JP2016033529A - Light transmissive member for cover of optical deflector, optical deflector, optical lens and optical mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light transmissive member for cover of an optical deflector, which reduces speckle of laser light without increasing the number of optical elements arranged on an optical path.SOLUTION: An optical deflector 1 scans the reflection direction of laser light made incident to a mirror part 11 by oscillating the mirror part 11. A light transmissive member 5 for cover is mounted to the optical deflector 1. In the light transmissive member 5 for cover, on the surface of a portion making incident light and reflection light to the mirror part 11 penetrate, a speckle elimination pattern 17 is formed so that a sub-wavelength structure area, which has grooves arrayed repeatedly at a cycle shorter than the wavelength of used light and has structural birefringent, is arranged so as to have a portion where optical axis directions to be the array directions of the grooves are different from each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light transmissive member for an optical deflector cover, an optical deflector, an optical lens, and an optical mirror.

  In recent years, laser displays using laser light as a light source have attracted attention as next-generation displays. Laser displays, for example, have lower power consumption, ultra-compact (thin and light), low cost, focus-free, and beautiful images than lamp-based displays, and expectations for laser displays are increasing. .

  In addition to the light source, the laser display includes an optical deflector that scans the reflection direction of the laser light incident on the mirror unit by vibrating the mirror unit. The optical deflector is a device that emits laser light to a target range or an object existing within a predetermined range by continuously reflecting the laser light emitted from the light source at a predetermined angle. The optical deflector is also called a laser scanning device. As an optical deflector, for example, a scanning mirror (MEMS mirror) using MEMS (Micro Electro Mechanical Systems), a polygon mirror (rotating polygon mirror), and the like are known.

  However, the laser display has a problem of speckle noise, which is difficult to realize. Speckle noise is generated when light scattered from fine irregularities on the screen causes interference. Until now, an effective prevention method and reduction method for speckle noise has not been established.

  As one effective solution for eliminating speckle noise, it is known that speckle can be reduced by dividing and arranging a pattern for modulating an optical axis in a region to eliminate polarization ( For example, see Patent Documents 1 and 2.)

JP 2004-341453 A JP 2011-180581 A JP 2003-57586 A JP 2011-180581 A JP 2006-133605 A

  The speckle eliminating element is disposed on the optical path. Therefore, the speckle eliminating element sometimes causes a space problem of the optical system. Such a problem occurs not only in an optical system of a laser display but also in an entire optical system using laser light as a light source.

  An object of the present invention is to reduce the pecking of a laser beam without increasing the number of optical elements arranged on the optical path.

  The cover light-transmitting member of the optical deflector according to the present invention is a cover light-transmitting member mounted on the light deflector that scans the reflection direction of the laser light incident on the mirror unit by operating the mirror unit. The sub-wavelength structure region exhibiting structural birefringence having grooves arranged repeatedly on the surface of the mirror portion where the reflected light is transmitted with a period shorter than the wavelength of the light to be used is the groove. The speckle elimination pattern is formed in such a manner that the optical axis directions which are the arrangement directions are arranged so as to have portions different from each other.

  An optical deflector according to the present invention is an optical deflector that scans a reflection direction of a laser beam incident on the mirror unit by vibrating the mirror unit, and is on an optical path of incident light and reflected light on the mirror unit. The light deflector cover light transmissive member of the present invention is provided.

  The optical lens according to the present invention has a sub-wavelength exhibiting structural birefringence having grooves arranged repeatedly on the surface of a lens portion made of a light-transmitting member having a lens function at a cycle shorter than the wavelength of light to be used. A speckle elimination pattern is formed in which the structure regions are arranged so that the optical axis directions, which are the arrangement directions of the grooves, have different portions from each other.

  In the optical mirror according to the present invention, the sub-wavelength structure region exhibiting structural birefringence having grooves arranged repeatedly on the surface of the light reflecting surface of the light reflecting member at a cycle shorter than the wavelength of the light to be used is described above. A speckle elimination pattern is formed in which the optical axis directions, which are the arrangement direction of the grooves, are arranged so as to have different portions.

  The light transmissive member, the optical deflector, the optical lens, and the optical mirror for the cover of the optical deflector according to the present invention can reduce the pecking of the laser beam without increasing the number of optical elements arranged on the optical path. it can.

