KR950010029B1 - Dual-mirror virtual image display for vehicle - Google Patents

Abstract

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Description

Dual-mirror virtual image display for vehicle instrumentation

1 is a front sectional view schematically showing the virtual image display described.

2 is a front view of a single lens display system to help understand the virtual image display of FIG.

FIG. 3 is an unfolded form of the virtual display of FIG. 1 and is a front view of the lens display to help understand the virtual display of FIG.

4A and 4B are side and front views of an embodiment of a sub-magnification mirror of the virtual image display of FIG.

5A and 5B are side and front views of an embodiment of a magnification mirror of the virtual image display of FIG.

6 is a schematic diagram illustrating an off-axis lens system to assist in understanding the off-axis configuration of the virtual image display of the present invention.

7 is a schematic diagram of an on-axis lens system using an off-axis portion of the lens to assist in understanding a known off-axis system using off-axis couples of optical elements.

* Explanation of symbols for main parts of the drawings

11: image source 13: plane fold mirror

15: minor magnification mirror 71: magnification mirror

BACKGROUND OF THE INVENTION The present invention relates generally to virtual image displays, and more particularly to virtual image displays for vehicle instrumentation having instrument image sources of different sizes for large fields of view.

Conventional instrumentation devices for the same vehicle of a vehicle typically include a direct view gauge supported in a dashboard in front of a steering wheel. Although simple and effective, this conventional direct viewing instrumentation device should allow the driver's eyes to refocus between the roadway and the observation of the instruments. Moreover, conventional direct viewing instrumentation is typically difficult to read by a driver wearing myopia glasses because it is typically close enough (about 61-76 cm; about 24-30 inches) to the driver.

US patent application Ser. No. 07 / 096,870, filed on September 4, 1987 and assigned to the applicant, is more optically optical from the driver than a conventional direct observation instrument. An instrument apparatus virtual image display for effectively positioning a virtual image of an instrument apparatus in a distant effective position. The virtual image of the position far from the driver is achieved by a single positive magnification, i.e., an enlarged mirror. However, image sources that can use a single magnification mirror must be very small in order to maintain a fairly short system length (ie the distance from the image source to the mirror), which does not allow more than one instrument gauge or reading device. . And relatively large image sources, such as electromechanidal gauges, cannot be used.

Therefore, it is an advantage of the present invention to provide a vehicle instrument virtual image display provided for displaying two or more gauges or reading device.

Another advantage is to provide a vehicle instrument virtual display that allows the use of relatively large image sources such as analog electromechanical gauges.

The above and other advantages include the image source for providing imaging illumination, the sub-magnification aspheric side mirror that reacts to the image source imaging illumination to provide divergent reflected imaging illumination. power aspheric off-axis mirror, and converging reflection imaging that generates a virtual image of an image source observable by the vehicle driver at a longer viewing distance than the moving optical path by the illumination source and imaging source and the driver's eye. Provided by a vehicular virtual image display of the present invention comprising a positive power aspheric off-axis mirror responsive to divergent imaging illumination to provide illumination.

Advantages and features of the described invention can be readily appreciated by those skilled in the art from the following detailed description with reference to the drawings.

Like reference numerals designate like elements in the following description and in the drawings.

Referring now to FIG. 1, this figure illustrates a virtual image display system for a vehicle according to the present invention. The virtual image display may for example be arranged above the steering wheel of the vehicle and in front of the steering wheel, for example in the area usually occupied by the instrument panel, for example.

The display system includes an image source 11 and a planar fold mirror 13 that responds to imaging illumination from the image source 11. Planar fold mirror 13 reflects the imaging illumination with an off-axis convex negative power mirror 15 that provides divergent reflective illumination. The mirror 15 is characterized by a negative magnification because this causes an image reduction when observed directly, and also provides divergent reflection because parallel incidence lines incident on the mirror 15 are emitted by the reflection. Characterized in that.

