JP5254513B2 - Browsing system with display illumination and eyewear assembly having the same - Google Patents

Description

Cross-reference to related applications This application is incorporated by reference in U.S. Provisional Application No. 60 / 140,327, June 21, 1999, 35 S. Insist on the priority of C§112 (e) interests. The entire contents of the above application are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT The development of the present 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)
Small active matrix liquid crystal displays (AMLCD) require an illumination source. In the case of a system using a transmissive AMLCD, the light source is placed after the display. FIG. 1 illustrates a simple prior art method in which a transmissive AMLCD 10 includes a light emitting diode (LEC) backlight 20. Ray 30 from the backlight propagates through the AMLCD and is modulated to form an image. For some types of AMLCDs, color development is performed by sequentially loading red, green and blue subframes into the AMLCD and illuminating the red, green and blue light emitting diodes simultaneously sequentially. Sequential illumination is accomplished by supplying current sequentially through one of the required light emitting diode leads 40. To collimate the light (collimated) beam shaping element 50, such as a Fresnel lens may be used. Other elements such as diffusers or filters can also be used. This type of AMLCD and lighting device is commercially available from Copin Corporation. A viewing system, such as a display, can comprise a simple optical magnifying optical element or a multi-stage image optical system featuring an intermediate image plane located between each stage.

The prior art miniature reflective AMLCD (FIG. 2) uses an illumination system based on a beam splitting cube 70 adjacent to the display 60. The beam splitter can include a polarization splitting coating 71 that serves to linearly polarize the illumination light and also serves as an analyzer for the liquid crystal display. Alternatively, the polarizing beam splitter can be formed from a polymer film. For transmissive AMLCDs , the optical element 50 can be used to collimate, diffuse, or filter illumination.

FIG. 3 shows a more complex prior art reflective AMLCD system that includes a compact and simple magnifying device attached to a lighting system for viewing a magnified image of display 60 (US Pat. No. 5,596,6). 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 for illuminating and viewing images, but the mirror 42 for magnification is not used in the optical path of the illumination system. There is no need for a lens or mirror that affects the 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 lighting devices based on lamps and collimating optics. The collimating optical system provides efficient and even illumination of a reflective display (see, for example, US Pat. No. 6,036,318). This type of collimation system is heavy and large because of the additional lens and optical path required, and is therefore not used in head mounted displays.

Collimated illumination optics are typically used in projection systems that use high brightness lamps and projection lenses as disclosed in US Pat. No. 5,949,503. In certain cases, such as the above US patent, a portion of the projection optics can be used for illumination. In the case of a projection system, this method improves the uniformity of illumination of the projected image and improves the contrast.

SUMMARY OF THE INVENTION The present invention relates to an improved illumination system for a reflective liquid crystal display. The improvement is based on the use of a set of optical elements for the two purposes of merging the illumination system and the magnification system, thereby for image magnification and display illumination. The invention also relates to a system for obtaining a high-intensity monochrome image that can be applied to a reflective or transmissive liquid crystal display.

More particularly, the present invention provides a display illumination and viewing system that includes an illumination optical path and a viewing optical path. In order to form a coincident optical path portion, at least a portion of the illumination optical path is coincident with the viewing optical path. A display comprising an active matrix liquid crystal display is located at one end of the coincident portion of the optical path. The first lens system is located on a 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 light sources such as red, green and blue light emitting diodes are located on the illumination optical path and are offset from the coincident part of the optical path. The illumination light source 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 source in the direction of the display towards the matching portion of the optical path and to direct light from the display along the viewing optical path. , Located at the opposite end of the matching portion of the optical path. In this way, the present invention provides a collimated illumination system for a head mounted reflective AMLCD that is lighter, smaller, and provides even and efficient illumination than prior art systems.

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

A better understanding of the present invention can be obtained when the following detailed description is read with reference to the accompanying drawings, in which:

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a viewing optical system and an illumination optical system that are integrated into a single or multiple stage optical system. The term integration is used for viewing optics and serves to collimate light in the illumination system, thereby reducing the separation and movement of the light used to reduce cost, weight and size. It means the integration of some of the influencing optical elements.

FIG. 4 shows a display system that uses the prior art collimation system of FIG. 2 to provide prior knowledge of the present invention. The lighting system 22 is connected to the browsing system 23 in order to provide an image 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. When the diffuser is used, the illumination from the light emitting diode passes through the diffuser and is collimated by the Fresnel lens 50 to illuminate the AMLCD 60 evenly. The reflected polarized light is directed toward the AMLCD by the beam splitter 71. The AMLCD rotates the polarization of light by an angle at each pixel by an electrical signal representing the image. The light rays pass from the illumination stage 22 through the magnification stage 23 and become an image through the lenses 150 and 160. Any number of optical surfaces can be used to enlarge the image and correct aberrations. To simplify the drawing, the lens surface will be represented by a single lens 150 and 160. In practice, these lenses 150 and 160, respectively, are achromatic double or triple lenses, non-spherical, or more complex combinations of surfaces.