It is the schematic for demonstrating one Example of an optical deflector, (A) is a top view, (B) is sectional drawing. It is a schematic plan view which shows the light transmissive member for a cover of the Example. It is a schematic top view which shows the optical deflector main-body part of the Example. It is a schematic sectional view for explaining another embodiment of the light transmissive member for cover and another embodiment of the optical deflector. FIG. 6 is a schematic cross-sectional view for explaining still another embodiment of the light transmitting member for cover and still another embodiment of the optical deflector. It is a schematic sectional view for explaining a subwavelength structure. It is the top view which showed an example of the speckle cancellation pattern schematically. It is the top view which showed the other example of the speckle cancellation pattern schematically. It is the schematic for demonstrating an example of the optical system of the optical scanning device to which the Example of an optical deflector is applied. It is the schematic for demonstrating an example of the optical system of the laser printer to which the Example of an optical deflector is applied. It is a schematic plan view for demonstrating the other Example of the light transmissive member for covers. It is a schematic sectional drawing for demonstrating one Example of an optical lens. It is a schematic sectional drawing for demonstrating one Example of an optical mirror. It is the schematic for demonstrating the other Example of an optical deflector.

  In the light transmissive member for a cover of an optical deflector according to the present invention, an example in which the speckle elimination pattern is also formed on the surface of a portion that transmits incident light to the mirror portion can be given. As a result, since the pecking of the laser beam can be reduced for both the incident light to the mirror part and the reflected light of the mirror part, the speckle elimination pattern is arranged only on the optical path of the reflected light of the mirror part. As compared with the above, the pecking of the laser beam can be further reduced.

  Moreover, the light transmissive member for the cover of the optical deflector of the present invention can be exemplified by providing a light shielding portion around the speckle elimination pattern. In this aspect of the light transmissive member for the cover of the optical deflector according to the present invention, stray light can be removed by the light shielding portion with respect to the incident light and the reflected light on the mirror portion. The light shielding portion is formed of, for example, a light absorbing film such as chrome or frosted glass. However, the configuration of the light shielding portion is not limited to these. In addition, the light transmissive member for the cover of the optical deflector of the present invention may not include the light shielding portion.

  In addition, the light transmissive member for the cover of the optical deflector according to the present invention includes an example in which the speckle elimination pattern is provided on both the surface facing the mirror portion and the opposite surface. In this aspect of the light deflecting member for the cover of the optical deflector of the present invention, the speckle elimination pattern is allowed to pass through both sides of the light transmitting member for the cover with respect to the incident light and the reflected light to the mirror part. Therefore, the polarization state can be made more random, and speckle can be reduced better.

  In the optical deflector of the present invention, for example, the speckle elimination pattern is disposed at least on the optical path of the reflected light, and an incident angle θ of light incident on the speckle elimination pattern from the mirror side is 0 °. An example where ≦ θ ≦ 30 ° can be given. Thereby, the speckle cancellation function of the speckle cancellation pattern is maintained. However, in the present invention, the incident angle θ of light incident on the speckle elimination pattern is not limited to 0 ° ≦ θ ≦ 30 °, and may be larger than 30 °. When the incident angle of the light incident on the speckle eliminating pattern exceeds 30 °, the speckle eliminating function of the speckle eliminating pattern is lowered, but for example, the function of 85% or more is maintained until the incident angle is 40 °. .

Embodiments of the present invention will be described below.
According to one aspect of the present invention, a speckle elimination pattern is constructed on a light transmission member for a cover of an optical deflector such as a MEMS mirror or a polygon mirror, for example, a cover glass, and a speckle elimination effect and a dustproof effect are achieved simultaneously.

  Further, according to the present invention, it is possible to reduce the number of parts of the optical system of the laser light by constructing a speckle elimination pattern on the surface of the optical element that transmits, refracts, or reflects the laser light.

  The present invention can reduce the number of parts and improve the degree of design freedom by combining an optical deflector and a speckle canceling element (means) that have been separately configured so far.

In the optical deflector according to the present invention, the speckle elimination pattern having a speckle reduction function is formed on the light transmission member for the cover, and thus is not easily affected by external impact or the like.
Further, since a light shielding portion that shields light other than the use area is formed around the speckle elimination pattern, it is possible to provide a stray light prevention effect.

