JPS5848016A - Light scanning optical system - Google Patents

Abstract

PURPOSE:To reduce a pitch between scanning lines by simple and small-sized constitution, by constituting so that a pitch between plural laser luminous fluxes is reduced by use of a prism. CONSTITUTION:Luminous fluxes L1-L4 emitted from plural semiconductor lasers 1 which are arrayed linearly at constant intervals are set to parallel luminous fluxes by spherical lenses 3, 4, pass through a triangular prism 5, and a pitch between the luminous fluxes is reduced. Said parallel luminous fluxes pass through 2 cylindrical lenses 6, 7, are deflected by a rotary polyhedral mirror 8, and are allowed to form an image on the surface of a photosensitive drum 10 through an image formation lens 9. Since it is unnecessary to make the rotary polyhedral mirror 8 large-sized, a pitch between the scanning lines is reduced by simple and small-sized constitution.

Description

[Detailed description of the invention] ＼ Is non-invention a column? A plurality of semiconductor laser output sections arranged in the same manner, a deflection device for completely deflecting the laser beams emitted from these semiconductor laser output sections, and an optical means for guiding the laser beams to the scanning surface at the deflection end? Concerning an original scanning system comprising:

The original scanning optical system of the above type used in an optical recording device such as a laser printer is well known, and this type of scanning optical system can perform multiple scans at the same time using laser beams from multiple semiconductor laser output sections. What are the advantages of this? I have L2. At that time, in order to improve resolution, it is necessary to reduce the pitch between multiple scanning lines that are formed simultaneously (pitch in the sub-scanning direction), but is it possible to reduce the pitch between scanning lines like this? It is difficult in terms of semiconductor laser manufacturing technology to set the pitch distance between each semiconductor laser output section to be small so that the distance between the semiconductor laser output sections can be reduced. From this perspective, columns? Similar to the arrangement of the semiconductor laser output section arranged in the same manner, a structure in which it is tilted from the direction corresponding to the sub-scanning direction when viewed optically has been proposed (Japanese Patent Application Laid-Open No. 15825/1982). . According to this configuration, the pitch between each semiconductor laser output section is maintained relatively large, while the pitch between scanning lines is maintained relatively large. You won't get the advantage of being able to make it smaller.

However, in the configuration according to this proposal, the starting position of scanning by multiple laser beams, for example, using a delay circuit, etc.
Since it is necessary to align the control circuit 5y, there is a disadvantage that the structure of the control circuit 5y becomes complicated. 1. When used in a rotating polygon mirror as a deflection device, there is a drawback that each mirror of the polygon mirror must be made large because the plurality of laser beams arranged in a row r are inclined as a whole. Atsuk.

The purpose of the invention is to reduce the pitch between the scanning lines on the scanning plane, without making the pitch of the semiconductor laser output section so small as to make it difficult to manufacture the semiconductor laser device, and to solve the problem of the above-mentioned conventional drawbacks. It is an object of the present invention to provide a light scanning optical system that can be used in various ways.

The invention is characterized by a structure in which the pitch between a plurality of laser beams is reduced using a prism, and advantageous embodiments of the invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing a specific example of a hole applied to a light scanning optical system according to the present invention and a laser printer.In order to understand the invention, first of all, what is the overall configuration of FIG. 1? explain.

In FIG. 1, a semiconductor laser device is shown having two plurality of semiconductor laser output sections (hereinafter simply referred to as output sections), and these output sections 2 are arranged at a constant pitch P, ? ! - They are arranged in a straight line.

Laser beams Ll s''2, L3, L4 are emitted from each output section 2 with a spread angle Y, and are converted into parallel laser beams by two spherical lenses 3.4, and the principal rays of each laser beam are also These laser beams then pass through a triangular prism 5 and two cylindrical lenses 15, which will be described later, and then a rotating polygon mirror 8.
Constructed as ζ force, the beam spot of each laser beam on the surface of the hole deflector is s,, s,.

83.84 (Figure 3) is the image formation. Incidentally, the laser beam coming out from the output section 2 passes through the spherical lenses 3, 4, the prism 5,
In order to clarify the state in which the cylindrical lens 6.7 passes, FIG. 2(a) shows a side view showing how the two laser beams L111'2 travel, and FIG. 2(b) shows the same state? Each side is schematically shown in the plan view (Fig. 2 (a)
(Only two laser beams IJ1+Tj2 at bJ?
Did you show the diagram? For the sake of clarity, even when there are four laser beams L1 to L4 as in the embodiment shown in FIG. 1, each laser beam proceeds in the same way as in FIGS. 2(a) and (b). (Of course) Since each laser beam shown in FIG. 1 passes through two spherical lenses 3 and 4, the bottom beam spot S in FIG. 3 is placed on the photosensitive drum by the first laser beam L1. , the force formed,
Similarly, beam spots indicated by S2 to S4 are sequentially formed by the second to fourth laser beams L2 to L4.

