JP2019159203A - Optical member, projection device, head-mounted display, head-up display, vehicle, spectrometer, and image forming apparatus - Google Patents

Abstract

To provide an optical member that can diffract a specific wavelength with high efficiency, a projection device, a head-mounted display, a head-up display, a vehicle, a spectrometer, and an image forming apparatus.SOLUTION: An optical member 10 comprises: a curved surface part 11; and fine structures 12 that are formed on the curved surface part 11 at a predetermined pitch, and the predetermined pitch changes according to the curvature of the curved surface part 11.SELECTED DRAWING: Figure 2A

Description

  The present invention relates to an optical member, a projection device, a head-mounted display, a head-up display, a vehicle, a spectroscope, and an image forming apparatus.

  The optical member including the diffraction grating diffracts light having a specific wavelength. The band of the diffracted light depends on the periodic structure such as the pitch and depth of the diffraction grating and the material.

  In recent years, an optical member including a curved diffraction grating has been proposed.

  However, a conventional diffraction grating provided on a curved surface cannot diffract a specific wavelength with high efficiency.

  An object of the present invention is to provide an optical member, a projection device, a head-mounted display, a head-up display, a vehicle, a spectroscope, and an image forming apparatus that can diffract a specific wavelength with high efficiency.

  One aspect of the optical member includes a curved surface portion and a fine structure formed on the curved surface portion at a predetermined pitch, and the predetermined pitch varies depending on a curvature of the curved surface portion.

  According to the disclosed technology, a specific wavelength can be diffracted with high efficiency.

It is a top view which shows the diffraction grating which concerns on 1st Embodiment. It is sectional drawing which shows the example of the diffraction grating which concerns on 1st Embodiment. It is sectional drawing which shows the other example of the diffraction grating which concerns on 1st Embodiment. It is a schematic diagram which shows the geometric relationship between a fine structure and an incident angle. It is a figure which shows two types of circular arcs from which a curvature differs. It is a figure which shows the relationship between the x coordinate and incident angle in the circular arc shown to FIG. 4A. It is a figure which shows an example of the relationship between an incident angle and the pitch of a fine structure. It is a figure which shows the example of the dependence to the correction coefficient of diffraction efficiency. It is a figure which shows the relationship between the wavelength of three examples from which the pitch of a microstructure differs, and diffraction efficiency. It is a schematic diagram which shows scattered light. It is a top view which shows the optical member which concerns on 2nd Embodiment. It is sectional drawing which shows the example of the optical member which concerns on 2nd Embodiment. It is a top view which shows the optical member which concerns on 3rd Embodiment. It is a figure which shows the motor vehicle carrying the head-up display which concerns on 4th Embodiment. It is a figure which shows the head-up display which concerns on 4th Embodiment. It is a figure which shows the head mounted display which concerns on 5th Embodiment. It is a figure which shows the image forming apparatus which concerns on 6th Embodiment. It is a figure which shows the spectrometer contained in the image forming apparatus which concerns on 6th Embodiment.

  Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially the same function structure, the duplicate description may be abbreviate | omitted by attaching | subjecting the same code | symbol.

(First embodiment)
First, the first embodiment will be described. The first embodiment relates to an optical member provided with one diffraction grating. FIG. 1 is a plan view showing an optical member according to the first embodiment. FIG. 2A is a cross-sectional view illustrating an example of the optical member according to the first embodiment, and FIG. 2B is a cross-sectional view illustrating another example of the optical member according to the first embodiment.

As shown in FIG. 1, the optical member 10 according to the first embodiment includes a curved surface portion 11 and a microstructure 12 formed on the curved surface of the curved surface portion 11. The curved surface portion 11 may have a concave curved surface 11A as shown in FIG. 2A, or may have a convex curved surface 11B as shown in FIG. 2B. The material of the curved surface portion 11 is not particularly limited, and is, for example, synthetic quartz or borosilicate glass. Examples of borosilicate glass include Tempax (registered trademark) and Pyrex (registered trademark). The material of the fine structure 12 has an optical constant different from that of the material of the curved surface portion 11, for example, TiO ₂ , Ta ₂ O ₅ , Si ₃ N _4, or Al ₂ O ₃ . The fine structure 12 is formed at a pitch that varies depending on the curvature of the curved surface 11A or 11B.