  Next, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the Example demonstrated below.

  1A and 1B are schematic views for explaining an embodiment of an optical deflector. FIG. 1A is a plan view and FIG. 1B is a cross-sectional view. FIG. 1B corresponds to a cross section at the position AA in FIG. FIG. 2 is a schematic plan view showing the cover light-transmitting member of the embodiment. FIG. 3 is a schematic plan view showing the optical deflector body of the embodiment.

  The optical deflector 1 includes a main body 3, a spacer 4, and a cover glass 5 (light transmitting member for cover). The main body 3 includes a frame 7, a torsion spring 9, a mirror 11, and a mirror 13. The spacer 4 is formed in a frame shape along the frame portion 7 of the main body portion 3. The cover glass 5 includes a light transmissive substrate 15 and a speckle eliminating pattern 17.

The material of the light transmissive substrate 15 is, for example, glass. The material of the speckle elimination pattern 17 is, for example, quartz, a metal oxide such as Ta ₂ O ₅ , a resin, or the like. In the present invention, the material for the light transmissive member for the cover is not limited to glass, quartz, metal oxide, or the like, but may be other light transmissive materials. Further, an antireflection film (antireflection coating) may be formed on the cover glass 5 such as the surface of the light-transmitting substrate 15 or the surface of the speckle eliminating pattern 17.

  The main body 3 is manufactured by MEMS technology. The mirror portion 11 is supported by the two torsion spring portions 9 and 9 and is disposed in the opening portion of the frame portion 7. A mirror 13 is disposed on the mirror unit 11. The main body 3 includes a drive system (not shown) for vibrating the mirror unit 11. The main body 3 is disclosed in Patent Document 3, for example. The main body 3 is called a MEMS mirror. Examples of the driving method of the MEMS mirror include an electromagnetic method using a magnetic field and a coil, a piezoelectric method using a piezoelectric element, and an electrostatic method using static electricity.

  The speckle elimination pattern 17 is formed by a method similar to the manufacturing method of the sub-wavelength structure disclosed in Patent Document 4, for example. The method for forming the speckle elimination pattern 17 is not limited to the manufacturing method disclosed in Patent Document 4. The speckle elimination pattern 17 may be formed by processing the light-transmitting substrate 15 itself, or formed by processing a member formed on the light-transmitting substrate 15. There may be.

  The cover glass 5 is attached to the main body 3 via the spacer 4. The spacer 4 is joined to the frame portion 7 of the main body portion 3. The light transmissive substrate 15 of the cover glass 5 is bonded to the spacer 4. The bonding between the spacer 4 and the frame portion 7 and the bonding between the spacer 4 and the cover glass 5 may be any bonding such as direct bonding such as anodic bonding or indirect bonding using an adhesive. The method for attaching the main body 3 to the cover glass 5 is not limited to the method using the spacer 4. For example, a counterbore (concave portion) may be formed on the surface of the light transmissive substrate 15 facing the main body 3, and the light transmissive substrate 15 and the frame portion 7 may be joined. Alternatively, the cover glass 5 may be attached to the main body 3 directly or via the spacer 4 using a cylindrical cover member that covers the peripheral edge of the upper surface of the cover glass 5 and has an opening at the center.

  The cover glass 5 is disposed at a distance from the torsion spring portion 9 and the mirror portion 11. A speckle elimination pattern 17 is formed on the surface of the light-transmitting substrate 15 of the cover glass 5. The speckle elimination pattern 17 is disposed in a part that transmits incident light and reflected light to the mirror unit 11.

  The speckle elimination pattern 17 is disposed, for example, on the surface opposite to the main body 3 side of the light transmissive substrate 15. However, the speckle elimination pattern 17 may be formed on the surface of the light transmissive substrate 15 on the main body 3 side as shown in FIG. 4, or the light transmissive substrate 15 as shown in FIG. It may be formed on both sides.

  The speckle elimination pattern 17 is a portion in which the sub-wavelength structure regions exhibiting structural birefringence having grooves arranged repeatedly with a period shorter than the wavelength of light to be used are different from each other in the optical axis direction in which the grooves are arranged. It is arranged and formed so as to have. Such a speckle elimination pattern 17 is disclosed in Patent Documents 1 and 2, for example.

