阅读说明：本技术 车载显示装置 (Vehicle-mounted display device ) 是由 大石利治 佐藤弘章 于 2018-04-18 设计创作，主要内容包括：能够设置于车辆的车厢内的车载显示装置具有液晶面板和光源。液晶面板显示被摄像机拍摄到的车辆外的图像。光源对液晶面板进行照明。光源的最大亮度的方向是穿过预先对车辆设定的视线范围内的方向。在示出用极角和方位角表示的各方向的光源的亮度的亮度分布图中,等亮度曲线为与第一方向相比在与第一方向交叉的第二方向上更长的形状。相对于液晶面板的长边方向而言,第二方向以及在亮度分布图上表示穿过液晶面板的中心的、视线范围的切线的极角及方位角的点的集合的长边方向向同一侧倾斜。(An in-vehicle display device that can be installed in a vehicle compartment of a vehicle includes a liquid crystal panel and a light source. The liquid crystal panel displays an image outside the vehicle captured by the camera. The light source illuminates the liquid crystal panel. The direction of the maximum brightness of the light source is a direction passing through a sight line range set in advance for the vehicle. In a luminance distribution diagram showing the luminance of the light source in each direction indicated by the polar angle and the azimuth angle, the equal luminance curve has a shape longer in a second direction intersecting the first direction than in the first direction. The second direction and the long side direction of the set of points representing the polar angle and the azimuth angle of the tangent to the line of sight passing through the center of the liquid crystal panel on the luminance distribution map are inclined to the same side with respect to the long side direction of the liquid crystal panel.)

1. An in-vehicle display device that can be installed in a compartment of a vehicle, the in-vehicle display device comprising:

A liquid crystal panel that displays an image outside the vehicle captured by a camera; and

A light source illuminating the liquid crystal panel,

wherein a direction of the maximum luminance of the light source is a direction passing through a sight line range set in advance for the vehicle,

In a luminance distribution diagram showing luminance of the light source in each direction expressed by a polar angle and an azimuth angle, an equal luminance curve is in a shape longer in a second direction crossing a first direction than the first direction,

The second direction and a long side direction of a set of points representing polar angles and azimuth angles of tangents to the line of sight range passing through the center of the liquid crystal panel on the luminance distribution map are inclined to the same side with respect to a long side direction of the liquid crystal panel.

2. The in-vehicle display device according to claim 1,

The direction of the maximum luminance of the light source is an obliquely upward direction with respect to the front direction of the liquid crystal panel.

3. The in-vehicle display device according to claim 1 or 2,

The direction of the maximum brightness of the light source is a direction passing through the center of the line of sight range.

4. The in-vehicle display device according to any one of claims 1 to 3,

The front direction of the liquid crystal panel is a direction passing through the outside of the visual line range.

5. The in-vehicle display device according to any one of claims 1 to 3,

The front direction of the liquid crystal panel is a direction passing through the inner side of the visual line range.

6. The in-vehicle display device according to any one of claims 1 to 5,

the light source includes:

a planar light emitting unit that emits light from a light emitting surface; and

and a prism sheet having an inverse prism shape, which is disposed on the light emitting surface of the planar light emitting unit, and which has a prism surface on the light emitting surface side.

Technical Field

the present disclosure relates to an in-vehicle display device for displaying an image of the rear side of a vehicle captured by a camera.

Background

the following electronic rearview mirror systems are known (see, for example, patent document 1): the vehicle has displays provided on the left and right sides of a driver's seat in a vehicle compartment, and the displays are configured to display an image of the rear side of the vehicle captured by a camera. A liquid crystal panel or the like is used as the display.

Disclosure of Invention

The present disclosure provides an in-vehicle display device that enables a driver to easily visually recognize an image.

An on-vehicle display device according to an aspect of the present disclosure is an on-vehicle display device that can be installed in a compartment of a vehicle, and includes: a liquid crystal panel that displays an image outside the vehicle captured by the camera; and a light source that illuminates the liquid crystal panel. The direction of the maximum brightness of the light source is a direction passing through a sight line range set in advance for the vehicle. In a luminance distribution diagram showing the luminance of the light source in each direction indicated by the polar angle and the azimuth angle, the equal luminance curve has a shape longer in a second direction intersecting the first direction than in the first direction. The second direction and the long side direction of the set of points representing the polar angle and the azimuth angle of the tangent to the line of sight passing through the center of the liquid crystal panel on the luminance distribution map are inclined to the same side with respect to the long side direction of the liquid crystal panel.

