JPH03180810A - Double mirror false image display device for automobile instrumentation - Google Patents

Abstract

PURPOSE: To read two or more gauges or large meters like analog meters at a proper virtual image distance by combining an off-axis mirror which has a negative power and is formed to an asphercal face and an eccentric mirror which has a positive power and is formed to an spherical face to constitute an observation optical system. CONSTITUTION: A virtual image display device of meters for vehicle is arranged in the front of a steering wheel, and light of an illuminated image from a image source 11 diverges and is reflected by a turning-back mirror 13 and is made incident on a negative-power mirror 15 formed to an eccentric convex. Light of the image from this mirror 15 is made incident on a positive-power mirror 17 formed to an eccentric concave, and the mirror 17 has a positive power to enlarge the image. Light of the image reflected by the mirror 17 reaches an observer through a protection window 19. Thus, the negative mirror 15 and the positive mirror 17 are used to obtain proper enlargement, virtual image distance, visual field, and optical characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates generally to virtual image displays, and more particularly to virtual image displays for vehicle instrumentation that provide a large field of view for image source structures of different dimensions.

BACKGROUND OF THE INVENTION Traditional instruments for vehicles, such as automobiles, typically include direct viewing instruments supported on a dash board in front of the steering wheel.

Although such traditional direct observation instruments are simple and effective, they require the operator's eyes to be refocused between road observation and instrument observation. Additionally, traditional direct viewing instruments typically operate with a close enough optical path length (approximately 24 to 30 inches) to be difficult to read by an adult operator using reading glasses for close objects.

[Problem to be solved by the invention] Document 'Automotlve JnStrulerlt'
commonly assigned U.S. Patent Application No. 07109B for Virtual IIIageDisplay;
No. 870, filed September 4, 1987, describes an instrument virtual image display system that effectively positions the virtual image of the instrument at an effective position that is optically further away from the operator than traditional direct viewing instruments. . The position of the virtual image away from the operator is achieved by a single positive magnifying mirror. However, image sources that can be used with a single positive mirror system typically have a fairly short system length (i.e., from the image source to the mirror) that does not allow for more than one or more instrument gauges or readers. must be very small in order to maintain the distance 11i1).

Also, relatively large image sources such as electromechanical devices cannot be used.

Accordingly, it would be advantageous to provide a vehicle instrument virtual image display that can include more than one gauge or reader display.

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

SUMMARY OF THE INVENTION The above and other advantages provide that the image illumination provides an image and a vehicle operator with a viewing distance greater than the optical path length traveled by the image illumination from the image source to the vehicle operator's eye. a virtual image display for a vehicle according to the present invention.

EXAMPLES In the following detailed description and in the drawings, like elements are designated by the same reference numerals.

Referring to FIG. 1, a virtual image display system for a vehicle according to the present invention is shown. The virtual image display device can be located, for example, in the area traditionally occupied by the instrument panel, for example above the vehicle steering column and in front of the steering wheel.

The display system includes an image source 11 and a planar fold mirror 13 responsive to image illumination from the image source 11. Planar fold mirror 13 reflects the image illumination to an off-axis convex negative power mirror 15 which provides divergent reflected illumination. The mirror 15 is characterized by having a negative power to reduce the image when directly observed, and is further characterized by providing a divergent reflection since the incident parallel light rays diverge upon reflection.

Illumination from negative power mirror 15 is incident on an off-axis concave positive power mirror 17 which provides focused reflected illumination. The mirror 17 is characterized by having positive power to magnify the image, and is further characterized by providing a focused reflection because the incident parallel light rays are focused upon reflection.

The illumination reflected by the positive power mirror 17 reaches the viewer through the curved protective window 19. The curved protective window 19 is configured such that, particularly when viewed from outside the display system, the reflections that can be seen by the observer are limited to the reflections of a dark light trap located above the protective window. The recess of the cylinder is shaped into a negative and oval shape.

Negative and positive power mirrors 15 and 17 have astigmatic, non-rotationally symmetrical reflective surfaces and may include, for example, gold-hardened plastic substrates.