  FIG. 6 is a schematic cross-sectional view for explaining the subwavelength structure. The birefringence effect of the subwavelength structure will be described with reference to FIG.

  The structure shown in FIG. 6 shows a general subwavelength structure. A sub-wavelength uneven structure having an uneven period (pitch) P shorter than the wavelength of light to be used is formed. Assuming that the medium having the sub-wavelength uneven structure is air and a medium having a refractive index n. The width of the land of ridges of refractive index n is L, and the width of the groove of grooves formed of an air layer is S, and P = L + S. L / P is called a filling factor (F). d is the depth of the groove.

  As a measure of the period P, it is a period shorter than the wavelength of the shortest incident light to be used, and more desirably, a period not more than half of the used wavelength. A periodic structure having a period P shorter than the wavelength of the incident light does not diffract the incident light, so that the incident light is transmitted as it is and exhibits birefringence characteristics with respect to the incident light. That is, the refractive index varies depending on the polarization direction of incident light. As a result, various wave plates can be realized because the phase difference can be arbitrarily set by adjusting the parameters relating to the structure.

  Structural birefringence means that when two types of media having different refractive indexes are arranged in a stripe pattern with a period shorter than the wavelength of light, a polarization component parallel to the stripe (TE wave) and a polarization component perpendicular to the stripe (TM The refraction index (referred to as an effective refraction index) differs from that of a wave, and birefringence occurs.

Assume that light having a wavelength twice or more than the period of the sub-wavelength structure is vertically incident. The effective refractive index of the sub-wavelength structure is given by the following equation depending on whether the polarization direction of the incident light is parallel (TE direction) or perpendicular (TM direction) to the groove of the sub-wavelength structure.
n (TE) = (F × n ² + (1−F)) ^1/2
n (TM) = (F / n ² + (1−F)) ^1/2

  The effective refractive index when the polarization direction of the incident light is parallel to the groove of the sub-wavelength structure is expressed as n (TE), and the effective refractive index when it is perpendicular is expressed as n (TM). The symbol F in the equation is the above-mentioned filling factor.

The phase difference (retardation) Δ between the TE wave and TM wave of light transmitted through such a subwavelength structure is:
Δ = Δn · d
It is. Here, Δn is the difference between n (TE) and n (TM), and d is the depth of the groove.

  When linearly polarized light is incident on the sub-wavelength structure region, the transmitted light is changed to elliptically polarized light by this phase difference. When linearly polarized light is transmitted through portions where the optical axis directions are different from each other in the sub-wavelength structure region, the ellipticity is different between portions where the optical axis directions are different from each other.

FIG. 7 is a plan view schematically showing an example of the speckle elimination pattern.
A plurality of sub-wavelength structure regions 19 are arranged in the speckle elimination pattern 17. The sub-wavelength structure regions 19 are arranged, for example, without any gaps. However, the adjacent sub-wavelength structure regions 19 may be arranged at intervals.

  Here, 8 × 8 = 64 sub-wavelength structure regions 19 are shown. However, this is a schematic diagram, and the number of sub-wavelength structure regions 19 is not limited to the number. The higher the number, the better. For example, if the speckle elimination pattern 17 is a square of 5 mm × 5 mm and the sub-wavelength structure area 19 is 50 μm × 50 μm, the speckle elimination where 100 × 100 = 10000 sub-wavelength structure areas 19 are arranged. Pattern 17 is obtained.

  The sub-wavelength structure region 19 has a striped uneven structure composed of grooves arranged repeatedly with a period shorter than the wavelength of light to be used. The arrangement direction of the striped irregularities is an optical axis, and the optical axis is indicated by an arrow in the figure. In this embodiment, each subwavelength structure region 19 has one optical axis.

  Here, the sub-wavelength structure regions 19 are arranged so that the optical axis directions are different between the adjacent sub-wavelength structure regions 19 so that the optical axis directions have different portions between the adjacent sub-wavelength structure regions 19. Yes. The optical axis direction of the sub-wavelength structure region 19 is formed to have one of 360 degrees divided into 15 directions, and the speckle elimination pattern 17 has a sub-wavelength so that the optical axis direction is random. A structure region 19 is arranged.

