EP1231620A1

EP1231620A1 - Control panel with laser backlight

Info

Publication number: EP1231620A1
Application number: EP01400359A
Authority: EP
Inventors: Alberto Borgonovo
Original assignee: Thomson Licensing SAS
Current assignee: Thomson Licensing SAS
Priority date: 2001-02-12
Filing date: 2001-02-12
Publication date: 2002-08-14

Abstract

The present invention is related to a control panel and in particular to remote controls equipped with a backlight system. The backlight system comprises at least one laser diode as light source and mirrors or other beam splitting elements to direct portions of the laser light to operating keys of the remote control. The use of a laser diode and deflecting elements provides a very efficient backlight system reducing the energy consumption and thereby enhancing the battery lifetime of a remote control. The remote control according to the invention also allows new design opportunities.

Description

The present invention is related to a control panel and in particular to a control panel equipped with a backlight system. A typical application of a control panel according to the invention are remote control devices, which are well-known and widely used e.g. for consumer electronic devices.
However, the present invention is not limited to remote controls but is applicable to any control panel requiring a backlight system. Even though the description will be focused on remote controls, the invention can easily be applied to other types of control panels e.g. front-panel controls.
Present remote control devices e.g. for operating consumer electronic devices become increasingly complex in the sense that a considerable number of buttons or keys is required to be able to access all features available on modern consumer electronic equipment. Frequently, there are dedicated keys associated with special functions for particular devices. The proper operation of these keys requires that a user reads the labels of these keys because it cannot be expected that every user simply knows the location of a key he needs to press to call for a certain function of the controlled device. However, consumer electronic devices like TV receivers and videocassette recorders (VCR) are often operated under dark conditions making it difficult for the user to read the respective labels on the keys of the remote control. Therefore, many remote controls are equipped with a backlight system illuminating the keys of the remote control. As a backlight source usually light emitting diodes (LED) are used as a light source. Light guiding elements and/or diffusors are used to direct and distribute the light from the LEDs to the key areas or the labels, which are to be illuminated. For this purpose it is also known to utilize a translucent rubber mat to realize the keys and at the same time a guiding element guiding the light to the keys. In this known remote control the light is generated by a plurality of LEDs mounted on the printed circuit board of the remote control and accommodated in pockets inside the rubber mat. In order to allow a user to see all keys on the remote control simultaneously all LEDs must be switched on. This brings on a corresponding energy consumption, which is not neglectable for a battery operated device.
In this type of remote controls it is an issue to distribute the light evenly between different keys or inside a large key when light guiding elements are used. Besides that, it is important to limit the energy consumption of the light source, the plurality of LEDs, in order to enhance the lifetime of the batteries of the remote control.
It is therefore desirable to provide a new type of remote controls equipped with a backlight system having low energy consumption and at the same time supplying a sufficient amount of light to the keys or labels of the remote control, so that the labels or keys remain readable also under dark conditions.
According to the invention a control panel is provided which is equipped with electronic circuitry comprising a signal emitter to send control signals. The control panel is provided with operating elements or keys for inputting commands associated with control signals. The operating elements are translucent and are illuminated by a light source. According to the invention a laser emitting a light beam forms the light source. A beam splitter is provided separating a portion out of the light beam emitted by the laser and directing it to an operating element. As a consequence the entire operating element becomes luminous.
The invention allows distributing the light from the laser in an efficient way with low losses. Furthermore, production costs for the control panel are reduced because of the absence of light guiding elements.
In an embodiment of the invention the control panel is provided with a plurality of beam splitters and each beam splitter separates a portion of the light beam emitted by the laser and directs this portion to an operating element or key. It is advantageous to use a plurality of beam splitters instead of a plurality of light sources because it allows limiting the energy consumption of the control panel. This is particularly advantageous when the control panel is incorporated in a battery-operated remote control because the energy consumption of the backlight source is the predominant factor limiting the lifetime of the batteries.
In one embodiment of the invention the beam splitters are formed by a mirror. In another embodiment of the invention the beam splitters are formed by semi-transparent elements. Finally, in yet another embodiment of the invention the beam splitters are formed by prisms. All beam splitters can be produced easily at low costs and are also economically advantageous compared to conventional light guiding elements.
In a control panel according to the invention the beam splitters are arranged in a sequence along progression direction of the light beam emitted by the laser. This arrangement allows illuminating efficiently a plurality of keys.
A plurality of beam splitters also provides the opportunity to illuminate different keys in a different intensity by separating and directing different portions of the light beam to the respective keys. The inventive arrangement also provides new design opportunities for the control panel making it easier to handle or more attractive for the consumer.
Finally, in one embodiment of the invention the control panel is provided with a plurality of lasers each having an associated beam splitter or an associated set of beam splitters directing portions of the light beams to the operating elements or keys of the remote control. This is a convenient arrangement for control panels, for which one laser does not provide a sufficient amount of light to illuminate all operating elements satisfactorily. Also in control panels where the light paths to reach every key are too complicated, it is convenient to use more than one laser as light source. In such an arrangement it is also possible to direct one or more beams to one key to generate an intense illumination and/or an illumination with different colours.
As mentioned above the control panel according to the present invention can be applied in a very beneficial way to remote controls having a backlight system. Of course the invention is not limited to this application even though the description will focus on a remote control as an illustrative exemplary embodiment of the invention.
In the drawing two different types of remote controls are shown.
Fig. 1a shows the exterior of a conventional remote control equipped with a backlight system;
Fig. 1b displays schematically the backlight system of the remote control shown in Fig. 1a, and
Fig. 2 shows schematically the backlight system of a remote control according to the invention.
The invention will be better understood by reading the detailed description accompanied by the drawing.
In Fig. 1a, a conventional remote control is shown indicated with the reference symbol 1 as a whole. The remote control 1 comprises a first selection switch 2 and a second selection switch 3 to select a VCR or a TV to be operated by the remote control 1 selectively. To enable the operation of the two different devices requires a relatively large number of keys on the remote control. In the lower portion 4 of the front panel of the remote control the control keys for operating VCR are arranged like "play", "stop", etc. In the upper portion 6 of the front panel a "menu" key 7, arrow keys 8 to navigate inside a menu and predominantly a volume up/down key 9 and a programme up/down 11 are arranged to name a few of the keys which are mainly used when the TV is controlled. In the middle portion 12 of the front panel of the remote control number keys are arranged to input a programme number.
In view of the large number of keys of the remote control it is apparently impossible for most users to know or remember the location of each key on the front panel. Consequently, the user has to look at the remote control and find the key he has to press to initiate the control function he intends to execute. However, usually it is relatively dark where TV is watched and therefore it is difficult to recognize individual buttons or keys or the labelling arranged on the button or in the vicinity of the button. To remedy this problem the remote control is equipped with the backlight system, which is shown schematically in Fig. 1b.
Fig. 1b visualizes schematically the printed circuit board (PCB) with a number of LEDs 13 forming the light source of the backlight system of the remote control. The LEDs are distributed across the surface of the PCB and located close to contact areas 14 of control keys of the remote control. The light of the LEDs 13 is guided and distributed through a translucent rubber mat (not shown), which forms also the control keys that can be brought into contact with their associated contact areas. Evidently, a considerable number of LEDs 13 are required to illuminate all control keys of the remote control. For the sake of simplicity the remainder of the electronic circuit is not shown in Fig. 1b apart from two transmitter diodes 16. In particular, batteries for supplying power, a micro controller for controlling the remote control and electrically conductive paths for interconnecting the electronic components are not shown in Fig. 1b. Of course, the number of LEDs 13 can be smaller or larger than the number of LEDs shown in Fig. 1b. In any case, the energy consumption of the backlight system corresponds to the number of LEDs mounted on the PCB and an increasing number of LEDs reduces the effective lifetime of the batteries used as power supply.
In Fig. 2 the backlight system of a remote control according to the invention is illustrated. The remote control indicated only schematically as an oval 20 comprises a number of control keys 21a - 21g made out of a luminescent material. In particular, this material has the property that when illuminated at one spot or in one region it re-emits light and re-absorbs it until the key is globally and evenly luminous. The backlight system further comprises a laser diode 22 emitting a light beam 23. The light beam consists of essentially parallel light and has a width WO. If the utilized laser diode generates only a divergent light beam or if the beam is too focused it is shaped with optical lenses such that the desired essentially parallel light beam 23 is generated. An appropriate lens system is known in the prior art and is not shown in Fig. 2. The light beam 23 is directed towards a first mirror 24. The mirror 24 is arranged such that a first portion 26 for the light beam 23 is separated from the originally emitted light beam 23 and directed towards the key 21e. As a consequence, the key 21e becomes luminous. The light beam 23 continues to propagate with a reduced width W1 and impinges partially on the second mirror 27. The second mirror 27 separates a second portion 28 of the light beam 23 and directs it to the key 21d causing the key to shine. The light beam 23 continues to propagate with a reduced width W2 towards a third mirror 29 separating a third portion 31 from the light beam and directing it to the key 21c. The remaining rest of the light beam 23 having a width W3 finally impinges on the forth mirror 32 and is reflected towards the key 21b.
To this extent, the backlight system has been described with reference to the right side of Fig. 2. A corresponding arrangement of a laser diode 22 and mirrors is arranged on the left side of the remote control to illuminate the keys 21f, 21g, 21a and 21b. The corresponding elements of the backlight system on both sides in Fig. 2 are indicated with the same reference numbers. Obviously, control key 21b is illuminated by two laser beams. This allows conferring the key 21b a different brightness or colour than the other keys. Different brightness of different keys can also be achieved by selecting the portion of the light beam 23 directed to one particular key to be different than to other keys.
In the described embodiments, the mirrors act as beam splitting elements being effective by reflection. However, it is also possible to use beam-splitting elements that partially reflect the incident lighting 23 and transmit the rest of the light beam. This can be achieved e.g. by transparent plastics or by a prism-like arrangement.

