JP2003502712A - Illumination system for eyepieces and face mask display systems - Google Patents

Abstract

(57) Abstract: A display illumination and viewing system having an illumination optical path and a viewing optical path coincident along a portion of its overall length (FIG. 4). The display (60) is located at one end of the match. The first lens system is located on the matching path portion, and the second lens system is located on the viewing optical path. The illumination assembly is located on the illumination optical path and is offset from the coincidence. The lighting assembly is separated from the first lens system by a distance corresponding to a focal length of the first lens system. The reflective and transmissive elements reflect light from the illumination assembly in the direction of the display toward the coincident path portion of the optical path, and transmit the light from the display along the viewing optical path to form the coincident path section. Are located at the opposite ends. According to another aspect of the invention, the invention is an image display system operable in a color mode and a monochrome mode. The illumination circuit (FIGS. 8-11) includes a switch connected to the illumination source and operative to switch the illumination source between a color mode for performing color display and a monochrome mode for performing monochrome display.

Description

Detailed Description of the Invention

CROSS REFERENCE TO RELATED APPLICATIONS This application is incorporated by reference in US provisional application 60 / 140,327, dated June 21, 1999, 35 U.S.P. S. Claims C.112 (e) benefit priority. The entire contents of the above application are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT The development of this invention was sponsored by R & D contract DAAN 02-98-C-4026. The US Government may have several rights in this invention.

BACKGROUND OF THE INVENTION Miniature active matrix liquid crystal displays (AMLCDs) require an illumination source. For systems using transmissive AMLCDs, the light source is placed after the display. In FIG. 1, the transmissive AMLCD 10 is a light emitting diode (LEC).
1 shows a simple prior art method with a backlight 20. Light rays 30 from the backlight propagate through the AMLCD and are modulated to form an image. In the case of some AMLCDs, the color is generated by AMLC in the red, green and blue subframes.
This is done by sequentially loading in D and sequentially illuminating the red, green and blue light emitting diodes simultaneously. Sequential illumination is achieved by supplying current sequentially through one of the required light emitting diode leads 40. A beam shaping element 50, such as a Fresnel lens, can be used to collimate the light. Other elements such as diffusers or filters can also be used. AMLCDs and illuminators of this type are commercially available from Copin Corporation. A viewing system, such as a display, can comprise simple optical magnifying optics, or a multi-stage image optical system featuring intermediate image planes located between each stage.

Prior art miniature reflective AMLCDs (FIG. 2) use an illumination system based on a beam-splitting cube 70 adjacent to display 60. beam·
The splitter can be provided with a polarization splitting coating 71 which serves to linearly polarize the illumination light and also acts as an analyzer for the liquid crystal display. Alternatively, the polarizing beam splitter can be formed from a polymer film. Using a transmissive AMLCD, the optics 50 can be used to collimate, diffuse, or filter the illumination.

FIG. 3 illustrates a more complex prior art reflective A including a compact and simple magnifying device attached to a lighting system for viewing a magnified image of display 60.
1 shows an MLCD system (US Pat. No. 5,596,451). In the case of this prior art device, a compact system is formed by using one beam splitter 71 for illuminating and viewing the image from AMLCD 60. The beam splitter 71 is used to illuminate and view images, but the mirror 42 for magnification is not used in the optical path of the illumination system. No lenses or mirrors are required to influence the separation and movement of the illumination light. This is because the light source 34 in this design is a wide area emitter.

In the case of reflective AMLCDs, projection systems have traditionally used efficient illuminators based on lamps and collimation optics. The collimating optics provide efficient and uniform illumination of reflective displays (see, eg, US Pat. No. 6,036,318). This type of collimation system is heavy and bulky due to the extra lenses and optical paths required, and therefore is not used in head-mounted displays.

