Device for generating light signals

• US 20020113561A1
• Filed: 12/13/2001
• Published: 08/22/2002
• Est. Priority Date: 12/18/2000
• Status: Active Grant

• Current Assignee: Bayer AG
• Original Assignee: Bayer AG
• Inventors: Neigl, Ralf, Berneth, Horst, Jacobsen, Wolfgang
• Granted Patent: US 6,731,433 B2
• Time in Patent Office: Days
• US Class Current: 315/363
• CPC Class Codes: F21V 14/003 by interposition of elements with electrically controlled variable light transmissivity, e.g. liquid crystal elements or electrochromic devices
• CPC Class Codes: F21V 23/0442 activated by means of a sensor, e.g. motion or photodetectors
• CPC Class Codes: F21V 9/40 with provision for controlling spectral properties, e.g. colour, or intensity
• CPC Class Codes: F21W 2111/02 for roads, paths or the like
• CPC Class Codes: G08G 1/095 Traffic lights

Abstract

The present invention relates to a device for generating light signals, in particular traffic lights. The device according to the invention contains a housing with at least one opening, which is closed by a plate, the absorption of which can be controlled electrically, there being located in the interior of the housing behind the opening a diffuser element, which reflects incident light through the plate. Preferred switched states of the plate are either black (absorption over the entire spectral region of visible light) and colored transparent (slight absorption in specific spectral regions) or transparent (no absorption over the entire spectral region of visible light). The device according to the invention is used to generate light signals by virtue of the fact that the ambient light strikes the plate and, depending on switched state, is absorbed entirely, partially or not at all by the plate. The light fraction transmitted through the plate is reflected by the diffuser plate located behind the plate and transmitted a second time through the plate, and can then be perceived from outside.

Claims

1. A device for generating light signals comprising:

(a) a housing having an interior and at least one opening,

(b) at least one plate having an absorption that is electrically controllable and closing the at least one opening, and

(c) a diffuser element for reflecting incident light through the plate and located in the interior of the housing behind the at least one opening.

2. The device according to claim 1, wherein the housing has three round openings arranged one above another and each of which is, respectively, closed by a plate, so that it is possible for each plate to be switched electronically between the switched states of colored transparent and black, and the absorption spectrum of the uppermost plate permits only transmission of red light, the middle plate permitting only the transmission of red and green light and the lower plate permitting only the transmission of green light.

3. The device according to claim 2, wherein at least one switchable active light source is arranged in the housing for each plate and the source illuminates the plate from inside.

4. The device according to claim 3, wherein the active light source is arranged behind the diffuser element when seen from the plate outwards.

5. The device according to claim 4, wherein the diffuser element has a transmittance in the range from about 5% to about 30%.

6. The device according to claim 1, wherein filter discs are arranged in, or outside on, the housing in the beam path of the light, and the absorption spectrum of the plates is selected such that, in the switched state of low absorption, the absorption of the plate is as low as possible in the transmission range of the filter disc, and in the switched state of high absorption, the absorption in the transmission range of the filter disc is above 70%, referred to the quantity of incident light.

7. The device according to claim 1, wherein one or more photoreceivers are arranged in the interior of the housing such that they detect a portion of the ambient light incident through the plate

8. The device according to claim 1, wherein the reflectance of the diffuser element, which is arranged in the interior of the housing, is above 30% of the quantity of light incident on the diffuser element.

9. The device according to claim 1, wherein the reflection at the diffuser element is partially retroreflective.

10. The device according to claim 9, wherein, the retroreflective component of the light reflected by the diffuser element is higher than 5%.

11. The device according to claim 9, wherein a component of at least 20%, with particular preference in the range from 30% to 70% of the light reflected by the diffuser element is diffusely reflected.

12. The device according to claim 1, wherein an additional diffuser element is fitted on the outside of the housing in front of the plate or plates.

13. The device according to claim 12, wherein the diffuser element is a glass plate which is coated with a layer which is strongly scattering and weakly absorbing.

14. The device according to claim 1 wherein the electric switched states of the plate are either black or colored transparent or transparent and colored transparent.

15. The device according to claim 1, wherein the housing is colored differently outside, at least in the region around the openings, from the plates in their switched states, and optionally in black or white.

16. The device according to claim 15, wherein the surrounding surface of the opening is white when one of the switched states of the associated plate is black, and in that the surrounding surface of the opening is black when one of the switched states of the plates is transparent.

17. The device according to claim 3, wherein the device is connected to a control unit, and this control unit switches off or switches in the active light source for the duration of the optically transparent state as a function of whether one or more signals measured with the aid of the photodetector in a prescribed time interval t after switching of the plate to an optically transparent state overshoots or undershoots a prescribed threshold value.

18. The device according to claim 17, wherein the prescribed time interval t is at most 1 second.

19. The device according to claim 17, wherein the device is connected to a control unit, and this control unit outputs an alarm signal when the ratio of the signals measured with the aid of one or more photoreceivers in the state of low and high absorption lies below a prescribed value.

20. The device according to claim 19, wherein use is made of a photoreceiver unit which detects only in a narrow spectral region, in which the characteristic color of the plates lies.

21. The device according to claim 1, wherein the plate or plurality of plates is/are electrochromic devices.

22. The device according to claim 21, wherein the electrochromic device comprises a pair of transparent glass or plastic discs which are provided in each case on one side with an electrically conductive, transparent coating and which are joined via a sealing ring on the sides of their conductive coating, and in the case of which the volume formed from the two discs and the sealing ring is filled with an electrochromic medium.

23. The device according to claim 22, wherein the electrochromic medium is a liquid, a gel or a polymer.

24. The device according to claim 23, wherein the electrochromic medium contains at least one pair of electrochromic and oxidizable or reducible substances OX₂ and RED₁.

25. The device according to claim 24, wherein an electrochromic medium is used wherein

a) the reducible substance has at least one or at least two chemically reversible reduction waves in the cyclic voltammogram, and the oxidizable substance correspondingly has at least one or at least two chemically reversible oxidation waves, or

b) the reducible substance and the oxidizable substance are bonded to one another covalently via a bridge or

c) the reducible and/or oxidizable substances are selected as those in which the reversible transition between the oxidizable form and the reducible form, or vice versa, is associated with the rupture or formation of a σ

bond, or

d) the reducible substance and/or the oxidizable substance are/is metal salts or metal complexes from those metals which exist in at least two oxidation stages, or

e) the reducible substance and/or the oxidizable substance are/is oligomers and polymers which contain at least one of the said redox systems, or pairs of such redox systems such as are defined under a) to d), or

f) mixtures of the substances described in a) to e) are used as reducible and/or oxidizable substance, assuming that these mixtures contain at least one reducible and at least one oxidizable redox system.