The astigmatic elements 15 and 17 each have an optical axis OAI and OA2 with the optical axis defined by the basic radius of the respective reflective surface before being astigmatically distorted. The optical axis passes through optical axis points P1 and P2, which are used as the origin of each coordinate system used to define non-flat distortions in each plane. In other words, the target is distorted.

With respect to the reflective surface of the negative mirror 15, the optical axis OAI connects the image center and the image source center and divides into three equal parts the incident and reflected portions of the central axis CA defined by the rays passing through the optical axis points pt and P2. . For the reflective surface of the positive mirror 17, the optical axis OA2 is also off-axis since the central axis CA is not in line with the optical axis, and the image source and image are astigmatic, including any reflective folds. It is not on the optical axis of the aberration element.

The central axis CA further limits the optical path through which the image illumination from the image source travels to the vehicle operator's eyes, and as discussed herein, such optical path also limits the effective viewing distance of the virtual image! (i.e. the distance 1 at which the operator's eyes focus to see the virtual image)
1ft).

While conventional systems use a mirror that includes an astigmatism section of the sleeve of the ball or a vertebral body (e.g. a parabola), such systems use a mirror that includes an astigmatism section of the sleeve of the ball or a vertebral body (e.g. a parabola); It should be noted that the image source is located on the optical axis. This is done to maintain some rotational symmetry for ease of assembly. However, this limits the properties of such optical systems by limiting the degree of astigmatism that can be imparted to the mirror surface. The optical system according to this invention is not symmetrical from the axis,
Take any shape that improves the overall virtual image properties. This additional design freedom makes the invention better than conventional design features.

Negative mirror 15 is a small mirror that makes sense for an enlarged virtual image without changing the dimensions of image source 11 or the virtual image distance (i.e. the effective distance at which the observer's eye focuses to see the virtual image). It is positioned with respect to the large positive mirror 17 according to a relatively simple optical formula (such as in a Cassgrain telescope) to obtain a large magnification distance. According to the present invention, the virtual image distance is approximately 4 to 12 feet, which is greater than the typical distance between the driver's eyes and direct viewing instruments in the instrument panel.

The use of negative and positive mirrors provides adequate magnification, virtual image distance, field of view and optical properties (i.e. reduced distortion and disparity), making the optical system more compact than a single positive mirror system with comparable parameters. (i.e., the distance #I between the image source and the mirror optically closest to the nominal eye position) is maintained. In other words, for a given magnification, virtual image distance, field of view and optical properties, the described dual mirror system has a shorter system length and therefore a smaller optical package than a comparable single positive mirror system.

The compactness of the dual mirror system results from the inverted telephoto arrangement of the negative and positive mirrors, which increases the working focal length without significantly increasing the system length. The working fish point length is, as is well known, a "first fundamental plane" in which a single lens or mirror is placed in such a position as to produce a single lens or mirror optical system with substantially the same parameters. The distance from the image source to

The first principal plane for a dual mirror system is located between the nominal eye position and the optically closest mirror, while the first principal plane for a single positive mirror system is located at the mirror. be done. In other words, the first fundamental plane for the dual mirror system is limited to being at one physical location of the optical element.

The factors that enable the double mirror system to achieve a more compact system length can be better understood by comparing the single and double lens systems shown in Figures 2 and 3, respectively, which are An essentially unfolded variant of the lens system and double mirror system that is easy to understand. Suitable optical parameters are as follows.

Distance NCR): Distance from the nominal eye position to the virtual image.

Eye Relief (L): Distance from the nominal eye position to the first lens surface.

Eyebox (Y): The diameter of the space around the nominal eye position in which the virtual image can be observed without blurring.

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

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

Back focus (B): distance from the image source to the lens closest to the image source.

Operating focal length (F): distance from the image source to the first fundamental plane of the optical system.

Working Diameter (D): Diameter of the first basic plane.

Operating F number (F/#): ratio of operating focal length to operating diameter (
i.e. F/D).

Image source dimension (H): height of the image source (in the vertical plane)
.

Virtual image size (Hl: height of virtual image (in vertical plane)
.