Collimated illumination optics are commonly used in projection systems that use high intensity lamps and projection lenses as disclosed in US Pat. No. 5,949,503. In some cases, such as the above-mentioned US patents, part of the projection optics can be used for illumination. In the case of projection systems, this method improves the illumination uniformity of the projected image and improves the contrast.

SUMMARY OF THE INVENTION The present invention relates to improvements in lighting systems such as reflective liquid crystal displays. The above improvement is based on the use of a set of optical elements for the two purposes of combining the illumination system and the magnification system, thereby magnifying the image and illuminating the display. The invention also relates to a system for obtaining high brightness monochrome images that can be applied to reflective or transmissive liquid crystal displays.

More specifically, the present invention provides a display illumination and viewing system that includes an illumination optical path and a viewing optical path. At least a portion of the illumination optical path is coincident with the viewing optical path to form the coincident optical path portion. A display comprising an active matrix liquid crystal display is located at one end of the coincident part of the optical path. The first lens system is located on the coincident portion of the optical path and forms an image plane on the viewing optical path. The second lens system is located on the viewing optical path.

Illumination assemblies, such as red, green and blue light emitting diodes, are located on the illumination optical path and are offset from the coincident portion of the optical path. The lighting assembly is separated from the first lens system by a distance corresponding to the focal length of the first lens system. Reflective and transmissive elements, such as beam splitters, reflect light from the illumination assembly toward the display, towards a coincident portion of the optical path, and direct light from the display along the viewing optical path. At the opposite end of the coincident portion of the optical path. In this way, the present invention provides a collimated illumination system for head-mounted reflective AMLCDs that is lighter and more compact than prior art systems and provides uniform and efficient illumination.

According to another aspect, the invention is an image display system capable of operating in color and monochrome modes. The display system comprises an active matrix liquid crystal display capable of operating at constant speed with sequential loading of red, green and blue subframes. An illumination source consisting of red, green and blue light sources, such as light emitting diodes, is arranged to illuminate the active matrix liquid crystal display. The illumination circuit is connected to the illumination source and includes a switch that operates to switch the illumination source between a color mode for color display and a monochrome mode for monochrome display. Therefore, the brightness of the present invention is improved by providing the function of switching the lighting device to monochrome mode. Furthermore, according to another aspect, the present invention also adjusts the brightness of the lighting device.

A better understanding of the present invention may be gained from a reading of the following detailed description with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises an integrated viewing optics and illumination optics of a single or multiple stage optical system. The term integrated is used for viewing optics and also serves to collimate the light in the illumination system, thereby making it possible to separate the movement of rays used to reduce cost, weight and size. Means the integration of some of the influencing optical elements.

To provide some background knowledge of the present invention, FIG. 4 shows a display system using the prior art collimation system of FIG. The lighting system 22 is connected to the viewing system 23 to provide images to the viewer. The illumination system comprises red 53, green 54 and blue 55 light emitting diodes, an optional diffuser 49, a Fresnel lens 50, and a polarizing beam splitter 71. Illumination from the light emitting diode, if a diffuser is used, passes through the diffuser and is collimated by the Fresnel lens 50 to evenly illuminate the AMLCD 60. The reflected polarization is directed by the beam splitter 71 towards the AMLCD. At each pixel of the AMLCD, the polarization of light is rotated through an angle by an electrical signal representing an image. The rays are from the illumination stage 22 to the expansion stage 2
3 through the lens 150 and 160 to form an image. Any number of optical surfaces can be used to magnify the image and correct aberrations. To simplify the drawing, the lens surfaces will be represented by a single lens 150 and 160. In practice, each of these lenses 150 and 160 is an achromatic doublet or triplet, an aspherical, or more complex combination of surfaces, respectively.

