CN216927274U

CN216927274U - Head-up display

Info

Publication number: CN216927274U
Application number: CN202220771004.XU
Authority: CN
Inventors: 江塚敏晴
Original assignee: Nippon Seiki Co Ltd
Current assignee: Nippon Seiki Co Ltd
Priority date: 2021-06-10
Filing date: 2022-04-02
Publication date: 2022-07-08
Anticipated expiration: 2032-04-02
Also published as: JP2022188796A

Abstract

The utility model provides a head-up display which suppresses reduction in display quality of a virtual image of the head-up display. A head-up display (H) is provided with: a light source unit (11) that emits laser light (SL); a screen (13) that is disposed so as to be inclined by a first angle (θ) with respect to an optical axis of the laser light (SL) and that is irradiated with the laser light (SL); and an optical unit (12) disposed on the optical path of the laser light (SL) between the light source unit (11) and the screen (13), wherein the head-up display (H) projects display light (PL) emitted from the screen (13) onto a Holographic Optical Element (HOE) and displays a virtual image (V). The optical unit (12) further includes an aspheric lens (126) having an aspheric coefficient corresponding to the first angle (θ).

Description

Head-up display

Technical Field

The present invention relates to a head-up display that displays vehicle information.

Background

Patent document 1 discloses a head-up display that displays vehicle information by a virtual image of light diffracted by a Holographic Optical Element (HOE).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. Hei 7-92892

The hologram optical element is formed with interference fringes and is irradiated with set reproduction light (light having a wavelength corresponding to the interference fringes) to obtain desired diffracted light. Therefore, when light having a wavelength different from the wavelength of the reproduction light is irradiated to the hologram optical element, stray light (reflection and scattering of unnecessary light) occurs, and the display quality of the virtual image of the head-up display is degraded.

SUMMERY OF THE UTILITY MODEL

An object of the present disclosure is to suppress a reduction in display quality of a virtual image of a head-up display.

The present disclosure achieves the above object by a head-up display having the following structure.

The disclosed head-up display is provided with:

a light source unit that emits laser light;

a screen that is disposed so as to be inclined at a first angle with respect to an optical axis of the laser light and is irradiated with the laser light; and

an optical unit disposed on an optical path of the laser beam between the light source unit and the screen,

the head-up display projects display light emitted from the screen to the hologram optical element and displays a virtual image,

the optical unit has an aspherical lens having an aspherical surface coefficient corresponding to the first angle.

Effect of the utility model

According to the present disclosure, it is possible to suppress a reduction in display quality of a virtual image of a head-up display.

Drawings

Fig. 1 is a diagram showing a structure of a head-up display.

Fig. 2 is a diagram showing a configuration of the image display unit.

Fig. 3 is a comparison diagram of light distribution characteristics of liquid crystal panels arranged at different tilt angles θ.

Fig. 4 is a graph comparing light distribution characteristics of the image display unit before (before) application of the aspherical lens and after (after) application.

Fig. 5 is a diagram showing a relationship between "inclination angle θ of the liquid crystal panel" and "aspherical coefficient of the aspherical lens".

Description of the symbols

H head-up display

1 image display part

11 light source unit

12 optical part

121 scanning mirror

122 beam steering part

123 fly-eye lens

124 condenser lens

125 objective lens

126 cylindrical lens with aspherical lens

127 diffusion plate

13 LCD panel (Screen)

2 reflecting mirror

3 case

31 light-transmitting dustproof cover

32 light shielding wall

WS windshield

HOE holographic optical element

P hitchhiker

PL display light

SL synthetic light (synthetic laser)

Virtual image of V

Detailed Description

The head-up display H of the present disclosure will be explained below with reference to the drawings. The head-up display H is an in-vehicle instrument that is incorporated in an instrument panel of a vehicle and displays various vehicle information such as a traveling speed of the vehicle and route guidance information.

Supplementing the description of the figures. The direction indicated by the symbol Y corresponds to the vertical direction (vertical direction) of the vehicle. The direction indicated by the symbol Z corresponds to the front-rear direction of the vehicle.