Each optical property of single and double lens systems (ie, distortion and disparity reduction) is directly related to the operating F-number F/#. In particular, the performance deteriorates when the operating F number F/# is decreased. Therefore, the operating F number F/# is generally fixed for a given characteristic specification. It is also desirable that the system length Z be as short as possible to minimize the optical package.

For the single lens system shown in FIG. 2, the working focal length F1 back focal length B and system length 2 are equal. The working diameter is the diameter of the lens. For a given distance MR, eye relief L1 eye box Y, and field of view FOV, the operating diameter can be expressed as follows.

D-2Ltan(FOV/2)+Y(1-L/R)(Formula 1) %Formula% D-2Ltan(FOV/2)+Y
(Equation 2) The required image source dimension H is the understanding that the ratio of the virtual image dimension H'' to the image source dimension H is equal to the ratio of the image distance (lens to image) to the image source distance (lens to image source). can be determined by

H-(2Rtan(FOV/2)F)/(R-L)(
Formula 3) % Formula % H-2F tan (F OV /2) (
Equation 4) Therefore, for a particular FOV, distance, eyebox and eye relief requirement, the working diameter is defined by Equation 1. Since the operating F number F/# is minimized and fixed for the specific property requirements, the operating focal length is also fixed (since F-DF/#) and the image source size is given by Equation 1
Determined by.

A single lens system provides suitable properties where the image source can be arbitrarily sized to meet the source size requirements discussed above. Such sizing allows the image source to be easily modified such that the dimensions of the graphics are small enough.
) or a vacuum fluorescent display (VFD). However, electromechanical instruments cannot be reduced to smaller dimensions than one inch in diameter, for example. Regarding size constraints for analog image sources, the above equations need to be applied backwards starting from a given image source size.

If the analog gauge is larger than the image source size derived by the equation, then both the working focal length and FOV are fixed at a constant working FOV.
Must be incremented for number F/#. If the FOV must be constant, the working diameter must also be constant;
The only way to use a larger image source size is to increase F/#. This also increases the operating focal length (larger than if the FOV could be increased)
.

If an analog gauge image source cannot be made as small as an LCD or VFD source, as a result the system length must be increased for a single lens system when an analog gauge is used as an image source. . Longer systems mean longer boxes and an overall increase in optical package size.

Consider the double lens system of FIG. 3, which is an unfolded version of the two ffl mirror system shown and functions as an inverted telephoto structure that increases the working focal length without increasing the system length. For simplicity, we define the distance to infinity as described above for a single lens system. The focal lengths of the two lenses are fl and fl, where fl is a positive focal length and fl is a negative focal length. The distance between the two lenses is
It is.

Therefore, the operating focal length of this system is F-(fl
)(fl)/(fl+f2-x) (Equation 5) As can be seen in FIG. 3, the focal length actually exceeds the system length. By varying fl and fl, the focal length becomes substantially independent of the back focal point and system length.

The distance fiL1 from the nominal eye position to the first basic plane is: L1 blink + B-F (Equation 6) Furthermore, the operating diameter is: D = 2 L l jan (F OV /2) +
Y (Equation 7) When solved for an image source size H with an infinite distance R, Equation 7 reduces by 4 as follows.

H-2Fjan(FOV/2) (Equation 8) This is the same as Equation 4.

If the image source dimensions are varied while keeping the operating F number F/# and field of view FOV constant, the operating focal length is defined by Equation 8. The operating diameter is determined by the operating F number F/#. LL is determined by Equation 7. Therefore, equation 6 can be solved for the system length ff1(x+B).

As an example of the difference between single and double lens systems, the optical parameters for single and double lens systems are calculated for the following system constraints:

R→--24 Y-2,5 FOV-3° For reasonable characteristics, the operating F number F/# must be less than 2°O.

Using equation 2 for a single lens system, the working diameter is 7
．． It must be 3,75 inches which requires a sunspot length (from F/#-F/D) of 514 inches, which is also the system length since for a single lens system the system length is equal to the working focal length. From Equation 4, the image source size must be 0.394 inches.

