JP2001075513A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device which is capable of lessening the unsharpness at the edges of a ray image and improving the display quality of the ray image. SOLUTION: This display device 10 has an optical element 11 which is periodically formed with plural projecting line-like microoptical elements 12 having prescribed surfaces 12b on their outer peripheries concentrically on a rear surface side and plural light sources 14 which are disposed regularly in a circumferential direction on the rear surface side of the optical element 11 such that the ray image extending from the curvature center side of the microoptical elements 12 toward a radiation direction corresponding to the lighting light sources 14 by the light L projected from the respective light sources 14 is formed. This display device 10 is set at <=0.2 μm in the arithmetic average roughness (Ra) on the surface (more particularly the surfaces of the microoptical elements 12) of the optical element 11, by which the scattering of the unnecessary light L to give rise to the unsharpness at the edges of the ray image is suppressed and the unsharpness at the edges of the ray image is drastically reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for optically generating a pseudo pointer.

[0002]

2. Description of the Related Art In general, in a conventional display device, a pointer is mechanically rotated to display a vehicle speed or the like.

[0003]

However, the conventional display device requires a complicated driving mechanism for rotating the hands, and has a problem that the device configuration is complicated.

[0004] Therefore, the inventors of the present application, although not known, have shown a plurality of ridge-shaped micro optical elements on the back side (left side in FIG. 12) of a flat optical element 100 as shown in FIG. 101 is formed concentrically and its optical element 1
A display device in which the light source 102 is disposed on the back side of the P.00 is being developed.

[0005] Each of the micro optical elements 101 is an optical element 1
It has a vertical prism surface 101a perpendicular to the surface direction 00 and a curved prism surface 101b having a substantially arc-shaped cross section, and has a substantially fan-shaped cross section with a central angle of 90 °. And the light source 102
Is refracted by each curved prism surface 101b and transmitted through the optical element 100, whereby a light ray image (pointer image) extending in the radial direction of each micro optical element 101 is displayed.

In such a display device, there is an advantage that by using a light beam image as a pointer, analog quantity display can be performed with a simple configuration without requiring a mechanical configuration.

However, in the display device shown in FIG. 12, as shown in FIG. 13A, the edge of the light image S may be blurred and unclear, and the display quality of the light image S is low. Was. FIG. 13B shows a desirable light beam image S with no edge blur.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a display device capable of reducing the blur of the edge of a light image and improving the display quality of the light image.

[0009]

The technical means for achieving the above object is that a plurality of ridge-shaped micro-optical elements having an outer peripheral surface serving as a prism surface or a reflecting surface are provided on a predetermined surface in a circumferential direction. An optical element formed in parallel with each other and periodically in a radial direction, and a light source for irradiating predetermined light toward the plurality of micro optical elements, and the optical A display device configured to generate a ray image extending from a center of curvature of the plurality of micro optical elements of the element toward a radiation direction corresponding to the ray,
The arithmetic average roughness (Ra) of the surface of each of the micro optical elements of the optical element is set to 0.2 μm or less.

[0010]

FIG. 1 is a front view showing a state in which a display device according to an embodiment of the present invention is installed on an instrument panel of a vehicle. FIG. 2 is a front view of the display device of FIG. FIG. 3 is a sectional view of the display device of FIG.
FIG. 3 is a sectional view of the display device of FIG.

The instrument panel section 1 is provided in front of a driver's seat in the interior of a vehicle and displays various kinds of information such as a vehicle speed and an engine rotation speed. The display device 10 is installed. At the periphery of the display window 3, there is provided an index display (diameter) 4 including scales, numerals, and the like for visually recognizing the quantity value indicated by the light beam image (pointer image) S displayed on the display device 10. ing.

The display device 10 comprises an optical element 11 and a substrate 1
The light source 14 includes a plurality of light sources 14 disposed on the control unit 3, and a control unit (not shown) for individually controlling on / off of each light source 14.

The optical element 11 is a transparent member (resin molded body here) colored in a predetermined color, and a plurality of optical elements 11 are provided on the back side (the opposite side to the viewer side) of the disk-shaped element body 11a. The micro optical elements 12 are periodically arranged on a concentric circle (for example, 0.3 m
m pitch). 2 and 3
The arrangement pitch of each of the micro optical elements 12 shown in FIG. 1 is coarser than the actual arrangement pitch in the expression of the drawing.