  Next, the pitch of the fine structure 12 will be described. FIG. 3 is a schematic diagram illustrating a geometric relationship between the fine structure and the incident angle.

Here, a concave surface 22 having a radius of curvature R is formed on the curved surface portion 21, a fine structure 23 </ b> C is formed at the center C of the concave surface 22, and a fine structure is formed at a position K separated from the center of the concave surface 22 by x _{k in the} x direction. It is assumed that the body 23K is formed. In this case, when the center of the circle 26 constituting the concave surface 22 is O and the angle formed by the line segment OC and the line segment OK is θ, the relationship of the expression (1) is established. Further, if the difference in the z direction between the center C and the position K is _zpk , the relationship of Expression (2) is established.

θ = sin ⁻¹ (x _k / R) (1)
z _pk = R (1-cos θ) (2)

These geometric relationships, the incident angle of light incident from the center C to the position K at a distance x _k can be specified, given the radius of curvature R or curvature.

  For example, for the two types of arcs 41 and 42 having different curvatures shown in FIG. 4A, the incident angle of the incident light 43 can be specified for each x coordinate as shown in FIG. 4B. 4A and 4B, the curvature of the arc 41 is larger than the curvature of the arc 42. As shown in FIG. 4B, the incident angle for each x coordinate is larger than the arc 42 in the arc 41 having a large curvature.

  A diffraction grating formed on a plane does not have such a difference in incident angle depending on the position, and such a difference in incident angle is a phenomenon peculiar to a diffraction grating using a curved surface. The difference in incident angle leads to a decrease in diffraction efficiency of the diffraction grating that diffracts light of a specific wavelength. On the other hand, by adjusting the pitch of the fine structures, it is possible to suppress a decrease in diffraction efficiency due to a difference in incident angles. Such a relationship holds when the curved surface is a convex surface, and also when the curved surface is not a spherical surface but a flat spherical surface. When the curved surface is an oblate spherical surface, the curvature increases as the distance from the center of the curved surface increases.

  In the present embodiment, in view of such a tendency, the fine structures 12 are formed at a pitch that varies depending on the curvature of the curved surface 11A or 11B. FIG. 5 is a diagram illustrating an example of the relationship between the incident angle and the pitch of the fine structure 12. This figure shows the relationship in the optical member 10 for diffraction of light having a wavelength of 532 nm. As shown in FIG. 4B, when the curvature of the curved surface is given, the incident angle for each x coordinate is specified, and in this embodiment, the fine structure 12 is formed at a pitch corresponding to this incident angle.

  According to such a first embodiment, light of a specific wavelength can be diffracted with high efficiency. Further, the specific wavelength to be diffracted with high efficiency can be arbitrarily selected by adjusting the pitch of the fine structure 12. That is, the relationship shown in FIG. 5 relates to light having a wavelength of 532 nm, but since the relationship between the incident angle and the pitch can be calculated according to the wavelength of light to be diffracted, the microstructure 12 is formed at a pitch based on this relationship. By doing so, it is possible to diffract an arbitrary wavelength with high efficiency.

  In order to further improve the diffraction efficiency, it is preferable that the pitch of the fine structures 12 is corrected according to the incident angle. For example, if the pitch obtained according to the incident angle θ calculated from the curvature as described above is P (θ), the fine structure 12 has a pitch P (θ represented by the equation (3) using the correction coefficient K. , K).

P (θ, K) = P (θ) × (1−Kθ ² ) (3)

FIG. 6 shows an example of the dependency of the diffraction efficiency on the correction coefficient K. FIG. 6 shows K = 0.0 × 10 ⁻⁴ , 1 × 10 ⁻⁴ , 2 × 10 ⁻⁴ as an example of a case where the curved surface has a radius of curvature of 80 μm and a pitch of 257 nm to 346 nm. An example of 3 × 10 ⁻⁴ is shown. As shown in FIG. 6, the diffraction efficiency changes according to the correction coefficient K. In order to improve the diffraction efficiency of light having a wavelength of 532 nm, 2 × 10 ⁻⁴ is the most suitable among the four correction coefficients K shown in FIG.