  The sub-wavelength structure region 19 does not have to have one optical axis, and the sub-wavelength structure region 19 may be formed to have optical axes in two directions orthogonal to each other. Further, it may be a sub-wavelength structure region 19 having a plurality of optical axes, and a concave-convex structure groove constituting the sub-wavelength structure so that the optical axis direction spreads radially from the center as will be described later. May be a subwavelength structure region 19 in which are arranged concentrically.

  The speckle elimination pattern 17 relates to the depth of the groove of the concavo-convex structure constituting the sub-wavelength structure, and the entire speckle elimination pattern 17 may have the same or different depth. You may go out.

  In the case of including those with different depths, one form is to make the groove depths uniform within each sub-wavelength structure region 19 and randomly arrange the sub-wavelength structure regions 19 with different groove depths. It is arranged. In the other form, the depth of the groove is changed in each sub-wavelength structure region 19. Such a form is disclosed in Patent Document 2, for example.

  FIG. 8 is a plan view schematically showing another example of the speckle elimination pattern. The speckle elimination pattern of FIG. 8 is composed of one sub-wavelength structure region as a whole without being divided into a plurality of sub-wavelength structure regions.

  In the speckle elimination pattern 17 of FIG. 8, a sub-wavelength structure having a groove 21 arranged repeatedly with a period shorter than the wavelength of light to be used and exhibiting structural birefringence is formed over the entire surface of the speckle elimination pattern. ing. In the sub-wavelength structure, the grooves 21 are concentrically arranged so that the optical axis direction, which is the arrangement direction of the grooves constituting the sub-wavelength structure, spreads radially from the center. Therefore, the optical axis direction indicated by the arrow in the figure is distributed over 360 degrees.

  Further, the depth of the groove 21 constituting the sub-wavelength structure is determined by a cross-sectional view at a position from the center (A1) of the speckle elimination pattern 17 to one point (A2) in the radial direction. It is formed so as to change continuously according to the function of

  In this embodiment, the most effective usage is to arrange the optical system so that the center of the incident light comes to the center (A1) of the depolarizing element.

  In the speckle elimination pattern 17 shown in FIG. 7 or FIG. 8, the depth of the groove constituting the sub-wavelength structure may be continuously changed along the optical axis direction. One way to achieve such a continuous change can be to follow a function represented by a trigonometric function, an exponential function, or any other mathematical formula. As the groove depth changes continuously, the phase difference of the light passing through this subwavelength structure region changes continuously, and the polarization state changes continuously to create various polarization states. To further contribute.

The phase difference Δ generated in the speckle elimination pattern 17 is
λ / 4 ≦ Δ ≦ λ
It is preferable that the sub-wavelength structure is designed so that Thereby, even if it is the light beams which passed through the different place of this depolarization element, the interference can be prevented.

  In the present invention, the speckle elimination pattern is not limited to that shown in FIG. 7 or FIG. In the present invention, the speckle elimination pattern is an optical axis direction in which a sub-wavelength structure region having a groove arranged repeatedly with a period shorter than the wavelength of light to be used and exhibiting structural birefringence is the groove arrangement direction. Any configuration may be used as long as they are arranged so as to have different portions.

Returning to FIG. 1, the description of the optical deflector 1 will be continued.
The optical deflector 1 changes the reflection direction by the mirror 13 by the vibration of the mirror unit 11. As a result, the reflected light is scanned.

  Incident light on the mirror 13 passes through the speckle elimination pattern 17 and the light transmissive substrate 15. The reflected light from the mirror 13 passes through the light transmissive substrate 15 and the speckle eliminating pattern 17. When incident light and reflected light pass through the speckle elimination pattern 17, the polarization state becomes random, and speckle is reduced.

  Thus, by providing the optical deflector 1 with a speckle eliminating function, it is possible to reduce the speckle of the laser light without using a separate speckle eliminating element. Therefore, the optical deflector 1 can reduce the pecking of the laser light without increasing the number of optical elements arranged on the optical path.