Each light source 14 extends along the outer circumference of the optical element 11, that is, the outermost minute optical element 12.
They are regularly arranged at predetermined intervals in the circumferential direction on an imaginary circle which is on the outer peripheral side and concentric with each micro optical element 12 (see FIG. 2). Then, light from each light source 14 is incident on each micro optical element 12.

Each light source 14 is disposed on the back side of the optical element 11 and at a predetermined distance from the optical element 11. Here, the distance between each light source 14 and the optical element 11 is such that light from each light source 14 enters each micro optical element 12 and a light image S of a predetermined length can be displayed on the front side of the optical element 11. Distance, the shape of each micro-optical element 12,
It is determined by the refractive index and the like.

As each of the light sources 14, a cold cathode tube, a fluorescent display tube, an LED, a bulb, a liquid crystal display device (including a backlight), an EL display device, or the like can be used.

Each of the micro optical elements 12 is formed in a substantially fan-shaped cross section with a central angle of less than 90 °.
The first prism surface 12a located on the side opposite to the second prism surface 12b and the second prism surface 12b located on the opposite side are adjacent to each other at a predetermined angle via a predetermined ridgeline 12c.

In the present embodiment, since each light source 14 is arranged on the outer peripheral side of the outermost micro optical element 12, the outer peripheral side of each micro optical element 12 is placed on the first prism surface 1.
2a, and the inner peripheral side thereof is a second prism surface 12b.

The first prism surface 12a moves away from the light source 14 as it approaches the light source 14 in the direction X (see the axis X in FIG. 3) perpendicular to the surface direction of the optical element 11 (as it approaches the ridge line 12c). It is formed on an inclined prism surface 12a that is inclined in the direction. The second prism surface 12b is formed on a curved prism surface 12b that bulges outward and has a substantially arc-shaped cross section.

A control unit (not shown) selects a light source 14 corresponding to a predetermined quantity value indicated by the input signal from a plurality of light sources 14 based on an input signal indicating an engine rotation speed or the like input from the outside. It is made to let.

In such a display device, as shown in FIG. 3, light L radially emitted from any one of the light sources 14 emits light L of the light source 14 of the optical element 11.
When the light passes through a portion along the radial direction passing through the optical element 11, the light is refracted or reflected in various directions by the curved prism surface 12b of each micro optical element 12, and is emitted to the front side of the optical element 11. Therefore, the light L emitted from the radial portion of the optical element 11 passing through the light source 14 that is turned on is visually recognized by a viewer, and as a result, the center of curvature of each micro optical element 12 (here, the optical element 11 A light beam image S linearly extending in the radial direction corresponding to the light source 14 lit from the center of the image is generated at a predetermined image forming position P. In the present embodiment, the light image S
Is generated at the position where the light source 14 is disposed.
The radial length of the light image S generated in this way is the light source 1
4 is much larger than the radial size,
A large light image S is obtained by the small light source 14.

Accordingly, when one light source 14 corresponding to a predetermined quantity value is turned on, a light image S extending radially from the center of the optical element 11 in the angular direction corresponding to the light source 14 is provided.
Will be displayed.

Therefore, according to the present embodiment, the light source 14 corresponding to the predetermined numerical value to be displayed is selected from among the plurality of light sources 14 arranged in a circle, and is turned on.
By using the light image S of No. 4 as a pointer, analog quantity display can be performed with a simple configuration without requiring a mechanical configuration.

In the display device configured as described above,
The relationship between the surface roughness (here, the arithmetic average roughness (Ra)) of the surface of the optical element 11 (particularly, the prism surfaces 12a and 12b of each micro optical element 12) and the generated light image S was analyzed. As a result, it was confirmed that there was a close relationship between the arithmetic average roughness (Ra) and the blur of the edge of the light image S. That is, it was found that the smaller the arithmetic average roughness (Ra), the more the edge blur of the light image S is improved and the sharpness of the light image S is improved.

Here, the arithmetic average roughness (Ra) is defined as in FIG.
As shown in the figure, this is a value obtained by averaging the absolute value of the height difference between the average curve Za of the roughness curve Z indicating the cross-sectional shape of the predetermined uneven surface and the roughness curve Z in the cutting line direction and conforming to the JIS standard. It was done. In the present embodiment, the arithmetic average roughness (Ra) of the front surface and the back surface of the optical element 11 is 0.2.
It is set to be less than μm. In the optical element forming region on the rear surface of the optical element 11 where the micro optical element 12 is formed, the concave and convex micro optical element 12 is formed.
The arithmetic average roughness (Ra) is defined based on the pattern surface of (1).

