JP2017015955A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device which reduces unevenness of the light intensity emitted from a screen.SOLUTION: A HUD device includes: green and blue LDs 11 g, 11 b for emitting green and blue laser beams G, B, respectively; a red LD 11 r for emitting a red laser beam R longer in wavelength than these laser beams G, B; a light combining part; and a MEMS scanner for scanning a synthesized laser beam synthesized by the light combining part in a scanning direction and a sub-scanning direction on a transmission screen. Each of the laser beams R, G, and B includes an elliptic cross-section Ab having the longitudinal direction. The green and blue LDs 11 g and 11 b are installed such that the longitudinal direction of the beam cross-section Ab of the green and blue laser beams G and B corresponds to the sub-scanning direction on the transmission screen. The red LD 11 r is installed in the direction to cross the longitudinal direction of the beam cross section Ab in the green and blue laser beams G and B viewed from the direction along an optical axis Ia.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a display device.

  2. Description of the Related Art Conventionally, as an example of a display device, a head-up display device has been proposed in which light representing a display image is irradiated on a windshield or the like so that a driver can visually recognize a virtual image corresponding to the display image.

  For example, the head-up display device described in Patent Document 1 generates a display image on a screen by scanning a laser beam emitted from a semiconductor laser toward the screen. In this head-up display device, there is a possibility that a speckle pattern called a speckle is generated in a display image due to interference of laser light.

JP-A-7-270711

  In order to solve such a problem, the present applicant uses a micro lens array (MLA) screen in a head-up display device, and sets a beam diameter of laser light to be projected smaller than the lens pitch. I'm considering doing that. Thereby, it is suppressed that laser beams interfere, and generation | occurrence | production of a speckle or an interference fringe can be suppressed. This type of head-up display device scans laser light so as to move in a sub-scanning direction orthogonal to the scanning direction while reciprocating in the main scanning direction on the microlens array. The amount of movement of the laser light in the main scanning direction during a predetermined time is extremely large compared to the amount of movement of the laser light in the sub-scanning direction.

  By the way, it is generally known that the wavelength differs depending on the color of laser light. In the head-up display device studied by the present applicant, the beam diameter of each color laser beam on the screen varies depending on the wavelength difference of each color laser beam. Specifically, the beam diameter of red laser light having the longest wavelength is larger than the beam diameter of blue laser light or green laser light having a shorter wavelength. The difference in the beam diameter of each laser beam in the main scanning direction hardly affects the display image because the laser beam moves mainly in the main scanning direction. However, unlike the main scanning direction, the laser light does not move directly in the sub-scanning direction, so that the intensity of the light emitted from the screen becomes uniform with the difference in the beam diameter of each color laser light in the sub-scanning direction. However, when the viewer looks at the display image, there is a risk that the viewer may perceive brightness unevenness or color unevenness.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a display device in which unevenness in intensity of light emitted from a screen is reduced.

  To achieve the above object, a display device according to the present invention includes a first laser light source that emits a first laser beam, and a second laser beam that emits a second laser beam having a longer wavelength than the first laser beam. A laser light source, a light combining unit that combines the first laser light and the second laser light to generate a combined laser light, and a reciprocating motion of the combined laser light along a scanning direction on a screen, And a scanning section that scans in a sub-scanning direction orthogonal to the scanning direction, and the first laser light and the second laser light are the first laser light and the second laser light, respectively. When the laser beam is cut in a direction perpendicular to the optical axis of the laser beam, the laser beam has an elliptical beam cross section having a longitudinal direction and a short direction, and the first laser light source is the beam in the first laser beam. The longitudinal direction of the surface corresponds to the sub-scanning direction on the screen, and the second laser light source is the second laser light source when viewed from a direction along the optical axis of the second laser light. The longitudinal direction of the beam cross section in the laser light is installed in a direction crossing the longitudinal direction of the beam cross section in the first laser light.

  According to the present invention, unevenness in intensity of light emitted from a screen can be reduced.

It is a mimetic diagram showing a vehicle carrying a HUD device concerning one embodiment of the present invention. It is the schematic which shows the structure of the HUD apparatus which concerns on one Embodiment of this invention. It is the schematic which shows the structure of the synthetic | combination laser beam generator which concerns on one Embodiment of this invention. It is a top view of the screen which shows the scanning locus | trajectory which concerns on one Embodiment of this invention. It is a top view of the screen which shows two scanning traces which concern on one Embodiment of this invention. It is a perspective view showing roughly the composition in the synthetic laser light generator concerning one embodiment of the present invention. (A) which concerns on one Embodiment of this invention is a top view of a micro lens array, (b) is a top view of an aperture array. 1 is a side view schematically showing a transmission screen according to an embodiment of the present invention. (A)-(e) which concerns on one Embodiment of this invention is a side view of the micro lens array which showed the position of the synthetic | combination laser beam at the time of the scanning to a main scanning direction, and the light distribution in the eye box in the position It is a figure which shows intensity distribution. FIG. 10 is a diagram showing the light distribution intensity distribution in the eye box in the main scanning direction when the light distribution intensity distributions of FIGS. 9A to 9E according to an embodiment of the present invention are integrated with time. (A) and (b) according to an embodiment of the present invention is a diagram showing the position of the synthetic laser light in the sub-scanning direction and the light distribution intensity distribution in the eye box at that position, (c), It is a figure which shows the light distribution intensity distribution in the eye box of the subscanning direction at the time of integrating the light distribution intensity distribution of the FIG. 11 (a) and (b) with time. (A)-(c) which concerns on one Embodiment of this invention is drawing which shows the beam shape of each laser beam on a transmission screen, Comprising: (d)-(f) is each color laser beam centering on a micro lens FIGS. 4A to 4I are diagrams showing the light distribution intensity distribution in the eye box in the sub-scanning direction when light is incident, and FIGS. It is a figure which shows the light distribution intensity distribution in the eye box in (j)-(l), and integrated the light distribution intensity distribution of said (d)-(f) and (g)-(i), respectively. It is a figure which shows the light distribution intensity distribution in the eye box in the subscanning direction in the case.

