WO2002086597A1

WO2002086597A1 - Color display contrast enhancing apparatus

Info

Publication number: WO2002086597A1
Application number: PCT/US2002/006608
Authority: WO
Inventors: Warren Smith
Original assignee: Warren Smith
Priority date: 2001-03-05
Filing date: 2002-03-05
Publication date: 2002-10-31
Also published as: WO2002071384A1

Abstract

A head-mounted contrast enhancing apparatus (10) enhances perceived signal contrast of a color display (12). The head-mounted color display contrast enhancing apparatus (10) comprises one or more color filters mounted on a structure, such as eyeglass lenses (20) mounted in eyeglass frames (32). The color filter has a frequency selectivity characteristic that produces more attenuation at some color frequencies not emitted by the color display than at the color frequencies emitted by the color display. The color filters are placed in close enough proximity to the eye (14) of the viewer of the color display such that most of the ambient (or non-emitted) light directed at the eye(s) (14) of the viewer is filtered by the color filter before striking the eyes of the viewer.

Description

COLOR DISPLAY CONTRAST ENHANCING APPARATUS

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of co-pending provisional application Serial No. 60/273,525 filed on March 5, 2001, which is fully incorporated herein by reference.

TECHNICAL FIELD [0002] The present invention relates to color images and color filters, and more particularly, relates to a head- mounted color display contrast enhancement apparatus .

BACKGROUND INFORMATION

[0003] Flat-panel display and CRT performance in high ambient light environments has heretofore frequently proved unsatisfactory. The reason is that much of the direct or diffused sunlight or other ambient light incident on a color CRT or color LCD display is reflected from the screen. If the strength of the reflected light is near to or greater than the light emitted from the back light through the active pixels or emitted from the activated phosphors in the CRT, the information being displayed on the display is washed out, making the image difficult to view. Furthermore, in high ambient light environments, the pupils of the viewer are contracted, reducing the amount of emitted light that strikes the retina of the viewer.

[0004] Laptop computers, for example, are virtually unusable in bright environments (such as outside, sitting by a swimming pool, sitting next to a window with direct sunshine on an airplane or a bus, etc.), greatly decreasing the utility provided by the mobility of the laptop computer. Furthermore, while people want more natural light in their work environments, the amount of natural light provided often must be limited to prevent interference with the readability of present flat panel or CRT computer displays. Projection television and projected movies also require dark rooms to prevent the image from being washed out .

[0005] Some previous attempts to deal with this problem have involved the use of viewing hoods to shade the CRT screen or the use of neutral density filters (i.e., filters providing a predetermined and substantially constant attenuation versus frequency) on the tube faceplate exterior. Another partial solution is provided by the black matrix CRT, which uses a black or ligh -absorbing material on the interior screen around the light-emitting phosphors and thereby absorbs a great deal of the light that would otherwise be reflected back to a viewer. Still another technique is to pigment the phosphors so as to reduce their reflectivity. Also, add-on exterior filters, which are somewhat transparent to two colors only, have been applied with penetration type CRT's. In such applications, the add-on exterior filters have provided only limited enhancement in contrast and have not permitted reproduction of a wide variety of colors.

[0006] Also, there have been attempts to increase total luminosity of the screens and to increase the contrast when viewed in daylight. However, in applications where the total illumination is limited by power considerations

(e.g., laptop computers designed to run on battery power), contrast has been especially problematic. Heretofore the goal of a daylight-readable flat panel display for laptop computer use in environments such as a poolside in sunny weather has been elusive.

[0007] U.S. Patent No. 4,245,242 discloses a contrast enhanced color display apparatus capable of providing a wide variety of colors. This apparatus comprises a display for emitting at least three colors and a color filter disposed between the display and a viewer. The color filter has a frequency selectivity characteristic that produces more attenuation at some non-emitted color frequencies than at other emitted color frequencies . The device disclosed in U.S. Patent No. 4,245,242 was shown experimentally to increase the color contrast of CRT displays by attenuating both the incident and the reflected ambient light, while not attenuating the red, blue, and green colors from the CRT as much, thereby increasing the signal-to-noise ratio.

