JP2000153635A - Optical recorder employing multibeam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the ratio of beam interval to beam diameter by setting the interval of a multi-beam from an optical waveguide element narrower than that of the input coupling part of a plurality of optical fibers and the optical waveguide element and tapering the optical waveguide element at the light output part. SOLUTION: Laser light emitted from the semiconductor laser in a plurality of laser modules 1 is introduced to a plurality of corresponding optical fibers 2 and the laser light exiting therefrom is coupled with an optical waveguide 5 on corresponding optical waveguide substrate 4. The interval of a multi-beam 14 emitted from an optical waveguide element substrate 4 is set narrower than that of the input coupling part 3 of the plurality of optical fibers 2 and the substrate 4. Further, the optical waveguide 5 on the optical waveguide element substrate 4 is tapered at the light output part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In order to realize a high-speed laser printer, the rotation speed of a rotary polygon mirror must be increased so that repetition of optical scanning can be accelerated. In addition, high-speed modulation can be performed to perform optical modulation corresponding to data to be printed. Is needed. A laser printer using a multi-beam is an effective means because the rotation speed of the rotary polygon mirror and the light modulation speed can be reduced by the number of multi-beams. It is necessary to increase the number.

FIG. 2 shows an example of a laser printer using a plurality of semiconductor lasers, particularly an example of the optical system. Reference numeral 1 denotes a laser module which guides laser light from a semiconductor laser to an optical fiber 2. The plurality of optical fibers are arranged in a line in the optical fiber array arrangement unit 17. The multi-beams emitted from the fiber array unit are converted into parallel lights by the coupling lens 8, and the rotating polygon mirror 9 collectively scans the photosensitive drum with light. Reference numeral 11 denotes a photodetector for detecting the scanning position of the laser beam. Optical fiber array unit 1
FIG. 3 is a side view as viewed from the light emitting portion 7. The optical fiber array portion has a structure in which the optical fiber from which the coating has been removed is held on a V-groove 18 formed by anisotropic etching of a Si crystal, pressed with a glass plate 19, and bonded with an adhesive 20. Reference numeral 21 denotes a clad portion of the optical fiber, and reference numeral 22 denotes a core portion. Light propagates through the core portion 22. Usually, the outer diameter of the cladding is 125 μm and the diameter of the core is 5
μm, and the beam diameter of the laser light propagating through the core is also about 5 μm. Therefore, the ratio between the diameter of the beam emitted from the optical fiber and the interval between the beams is 5: 125 = 1: 25 even if the optical fibers are arranged in close contact with each other, which is usually a value higher than this. Since this ratio is maintained even after passing through the optical system, in order to scan such a multi-beam and form continuous and close scanning lines, as shown in FIG. Scanning is performed with the arrangement direction of the light spot row formed in the step (1) being oblique. The setting of the oblique angle is performed by integrating the optical fiber array unit 17 and the coupling lens 8 and adjusting the rotation as shown in FIG. FIG. 4A is a diagram for explaining this scanning method, in which the light spot array 13 formed on the photosensitive drum is scanned obliquely with respect to the scanning direction.
The size of the light spot, schematic equal to the distance P _S of the scanning line, when collectively scan the multi-beam, a plurality of scanning lines closely spaced can be formed. That is, assuming that the interval between the light spots is P ₀ , if it is set to θ determined by the relational expression of P ₀ sin θ = P _S (1), a close scanning line can be realized. P _S as shown in the previous example: P ₀ = 1: When 25, obtained as theta = 2.3 ° from the equation (1). P _S :
Since the ratio of P ₀ is small, that is, since the arrangement interval of the light spots is considerably larger than the size of the light spots,
θ is a small angle. By the way, in order to realize high-quality printing, it is necessary to keep the scanning line interval with high accuracy within a predetermined error. Next, the effect of the oblique angle error on the scanning line interval will be examined. From the equation (1), the following equation is established between the oblique angle error Δθ and the scanning line interval error ΔP _S.

ΔP _s / P _s = Δθ / θ (2) As the oblique angle θ is smaller, the error of this angle has a greater effect on the deviation of the scanning line interval. For example, when it is desired to suppress the scanning line interval error to within 1%,
% Or less. In the case of θ = 2.3 degrees described above,
It is necessary to set the angle with high accuracy of 0.023 degrees or less. If, for example, .theta. = 30 degrees as in the example described later, the accuracy of 0.3 degrees is sufficient, and the 13 times precision is relaxed. Also, in the optical fiber arrangement shown in FIG. 3, if the number of multi-beams is increased because the interval between the generated multi-beams is large, the beams at both ends are greatly separated from the optical axis of the optical system, and Deterioration of aberration characteristics becomes a problem. That is, the lenses 8 and 10 shown in FIG. 2 use a high-precision so that good characteristics can be maintained for a beam far away from the optical axis when using a multi-beam, as compared with a case using a single beam. It is necessary to use a proper one. Therefore, the laser printer of FIG. 2 cannot increase the number of multi-beams,
There was a limit to high-speed printing.