  Hereinafter, a head-up display (HUD) device as an example of a display device according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  As schematically shown in FIG. 1, the HUD device 1 is provided in the dashboard of the vehicle 2 and emits light L representing the generated display image M toward the windshield 3. The viewer (mainly the driver) receives the light L representing the display image M reflected on the windshield 3 in the eyebox 4 that is the viewing area, so that the display is superimposed on the actual scene seen through the windshield 3. The virtual image W corresponding to the image M can be visually recognized.

(Overall configuration of HUD device)
As shown in FIG. 2, the HUD device 1 includes a synthetic laser light generator 10, a MEMS (Micro Electro Mechanical Systems) scanner 20, which is an example of a scanning unit, a field lens 30, a transmission screen 40, and a relay optical unit. 50, a control unit 70, and a housing 60.

  The housing 60 is formed in a box shape from hard resin or the like. The housing 60 has a penetrating opening 60 a formed at a position facing the windshield 3. A curved plate-like window 61 is attached to the opening 60 a of the housing 60. The window 61 is made of a translucent resin such as acrylic so that the light L representing the display image M is transmitted. Each component of the HUD device 1 is accommodated in the housing 60.

(Configuration of synthetic laser light generator)
The combined laser beam generator 10 combines the laser beams R, G, and B of the three primary colors of R (red), G (green), and B (blue) under the control of the control unit 70 to combine one. Laser light C is emitted toward the MEMS scanner 20. Specifically, as shown in FIG. 3, the combined laser beam generator 10 includes a laser diode (LD) group 11, a condenser lens group 12, a polarization axis conversion element 13, a light combining unit 14, and an adjustment unit. And an optical part 19.

  As shown in FIG. 3, the LD group 11 includes a red LD 11 r that emits red laser light R, a green LD 11 g that emits green laser light G, and a blue LD 11 b that emits blue laser light B. The red LD 11r corresponds to a red laser light source or a second laser light source, the green LD 11g corresponds to a green laser light source or a first laser light source, and the blue LD 11b corresponds to a blue laser light source or a first laser light source. As shown in FIG. 6, the LDs 11r, 11g, and 11b are arranged at regular distance intervals. The degree of polarization of each laser beam R, G, B is about several hundred to one, that is, each laser beam R, G, B is linearly polarized. Each of the laser beams R, G, and B includes an elliptical beam section Ab having a longitudinal direction and a short direction when cut in a direction perpendicular to the optical axis Ia. The polarization axes Ip of the laser beams R, G, and B are along the short direction of the beam cross section Ab. The red LD 11r is installed in a direction rotated 90 ° around the optical axis Ia with respect to the green LD 11g and the blue LD 11b. In other words, when viewed from the direction along the optical axis Ia of the red laser beam R, the longitudinal direction of the beam section Ab in which the red laser beam R spreads is orthogonal to the longitudinal direction of the beam section Ab in which the green laser beam G and the blue laser beam B spread. The red LD 11r is installed with respect to the green LD 11g and the blue LD 11b so as to extend in the direction in which the light is emitted. Therefore, the polarization axis Ip of the red laser light R from the red LD 11r is the polarization axis of the green laser light G and the blue laser light B from the green LD 11g and the blue LD 11b when viewed from the direction along the optical axis Ia of the red laser light R. It extends in a direction orthogonal to Ip.

  As shown in FIG. 3, the condensing lens group 12 includes three condensing lights that are converted into convergent light by refracting the laser beams B, R, and G, which are diverging lights emitted from the LDs 11r, 11g, and 11b. It consists of lenses 12r, 12g, and 12b. The condenser lens 12r is installed in the optical path of the red laser light R emitted from the red LD 11r, the condenser lens 12g is installed in the optical path of the green laser light G emitted from the green LD 11g, and the condenser lens 12b is It is installed in the optical path of the blue laser light B emitted from the blue LD 11b. The convergent light from each of the condensing lenses 12r, 12g, and 12b has a substantially minimum beam diameter on the transmission screen 40. Each condensing lens 12r, 12g, 12b has an aspherical shape optimally designed according to the wavelength of laser light R, G, B from any of the LD groups 11 or an intermediate wavelength thereof. Each condensing lens 12r, 12g, 12b is comprised with the same lens, respectively. When the same lens is used for each condenser lens 12r, 12g, 12b, each LD 11r is adjusted by adjusting the distance between the light emitting point of each LD 11r, 11g, 11b and each condenser lens 12r, 12g, 12b. , 11g, and 11b, even if laser beams R, G, and B having different wavelengths are emitted, the laser beams can be condensed on the transmission screen 40.

