JP2002287071A - Optical scanning method and optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanning method which can make an optical scanning system small-sized and save its energy and to provide an optical scanner which can be made small-sized and saves the energy by using the optical scanning method. SOLUTION: The optical scanning method which deflects the light beam from a light source for scanning by reflecting surfaces 2 to 7 rotated and moved by a rotor uses narrow-band light interfering reflecting films as the reflecting surfaces. Further, the narrow-band light-interfering reflecting films are stacked and constituted as mutually parallel reflecting surfaces. Further, the reflecting surfaces 2 to 7 made of the light-interfernig reflecting films are arrayed radially around the center O of rotation of the rotor 1. Consequently, the rotor can be made small-sized and reduced in tare and the optical scanning system can be made small-sized and reduced in energy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent image writing section of an image forming apparatus such as a laser printer and a digital copying machine, an optical scanning display, an optical scanning projector, and the like.
The present invention relates to an optical scanning method and an optical scanner applicable to devices having an optical scanning system such as a bar code reader and a digital theater.

[0002]

2. Description of the Related Art As represented by a laser printer, a polygon mirror (usually called a polygon mirror or a rotating polygon mirror) rotated by a motor is used to scan a light beam from a light source. Although widely used, as the total energy of devices incorporating the polygon mirror is reduced, there is a demand for miniaturization and energy saving of the optical scanning system. Although the energy consumed by the polygon mirror also depends on the rotation speed, most of the energy is frictional energy between the polygon mirror and surrounding air, which is called windage. One measure that has been used to reduce this is to reduce the thickness of the polygon mirror. However, the thickness of the polygon mirror has a lower limit from the required diameter required for the light beam. Therefore, in order to avoid this, the light beam is deformed into an elliptical shape, and a device has been devised so that the minor axis is directed in the thickness direction of the polygon mirror. The next largest energy consumption is the friction energy of the bearing that rotates the polygon mirror. Although this has a long history, air bearings have recently come into practical use from conventional ball bearings.

[0003]

FIG. 7 is an explanatory view of a hexagonal prism-shaped polygon mirror (rotating polygon mirror) showing an example of a conventional optical scanner, and is incident on a polygon mirror 11 and one of its mirror surfaces. The cross-sectional shapes of the incident beams are shown, and the cross-sections of the two incident beams are shown by two circles. The two beam positions indicate that the polygon mirror 11 has moved as it rotates, and the angle between the two beams from the rotation center O of the polygon mirror is α.
In this case, the angle formed by one surface of the polygon mirror 11 with the center is 60 degrees (∠aOb). In the polygon mirror 11, the light beam is reflected by the six outer mirror surfaces, and the light beam is scanned as the polygon mirror 11 rotates. Since the mirror surface of the polygon mirror 11 is shifted from the center of the hexagonal prism, the polygon mirror 1
With the rotation of 1, the incident position of the light beam shifts. Since all of this light beam is used for drawing by optical scanning,
It is not desirable to protrude from one mirror surface during writing. Therefore, in the case of a hexagonal prism shape as shown in FIG. 7, while the polygon mirror 11 rotates by 60 degrees (∠AO
B) Despite the light beam being incident on the same surface,
Only the part of the angle α (∠aOb) where all the beam bundle cross sections can be used can be used for writing. This is because the ratio of effective irradiation decreases as the mirror area becomes relatively smaller than the light beam, so that miniaturization of the optical system causes a decrease in efficiency. That is, a decrease in the diameter is not preferable.

Another more serious problem is that the polygon mirror system cannot be miniaturized because the size (length) of the side of the polygonal prism is required to some extent for the above-mentioned reason. For this reason, the loss due to friction between the polygon mirror and the air (usually called windage loss) is large, and most of the rotational energy of the polygon mirror has been taken away by the windage loss. It is known that energy commonly referred to as windage increases to the nth power of the radius of rotation (n> 2), the square of the number of rotations, and in proportion to the thickness of the polygon mirror. Therefore, reducing the radius (diameter) of the polygon mirror is a major issue from this viewpoint.

