GB2368446A

GB2368446A - Display assembly

Info

Publication number: GB2368446A
Application number: GB0112478A
Authority: GB
Inventors: Paul Albert Voisin
Original assignee: BF Goodrich Avionics Systems Inc; Goodrich Avionics Systems Inc
Current assignee: Goodrich Avionics Systems Inc
Priority date: 2000-06-22
Filing date: 2001-05-22
Publication date: 2002-05-01
Also published as: FR2811089A1; GB0112478D0

Abstract

A display assembly for emitting a display image at a reduced viewing angle to avoid unwanted reflections of the display image to a viewer is disclosed. The display assembly comprises: an enclosure (110) having a frontal opening and a backlight (90) disposed therein; an liquid crystal display (44) disposed at the frontal opening and electrically controlled to project the display image to the viewer when illuminated by the backlight (90); and a microlouver film (60) disposed in the enclosure (110) between the backlight (90) and electro-optical array (44) to control the area of light illumination passed to the array (44) from the backlight (90) to reduce the viewing angle of the display image.

Description

2368446 A DISPLAY ASSEMBLY FOR EMITTING A DISPLAY IMAGE AT A REDUCED

VIEWING ANGLE

BACKGROUND OF THE INVENTION

The present invention relates to display assemblies, in general, and more particularly, to a display assembly for emitting a display image at a reduced viewing angle to avoid unwanted reflections of the display image to a viewer.

Display assemblies, especially those having application in avionics instruments, emit display images over a substantially wide viewing angle For the avionics applications, the display images are emitted within the cockpit of an aircraft for viewing by a pilot.

Reflections of the display images from the aircraft's canopy can impair the pilot's vision of the outside of the aircraft, creating the potential for a hazardous condition.

A typical display assembly for an avionics instrument is a backlighted liquid crystal display (LCD) assembly Generally, displays of this type include a diffuser disposed within an assembly enclosure between the backlight and the LCD array of elements to distribute light from a non-uniform backlight source, like a fluorescent lamp, for example, throughout a viewing envelope which causes the light to appear uniform to a viewer A second diffuser may be included in a night vision imaging system (NVIS) filter also disposed between the backlight and the LCD array The purpose of this second diffuser is to pre-diffuse light from collimating optics of the NVIS filter.

Light control films, such as the 3 M product LCF-P, for example, have been proposed to reduce or eliminate night time window reflections from a display in automotive and aeronautical applications The recommended usage of the light control films is to apply it to the external surfaces of the display element For more information on such light control films and their applications, reference is made to a 3 M product brochure from 3 M's Safety and Security Systems Division bearing number 75-0500- 1433-3-C and dated 1997.

Externally mounted light control films, while capable of eliminating display image reflections from the canopy of an aircraft cockpit, exhibit poor specular (glare) and diffuse reflectivity performance which makes ambient (sunshine) viewing difficult.

The present invention overcomes the aforementioned drawbacks of the prior art display assemblies to more effectively eliminate display image reflections to the viewer without affecting specular and diffuse reflectivity performance.

SUMMARY OF THE INVENTION

In accordance with the present invention, a display assembly for emitting a display image at a reduced viewing angle to avoid unwanted reflections of said display image to a viewer comprises: an enclosure having a frontal opening and a backlight disposed therein; an array of electro-optical display elements electrically controlled to project the display image to the viewer when illuminated by the backlight; and a light control film disposed in the enclosure between the backlight and electro-optical array to control the area of light illumination passed to the array from the backlight to reduce the viewing angle of the display image.