As is well known, the rotating polygon mirror 8 includes a plurality of 11 mirrors 1 to 1.
Moreover, since it is rotating in the direction shown by the arrow, the mirror 11
Upon reflection, each laser beam is deflected in the direction of arrow A, and main-scans the surface of the photosensitive drum 0 in the direction of arrow X. In this way, multiple main scans are performed at the same time, and the left image is displayed on the drum 1 according to the information signal input to each output section 2 individually.
Force is applied to the surface of 0 sequentially on the expanding surface. At this time, the centers of the scanning lines generated by each laser beam bundle or L4 are shown in FIG. 3 with the symbols "l + B2, B3. L21
The scans performed by L3 + L4 respectively are simply referred to as main scans, and are all the multiple scans performed simultaneously? When you point it out, we will call it Kake group scanning and distinguish between all the points. 1. To simplify the description, the center of the scanning line shown in FIG. , will be simply referred to as a scanning line in the following explanation.

As mentioned above, multiple main scans are performed simultaneously and one group scan? However, this group scanning is performed sequentially for each mirror 11 as the rotating polygon mirror 8 rotates. Since the photosensitive drum 10 is rotating 1-5 in the sub-scanning direction,
A predetermined two-dimensional image is formed on the surface of the drum]0. 12 is a photodetector for generating a synchronization signal to control the input timing of information signals to each output section 2, and the detector 2 detects the start of each group scan in a manner known per se. Press until the position is aligned.

Main scanning and barge group scanning are generally performed as described above.
At that time, high resolution? In order to obtain K, it is necessary to set the pitch P2 between the scanning lines B and 84 on the surface of the photoreceptor drum to a small pitch ζ, and usually, this pitch P2 and
It is preferable that the diameter d of the beam spot is approximately equal to the diameter d of the beam spot. Assuming that the t intensity distribution is a Gaussian distribution, what is the light intensity at the center? As explained earlier, in contrast to the small pitch P2 between scanning lines, the semiconductor laser device Pt of each output section 2 in 1? Setting the pitch Pt'r is difficult due to manufacturing technology, and there is a limit to how small the pitch Pt'r can be. For this reason, the triangular prism 5 described above is used in the present invention, and its details will be explained below.

First, for convenience of explanation, let us assume that the px axis is in the main scanning X direction on the surface of the photoreceptor drum as shown in FIG. 1ilI
] is defined as the sub-scanning direction key y-axis. Then, as clearly shown in FIG. 1, the positions of the semiconductor laser device 1 and other optical elements are also determined by optically corresponding to the The direction of the ZY axis at the position is determined by optically corresponding σ to the xy axis direction on the surface of the photoreceptor drum,
It is clear from FIG. 1 that the x and y axis directions at each position do not necessarily have to coincide spatially). In this way, when the direction is not determined, the arrangement direction of each output section 2 of the semiconductor laser device coincides with the y-axis direction, and the rotation axis of the rotating polygon mirror coincides with the V-axis. And the triangular prism 5 according to the present invention
are arranged in such a manner that the pitch of each laser beam incident on the beam is reduced by 7 in the V-axis direction. That is, the first
As shown in the figures, particularly in Fig. 4, the laser beam flux,
When the first refracting surface 13 of the prism on which the laser beam enters and the second refracting surface 14 of the prism from which the laser beam exits are at right angles to the side surface 15K of the prism 5, this side surface 15 is relative to the V2 plane. It is sufficient to arrange five triangular prisms so that the prisms extend parallel to each other (the z-axis is a direction perpendicular to the X-axis and the V-axis at the position of the first refracting surface 13).

If the five prisms are arranged in this way, the pitch of the laser beams L1 to L4 emitted from the five prisms can be made smaller than the pitch of the laser beams incident on the prism 5, as shown in FIG. It is. To be more specific, the principal optical power α, ? of two adjacent laser beams? +, the incident angle kis of the laser beam onto the first refracting surface 13 of the prism, the exit angle ki' from the first refracting surface 13, and the following relationship cannot be obtained.