[0005]

Accordingly, in the present invention, the ratio of the beam interval to the beam diameter of the multi-beam is reduced, that is, by generating the multi-beams arranged at a high density, the scanning line interval can be adjusted with high precision. To be able to set and realize high quality printing. Another object is to realize a higher-speed optical recording apparatus by increasing the number of multi-beams without deteriorating the characteristics of the optical system by arranging at high density.

[0006]

According to the present invention, there is provided an optical recording apparatus which emits multi-beams arranged in a row from a multi-beam generating section, and collectively scans an optical recording material. The multi-beam generation unit includes:
A plurality of semiconductor lasers, a plurality of optical fibers for transmitting a single mode beam, and an optical waveguide element provided with a plurality of optical waveguides for transmitting a single mode beam on a single substrate; The emitted laser light is guided to the corresponding plurality of optical fibers, and the laser light emitted from the optical fiber is input-coupled to the optical waveguide on the corresponding optical waveguide element, and emitted from the optical waveguide element. The beam interval of the multi-beams is narrower than the interval between the plurality of optical fibers and the input connection part of the optical waveguide element, thereby realizing an optical recording apparatus using the multi-beams. Further, when the width of the optical waveguide on the optical waveguide element is widened in a tapered shape at the optical output portion, the width of the beam emitted from the optical waveguide increases, and the ratio of the beam size to the beam interval of the multi-beam increases. can do. In addition, good results can be obtained by affixing a flat glass to the light output portion of the optical waveguide element and making the light output portion of the optical waveguide element concave. Further, in the optical recording device, in the optical recording device in which the multi-beams are emitted from the multi-beam generating unit in a row and are collectively scanned on the optical recording material, the multi-beams are generated at positions where all the generated multi-beams intersect. Good results can be obtained even if a beam shape limiting member that limits the size of the beam in the arrangement direction is provided.

[0007]