See fig. 1. The head-up display H includes: an image display unit 1, a mirror 2, and a housing 3. The head-up display H projects the display light PL output from the image display unit 1 to a hologram optical element HOE provided on a windshield WS of the vehicle. The hologram optical element HOE reflects diffracted light obtained by diffracting the display light PL toward the occupant P of the vehicle. This allows the passenger P to visually recognize the virtual image V representing the vehicle information in front of the windshield WS.

The image display unit 1 is a display for displaying an image representing vehicle information by numerical values, figures, and the like, and emitting display light PL from the image. The detailed configuration of the image display unit 1 will be described later.

The mirror 2 is, for example, a concave mirror. The mirror 2 reflects the display light PL emitted from the image display unit 1 and turns the light back in the housing 3 to increase the optical path length of the display light PL, and as a result, the virtual image V can be formed at a distance from the windshield WS. The mirror 2 has a free-form surface shape that cancels the deformation of the virtual image V due to the curved shape of the windshield WS, and suppresses the influence of the deformation of the virtual image V due to the curved shape of the windshield WS. The reflecting mirror 2 is not limited to one concave mirror, and the light may be folded by two mirrors, i.e., a plane mirror and a concave mirror.

The housing 3 is a box body formed with an exit port for emitting the display light PL. The housing 3 accommodates the image display unit 1, the mirror 2, and the control circuit board. The case 3 is molded from, for example, black opaque resin or metal. The exit port of the housing 3 is covered with a light-transmitting dust cap 31 having a thickness of 0.5 to 2mm (millimeters). The light-transmitting dust cover 31 is a film made of a resin such as an acrylic resin or a polycarbonate resin. Further, a light shielding wall 32 for preventing external light (external light) (mainly sunlight) EL incident from the exit port from directly entering the image display unit 1 is formed inside the housing 3 in the vicinity of the exit port.

The hologram optical element HOE is a reflective hologram film on which interference fringes corresponding to a specific wavelength are recorded. The hologram optical element HOE is provided to the windshield WS. The specific wavelength is the wavelength of the three primary colors of blue, red, and green light. Hereinafter, blue refers to light having a central wavelength of about 632 nm. Red refers to light having a central wavelength of about 488 nm. Green refers to light having a central wavelength of about 532 nm.

(construction of image display section 1)

See fig. 2. The image display unit 1 includes: a light source unit 11, an optical unit 12, and a liquid crystal panel (screen) 13.

The light source unit 11 is a backlight for irradiating the liquid crystal panel 13. The light source unit 11 includes: laser light sources 111 to 113 and a combining unit. The combining unit is composed of a first combining unit 114, a second combining unit 115, and a third combining unit 116, which will be described later.

The laser light source 111 is a laser diode that emits the blue laser light B. The laser light source 111 emits the blue laser light B toward the first combining portion 114.

The laser light source 112 is a laser diode that emits the red laser light R. The laser light source 112 emits the red laser beam R toward the second combining part 115.

The laser light source 113 is a laser diode that emits green laser light G. The laser light source 113 emits the green laser beam G toward the third synthesis unit 116.

The first combining unit 114 is a dichroic mirror that reflects only blue light. The first combining unit 114 reflects the blue laser beam B emitted from the laser light source 111 toward the second combining unit 114.

The second combining unit 115 is a dichroic mirror that reflects red light and transmits blue light. The second combining unit 115 transmits the blue laser beam B reflected by the first combining unit 114 toward the third combining unit 116, and reflects the red laser beam R emitted from the laser light source 112 toward the third combining unit.

The third synthesis unit 116 is a dichroic mirror that reflects green light and transmits red light and blue light. The third combining unit 116 transmits the blue laser beam B transmitted by the second combining unit and the red laser beam R reflected by the second combining unit, and reflects the green laser beam G emitted from the laser light source 113.

With the above configuration, the light source unit 11 emits the combined light SL, which is obtained by combining the laser light R, G, B emitted from the laser light sources 111 to 113 by the combining units 114 to 116, toward the optical unit 12.

The optical unit 12 is an optical member that reflects, refracts, converges, and diverges the combined light SL emitted from the light source unit 11 in the process of reaching the liquid crystal panel 13. The optical unit 12 is described in the order of being disposed on the light source unit 11 side, and is composed of a scanning mirror 121, a beam steering unit 122, a fly-eye lens 113, a condenser lens 114, an objective lens 115, a lenticular lens 116, and a diffuser plate 117.