Here, in order to evaluate the sharpness of the generated light image S, as shown in FIG. 5, the luminance Lmax at the center in the width direction of the light image S and the edge portion ( Here, a luminance La at a position separated from the center by 1.5 mm in the width direction) is detected, and both luminances Lm are detected.
The contrast between α and La (α = La / Lmax) was obtained, and the sharpness of the light image S was evaluated based on the contrast (α). That is, the narrower the width of the light beam image S and the better the sharpness, the more the luminance Lma of the central part
As x increases, the luminance La at the edge decreases,
The contrast (α) is reduced.

The measurement of the luminances Lmax and La of the light image S is as follows.
As shown in FIG. 6, light L from the light source 14 is
To generate a light beam image S, light L from a light source 14 that generates the light beam image S is made incident on a luminance meter 16 through a movable slit 15, and the movable slit 15 is moved as shown by an arrow 17. By moving the light image S in the width direction, the brightness detection position in the light image S was narrowed down by the movable slit 15 in a pinpoint manner. The light source 14 was prepared using a cold-cathode tube and a light diffusing plate so as to have uniform luminance in the light emitting surface, and the size of the light emitting surface was 1.0 × 1.0 mm. The size of the light-transmitting portion 15a of the slit 15 is 0.
The length was set to 1 mm at 1 mm. The distance between the light source 14 and the movable slit 15 was 8 mm.

FIG. 7 is a graph showing the relationship between the arithmetic average roughness (Ra) and the contrast (α) under the measurement conditions shown in FIGS. According to the graph of FIG. 7, the contrast (α) is almost proportional to the decrease in the arithmetic average roughness (Ra).
Is smaller.

FIG. 8 shows the arithmetic average roughness (Ra) and the ray image S.
Is a graph showing the relationship with the luminance distribution in the width direction of the graph, wherein a graph G1 shows the luminance distribution of the light image S when Ra = 3 μm, and a graph G2 shows the luminance distribution of the light image S when Ra = 0.2 μm. The luminance distribution is shown, and the graph G3 shows Ra = 0.1 μm
5 shows the luminance distribution of the light beam image S at the time of. The graph G4 shows a luminance distribution obtained by removing the optical element 11 and measuring the luminance distribution of the light emitting surface itself of the light source 14 under the measurement conditions shown in FIG.

From the graph of FIG. 8, if the arithmetic average roughness (Ra) in the optical element forming region of the optical element 11 is 0.2 μm or less, the luminance distribution (contrast) of the light source 14 alone shown in the graph G4. It can be seen that a light beam image S having substantially the same luminance distribution (contrast) is generated.

Next, the reason why the edge blur of the light source image S is improved by reducing the arithmetic average roughness (Ra) of the optical element 11 will be described with reference to FIGS.
9 to 11 schematically show the configuration when the optical element 11 is cut along the tangential direction of the micro optical element 12. FIG.

If the optical element 11 is provided with the micro optical element 12 having a smooth ideal surface form without any scratches on the rear surface of the optical element 11, as shown in FIG.
The light L emitted radially from is transmitted through the optical element 11 without being scattered, whereby an ideal light image S without blur as shown in FIG. 13B is generated.

On the other hand, the surface of the optical element 9 (particularly, the surface of the minute optical element 12) has irregularities such as scratches as shown in FIGS. Is scattered by a scratch or the like when transmitting through the optical element 11. Thus, the light L from the light source 14 is
When the light is scattered in the circumferential direction of the micro optical element 12 (that is, in the width direction of the light image S) due to irregularities such as scratches on one surface, FIG.
As shown in FIG. 11, unnecessary light L that does not originally contribute to the generation of the light beam image S is incident on the viewpoint of the viewer, and thereby the edge of the light beam image S is blurred.

The magnitude of the scattering of the light L from the optical element 11 is related to the size of irregularities such as scratches on the surface of the optical element 11, and the smaller the arithmetic average roughness (Ra) of the surface of the optical element 11 is, the smaller it is. The degree of scattering is reduced, and the range in which unnecessary light L that causes edge blurring of the light beam image S reaches the viewpoint is narrowed, whereby the blurring of the light beam image S is improved.