[However, 11. : r -5in-t (3111'j-
), and if t*deflection 'iδ, then δ=t-α+5i
n= [n5in (α-1′)]]0 Therefore,
Prism 5 position? By setting the pitches P4 and P3 appropriately (i.e., by appropriately rotating the 5 prisms while keeping them parallel to the side surface 15'?yz plane of the prism 5), the ratio of the pitches P4 and P3 can be set to a desired size. , pitch P4
A smaller predetermined thick awn pitch P3 (i" can be obtained. If the pitch of the laser beam can be reduced in this way r", then the pitch P of the output section 2 of the semiconductor laser) Regardless, the pitch P21 between each scanning line B to 84 on the photosensitive drum 10 can be added to a desired size.

According to the above configuration, since the pitch of the laser beam is reduced using the triangular prism, it is possible to reduce the pitch of the laser beam in the arrangement direction of the output section in the semiconductor laser device, unlike the configuration related to the conventional proposal. It is possible to set the pitch P2 between scanning lines on the photoreceptor drum to a desired small pitch without tilting the scanning line with respect to the y-axis. Therefore, each laser beam “I +”2 +”fi +”4
Accordingly, the positions of the beam spots formed on the photosensitive drum can be aligned in the y-axis direction (sub-scanning direction) as shown in FIG. Is this a complicated method like a delay circuit? There is no need to align the start positions of the main scans in each group scan using this method. In other words, when one group scan is performed, a plurality of laser beams, , L2
．． L5. It is not necessary to perform control such as detecting each of L individually by the photodetector 12 and aligning the start positions of each main scan, but it is possible to perform seven optical scans using the [] detector 12 with the [ ] laser beam. The start position of each group scan is determined by light detection by the left detector 2, in exactly the same manner as the scan start control which is well known per se. It is enough just to arrange them.

Contrary to this, if the pitch of the laser beam is reduced by tilting the arrangement of the output section 2 at an angle of 6 with respect to the ku-axis direction, the pitch of the laser beam can be reduced, as shown in FIG. Then, the beam spot can be formed,
A complicated circuit is required to align the start positions of each main scan. Not only the arrangement direction of output section 2? If it is tilted, the cylindrical lens 6.7 must also be tilted ζ to accommodate the stiffness, which makes positioning the lenses 6.7 troublesome. This is not necessary at all, and therefore the configuration of the optical system can be simplified. ′=! Therefore, there is no need to particularly increase the size of the rotating polygon mirror as in the prior art.Are there any advantageous embodiments of the present invention? Description L-fc7'', the present invention is not limited to the above configuration, and it goes without saying that various modifications can be made. For example, in the embodiment shown in FIG. Parallel state [
L-After that, this? Make it incident on prism 5 2
k is the diverging laser beam as shown schematically in Figure 6? It is also possible to make the light directly enter the housing prism 5.

However, in this case, as can be seen from FIG. 6, the incident angle of the peripheral rays 18 and 19 of each laser beam I'S and L2 on the prism 5 is G+'2, and therefore the output angle is '3+'.
4 are different from each other ('+ ”': 't + '
To s i4), the cross-sectional shape of the laser beam is deformed when the laser beam is emitted from the five prisms, and a difference occurs in the optical path length within the prism 5 in each laser beam LH, L2.
The cross-sectional shape (dimensions) of each laser beam will change, and there is a possibility that it will not be possible to produce a beam spot of the same shape on the photoreceptor drum. In this regard, in the configuration shown in FIG. 1, the cross-sectional shapes of the external laser beams emitted from the five prisms are all the same, and therefore the shapes of the beam spots on the photoreceptor drum are also all constant.
In this sense, it can be said that the configuration shown in FIG. 1 is superior to the configuration shown in FIG. 6. Further, as the triangular prism, a prism having an appropriate shape other than the one shown in FIG. 1, for example, the η-shaped prism 5 shown in FIG. 7, can also be used.

The angle of incidence of the laser beam onto the prism 5 can also be set appropriately, and FIG. 7 shows the case where this angle of incidence is 00? It shows. It is possible to provide five 1'fc prisms at appropriate positions from the output section 2 to the photoreceptor drum 101, but are these prisms installed after the deflection device? Do I need to install a prism to deflect the laser beam? Since it is not easy to configure in this way, the output section 2 and
A prism 5 should be placed between the deflection device and the deflection device. Also, the number of prisms is not limited to one, but multiple prisms as necessary? It can also be used.