  The polarization axis conversion element 13 is configured by a wave plate such as a 1 / 2λ plate, for example, and is installed on the optical path of the red laser light R. As shown in FIG. 6, the polarization axis conversion element 13 rotates the polarization axis Ip of the red laser light R by 90 ° about the optical axis Ia. Therefore, the polarization axis Ip of the red laser light R extends in the same direction as the polarization axes Ip of the green laser light G and the blue laser light B after passing through the polarization axis conversion element 13. However, since the polarization direction of the red laser light R does not change by the polarization axis conversion element 13, the longitudinal direction of the beam cross section Ab of the red laser light R is still the beam cross section Ab of the green laser light G and the blue laser light B. It extends in a direction perpendicular to the longitudinal direction.

  The light control unit 19 adjusts the amount of laser light after transmission, and includes a first polarizing plate 15, a liquid crystal element 16, and a second polarizing plate 17, as shown in FIG. .

  Specifically, the first polarizing plate 15 is installed in the optical path of the red laser light R that has passed through the polarization axis conversion element 13, the optical path of the green laser light G from the green LD 11g, and the optical path of the blue laser light B from the blue LD 11b. Is done. The first polarizing plate 15 has a direction along the polarization axis Ip of the red laser light R that has passed through the polarization axis conversion element 13 (the same as the polarization axis Ip of the green laser light G and the blue laser light B from the green LD 11g and the blue LD 11b). Direction) transmission axis Ib. The first polarizing plate 15 transmits only the light along the transmission axis Ib among the laser beams R, G, and B.

  The liquid crystal element 16 includes a liquid crystal layer and an electrode (not shown). The liquid crystal element 16 can change the directions of the polarization axes Ip of the laser beams R, G, and B by changing the arrangement of the liquid crystal molecules in the liquid crystal layer according to the voltage applied to the electrodes.

  As shown in FIG. 3, the second polarizing plate 17 is installed in the optical path of the synthetic laser light C from the photosynthesis unit 14 described later in detail. The transmission axis of the second polarizing plate 17 is orthogonal to the transmission axis Ib of the first polarizing plate 15. Here, the windshield 3 has a higher reflectance of the S-polarized wave than the P-polarized wave. For this reason, considering the visibility of the virtual image W, it is desirable that the windshield 3 is irradiated with light having a high ratio of the S-polarized component. Therefore, in this example, the transmission axis of the second polarizing plate 17 is set to coincide with the direction of the S polarization component of the windshield 3. The second polarizing plate 17 transmits only the light along the transmission axis of the second polarizing plate 17 in the synthetic laser light C. The light adjusting unit 19 can adjust the amount of the combined laser light C transmitted through the second polarizing plate 17 by changing the direction of the polarization axis Ip of each laser light R, G, B through the liquid crystal element 16.

  As shown in FIG. 3, the light combining unit 14 generates the combined laser light C by substantially aligning the optical axes Ia of the laser lights R, G, and B. Specifically, the light combining unit 14 includes dichroic mirrors 14r, 14g, and 14b. Each of the dichroic mirrors 14r, 14g, and 14b is made of a dielectric multilayer film having a different refractive index. The red dichroic mirror 14r reflects only the wavelength region of the red laser light R and transmits light in other wavelength regions. The dichroic mirror for green 14g reflects only the wavelength region of the green laser light G and transmits light in other wavelength regions. The blue dichroic mirror 14b reflects only the wavelength region of the blue laser light B and transmits light in other wavelength regions. The dichroic mirrors 14r, 14g, and 14b are arranged so that their reflected lights coincide with each other to generate the combined laser beam C.

  As shown in FIG. 3, the aperture member 18 is installed in the optical path of the synthetic laser light C that has passed through the second polarizing plate 17, and is provided with an opening (aperture) that is slightly larger than the mirror diameter of the MEMS scanner 20 described later. ing. The aperture member 18 shapes the synthetic laser light C according to the mirror of the MEMS scanner 20. Thereby, the occurrence of vignetting in the mirror of the MEMS scanner 20 is prevented. If vignetting occurs in the mirror of the MEMS scanner 20, light may be reflected from the hinge portion or the silicon substrate surface existing around the mirror surface 20a, resulting in stray light.

(Configuration of MEMS scanner, field lens and transmission screen)
As shown in FIG. 2, the MEMS scanner 20 includes a mirror surface 20a and is configured to be able to vibrate the mirror surface 20a. The MEMS scanner 20 may be a piezo type, an electromagnetic type, or an electrostatic type. The MEMS scanner 20 performs scanning while reflecting the synthetic laser light C emitted from the synthetic laser light generator 10 toward the transmission screen 40 by vibrating the mirror surface 20a. As a result, a display image M is generated on the upper surface of the transmissive screen 40.