In the following, we consider the use of an analog gauge package with dimensions of 1 inch as an image source. FOV of equations 4 and 3@
, the focal length must increase to 19.094 inches. This is a 150% increase in system length. The working diameter is 3.75 finches, providing an F/# of 5.082.

If the system length of 19.094 inches cannot be tolerated, the FOV can be changed to reduce the focal length. In equation 2, the focal length F is CD )(
By substituting F/#) and replacing D from Equation 2, we can relate the image source to the motion F number F/# and FOV.

H= (2F/Lu tan (POV/2)) [2L t
an(FOV/2)+Y] (Equation 9) When solved for the FOV in the above quadratic equation (with the operation F number F/# fixed at 2,0 for this example), 5.803 The value of is obtained. Substituting that value into Equation 4 yields a working focal point of 9.865 inches and 4.93 inches.
A working diameter of 3 inches results. System length is 9.865 (still larger than the original of 7.514 inches for a small source size of 0.394 inches)
while the working diameter increases from 3.75 inches to 4.933 inches (31% larger). Therefore, even with a new FOV, the overall size of the system increases.

Below, we consider the dual lens method for an image source size of 1 inch. From Equation 8, the working focal point is 19. [It is 194 inches. Distance M between two lenses
Setting x to 3 inches and system length to 7.514 inches (shortest possible single lens design for the specified eye relief above 1 eye box Y and field of view FOV), the back focal point is 4.514 inches. . From Equation 6, Ll is equal to 12.42 inches. Although the focal length of each lens varies with respect to each other, one solution to Equation 5 says that f
1 is 7.5B8 inches, and [2 is -7,568 inches.

Since the dimension of fl is equal to the working diameter of a single lens system of 3.757, the F/# of fl is 2.014.

From the above comparison, it can be seen that for a specified image source size with optical specifications such as distance, FOV, etc., a double lens system provides a system length comparable to a single lens system with a small image source size. Should. It is pointed out that the optical properties are better than the single lens method since there are two lenses to be optimized, since the operation F number F/# of the individual lenses in a double lens system is not very fast.

Regarding the structure of the double-mirror virtual image display system, the above analysis of the double-lens system can be used to arrive at a first-order design, followed by an optical transformation into a spherical mirror deformation of the first-order design. A design computer program is used.

The computer program deforms the nominal spherical surface to meet the desired criteria of minimizing distortion when viewed in the eyebox.

Since the eyebox and virtual image are off-axis with respect to the respective axes of the two mirrors, the astigmatism surface equation can be adjusted independently of the axis joining the eye and virtual image. This provides greater latitude in the design process and better corrects optical aberrations and distortions. Such distortions can cause vertical disparity and magnification changes that are problematic in the final design.

4A, 4B, 5A and 5B, embodiments of astigmatism are shown to reduce surface distortion. Regarding the mirrors shown in these drawings and the coordinate system shown in FIG. 4B, the following equations are satisfied.

here, and F (X.

Y) is as follows be.

-0,652462x 10-6 A(x2+Y2)2 Also, (X.

Y) teeth, (X.

Y) -R+ (R2 ＋　X　2 + Y 2 ) ・Sample point (inch) Show the data for.

Negative mirror surface sample point -0,057928 -0,025244 -0,028365 -(), 097131 -0.072639 Regarding the coordinate system, the following surface equation is satisfied.

Here, C and F (X.

Y) is as follows be.

F(X, Y).

Also, (X.

Y) teeth, (X.

Y) R- (R2 X 2 2 ) point (inch) Show the data for.

-0,041533 -0,029191 -0,0290E19 -0.073142 -0.068383 The mirror surface described above can be used in a display system with the following parameters.

Distance 111R: 1110 inches Eye relief L: 24 inches Back focal point B: 5. Finch System Length 229 inches Image Source Dimensions: 1.25X 5 inches Virtual Image Size = 4" It should be understood that such a coordinate system passes through the origin, and such an origin corresponds to the optical axis point PL, P2.

Referring to FIG. 6, a simple off-axis lens system is shown illustrating the use of "off-axis" according to the present invention. The central axis CA connecting the center of the object and the center of the image does not coincide with the optical axis OA of the lens, so the central axis is "off-axis" like the object and the image.