[0008] U.S. Patent No. 4,245,242, however, specifically discloses that the color filter is in proximity with the screen that is emitting the colored light. This takes advantage of the fact that ambient light must pass through the color filter both on the way to the screen and on the way back from the screen after refection, thereby providing double filtration as the ambient light passes through the light filter twice while the emitted light passes through the light filter only once. Thus, U.S. Patent No. 4,245,242 discloses a filter used only for applications such as panel displays and CRTs but not for other types of displays such as projected images, where the filter, of necessity, must be in proximity to the display unit . [0009] One problem is that nearly all attempts to increase display contrast have focused on modifying the display unit itself, by increasing the luminosity and/or decreasing the reflectance of ambient light at the display device itself using, for example, antireflective coatings. However, the dust, oils, and other contamination on the surface of any antireflective coatings readily reflect ambient light, greatly reducing the effects of the coatings. Even given these screen-based attempts at producing higher contrast levels, light from sources other than the screen viewed (i.e., light from the rest of the viewing environment that is not reflected from the screen but still strikes the eye of the viewer via peripheral vision) also strikes the eyes of the viewer. This causes glare and causes the iris in the viewer's eye to contract, thereby reducing the viewer's ability to see the screen. [0010] While U.S. Patent No. 4,245,242 discloses interposing color filters between a CRT and the viewer, these color filters are explicitly in proximity with the CRT, and thus have no effect on the particular problems described above. The display disclosed in U.S. Patent No. 4,245,242 is still difficult to view outside on a sunny day. In this environment, the viewer is likely to be wearing sunglasses, which further attenuate the signal from the display and reduce total luminosity. Furthermore, positioning the color filters in proximity with the display device does not allow for enhancement in contrast in other types of displays, for example, projected images. [0011] Accordingly, there is a need to increase the utility of laptop computers and solve problems with image viewability in CRTs, flat panel displays, projected movies, and the like, by providing a contrast enhancement apparatus making it substantially easier to view these images in environments with more ambient light than has been possible heretofore.

SUMMARY OF THE INVENTION [0012] In accordance with one aspect of the present invention, a head-mounted color display contrast enhancing apparatus is provided for enhancing perceived signal contrast of a color display. The head-mounted color display contrast enhancing apparatus comprises one or more color filters mounted on a structure. The structure preferably places the color filters in close enough proximity to the eye(s) of the viewer of the color display such that most of the ambient light that would otherwise strike the eye(s) of the viewer is filtered through the color filter before striking the eye(s) of the viewer. The color filter has a frequency selectivity characteristic that produces more attenuation at some non-emitted color frequencies than at the emitted color frequencies . [0013] The color filter preferably provides a frequency selectivity characteristic wherein (i) at least some light frequencies less than a first color frequency CR are more greatly attenuated than light at the first color frequency CR, (ii) at least some light frequencies between the first color frequency CR and a second color frequency CG are more greatly attenuated than light at the first color frequency CR or the second color frequency CG, (iii) at least some light frequencies between the second color frequency CG and a third color frequency CB are more greatly attenuated than light at the second color frequency CR or the third color frequency CG, and (iv) at least some light frequencies more than the third color frequency CB are more greatly attenuated than light at the third color frequency CB. One embodiment of the color filter includes a tricolor bandpass filter. Alternatively, the head-mounted color display contrast enhancing apparatus includes a clear medium printed with cyclic patterns of the same three dyes used in the color filtration of the pixels in the display. The term frequency, as used herein, includes a frequency band near to the nominal frequency, not just a single specific frequency.

[0014] One embodiment of the head-mounted color display contrast enhancing apparatus is in the form of a set of eyeglasses where the color filter is in the form of eyeglass lenses and the structure is one of eyeglass frames holding the color filter in proximity to the viewer's eyes. Other embodiments of the head-mounted color display contrast enhancing apparatus include contact lenses and a helmet with a visor.

[0015] According to another aspect of the present invention, an enhanced-contrast color display system is provided comprising a color display and the head-mounted color display contrast enhancing apparatus. The color display emits at least a visible light of a first color frequency CR, which is selected to stimulate the red color pigment cones in human eyes, emits at least a visible light of a second color frequency CG, which is selected to stimulate the green color pigment cones in human eyes, and emits at least a visible light of a third color frequency CB, which is selected to stimulate the blue color pigment cones in human eyes . The color display is preferably designed to be viewed either directly or by reflection or refraction, either directly or through other optical elements .

[0016] One embodiment of the display comprises a color cathode ray tube having red light-emitting phosphors, green light-emitting phosphors, and blue light-emitting phosphors, producing light at the color frequencies CR, CG, and CB respectively, or near enough thereto that the light thus produced is relatively less attenuated by the color filter than is the ambient light.