  The field lens 30 is provided between the MEMS scanner 20 and the transmission screen 40, and makes the synthetic laser light C scanned by the MEMS scanner 20 incident on the transmission screen 40 at an incident angle corresponding to the scanning position. The field lens 30 is configured to optimize the incident angle of the synthetic laser light C on the transmission screen 40 according to the characteristics of the optical system (relay optical unit 50, windshield 3) after the transmission screen 40. .

  Under the control of the control unit 70, the MEMS scanner 20 reciprocates the synthetic laser light C along the main scanning direction H extending in the longitudinal direction of the rectangular transmission screen 40 as shown in FIG. The transmissive screen 40 is moved along the sub-scanning direction V extending in the short direction. Thereby, the scanning locus 500 forms a substantially sine wave along the sub-scanning direction V from the scanning start position Ya to the scanning end position Yb. The scanning start position Ya and the scanning end position Yb are respectively located at two corners of the transmission screen 40 located on the diagonal line. Based on the control by the control unit 70, the MEMS scanner 20 returns the synthetic laser light C from the scanning end position Yb to the scanning start position Ya after the synthetic laser light C reaches the scanning end position Yb. In this example, scanning for one frame refers to the period from when the combined laser beam C reaches the scanning end position Yd from the scanning start position Ya and then returns to the scanning start position Ya again. Specifically, as shown in FIG. 5, the MEMS scanner 20 performs scanning by shifting the scanning locus in the sub-scanning direction V by 1/2 of the pitch dV1 in the sub-scanning direction V of the microlens array 41 described later for each frame. To do. That is, the MEMS scanner 20 scans the synthetic laser light C along two alternately different scanning loci 500a and 500b. In this example, the MEMS scanner 20 performs scanning for one frame in 1/120 seconds, thereby scanning for 120 frames per second, that is, scanning at a high frequency of 120 Hz. For this reason, for the viewer, the two frames related to the two scanning trajectories 500a and 500b are substantially seen as one frame. The control unit 70 switches the display image M indicating numbers or symbols on the transmission screen 40 by switching between an ON state in which the synthetic laser light C is irradiated during scanning and an OFF state in which the synthetic laser light C is not irradiated. Generate. The main scanning direction H corresponds to the horizontal direction of the display image M, and the sub-scanning direction V corresponds to the vertical direction of the display image M.

  As shown in FIG. 4, the transmission screen 40 displays the display image M on the surface (the surface opposite to the MEMS scanner 20) based on the synthetic laser light C scanned by the MEMS scanner 20. Specifically, the transmission screen 40 enlarges the exit pupil (Exit Pupil) of the synthetic laser light C incident from the MEMS scanner 20 to display a display image M, and light L (display light L) representing the display image M is displayed. The light is emitted toward the relay optical unit 50. A specific configuration of the transmission screen 40 will be described later.

  As shown in FIG. 2, the relay optical unit 50 is provided between the light path between the transmission screen 40 and the windshield 3, and specifically includes two mirrors, a plane mirror 51 and a magnifying mirror 52. The plane mirror 51 is a planar total reflection mirror or the like, and reflects the light L representing the display image M transmitted through the transmission screen 40 toward the enlargement mirror 52.

  The magnifying mirror 52 is a concave mirror or the like, and reflects the reflected light toward the windshield 3 by reflecting the display light L reflected by the flat mirror 51 on the concave surface. As described above, since the display light L is light containing a large amount of S-polarized light components, the windshield 3 reflects the display light L toward the viewer with high reflectivity. The viewer can visually recognize the virtual image W in which the display image M is enlarged by receiving the display light L reflected by the windshield 3.

(Specific configuration of the transmission screen)
As shown in FIGS. 7A, 7B, and 8, the transmission screen 40 includes a microlens array 41 positioned on the incident side of the synthetic laser light C and an aperture array positioned on the emission side of the synthetic laser light C. 42. The microlens array 41 and the aperture array 42 are disposed so as to face each other. FIG. 8 is a diagram schematically showing a vertical cross section of the transmissive screen 40.

  As shown in FIG. 7A, the microlens array 41 includes rectangular microlenses 41a arranged in a matrix as viewed from the thickness direction. The microlenses 41a have a lens size of about 100 μm, for example, and are arranged with a pitch dH1 in the main scanning direction H and with a pitch dV1 in the sub-scanning direction V. In the present embodiment, the pitch dH1 in the main scanning direction H is larger than the pitch dV1 in the vertical direction, that is, a relationship of dH1> dV1 is established. The microlens array 41 is formed such that gaps and steps generated between adjacent microlenses 41a are minimized. Here, the pitch is the distance between the lens centers of the microlenses 41a adjacent to each other, and this pitch is hereinafter referred to as the “pitch of the microlens array 41”. In this example, as shown in FIGS. 12A to 12C, since the red laser light R has the longest wavelength, the beam diameter DV of the red laser light R as the synthetic laser light C on the transmission screen 40. , DH are larger than the beam diameters DV, DH of the blue laser light B and the green laser light G as the combined laser light C. When the beam diameters DV and DH are larger than the pitch of the microlens array 41, speckles and interference fringes may occur as described in the background art. For this reason, the pitch of the microlens array 41 needs to be determined based on the red laser beam R having the largest beam diameter. In consideration of the aspect ratio of the eye box 4, the pitch of the microlens array 41 is desirably a rectangular shape large in the main scanning direction H as shown in FIG.