In addition, any combination of the above-described constituent elements, and a mode in which the expression of the present disclosure is converted between a method, an apparatus, a system, and the like are also effective as a mode of the present disclosure.

According to the present disclosure, the driver can easily visually recognize the image.

Drawings

Fig. 1 is a plan view schematically showing a vehicle mounted with an electronic rearview mirror system according to an embodiment.

fig. 2 is a side view schematically showing the vehicle of fig. 1.

Fig. 3 is a view showing a position where the first in-vehicle display device of fig. 1 is installed in the vehicle compartment.

Fig. 4 is a diagram showing an arrangement relationship of the respective components of the in-vehicle display device of fig. 1.

Fig. 5 is a diagram for explaining a polar angle and an azimuth angle in the in-vehicle display device of fig. 1.

fig. 6 is a luminance distribution diagram of the first on-board display device of fig. 1.

Fig. 7 is a luminance distribution diagram of a backlight of the vehicle-mounted display device of the comparative example.

Fig. 8 is a diagram showing an installation position of the first vehicle-mounted display device according to the modification in the vehicle compartment.

Detailed Description

Before describing the embodiments of the present disclosure, problems in the prior art are briefly described. In general, since the backlight of a liquid crystal panel has a direction of maximum brightness substantially in front of the liquid crystal panel, it is sometimes difficult for a driver to visually recognize an image of a display with sufficient brightness depending on the installation position of the display in an electronic rearview mirror system.

Before the embodiments are explained in detail, the outline will be described. The embodiment relates to an in-vehicle display device that can be provided on the left and right sides in the vehicle compartment of a vehicle and is used by a driver to confirm the rear side of the vehicle. The in-vehicle display device includes a liquid crystal panel and a backlight. The liquid crystal panel displays an image of the rear side of the vehicle captured by the camera. The backlight illuminates the liquid crystal panel. In the in-vehicle display device according to the embodiment, the direction of the maximum luminance of the backlight is a direction passing through a sight line range set in advance for the vehicle. In a luminance distribution diagram showing the luminance of the backlight in each direction, the equal luminance curve has a shape longer in a second direction intersecting the first direction than in the first direction. The second direction and the long side direction of the set of points representing the polar angle and the azimuth angle of the tangent to the line of sight passing through the center of the liquid crystal panel on the luminance distribution map are inclined to the same side with respect to the long side direction of the liquid crystal panel.

Fig. 1 is a plan view schematically showing a vehicle 1 on which an electronic rearview mirror system 10 according to an embodiment is mounted. Fig. 2 is a side view schematically showing the vehicle 1 in fig. 1. Fig. 3 is a view showing the installation position of the first onboard display device 30a of fig. 1 in the vehicle interior.

The electronic rearview mirror system 10 has a first camera 20a, a second camera 20b, a first in-vehicle display device 30a, and a second in-vehicle display device 30 b. The first camera 20a is provided around a left side door outside the vehicle compartment, captures an image of the left rear side outside the vehicle 1, and supplies image data to the first on-vehicle display device 30 a. The second camera 20b is provided around the right door outside the vehicle compartment, captures an image of the right rear side outside the vehicle 1, and supplies the image data to the second vehicle-mounted display device 30 b. When the first camera 20a and the second camera 20b are collectively referred to, they are appropriately referred to as the cameras 20. The camera 20 is configured using a CCD (Charge-Coupled Device) image sensor, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or the like. The camera 20 may be provided in the vehicle compartment.

The first on-vehicle display device 30a is provided on the left side in the vehicle compartment, and displays an image of the left rear side of the vehicle 1 captured by the first camera 20 a. Specifically, as shown in fig. 3, the first vehicle-mounted display device 30a is provided on the front side of the vehicle 1 housed in the left side door. The second onboard display device 30b is provided on the right side in the vehicle compartment, and displays the right rear side image of the vehicle 1 captured by the second camera 20 b. Specifically, the second onboard display device 30b is provided on the front side (not shown) of the vehicle 1 housed in the right side door. When the first on-vehicle display device 30a and the second on-vehicle display device 30b are collectively referred to, they are appropriately referred to as the on-vehicle display device 30.