Illumination from sub-magnification mirror 15 is incident on an off-axis concave positive power mirror 17 where the reflected illumination provides convergent reflective illumination. The mirror 17 is characterized by having a positive magnification because it provides an image magnification, and is characterized in that parallel incidence lines incident on the mirror 17 provide convergent reflection.

The illumination reflected by the magnification mirror 17 passes through curved protective windows 19 to the viewer. The curved protective window 19 is a concave part of the elliptical cylinder, which is configured such that, especially when viewed outside the display system, the reflections from where the observer can see are limited to the reflections of the dark ray traps disposed above the protective window. Negative and constant magnification mirrors 15 and 17 have an aspherical, non-rotating symmetrically symmetrical reflective surface, for example an injection mold or a casting mold having an essential aspherical surface covered with a metal reflective coating. It may include a cast mold plastic substrate.

Aspherical elements 15 and 17 have optical axes OA1 and OA2 defined by the base radius of their respective reflective surfaces before they are deformed into aspherical surfaces. The optical axes pass through optical axis points P1 and P2 used as the origin of the respective coordinate systems used to define the aspherical deformation of each surface. In other words, the optical axis points P1 and P2 and the axes passing therethrough are fixed and the peripheral ranges are deformed into aspherical surfaces.

On the reflective surface of the sub-magnification mirror 15, the optical axis OA1 combines the image source center and the image center, and the incidence portion of the central axis CA defined by the line passing through the optical axis points P1 and P2. Divide the reflective part. On the reflective surface of the constant magnification mirror 17, the optical axis OA2 further divides the incident and reflective portions of the central axis.

In proportion to the optical axes OA1 and OA2, the aspherical elements are off-axis because the central axis CA is not collinear with the optical axes, and the optical axes of the aspherical elements whose image source and image comprise certain reflective fold mirrors here. Do not put on

In addition, the central axis CA defines the optical path traveled by the imaging illumination from the image source to the eyes of the vehicle driver, and as also described herein, this optical path is the effective viewing distance of the virtual image (i.e. Distance longer than the eye focuses to observe the virtual image.

Existing systems have used mirrors in which the mirrors comprise off-axis portions of the sphere or aspherical portion of the cone (eg parabolic), which system uses an image source on the optical axis of the cone portion used to define the mirrors. Be aware that you deploy This is done to maintain some rotational symmetry to facilitate manufacturing. However, this limits the performance of this optical system by limiting the degree of aspherical surface that can be applied to the mirror surface. The optical system described in the present invention eliminates this limitation by placing the image source off-axis, thus decoupling the optical axis of the aspheric surface from the image source. Aspheric mirrors of the present invention are not rotationally symmetrical and take some form to improve the overall starting performance. This added design freedom surpasses the performance of the prior art designs of the present invention.

The sub-magnification mirror 15 is a smaller mirror and is enlarged without requiring a change in the size or the virtual image range of the image source 11 (ie, the effective distance for focusing the viewer's eye to see the virtual image). In order to achieve a significant range of magnification for the virtual image, it is arranged in relation to the large magnification mirror 17 which is different in a relatively simple optical manner (eg, in a Cassgrain telescope). According to the present invention, the virtual image range is in the range of about 122 cm to 366 cm (4 to 12 ft) which is much larger than the typical distance between the driver's eyes and the direct viewing instrument device in the instrument panel.

The use of sub- and mirror magnification mirrors provides adequate magnification, virtual image range, field of view, and optical performance (i.e. reduction of distortion and imbalance) and is smaller than a single magnification mirror system with comparable parameters. Maintain the optical system length (ie, the distance between the image source and the optically closest mirror to the nominal eye position). In other words, for a given magnification, virtual image range, field of view, and optical performance, the dual mirror system described above has a shorter system length than a comparable single constant magnification mirror system, and thus has a smaller optical package.