  The aperture array 42 is formed of a material that absorbs visible light, and includes a plurality of openings 42a arranged in a matrix as seen from the thickness direction, as shown in FIG. 7B. The plurality of openings 42a are provided corresponding to the microlenses 41a of the microlens array 41, and are formed so as to penetrate the aperture array 42 in the thickness direction. The plurality of openings 42a are periodically arranged at a pitch dHA in the main scanning direction H and at a pitch dVA in the sub-scanning direction V. The plurality of openings 42a are formed by a photolithography technique or the like. Here, the pitch is the distance between the centers of the openings 42a adjacent to each other, and this pitch is hereinafter referred to as the “pitch of the aperture array 42”.

  In the present embodiment, the pitch dHA in the main scanning direction H is larger than the pitch dVA in the sub-scanning direction V, that is, the relationship dHA> dVA is established. Further, the pitch dHA of the aperture array 42 in the main scanning direction H is slightly larger than the pitch dH1 of the microlens array 41 in the main scanning direction H, that is, a relationship of dHA> dH1 is established.

  The opening 42a of the aperture array 42 is formed so that the size thereof is about 1/5 to 1/10 of the lens size of the micro lens 41a when viewed from the thickness direction of the aperture array 42. As described above, the aperture array 42 is formed of a material that absorbs visible light, such as a black resist used in a liquid crystal panel, for example. For this reason, the area other than the opening 42a of the aperture array 42 functions as a light shielding part 42b. Therefore, most of the laser light that has reached the aperture array 42 is absorbed by the light shielding portion 42b except for the light that passes through the opening 42a.

  As shown in FIG. 8, the microlens array 41 and the aperture array 42 are arranged in the thickness direction with a distance of the focal length f of the microlens 41 a. The microlens 41a positioned at the center of the microlens array 41 when the microlens array 41 is viewed from the thickness direction and the center of the opening 42a positioned at the center of the aperture array 42 when viewed from the thickness direction are the same light. A microlens array 41 and an aperture array 42 are installed so that the axis AX passes through. Moreover, the condensing point P of the synthetic laser light C by the microlens array 41 is located at the center of each opening 42a. Since the synthetic laser light C is thus focused on the openings 42a of the aperture array 42, each laser light R, G, B emitted from the LD group 11 is efficiently converted into light L representing the display image M. Can do. Even when external light entering from the outside of the HUD device 1 propagates in the reverse direction of the optical path of the laser light, most of the external light is absorbed by the light shielding portion 42 b of the aperture array 42. Therefore, external light reflection is significantly reduced. By providing the light shielding part 42b in this manner, it is possible to suppress the external light diffused and reflected by the transmissive screen 40 from reaching the viewer's eyes through the optical path of the HUD device 1, and as a result, the transmissive screen 40 overlaps the display image M. It is suppressed that the visibility rises in a white frame shape.

  Of the synthetic laser light C that has reached the transmission screen 40, most of the light other than the light L representing the display image M that passes through the openings 42 a of the aperture array 42 is absorbed by the light shielding portion 42 b of the aperture array 42. Is done. Therefore, reflection of the synthetic laser beam C toward the field lens 30 by the transmission screen 40 is also suppressed. The synthetic laser light C refracted by the microlens 41a of the microlens array 41 diverges through the opening 42a of the aperture array 42 and then illuminates the eye box 4 through the relay optical unit 50 and the like.

(Light distribution intensity distribution in the main scanning direction)
Next, the light distribution intensity distribution in the eye box 4 when the synthetic laser light C moves in the main scanning direction H will be described with reference to FIGS.

  When the synthesized laser light C is scanned in the main scanning direction H with respect to one micro lens 41a, different light distribution intensity distributions are obtained as shown in the lower right graphs of FIGS. 9 (a) to 9 (e). It is done. When these different light distribution intensity distributions are integrated by the time for scanning one microlens 41a in the main scanning direction H, as shown in FIG. 10, it is substantially uniform throughout the main scanning direction H in the eye box 4. A light distribution intensity distribution can be formed.

(Light distribution intensity distribution in the sub-scanning direction)
Next, the light distribution intensity distribution in the eye box 4 in the sub-scanning direction V will be described with reference to FIGS.

  When the synthetic laser beam C is scanned through the first scanning locus 500a, when the synthetic laser beam C is irradiated near the center of the microlens 41a, as shown in FIG. The light distribution intensity distribution of the synthetic laser beam C in the inside is almost Gaussian. In the next frame, when the synthetic laser light C is scanned through the second scanning locus 500b, when the synthetic laser light C is irradiated near the boundary between the two microlenses 41a, FIG. ), The light distribution intensity distribution of the synthetic laser light C in the eye box 4 is a light distribution intensity distribution having two peaks. Here, since scanning for 120 frames per second is performed at a high speed, the viewer adds the light distribution intensity distribution of FIG. 11A and the light distribution intensity distribution of FIG. Light having a substantially uniform intensity distribution as shown in FIG.