The eye lip E1 is shown in fig. 1 and 2, respectively. The eye lip E1 shows the range of the right and left eyes of the driver in the form of an ellipse in the side view and the top view. The sight line range is used to statistically represent the distribution of the positions of the eyes of the driver. The sight line range and the eye lip E1 are set in advance for the vehicle 1. If the vehicle models are different, the sight line range and the eye lip E1 are also different. The sight range and the eye lip E1 are also set in consideration of the movement of the seat position. As is apparent from fig. 1, the front direction d1 of the in-vehicle display device 30 is a direction passing through the outside of the eye lip E1, i.e., a direction passing through the outside of the visual range. Specifically, the front direction d1 is a direction passing through the front side of the vehicle 1 with respect to the eye lip E1 and the visual range.

Fig. 4 is a diagram showing an arrangement relationship of the respective components of the in-vehicle display device 30 of fig. 1. The in-vehicle display device 30 includes a liquid crystal panel 32 and a backlight 34. The liquid crystal panel 32 is disposed on the front side of the in-vehicle display device 30, and displays an image of the rear side of the vehicle 1 captured by the camera 20. The image display of the liquid crystal panel 32 is controlled by a control unit, not shown.

The backlight 34 is disposed on the back side of the in-vehicle display device 30 and illuminates the liquid crystal panel 32. The backlight 34 functions as a light source. The backlight 34 includes a planar light emitting section 50, a first prism sheet 52, a second prism sheet 54, and a diffusion sheet 56. The planar light emitting unit 50 emits light from the light emitting surface. The planar light emitting unit 50 includes a light emitting source 58, a light guide plate 60, and a reflection plate 62. The light emitting source 58 emits light while the in-vehicle display device 30 is in the on state. The light guide plate 60 is a plate-like member made of, for example, polycarbonate, and diffuses light from the light emission source 58 incident from an end face to emit the light almost uniformly to the front side. The reflection plate 62 reflects the light leaking from the light guide plate 60 to the back side toward the front side.

the first prism sheet 52 is an optical member having a reverse prism shape and having a first prism surface 64 on the back surface side, which is the light incidence side, disposed on the light emitting surface of the planar light emitting unit 50. The first prism sheet 52 changes the traveling direction of the light incident from the light guide plate 60 and emits the light to the front surface side, thereby adjusting the luminance distribution of the emitted light.

The second prism sheet 54 is an optical member having a reverse prism shape having a second prism surface 66 on the rear surface side, which is the light incident side, disposed on the front surface side of the first prism sheet 52. The second prism sheet 54 changes the traveling direction of the light incident from the first prism sheet 52 and emits the light to the front surface side, thereby adjusting the luminance distribution of the emitted light.

The light component in a predetermined direction can be increased by the shapes of the first prism surface 64 and the second prism surface 66. In the present embodiment, the first prism face 64 and the second prism face 66 are different in shape from each other, and the first prism face 64 and the second prism face 66 are each asymmetric in a predetermined direction, whereby the direction of maximum brightness and the brightness distribution are controlled as described later. The shapes of the first prism surface 64 and the second prism surface 66 are not particularly limited as long as the direction of the maximum luminance and the luminance distribution can be controlled as described later. In addition, if desired optical characteristics can be obtained by the first prism sheet 52, the second prism sheet 54 may not be provided.

The diffusion sheet 56 diffuses the light emitted from the second prism sheet 54. The light diffused by the diffusion sheet 56 illuminates the liquid crystal panel 32.

Next, the luminance distribution of the in-vehicle display device 30 will be described. The luminance distribution is expressed in terms of polar and azimuthal angles. Fig. 5 is a diagram for explaining a polar angle and an azimuth angle in the in-vehicle display device 30 of fig. 1. As shown in fig. 5, the angle formed by the front direction d1 and the direction d2 of the liquid crystal panel 32 is defined as a polar angle θ. The front direction d1 is a direction of a normal line at the center P1 of the liquid crystal panel 32. The polar angle θ of the front direction d1 is 0 °. It is assumed that the azimuth angle, which is the angle formed by the right direction in the display surface of the liquid crystal panel 32 and the line segment G1 when the direction d2 is projected onto the liquid crystal panel 32, increases counterclockwise when viewed from the front direction d1 of the liquid crystal panel 32. Therefore, in the display surface of the liquid crystal panel 32, the azimuth angle in the right direction is 0 °, the azimuth angle in the upper direction is 90 °, the azimuth angle in the left direction is 180 °, and the azimuth angle in the lower direction is 270 °.