5a and 5b show the main parts of the invention. The reflective AMLCD 60 will be viewed through a two-stage magnification lens system, represented by lens system 150 and lens system 160. A line of sight path is formed from the AMLCD to the user's eye through lens system 150 and lens system 160. A characteristic of each lens system is the focal length f. Referring to FIG. 5a, according to Newton's lens equation (N · P = f ₁ · f ₂ ),
Lens system 150 forms an intermediate image plane, as shown between 150 and 160, a portion of which is given by Newton's lens equation or equivalents well known to those skilled in the art. . When the lens system 160 is located some distance from the image plane, which is equal to its focal length, the user sees the image at infinity. The position of the lens system 160 can be moved to change the distance of the virtual image. The extension of the system is represented by the product of the above two stages of magnification, as is known to those skilled in the art.

5a and 5b illustrate the insertion of reflective and transmissive elements, such as beam splitter 200, between lens systems 150 and 160.
A beam splitter, as known to those skilled in the art, is a polarizing beam splitter that can be made by vacuum depositing multiple layers of thin films,
Alternatively, a polarizing beam splitter can be used that can be made by polymer technology (eg, a product offered as 3M), or a vacuum-deposited thin metal film (half-silver mirror) that is about 50% transparent. You can also do it. Alternatively, a polarized beam splitting cube can be used. 5b, it can be seen that the purpose of the beam splitter 200 is to reflect light from an illumination source, such as a light emitting diode lamp 100. The light emitting diode lamps may be multiple color lamps with red, green and blue light emitting diodes used in electric field sequential color lighting devices to the optical path. Light emitting diode lamp 10
The path between 0 and AMLCD 60 forms the illumination path. From the figure it can be seen that the illumination formation coincides with part of the browsing path. When the light emitting diode is installed at a position equal to the focal length f ₂ of the lens system 150 from the lens system 150 (indicated by distance a + b in FIG. 5b), the lens system 150 collimates the light. , Thereby improving the uniformity of illumination on the AMLCD 60. Diffusers and other optical elements can be used between the light emitting diode and the beam splitter to homogenize the light incident on the AMLCD or to develop long light sources depending on the viewing requirements of the entire system.

FIG. 6 shows an example of an optical design based on this main member. Lens surface 150, 1
60 is a non-spherical shape well known to those skilled in the art, and is represented by the following formula.

[0018]

[Equation 1]

In this case, the coefficient is the numerical value shown in Table 1. Table 2 is a summary of the optical specifications for the imaging path (between the display 60 and the pupil). Table 3 is a summary of the definitions for the lighting path (between the lamp 100 and the display 60).

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023] These designs can be lightweight because they do not require a separate lens to collimate the light from the light emitting diodes. Referring to FIG. 4,
From this figure, it can be seen that the collimating lens 50 (of FIG. 4) is not used and the distance related to its focal length is shortened, resulting in a smaller size and lighter weight.

FIG. 7 illustrates the use of the present invention in an eyepiece display of the type disclosed in US Pat. No. 5,886,822. The housing 170 for the reflective display 60 and magnifying lens system 150 is located near the eyepiece 210. The display 60 is illuminated by the light source 100. Lens system 150 projects into the image plane at the input pupil of the optical system in lens 210. The lens 210 is an enlarged internal optical relay formed by the lens 220,
Polarizing beam splitter 240, quarter wave plate 260 and concave mirror 2
Together with 50, it provides an image that is visible to the user's eyes in front of the lens 210 at a convenient viewing distance.

In the above description, an image source in the form of a light emitting diode or an array of light emitting diodes has been described, since the light emitting diodes are the usual light source in these displays. Many other illumination sources may also be used, including lasers, fiber optics that deliver light from a remote image source, or other lamps.

The use of sequential red, green and blue illumination in an eyepiece system of the type of FIG. 7 produces excellent color images. However, the use of light emitting diode sequential illumination reduces the utilization of the light emitting diodes, thereby reducing the total amount of light delivered to the eye. In the case of a system of the type of FIG. 7, which uses the beam splitter 240 as a combiner to combine the surrounding landscape with the light rays from the display, the viewer is as if the ambient sunlight was bright. May require very bright images.

For many applications, such as the eyewear displays above, color displays for certain images, and other images for viewing in bright ambient light that do not require color. You need a bright display. In order to make a sequential color display very bright, the invention also implements a high brightness monochrome mode at 100% utilization, including the step of powering the red, green and blue light emitting diodes simultaneously. Including a method for doing.

In one embodiment of the invention of FIG. 8, light emitting diodes 301, 302, 3
03 is turned on continuously, in which case AMLC using switch 300
The frame rate of D does not change at all. When all three light emitting diodes emit light sequentially and simultaneously, a portrait of a black and white image is formed, in which case
White is brighter than any color due to the emission of sequential light emitting diodes in red, green and blue.

Simultaneous light emission can be performed by using the switch 300 of FIG. 8 applied to the power circuit of the lighting device. When the switch is set to a position, the light emitting diode is connected to the sequential color driving circuit in the backlight controller. If set to another position, the light emitting diode is connected to the current source. FIG. 8 shows a current source including V _DD , light emitting diodes 301, 302, 303, current limiting series resistors 311, 312, 313 and ground. However, other circuits can be used to supply current to the light emitting diodes. Since the switch 300 supplies current to the light emitting diodes continuously and simultaneously, the usage rate of each light emitting diode is at least tripled. This technology is based on transmissive AMLCD
(FIG. 1) or reflective AMLCD illuminator (FIG. 2).

FIG. 9 shows another embodiment. The switch 350 is used to provide a logic input to the display controller 330 to control the light emitting diode. The display controller 330 provides the illumination signal to the light emitting diodes along the path 319 through OR gates 304, 305 and 306. O
The logic output from the R gate is supplied to the gates of the control transistors 307, 308, 309. The transistor allows current to flow through the light emitting diode in accordance with the logic signal sent on path 319. Switch 350 is used to select the operating mode of the lighting device. When set to the left position (ground), the input of the OR gate is held at ground potential and the control signal on path 319 fully controls the light emitting diode. When set in the central position, the OR gate inputs 321, 322 and 323 are held at the V _DD potential, which means that the output of the OR gate is held high, which results in the path Whatever the signal on 319, it means that the light emitting diode emits light continuously. If switch 350 is set to the rightmost position, line 321,
322, 323 are held at a number established by logic within the display controller or another logic path (not shown) from other control circuitry.

The third embodiment (FIG. 10) comprises a switch 310 that provides a logic signal path 320 to the AMLCD display controller. The logic signal on line 320 signifies the user's selection of high intensity monochrome mode. This signal causes the controller logic to reduce its power consumption in memory and elsewhere, and to use it to optimize the balance of red, green, and blue information that forms a monochrome image. Adjust.

Another embodiment of the invention comprises circuitry that allows the microprocessor to select a background color. In general, by operating the red, green and blue light emitting diodes at full brightness, high brightness black and white can be displayed as described above. By controlling the current balance between the three light emitting diodes, the backlight can be any color. White and black can be used as the main high intensity lighting, but if the application running on the computer chooses to do so, it will display a black and red background to alert you. The color of the light can be switched to red, for example. This switching can be done by supplying power only to the red light emitting diode.

It should be noted that the light emitting diode does not have to be continuously illuminated in monochrome mode, or operated in color mode at its full utilization. The above logic device can be used to reduce the utilization in order to reduce the brightness in monochrome or color mode. FIG. 12 shows a method of performing the above brightness control. A signal is emitted from the display controller 330 to cause one of the light emitting diodes to emit light. The path 451 simultaneously supplies the pulse to the monostable multivibrator 400. For example, the light emitting diode 30
The signal for causing 3 to emit light is sent from the display controller 330 to the AND gate 403 through the OR gate 306. AND gate has pulse 42
Only pass the illumination signal while the 0 is present. This pulse 420 is initiated by the multivibrator 400 when it receives a start pulse from line 451. The duration of the pulse is controlled by the setting of potentiometer 410 under the control of the system user. If the pulse width time is t, the corresponding AND gate is held open for the corresponding time t and the light emitting diode emits light for the time t. Therefore, the width of the pulse from the multivibrator 400 controls the usage rate of the light emitting diode, that is, the brightness. FIG. 11 shows
It is shown that the signal from the AND gate is sent through a series resistor 413 which controls the current flowing through the set of matching field effect transistors 460. Note that the pulse width t can be provided by the display controller or can be controlled by an additional logic path (not shown) by a logic signal that can be provided by the monostable multivibrator. .

The lighting circuits of FIGS. 8-12 can be implemented in individual logic devices, programmable logic devices, or custom integrated circuits. Alternatively, the circuit can be built into the display controller. The circuit can be configured to control another illumination source, such as a laser diode.

The invention is not limited to the details and figures described above, but only by the appended claims.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a prior art transmissive active matrix liquid crystal display illumination system.

FIG. 2 is a schematic diagram of a prior art reflective active matrix liquid crystal display illumination system.

FIG. 3 is a schematic diagram of a lighting system including a magnifying device of a reflective active matrix liquid crystal display of the prior art.

FIG. 4 Display with built-in lighting system and viewing system
System.

5a and 5b are schematic illustrations of optical components of a display system of the present invention.

FIG. 6 is a schematic diagram of the optical design of the display system of FIGS. 5a and 5b.

FIG. 7 is a schematic diagram of a display system of the present invention comprising an eyepiece display.

FIG. 8 is a block diagram and circuit of a lighting control system of the present invention.

FIG. 9 is a block diagram and circuitry of another embodiment of the lighting control system of the present invention.

FIG. 10 is a block diagram and circuitry of yet another embodiment of a lighting control system of the present invention.

FIG. 11 is a block diagram and circuitry of yet another embodiment of a lighting control system of the present invention.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/64 511 H04N 5/64 511A F term (reference) 2H087 KA00 KA14 LA12 LA24 PA01 PA02 PA17 PB01 PB02 QA02 QA03 QA06 QA07 QA12 QA21 QA32 QA33 QA41 RA05 RA12 RA13 RA41 RA45 UA01 2H088 EA10 HA10 HA24 HA28 MA01 MA06 MA20 2H091 FA10Z FA31X FA31Z FA41Z FA45Z FA46Z GA13 LA11 [Continued Summary]

Claims (29)