Miniaturization of a dual mirror system is the result of a reverse telephoto arrangement of sub- and magnification mirrors providing increased active focal length without significant increase in system length. As is known, the active focal length is from the image source to the “first principle plane” placed in a position where a single lens or mirror is arranged to form a single lens or mirror optical system with virtually identical parameters. Is the distance. The first principle plane for the dual mirror system is disposed between the nominal eye position and the optically nearest mirror here, and the first principle plane for the single constant magnification mirror system is disposed on the mirror. In other words, the first principle plane for the double mirror system is not limited to the physical location of one of the optical elements.

The elements that allow a dual mirror system to achieve a smaller system length are further compared to the single and dual lens systems shown in FIGS. 2 and 3, respectively, in which the single lens system and the dual mirror system are basically unfolded. I can understand it better and understand it more easily. Relevant optical parameters are as follows.

Range (R): distance from the nominal eye position to the virtual image.

Eye Relif (eL): distance from the nominal eye position to the first lens surface.

Eye Box (Y): The diameter of the space around the nominal eye position at which the virtual image can be observed without any vignetting.

Field of View (FOV): The actual angle of the virtual image when viewed from the nominal eye position.

System Length (Z): The distance between the lens and the image source nearest to the eye.

Back Focus (B): The lens closest to the image source from the image source.

Activity Focus Length (F): The distance from the image source to the first principle plane of the optical system.

Activity diameter (D): Diameter of the first principle plane.

Activity F-TN (F / #): The ratio of activity focus length to activity diameter (ie F / D).

Image Source Size (H): The height of the image source (in the vertical plane).

Virtual image size (H '): The height of the virtual image (within the vertical plane).

The optical performance (ie reduction of distortion and nonuniformity) of each single and dual lens system is directly related to activity F / #. In particular, performance is reduced when activity F / # is reduced. Therefore, for a given performance specification, activity F / # is typically fixed. It is also desirable to make the system length Z as short as practical in order to minimize the optical package.

For a single lens, as shown in FIG. 2, the active focal length F, the rear focal point B, and the system length Z are the same. The active diameter (D) is simply the diameter of the lens. For a given range (R), eye relief (L-), eye box size (Y), and field of view (FOV), the activity diameter (D) can be expressed as follows.

D = 2Ltan (FOV / 2) + V (1-L / R) (Equation 1)

or

D = 2Ltan (FOV / 2) + Y₁, where R-> About (Equation 2)

The required image source size H is equal to the ratio of the virtual image size H 'and the image source size H to the ratio of the image distance (lens to image) to the image source distance (lens to image source).

H [2Rtan (FOV / 2) F] (R-L) (Equation 3)

or

H = 2Ftan (FOV / 2), R-> About (Equation 4)

Therefore, for specific FOV, range, eye box, and eye relief requirements, the action diameter is defined by equation (1). Since the activity F / # is minimum and fixed for a particular performance requirement, the activity focus length is also fixed (since F = DF / #), so that the image source size is determined by equation (1).

The single lens system provides adequate performance when the image source can be of any size to match the image source size requirements described above. This size can be achieved when the image source includes liquid crystal display (LCD) or vacuum fluorescent display (VFD) technology, which can be easily changed to make the graphic size considerably smaller. However, electromechanical gauges cannot be miniaturized to a certain size, for example less than about 2.54 cm (1 inch) in diameter. If a size constraint is given to an analog image source, the above equations may be melted at the reverse initiation with a given image source size.

If the analog gauge is larger than the limited image source size indicated by the equations, the activity focus length and FOV increase for a constant activity F / #. If the FOV is to be kept constant, the activity diameter is also constant, and only the method for using a larger image source will increase the F / #. This will also increase the working focal length (even if it is larger than if the FOV can be increased). If the analog gauge image source cannot be made as small as an LCD or VFD source, the overall result is that the system length should be increased for a single lens system when an analog gauge is used as the image source. Longer systems mean an overall increase in longer boxes and optical packages.