The scanning mirror 121 is a mirror that reflects the combined light SL emitted from the light source unit 11 so as to perform two-dimensional scanning toward the light beam steering unit 122. The scanning Mirror 121 is a two-dimensional scanning Mirror such as a MEMS (Micro Electro Mechanical System) Mirror or a VCM (Voice Coil Mirror).

The beam steering section 122 is a lens that refracts the incident combined light SL and irradiates the fly-eye lens 113. The beam steering section 122 is constituted by a pair of wedge prisms and a rotation mechanism that rotates these wedge prisms. The angle of refraction of the combined light SL is controlled by rotating the wedge prism.

The fly-eye lens (integrator lens) 123 is a lens in which a plurality of lenses are arranged in a matrix. The fly-eye lens 123 generates as many multiple images as the number of lenses configured, thereby making the light from the point light source of the light source unit 11 close to a uniform illuminance distribution of surface illumination (planar illumination).

The condenser lens 124 and the objective lens 125 are a pair of lenses constituting Koehler illumination (Koehler illumination). The condenser lens 124 and the objective lens 125 are also lenses for achieving an illumination distribution close to uniform surface illumination, similarly to the fly-eye lens 123.

The lenticular lens 126 is a lens having a predetermined aspherical lens, and suppresses adverse effects on light distribution characteristics due to an inclination angle θ of a liquid crystal panel described later. Details of the aspherical lens will be described later.

The diffusion plate 127 disperses the light of the combined light SL passing through the lenticular lens 126, preventing the generation of hot spots of light.

The liquid crystal panel 13 is a TFT (Thin Film Transistor) type liquid crystal panel. The liquid crystal panel 13 displays a figure or a numeral indicating vehicle information as an image, and emits display light PL from the displayed image by irradiating the synthesized light SL from the back surface.

The liquid crystal panel 13 is inclined in the Y direction with respect to a principal ray passing through the aperture center of the combined light SL emitted from the light source unit 11. The inclination angle is defined as a first angle θ.

The first angle θ is set so that the external light EL reflected by the reflector 2 is reflected by the liquid crystal panel 13 and directed to the back surface of the light shielding wall of the housing 3. This prevents the external light EL reflected by the reflector 2 from being reflected by the liquid crystal panel 13, reflected by the reflector 2 again, and emitted from the exit port of the housing 3. When the liquid crystal panel 13 is not disposed obliquely (the first angle θ is 0 °), the external light EL reflected by the mirror 2 is reflected by the liquid crystal panel 13, and then reflected by the mirror 2 and emitted from the exit port of the housing 3 to become stray light. This stray light is irradiated to the hologram optical element HOE together with the display light PL, and therefore, causes a reduction in the display quality of the virtual image V.

As described above, the liquid crystal panel 13 is disposed obliquely to prevent stray light caused by the external light EL.

Fig. 3 shows the result of comparing the light distribution characteristics of example a in which the first angle θ is 0 ° and example B in which the first angle θ is 30 °. In fig. 3, the ordinate represents the intensity ratio of the display light PL emitted from the liquid crystal panel 13 when the intensity of the combined light SL emitted from the light source unit 11 is 100%, and the abscissa represents the scattering angle.

As shown in fig. 3, the inventors of the present disclosure found that the larger the first angle θ, the more the decrease in the intensity of the display light PL emitted from the liquid crystal panel 13 and the increase in the scattering angle occur. In particular, the inventors of the present disclosure have found the following problems: when the scattering angle increases, the display light PL contains a large amount of light deviated from the light having the wavelength corresponding to the interference fringe formed on the hologram optical element HOE, and therefore stray light (reflection and scattering of unnecessary light) is generated in the diffracted light emitted from the hologram optical element HOE, and the display quality of the virtual image of the head-up display is degraded.

In order to suppress stray light caused by the above-described inclined arrangement of the liquid crystal panel 13, the aspherical coefficient of the aspherical lens of the lenticular lens 126 is set based on the first angle θ of the liquid crystal panel 13. Further, the aspherical coefficient of the aspherical lens relates to the lens shape of the lens in the direction orthogonal to the tilt direction of the liquid crystal panel 13. The aspherical lens has an asymmetric shape in the entire surface so that the emission surface is in the opposite direction to the inclination of the liquid crystal panel 13.