[Claims] 1. A display illumination and viewing system in which at least a portion of the illumination optical path and at least a portion of the viewing optical path are matched to form a matched path portion. A display comprising an active matrix liquid crystal display located at one end of the matching portion; a display located on the matching path portion having a first focal length and an image plane on the viewing optical path. A first lens system for supplying, a second lens system located on the viewing optical path, a second lens system located on the illumination optical path and offset from the coincident path portion, the first lens system An illumination assembly separated from the first lens system by a distance corresponding to a first focal length of the lens system; Reflective elements located at opposite ends of the coincident path portion for directing light from the display along the viewing optical path toward the direction of splay and along the viewing optical path. And a transmissive element, a display illumination and viewing system. 2. The display lighting and viewing system of claim 1, wherein the lighting assembly comprises red, green and blue light emitting diodes. 3. The display lighting and viewing system of claim 1, wherein the lighting assembly comprises red, green and blue laser diodes. 4. The display illumination and viewing system of claim 1, further comprising another optical element on the illumination optical path. 5. The display illumination and browsing system of claim 4, wherein the other optical element comprises a diffusing device. 6. The display illumination and viewing system of claim 1, wherein the reflective and transmissive elements comprise beam splitters. 7. The display illumination and viewing system of claim 6, wherein the beam splitter comprises a polarizing beam splitter. 8. The display illumination and viewing system of claim 6, wherein the beam splitter comprises a plurality of thin film layers, or a thin film metal layer, or a semi-silver mirror, or a beam splitting cube. Display lighting and viewing system characterized by. 9. The display illumination and viewing system of claim 1, further comprising a housing, the display, the first lens system, the lighting assembly, and a reflective and transmissive body supported within the housing. Display lighting and viewing system, characterized in that it comprises a mold element. 10. An eyewear assembly comprising: a frame that can be worn on the head, an eyewear lens supported by the frame in front of the user's eyes, and through the lens, along the viewing optical path. The display illumination and viewing system of claim 1, wherein the display illumination and viewing system is arranged to direct light into an optical path.
An eyewear assembly comprising: 11. The eyewear assembly of claim 10, further comprising a housing supported on a frame mountable on the head, the display, the first lens system, and within the housing. An eyewear assembly comprising: the reflective and transmissive elements supported by the second lens system attached to the eyewear lens. 12. An image display system capable of operating in color and monochrome modes, capable of operating at a constant frame rate consisting of sequential loading of red, green and blue sub-frames. An active matrix liquid crystal display, arranged to cause the active matrix liquid crystal display to emit light,
An illumination source having red, green, and blue light sources; and connecting the illumination source to the illumination source between the color mode for performing color display and the monochrome mode for performing monochrome display. An illumination circuit that includes a switch that operates to switch. 13. The image display system according to claim 12, wherein:
The lighting circuit operates in the color mode to drive the red, green and blue light sources sequentially in synchronization with sequential loading of the red, green and blue sub-frames. Image display system. 14. The image display system according to claim 12, wherein:
An image display system further comprising a backlight controller, wherein the lighting circuit is connected to the backlight controller in the color mode. 15. The image display system according to claim 12, wherein:
The monochrome circuit for simultaneously driving the red, green and blue light sources in synchronization with the sequential loading of the red, green and blue sub-frames by the illumination circuit.
An image display system characterized by operating in a mode. 16. The image display system of claim 12, wherein
An image display system, wherein the lighting circuit operates in the monochrome mode to connect the lighting source to a current source. 17. The image display system of claim 12, wherein
An image display system, wherein the illumination circuit operates in the monochrome mode to simultaneously drive the red, green and blue light sources at 100% utilization. 18. The image display system of claim 12, wherein
An image display system, wherein the illumination circuit operates in the monochrome mode to drive the red, green and blue light sources, respectively, with less than 100% utilization. 19. The image display system of claim 12, wherein
An image display system, wherein the lighting circuit further comprises a multivibrator operative to provide a pulse of controlled duration to limit the emission time of the light source. 20. The image display system according to claim 12, wherein
An image display system, wherein the illumination circuit operates in the monochrome mode to drive the red, green and blue light sources at once. 21. The image display system of claim 12, wherein
To drive a combination of red, green and blue light sources, each with current or duration, each selected to provide a monochrome backlight color,
An image display system operating in the monochrome mode. 22. The image display system of claim 12, wherein
An image display system further comprising a display controller connected to the display. 23. The image display system of claim 22, wherein
An image display system, wherein the lighting circuit is connected to the display controller when in the color mode. 24. The image display system of claim 22, wherein
An image display system, wherein the switch is connected to the display controller to receive a logic signal from the display controller. 25. The image display system of claim 22, wherein
An image display system, wherein the switch is connected to the display controller and the display controller operates to control power consumption of the illumination source. 26. The image display system of claim 12, wherein
Further, a display controller is connected to the display and the lighting circuit, the lighting circuit further comprising an O associated with each of the red, green and blue light sources.
An image display system comprising an R gate, the OR gate operative to receive a logic signal from the display controller and to receive a logic signal from the switch. 27. The image display system of claim 12, wherein
In order for the user to select the color mode or the monochrome mode,
An image display system characterized in that the switch is operable. 28. The image display system of claim 12, wherein
An image display characterized in that the display is a reflective active matrix liquid crystal display or a transmissive active matrix liquid crystal display.
system. 29. An illumination circuit operating with the image display system of claim 12.