[0017] Another embodiment of the display comprises a flat panel display having red, blue, and green picture elements producing light at the color frequencies CR, CG, and CB respectively, or near enough thereto that the light thus produced is relatively less attenuated by the color filter than is the ambient light.

[0018] A further embodiment of the display comprises light containing at least the color frequencies CR, CB, and CG passing through a film. The film includes colored pigments dispersed therein to selectively allow varying degrees of passage of light in mixtures of predominantly the frequencies CR, CB, and CG. The colored pigments are patterned to form an image .

[0019] A further embodiment of the display comprises a light source producing multiple frequencies of light. The light from the light sources passes through a film including colored pigments dispersed therein to selectively allow varying degrees of passage of light in mixtures of predominantly the frequencies CR, CB, and CG, wherein the colored pigments are patterned to form an image . [0020] Yet another embodiment of the display comprises a light source producing predominantly light at the frequencies CR, CB and CG. The light from the light source passes through a film including colored pigments dispersed therein to selectively allow varying degrees of passage of combinations of red, blue, or green light, wherein the colored pigments are patterned to form an image . The display can also include at least one optics system wherein the emitted light is projected and diffracted from a viewing surface.

[0021] According to another aspect of the present invention, a method is provided for enhancing the contrast of a color display. The method comprises positioning a color filter in proximity to at least one eye of a viewer and between the viewer and the color display, and causing light to be emitted by the display at predetermined emitted color frequencies, wherein the light forms an image. The image is viewed and the color filter provides more attenuation at some non-emitted color frequencies than at the emitted color frequencies .

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] These and other features and advantages of the present invention will be better understood by reading the following detailed description, taken together with the drawings wherein:

[0023] FIG. 1 is a schematic diagram of an enhanced- contrast color display system, according to the present invention;

[0024] FIG. 2 is a perspective view of a head mounted color display contrast enhancement apparatus, according to one embodiment of the present invention; [0025] FIG. 3 is a schematic view of a color display contrast enhancement apparatus having color filters, according to an alternative embodiment of the present invention;

[0026] FIG. 4 is a graphical illustration of the relative frequency response of the human eye;

[0027] FIG. 5 is a graphical illustration of a signal output from a computer display relative to the retinal response;

[0028] FIG. 6 is a graphical illustration of the stimulation of cones in the human eye without using a contrast enhancement apparatus according to the present invention; and

[0029] FIG. 7 is a graphical illustration of the stimulation of cones in the human eye with a contrast enhancement apparatus according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0030] A head-mounted color display contrast enhancement apparatus 10, FIG. 1, according to the present invention, enhances the contrast of a multicolor display 12, such as a cathode ray tube (CRT) display, back-lit flat panel display, reflective panel display, or projected image display (e.g., movies or slides). The display 12 is generally a tricolor display with frequencies (CR, CG, CB) of red light 16a, blue light 16b, and green light 16c, which are selected to stimulate the red, green and blue color pigments cones in human eyes. A CRT has red light- emitting phosphors, green light-emitting phosphors, and blue light-emitting phosphors producing light at the color frequencies CR, CG, and CB, respectively. A flat panel display has red, blue, and green picture elements producing light at the color frequencies CR, CG, and CB respectively. A projected image display projects light containing the color frequencies CR, CB, and CG.

[0031] The head-mounted color display contrast enhancement apparatus 10 is preferably positioned proximate the eyes 14 of a viewer and selectively attenuates ambient light 18 while allowing light 16a-c from the display 12 to pass to the eye 14 of the viewer with relatively little attenuation. The head-mounted color display contrast enhancement apparatus 10 thus increases the signal-to-noise ratio between the signal (the emitted light 16a-c) and the noise (the ambient light 18), i.e., substantially filters out light 18 not emitted from the display 12 while allowing light 16a-c emitted from the display 12 to be viewed by the viewer.

[0032] According to a preferred embodiment, the head- mounted color display contrast enhancement apparatus 10 includes color filters 20, which attenuate all ambient light 18 of the frequency bands not produced by the display 12 (i.e., the non-emitted color frequencies) while substantially not attenuating the light 16a-c of the frequency bands emitted from the display 12 (i.e., the emitted color frequencies) . Positioning the color filters 20 proximate the eyes 14 of the viewer provides a number of advantages over filters positioned on the screen of the display 12. Because of the proximity to the eyes 14 of the viewer, the viewer side 22 of the color filters 20 is substantially shielded from ambient light 18. This natural shading on the viewer side 22 of the color filters 20 prevents scattering and reflections of ambient light 18 (e.g., from dust, oil, etc.) on the viewer side 22 of the color filters 20. The total amount of ambient light 18 striking the viewer's eyes 14 from areas in the work environment aside from the display 12 being viewed is reduced, allowing the viewer's pupils to dilate. Dilating the pupils increases the amount of the desired image light 16a-c that strikes the retina of the viewer's eyes 14, thereby increasing the total perceived luminosity of the display 12 and the perceived "brightness" of the display 12, making the images thereon easier to see. [0033] One embodiment of the head-mounted color display contrast enhancement apparatus 10, FIG. 2, is a pair of eyeglasses or sunglasses 30. Eyeglass lenses are created from the color filters 20 and are mounted in standard eyeglass frames 32, using known methods, to form eyeglasses or sunglasses 30. This embodiment is particularly suited for using the display 12 outdoors in bright ambient light (e.g., poolside on a sunny day), where the viewer is likely to be wearing some type of eyewear such as sunglasses . By combining the color filters 20 into the pair of sunglasses 30, the present invention allows a stronger signal to reach the eyes 14 of the viewer.

[0034] Another embodiment includes goggle lenses created out of the color filter material and mounted in the form of goggles. Yet another embodiment includes the color filter material mounted in the faceplate of a helmet, such as the helmets worn by military pilots. Yet another embodiment includes the color filter material in a set of contact lenses to be disposed in contact with the eyes 14 of the viewer. Any other structure capable of holding the color filters 20 proximate the eyes 14 of the viewer is also contemplated. [0035] According to one preferred embodiment, the color- filters 20 used in the present invention are triple bandpass color filters designed to allow the light 16a-c having the color frequencies CR, CG, and CB to pass through while substantially attenuating the ambient light 18. Examples of triple bandpass color filters are disclosed in U.S. Patent Nos . 4,245,242; 4,663,562; 5,754,262; and 5,646,781, incorporated herein by reference. The color filters 20 can be manufactured according to the methods disclosed in the patents referenced above. Although the above patents disclose specific types of color filters, any type of color filter can be used in the present invention insofar as it provides the color frequency characteristics described above and can be disposed in proximity to the eye of the viewer.

[0036] According to an alternative embodiment, the present invention includes another means for attenuating the ambient light without using conventional color filters. For example, the contrast enhancing apparatus 10, FIG. 3, can be printed on a clear medium with patterns 40a-c (e.g., stripes) of similar frequency attenuation characteristics as the three dyes used in the color filtration of the pixels in the display 12. The patterns 40a-c can be cyclic patterns or random patterns of the three colors . The medium 42 on which the patterns 40a-c are printed is held by a structure (e.g., eyeglass frames 32) substantially outside of the focal plane 44 of the eyes 14 as the eyes 14 view the display 12. The width of the patterns 40a-c is preferably wide enough so that there is essentially no diffraction effect by the patterns 40a-c, but thin enough that the presence of multiple colored patterns 40a~c is unnoticeable to the eye when it is focused on the image being viewed. The results of simulations (described below) indicate that even such rudimentary color filters could have a substantial impact on increased ease of viewing color displays 12.

[0037] This invention is based on an understanding of the principles of human color vision perception. The human eye is equipped with color-insensitive rod cells (which can only see in black and white) and color sensitive cone cells of three varieties, red cone cells (that are more sensitive to red light, and optimally sensitive to light with a wavelength of about 564 nm) , green cone cells (that are more sensitive to green light, and optimally sensitive to light with a wavelength of about 534 nm) , and blue cone cells (that are more sensitive to blue light, and optimally sensitive to light with a wavelength of about 420 nm) . FIG.4 shows a graph showing the frequency response of the individual cones in the human eye .

[0038] The human brain perceives color by the relative degree of stimulation of these types of cone cells. For example, if all three types of cone cells are simultaneously and equally stimulated, the human brain sees the color as "white." Manufacturers of displays use this principle to synthesize all apparent visible colors by producing three separate color signals in the vicinity of about 420 nm for blue, about 534 nm for green, and about 564 nm for red. Because human perception of the whole spectrum of perceivable colors results from the relative levels of stimulation of these individual cone types, stimulation of the cones by these frequencies in varying combinations can reproduce the entire human color experience using only three discrete color frequencies (although in nature color is a complicated mixture of continuous frequencies of light) .