Consider now the dual lens system of FIG. 3, which is an unfolded form of the dual mirror system described above and serves as an inverted photographic transmission arrangement that provides increased active focal length without increasing the system length. For simplicity, the range is set to infinity beyond that for the single lens system. The focal lengths of the two lenses are f ₁ and f ₂, where f ₁ is the magnification focal length and f ₂ is the negative magnification focus lens. The distance between the two lenses is x. Therefore, the activity focus length of this system is as follows.

F = (f₁) (f₂) / (f₂ + f₂-x) (Equation 5)

to be.

As can be seen in Figure 3, this focal length actually exceeds this system length. By varying f₁ and f2, the focal length is almost independent of the back focus and the system length. The length L1 from the nominal eye position to the first principal plane is as follows.

L1 = l + x-B-F (Equation 6)

In addition, activity diameter is as follows.

D = 2l1 tan (FOV / 2) + Y (Equation 7)

Solving for the image source size (H) by range (R) at infinity, Equation 7 is reduced to

H = 2Ftan (FOV / 2) (Equation 8)

This is the same as Equation 4.

If the image source size is changed, and the activity F / # and field of view (FOV) are constant, the activity focus length is set by equation (8); The activity diameter D is set by activity F / #, and L1 is set by equation 7. Equation 6 can then be solved for the amount X + B, which is the system length.

As in the example of the difference between single and dual-lens systems, optical parameters for single and dual-lens systems can be calculated for the system specifications below.

R

L = 24 inches (24 × 2.54 cm)

Y = 2.5 inches (2.5 × 2.54 cm)

FOV = 3 °

For delivered performance, the activity F / # cannot be less than 2.0.

Using Equation 2 for a single lens system, the active diameter (from F / # = F / D) should be 9.543 cm (3.757 inches), which requires a focal length of 19.086 cm (7.514 inches). This is also the system length because for a single lens system the length is equal to the active focal length. From Equation 4 the image source size should be 1 cm (0.394 inches).

Now consider the use of an analog gauge package that is 2.54 cm (1 inch) in size for the image source. Keeping the FOV from Equation 4 and at 3 °, the focal length should increase to 48.499 cm (19.094 inches). This is a 150% increase in system length. The active diameter is maintained at 9.542 cm (3.757 inches) with a F / # of 5.082.

If a system length of 48.499 cm (19.094 inches) is unacceptable, the FOV can be varied to reduce the focal length. By substituting (D) (F / #) for the focal length F of equation 2 and substituting the expression for D from equation 2, the image source can be related to the activities F / # and FOV.

H = {2F / # tan (FOV / 2)} [2Ltan (FOV / 2 + Y] (Equation 9)

Solving the quadratic equation for FOV (keeping a fixed activity F / # at 2.0 in this example) gives the value 5.803. Substituting this value into Equation 4 is an active diameter of 12.529 cm (4.933 inches) with an active focal length of 25.057 cm (9.865 inches). Although the system length is reduced to 25.057 cm (9.865 inches) (still larger than the original 19.085 cm (7.514 inches) for smaller image source sizes of 1 cm (0.394 inches)), the active diameter is 9.543 cm (3.757 inches). To 12.529 cm (4.933 inches) (31% increase). Therefore, even with the new FOV, the overall size of the system is increased.

The dual lens approach will now be analyzed for an image source size of 2.54 cm (1 inch). From Equation 8, the active focal length is 48.499 cm (19.094 inches) for 3 ° FOV. Set the distance (x) between two lenses to be 7.62 cm (3 inches), and the system length (specified eye relief (L), eye box (Y), and field of view (19.085 cm (7.514 inch)) Setting the shortest possible single lens design for FOV), the rear focus will be 11.466 cm (4.514 inches). At this time, from Equation 6, L1 is equal to 31.546 cm (12.42 inches). The focal lengths of each lens vary in proportion to another equation, but one solution from equation 5 is that f1 is 19.222 cm (7.568 inches) and 2SMS -19.222 cm (7.568 inches). Since the size of f1 is equal to the active diameter of a single lens of 9.543 cm (3.757 inches), the F / # of f1 is 2.014.