The rotational energy consumed mainly by windage has not been a major problem in the past. The reason is that such an optical scanning system is used as one component of a large energy consumption system such as a printer, and is largely inconspicuous. However, in recent years, energy saving has been addressed from two directions. One of them is
This is a reduction in friction of a bearing of a rotor such as a polygon mirror. This is changing from a conventional ball bearing to an air bearing to a less resistive system. The second approach is to reduce resistance to surrounding air, that is, windage loss, due to rotation of a rotor such as a polygon mirror. To reduce the diameter of the rotor, a measure was taken. Since windage is said to be proportional to the fourth power of the prism diameter, the energy saving effect by reducing the diameter is large. However, the inscribed diameter of the prismatic rotor is still about 30 mm in diameter, which is the minimum practical diameter. Another approach is to use multiple beams. This suppresses an increase in the number of rotations of the rotor by increasing the number of light beams to be irradiated to two or four. Since the windage is proportional to the square of the number of revolutions, this method is an effective means currently in practical use. Yet another approach is to reduce the thickness of the polygon mirror. That is, the air resistance is reduced by reducing the thickness of the polygon mirror. In addition, there is also a proposal for multi-layer processing of a mirror of an optical scanner to improve reflection efficiency (Japanese Patent Laid-Open No. Hei 6-30840).
No. 7).

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel optical scanning system capable of reducing the size and energy saving of an optical scanning system, and to further reduce the size and energy consumption by using the optical scanning system. An object of the present invention is to provide an optical scanner having a novel configuration that can be achieved.

[0007]

In order to achieve the above object, according to the present invention, there is provided an optical scanning system in which a light beam from a light source is deflected and scanned by a plurality of reflecting surfaces rotating and moving by a rotor. The present invention is characterized in that a narrow-band light coherent reflection film is used as the reflection surface. According to a second aspect of the present invention, in the optical scanning system according to the first aspect, a plurality of narrow-band optical coherent reflective films are overlapped and configured as reflective surfaces parallel to each other. . The invention according to claim 3 is the invention according to claim 1.
Alternatively, in the optical scanning method described in Item 2, a plurality of reflection surfaces made of an optical interference reflection film are radially arranged from a rotation center of the rotor.

According to a fourth aspect of the present invention, in the optical scanning system according to the first, second or third aspect, the scanning light beam is incident toward the center of the rotor. According to a fifth aspect of the present invention, in the optical scanning method according to the third aspect, an angle between adjacent light interference reflective films is set to α.
In this case, the effective reflection angle width of the reflected beam from the reflection film is effectively reflected on both sides of the normal incidence by an angle width of approximately 1-cos (α / 2).

According to a sixth aspect of the present invention, in the optical scanning system according to any one of the first to fifth aspects, the narrow band light interference reflective film constituting the reflecting surface is formed by alternate layers of a transparent substance. It is characterized by being formed by. According to a seventh aspect of the present invention, in the optical scanning system according to any one of the first to fifth aspects, the narrow band light interference reflective film constituting the reflective surface is formed by alternately forming a transparent gap layer and glass. It is characterized by being formed by a layer. According to an eighth aspect of the present invention, in the optical scanning system according to any one of the first to fifth aspects, the narrow-band light interference reflective film constituting the reflective surface is embedded in a transparent disk-shaped substrate. It is characterized by the following.

According to a ninth aspect of the present invention, in the optical scanning system according to any one of the first to eighth aspects, both sides of the narrow-band optical coherent reflection film constituting the reflection surface can be used for optical scanning. It is characterized by the following. According to a tenth aspect of the present invention, in the optical scanning system according to the third aspect, one or more types of multilayer thin film plane mirrors having a cutout in a part of a plane mirror having a reflection surface made of an optical interference reflection film. Are combined with each other and arranged at equal angles radially from the same center to constitute an optical scanning rotor.