FIG. 7 shows the relationship between the diffraction efficiency and the wavelength of three examples in which the curvature radius of the curved surface is 80 μm and the pitch of the microstructure is different. The first example is an example of a diffraction grating in which fine structures are formed at an equal pitch. The second example is an example of a diffraction grating formed with a pitch that varies depending on the curvature. The third example is an example in which the second example is corrected using a correction coefficient K of 2 × 10 ⁻⁴ . As shown in FIG. 7, focusing on the diffraction efficiency of light having a wavelength of 532 nm, the second example is superior to the first example, and the third example is superior to the second example.

  When the curvature of the curved surface is constant, that is, when the curved surface is a spherical surface, it is preferable that the fine structures are formed with a pitch corrected using a correction coefficient. Since the incident angle increases as the distance from the center of the curved surface increases, it is preferable that the pitch of the fine structure decreases as the distance from the center of the curved surface increases.

  Further, it is preferable that the fine structure is not formed on the entire curved surface of the curved portion, but the fine structure is not formed on the end portion of the curved surface. The end of the curved surface here refers to a region from the edge of the curved surface to the inside by 5% of the distance from the center of the curved surface to the edge in plan view. For example, when the planar shape of the curved surface is a circle, it is preferable that a fine structure is formed in a region from the center of the curved surface to 95% of the radius, and no fine structure is formed on the outside thereof. As shown in FIG. 8, when the fine structure is formed at the end of the curved surface 51 of the curved surface portion 50, when the incident light 52 enters the end, scattered light 53 that cannot be calculated and is not assumed is generated. There is a fear. This is to suppress the generation of such scattered light 53.

  The curved surface portion 11 may be made of a material that reflects incident light, or may be made of a material that transmits incident light. That is, the optical member 10 may be either a transmission type or a reflection type.

(Second Embodiment)
Next, a second embodiment will be described. The second embodiment relates to an optical member having a plurality of diffraction gratings. FIG. 9A is a plan view showing an optical member according to the second embodiment. FIG. 9B is a cross-sectional view illustrating an example of an optical member according to the second embodiment. FIG. 9B corresponds to a cross-sectional view taken along line II in FIG. 9A.

  As shown in FIGS. 9A and 9B, the optical member 60 according to the second embodiment includes a plurality of optical members 10 including the curved surface portion 11 and the fine structure 12. For example, the optical member 10 has a regular hexagonal planar shape, and the plurality of optical members 10 are arranged in a honeycomb shape so as to form a hexagonal close-packed structure.

  The optical member 60 configured as described above has a structure in which curved surfaces are continuous except for a joint between the optical members 10. In the second embodiment, the arrangement direction of the fine structures 12 is the same among the plurality of optical members 10.

(Third embodiment)
Next, a third embodiment will be described. The third embodiment relates to an optical member having a plurality of diffraction gratings. FIG. 10 is a plan view showing an optical member according to the third embodiment.

  As shown in FIG. 10, the optical member 70 according to the third embodiment includes a plurality of optical members 10 including the curved surface portion 11 and the fine structure 12. For example, the optical member 10 has a regular hexagonal planar shape, and the plurality of optical members 10 are arranged in a honeycomb shape so as to form a hexagonal close-packed structure.

  The optical member 70 configured as described above has a structure in which curved surfaces are continuous except for a joint between the optical members 10. In the third embodiment, unlike the second embodiment, the arrangement direction of the microstructures 12 is orthogonal between the plurality of optical members 10. That is, the optical member 10 in which the fine structures 12 are arranged in parallel to the x direction and the optical member 10 in which the fine structures 12 are arranged in parallel to the y direction are alternately arranged. According to the third embodiment, the diffraction efficiency can be increased without depending on the polarization state of the incident coherent light source.

(Fourth embodiment)
Next, a fourth embodiment will be described. The fourth embodiment relates to a head-up display including an optical member. A head-up display is an example of a projection device that projects an image by optical scanning. FIG. 11 is a diagram illustrating an automobile equipped with a head-up display according to the fourth embodiment. FIG. 12 is a diagram illustrating a head-up display according to the fourth embodiment.

  The head-up display according to the fourth embodiment includes an imager unit 500 and an optical member 403 provided on the window shield 401. The optical member 403 is a reflective optical member according to any one of the first to third embodiments. The optical member 403 may be processed directly into the window shield 401 or may be attached to the window shield 401.