An example of an optical system including the optical deflector 1 will be described.
(Application to optical scanning device)
FIG. 9 is a schematic configuration diagram of an optical system of the optical scanning device. The laser light emitted from the light source device 56 that emits the laser light as parallel light is reflected by the total reflection mirror 57 and enters the optical deflector 1. The light incident on the optical deflector 1 is deflected and scanned by the optical deflector 1. The light deflected and scanned by the optical deflector 1 is emitted to the outside of the housing 59 through the emission window 58.

  Light incident on the optical deflector 1 enters the speckle elimination pattern 17 at an incident angle θ1. The light transmitted through the speckle elimination pattern 17 and the light transmissive substrate 15 is reflected by the mirror 13 of the mirror unit 11.

  The mirror unit 11 and the mirror 13 are vibrated so that the light reflected by the mirror 13 is scanned within a range of a predetermined scanning angle. The light reflected by the mirror 13 is emitted to the outside of the optical deflector 1 through the light transmissive substrate 15 and the speckle elimination pattern 17. At this time, the incident angle θ2 of the light reflected by the mirror 13 with respect to the speckle elimination pattern 17 is in the range of 0 ° ≦ θ2.

  The incident angle θ1 of light incident on the speckle elimination pattern 17 from the outside of the optical deflector 1 is preferably 0 ° ≦ θ1 ≦ 30 °. Moreover, it is preferable that the incident angle θ2 of the light incident on the speckle elimination pattern 17 from the mirror unit 11 side is 0 ° ≦ θ2 ≦ 30 °. This is because the speckle elimination function of the speckle elimination pattern 17 is maintained when the incident angle θ of light incident on the speckle elimination pattern 17 is 0 ° ≦ θ ≦ 30 °.

  In the optical system of FIG. 9, the exit window 58 may include a speckle elimination pattern on the light incident surface, the light exit surface, or both. In this case, the incident angle θ of light incident on the speckle elimination pattern is preferably 0 ° ≦ θ1 ≦ 30 °.

(Application to laser printer)
FIG. 10 shows an optical system of a laser printer. Inside the laser diode unit 31, there are provided a laser diode as a light source and a collimating lens for making a laser beam emitted from the laser diode a parallel beam. Laser light emitted as parallel rays from the laser diode unit 31 is deflected and scanned by the optical deflector 1, and is formed into a drum-shaped photosensitive member by an imaging lens system including an F-θ lens 33, a prism 35, and the like. An image is formed on the charged surface of the drum 37.

  In this optical system, the speckle elimination pattern 17 (see FIG. 1) is arranged on the optical deflector 1 so that the laser light emitted from the laser diode unit 31 has a random polarization state. Has been. Here again, it is preferable that the incident angle θ of light incident on the speckle elimination pattern from the mirror portion of the optical deflector 1 is 0 ° ≦ θ ≦ 30 °. Further, the incident angle θ of light incident on the speckle elimination pattern from the outside of the optical deflector 1 is preferably 0 ° ≦ θ ≦ 30 °.

  The optical system to which the optical deflector 1 is applied is not limited to the optical system of the laser printer. The optical deflector of the present invention is applicable to an optical system including an optical deflector that scans the reflection direction of laser light incident on the mirror unit by vibrating the mirror unit.

  FIG. 11 is a schematic plan view for explaining another embodiment of the cover light-transmitting member. In FIG. 11, parts having the same functions as those in FIG.

  Compared with the cover glass 5 shown in FIG. 2, the cover glass 23 (light transmissive member for cover) further includes a light shielding portion 25 formed on the surface of the light transmissive substrate 15. The light shielding portion 25 is disposed around the speckle elimination pattern 17. The surface of the light transmissive substrate 15 on which the light shielding portion 25 is formed may be the same surface as the surface on which the speckle elimination pattern 17 is formed, or may be the opposite surface.

The light shielding portion 25 is formed of, for example, a light absorption film such as chromium, polished glass, or the like.
The cover glass 23 is attached to the main body 3 (see FIGS. 1 and 3) of the optical deflector 1 in the same manner as the cover glass 5. The light deflector 1 in which the cover glass 23 is arranged can remove stray light from the light shielding part 25 with respect to the incident light and the reflected light to the mirror part 11.