[0039] Because color perception is the result of the relative level of stimulation of the respective sets of cone cells in the retina of the viewer, it is easy to model human color vision mathematically. The total level of stimulation of any of the sets of cone cells for any colors can be described mathematically as follows:

Stimulation=Integral_(λ__{0 to infinlty)} (L(λ) *FR(λ) ) dλ here λ is wavelength, L(λ) is the luminosity at a given wavelength, and FR(λ) is the frequency response of the cone cell at that frequency

[0040] he reason why images from displays (such as R s, flat panel displays, movies, and even so called daytime viewa le reflective displays) are washed out in daylight is that the am ient light in outdoor situations is essentially evenly distri uted across the frequency spectrum (although it varies somewhat depending on the frequencies of light reflected from surroundings) he light emitted from a display (e g , a flat panel display) , on the other hand, is at a com ination of particular frequency ands, as descri ed a ove ven if the light from the display in a particular frequency and is considera ly righter than the am ient light in that particular frequency and, the human eye integrates the stimulation from light over all frequencies, su stantially overwhelming the light from the display y selectively filtering out the frequencies of light that are not produced y the display (while not filtering out the frequencies of light produced y the display) , the total stimulation due to ambient light can be reduced significantly while substantially not reducing the stimulation due to the light from the display. Thus, the signal-to-noise ratio of the human perception of the light impinging on the retinas of the viewer is substantially increased, making the display device considerably easier to read. This is shown in FIG. 5, which looks at the perceived contrast of "white" light from a display in an environment with moderate ambient light .

[0041] Given this signal and this degree of ambient light, the stimulation of the human cone cells in all three colors (obtained through integrating the formula above) is given in FIG. 6 for the case when "white light" is produced by the display device and the case when it is not (i.e., the case where the display device is displaying darkness) . [0042] FIG. 6 is the result of simulation modeling of a typical existing flat panel display, looking at total retinal stimulation from the screen of FIG. 5 given a "white" display versus a "black" display. The values in the charts are derived using numerical analysis based on the curves shown in FIG. 5.

[0043] The signal-to-noise ratio obtained without the use of the contrast enhancing apparatus of this invention can be calculated from the simulation results above as the total stimulation to the cones with a white signal (signal plus noise) , less the total stimulation to the cones when black (noise) , divided by the total stimulation to the cones with a black signal (noise alone) . This results in (1247.6-757.5)

as the signal-to-noise ratio. Note that this is the signal-to-noise ratio that is obtained when we assume that the display is 5 times brighter than the sum of the reflected ambient light and light leakage from the screen at the particular colors produced by the screen.

[0044] When the contrast enhancement apparatus is used, however, the results are dramatically different, as is shown in FIG. 7. The signal-to-noise ratio when the contrast enhancement apparatus is used, when calculated by the same method as described above, is found to be 1.29, indicating that the signal-to-noise ratio has been improved by a factor of 1.99, nearly doubled.

[0045] The assumptions used in the simulations above should be noted. While simulations for all types of media described in this specification (i.e., projected images, television screens, LCDs, computer monitors, etc.) obtain very similar results, the specific case modeled above is one that assumes the state-of-the-art "daylight readable" LCD screen as described in U.S. Patent No. 5,754,262. The relative intensities assumed between the screen output and the ambient light (5:1) and the frequency-dependant filtering performance of the triple bandpass filter assumed in these simulations are the same as in U.S. Patent No. 5,754,262. The use of this contrast enhancement device provides an about doubled signal-to-noise ratio even when used with other so-called high-contrast display equipment.

[0046] It was found in the simulations that the ratio with which the contrast (signal-to-noise ratio) was improved was virtually independent of the initial contrast level of the display system (i.e., using this same triple bandpass filter material in a head-mounted contrast enhancement apparatus will double the contrast regardless of how excellent or poor the initial contrast was) , and thus similar effects can be expected for projected movies, CRTs, LCDs, etc., insofar as the red, green, and blue frequencies used in the triple bandpass filter substantially match the frequencies of the light emitted by display device.