(Beam diameter in the sub-scanning direction)
12A to 12C show the beam shapes Rf, Gf, and Bf of the laser beams R, G, and B on the transmission screen 40. FIG. Each of the laser beams R, G, and B is a synthetic laser beam C composed of a single color of red, green, or blue. The beam shapes Rf, Gf, and Bf of the laser beams R, G, and B are elliptical shapes having a beam diameter DH in the main scanning direction H and a beam diameter DV in the sub-scanning direction V. As described above, the red laser light R has a longer wavelength than the green laser light G and the blue laser light B. For this reason, the beam shape Rf of the red laser light R is larger in size than the beam shape Gf of the green laser light G and the beam shape Bf of the blue laser light B. That is, the beam diameters DH and DV of the red laser light R are larger than the beam diameters DH and DV of the green laser light G and the blue laser light B. In the present embodiment, as described above, the red LD 11r is installed in a direction rotated by 90 ° about the optical axis Ia with respect to the green LD 11g and the blue LD 11b. Thereby, as shown in FIG. 12A, the beam shape Rf of the red laser light R has a longitudinal direction along the main scanning direction H, and the beam shape Gf of the green laser light G and the beam shape of the blue laser light B. The longitudinal direction of Bf is along the sub-scanning direction V. That is, the direction of the beam shape Rf of the red laser light R differs from the direction of the beam shapes Gf and Bf of the green laser light G and the blue laser light B by 90 °. The beam diameter of the red laser beam R in the short direction (in this example, the beam diameter DV in the sub-scanning direction V) and the beam diameter in the longitudinal direction of the green laser beam G or blue laser beam B (in this example, in the main scanning direction H). The difference from the beam diameter DV) is relatively small. For this reason, by arranging the LDs 11r, 11g, and 11b as described above, the difference in the beam diameter DV in the sub-scanning direction V between the laser beams R, G, and B can be reduced.

  12 (d), (e) and (f) show the light distribution intensity distribution in each of the laser beams R, G and B corresponding to FIG. 11 (a), and FIG. 12 (g), (h) and FIG. (I) shows the light distribution intensity distribution in each of the laser beams R, G, and B corresponding to FIG. 11 (b), and FIGS. 12 (j), (k), and (l) show FIG. 11 (c). 12 (d), (e), and (f), and FIGS. 12 (g), (h), and (i), respectively, are added to each other to show light distribution intensity distributions. As described above, by reducing the difference between the beam diameters DV of the laser beams R, G, and B in the sub-scanning direction V, as shown in FIGS. 12 (j), (k), and (l), Almost the same intensity light distribution is obtained among the lights R, G, and B.

  By the way, by arranging the LDs 11r, 11g, and 11b as described above, the difference between the beam diameter DH of the red laser light R in the main scanning direction H and the beam diameters DH of the green laser light G and the blue laser light B is as follows. Compared to the prior art. However, when the synthetic laser beam C is scanned by the MEMS scanner 20, since the synthetic laser beam C continuously moves in the main scanning direction H, the light distribution intensity distribution in the eye box 4 formed by time integration is all. A substantially uniform light distribution intensity distribution is obtained. For this reason, the difference in the beam diameter DH in the main scanning direction H has almost no influence on the display image M.

(effect)
As mentioned above, according to one Embodiment described, there exist the following effects.

  (1) The HUD device 1 includes a green LD 11g that emits green laser light G, a blue LD 11b that emits blue laser light B, and a red LD 11r that emits red laser light R having a longer wavelength than the green laser light G and blue laser light B. And a laser beam synthesis unit 14 that synthesizes the laser beams R, G, and B from the laser diodes 11r, 11g, and 11b to generate a synthesized laser beam C, and the synthesized laser beam C on the transmission screen 40 along the scanning direction H. And a MEMS scanner 20 that performs scanning so as to move in the sub-scanning direction V orthogonal to the scanning direction H. A beam cross section Ab obtained by cutting each laser beam R, G, B from each LD 11r, 11g, 11b in a direction perpendicular to the optical axis Ia of the laser beams R, G, B is an ellipse having a longitudinal direction and a short direction. It is a shape. The green LD 11g and the blue LD 11b are installed such that the longitudinal direction of the beam cross section Ab of the green laser light G and the blue laser light B corresponds to the sub-scanning direction V. In the red LD 11r, when viewed from the direction along the optical axis Ia of the red laser light R from the red LD 11r, the longitudinal direction of the beam cross section Ab of the red laser light R is the beam cross section Ab of the green laser light G and the blue laser light B. It is installed in the direction that intersects the longitudinal direction.