FIG. 5 shows a multi-beam generating section used in the present invention. Reference numeral 1 denotes a laser module which guides laser light from a semiconductor laser to an optical fiber 2.
Reference numeral 41 denotes an optical waveguide element, and a plurality of optical waveguides 5 are formed on the flat substrate 4. The plurality of optical fibers are guided to the optical waveguide 5 of the optical waveguide device 41. Since the holding member such as a ferrule is mounted on the optical fiber, the distance between the optical fiber and the optical waveguide is as large as about several mm. The optical waveguide of the light input section is bent to reach the light output section 51. Light output unit 5
In No. 1, the optical waveguides are arranged at equal intervals so that the emitted multi-beams are at equal intervals and the beam intervals are narrow, and the intervals are reduced. FIG. 6 shows a typical structure of the optical waveguide. In the ridge type shown in FIG. 6A, an optical waveguide 52 is formed on a substrate 4 with a material having a high refractive index. FIG. 6 (b)
In the embedded type, the waveguide 53 is embedded with a lower refractive index than the waveguide material. If the size of the beam propagating in the optical fiber and the size of the beam propagating in the optical waveguide match, the coupling efficiency between the optical fiber and the optical waveguide element can be increased, so that the width of the optical waveguide is also reduced. Approximately equal to the core diameter of the fiber. In the above example, it is about 5 μm. FIG. 7 shows an enlarged view of the light output section 51 of the optical waveguide element. In the light output section, the plurality of waveguides are arranged at equal intervals. Numerals 31 and 32 denote a beam propagating through the optical waveguide and a beam exiting, respectively. Since the arrangement interval of the optical waveguides can be narrowed to such an extent that the coupling between the waveguides can be ignored, a high-density arrangement of, for example, about 10 μm is possible if the diameter of the propagating beam is 5 μm. The flat glass 6 is bonded to the output end of the optical waveguide element 41 in FIG. This has the following functions in addition to preventing the output end of the optical waveguide element from being chipped. Sunahachi,
Since the beam emitted from the waveguide has a size of several μm, if dust adheres to the end of the waveguide, serious light output degradation will be caused. However, since the light emitted from the glass spreads at the glass emission end, it is hardly affected by dust. In addition, since the amount of light reflected from the emission end of the glass and returning to the semiconductor laser is significantly smaller than when there is no glass, the light output of the semiconductor laser fluctuates when the laser light returns to the semiconductor laser. Problems can be solved. FIG. 12 shows a waveguide 5 formed on a substrate 4 of an optical waveguide element.
FIG. 4 is a diagram for explaining a beam emitted from a. Assuming that the diameter of the beam emitted from the waveguide is d, the beam diameter D on the air side surface of the glass plate having the thickness a is approximately the following equation. D = d [1+ (4λa / (πd ² )) ² ] ^0.5 (3) where λ is the wavelength of light. For example, λ = 0.64μ
Assuming that m, d = 5 μm, and a = 1 mm, from equation (3), D = 163 μm. That is, 5μ at the end of the optical waveguide
The output beam having the size of m 2 is expanded to 163 μm at the glass end, and the above-mentioned remarkable effect can be expected. FIG. 1 shows a diagram in which the multi-beam generating element shown in FIG. 5 is applied to a laser printer of the present invention which is an optical recording apparatus. Reference numeral 1 denotes a laser module which guides laser light from a semiconductor laser to an optical fiber 2. The plurality of optical fibers are coupled to the corresponding optical waveguide at the input end face 3 of the optical waveguide element 4 already described in FIG. The multi-beams emitted from the optical waveguide elements are converted into parallel lights by the coupling lens 8, and the rotating polygon mirror 9 collectively scans the photosensitive drum with light. Reference numeral 11 denotes a photodetector for detecting the scanning position of the laser beam. Since the interval between the light spot arrays obtained on the photosensitive drum is larger than the size of the light spots, the arrangement direction of the light spot arrays is set to be oblique with respect to the light scanning direction so that close scanning lines are formed. I have to. FIG. 4 is a diagram for explaining that close scanning lines can be obtained by making the light spot array oblique to the scanning direction as described above. However, in the multi-beam device using the optical waveguide device of the present invention, for example, in the above-described device, the arrangement interval of the multi-beam was 10 μm, and the diameter of the emitted beam was 5 μm. In this case, P _S : P ₀ =
1: 2, and the angle at which the light spot row is set obliquely is 3
0 degrees. The value is 13 times larger than that of θ = 2.3 degrees described in the related art. To realize high quality printing, it is necessary to keep the scanning line interval within a predetermined error with high accuracy. However, if it is desired to keep the scanning line interval error within 1%, the oblique angle error is also 1%. It must be: In the case of θ = 2.3 degrees, it is necessary to set the angle with a high precision of 0.023 degrees or less in the element described as the prior art. It will be good. Therefore, high-quality printing without errors in scanning line intervals can be expected. Further, since the multi-beams are arranged at high density, the number of multi-beams can be increased without being affected by the aberration of the optical system, and a high-speed, high-resolution laser printer can be realized. FIG. 8 shows the shape of the optical waveguide 55 on the optical output end side of another optical waveguide element used in the present invention. The optical waveguide 5 is a tapered waveguide having a wide optical waveguide at the light output end face. In this case, the beam propagating in the tapered waveguide spreads in the taper direction, and the emitted beam becomes a beam spread in the multi-beam array direction as indicated by 33. It becomes possible. in this case,
The scanning method shown in FIG. 4B can be performed on the photosensitive drum. That is, even if the arrangement direction of the generated multi-beams is set perpendicular to the scanning direction, the space between the scanning lines is exposed. In this scanning method, all the multi-beams are printed at the same printing timing, and the adjustment of the printing timing between the multi-beams required for the multi-beam oblique scanning becomes unnecessary.
FIG. 9 shows a laser printer optical system using the waveguide element having the waveguide structure shown in FIG. The multi-beam emitted from the multi-beam element is arranged perpendicular to the scanning direction of the rotary polygon mirror, and the light spot array 23 formed on the photosensitive drum is perpendicular to the scanning direction 14. By the way, if there is an error in the production of the optical waveguide element, the width of the beam emitted from the optical waveguide element and the arrangement interval of the multi-beams may not be completely equal. Usually, when the beam width is small, an unexposed portion occurs between the optical scanning lines, which is not preferable. In order to solve this, it is effective to insert a slit 84 for limiting the beam width in the multi-beam arrangement direction at the place where the multi-beams intersect as shown in FIG. That is, by changing the beam width by the width of the slit, the arrangement interval of the multi-beams on the photosensitive drum is unchanged, and the size of the light spot in the direction perpendicular to the scanning direction can be changed. The size of the light spot can be optimized for the arrangement interval. FIG.
FIG. 3 is a diagram for explaining coupling between the optical waveguide on the optical waveguide element and the optical fiber 2. A glass plate 42 having an appropriate thickness is bonded to the upper surface of the substrate 4 of the optical waveguide element. By doing so, the bonding area of the optical fiber becomes large between the end face of the glass plate and the end face 3 of the optical waveguide element, so that the optical fiber can be stably bonded. 24 is a member for holding the optical fiber. The glass plate 6 has already been described with reference to FIG.