  As shown in FIG. 11, the imager unit 500 is installed in the vicinity of a window shield 401 such as a windshield of an automobile 400, for example. The projection light L emitted from the imager unit 500 is reflected by the optical member 403 provided on the window shield 401 and travels toward the observer (driver 402) who is the user. Accordingly, the driver 402 can visually recognize the image projected by the imager unit 500 as a virtual image. Note that a combiner may be installed on the inner wall surface of the window shield 401 so that the user can visually recognize the virtual image by the projection light reflected by the combiner.

  As shown in FIG. 12, the imager unit 500 emits laser beams from red, green, and blue laser light sources 501R, 501G, and 501B. The emitted laser light passes through an incident optical system composed of collimator lenses 502, 503, and 504 provided for each laser light source, two dichroic mirrors 505 and 506, and a light amount adjusting unit 507. Deflection is performed by a movable device 523 having a reflecting surface 524. The deflected laser light is projected onto a screen through a projection optical system including a free-form surface mirror 509, an intermediate screen 510, and a projection mirror 511. In the imager unit 500, the laser light sources 501R, 501G, and 501B, the collimator lenses 502, 503, and 504, and the dichroic mirrors 505 and 506 are unitized by an optical housing as the light source unit 530.

  The imager unit 500 projects the intermediate image displayed on the intermediate screen 510 onto the window shield 401 of the automobile 400 so that the driver 402 can visually recognize the intermediate image as a virtual image.

  The respective color laser beams emitted from the laser light sources 501R, 501G, and 501B are substantially collimated by the collimator lenses 502, 503, and 504, and are combined by the two dichroic mirrors 505 and 506. The combined laser light is two-dimensionally scanned by the movable device 523 having the reflecting surface 524 after the light amount is adjusted by the light amount adjusting unit 507. The projection light L that has been two-dimensionally scanned by the movable device 523 is reflected by the free-form surface mirror 509, corrected for distortion, and then condensed on the intermediate screen 510 to display an intermediate image. The intermediate screen 510 includes a microlens array in which microlenses are two-dimensionally arranged, and enlarges the projection light L incident on the intermediate screen 510 in units of microlenses.

  The movable device 523 reciprocally moves the reflecting surface 524 in two axial directions, and two-dimensionally scans the projection light L incident on the reflecting surface 524. The drive control of the movable device 523 is performed by the control device 521 in synchronization with the light emission timings of the laser light sources 501R, 501G, and 501B. The optical scanning device 520 includes a control device 521, a movable device 523, and a reflection surface 524. The microstructure of the optical member 403 depends not only on the curvature of the curved surface portion, but also on the wavelength parameter of the laser light emitted from the laser light sources 501R, 501G, and 501B.

  According to the head-up display according to the fourth embodiment, the light emitted from the imager unit 500 is reflected by the window shield 401 and projected onto the driver 402 so that the image can be shown to the driver 402. At this time, only light of a specific wavelength corresponding to the pitch of the fine structure included in the optical member 403 can be reflected with high efficiency. When the light is reflected by the window shield 401 without using the optical member 403, only a few percent of reflected light is generally obtained. However, according to the present embodiment, for example, a reflectance of around 60% can be obtained. Therefore, power saving and size reduction of the imager unit 500 can be realized.

(Fifth embodiment)
Next, a fifth embodiment will be described. The fifth embodiment relates to a head mounted display including an optical member. A head mounted display is an example of a projection device that projects an image by optical scanning. FIG. 13 is a diagram illustrating a head mounted display according to the fifth embodiment.

  As shown in FIG. 13, a head mount display (HMD) 600 according to the fifth embodiment includes a control device 521, a light source unit 530, a light amount adjustment unit 507, and a movable device having a reflection surface 524. 523, a light guide plate 601, and a half mirror 602.

  As described above, the light source unit 530 is obtained by unitizing the laser light sources 501R, 501G, and 501B, the collimator lenses 502, 503, and 504, and the dichroic mirrors 505 and 506 with an optical housing. In the light source unit 530, the three color laser beams from the laser light sources 501R, 501G, and 501B are combined by the dichroic mirrors 505 and 506. From the light source unit 530, the synthesized parallel light is emitted.

