JPH11271652A - Optical recorder using multiple beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set scanning line intervals with high precision and to enable printing of high quality by inputting and coupling laser light emitted from an optical fiber with corresponding optical waveguides on optical waveguide elements and making the beam intervals of multiple beams emitted by the optical waveguide elements narrower than the intervals between optical fibers and input coupling parts of of the optical waveguide elements. SOLUTION: A laser module 1 guides the laser light from a semiconductor laser to an optical fiber 2. An optical waveguide element 41 has optical waveguides 5 formed on its plane substrate 4. Optical fibers 2 are led to the optical waveguides 5 of optical waveguide elements 41. The optical fibers 2 are mounted with a holding member such as a ferrule, so the interval between the optical fibers 2 and optical waveguides 5 is about several mm, or large. The optical waveguides of the light input part are curved and reach the optical output part 51. At the optical output part 51, emitted multiple beams are at equal intervals and the optical waveguides 5 are at small equal intervals so that the beam intervals become narrow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser printer which scans and prints a large number of beams emitted from a plurality of semiconductor lasers, that is, a multi-beam.

[0002]

2. Description of the Related Art In order to realize a high-speed laser printer, it is necessary to increase the rotation speed of a rotary polygon mirror to increase the repetition of optical scanning, and to perform optical modulation corresponding to data to be printed. Modulation is needed. A laser printer using a multi-beam is an effective means because the rotation speed of the rotating polygon mirror and the light modulation speed can be reduced by the number of the multi-beams. Need to be more.

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 shape of the clad portion is 125 μm, the diameter of the core portion is 5 μm, and the beam diameter of the laser light propagating through the core portion is also approximately 5 μm.
m. 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, if the interval between light spots is p ₀ ,

[0004]

(Equation 1)

By setting θ to be determined by the relational expression, close scanning lines can be realized. As in the previous example, P _s : p ₀ =
Assuming 1:25, θ = 2.3 degrees is obtained from equation (1). Since the ratio of P _s : p ₀ is small, that is, θ is a small angle because the arrangement interval of the light spots is considerably larger than the size of the light spots. 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. Oblique angle error Δ
The following equation is established from Equation (1) between θ and the scanning line interval error ΔP _S.

[0006]

(Equation 2)

[0007] As the oblique angle θ is smaller, the error of this angle has a greater effect on the deviation of the interval between the scanning lines. For example, when it is desired to suppress the scanning line interval error to within 1%, the oblique angle error needs to be 1% or less. The aforementioned θ = 2.
In the case of 3 degrees, 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.

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. Deterioration of aberration characteristics of system components becomes a problem. That is, the lenses 8, 10 in FIG.
In the case of using multiple beams, it is necessary to use a high-precision beam so that good characteristics can be maintained even for beams far away from the optical axis as compared with the case of using a single beam. Therefore, the laser printer of FIG. 2 cannot increase the number of multi-beams, and there is a limit to high-speed printing.

[0009]

Therefore, according to the present invention, the ratio of the beam interval to the beam diameter of the multi-beam is made small, that is, by generating the multi-beams arranged at high density, the scanning line interval can be set with high accuracy. To achieve 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.

[0010]

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.

The width of the optical waveguide on the optical waveguide element is provided to be narrow in a tapered shape at the optical output part, and a flat glass is attached to the optical output part of the optical waveguide element.
Good results can be obtained even if the light output portion of the optical waveguide element is concave.

In the above-mentioned optical recording apparatus, in the optical recording apparatus in which the multi-beams are emitted from the multi-beam generating section in a row and are collectively scanned on the optical recording material, a place where all the generated multi-beams intersect. Good results can be obtained even if a beam shape limiting member for limiting the size of the beam in the multi-beam arrangement direction is arranged.