[0047] The color display contrast enhancement apparatus of the present invention is described further in the context of the following prophetic examples. Color Display Contrast Enhancement Example 1

[0049] A user of a laptop computer sits in a bright poolside environment wearing a pair of sunglasses made according to the present invention, which comprise notch pass filters for 420±5 nm, 534+5 nm, and 564+5 nm passing 80% of the light energy in these bands while attenuating 80% of visible light outside of these bands. The color- filter lenses in this example can be produced using a known technique, such as the dispersion of inorganic metal oxide particles in the filter medium, as disclosed in U.S. Patent No. 6,093,349, incorporated herein by reference, and then mounted in glasses frames as are commonly known. The display on the computer has pixels that produce red light at 564+5 nm, green light at 534+5 nm, and blue light at 420+5 nm. The lenses of the glasses of this example are close enough to the user's face that virtually all ambient light is prevented by the user's head from striking the back side of the glasses.

[0050] Given the description above, the total intensity of the signal is reduced by 20%, while the total intensity of the noise integrated over the shape of the curve is reduced by slightly under 80%. Simulations indicate that the S/N (signal-to-noise) ratio is increased by a factor of 2.88. The reason why the S/N ratio is not improved by the factor of 4, which one might expect from a simple ratio of the transmission characteristics of the lenses, is that ambient light also contains some light at the exact frequencies as used in the filters . Color Display Contrast Enhancement Example 2

[0051] A combat pilot viewing a CRT display sits in a bright cockpit environment wearing a pair of goggles made according to the present invention, which comprise notch pass filters for 418+2 nm, 532+2 nm, and 566+2 nm passing 90% of the light energy in these bands while attenuating 90% of visible light outside of these bands. The color- filter lenses according to this example can be produced using a known technique, such as disclosed in U.S. Patent No. 4,521,524, and then mounted in the goggle frames as are commonly known. The display on the CRT has pixels that produce red light at 566+2 nm, green light at 532+2 nm, and blue light at 418±2 nm. The total intensity of the signal is reduced by 10%, while the total intensity of the noise integrated over the shape of the curve is reduced by slightly under 90%, meaning that the S/N ratio is increased by nearly a factor of 4.42 (as indicated by the simulations) . This allows the pilot to read the instruments with ease and to operate the airplane more easily even in a situation where the pilot might need to look into bright light to visually identify a target, then change focus to a display device within the cockpit, and then change focus to the bright outdoors again. Color Display Contrast Enhancement Example 3

[0052] A film is to be shown in a high school, but the auditorium windows cannot be closed or covered because they must be left open on a hot summer day. While the pigments used in the film allow a broad frequency range of light to pass through, increasing the amount of light energy used to project the image so that it is viewable easily would force the film to absorb enough energy to damage the film. Instead a projector with a light source that only subjects the film to light at 422+2 nm for blue, 430+2 nm for green, and 545+2 nm for red is used, and the audience members use the glasses described in Example 3, passing selectively those particular wavelengths, to view the movie with ease even though the total power dissipated by the film itself is substantially reduced and even though the room is quite bright. Another audience member obtains the same effects through the use of contact lenses having the same frequency response as described above .

Color Display Contrast Enhancement Example 4 [0053] A player of a hand-held low-power game machine has problems reading the reflective (non-lit) screen in the bright daylight because of glare and reflections from the display (due, in large part, to oil and dirt on the display) . The glasses of the present invention, which in this case pass the primary colors reflected from the display, increase the contrast of the game machine by filtering out the glare and other ambient light scattered from the surface of the game machine .

[0054] The head-mounted color display contrast enhancement apparatus of the present invention can also be combined with other contrast-enhancing techniques such as the use of antireflective coatings on optical elements in the system, increased power to the light-emission systems, and the like, without violating the scope or intent of the present invention. Furthermore, the method used to produce the multi-notch band pass filter in the present invention can be any method, and the multi-notch band pass filter can be of any composition, insofar as it fulfils the optical characteristics described above.

[0055] Accordingly, the contrast enhancement apparatus of the present invention makes it substantially easier to read displays, such as CRTs, flat panel displays, projected images, and the like, in high levels of ambient light producing benefits for military applications, business applications, and entertainment applications. While making the displays more readable and more pleasing to the viewer, this invention also reduces eyestrain, allowing workers who use display devices such as computers to work longer and produce more. It also allows increased portability of work, allowing laptop computer owners to use their laptop computers in environments where they could not be used before (such as on busses in bright sunshine, in parks in direct sunlight, by the pool, at the beach, etc.), greatly enhancing the value and usability of laptop computers. It also allows the total brightness of the display device to be reduced while still allowing the display to be viewed with ease . This also reduces power consumption in laptop computers, extends battery life, allows the computers to be used longer without connection to external power sources or, conversely, allows cheaper and/or smaller batteries to be used in the laptop computer, increasing the economy and/or the portability of the device. The contrast enhancement apparatus also allows for easier viewing of movies and other projected images.

[0056] Modifications and substitutions by one having ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims .

Claims

CLAIMS The invention claimed is:

1. A head-mounted color display contrast enhancing apparatus, for use proximate at least one eye of a viewer to enhance perceived signal contrast of a color display, wherein said color display emits light at predetermined emitted color frequencies, said apparatus comprising: a head mounting structure; at least one color filter mounted on said structure, wherein said at least one color filter has a frequency selectivity characteristic that produces more attenuation at non-emitted color frequencies than at emitted color frequencies; and wherein said mounting structure mounts said at least one color filter in close enough proximity to the eye of the viewer such that most ambient light that would otherwise strike the eye of the viewer is filtered by said color filter before striking the eye of the viewer.

2. The head-mounted color display contrast enhancing apparatus of claim 1 wherein said at least one color filter comprises means for more greatly attenuating at least some light frequencies less than a first color frequency CR than light at the first color frequency CR, more greatly attenuating at least some light frequencies between the first color frequency CR and a second color frequency CG than light at the first color frequency CR or the second color frequency CG, more greatly attenuating at least some light frequencies between the second color frequency CG and a third color frequency CB than light at the second color frequency CR or the third color frequency CG, and more greatly attenuating at least some light frequencies more than the third color frequency CB than light at the third color frequency CB.

3. The head-mounted color display contrast enhancing apparatus of claim 1 wherein said color filter includes a tricolor band-pass filter.

4. The head-mounted color display contrast enhancing apparatus of claim 1 wherein said color filter includes a clear medium printed with patterns of the same three colors used in the display.

5. The head-mounted color display contrast enhancing apparatus of claim 1 wherein said at least one color filter is formed as eyeglass lenses, and wherein said head mounting structure is formed as eyeglass frames holding said eyeglass lenses in proximity to the eye of the viewer.

6. The head-mounted color display contrast enhancing apparatus of claim 5 wherein said at least one color filter is incorporated into lenses in a pair of sunglasses.

7. The head-mounted color display contrast enhancing apparatus of claim 1 wherein said at least -tone color filter is formed as a visor, and wherein said head mounting structure is a helmet holding said visor in proximity to the eye of the viewer.

8. The head-mounted color display contrast enhancing apparatus of claim 1 wherein said at least one color filter and said head mounting structure are formed as at least one contact lens .

9. A head-mounted color display contrast enhancing apparatus, for use proximate eye of a viewer to enhance perceived signal contrast of a color display, wherein said color display emits light at predetermined emitted color frequencies, said apparatus comprising: eyeglass frames; and eyeglass lenses mounted in said eyeglass frames, said eyeglass lenses incorporating at least one color filter having a frequency selectivity characteristic that produces more attenuation at non-emitted color frequencies than at emitted color frequencies .

10. The head-mounted color display contrast enhancing apparatus of claim 9 wherein said at least one color filter comprises means for more greatly attenuating at least some light frequencies less than a first color frequency CR than light at the first color frequency CR, more greatly attenuating at least some light frequencies between the first color frequency CR and a second color frequency CG than light at the first color frequency CR or the second color frequency CG, more greatly attenuating at least some light frequencies between the second color frequency CG and a third color frequency CB than light at the second color frequency CR or the third color frequency CG, and more greatly attenuating at least some light frequencies more than the third color frequency CB than light at the third color frequency CB.

11. The head-mounted color display contrast enhancing apparatus of claim 9 wherein said color filter includes a tricolor band-pass filter.

12. The head-mounted color display contrast enhancing apparatus of claim 9 wherein said color filter includes a clear medium printed with patterns of the same three colors used in the display.

13. An enhanced-contrast color display system comprising: a color display for emitting at least a visible light of a first color frequency CR, which is selected to stimulate the red color pigment cones in human eyes, for emitting at least a visible light of a second color frequency CG, which is selected to stimulate the green color pigment cones in human eyes, and for emitting at least a visible light of a third color frequency CB, which is selected to stimulate the blue color pigment cones in human eyes; and color filter means, located away from said display and proximate at least one eye of a viewer, for more greatly attenuating at least some light frequencies less than said first color frequency CR than light at said first color frequency CR, more greatly attenuating at least some light frequencies between said first color frequency CR and said second color frequency CG than light at said first color frequency CR or said second color frequency CG, more greatly attenuating at least some light frequencies between said second color frequency CG and said third color frequency ^• CB than light at said second color frequency CR or said third color frequency CG, and more greatly attenuating at least some light frequencies more than said third color frequency CB than light at said third color frequency CB .

14. The enhanced-contrast color display system of claim 13 wherein said color display comprises a color cathode ray tube having red light-emitting phosphors, green light-emitting phosphors, and blue light-emitting phosphors, for producing light at the color frequencies CR, CG, and CB respectively, or near enough thereto that the light thus produced is relatively less attenuated by the color filter than is the ambient light.

15. The enhanced-contrast color display system of claim 13 wherein said color display comprises a flat panel display having red, blue, and green picture elements for producing light at the color frequencies CR, CG, and CB respectively, or near enough thereto that the light thus produced is relatively less attenuated by the color filter than is the ambient light .

16. The enhanced-contrast color display system of claim 13 wherein said color display comprises means for passing light containing at least the color frequencies CR, CB, and CG through a film, wherein said film includes colored pigments dispersed therein to selectively allow varying degrees of passage of light in mixtures of predominantly the frequencies CR, CB, and CG, wherein the colored pigments are patterned to form an image.

17. The enhanced-contrast color display system of claim 13 wherein said color display comprises at least one light source producing multiple frequencies of light, wherein said light from said at least one light source passes through a film including colored pigments dispersed therein to selectively allow varying degrees of passage of light in mixtures of predominantly the frequencies CR, CB, and CG, wherein the colored pigments are patterned to form an image .

18. The enhanced-contrast color display system of claim 13 wherein said display comprises at least one light source producing predominantly light at the frequencies CR, CB and CG, wherein said light from said at least one light source passes through a film including colored pigments dispersed therein to selectively allow varying degrees of passage of combinations of red, blue, or green light, wherein the colored pigments are patterned to form an image .

19. The enhanced-contrast color display system of claim 13 wherein said display includes at least one optic system, wherein the emitted light is projected and diffracted from a viewing surface.

20. An enhanced-contrast color display system comprising: a color display for emitting at least a visible light of a first color frequency CR, which is selected to stimulate the red color pigment cones in human eyes, for emitting at least a visible light of a second color frequency CG, which is selected to stimulate the green color pigment cones in human eyes, and for emitting at least a visible light of a third color frequency CB, which is selected to stimulate the blue color pigment cones in human eyes, wherein said light at said first, second and third color frequencies forms a color image; and a color filter located away from said display and proximate at least one eye of a viewer, wherein said color filter more greatly attenuates light at frequencies other than said first, second and third color frequencies than said visible light at said first, second and third color frequencies, thereby enhancing the perceived contrast of the image in the eyes of the viewer.

21. A method for enhancing the contrast of a color display, said method comprising: positioning a color filter in proximity to at least one eye of a viewer and between the viewer and the color display; causing light to be emitted by said display at predetermined emitted color frequencies, wherein said light forms an image; and viewing the image, wherein the color filter provides more attenuation at some non-emitted color frequencies than at said emitted color frequencies .

22. The method of claim 20 wherein said color filter is positioned such that most of the ambient light that would otherwise strike the eyes of the viewer is filtered by said color filter before striking the eyes of the viewer.

23. The method of claim 20 wherein said predetermined emitted color frequencies include a first color frequency CR, which is selected to stimulate the red color pigment cones in human eyes, a second color frequency CG, which is selected to stimulate the green color pigment cones in human eyes, and a third color frequency CB, which is selected to stimulate the blue color pigment cones in human eyes .

24. The method of claim 20 wherein causing light to be emitted by display includes emitting light using a color cathode ray tube such that the image is formed on the color cathode ray tube.

25. The method of claim 20 wherein causing light to be emitted by said display includes producing light on a flat panel display such that the image is formed on the flat panel display.

26. The method of claim 20 wherein causing said light to be emitted by said display includes passing said light at said emitted color frequencies through a film including colored pigments such that said image is projected onto a projection surface.

27. The method of claim 20 wherein causing said light to be emitted by said display includes producing light at said predetermined emitted color frequencies using a light source and passing said light through a film including colored pigments such that said image is projected onto a projection surface.