From the comparisons above, it can be appreciated that for an image source size specified according to optical specifications such as range, FOV, etc., the dual lens system provides a system length comparable to a single lens system having a smaller image source size. . Since the activity F / # of the individual lenses in the dual lens system is not too fast, this optical performance indicates that there are two lenses to best fit here, which is superior to the single lens approach.

After using the optical design computer program having the spherical mirror form of the primary design, as in the installation of the dual mirror display system described above, the above-described analysis of the dual lens system can be used to be achieved in the primary design. In a computer program, nominal spherical surfaces are modified to meet the required criteria to minimize distortion when observed in an eye box. Since the eye box and the virtual image are off-axis with respect to each axis of the two mirrors, the equation of the aspherical surfaces can be adjusted independently of the axis combining the eye and virtual image. This provides greater tolerance in the design process and can more easily correct optical aberrations and distortions. Such distortions can cause vertical non-uniformity and magnification distortion that are inappropriate for the final design.

Referring now to FIGS. 4A, 4B, 5A, and 5B, which are embodiments of the aspherical reflective surfaces of the minor and positive mirrors for dual mirror virtual image display according to the present invention, these surfaces are designed to reduce the distortion. The area is deformed. The area of the mirrors shown in these figures is 2.54 cm (1 inch).

The aspheric surface of the embodiment of the sub-magnification mirror satisfies the following surface equation proportional to the coordinates shown in FIGS. 4A and 4B.

Where C and F (X, Y) ₁ are

i C _i F (X, Y) _i

1 -0.152819 × 10 X²-Y²

2 -0.228226 × 10 ^-2 Y (X² + Y²)

3 -0.384185 × 10 ^-2 Y (3C²-Y²)

4 -0.279668 × 10 ^-3 X⁴-Y⁴

5 -0.652462 × 10 ^-6 Y (X² + Y²) ²

And S (X, Y)

S (X, Y) = R + (R²-X²-Y²) ^1/2

And R = -30.0306 cm (-11.8231 inch)

The table below describes the data for sample points [in cm] along the aspherical surface of the sub-magnification mirror.

Minor magnification mirror surface sample points

X Y Z

+ 1 × 2.54 0 -0.057928 × 2.54

0 + 1 × 2.54 -0.025244 × 2.54

0 + 1 × 2.54 -0.028365 × 2.54

+ 1 × 2.54 + 1 × 2.54 -0.097131 × 2.54

+ 1 × 2.54 + 1 × 2.54 -0.072639 × 2.54

The aspherical surface of the positive magnification mirror used with the sub-magnification mirror described above satisfies the following surface equation proportional to the coordinate system shown in FIGS. 5A and 5B.

Where C and F (X, Y) are as follows.

i C _i F (X, Y) _i

1 -0.617592 × 10 ^-2 X²-Y²

2 -0.593066 × 10 ^-3 Y (X² + Y²)

3 -0.560451 × 10 ^-3 Y (3X²-Y²)

4 -0.206953 × 10 ^-4 X⁴-Y⁴

5 -0.181196 × 10 ^-4 Y (X² + Y²) ²

And S (X, Y) is

S (X, Y) = R- (R²-X²-Y²) ^1/2

And R = 35.9846 cm (-14.1672 inches)

The table below describes the data for sample points [in cm] along the aspherical surface of the magnification mirror.

If you look at the static mirror table,

X Y Z

+ 1 × 2.54 0 -0.04153 × 2.54

0 + 1 × 2.54 -0.029191 × 2.54

0 -1 × 2.54 -0.029089 × 2.54

+ 1 × 2.54 + 1 × 2.54 -0.73142 × 2.54

+ 1 × 2.54 -1 × 2.54 -0.068383 × 2.54

The aforementioned mirror surfaces can be used in a display system having the following parameters.