BRIEF DESCRIPTION OF THE DRAWINGS

The following includes a more detailed description of display assemblies that are in accordance with the invention, by way of example, reference being made to the appended schematic drawings which are:

Figure 1 is an illustration of a cockpit which may serve as a suitable environment for the present invention; Figure 2 is an isometric breakout view of components exemplifying a conventional display assembly; Figure 2 A is an isometric breakout view of components of a conventional backlight assembly suitable for use in the display assembly of Figure 2; Figure 2 B is an isometric breakout view of components of a conventional enclosure suitable for enclosing the display assembly of Figure 2; Figure 3 is an isometric breakout view of components of a display assembly suitable for embodying the principles of the present invention; Figure 4 is a top view illustration of a light control film suitable for use in the display assembly embodiment of Figure 3; Figure 4 A is a magnified top view illustration of the light control film depicted in Figure 4; and Figure 5 is an illustration of a cockpit for depicting a reduced viewing angle of the display assembly embodiment of Figure 3.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 is an illustration of a cockpit environment suitable for embodying a display assembly as part of an avionics instrument for viewing by a pilot of an aircraft Referring to Figure 1, a pilot 10 is seated in a cockpit 12 of an aircraft The cockpit 12 is surrounded by a canopy 14 and includes an avionics panel 16 An avionics instrument including a display assembly 18 is disposed in the cockpit 12 at the panel 16 for viewing by the pilot 10 along a direct viewing line 20 As described herein above, without the use of applicant's invention, the pilot 10 may encounter unwanted reflections of the display image, like that shown at area 22 on the canopy 14, for example.

A typical display assembly 18 of the avionics instrument is shown in greater detail in the isometric view of display assembly components of Figure 2 Referring to Figure 2, data interface circuitry for interfacing the display with the avionics instrument is disposed on a printed circuit (PC) card 30 which is mounted on a reflector housing with screw elements 34.

The PC card 30 is spaced from the housing 32 by spacers 36 which accommodate the screw elements 34 and secure the PC card to the housing 32 Between the PC card 30 and housing 32 is a backlight assembly 31 (not shown) disposed in assembly 18 to emit light toward the front of an enclosure which will be described in greater detail herein below The backlight may be a fluorescent lamp, incandescent lamp, electro-luminescent panel or the like, for example Figure 2 A is a breakout illustration exemplifying a backlight assembly 31 for use in the present embodiment Referring to Figure 2 A, a fluorescent lamp 90 is disposed on one side of a machined aluminum plate 92 which functions as a heat sink for the backlight The fluorescent lamp 90 may be serpentined across the one side of plate 92 taking the shape of a rounded M, for example Cathodes 94 of the fluorescent lamp are disposed on the other side of the plate 92 and connected through wires (not shown) to a printed circuit card 96 also disposed on the other side of the plate 92 The card 96 includes interface electronics for governing the operation of the lamp Heat sink bumps 98 are provided on the other side to expand the surface area thereof, and thus, improve heat sink efficiency A connector 100 is mounted on the card 96 for making connection to a power supply card 102 which functions to supply power to the fluorescent lamp via connector 100 Various screws 104 and other assembly elements 106 are used to assemble the card 102 to the plate 92 in a conventional manner.

Referring back to Figure 2, a passageway for the emitted light from the backlight assembly 31 is provided through the housing 32 to permit illumination of an LCD array of elements 44 The housing 32 also includes interconnect circuits 38 to electrically couple gate drivers 40 and column drivers 42 of the LCD array of display elements 44 to the data interface circuits of the PC card 30 The LCD array may be of the type manufactured by Planar Systems bearing model number SISM AM 3 ATI-001, for example Sandwiched between the housing 32 and LCD array 44 are a collimating film 46, an NVIS filter with a diffuser 48, an alignment ring and a diffuser 52 in that order going from front to rear of the assembly 18 The collimating film 46 may be of the type manufactured by 3 M Corporation, for example The NVIS filter 48 may be of the type manufactured by Oxley, Inc laminated with a diffuser of the type manufactured by Nitto bearing model number LDS-19 W, for example And the diffuser 52 may be of the type manufactured by Physical Optics Corporation bearing model number LSD 95 x 25 PC 20, for example A temperature sensor 53 which may be of the type manufactured by Analog Devices bearing model number AD 590, for example, is disposed at the LCD array and interconnected to the circuit 38 of the housing 32 Securing the aforementioned assembly of components to the housing 32 is a retainer 54 utilizing screws 56 Gaskets 58 are disposed between the retainer 54 and LCD array 44 The LCD array 44 is electrically controlled by the avionics instrument via interface electronics 30 and interconnect circuit 38 to project a display image from a frontal opening of an enclosure (see below) to the pilot (viewer) when illuminated by the backlight assembly 31.

6 Figure 2 B illustrates a suitable enclosure 110 for enclosing the components of the display assembly 18 Referring to Figure 2 B, the enclosure 110 includes a frontal opening 112 through which the assembly 18 may be disposed within the enclosure and through which the LCD array of elements 44 may emit a display image to the viewer A display bezel 114 is mounted about the periphery of the enclosure 110 at the opening 112 and includes two control knobs 116 and 118 which may be electrically connected to the electronics board 30 for controlling various aspects of the displayed image Mounted between the bezel 114 and the enclosure 110 are a gasket 120 and mask 122 which may be made of a brass material with a black oxide coating, for example, for- preventing light from leaking out of the sides of the opening 126 between the bezel 114 and enclosure 110 The enclosure also includes ventilating holes at 124 and 126, for example, for allowing hot air to pass through the enclosure to the ambient In addition, the enclosure 110 may include one or more removable cover plates 128 for access to the display assemble 18 within the enclosure for testing, maintenance or other purposes The display assembly 18 may be secured to the enclosure 110 by mounting screws 130 through sidewalls of the enclosure.

In operation, the backlight assembly 31 emits light which passes through the collimating film 46, the NVIS filter/diffuser 48, diffuser 52, and on to the liquid crystal display 44.

Accordingly, diffused light is projected onto a back polarizer of the liquid crystal display 44 The column and row pixel elements of the liquid crystal display 44 which are sandwiched between the rear and a front polarizer act as shutters for the light, but do not have much effect on the angular properties of light entering and exiting the display Thus, light exiting the display 44 through opening 126 of the enclosure 110 will have similar angular properties to those of the light entering the display Images projected by the liquid crystal display to the viewer are defined by digital data provided to the data interface circuit 30 This digital data that defines the image is provided to the interface card 30 which updates the image of the display by selecting one row of the display at a time The interface card 30 loads the digital information for each pixel of a selected row into its column driver(s) which convert the digital data for each pixel into a discrete voltage for each individual column output Next, the interface card 30 signals its row driver circuitry to enable/select the first row of the display The discrete voltages of each column driver output are now able to charge /discharge their corresponding pixels of the selected row.

Then, the selected row driver output is disabled and the next row is selected This process repeats until all rows of the display 44 have been addressed, upon which time the first row is selected 7 and the process repeats itself again The voltage applied to each pixel rotates the light's plane of vibration which determines if the light polarized by the rear polarizer of the display will pass through the front polarizer or be absorbed by the front polarizer Rotating the light's plane of vibration does not alter the direction of travel however Each pixel also contains either a red, green, blue, or white color filter The colored light that passes through the front polarizer is seen by the viewer as the image and the light from pixels that are blocked by the front polarizer is not seen (black).

In an embodiment of the present invention as shown in Figure 3, the diffuser 52 of the display assembly is replaced with a light control film element 60 that is used to control the area of light illumination passed to the LCD array 44 from the backlight assembly 31 to reduce the viewing angle of the display image emitted to a viewer from the LCD array 44 Suitable for this application is a film marketed by 3 M Corporation under the model name LCF or LCF-P For more details of this film, reference is made to the 3 M product specification publication from

3 M's Safety and Security Systems Division bearing publication number 750500-1433-3-C and dated 1997.

Top view illustrations of an exemplary light control film 60 for use in the display assembly embodiment are shown in Figures 4 and 4 A For the present embodiment, the light control film is of the type manufactured by 3 M bearing model descriptor LCF-P ABR 2 AG 48, Type 011 Tbk 034 Figure 4 A is a magnified top view of the film of Figure 4 illustrating the details thereof Referring to Figure 4 A, the film 60 comprises a layer of closely spaced microlouvers shown at 62, which may be of a predetermined thickness say on the order of 010 inches, for example, and may be aligned at a predetermined louver angle say on the order of 0 degrees, for example One side 64 of each microlouver may comprise a light absorbing matte type material, having a 3 M descriptor 90 % Gloss view side, for example, and the other side 66 of each microlouver may comprise a glossy type material, having a 3 M descriptor Gloss on back side, for example, which reflects light The light control film 60 may also comprise protective layers 68 of a polycarbonate material, for example, covering the layer of microlouvers 62 These protective layers may be of a thickness of 010 inches, for example Finally, a thin anti-reflective coating may be applied to the exit side of film 60 For more details of the microlouvers 62 reference is made to the aforementioned 3 M publication.

8 Referring to the top view illustration of Figure 4, in operation, light from the backlight assembly 31 which has a wide angle illumination pattern shown at 72 enters one side 74 of the film 60 and exits the other side 76 with a reduced illumination pattern shown at 78, for example.

In the present example, light entering the film may have a pattern that is substantially 90 degrees from a center line of the film and light exiting the film may have a pattern of 45 degrees from center The microlouvers in the light control film 60 reduce the angle at which light is projected onto the liquid crystal display 44 The aspect ratio of the microlouvers determines the amount of angular reduction achieved As has been explained above, the pixel elements of the display 44 act as shutters and have very little scattering effect on light entering the display Thus, light exiting the display will have a similar angular reduction This reduced area of illumination of the LCD array 44 causes a reduced viewing angle of the display image from the display assembly 18 such as that shown in the cockpit illustration of Figure 5.

Accordingly, any unwanted image reflections from the canopy 14 will be projected behind the pilot 10 as shown at area 80, for example.

While the present embodiment has been described herein above in connection with one or more embodiments, it was done so merely by way of example and no limitations found in the foregoing described embodiments should be imparted to the present invention Rather, the present invention should be construed in broad scope and breadth in accordance with the recitation of the appended claims.

Claims

1 A display assembly for emitting a display image at a reduced viewing angle to avoid unwanted reflections of said display image to a viewer, said display assembly comprising:

an enclosure having a frontal opening; a backlight disposed within said enclosure; an array of electro-optical display elements electrically controlled to project said display image to said viewer when illuminated by said backlight; and a light control film disposed in said enclosure and between said backlight and said array to control the area of light illumination passed to said array from the backlight to reduce the viewing angle of the display image.

2 The display assembly of claim 1, wherein the array comprises an array of liquid crystal display elements.

3 The display assembly of claim 1 or claim 2, wherein the backlight consists of a lamp type of the group of fluorescent, incandescent and electro- luminescent.

4 The display assembly of any one of claims 1 to 3, wherein the light control film comprises a plurality of closely spaced microlouvers having a predetermined thickness and aligned at a predetermined louver angle to allow light from the backlight to pass at a predetermined angle of illumination to the array of electro-optical display elements.

The display assembly of claim 4, wherein said microlouvers of the light control film are comprised of a light absorbing material.

6 The display assembly of claim 4 or claim 5, wherein the light control film comprises a thin layer of material covering the microlouvers.

7 The display assembly of any one of claims 1 to 6, wherein the display assembly is part of an avionics instrument disposed in the cockpit of an aircraft; and the viewer is a pilot located in close proximity to the display assembly.

8 The display assembly of claim 7, wherein the unwanted reflections comprise reflections from a canopy of the aircraft; and wherein the reduced viewing angle of the display image renders the canopy reflections out of view of the pilot.

9 The display assembly of any one of claims 1 to 8, including a NVIS filter and diffuser disposed in the enclosure between the backlight and the light control film.

The display assembly of any one of claims 1 to 9, including a collimating film disposed in the enclosure between the backlight and the light control film.

11 The display assembly of any preceding claim, wherein the array is disposed at the frontal opening of the enclosure.

12 A display assembly substantially as hereinbefore defined with reference to Figures 3, 4, 4 A and 5.