  In general, the longer the wavelength of light, the larger the beam diameter of the light on the transmission screen 40. By disposing the LDs 11r, 11g, and 11b as described above, as shown in FIGS. 12A to 12C, the longitudinal direction of the beam shape Rf of the red laser light R, the green laser light G, and the blue laser The beam shapes Gf and Bf of the light B are set at different angles from the longitudinal direction. As a result, the beam diameter DV of the red laser light R in the sub-scanning direction V approaches the beam diameter DV of the green laser light G and the blue laser light B in the sub-scanning direction V. By reducing the difference in the beam diameter DV of each color laser beam R, G, B in the sub-scanning direction V, the intensity of light emitted from the transmission screen 40 is made uniform for each color laser beam R, G, B. Is done. For this reason, when the viewer views the virtual image W, it is suppressed that the viewer perceives luminance unevenness or color unevenness.

  (2) Further, the HUD device 1 is provided corresponding to each of the red LD 11r, the green LD 11g, and the blue LD 11b, and converts the corresponding laser beams R, G, and B from the diffused light to the convergent light, respectively. Are provided with three condensing lenses 12r, 12g, and 12b. By using the same lens as each condensing lens 12r, 12g, 12b, it is possible to prevent mistakes when arranging the condensing lenses 12r, 12g, 12b, and to contribute to cost reduction through the common use of parts. it can. Further, even when a plurality of condensing lenses 12r, 12g, and 12b having the same configuration is used, by arranging the LDs 11r, 11g, and 11b as described above, each color laser beam in the sub-scanning direction V is provided. The difference in beam diameter DV between R, G, and B can be reduced.

  (3) The HUD device 1 includes a polarization axis conversion element 13 that converts the respective polarization axes Ip of the laser beams R, G, and B in the same direction, and the polarization axis Ip that passes through the polarization axis conversion element 13 in the same direction. A dimming unit 19 for dimming the combined laser beam C relating to the converted laser beams R, G, and B. According to this configuration, when the polarization axes Ip of the laser beams R, G, and B are converted in the same direction, the dimming unit 19 has the first polarizing plate 15 and the second polarizing plate 17 respectively. Dimming can be performed uniformly between the laser beams R, G, and B due to the relationship of the transmission axes. In particular, the light can be efficiently guided to the eye box 4 by matching the polarization axes Ip of the laser beams R, G, and B with the direction in which the reflectance at the windshield 3 is high.

  (4) In the red LD 11r, when viewed from the direction along the optical axis Ia of the red laser light R, the longitudinal direction of the beam cross section Ab of the red laser light R is the longitudinal direction of the beam cross section Ab of the green laser light G and the blue laser light B. Installed in a direction perpendicular to the direction. Thereby, the difference between the beam diameter DV of the red laser light R in the sub scanning direction V and the beam diameter DV of the green laser light G and the blue laser light B in the sub scanning direction V can be minimized. As a result, unevenness in intensity of light emitted from the transmission screen 40 is reduced and uniformized for each color laser beam R, G, and B. Feeling as unevenness is further suppressed.

  (5) The second polarizing plate 17 in the light control unit 19 is provided in the optical path of the combined laser light C from the light combining unit 14. By providing the second polarizing plate 17 at this position, the second polarizing plate 17 needs only to have a size capable of transmitting one synthetic laser beam C. Therefore, the second polarizing plate 17 can be made compact. Can do.

(Modification)
In addition, the said embodiment can be implemented with the following forms which changed this suitably.

  In the embodiment described above, the polarization axis conversion element 13 changes the polarization axis Ip of each of the laser beams R, G, and B in the same direction by changing the direction of the polarization axis Ip of the red laser beam R. However, the polarization axis conversion element 13 is not limited to this as long as it can convert the polarization axes Ip of the laser beams R, G, and B in the same direction. For example, the polarization axis conversion element 13 converts the polarization axes Ip of the green laser beam G and the blue laser beam B. It may be changed. Further, the polarization axis conversion element 13 rotates the polarization axes Ip of the laser beams R, G, and B by 45 ° about the optical axis Ia so that the polarization axes Ip of the laser beams R, G, and B are in the same direction. May be converted to Further, the polarization axis conversion element 13 may be a circularly polarizing plate that converts each of the laser beams R, G, and B from linearly polarized light to circularly polarized light.

  In the synthetic laser light generation apparatus 10 of the above embodiment, the condenser lens group 12, the polarization axis conversion element 13, the light control unit 19, or the diaphragm member 18 may be omitted as appropriate.

  In the above embodiment, the red LD 11r is installed in a direction rotated by 90 ° about the optical axis Ia with respect to the green LD 11g and the blue LD 11b. However, the red LD 11r may be other than 90 ° as long as the red LD 11r is oriented in a different direction around the optical axis Ia with respect to the green LD 11g and the blue LD 11b. That is, in the red LD 11r, when viewed from the optical axis Ia of the red laser light R emitted from the red LD 11r, the longitudinal direction of the beam cross section Ab in which the red laser light R spreads is in the longitudinal direction of the beam cross section Ab in which the laser lights G and B spread. As long as it is installed in the intersecting direction, these longitudinal directions do not necessarily have to be orthogonal.