Claims

A control panel equipped with electronic circuitry comprising a signal emitter to send control signals, and with operating elements for inputting commands associated with control signals, the operating elements (21a - 21g) being translucent and illuminated by a light source characterized in that the light source is formed by a laser (22) emitting a light beam (23) and in that a beam splitter (24, 27, 29, 32) is provided separating a portion (26, 28, 31) of the light beam (23) emitted by the laser (22) and directing this portion to an operating element (21a - 21g).
A control panel according to claim 1 characterized in that a plurality of beam splitters (24, 27, 29, 32) is provided and each beam splitter being effective to separate a portion of the light beam (23) and to direct this portion to an operating element (21a - 21g).
A control panel according to claim 1 or 2 characterized in that the beam splitter(s) (24, 27, 29, 32) is (are) formed by a mirror (mirrors).
A control panel according to claim 1 or 2 characterized in that the beam splitter(s) is (are) formed by a semi-transparent element (semi-transparent elements).
A control panel according to claim 1 or 2 characterized in that the beam splitter(s) is (are) formed by a prism (prisms).
A control panel according to claim 2 characterized in that the beam splitters are arranged in a sequence along the progression direction of the light beam (23) emitted by the laser (22).
A control panel according to claim 2 characterized in that a plurality of lasers (22) is provided each having an associated beam splitter or an associated set of beam splitters (24, 27, 29, 32).
A remote control equipped with a control panel according to one of the preceding claims