As described above, according to the display device of this embodiment, the surface of the optical element 11 (particularly, the minute optical element 1
Since the arithmetic average roughness (Ra) of the surface 2 is set to 0.2 μm or less, unnecessary light L that does not originally contribute to the generation of the light beam image S is scattered on the surface of the optical element 11 so that the viewer cannot observe the light L. Can be suppressed from entering the viewpoint, thereby blurring of the edge of the light beam image S is greatly reduced, a clear light beam image S can be displayed, and the display quality of the light beam image S can be improved. I can do it.

In this embodiment, the micro optical element 12
Is provided on the back surface of the optical element 11, but the micro optical element 12 may be provided on the front surface of the optical element 11.

In this embodiment, the light source 14 is provided on the back side of the optical element 11 and the light L from the light source 14 is transmitted through the optical element 11 to generate the light beam image S. Is disposed facing the outer peripheral side of the optical element 11 (or on the front side), and the light L from the light source 14 is transmitted from the outer peripheral side (or from the front side surface) of the optical element 1.
1 and the prism surface 12 of each micro optical element 12
b, the light is reflected forward (total reflection in this case), and the optical element 11
The light image S may be generated by emitting the light forward from the front surface of the light emitting device.

[0038]

According to the first aspect of the present invention, the arithmetic average roughness (Ra) of the surface of each micro optical element of the optical element is:
Since it is set to 0.2 μm or less, the light image S
Of unnecessary light L that does not contribute to the generation of light is prevented from entering the viewer's viewpoint due to scattering on the surface of the optical element 11, whereby blurring of the edge of the light beam image is greatly reduced, and A light beam image can be displayed, and the display quality of the light beam image can be improved.

[Brief description of the drawings]

FIG. 1 is a front view showing a state in which a display device according to an embodiment of the present invention is installed on an instrument panel of a vehicle.

FIG. 2 is a front view of the display device of FIG.

FIG. 3 is a cross-sectional view of the display device of FIG.

FIG. 4 is an explanatory diagram of arithmetic average roughness (Ra).

FIG. 5 is an explanatory diagram of a contrast (α) of a light image.

FIG. 6 is a diagram showing a facility configuration when measuring a luminance distribution of a light image.

FIG. 7 is a graph showing the relationship between arithmetic average roughness (Ra) and contrast (α).

FIG. 8 is a graph showing a relationship between arithmetic average roughness (Ra) and a luminance distribution in a width direction of a light beam image.

FIG. 9 is a diagram illustrating the relationship between the surface roughness of an optical element and the blurring of the edge of a light beam image.

FIG. 10 is an explanatory diagram of a relationship between a surface roughness of an optical element and blurring of an edge of a light beam image.

FIG. 11 is an explanatory diagram of a relationship between a surface roughness of an optical element and blurring of an edge of a light beam image.

FIG. 12 is a sectional view of a main part showing a display device proposed earlier.

13A is a front view showing a light image in the display device of FIG. 12, and FIG. 13B is a front view showing an ideal light image.

[Explanation of symbols]

 Reference Signs List 10 display device 11 optical element 11a element main body 12 micro optical element 12a inclined prism surface 12b curved prism surface 14 light source S ray image

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayoshi Imoto 1-7-10 Kikuzumi, Minami-ku, Nagoya-shi, Aichi F-term in Harness Research Institute, Inc. (Reference) 3D044 BA21 BB01 BC13 BD01 BD02 5C096 AA04 BA02 CA04 CA06 CA15 CA22 CB02 CC06 CC07 CC13 CC21 CC30 CD02 CD32 CD33 CD53 CG04 FA11 FA17

Claims (1)

[Claims] An optical element in which a plurality of ridge-shaped micro optical elements each having an outer peripheral surface serving as a prism surface or a reflecting surface are formed on a predetermined surface in parallel with each other in a circumferential direction and periodically in a radial direction. A light source that irradiates predetermined light toward the plurality of micro optical elements, and the light emitted from the light source causes the light from the center of curvature of the plurality of micro optical elements of the optical element to the light beam. A display device configured to generate a ray image extending in a corresponding radiation direction, wherein an arithmetic average roughness (Ra) of a surface of each of the micro optical elements of the optical element is set to 0.2 μm or less. A display device, comprising: