a light beam scanning device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a distributed reflection semiconductor laser element used in the light beam scanning device.

FIG. 3 is a graph showing the relationship between the input current of the semiconductor laser device shown in FIG. 2 and the wavelength of the emitted laser beam.

FIG. 4 is a graph showing the relationship between the ambient temperature of the semiconductor laser device shown in FIG. 2 and the wavelength of the emitted laser beam.

FIG. 5 is a sectional view of another embodiment of a semiconductor laser device used in the light beam device of the present invention.

FIG. 6 is a configuration diagram of a light beam scanning device according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram of a light beam scanning device according to a third embodiment of the present invention.

FIG. 8 is a graph showing the relationship between a video pattern signal of a semiconductor laser element and a wavelength control current in the optical beam scanning device.

FIG. 9 is a graph showing the relationship between the wavelength control current of the semiconductor laser beam device and the oscillation laser beam wavelength.

FIG. 10 is a graph showing the relationship between the oscillation current of the semiconductor laser beam device and the oscillation laser beam wavelength.

FIG. 11 is a graph showing changes over time in the oscillation laser beam wavelength of the semiconductor laser beam device.

FIG. 12 is a configuration diagram showing a conventional light beam scanning device.

FIG. 13 is a graph showing the relationship between fluctuations in the video pattern signal of the semiconductor laser element and changes in the oscillation laser beam wavelength in the optical beam scanning device.

[Explanation of symbols]

10 Semiconductor laser element 11 Laser beam 32 Hologram scanner 33 Photoreceptor drum 34 Hologram disk 36 Homgram lens 40 Parallel hologram 42 Two-part photodiode 50 Differential amplifier 52 Signal processing circuit 60 Video signal input section 61 Laser driver 70 Low pass filter circuit 71 Wavelength control driver

Claims (3)

[Claims] 1. An active region that oscillates a laser beam at a wavelength corresponding to the injected current, and wavelength control that changes the wavelength of the laser beam oscillated in the active region in accordance with the injected current and emits the laser beam. a semiconductor laser element having a region, a plurality of hologram lenses that diffract reproduced waves emitted from the semiconductor laser element and scan the diffracted waves on a surface to be scanned, and each hologram lens arranged in parallel in the circumferential direction to a predetermined position. A light beam comprising: a hologram scanner having a hologram disk rotated in a direction; and means for controlling a current injected into the wavelength control region based on a current injected into an active region of the semiconductor laser element. scanning device. 2. Wavelength fluctuation detection means for detecting wavelength fluctuation of a laser beam emitted from the semiconductor laser element; and a wavelength fluctuation detection means for detecting wavelength fluctuation of a laser beam emitted from the semiconductor laser element; The light beam scanning device according to claim 1, further comprising control means for controlling the current. 3. An active region that oscillates a laser beam at a wavelength corresponding to the injected current, and wavelength control that changes the wavelength of the laser beam oscillated in the active region in accordance with the injected current and emits the laser beam. a semiconductor laser element having a region, a plurality of hologram lenses that diffract reproduced waves emitted from the semiconductor laser element and scan the diffracted waves on a surface to be scanned, and each hologram lens arranged in parallel in the circumferential direction to a predetermined position. a hologram scanner having a hologram disk rotated in the direction; a wavelength fluctuation detection means for detecting wavelength fluctuation of a laser beam emitted from the semiconductor laser element; A light beam scanning device comprising: control means for controlling a current.