[0008]

According to the optical recording apparatus for scanning by using the multi-beam element of the present invention, the arrangement interval of the multi-beams can be narrowed with respect to the size of the light spot on the optical recording material. Less susceptible to optical system aberrations,
In addition, since it is easy to adjust the arrangement interval with high precision, high-quality recording can be performed at high speed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an optical system of an optical recording device including an optical waveguide element according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an optical system of an optical recording device using a conventional optical fiber array element.

FIG. 3 is a cross-sectional view showing optical fibers arranged on a V-groove in a conventional optical fiber array element.

FIG. 4A is a diagram illustrating a scanning method on an optical recording material in which the arrangement direction of the multi-beams is oblique to the scanning direction. FIG. 3B is a diagram illustrating a scanning method in which the arrangement direction of the multi-beams is made perpendicular to the scanning direction on the optical recording material.

FIG. 5 is a perspective view of a multi-beam generating unit used in the optical recording apparatus of the present invention.

FIG. 6A is a diagram showing a structure of an optical waveguide. (B) It is a figure showing the structure of an optical waveguide.

FIG. 7 is a schematic diagram illustrating a structure near an optical output portion of an optical waveguide element used in the optical recording device of the present invention.

FIG. 8 is a schematic diagram showing a case where a tapered optical waveguide near an optical output portion of an optical waveguide element used in the optical recording apparatus of the present invention is used.

FIG. 9 is a schematic diagram showing an optical system of an optical recording apparatus using an optical waveguide element including a tapered optical waveguide according to the present invention.

FIG. 10 is a schematic diagram showing an optical system of an optical recording apparatus including a slit according to the present invention.

FIG. 11 is a schematic diagram illustrating a structure in which an end surface of an optical waveguide element used in the present invention is formed in a cylindrical shape.

FIG. 12 is a schematic diagram illustrating a state of a beam propagating through a glass plate adhered to an end face of an optical waveguide element used in the present invention.

FIG. 13 is a schematic diagram illustrating the coupling between an optical waveguide element and an optical fiber used in the present invention.

[Explanation of symbols]

1: laser module, 2: optical fiber, 3: optical fiber and optical waveguide element joint, 4: optical waveguide element substrate, 5: optical waveguide, 6: flat glass, 8: coupling lens, 9: rotating polygon mirror, 10: scanning lens, 11: photodetector, 13: light spot array, 14: multi-beam for scanning, 17: optical fiber array array, 18: Si substrate with V-groove formed, 2
1: Cladding part of optical fiber, 22: Core part of optical fiber, 19: Glass plate, 20: Adhesive, 13: Row of light spots formed on photosensitive material, 23: Formed on photosensitive material by another method Light spot array, 41: optical waveguide element, 5
1: optical output part of optical waveguide element, 52, 53: optical waveguide, 5
4: cover layer, 31: sectional shape of a beam propagating through the optical waveguide, 32: sectional shape of a beam to be output, 55: tapered waveguide, 33: sectional shape of a beam emitted from the tapered waveguide, 84: slit, 60 : A cylindrical end face of the optical waveguide element; 42: a glass plate adhered on the optical waveguide element.

Claims (3)

[Claims] 1. An optical recording apparatus which emits multi-beams arranged in a row from a multi-beam generating section and scans the optical recording material collectively, wherein the multi-beam generating section includes a plurality of semiconductor lasers and a single mode A plurality of optical fibers for propagating a beam, and an optical waveguide element provided with a plurality of optical waveguides for propagating a single mode beam on a single substrate, and the laser beams emitted from the plurality of semiconductor lasers correspond respectively. The laser light guided to the plurality of optical fibers, the laser light emitted from the optical fiber is input-coupled to the optical waveguide on the corresponding optical waveguide element, and the beam interval of the multi-beam emitted from the optical waveguide element is a plurality of. It is characterized in that it is provided narrower than the distance between the optical fiber and the input connection part of the optical waveguide element, and the width of the optical waveguide on the optical waveguide element is provided in a tapered shape at the optical output part. Optical recording apparatus using a multibeam to. 2. An optical recording apparatus using a multi-beam according to claim 1, wherein a flat glass is attached to an optical output portion of the optical waveguide element. 3. An optical recording apparatus which emits multi-beams arranged in a row from a multi-beam generating section and scans the optical recording material collectively at a position where all the generated multi-beams intersect. 2. An optical recording apparatus using a multi-beam according to claim 1, further comprising a beam shape limiting member for limiting the size of said beam.