Next, examples of the optical lens will be described.
FIG. 12 is a schematic cross-sectional view for explaining an embodiment of the optical lens.
The optical lens 41 includes a lens portion 43 and a speckle elimination pattern 45.

  The lens portion 43 is formed of a light transmissive member having a lens function. The lens unit 43 is, for example, a biconvex lens. However, in the present invention, the lens portion is not limited to a biconvex lens. In the present invention, the lens part may be any light-transmitting member having a lens function, and may be, for example, a plano-convex lens, a biconcave lens, or a plano-concave lens.

  The speckle elimination pattern 45 is formed on one surface of the lens portion 43. The structure of the speckle elimination pattern 45 is the same as the structure of the speckle elimination pattern 17 described with reference to FIGS. 1 and 6 to 8.

  The laser light transmitted through the optical lens 41 has a random polarization state due to the speckle elimination pattern 45, and speckle is reduced.

  By providing the optical lens 41 with a speckle eliminating function, it is possible to reduce the speckle of the laser light without using a separate speckle eliminating element. Therefore, the optical lens 41 can reduce the pecking of the laser light without increasing the number of optical elements arranged on the optical path.

  In the optical lens 41 shown in FIG. 12, the speckle elimination pattern 45 is arranged on the light incident surface of the lens portion 43, but the optical lens of the present invention is not limited to this. In the optical lens of the present invention, the speckle elimination pattern may be disposed on the light exit surface of the lens unit, or may be disposed on both the light incident surface and the light exit surface of the lens unit.

  The speckle elimination pattern 45 is formed by a method similar to the manufacturing method of the sub-wavelength structure disclosed in Patent Document 4, for example. The method for forming the speckle elimination pattern 45 is not limited to the manufacturing method disclosed in Patent Document 4. The speckle elimination pattern 45 may be formed by processing the lens portion 43 itself, or may be formed by processing a member formed on the lens portion 43. .

Next, an example of the optical mirror will be described.
FIG. 13 is a schematic cross-sectional view for explaining an embodiment of the optical mirror.
The optical mirror 51 includes a light reflecting member 53 and a speckle elimination pattern 55.

  The light reflecting member 53 includes a light reflecting surface. The light reflecting member 53 is, for example, a plane mirror. However, in the present invention, the light reflecting member is not limited to a plane mirror. In the present invention, the light reflecting member only needs to have a light reflecting surface, and may be, for example, a convex mirror or a concave mirror.

  The speckle elimination pattern 55 is formed on the light reflecting surface of the light reflecting member 53. The structure of the speckle elimination pattern 55 is the same as that of the speckle elimination pattern 17 described with reference to FIGS. 1 and 6 to 8.

  The incident light and the reflected light on the optical mirror 51 are randomized in the polarization state by the speckle elimination pattern 55, and speckle is reduced.

  By providing the optical mirror 51 with a speckle eliminating function, it is possible to reduce the speckle of the laser beam without using a separate speckle eliminating element. Therefore, the optical mirror 51 can reduce the pecking of the laser light without increasing the number of optical elements arranged on the optical path.

  The speckle elimination pattern 55 is formed, for example, by the same method as the manufacturing method of the sub-wavelength structure disclosed in Patent Document 4. The method for forming the speckle elimination pattern 55 is not limited to the manufacturing method disclosed in Patent Document 4. The speckle elimination pattern 55 is formed by processing a member formed on the light reflecting member 53.

Next, another embodiment of the optical deflector will be described.
FIG. 14 is a schematic configuration diagram for explaining another embodiment of the optical deflector.
The light deflector 61 is a device that performs color image writing by performing optical scanning on a color printing paper (not shown) with three light beams of red (R), green (G), and blue (B).

  The optical deflector 61 includes laser light sources 63R, 63G, and 63B. Each color laser beam emitted from the laser light sources 63R, 63G, and 63B passes through the corresponding modulation means 65R, 65G, and 65B, and is modulated in accordance with the image signal.

  The light beams modulated by the modulation means 65R, 65G, and 65B are incident on the collimating lens systems 67R, 67G, and 67B as parallel light beams as divergent light beams from the light source side, and then are converted into parallel light beams. Incident. The light beams reflected by the mirrors 69R, 69G, and 69B are condensed in the sub-scanning direction by the cylindrical lens systems 71R, 71G, and 71B, and are combined as one light beam by the optical path combining element 73 having a dichroic film. The synthesized light beam is incident on the deflection reflection surface of the rotary polygon mirror 75 (mirror unit).