Fig. 6 is a luminance distribution diagram of the first on-vehicle display device 30a of fig. 1. The luminance distribution chart shows an example of the luminance of the first on-vehicle display device 30a in each direction indicated by the polar angle θ and the azimuth angle. The luminance of the in-vehicle display device 30 is substantially equivalent to the luminance of the backlight 34. In fig. 6, the polar angle θ ranges from 0 ° to 80 °, and the azimuth angle ranges from 0 ° to 360 °. The luminance distribution map includes a plurality of equal luminance curves L1 to L3. The equal luminance curve L1 has the highest luminance, and the luminance decreases in the order of the equal luminance curve L2 and the equal luminance curve L3.

As shown in fig. 6, the direction of the maximum luminance of the backlight 34 indicated by a point P10 on the luminance distribution diagram is an obliquely upward direction with respect to the front direction d1 of the liquid crystal panel 32, and is a direction passing through a line of sight range determined in advance for the vehicle 1. In the example of fig. 6, the direction of the maximum luminance of the backlight 34 is a direction passing substantially through the center of the visual range. The direction passing through the center of the line of sight is represented on the luminance distribution map as point P2. The center of the line of sight coincides with the center C1 of the lip E1 shown in fig. 1 and 2.

The graph 100 is a set of points representing the polar angle θ and the azimuth angle of the tangent to the line of sight range passing through the center P1 of the liquid crystal panel 32 on the luminance distribution diagram. In the example of fig. 6, the graph 100 is generally elliptical. That is, the pattern 100 has a shape extending in the longitudinal direction. The pattern 100 can also be said to be a polar angle θ and azimuth angle pattern 100 at each position indicating the outline of the viewing range viewed from the center P1 of the liquid crystal panel 32 in the luminance distribution diagram, which is indicated by the viewing range of the right eye. The graphic 100 may also be determined using the line of sight range of the left eye and may also be determined using the line of sight ranges of the right and left eyes. For example, the graphic 100 may be determined using the outline of the region obtained by adding the line of sight range of the right eye and the line of sight range of the left eye.

the point P3 on the graph 100 corresponds to the tangent Hmin of the eye lip E1 having the smallest angle with respect to the front direction d1 shown in fig. 1 and the tangent Vmin of the eye lip E1 having the smallest angle with respect to the rear direction shown in fig. 2. The point P4 on the graph 100 corresponds to the tangent Hmax of the eye lip E1 having the largest angle with respect to the front direction d1 shown in fig. 1 and the tangent Vmax of the eye lip E1 having the largest angle with respect to the rear direction shown in fig. 2.

In the luminance distribution diagram, the equal luminance curves L1 to L3 have a longer shape in a second direction d12 orthogonal to the first direction d11 than in the first direction d 11. That is, the equal luminance curves L1 to L3 are shapes extending in the second direction d 12. The second direction d12 and the longitudinal direction of the pattern 100 are inclined to the same side with respect to the longitudinal direction of the liquid crystal panel 32, that is, the right direction having an azimuth angle of 0 ° or the left direction having an azimuth angle of 180 °. Specifically, the second direction d12 and the long side direction of the figure 100 are inclined to the direction having an azimuth angle of less than 180 ° with respect to the left direction. Here, the first direction d11 and the second direction d12 are directions within the luminance distribution diagram of fig. 6, and are directions within a plane representing the luminance distribution diagram. In the luminance distribution diagram of fig. 6, the second direction d12 may be, for example, a direction indicating a straight line passing through any 2 points of the points P2, P3, P4, and P10. The second direction d12 may not strictly indicate the directions of these straight lines, and may indicate a straight line that is approximate to a straight line passing through any 2 points of the points P2, P3, P4, and P10.

Although not shown, in the second on-vehicle display device 30b on the right side, the second direction d12 of the equal luminance curve and the longitudinal direction of the graphic 100 are inclined to the same side with respect to the longitudinal direction of the liquid crystal panel 32. Specifically, the second direction d12 and the longitudinal direction of the figure 100 are inclined with respect to the right direction in a direction having an azimuth angle larger than 0 °.