  The light from the light source unit 530 is incident on the movable device 523 after the light amount is adjusted by the light amount adjustment unit 507. The movable device 523 moves the reflecting surface 524 in the XY directions based on a signal from the control device 521, and performs two-dimensional scanning with the light from the light source unit 530. The drive control of the movable device 523 is performed in synchronization with the light emission timings of the laser light sources 501R, 501G, and 501B, and a color image is formed by the scanning light.

  Scanning light from the movable device 523 enters the light guide plate 601. The light guide plate 601 guides the scanning light to the half mirror 602 while reflecting the scanning light on the inner wall surface. The light guide plate 601 is formed of a resin or the like having transparency with respect to the wavelength of the scanning light.

  The half mirror 602 reflects the light from the light guide plate 601 to the back side of the HMD 600 and emits it in the direction of the eyes of the wearer 603 of the HMD 600. The half mirror 602 has, for example, a free-form surface shape, and includes a reflective optical member according to any one of the first to third embodiments. The microstructure of the optical member depends not only on the curvature of the curved surface portion but also on the wavelength parameter of the laser light emitted from the laser light sources 501R, 501G, and 501B. The image by the scanning light is imaged on the retina of the wearer 603 by reflection at the half mirror 602. Alternatively, an image is formed on the retina of the wearer 603 by the reflection from the half mirror 602 and the lens effect of the crystalline lens in the eyeball. Also, spatial distortion of the image is corrected by reflection at the half mirror 602. The wearer 603 can observe an image formed by light scanned in the XY directions.

  The wearer 603 observes the image by the light from the outside and the image by the scanning light superimposed through the half mirror 602. A mirror may be provided instead of the half mirror 602 so that light from the outside can be eliminated and only an image by scanning light can be observed.

  A projection apparatus to which the optical member of the present disclosure can be applied can be applied to an apparatus that projects an image by performing optical scanning with a movable device 523 having a reflective surface 524. The above-described head-up display and head Not limited to mounted displays. For example, the present invention can be applied to a projector that is placed on a desk or the like and projects an image on a display screen.

  The image projection apparatus is not only a vehicle or a mounting member, but also, for example, a moving body such as an aircraft, a ship, or a mobile robot, or a work robot that operates a driving target such as a manipulator without moving from the spot. It may be mounted on a non-moving body.

(Sixth embodiment)
Next, a sixth embodiment will be described. The sixth embodiment relates to an image forming apparatus including an optical member. FIG. 14 is a diagram illustrating an image forming apparatus according to the sixth embodiment. FIG. 15 is a diagram illustrating a spectroscope included in an image forming apparatus according to the sixth embodiment.

  As shown in FIG. 14, the image forming apparatus 80 according to the sixth embodiment includes a spectral characteristic measuring device 89 including a spectroscope. The image forming apparatus 80 also includes a paper feed cassette 81a, a paper feed cassette 81b, a paper feed roller 82, a controller 83, a writing optical system 84, a photosensitive member 85, an intermediate transfer member 86, a fixing roller 87, a paper discharge roller 88, and the like. ing.

  In the image forming apparatus 80, when the four photoconductors 85 are exposed by the writing optical system 84 based on the image data, an electrostatic latent image corresponding to each color is formed on each photoconductor 85. Development processing is performed by attaching a color material such as toner of a color corresponding to the electrostatic latent image. Each color toner image formed on each photoconductor 85 by this development processing is transferred onto the intermediate transfer body 86 so as to overlap each other. Thereafter, the toner image on the intermediate transfer member 86 is transferred from the paper feed cassettes 81a and 81b to an image bearing medium 90 such as a guide (not shown) and paper conveyed by the paper feed roller 82. The toner image transferred onto the image bearing medium 90 in this manner is fixed by the fixing roller 87, and the image bearing medium 90 is ejected by the ejection roller 88. In the present embodiment, the spectral characteristic measuring device 89 is installed at the subsequent stage of the fixing roller 87.