5a and 5b show the main components of the present invention. The reflective AMLCD 60 will be viewed through a lens system with two-stage magnification, represented by lens system 150 and lens system 160. A line-of-sight path is formed from AMLCD to the user's eye through lens system 150 and lens system 160. A characteristic of each lens system is a focal length f. Referring to FIG. 5a, according to Newton's lens equation (N · P = f ₁ · f ₂ ), the lens system 150 forms an intermediate image plane, as shown between 150 and 160, and the image plane described above. Are given by Newton's lens equations well known to those skilled in the art or equivalents thereof. If lens system 160 is located at a distance from the image plane equal to its focal length, the user views the image at an infinite distance. The position of the lens system 160 can be moved to change the distance of the virtual image. As is well known to those skilled in the art, the enlargement ratio of the system is represented by the product of the magnifications of the two stages.

FIGS. 5 a and 5 b illustrate the insertion of reflective and transmissive elements, such as, for example, beam splitter 200, between lens systems 150 and 160. As known to those skilled in the art, a beam splitter can be made by polarization beam splitter, or polymer technology, which can be made by vacuum deposition of multiple layers of thin film (eg, 3M The polarizing beam splitter can be used, or a vacuum-deposited thin metal film (semi-silver mirror) that transmits about 50% can be used. Alternatively, a polarized beam splitting cube can be used. Turning to FIG. 5 b, it can be seen that the purpose of the beam splitter 200 is to reflect light from an illumination source such as the light emitting diode lamp 100. The light emitting diode lamp can be a multiple color lamp with red, green and blue light emitting diodes used in electric field sequential color illumination devices to the optical path. The path between the light emitting diode lamp 100 and the AMLCD 60 forms an illumination path. From the figure, it can be seen that the illumination path matches a part of the browsing path. Light emitting diode, the lens system 150 (in FIG. 5b, the distance indicated by a + b) when it is installed in a position equal to the focal length f ₂ of the lens system 150, 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 a long light source, depending on the viewing requirements of the entire system.

FIG. 6 shows an example of an optical design based on this main member. The lens surfaces 150 and 160 are non-spherical shapes well known to those skilled in the art, and are represented by the following equations.

[Expression 1]

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

[Table 1]

[Table 2]

[Table 3]

In the case of these designs, a separate lens for collimating the light from the light emitting diode is not required, and thus the weight can be reduced. Although FIG. 4 will be described, it can be seen from this figure that the collimating lens 50 (of FIG. 4) can be omitted, and the distance related to the focal length is shortened, resulting in a smaller 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 the magnifying lens system 150 is located near the eyepiece 210. The display 60 is illuminated by the illumination light source 100. The lens system 150 projects onto the image plane at the input pupil of the optical system within the lens 210. The lens 210 cooperates with the magnifying internal optical relay formed by the lens 220, the polarizing beam splitter 240, the quarter wave plate 260 and the concave mirror 250 in front of the lens 210 at a distance that is easily visible to the user's eyes. Supply images that can be seen in

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, because the light emitting diode is the usual light source in these displays. Many other illumination sources can also be used, including lasers, optical fibers that send light from remote image sources, or other lamps.

The use of sequential red, green and blue illumination with an eyepiece system of the type of FIG. 7 results in excellent color images. However, the use of sequential illumination of light emitting diodes reduces the utilization of light emitting diodes, thereby reducing the total amount of light supplied to the eye. In the case of a system of the type of FIG. 7 that is used as a beam splitter 240 and a coupling device for fusing the surrounding landscape and the light from the display, the viewer is as if the ambient sunlight is bright. Sometimes very bright images are required.

For many applications, such as the above (mounting on the eye) eyewear display is a color display for certain image, and bright ambient does not require color in view of the other in the light A high brightness display for images is required. In order to make the sequential color display very bright, the present invention also implements a high-intensity monochrome mode that includes powering the red, green and blue light-emitting diodes at 100% utilization at the same time Including a method for

In the embodiment of the invention of FIG. 8, the light emitting diodes 301, 302, 303 are turned on continuously, but in that case the frame rate of the AMLCD using the switch 300 is not changed at all. When all three light emitting diodes emit light continuously and simultaneously, a black and white image portrait is formed, in which white is more than any of the colors emitted by the red, green and blue sequential light emitting diodes. Is also bright.

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 a sequential color drive circuit in the backlight controller. When set to another position, the light emitting diode is connected to a 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 also be used to supply current to the light emitting diode. 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 technique can also be applied to a transmissive AMLCD (FIG. 1) or a reflective AMLCD illumination device (FIG. 2).

FIG. 9 shows another embodiment. Switch 350 is used to provide a logical input to display controller 330 to control the light emitting diodes. Display controller 330 provides illumination signals to the light emitting diodes through OR gates 304, 305 and 306 along path 319. The logic output from the OR gate is supplied to the gates of the control transistors 307, 308, and 309. The transistor allows current to flow through the light emitting diode according to the logic signal sent to path 319. The switch 350 is used to select an operation 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 to the center position, the OR gate inputs 321, 322 and 323 are held at the V _DD potential, which means that the OR gate output is held high, resulting in a path Whatever the signal on 319 means that the light emitting diode emits continuously. When switch 350 is set to the rightmost position, lines 321, 322, and 323 are separate logic paths (not shown) from logic within the display controller or from other control circuits. Is held at the numerical value established by

The third embodiment (FIG. 10) includes a switch 310 that provides a logic signal path 320 to the AMLCD display controller. The logic signal on line 320 means the user selects a high-intensity monochrome mode. This signal allows the controller logic to use for the purpose of optimizing the balance of red, green and blue information that reduces power consumption in the memory and elsewhere and forms a monochrome image therefrom. Adjust.

Another embodiment of the invention comprises circuitry that allows the microprocessor to select a background color. Normally, by operating 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 of 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, the back to display an alarm in black and red The color of the light can be switched to, for example, red. This switching can be performed by supplying power only to the red light emitting diode.

It should be noted that the light emitting diode need not be continuously lit in monochrome mode and need not be operated at full utilization in color mode. The above logic devices can be used to reduce utilization in order to reduce brightness in monochrome or color mode. FIG. 11 shows a method for performing the brightness control. A signal for emitting one of the light emitting diodes is transmitted from the display controller 330. A pulse is simultaneously supplied to the monostable multivibrator 400 by the path 451. For example, a signal for causing the light emitting diode 303 to emit light is sent from the display controller 330 to the AND gate 403 through the OR gate 306. The AND gate passes only the illumination signal only while the pulse 420 is present. This pulse 420 is started by the multivibrator 400 when a start pulse is received from the 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 usage rate of the light emitting diode, that is, the luminance is controlled by the width of the pulse from the multivibrator 400. FIG. 11 shows how the signal from the AND gate is sent through a series resistor 413 that controls the current flowing through a set of matching field effect transistors 460. Note that the pulse width t can be supplied by a display controller or can be controlled by a logic signal that can be supplied by a monostable multivibrator through an additional logic path (not shown). .

The lighting circuits of FIGS. 8-11 can be implemented with 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 present invention is not limited to the figures and the description described above, but only by the appended claims.
[Brief description of the 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 an illumination system comprising a prior art reflective active matrix liquid crystal display magnification device.
FIG. 4 is a display system incorporating a viewing system with a lighting system.
FIG. 5a is a schematic illustration of the optical components of the display system of the present invention.
FIG. 5b is a schematic diagram of the optical components of the display system of the present invention.
FIG. 6 is a schematic illustration of the optical design of the display system of FIGS. 5a and 5b.
FIG. 7 is a schematic illustration 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 circuit of another embodiment of the lighting control system of the present invention.
FIG. 10 is a block diagram and circuit of yet another embodiment of the lighting control system of the present invention.
FIG. 11 is a block diagram and circuit of yet another embodiment of the lighting control system of the present invention.

Claims (26)

A viewing system with display illumination for viewing images on a display,
An illumination optical path and a viewing optical path 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 matching path portion;
A display comprising an active matrix liquid crystal display located at one end of the matching path portion;
A first lens system located on the coincidence path portion, having a first focal length and providing an image plane on the viewing optical path;
A second lens system located on the viewing optical path;
Located on the illumination optical path, offset laterally from the optical path of the coincident path portion, and from the first lens system by the same distance as the first focal length of the first lens system. A distant illumination source,
Opposite ends of the coincidence path portion for directing light from the illumination light source onto the coincidence path portion, in the direction of the display, and for transmitting light from the display along the viewing optical path With a beam splitter located at
The coincident path portion is an optical path portion extending between the display and the beam splitter;
The display is an image display system capable of operating in color mode and monochrome mode,
An active matrix liquid crystal display capable of operating at a constant frame rate consisting of sequential loading of red, green and blue subframes;
The illumination light source comprising red, green and blue light sources arranged to emit light from the active matrix liquid crystal display;
A color mode for performing color display and a monochrome mode for performing monochrome display by controlling a current balance between the red, green and blue light sources connected to the illumination light source; An illumination circuit including a switch that operates to switch the illumination light source between,
Equipped with a,
The viewing system with display illumination , wherein the illumination optical path in the color mode and the illumination optical path in the monochrome mode are the same .   2. The browsing system with display illumination according to claim 1, wherein the illumination light source includes red, green and blue light emitting diodes.   The viewing system with display illumination according to claim 1, wherein the illumination light source includes red, green, and blue laser diodes.   The viewing system with display illumination according to claim 1, further comprising another optical element on the illumination optical path.   5. The browsing system with display illumination according to claim 4, wherein the another optical element includes a diffusion device.   The viewing system with display illumination according to claim 1, wherein the beam splitter includes a polarization beam splitter.   The viewing system with display illumination according to claim 1, wherein the beam splitter comprises a plurality of thin film-like layers, or a thin film-like metal layer, a semi-silver mirror, or a beam-splitting cube. Browsing system with display lighting.   The viewing system with display illumination according to claim 1, further comprising a housing, wherein the display, the first lens system, the illumination light source, and the beam splitter are supported in the housing. Browsing system with display lighting. An eyewear assembly,
A frame that can be worn on the head;
An eyewear lens supported by the frame in front of the user's eyes;
The viewing illuminated viewing system of claim 1, wherein the viewing illuminated viewing system is arranged to send light in an optical path through the eyewear lens along the browsing optical path;
An eyewear assembly comprising: 10. The eyewear assembly of claim 9, further comprising a housing supported on a frame that can be attached to the head, wherein the display, the first lens system, and the beam splitter are the housing. Is supported within,
An eyewear assembly, wherein the second lens system is attached to the eyewear lens.   2. A viewing system with display illumination according to claim 1, wherein the lighting circuit drives the red, green and blue light sources sequentially in synchronism with the sequential loading of the red, green and blue subframes. A browsing system with display illumination, which operates in the color mode.   12. The browsing system with display illumination according to claim 11, further comprising a backlight controller, wherein in the color mode, the lighting circuit is connected to the backlight controller. system.   12. A viewing system with display illumination according to claim 11, wherein the lighting circuit drives the red, green and blue light sources simultaneously in synchronism with sequential loading of the red, green and blue subframes. A browsing system with display illumination, which operates in the monochrome mode.   12. The viewing system with display illumination according to claim 11, wherein the illumination circuit operates in the monochrome mode to connect the illumination source to a current source.   12. The viewing system with display illumination according to claim 11, wherein the illumination circuit operates in the monochrome mode to simultaneously drive the red, green and blue light sources at 100% utilization. Browsing system with display lighting.   12. The viewing system with display illumination according to claim 11, wherein the illumination circuit operates in the monochrome mode to drive the red, green and blue light sources respectively at a utilization rate of less than 100%. Browsing system with display lighting.   12. A viewing system with display illumination according to claim 11, wherein the lighting circuit further includes a multivibrator that operates to provide a pulse of controlled duration to limit the light emission time of the light source. A viewing system with display illumination.   12. A viewing system with display illumination according to claim 11, wherein the illumination circuit operates in the monochrome mode to drive the red, green and blue light sources at once. .   12. A display illuminated viewing system according to claim 11, each driving a combination of red, green and blue light sources, each having a current or duration, selected to provide a monochrome backlight color. Therefore, a browsing system with display illumination, which operates in the monochrome mode.   12. The browsing system with display illumination according to claim 11, further comprising a display controller connected to the display.   21. The browsing system with display illumination according to claim 20, wherein in the color mode, the lighting circuit is connected to the display controller.   21. A viewing system with display illumination according to claim 20, wherein the switch is connected to the display controller to receive a logic signal from the display controller.   21. A viewing system with display illumination according to claim 20, wherein the switch is connected to the display controller and the display controller is operative to control power consumption of the illumination source. With browsing system.   12. The viewing system with display illumination of claim 11, further comprising a display controller connected to the display and the illumination circuit, the illumination circuit further comprising an OR associated with each of the red, green and blue light sources. A viewing system with display illumination, comprising: a gate, wherein the OR gate is operable to receive a logic signal from the display controller and to receive a logic signal from the switch.   12. The browsing system with display illumination according to claim 11, wherein a user can operate the switch to select the color mode or the monochrome mode. 12. The browsing system with display illumination according to claim 11, wherein the display is a reflective active matrix liquid crystal display or a transmissive active matrix liquid crystal display.

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