The luminance of the backlight 34 in the direction of each position of the outer shape of the visual range viewed from the center P1 of the liquid crystal panel 32, that is, the luminance of the backlight 34 in the direction indicated by each point on the graph 100 of the luminance distribution pattern is, for example, 50% or more of the maximum luminance of the backlight 34. Thus, the brightness at each position in the visual range is 50% or more of the maximum brightness of the backlight 34.

Next, the overall operation of the electronic rearview mirror system 10 configured as described above will be described. When the electronic rearview mirror system 10 is turned on, the camera 20 captures an image of the rear side of the vehicle 1, and the in-vehicle display device 30 displays the captured image of the rear side of the vehicle 1 using light from the backlight 34. The driver whose eyes are within the visual range can visually recognize the image at a luminance that is 50% or more of the maximum luminance of the backlight 34.

Here, an in-vehicle display device of a comparative example is explained. Fig. 7 is a luminance distribution diagram of a backlight of the vehicle-mounted display device of the comparative example. The luminance distribution map includes equal luminance curves L12 and L13. The luminance of the equal luminance curve L12 is higher than the luminance of the equal luminance curve L13. The direction of the maximum luminance of the backlight of the comparative example is the substantially front direction. Therefore, when the in-vehicle display device of the comparative example is installed at the installation position of the present embodiment of fig. 1, the deviation between the center of the visual range and the direction of the maximum luminance of the backlight is large as compared with the present embodiment of fig. 5. In addition, the luminance distribution diagram has a lower luminance in most directions in the graph 100 than in the present embodiment. This makes it difficult for the driver to visually recognize the image displayed on the liquid crystal panel with sufficient brightness.

In particular, in the installation position of fig. 1, direct sunlight easily strikes the liquid crystal panel of the in-vehicle display device, and it is more difficult for the driver to visually recognize an image when the direct sunlight strikes the liquid crystal panel. In addition, since the temperature of the in-vehicle display device is likely to increase when direct sunlight is irradiated, it is difficult to increase the overall brightness by increasing the power consumption of the backlight from the viewpoint of suppressing the temperature increase.

In contrast, according to the present embodiment, the direction of the maximum luminance of the backlight 34 is a direction passing through the visual range. In the luminance distribution diagram showing the luminance of the backlight 34 in each direction, the equal luminance curves L1 to L3 are long in the second direction d12, and the second direction d12 and the longitudinal direction of the pattern 100 are inclined to the same side with respect to the longitudinal direction of the liquid crystal panel 32. Thus, more light can be concentrated in the visual range than in the comparative example, with the same power consumption as in the comparative example. Therefore, the brightness in the direction of the eyes of the driver can be made higher than that of the comparative example without increasing the power consumption and without depending on the driver and the seat position. Therefore, the driver can easily visually recognize the image.

In addition, even when direct sunlight strikes the liquid crystal panel 32 of the in-vehicle display device 30, the brightness in the direction of the eyes of the driver is higher than that of the comparative example, and therefore the driver can easily see the image.

Further, since the direction of the maximum luminance of the backlight 34 is an obliquely upward direction with respect to the front direction d1 of the liquid crystal panel 32, the in-vehicle display device 30 can be provided at the right and left sides of the driver and at a position where the driver looks down. This makes it possible to make the driver visually recognize the image of the rear side of the vehicle in the direction of the line of sight close to the case of the door mirror using the mirror.

Further, since the direction of the maximum luminance of the backlight 34 is a direction passing through substantially the center of the visual range, more light can be concentrated in the visual range.

Further, since the front direction d1 of the liquid crystal panel 32 is a direction passing outside the visual range, the in-vehicle display device 30 can be provided at a position and in an orientation where the front direction d1 of the liquid crystal panel 32 does not face the eyes of the driver.

The present disclosure has been described above based on the embodiments. The present embodiment is illustrative, and it will be understood by those skilled in the art that various modifications are possible in combination of these respective components or the respective processing steps, and such modifications are also within the scope of the present disclosure.

For example, the installation position of the in-vehicle display device 30 is not limited to the example shown in fig. 1 and the like. Fig. 8 is a diagram showing the interior of the vehicle at the installation position of the first vehicle-mounted display device 30a according to the modification. As shown in fig. 8, the first in-vehicle display device 30a may be provided on the left side of the instrument panel in the vehicle compartment. Although not shown, the second in-vehicle display device 30b may be provided on the right side of the instrument panel in the vehicle compartment. In this case, the direction of the maximum luminance of the backlight and the luminance distribution are also set in the same manner as in the above embodiment. According to this modification, it is also possible to support a vehicle in which the in-vehicle display device 30 cannot be installed inside the door. In the present modification, the front direction d1 of the liquid crystal panel 32 of the first vehicle-mounted display device 30a may be a direction passing through the inside of the visual range. In this case, the first on-vehicle display device 30a may be provided such that the front direction d1 of the liquid crystal panel 32 is directed to pass through the inside of the visual range but to deviate from the center of the visual range.