With the above-described aspherical lens, as shown in fig. 4, the light distribution characteristics of the configuration (rear) in which the aspherical coefficient of the aspherical lens of the lenticular lens 126 is set based on the first angle θ of the liquid crystal panel 13 are improved compared to the configuration (front) before the application of the aspherical lens. Specifically, when the intensity of the combined light SL emitted from the light source unit 11 is set to 100%, the intensity ratio (Relative Power) of the display light PL emitted from the liquid crystal panel 13 increases. Further, the scattering angle of the display light PL emitted from the liquid crystal panel 13 is reduced.

The aspherical coefficient of the aspherical lens of the lenticular lens 126 becomes an aspherical coefficient shown in fig. 5 according to the first angle θ of the liquid crystal panel 13, and thus stray light due to the inclined arrangement of the liquid crystal panel 13 can be suppressed.

As shown in AC (3th) of fig. 5, in the case of a three-dimensional aspheric surface, the light distribution characteristics can be improved by setting the three-dimensional aspheric surface coefficient to be smaller in inverse proportion to the first angle θ. That is, it is preferable to set the aspherical surface coefficient of the odd dimension to be smaller in inverse proportion to the first angle θ.

As shown in AC (4th) of fig. 5, in the case of a four-dimensional aspheric surface, the light distribution characteristics can be improved by setting the four-dimensional aspheric surface coefficient to be larger in proportion to the first angle θ. That is, it is preferable to set the even-dimensional aspheric coefficient to be larger in proportion to the first angle θ.

The aspherical surface coefficient of the aspherical lens of the lenticular lens 126 is preferably 80% or more when the intensity ratio of the display light PL emitted from the liquid crystal panel 13 is within a range of ± 3deg with respect to the intensity of the combined light SL emitted from the light source unit 11 being 100%, and is less than 40% when the scattering angle is outside the range of ± 4.5 deg. By setting the aspherical coefficient to satisfy such a condition, stray light caused by the oblique arrangement of the liquid crystal panel 13 can be suppressed.

The above is a description of an embodiment of the head-up display H of the present disclosure. The head-up display H of the present disclosure is not limited to the above-described embodiment, and the following modifications may be made.

In the present embodiment, the lenticular lens 126 has a structure having an aspherical lens based on the first angle θ, but is not limited thereto. For example, a lens such as fly-eye lens 123 may have such an aspherical lens configuration. Of the lens groups applied to the optical portion 12, the lens closest to the back surface of the liquid crystal panel 13 as in the present embodiment is preferable.

The lenticular lens 126 may be disposed to be inclined by the first angle θ in the Y direction with respect to the principal ray passing through the aperture center of the combined light SL emitted from the light source unit 11, as in the liquid crystal panel 13. That is, the liquid crystal panel may be disposed substantially in parallel with the liquid crystal panel 13. In this case, in designing the aspherical lens based on the first angle θ of the lenticular lens 126, it becomes easy to uniformly irradiate the liquid crystal panel 13.

Claims

1. A head-up display is characterized by comprising:

a light source unit that emits laser light;

the head-up display projects display light exiting from the screen to a holographic optical element and displays a virtual image,

the optical unit has an aspherical lens having an aspherical coefficient corresponding to the first angle.

2. Head-up display according to claim 1,

the aspherical lens is an odd-dimensional aspherical lens set such that the aspherical coefficient becomes smaller in inverse proportion to the magnitude of the first angle.

3. Head-up display according to claim 1,

the aspherical lens is an even-numbered aspherical lens in which the aspherical coefficient is set to be larger in proportion to the magnitude of the first angle.

4. Head-up display according to any one of claims 1 to 3,

the intensity of the display light emitted from the screen is 80% or more of the intensity of the laser light in a range where the scattering angle is ± 3deg, and the intensity of the light outside the range where the scattering angle is ± 4.5deg is less than 40% of the intensity of the laser light.

5. Head-up display according to claim 4,

the screen is a liquid crystal panel which is,

the aspherical lens is a cylindrical lens.