The invention according to claim 11 is the invention according to claims 1 to 10
In the optical scanning method according to any one of the above, the incident light beam, or the reflected light beam, for the purpose of preventing astigmatism due to the transparent substrate constituting the rotor, the optical system has an astigmatism correction function. It is characterized by having. According to a twelfth aspect of the present invention, in the optical scanning system according to any one of the first to eleventh aspects, the reflecting surface made of the light interference reflective film is formed of a low-refractive-index single crystal or a polycrystal (for example, a fluororesin). (A single crystal or polycrystal of lithium chloride). According to a thirteenth aspect of the present invention, in the optical scanning method according to any one of the first to eleventh aspects, a rotor surface made of a transparent substrate in which a reflection surface made of an optical coherent reflection film is embedded has a rotationally symmetric system ( For example,
(Cylindrical).

According to a fourteenth aspect of the present invention, there is provided an optical scanner for deflecting and scanning a light beam from a light source by a plurality of reflecting surfaces rotated by a rotor. The optical scanning method described above is used.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration, operation and operation of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing an example of the configuration of an optical scanner using the optical scanning method of the present invention, and is a schematic cross-sectional view of the optical deflector viewed from the direction of the rotation center axis O. The light deflector 1 has a plane reflecting mirror (which is an optical interference type) that uses a narrow-band light coherent reflecting film that completely reflects incident light only in a specific angle range and becomes transparent at other angles as a reflecting surface. 2,3,4)
This is an optical scanning rotor in which 5, 6, and 7 are arranged radially from the rotation center of the rotor, and a light beam from a light source (not shown) is incident on the center O of the optical scanning rotor 1. Then, by rotating the optical scanning rotor 1 by a motor (not shown), the reflected light is deflected and scanned by each of the optical interference type reflecting mirrors 2 to 7.

Next, the optical scanning method and configuration of the optical scanner according to the present invention will be described in detail. Fig. 2 shows an optical deflector
FIG. 4 is a diagram comparing a conventional polygon mirror with an optical scanning rotor according to the present invention, and schematically shows how an incident light beam bundle is reflected by two differently shaped optical scanners. FIG. 2A shows a conventional polygon mirror 11 having a polygonal prism shape, and the entire polygon mirror is many times larger than the bundle of incident beams. FIG. 2B shows an optical scanning rotor 1 using the optical interference type reflecting mirror of the present invention, which has a rotating portion having a diameter substantially equal to the bundle of incident beams. That is, in FIG. 2, the widths of the arrows indicate the widths of the incident light beam and the reflected light beam, and intuitively, the diameter of the optical scanning rotor 1 using the light interference type reflecting mirror of the present invention as compared with the polygon mirror 11. Is dramatically reduced. FIG.
In (b), it can be inferred that a rotor having substantially the diameter of the light beam is sufficient. Further, since the air resistance increases in proportion to the fourth power of the rotor diameter, if the optical scanning rotor 1 shown in FIG. 2B can be realized, the windage loss can be considerably reduced, and the effect is immeasurable.

Next, FIG. 3 is a view for explaining the operation of the optical scanning rotor 1 having the six light interference type reflecting mirrors 2 to 7 similar to FIG. In FIG. 3, A and B are incident lights from two directions, and a and b are reflected lights corresponding to each. The light coherent reflection film forming the reflection surface is formed of a multilayer film and reflects light (monochromatic light) only in a specific direction. In this case, only light from a direction close to the vertical is reflected, and the others are transmitted.
Further, the multilayer film constituting the light interference reflective film has almost the same characteristics on the front and back sides. Therefore, two optical scans by the front surface and the back surface can be performed while one light interference reflective film makes one rotation. In the example of the optical scanning rotor 1, six optical interference type reflecting mirrors each composed of an optical interference reflective film are radially arranged, so that 12 scans can be performed during one rotation of the optical scanning rotor 1. It is. Therefore, the number of rotations can be reduced to half compared with the conventional hexagonal prism-shaped polygon mirror, and the windage loss and the like can be further reduced and energy can be saved.