In the present invention, an off-axis structure is first set with respect to the optical axis of the spherical element which is subsequently distorted as described above to form a suitable astigmatic surface.

Referring to FIG. 7, a simple lens system is shown representing a known on-axis system using a portion of the optical element that is positioned off-axis with respect to the optical axis of the optical element; is limited by the fundamental radius of the optical element. Although the off-axis portion of the optical element is used, the central axis connecting the center of the object and the center of the image coincides with the optical axis OA and is therefore "on-axis" as the object and the image (i.e., the center of the object and the image is on the optical axis).

Although the above is primarily concerned with the content of image sources including electronic and mechanical analog gauges, the disclosed two-ffi mirror virtual image display system can be used with VFD and LCD sources larger than those used in a single mirror system. It should be understood that this allows for densification of the graphics.

In the above, a compact virtual image display system is disclosed that includes a plurality of analog electronic and mechanical gauges and can provide a relatively large viewing distance and a relatively large field of view, e.g., from about 4 to 12 feet. .

Although specific embodiments of the invention have been described and illustrated above, those skilled in the art will appreciate that various modifications and changes can be made without departing from the scope of the invention as defined by the claims. I can do it.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a virtual image display device. FIG. 2 is a front view of a single lens display system that is helpful in understanding the virtual image display of FIG. FIG. 3 is a non-folded version of the virtual image display of FIG. 1 and is a top view of a dual lens display system that is helpful in understanding the virtual image display of FIG. 4A and 4B are side and front views of an embodiment of the negative power mirror of the virtual image display of FIG. 1; FIG. 5A and 5B are side and front views of an embodiment of the positive power mirror of the virtual image display of FIG. 1; FIG. FIG. 6 is a schematic diagram illustrating an off-axis lens system useful in understanding the off-axis structure of the virtual image display of the present invention. FIG. 7 is a schematic illustration of an on-axis lens system using an off-axis portion of a lens that is helpful in understanding known off-axis systems that use an off-axis portion of an optical element.

Claims (10)

[Claims] (1) an image source that provides image illumination; a negative power astigmatic off-axis optical means responsive to the image source image illumination that provides divergent image illumination; and an optical path length that the image illumination follows from the image source to the vehicle operator's eye. positive power aspherical off-axis optical means responsive to said divergent image illumination to provide a focused image illumination that produces a virtual image of said image source viewed by a vehicle operator at a greater viewing distance; The aspherical optical means is off-axis, so that the image source and the virtual image are not located on the optical axis of the aspherical element, and the aspherical optical means is off-axis so as to reduce distortions, including distortions produced by off-axis structures. A virtual image display device for cars that is visually distorted. 2. The virtual image display system of claim 1, wherein said image source means includes a plurality of electronic and mechanical vehicle instrument gauges. (3) The virtual image display device according to claim 1, wherein the virtual image is an enlarged image of the image source means. 4. The virtual image display of claim 1, wherein the viewing distance is approximately 4 to 12 feet. (5) The virtual image display device according to claim 1, wherein the negative power optical means comprises a negative mirror having a convex reflective surface. (6) The virtual image display device according to claim 5, wherein the positive power optical means comprises a positive mirror having a concave reflective surface. (7) an image source providing image illumination; and a negative power aspheric off-axis mirror responsive to the image source image illumination providing divergent image illumination, the image illumination being greater than the optical path length traveled from the image source to the vehicle operator's eye. a positive power aspherical off-axis mirror responsive to the divergent image illumination to provide a focused image illumination that produces a virtual image of the image source observed by a vehicle operator at a viewing distance, the aspherical mirror comprising: off-axis, whereby the image source and virtual image are not located on the optical axis of the astigmatism element and are aspherically distorted to reduce distortion, including distortion produced by off-axis structures. A virtual image display device for automobiles. 8. The virtual image display system of claim 7, wherein said image source means includes a plurality of electronic and mechanical vehicle instrument gauges. (9) The virtual image display device according to claim 7, wherein the virtual image is an enlarged image of the image source means. 10. The virtual image display device of claim 7, wherein the viewing distance is approximately 4 to 12 feet.