  As shown in FIG. 16, in the spectroscope 100 included in the spectral characteristic measuring device 89, illumination is performed from the illumination system 102 from a direction inclined by 45 ° from the normal direction of the measurement target surface of the image bearing medium 90 that is the measurement target. . The spectroscope 100 condenses the diffusely reflected light beam from the surface to be measured on the slit 111 by the condensing lens 103, and spectrally condenses and condenses the light beam that has passed through the slit 111 by the concave diffraction element 112, and the array light receiving element 113. invite. The concave diffraction element 112 includes a reflective optical member according to any one of the first to third embodiments. This microstructure of the optical member depends not only on the curvature of the curved surface portion but also on the wavelength parameter of the light emitted from the illumination system 102. The array light receiving element 113 has a plurality of light receiving areas arranged in a direction corresponding to the diffraction direction of the concave diffraction element 112, and detects light intensity signals in different wavelength bands in each light receiving area. Then, the reflectance of each wavelength band corresponding to each light receiving region is calculated from the detection result in each light receiving region of the array light receiving element 113 and the light intensity signal obtained from the standard white surface or the like, and the spectral reflectance is calculated. obtain. If the spectral reflectance obtained in this way is used, other spectral characteristics such as parameters (colorimetric values) such as the XYZ color system and the L * a * b * color system can be grasped.

  In the image forming apparatus 80, the spectral characteristic measuring device 89 measures (estimates) the spectral characteristics (spectral reflectance, etc.) of the output image (measurement target) at a predetermined timing, and sends the measurement results to the controller 83. The controller 83 functions as an image forming condition adjusting unit, and adjusts the image forming condition based on the measurement result. As a result, since automatic color calibration is possible, it is possible to continuously provide a high-quality image with little color variation, and to stably operate the image forming apparatus.

DESCRIPTION OF SYMBOLS 10 Optical member 11 Curved surface part 11A, 11B Curved surface 12 Fine structure 60 Optical member 70 Optical member 80 Image forming apparatus 89 Spectral characteristic measuring apparatus 100 Spectrometer 112 Concave diffraction element 400 Car 401 Window shield 402 Driver 403 Optical member 500 Imager unit 501R, 501G, 501B Laser light source 520 Optical scanning device 530 Light source unit 600 Head mounted display 602 Half mirror 603 Wearer

Japanese Patent No. 4387855

Claims (14)

A curved surface section;
A fine structure formed on the curved surface portion at a predetermined pitch;
With
The optical member according to claim 1, wherein the predetermined pitch varies depending on a curvature of the curved surface portion.   The optical member according to claim 1, wherein the predetermined pitch becomes narrower as a curvature of the curved surface portion increases. A curved surface section;
A fine structure formed on the curved surface portion at a predetermined pitch;
With
The optical member, wherein the predetermined pitch becomes narrower as it approaches the outer edge of the curved surface portion.   The optical member according to any one of claims 1 to 3, wherein the fine structure is formed only inside the end portion of the curved surface portion.   The optical member according to claim 1, wherein the curved surface portion is made of a material that reflects or transmits incident light.   The optical member according to claim 1, comprising a plurality of combinations of the curved surface portion and the fine structure.   The optical member according to claim 6, wherein the arrangement direction is shifted by 90 degrees between the plurality of fine structures.   The optical member according to claim 6 or 7, wherein the combination is arranged in a honeycomb shape. A light source that emits coherent light;
An optical scanning device for optically scanning light from the light source;
The optical member according to any one of claims 1 to 8, wherein light scanned by the optical scanning device is incident;
With
The predetermined pitch varies depending on a curvature of the curved surface portion and a wavelength parameter of the coherent light.   A head-mounted display comprising the projection device according to claim 9.   A head-up display comprising the projection device according to claim 9.   A vehicle comprising the head-up display according to claim 11. The optical member according to any one of claims 1 to 8,
An incident member that makes light incident on the optical member;
A light receiving means for receiving the light dispersed by wavelength by the optical member;
A spectroscope characterized by comprising: In an image forming apparatus for forming an image composed of a plurality of colors on an image bearing medium,
Spectral characteristic measuring means for measuring spectral characteristics of the image formed on the image bearing medium;
Image forming condition adjusting means for adjusting image forming conditions based on the spectral characteristics measured by the spectral characteristic measuring means;
Have
An image forming apparatus comprising the spectroscope according to claim 13.

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