  When the rotary polygon mirror 75 rotates at a constant speed, the combined light beam is transmitted through lenses 77, 79, and 81 that constitute an Fθ lens that is a scanning imaging optical system while being deflected at a constant angular velocity. The light beam transmitted through the Fθ lens is emitted outside the casing 83 through a speckle elimination pattern 87 formed on the cover light-transmitting member 85 disposed in the casing 83, and a scanned surface (not shown) For example, a light spot is formed on color photographic paper. This light spot is optically scanned on the scanning line 89 at a constant speed, and optical writing is performed on the surface to be scanned. The surface to be scanned is conveyed at a constant speed in the sub-scanning direction orthogonal to the scanning line 89. Along with this conveyance, main scanning is repeated in the sub-scanning direction, and a two-dimensional color image is written on the surface to be scanned. An optical system similar to the optical deflector 61 is disclosed in Patent Document 5, for example.

  The laser light emitted from the optical deflector 61 has a random polarization state due to the speckle elimination pattern 87 formed on the cover light-transmitting member 85, and speckle is reduced. Therefore, the optical deflector 61 can reduce the pecking of the laser light without increasing the number of optical elements arranged on the optical path.

  The structural example, arrangement example, material example, and manufacturing method example of the speckle elimination pattern 87 are, for example, the structural example and arrangement example of the speckle elimination pattern 17 described with reference to FIGS. 1 and 6 to 8. This is the same as the material example and the manufacturing method example.

  As mentioned above, although the Example of this invention was described, this invention is not limited to these, A various change is possible within the range of this invention described in the claim.

DESCRIPTION OF SYMBOLS 1,61 Optical deflector 11 Mirror part 15,23,85 Cover light transmissive member 17,45,55,87 Speckle cancellation pattern 25 Light-shielding part 41 Optical lens 43 Lens part 51 Optical mirror 53 Light reflecting member 75 Mirror (mirror part)

Claims (8)

A cover light-transmitting member attached to an optical deflector that scans a reflection direction of laser light incident on the mirror unit by operating a mirror unit;
A sub-wavelength structure region exhibiting structural birefringence having grooves arranged repeatedly at a period shorter than the wavelength of the light to be used on the surface of the portion of the mirror that transmits the reflected light is arranged in the direction in which the grooves are arranged. A light transmissive member for a cover of an optical deflector, characterized in that a speckle elimination pattern is formed so that certain optical axis directions have different portions.   The light transmissive member for a cover of an optical deflector according to claim 1, wherein the speckle elimination pattern is also formed on a surface of a portion that transmits incident light to the mirror portion.   The light transmissive member for a cover of an optical deflector according to claim 1, further comprising a light shielding portion around the speckle elimination pattern.   4. The light transmissive member for a cover of an optical deflector according to claim 1, wherein the speckle elimination pattern is provided on both the surface facing the mirror portion and the surface on the opposite side thereof. 5. . An optical deflector that scans the reflection direction of laser light incident on the mirror unit by vibrating the mirror unit,
An optical deflector comprising: the light transmissive member for the optical deflector according to any one of claims 1 to 4 on an optical path of incident light and reflected light to the mirror unit. The speckle elimination pattern is disposed at least on the optical path of the reflected light,
The optical deflector according to claim 5, wherein an incident angle θ of light incident on the speckle elimination pattern from the mirror part side is 0 ° ≦ θ ≦ 30 °.   The sub-wavelength structure region exhibiting structural birefringence has grooves arranged repeatedly on the surface of a lens portion made of a light transmissive member having a lens function at a period shorter than the wavelength of light to be used. An optical lens, characterized in that a speckle elimination pattern is formed so that the optical axis directions as directions are different from each other.   An optical axis in which the sub-wavelength structure region exhibiting structural birefringence has grooves arranged repeatedly on the surface of the light reflecting surface of the light reflecting member at a period shorter than the wavelength of the light to be used, and the groove arrangement direction. An optical mirror, characterized in that a speckle elimination pattern is formed so as to have portions having different directions.

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