[0013]

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. 4
Reference numeral 1 denotes an optical waveguide element, on which a plurality of optical waveguides 5 are formed on a plane substrate 4. The plurality of optical fibers are optical waveguide elements 4
The light is guided to one optical waveguide 5. 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 51
In the above, the optical waveguides are arranged at equal intervals and the intervals are reduced so that the emitted multi-beams are at equal intervals and the beam intervals are narrower. 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. In the embedded type shown in FIG. 6B, 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 a degree 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. That is, since the beam emitted from the waveguide has a size of several μm, if the dust adheres to the end of the waveguide, serious light output deterioration is 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.
FIG. 3 is a diagram for explaining a beam emitted from a waveguide 5 formed on a substrate 4 of the optical waveguide element. 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.

[0014]

(Equation 3)

Here, λ is the wavelength of light. For example, λ
Assuming that = 0.64 μm, d = 5 μm, and a = 1 mm, D = 163 μm from equation (3). That is, an output beam having a size of 5 μm at the end of the optical waveguide is 163 at the end of the glass.
The size is expanded to μm, and the remarkable effects described above can be expected.

FIG. 1 is 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 optical 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 narrow optical waveguide width 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 spreads in the multi-beam arrangement direction as indicated by 33, and the arrangement interval of the multi-beams and the beam size may be set to be substantially equal. It becomes possible. In this case, FIG.
The scanning method (b) becomes possible. 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. In this case, the size of the light spot can be optimized.

FIG. 13 is a view for explaining the 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.

[0019]

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 diagram illustrating a laser printer optical system using a multi-beam generating unit including an optical waveguide element according to the present invention.

FIG. 2 is a diagram showing a conventional laser printer optical system using an optical fiber array element.

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

FIG. 4A is a diagram illustrating a scanning method in which the arrangement direction of the multi-beams is oblique to the scanning direction on the optical recording material. 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 diagram showing a structure of a multi-beam generating unit used in the optical recording device 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 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 diagram showing a case where a tapered optical waveguide near an optical output part of an optical waveguide element used in the optical recording apparatus of the present invention is used.

FIG. 9 is a diagram showing a laser printer optical system using an optical waveguide element including a tapered optical waveguide according to the present invention.

FIG. 10 is a view showing a laser printer optical system including a slit according to the present invention.

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

FIG. 12 is a 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 diagram illustrating 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: light spot array formed on photosensitive material, 23: light spot array, 4
1: optical waveguide element, 51: optical output part of optical waveguide element, 52,
53: optical waveguide, 54: cover layer, 31: cross-sectional shape of beam propagating through the optical waveguide, 32: cross-sectional shape of output beam, 55: tapered waveguide, 33: cross-sectional shape of beam emitted from tapered waveguide, 84 : Slit, 60: cylindrical end face of optical waveguide element, 42: glass plate adhered on optical waveguide element.

Claims (5)

[Claims] 1. An optical recording apparatus which emits a beam from a multi-beam generating section and scans an optical recording material collectively.
The multi-beam generating section is composed of 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 laser beams emitted from the plurality of semiconductor lasers are guided to corresponding optical fibers, and the laser beams emitted from the optical fibers are coupled so as to be input to the optical waveguides on the corresponding optical waveguide elements, An optical recording apparatus using a multi-beam, wherein a beam interval of the multi-beams emitted from the optical waveguide is narrower than a beam interval of a plurality of optical fibers and an input connection portion of the optical waveguide. 2. An optical recording apparatus using a multi-beam according to claim 1, wherein the width of the optical waveguide on the optical waveguide element is tapered and narrow at the optical output portion. 3. The 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. 4. The optical recording apparatus using a multi-beam according to claim 1, wherein the light output section of the optical waveguide element has a concave surface. 5. An optical recording apparatus which emits multi-beams arranged in a row from a multi-beam generating section and scans the optical recording material at a time in an optical recording material. 2. An optical recording apparatus using a multi-beam according to claim 1, wherein a beam shape limiting member for limiting a beam size is arranged.