FIG. 4 shows an example of a multilayer film used as an optical coherent reflection film constituting a reflection surface of the optical scanning rotor according to the present invention. 6 is a graph of calculated values showing the principle of a filter having a property (wavelength selective reflection film). It is known that a reflective film having high wavelength selectivity can be obtained by stacking two types of transparent substances having different refractive indices over multiple layers.
A reflective film having an arbitrary band and an arbitrary wavelength width can be designed. In FIG. 4, a high refractive index on a transparent substrate (n _S = 1.52) as a function of the wavelength λ for a phase thickness δ = 2πnd / λ (upper scale) or λ ₀ = 460 nm (lower scale). Index (n _H = 1.52) and low refractive index (n _L =
1.38) shows the calculated values of reflectance R ₀ for normal incidence lambda _0/4 alternating layers of dielectric material. The number of layers is
Shown as curve parameters.

Conventionally known multilayer reflective (or non-reflective) coating films have strong wavelength selectivity. In the past, efforts have been made to eliminate this wavelength selectivity, but here, it is actively utilized. Now, if there is a light interference type reflection film designed to completely reflect light incident from the front with respect to a specific wavelength λ, the light is completely reflected only at an angle of θ before and after, and the others are transmitted. In FIG. 4, the phase of FIG. 4 can be adjusted so as to “perfectly reflect at wavelengths between λ and λ (1−cos θ)”. In FIG. 4, the width g of the reflectance graph is given by the following equation (HAMacleod, Thin-Film Optical Filtration).
ters; Ogura et al., Optical Thin Film; Nikkan Kogyo Shimbun, 1989). δ = (π / 2) ( λ 0 / λ) ≡ (π / 2) g where the optical thin film is when as a lambda _0/4, a light wavelength lambda is of interest. The bandwidth of the wavelength Delta] g can be expressed by Δg = (2 / π) sin -1 {(n H -n L) / (n H + n L)}. Here, n _H and n _L are the respective transparent films (high-refractive-index film, low-refractive-index film) forming the alternating layers as described above.
Is the refractive index of As described above, if light scanning is performed 12 times by the six light interference type reflection mirrors during one rotation of the light scanning rotor 1 (two reflections on the front and back sides), the angle between the reflection films is 30 degrees. Therefore, from the relationship of cos 15 ° = 0.94, a 2Δg = 0.06, i.e., 0.03 × (π / 2) = sin -1 {(n H -n L) / (n H + n
_L) a}, _{i.e., {(n H -n L)} / (n H + n L)} = 0.047 is obtained. From this, n _H / n _L = 1.098 is obtained.

A combination of transparent materials having such a refractive index ratio can be easily found. In general, there are various combinations of transparent substances having a similar refractive index, including optical glass. Such alternating layers of transparent materials having different refractive indices are also effective in the following special cases. That is, although the refractive index of glass changes depending on the composition of a trace component represented by the alkali oxide element,
Such a configuration can be achieved by adding a trace component in a layered manner. Further, by providing a gap instead of mixing the substance, the refractive index can be changed. It is also possible to form a multi-layered film by forming a large number of pore layers in a glass substrate, or by depositing low-density glass known as porous silica.

Although the light coherent reflection film in the present invention is intended for monochromatic light, by narrowing the bandwidth of the light coherence reflection film, R (red), G (green), and B (blue) are reduced. It is possible to superimpose the light interference reflective films of three colors. For example, as shown in FIG. 5, when multilayer films A, B, and C having narrow bandwidths corresponding to three colors of R (red), G (green), and B (blue) are overlapped, the same scanning optical system becomes Effective for color beams. Moreover, the same effect can be obtained on the front side and the back side. In other words, one reflection film can execute optical scanning twice during one rotation. FIG. 5 shows an example of three types of multilayer films in a transparent substrate constituting an optical interference type mirror, and a narrow band multilayer reflection film (A, B, C) adapted to three types of wavelengths. (3 types) are superimposed and embedded in a transparent substrate to constitute one of the blades (optical interference mirror) of the optical scanning rotor. The multilayer reflective film is held in a substrate made of a transparent material. As will be described later, a transparent material of this substrate having a low refractive index is more suitable for optical scanning.