Furthermore, the configuration shown in FIG. 1 can be modified as appropriate within the scope obvious to those skilled in the art. For example, as shown in FIG. 1, the cylindrical lens 6.7 shapes the cross-sectional shape of the laser beam,
Beam spot of desired shape? Although the function is to form an image on the photosensitive drum, an appropriate light beam shape shaping means other than the lens 6.7, such as a hologram lens or a prism, may be used, and in some cases, such a light beam shape shaping means may be used. It is also possible to omit the beam shape shaping means (in addition,
For reference, FIG. 1 shows the cross-sectional shape of one laser beam in each device I to (2) in the optical path. , code 20,2
1.21 is attached, and as you can see,
The cross-sectional shape of the laser beam is reduced only in the X-axis direction by the illustrated cylindrical lens 6.7, and in this case, the pitch between the laser beams is enlarged by the cylindrical lenses 6, 7IL while being reduced by the prism 5. Never).

1 is also a hologram scanner, AO instead of a rotating polygon mirror 8.
A left-handed optical system using a polarizing device consisting of a resistor or a galvano mirror φλ, a beam compressor or a beam expander, etc. interposed in the optical path of the laser beam, or a fc optical system, or a belt-like or sheet-like photoreceptor. Even in universities that have
The present invention can be advantageously applied. It goes without saying that the number of output units 2 is not limited to four, but can be set to an appropriate number.

[Brief explanation of the drawing]

FIG. 1 shows a laser 7'I including a scanning round type laser according to the present invention.
A schematic perspective view of the interface, Figure 2 (a) shows the progress state of the laser beam? The explanatory side view, FIG. 2(b), is the same as FIG. 2(a).
), FIG. 3 is an explanatory diagram schematically showing the beam spot formed on the photoreceptor drum, FIG. 4 is an explanatory diagram showing the state in which the pitch of the leopard beam is reduced using the prism, and FIG. 5 is an explanatory diagram showing the conventional beam spot. The scanning optical system forms an image on the photoreceptor drum, and the beam is focused on the drum. Other forms of prism? FIG. 2... Output section 5... Prisms Ll to L4... Laser beam P3. P... Pitch procedure amendment (voluntary) December 17, 1980 Director of the Japan Patent Office Kazuo Wakasugi 1 Display of the case 1983 Patent Application No. 146077 2 Name of the invention Light scanning optical system 3 Correction Relationship with the case of the person who filed the patent application Address of the patent applicant: 1-3-6 Nakamagome, Ota-ku, Tokyo Name (67
4) Ricoh Co., Ltd. 4 Agent 105 Address 3, Chugin 5th Hill, 1-9-9 Nishi-Shinbashi, Minato-ku, Tokyo
Floor Ta (501) No. 4887 (1) Claims column of the specification (2) Detailed explanation of the invention column 6 Contents of amendment (1) Percentage The scope of claims is amended as per the attached sheet. do. (2) ``1 inclusion'' on page 2, line 8 of the specification is amended to ``equipment.'' (3) "Reduction" in the last line of page 3, 2 lines from the bottom of page 8, line 9 of page 10, and line 15 of page 10 will be corrected to "reduction by 1". (4) On page 4, lines 13 and 14, “As it happens...
made parallel. ” is corrected to “will be.” (5) Page 9, lines 12 to 13 and page 12, line 16
Correct the "principal ray" in rows to rows 17 to "ray passing through the center." Attachment [2 Claims (1) A plurality of semiconductor laser output sections arranged in a row, a deflection device for deflecting laser beams emitted from these semiconductor laser output sections, and a deflected laser beam In the optical scanning optical system, a prism is provided between the semiconductor laser output section and the deflection device, and a plurality of semiconductor laser output sections emit light to the prism. The optical scanning optical system is characterized in that the prism is positioned so that the pinch between the laser beams exiting the prism can be made smaller than the pitch between the laser beams entering the prism. (2) Claim 1, characterized in that the prism is provided with an optical element that converts the laser beam into a parallel beam, and the prism is arranged at a position where the laser beam made parallel by the optical element can be incident. The optical scanning optical system described in . ”

Claims (2)

[Claims] (1) A plurality of semiconductor laser output units arranged in a row, a deflection device for completely deflecting the laser beams emitted from these semiconductor laser output units, and a deflection angle for guiding the laser beams to the scanning plane. With optical means? In the optical scanning optical system, a prism is provided between the semiconductor laser output section and the deflection device, and the pitch between the laser beams emitted from the plurality of semiconductor laser output sections and incident on the prism is , the prism is designed so that the pitch between the emitted laser beams can be reduced. The light scanning optical system is characterized by positioning. (2) Laser beam? Optical element for parallel light flux? Is the prism placed at a position where the laser beam can be incident without being parallelized by the optical element? The original scanning system according to claim 1, characterized in that: