FR2811089A1 - Image display system with reduced visual angle to avoid undesirable reflections, for use in aircraft cockpit - Google Patents

Abstract

The image display system (18) comprises a housing with a front opening, a retro-illumination device inside the housing, a set of electrically controlled optoelectronic display elements (44) accommodated in the front opening for projecting the image to the observer, and a light-control film (60) positioned between the retro-illumination device and the set of optoelectronic elements for controlling the surface illumination by transmitted light. The set of display elements (44) comprises a set of liquid-crystal display (LCD) elements. The retro-illumination device comprises a lamp such as fluorescent, incandescent, or electroluminescent. The light-control film (60) comprises a multitude of closely spaced micro-shutters having a predetermined thickness and aligned at a predetermined slit angle so that the light propagates at a predetermined angle to the set of display elements. The micro-shutters contain a light-absorbing material, and the light-control film contains a thinn layer of material covering the micro-shutters. The display system is a part of an aircraft instrument panel laid out in cockpit, and the pilot is seated in the immediate vicinity of the system. The undesirable reflections are from the glass roof of aircraft, and the reduced visual angle puts the reflections out of the view of pilot. The display system comprises a nocturnal vision image system (NVIS) filter and a diffusor (48) positioned inside the housing between the retro-illumination device and the light-control film. The display system comprises a collimator layer (46) in the housing between the retro-illumination device and the light-control film.

Description

The present invention generally relates to systems

  mes display, and more particularly a display system

  chage to emit a display image at an angle

  reduced observation to avoid unsubstantiated reflections

  hated from the displayed image to an observer.

  Display systems, and more particularly those having an application in avionics instruments, emit display images from a relatively wide viewing angle. For avionics applications, display images are emitted inside the passenger compartment of an aircraft to be seen by a pilot. Reflections of images displayed from the aircraft canopy can interfere

  the pilot’s vision out of the plane, creating

  essentially a dangerous situation.

  A typical display device for an instrument

  avionics is a backlit display system with

  liquid rates (LCD). In general, displays of this type

  include a diffuser arranged in a device housing

  tif between the backlight source and the group of

  liquid crystal display elements for distributing light from a non-uniform backlight source,

  such as a fluorescent lamp, for example, in an enclosure

  viewing window which causes light to appear uniform to an observer. A second diffuser can be

  included in an imaging system filter for night vision

  turne (NVIS) also arranged between the backlight source and the group of liquid crystal display elements. The purpose of this second diffuser is to pre-diffuse the light

  from optical collimators of the NVIS filter.

  Illumination control films, such as

  LCF-P from 3M, for example, has been proposed

  to reduce or eliminate, at night, window reflections from a display in automotive and aeronautical applications. The recommended use of lighting control films is to apply them to the surface

  display element. For more information

  tions on such lighting control films and their applications, refer to a product brochure

  of the "Security Systems" Division of 3M company

  number 75-0500-1433-3-C, dated 1997.

  Illumination control films mounted externally

  laughing, although they are able to eliminate display image reflections from the canopy of the passenger compartment

  aircraft, perform poorly in re-

  specular bending (harsh light) and in reflective power

  diffuse which make observation in light difficult

  ambient (sun). The present invention overcomes the disadvantages

  previously mentioned displays of display systems

  the prior art to more effectively eliminate

  bending towards the viewer of displayed images without affecting

  performance in specular reflection and in power

flexing diffuse.

  According to the present invention, a display system for emitting a display image from a reduced angle of observation in order to avoid unwanted reflections towards an observer of said display image comprises: a housing having a front opening and a device for

  backlight arranged in it; a group of opto elements

  display electronics arranged in the front opening

  and electrically controlled to project the display image

  ge towards the observer when they are lit by the dispo-

  backlight sitive; and a light control film

  arranged in the housing between the backlight device

  ge and the optoelectronic group to control the illumination surface transmitted to the group from the backlight device in order to reduce the observation angle of

the display image.

  The invention will be better understood in the light of the

  description which follows, referring to the drawings given

  by way of example only and not limiting.

  Figure 1 is a representation of a passenger compartment which can serve as an environment suitable for the present invention. Figure 2 is an exploded perspective view of components showing an example of a conventional display system. Figure 2A is an exploded perspective view of

  components of a conventional backlight system

  for use in the display system of the

figure 2.

  Figure 2B is an exploded perspective view of components of a conventional housing suitable for containing the

  Figure 2 display system.

  Figure 3 is an exploded perspective view of components of a display system suitable for implementation

  work of the principles of the present invention.

  FIG. 4 is a top view showing a light control film suitable for use in the display system embodiment of FIG. 3. FIG. 4A is an enlarged top view of the film of

  light control shown in figure 4.

  Figure 5 is a representation of a passenger compartment

  to show a reduced angle of observation of the mode of realization

  The display system of Figure 3.

  As indicated above, Figure 1 is a representation

  feeling of a cabin environment suitable for setting

  implementation of a display system forming part of an ins-

  avionics tool to be observed by the pilot of an airplane. Referring to Figure 1, a pilot 10 is seated in a passenger compartment 12 of an aircraft. The passenger compartment 12 is surrounded by a canopy 14 and includes a dashboard 16. An avionics instrument comprising a display system 18 is placed in the passenger compartment 12 on the dashboard 16 to be observed by the pilot 10 along line 20 of

  direct viewing. As described above, without the use of

  sation of the applicant's invention, the pilot 10 may be confronted with parasitic reflections from the displayed image, such as that represented in an area 22 on the canopy 14,

for example.

  A typical display system 18 of the avionics instrument is shown in more detail in the exploded perspective view of the components of the display system.

  FIG. 2. Referring to FIG. 2, an information circuit

  data terface to interface the display with the

  avionics tool is placed on a printed circuit board 30 which is mounted on a reflector box 32 at the

  by means of screwing elements 34. The circuit board 30 im-

  The award-winning is spaced from the housing 32 by spacers 36 which receive the screwing elements 34 and fix the printed circuit board to the housing 32. Between the printed circuit board 30 and the housing 32 is a backlight sub-assembly 31 ( not shown) arranged in the system 18 to emit light towards the front of a box which

  will be described in more detail below. The re-

  backlight may be, for example, a fluorescent lamp, an incandescent lamp, an electroluminescent panel or the like. Figure 2A is a representation

  exploded view showing an example of a sub-assembly 31 of retro-

  lighting intended for use in this mode of

  production. Referring to Figure 2A, a fluorescent lamp

  rescent 90 is arranged on one side of a machined plate 92

  aluminum which serves as a heat sink for the

  backlight positive. The fluorescent lamp 90 can be arranged in a serpentine through one side of the plate 92 and can take, for example, the shape of a rounded M. Cathodes 94 of the fluorescent lamp are arranged on the other side of the plate 92 and connected by means of wires (not shown) to a printed circuit board 96 also disposed on the other side of the plate 92. The card 96 also includes an electronic interface circuit for controlling the

  operation of the lamp 90. Protrusions 98 of the

  heat sink are provided on the other side for ac-

  grow the surface of it and therefore increase the efficiency of the heat sink. A connector 100 is mounted on the card 96 to establish a connection with a power supply card 102 which serves to supply energy 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 of a

classic way.

  Returning to Figure 2, a passage for the light-

  re emitted from the backlight device 31

  is made through the housing 32 to allow the illumination

  rage of a group of liquid crystal display elements 44

  of. The housing 32 also includes interconnection circuits 38 for electrically coupling gate drives and drive devices 42.

  column of group of liquid crystal display elements 44

  to the data interface circuits of the printed circuit board 30. The group of liquid crystal elements can be of a type manufactured by the company Planar Systems under the model number SISM AM3ATI-001, for example. Sandwiched between the housing 32 and the group of liquid crystal display elements 44, there is a collimation layer 46, an imaging filter for night vision

  with a diffuser 48, an alignment ring 50 and a diffuser

  sor 52 in order from front to back of the system

  me 18. The collimation layer 46 can be of the type

  manufactured by 3M Corporation, for example. Thread-

  tre 48 imagery for night vision can be of the type

  manufactured by Oxley, Inc., laminated with a diffuse

  of the type manufactured by the company Nitto under the reference LDS-19W, for example. And the diffuser 52 can be of the type manufactured by the company Physical Optics Corporation under the

  reference LSD95x25PC20, for example. A temperature sensor 53

  strip which may be of the type manufactured by the company Analog Devices under the reference AD590, for example, is placed on the group of liquid crystal display elements and interconnected to circuit 38 of the housing 32. The fixing of the above-mentioned assembly of components of the housing 32 is provided by a frame 54 using screws 56. Seals 58 are arranged between the frame 54 and the group of liquid crystal display elements 44. The group of liquid crystal display elements 44 is electrically controlled by the avionics instrument via the circuit

  interface electronics 30 and interface circuit 38

  connection to project a display image of an opening

  front of a box (see below) towards the pilot (observer) when it is illuminated by the backlight device 31. Figure 2B shows a housing 110 suitable for containing the components of the display system 18. In

  referring to FIG. 2B, the housing 110 comprises an or-

  front edge 112 through which the system 18 can be disposed in the housing and through which the group of liquid crystal display elements 44 can output a display image to the viewer. A display flange 114 is mounted around the periphery of the housing on the opening 112 and comprises two buttons 116 and 118

  which can be electrically connected to the

  te 30 of electronics to control various characteristics

  of the displayed image. Mounted between the flange 114 and the housing 110, there is a seal 120 and a mask 122 which can be made of a brass-based material with a black oxide coating, for example, to prevent light from escaping through the sides of the opening 126

  between the flange 114 and the housing 110. The housing comprises

  also takes ventilation holes 124 and 126, for example

  full, to allow hot air to pass out of the housing. In addition, the housing 110 may include one or more removable cover plates 128 for access to the display system 18 in the housing in

  testing, maintenance or other purposes. The system 18 affi-

  chage can be fixed to the housing 110 by screws 130 of my

  tage entering the side walls of the housing.

  In operation, the sub-assembly 31 of retro-

  lighting emits light which passes through layer 46 of col

  limitation, the NVIS filter / diffuser 48, the diffuser 52, for

  arrive on the liquid crystal display 44. Therefore

  quence, a scattered light is projected on a rear polarizer of the liquid crystal display 44. The column and row pixels of the liquid crystal display 44 which are sandwiched between the rear and a front polarizer serve as light shutters, but do not have much effect on the angular properties of the light

  entering and leaving the display. So the lu-

  out of the display 44 through the opening 126 of the box

  tier 110 will have angular properties similar to those

  light entering the display. Projected images

  ted by the liquid crystal display to the observer are defined by digital data supplied to the circuit

  data interface. This digital data which

  The image is sent 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 in a separate row

  selected in its column driver (s) which convert the digital data for each pixel into a discrete voltage for each individual output of

  column. Then, the interface card 30 indicates on its circuit

  cooked row attack to activate or select the first row of the display. The discrete voltages of each column driver output can now charge or discharge their corresponding pixels in the selected row. Then the selected output

  of the row attack device is deactivated and the

  next age is selected. This process is repeated until all the rows of the display 44 have

  been addressed, after which the first row is selected-

  born and the process repeats again. The applied voltage

  that at each pixel rotates the polarization plane of

  light which determines whether the light polarized by the po-

  the rear viewfinder will cross the front polarizer or be absorbed by the front polarizer. A rotation

  of the plane of polarization of the light does not modify the di-

  propagation rection, however. Each pixel also contains a color filter, either red, green or

  blue or white. The colored light that crosses the polar-

  front viewer is seen by the observer as the image, and the light of pixels that are blocked by the front polarizer

is not seen (black).

  In an embodiment of the present invention as shown in FIG. 3, the diffuser 52 of the display system is replaced by an element 60 forming a film of

  light control, which is used to control the over-

  illuminating face transmitted to the group 44 of liquid crystal display elements from the backlight sub-assembly 31 in order to reduce the viewing angle of the display image sent to an observer from the group 44 d liquid crystal display elements. There is a film sold by 3M Corporation

  under the reference LCF or LCF-P suitable for this applica-

  tion. For more details on this film, we refer to the

  publication of product specification of the Division "Sys-

  Safety Temes "from 3M company number

  publication 75-0500-1433-3-C and dated 1997.

  Top view illustrations of an example light control film 60 for use in the display system embodiment are shown in Figures 4 and 4A. For the present embodiment, the light control layer is of the type manufactured by 3M under the reference LCF-P ABR2 AG48, type 011 Thk.034. The

  FIG. 4A is an enlarged top view of the film of the fig.

  re 4 which shows the details. Referring to Figure 4A, the film 60 includes a layer of closely spaced micro-flaps shown at 62, which may have a predetermined thickness in the range of 0.010 inch (0.254 mm)

  for example, and which can be aligned at a predetermined angle

  born of cleft which can be of the order of 0 degrees, for example-

  ple. One side 64 of each micro-flap may comprise a matte light-absorbing material, having a 3M descriptor of 90% gloss on the visible side, for example, and the other side 66 of each micro-flap may comprise a material of the type glossy having a glossy 3M descriptor on the back side, for example, that reflects light. The light control film 60 may also include layers

  protectors 68 of polycarbonate material, for example

  ple, covering the layer of micro-flaps 62. These protective layers may have a thickness of 0.010 inch

  (0.254 mm), for example. Finally, an anti-

  flounder can be applied on the output side of film 60. For more

  details on the micro-flaps 62, see the pu-

3M abovementioned.

  Referring to the top view illustration of Figure 4, in operation, light from the backlight subassembly 31, which has a wide angle illumination pattern shown at 72, enters a side 74 of the film 60 and comes out on the other side 76 with a

  reduced illumination diagram shown in 78, for example

  ple. In the present example, the light entering the

  movie can have a diagram that has about 90 degrees of-

  then a central axis of the film and the light coming out of the film can have a 45 degree diagram from the center. The

  micro-shutters in the reduced light control film 60

  senses the angle at which light is projected on the liquid crystal display 44. The aspect ratio of the micro-shutters

  determines the proportion of angular reduction obtained. com-

  me it was described above, the pixel elements of the affi-

  cheur 44 serve as shutters and have a dispersing effect

  very reduced on the light entering the display.

  Thus, the light coming out of the display will have a similar reduction in angle. This reduced area of illumination of the

  group 44 of liquid crystal display elements

  do a reduced viewing angle of the display image from the display system 18, such as that shown

  in the illustration of the passenger compartment in Figure 5. As a result

  quence, any parasitic reflection from the canopy 14 will be projected behind the pilot 10 as represented by an area

, for example.

Claims (10)

  1. Display system for emitting a display image   plugging in at a reduced viewing angle to avoid   unwanted reflections to an observer of said ima-   a display, said display system comprising: a housing (110) having a front opening (112);   a backlight device (31) disposed in said housing;   a group (44) of optoelectronic elements of affi   electrically controlled chage to project said display image to said observer when the group is illuminated by said backlight device (31), said group (44) being disposed in said front opening (112) of said housing (110); and a light control film (60) disposed in   said housing (110) between said feedback device (31)   lighting and said group (44) for controlling the luminous lighting surface transmitted to said group from said   backlighting device to reduce the angle of ob- servation of the display image.   2. Display system according to claim 1, characterized in that said group (44) comprises a group   liquid crystal display elements.   3. Display system according to claim 1,   characterized in that said backlight device (31)   ge includes a type of lamp chosen from the group compre-   for fluorescent, incandescent and electroluminescent lamps. 4. Display system according to claim 1, characterized in that said light control film (60)   includes a plurality of closely spaced micro-flaps (62)   paces having a predetermined thickness and aligned at a   predetermined angle of slit to allow light is-   of said backlight device (31) to propagate with a predetermined angle of light towards said group   (44) optoelectronic display elements.   5. Display system according to claim 4, characterized in that said micro-flaps (62) of said film (60) of light control are made of a material absorbing light.   6. Display system according to claim 4, characterized in that the light control film (60) comprises a thin layer of material covering the micro-flaps. 7. Display system according to claim 1,   characterized in that the display system (18) forms part of   tie of an avionics instrument placed in the cockpit (12) of an airplane, and that the observer is a pilot (10)   located in the immediate vicinity of the display system.   8. Display system according to claim 7,   characterized in that the unwanted reflections include   reflect reflections from a canopy (14) of the aircraft, and that the reduced viewing angle of the display image puts   reflections on said canopy out of sight of the pilot.   9. Display system according to claim 1, characterized in that it comprises an NVIS filter (48) for   night vision and a diffuser (52) arranged in the housing   tier (110) between the backlight device (31) and the light control film (60).   10. Display system according to claim 1,   characterized in that it comprises a layer (46) of collima-   tion disposed in the housing (110) between the device (31)   backlight and the light control film (60).