In mounting, it is easiest to fabricate a light interference type reflection mirror by embedding a light interference reflection film composed of a multilayer reflection film in a transparent substrate (such as glass).
When the light interference type reflection mirror provided with the light interference reflection film is mounted in an impeller-like cylindrical rotor, the planar accuracy of the reflection film is important. FIG. 6 shows a component shape of an optical interference type mirror provided with a multilayer reflective film and a mounting method thereof. FIG. 6 (a)
Fig. 6 shows three types of plane mirror parts 8, 9, and 10 having different shapes, which are light interference type reflection mirrors, and Fig. 6B shows an assembled state thereof. In FIG. 6B, of the three types of plane mirror parts 8, 9, and 10, two plane mirror parts 8, 9 are used.
It shows a state where they cross each other at a central portion O. Since the thickness of each plane mirror part is sufficiently thin, two sets of these three kinds of plane mirror parts 8, 9, and 10 are prepared (a total of six pieces are prepared), and two sets of plane mirrors 8, 9, and 10 are alternately combined. This makes it possible to form an impeller-shaped optical scanning rotor (FIG. 1) having a high plane accuracy, in which the six elements intersect at one point substantially at the center.

Although the individual elements have been described above, finally, the following considerations are required when describing the entire optical scanning optical system. The above-described six-piece light interference type reflecting mirror has:
It is easy to make a configuration that is embedded in a disk-shaped transparent substrate.
Further, it is desirable that the surface of the rotor made of a transparent substrate in which the light interference type reflection mirror is embedded be made rotationally symmetric (for example, cylindrical). In the case of a configuration in which the light interference type reflection mirror is embedded in a cylindrical transparent substrate, incident light may be refracted by the transparent substrate and cause astigmatism. But,
This is not necessary if the transparent substrate has a refractive index of 1. As an example, lithium fluoride (L
iF) can be used. As is well known, this material has a refractive index of 1.1 and can minimize the effects of astigmatism. In the case of a substance having a large astigmatism, various correction optical systems similar to those of a normal laser printer are required to prevent this, but the details will not be described here. These considerations
This is because the correction system can be designed if the person has ordinary optical design knowledge.

The optical scanning system according to the present invention enables a light beam to be scanned by a small scanning system, and is not limited to a latent image writing device of an image forming apparatus such as a laser printer or a digital copying machine. Needless to say, it can be applied to a wide range of products. For example, an optical scanning display, an optical scanning projector, a barcode reader,
The present invention can be applied to a device having an optical scanning system such as a digital theater without changing the basic concept.

[0023]

As described above, according to the present invention,
The method uses a conventional polygon mirror because it uses an optical interference mirror that uses a narrow-band optical interference reflective film as the reflection surface, and uses an optical scanning rotor that arranges multiple optical interference mirrors radially. It is possible to realize an optical scanning system that is smaller in size and can reduce windage loss, and that can reduce the size of the optical scanning system and save energy. Further, it is possible to provide an optical scanner which achieves miniaturization and energy saving by using the optical scanning method.

[Brief description of the drawings]

FIG. 1 is a diagram showing one configuration example of an optical scanner using an optical scanning method according to the present invention, and is a schematic sectional view of an optical deflector as viewed from a direction of a rotation center axis.

FIG. 2 is a diagram comparing a conventional polygon mirror and an optical scanning rotor according to the present invention as an optical deflector, and schematically shows how an incident light beam is reflected by two differently shaped optical scanners. FIG.