  Of the red LD 11r, green LD 11g, and blue LD 11b in the above embodiment, the green LD 11g or the blue LD 11b may be omitted. The red LD 11r is not limited to red as long as it has a longer wavelength than other LDs. Further, the green LD 11g or the blue LD 11b is not limited to the color as long as the wavelength is shorter than that of the red LD 11r.

  In the above embodiment, the second polarizing plate 17 is provided in the optical path of the combined laser light C from the light combining unit 14, but not limited to this, each laser light R, G, It may be provided in the optical path B. Further, all the configurations of the light control unit 19 may be provided in the optical path of the synthetic laser light C.

  In the above embodiment, the microlens array 41 is configured by arranging rectangular microlenses 41a in a lattice shape, but the shape of the microlenses may be square. The microlens array may be configured by arranging hexagonal microlenses in a honeycomb shape.

  In the above embodiment, the control unit 70 is built in the housing 60 of the HUD device 1, but may be provided outside the housing 60.

  In the above embodiment, the transmissive screen 40 includes the aperture array 42. However, the aperture array 42 may be omitted and the transmissive screen 40 may be configured by only the microlens array 41.

  In the above embodiment, the microlens array 41 is provided only on the incident side of the aperture array 42. However, a similar microlens array is provided on the exit side of the aperture array 42 as a so-called dual-microlens array. It may be configured.

  In the above embodiment, each of the condensing lenses 12r, 12g, and 12b is composed of the same lens. However, the condensing lenses 12r, 12g, and 12b may have different configurations according to the wavelengths of the corresponding laser beams R, G, and B. .

  In the above embodiment, the display device according to the present invention is applied to a vehicle-mounted head-up display device. However, the display device is not limited to a vehicle-mounted device, and may be applied to a head-up display device mounted on a vehicle such as an airplane or a ship. . Further, the HUD device 1 may project the light L representing the display image M on a dedicated combiner instead of the windshield 3. Further, the display device according to the present invention may be applied not to a head-up display device but to a display device such as a projector used indoors or outdoors. Further, the projection member is not limited to a light-transmitting member, and may be a reflective screen or the like. Further, for example, the display device according to the present invention may be mounted on a glasses-type wearable terminal.

DESCRIPTION OF SYMBOLS 1 ... HUD apparatus 2 ... Vehicle 3 ... Windshield 4 ... Eye box 10 ... Synthetic laser beam generator 11 ... LD group 11r ... Red LD
11g ... Green LD
11b ... Blue LD
DESCRIPTION OF SYMBOLS 12 ... Condensing lens group 12r, 12g, 12b ... Condensing lens 13 ... Polarization axis conversion element 14 ... Photosynthesis part 14r, 14g, 14b ... Dichroic mirror 15 ... 1st polarizing plate 16 ... Liquid crystal element 17 ... 2nd polarization | polarized-light Plate 18 ... Diaphragm member 20 ... MEMS scanner 20a ... Mirror surface 30 ... Field lens 40 ... Transmission screen 41 ... Micro lens array 41a ... Micro lens 42 ... Aperture array 42a ... Opening 42b ... Light shielding part 50 ... Relay optical part R ... Red Laser beam G ... Green laser beam B ... Blue laser beam C ... Synthetic laser beam W ... Virtual image

Claims (4)

A first laser light source emitting a first laser beam;
A second laser light source that emits a second laser light having a longer wavelength than the first laser light;
A photosynthesis unit that synthesizes the first laser beam and the second laser beam to generate a synthesized laser beam;
A scanning section that scans the synthetic laser light so as to move in a sub-scanning direction orthogonal to the scanning direction while reciprocating along the scanning direction on the screen,
When the first laser beam and the second laser beam are cut in a direction perpendicular to the optical axes of the first laser beam and the second laser beam, respectively, the first laser beam and the second laser beam have a longitudinal direction and a short direction. With an elliptical beam cross section,
The first laser light source is installed so that the longitudinal direction of the beam cross section in the first laser light corresponds to the sub-scanning direction on the screen,
The second laser light source has a longitudinal direction of the beam cross section of the second laser light that is the longitudinal direction of the beam cross section of the first laser light, as viewed from the direction along the optical axis of the second laser light. Installed in the direction that intersects the longitudinal direction,
A display device characterized by that. The first laser light source is at least one of a blue laser light source emitting blue laser light and a green laser light source emitting green laser light,
The second laser light source is a red laser light source that emits red laser light,
The same configuration is provided corresponding to each of the red laser light source, the green laser light source, and the blue laser light source, and converts the red laser light, the green laser light, and the blue laser light from diffused light to convergent light, respectively. With three condenser lenses consisting of
The display device according to claim 1. A polarization axis conversion element that converts the polarization axes of the red laser light, the green laser light, and the blue laser light in the same direction;
A dimming unit for dimming the red laser light, the green laser light, the blue laser light, or the synthetic laser light, the polarization axis of which has been converted in the same direction through the polarization axis conversion element,
The display device according to claim 2. The red laser light source has a longitudinal direction of the beam cross section in the red laser light in a longitudinal direction of the beam cross section in the green laser light or the blue laser light as viewed from a direction along the optical axis of the red laser light. Installed in an orthogonal orientation,
The display device according to claim 2, wherein the display device is a display device.