Range (R): 203.2 cm (80 inches)

Eye relief (L): 60.96 cm (24 in)

Rear focus (B): 14.478 cm (5.7 in)

System length (Z): 22.86 cm (9 inches)

Image source size: 3.175 cm x 12.7 cm (1.25 inches x 5 inches)

Virtual image size: 4 ° x 16 ° range at 203.2 cm (80 in)

The optical axes OA1 and OA2 of the aspherical elements described above have a central axis CA of the display comprising aspherical elements passing through the origins of this coordinate system, and these origins of the respective surfaces corresponding to the optical axis points P1 and P2. Follow each Z axis of each coordinate system used to define the aspherical deformation.

Referring now to FIG. 6, this figure is a simple off-axis lens system illustrating the use of “off-axis” in accordance with the present invention. Since the central axis CA, which combines the center of the object with the center of the image, does not coincide with the optical axis OA of the lens, the center axis is “off-axis” like the object and image. In the present invention, the off-axis configuration is initially set in proportion to the optical axis of the spherical element distorted as described above to form a suitable aspherical surface.

Referring now to FIG. 7, there is shown a simple lens system implementing a known axial system using a portion of an optical element, which optical axis is defined by the fundamental radius of the optical element. Although the off-axis portion of the optical element is used, the central axis that combines the center of the object with the center of the image coincides with the optical axis (OA) and thus is “axial” like the object and the image (ie, the object and image are placed on the optical axis). ).

Although the concept of an image source that includes electromechanical analog gauges has been basically described in the description, the above-described dual mirror virtual image display system may be used with larger VFD and LCD sources than those used as a single mirror system that allows more detail in graphics. It can be appreciated that they can be used together.

The detailed description has described a dense virtual image that includes a number of analog electromechanical gauges and provides relatively long viewing distances, for example, 121.92 to 365.76 cm (4 to 12 ft), and a relatively large field of view.

Although specific embodiments of the invention have been described and practiced in the detailed description, various modifications and alterations herein are made by those skilled in the art without departing from the scope and background of the invention as defined by the appended claims. It can be prepared by.

Claims (6)

In a virtual image display for a vehicle, an image source (11) for providing an imaging illumination: a planar fold mirror (13) reflecting the imaging illumination in response to imaging illumination from the image source (11) ; A negative power aspheric off-axis mirror 15 for providing divergent imaging illumination in response to the imaging illumination reflected from the planar fold mirror; Converging that generates a virtual image of the image source 11 observable by the driver of the vehicle in an observation transaction longer than the optical path distance traveled by the imaging illumination from the image source 11 to the eye of the vehicle driver. A positive power aspheric off-axis mirror 17 responsive to the divergent imaging illumination to provide imaging illumination; And the illumination reflected by the magnification aspheric off-axis mirror 17 to allow the observer to observe, and when observing outside the display system, the reflection of a dark ray trap with reflections from the observable place disposed thereon. Curved protective windows (19) of an elliptical cylinder configured to be constrained to the non-spherical mirrors (17 and 19), so that the image source and the virtual image are on the optical axis of the aspheric elements. A virtual image display for a vehicle, characterized in that it is deformed and is not spherical, so that distortion including distortion caused by their off-axis configuration is reduced. 2. The virtual image display for a vehicle according to claim 1, wherein said image source means comprises a plurality of electromechanical vehicle gauges. 2. The virtual image display for a vehicle according to claim 1, wherein said virtual image is an enlarged image of said image source (11) means. 2. The virtual image display for a vehicle as claimed in claim 1, wherein the viewing distance is in the range of about 121.92 cm to 365.76 cm (4 to 12 ft). 2. The virtual image display for a vehicle according to claim 1, wherein the sub-magnification aspheric off-axis mirror includes a sub-magnification mirror having a convex reflective surface. 6. The virtual image display for a vehicle according to claim 5, wherein the constant magnification aspheric off-axis mirror includes a constant magnification mirror having a concave reflective surface.