FIG. 3 is an operation explanatory view of an optical scanning rotor having six light interference type reflecting mirrors similar to FIG. 1;

FIG. 4 shows an example of a multilayer film used for the light interference reflective film according to the present invention, in which a filter having a specific wavelength selectivity is provided by alternate layers of transparent thin films (wavelength selective reflective film).
Is a graph of calculated values showing the principle of

FIG. 5 is a view showing an example of three types of multilayer films in a transparent substrate constituting a light interference type reflection mirror.

FIG. 6 is a diagram showing a component shape of an optical interference type reflection mirror provided with a multilayer reflection film and a mounting method thereof.

FIG. 7 is an explanatory view of a hexagonal prism-shaped polygon mirror (rotating polygon mirror) showing an example of a conventional optical scanner.

[Explanation of symbols]

 1: Optical scanning rotor (optical scanner) 2, 3, 4, 5, 6, 7: Optical interference type reflection mirror 8, 9, 10: Planar mirror parts

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiharu Murai 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor Hiroyoshi Funato 1-3-6 Nakamagome, Ota-ku, Tokyo・ F-term in Ricoh Co., Ltd. (reference) 2C362 AA42 AA48 BA05 BA06 BA83 BA90 DA08 EA24 2H045 AA02 AA03 AA06 5C072 AA03 CA06 DA04 HA02 HA13 XA01 XA05

Claims (14)

[Claims] 1. A light scanning system in which a light beam from a light source is deflected and scanned by a plurality of reflecting surfaces rotated and moved by a rotor, wherein a narrow-band light coherent reflecting film is used as the reflecting surface. Optical scanning method. 2. An optical scanning system according to claim 1, wherein a plurality of narrow-band optical coherent reflection films are overlapped and formed as reflection surfaces parallel to each other. 3. The optical scanning method according to claim 1, wherein a plurality of reflection surfaces made of an optical interference reflection film are arranged radially from a rotation center of the rotor. 4. The optical scanning method according to claim 1, wherein the scanning light beam is incident toward the center of the rotor. 5. The optical scanning system according to claim 3, wherein when an angle between adjacent light interference reflective films is α, an effective reflection angle width of a reflected beam from the reflective film is set on both sides of normal incidence. An optical scanning method characterized by effectively reflecting an angular width of approximately 1-cos (α / 2). 6. The optical scanning method according to claim 1, wherein the narrow-band light coherent reflection film constituting the reflection surface is formed by alternate layers of transparent substances. Optical scanning method. 7. The optical scanning method according to claim 1, wherein the narrow-band light coherent reflection film constituting the reflection surface is formed by an alternate layer of a transparent gap layer and glass. An optical scanning method. 8. The optical scanning system according to claim 1, wherein the narrow-band light coherent reflection film constituting the reflection surface is embedded in a transparent disk-shaped substrate. Optical scanning method. 9. The optical scanning method according to claim 1, wherein both sides of the narrow-band light coherent reflection film forming the reflection surface can be used for optical scanning. method. 10. An optical scanning system according to claim 3, wherein one or more kinds of multilayer thin film plane mirrors each having a cutout in a part of a plane mirror having a reflection surface made of an optical interference reflection film are combined with each other. An optical scanning method, wherein an optical scanning rotor is constituted by arranging radially equal angles from the same center. 11. An optical scanning system according to claim 1, wherein the incident light beam or the reflected light beam is provided for preventing astigmatism caused by a transparent substrate constituting a rotor. An optical scanning method characterized in that the optical system has an astigmatism correction function. 12. The optical scanning method according to claim 1, wherein the reflection surface formed of the light interference reflection film is embedded in a single crystal or polycrystal having a low refractive index. Optical scanning method. 13. The optical scanning method according to claim 1, wherein the rotor surface made of a transparent substrate in which a reflection surface made of a light interference reflection film is embedded is made to be a rotationally symmetric system. Characteristic optical scanning method. 14. An optical scanner for deflecting and scanning a light beam from a light source by a plurality of reflection surfaces rotated and moved by a rotor, wherein the optical scanning method according to claim 1 is used. An optical scanner.