One way of the present disclosure is as follows.

[ item 1]

An in-vehicle display device that can be installed in a vehicle compartment of a vehicle includes a liquid crystal panel and a light source. The liquid crystal panel displays an image outside the vehicle captured by the camera. The light source illuminates the liquid crystal panel. The direction of the maximum brightness of the light source is a direction passing through a sight line range set in advance for the vehicle. In a luminance distribution diagram showing the luminance of the light source in each direction indicated by the polar angle and the azimuth angle, the equal luminance curve has a shape longer in a second direction intersecting the first direction than in the first direction. The second direction and the long side direction of the set of points representing the polar angle and the azimuth angle of the tangent to the line of sight passing through the center of the liquid crystal panel on the luminance distribution map are inclined to the same side with respect to the long side direction of the liquid crystal panel.

According to this aspect, more light can be concentrated in the visual line range than in the comparative example, with the same power consumption as in the comparative example. Therefore, the brightness in the direction of the eyes of the driver can be made higher than that of the comparative example without increasing the power consumption and without depending on the driver and the seat position. Therefore, the driver can easily visually recognize the image.

[ item 2]

In the in-vehicle display device according to item 1, the direction of the maximum luminance of the light source may be an obliquely upward direction with respect to the front direction of the liquid crystal panel.

In this case, the in-vehicle display device can be provided at the right and left sides of the driver and at a position where the driver looks down. This makes it possible to make the driver visually recognize the image of the rear side of the vehicle in the direction of the line of sight close to the case of the door mirror using the mirror.

[ item 3]

In the in-vehicle display device recited in item 1 or 2, the direction of the maximum luminance of the light source may also be a direction passing through the center of the line of sight range.

In this case, more light can be concentrated into the sight line.

[ item 4]

In the in-vehicle display device according to any one of items 1 to 3, a front direction of the liquid crystal panel may be a direction passing through a range outside the visual line range.

In this case, the in-vehicle display device can be provided at a position and orientation where the front direction of the liquid crystal panel does not face the eyes of the driver.

[ item 5]

In the in-vehicle display device according to any one of items 1 to 3, a front direction of the liquid crystal panel may be a direction passing through an inner side of the visual range.

In this case, it is also possible to support the installation of the in-vehicle display device in which the front direction of the liquid crystal panel is a direction that passes through the inside of the visual range but deviates from the center of the visual range.

[ item 6]

The in-vehicle display device according to any one of items 1 to 5, wherein the light source may include a planar light emitting section and a prism sheet. The planar light emitting unit emits light from the light emitting surface. The prism sheet is arranged on the light emitting surface of the planar light emitting unit and has a reverse prism shape having a prism surface on the light emitting surface side.

In this case, the light source can be realized with a simple structure.

Industrial applicability

The present disclosure relates to an in-vehicle display device, and is particularly useful as an in-vehicle display device that displays an image of the rear side of a vehicle captured by a camera.

Description of the reference numerals

1: a vehicle; 10: an electronic rearview mirror system; 20: a camera; 20 a: a first camera; 20 b: a second camera; 30: an in-vehicle display device; 30 a: a first on-board display device; 30 b: a second onboard display device; 32: a liquid crystal panel; 34: a backlight; 50: a planar light emitting section; 52: a first prism sheet; 54: a second prism sheet; 56: a diffusion sheet; 58: a light emitting source; 60: a light guide plate; 62: a reflective plate; 64: a first prism face; 66: a second prism face; 100: a graph; c1: a center; e1: the lips of the eyes; g1: a line segment; hmax: cutting a line; hmin: cutting a line; vmax: cutting a line; vmin: cutting a line; l1, L2, L3: an equal brightness curve; l12, L13: an equal brightness curve; p1: a center; p2: point; p3: point; p4: point; p10: point; d 1: a front direction; d 2: direction; d 11: a first direction; d 12: a second direction.