Patent Application
20080061712
The invention will now be elucidated in further detail, with reference to the drawings that show exemplary embodiments, and in which:
a through 3c diagrammatically show three different sensor arrangements for a device according to the invention; and
a and 4b diagrammatically show two different group sensor arrangements for a device according to the invention.
In
A light generating device, or lighting device proper, comprises a lamp housing 10, and three groups 11A through 11C of three fluorescent lamps 12 each. Each group comprises one group sensor, 13A through 13C, respectively.
The control device 1 comprises a power unit 3, which may be any device suitable for operating the lamps used in the lighting device proper, such as batteries with an optional transformer, a generator or simply a connector to mains power. The power unit 3 is connected to a power control unit 4, which controls the power actually delivered to the lamps 12 of the lighting device proper. The power unit 3 may for example be a simple potentiometer or other device for manually adjusting the delivered power, based on a measurement by a sensor. However, it will often comprise circuitry such as a printed circuit board or one or more ICs for automated control of the supplied power. The power control will often regulate the current supplied to the lamps, although in some cases a voltage or combination of voltage and current will be controlled. The power control unit 4 receives measured information, on which the control is to be based, from one or more sensors, which will be discussed hereinbelow. This measured information is processed by the control device, which may comprise a (micro)computer or other suitable circuitry, and may be compared or related to stored information in the information retrieval system 5. The latter may be a look-up table, such as on a memory chip, a CD, a diskette, or in dynamic memory etc. The stored information may e.g. comprise known data on measured relationships between various lamp parameters, such as intensity as a function of lamp current and lamp voltage, or lamp temperature, etc.
The lighting device proper comprises a lamp housing 10. This lamp housing 10 may comprise just a holder or similar structure for holding the lamps in a fixed position with respect to each other, or e.g. a box which is closed on all sides, except a light emitting side, which may alternatively be closed but optically transparent. The lamp housing 10 may be made of any suitable material or combination of materials, such as metal, plastics, glass etc.
The lighting device as shown in
It is to be noted that the number of groups as well as the total number of lamps is at least two, and the subdivision of all the lamps present in the device into groups of lamps is based on the idea of controlling the operation of at least one lamp with respect to the operation of at least one other lamp, based on measurements via one or more sensors. Hence it is always possible to indicate two or more groups in the device, without any requirement of there being a specific physical separation between the groups. However, since lamp control of each group should be possible separately, it will be possible to characterize the groups based on the control circuitry and the distribution of the lamps over the various branches of the operation control circuit.
Note furthermore that the distribution of lamps over the groups is not limited to neighboring lamps. It is likewise possible, and sometimes preferable, to combine the lamps in a symmetrical fashion, such as the two outermost lamps in one group, the two inner neighbors thereof in a second group, etc. If the whole device is symmetrical, then at least with respect to some parameters, such as temperature inside the lamp housing 10, a symmetrical behavior may be expected. This subsequently allows a simpler design, since only half the number of sensors to measure that symmetrical parameter is needed.
The fluorescent lamps 12 may be any type of fluorescent lamp containing mercury, such as hot cathode fluorescent lamps, cold cathode fluorescent lamps, or even cathodeless fluorescent lamps which are powered through electromagnetic fields. Any desired length, power or lamp color is allowed. Even simple UVC lamps, that do not contain a fluorescent pigment and hence are not fluorescent lamps in a literal sense, may be applied in the device according to the invention.
In
The group sensors 13 are connected to the control device 1, and to the power control unit 4 in particular, which may thus control and adjust the power supplied to the lamps or groups of lamps, based on a measurement signal supplied by the group sensors. Note that instead of a group sensor 13, it is also possible to use one or more sensor devices that are able to selectively supply a signal indicative for individual lamp intensity, e.g. by providing a movable sensor device. Alternatively, it is possible to provide each individual lamp with one or more sensors that are fixedly disposed therewith.
It is moreover possible to supply more than one sensor per group of lamps or even per individual lamp. This may comprise more than one sensor of the same type, such as an optical sensor. In this way, an even more reliable measurement may be made, since not only is there a back-up possibility in case one sensor is malfunctioning, but it is also possible to average the measurements of the sensors. Furthermore it is possible to provide more than one type of sensor, such as a temperature sensor and an optical sensor, or a voltage meter and a current meter.
A display housing 20 contains lamps 12, behind which a reflector 21 is disposed. An optional fan 22 controls the internal environment inside the display housing 20.
First sensors 23 and second sensors 24 provide measurements of the intensity of the lamps, the sensors and the lamps being connected to a control device 1.
A diffuser 25 diffuses the light emitted by the lamps, that will back-light a liquid crystal display (LCD) 26, which is controlled by a LCD control device 27.
The display housing 20 may again be made of any suitable material, and may for example be a display device for a computer, a television set, etc.
In this case 6 fluorescent lamps are provided, which number may, however, be any natural number larger than 1. The lamps 12 are provided in front of a reflector 21, to concentrate the emitted light in a forward direction, towards the LCD 26. It is also possible to use lamps 12 with a built-in reflector. In that case, no reflector 21 is needed. Note that a lamp housing is not shown in any detail.
First sensors 23 and second sensors 24, in each case only three of which are shown, are provided to measure a parameter that relates to the intensity, e.g. intensity itself, or temperature of a lamp envelope. First sensors 23 may provide individualized measurements for each lamp, while second sensors 24 may provide measurements that relate to e.g. an intensity which is averaged over a group of lamps.
The second sensors 24 are shown provided against a diffuser 25, which diffuses the light before it reaches an LCD 26. It is only at the level of the LCD where the light should be optimally diffused, e.g. diffuse within 0.1% over 1 cm, or any other desired criterion. The light provided serves as a back-light for the LCD, and by blocking unwanted radiation, an image is formed.
The LCD itself is controlled by a LCD control unit 27, which may optionally be connected to the control device 1. This may e.g. be useful in that the measurements by the sensors 23 and 24 provide information on the color temperature of the light of the lamps, which is a.o. temperature dependent. Based on this information, the LCD control unit 27 may adjust the control of the LCD, in order to correct for any shift in color temperature. Moreover, the speed of the LCD may also depend on temperature, which may be one of the parameters measured by the sensors. Based on this information, the control speed of the LCD may be adjusted.
In this case, the control device 1 and the LCD control device 27 are shown to be separate from the display housing 20. It is also possible to integrate one or both of the devices 1 and 27 into the display housing.
a through 3c diagrammatically show three different sensor arrangements for a device according to the invention.
a shows a fluorescent lamp with a lamp envelope 30, a first connector or lamp base 31, and a second connector or lamp base 32. A temperature sensor is denoted with reference numeral 33.
In use, the lamp bases 31 and 32 are connected to power lines. Note that in these and the following Figures, the lamp bases are shown with only pin each, as is the case for e.g. cold cathode fluorescent lamps. In the case of hot cathode fluorescent lamps, each lamp base would have two pins, which are connected to a filament electrode, and which would carry heater current for heating the filament electrode. Since this is irrelevant for the present invention, the drawings only show one pin, without the invention being limited thereto. Note that a side elevation view of a double-pin lamp base would also show only one pin.
The temperature sensor 33 is disposed in good thermal contact with the lamp envelope 30, and connected to a control device (not shown). The sensor is disposed at a position where the temperature of the envelope is lowest. This temperate determines the mercury vapor pressure, which in turn determines the light output/luminous efficacy. Since the light output as a function of coldest-spot temperature is known in the art, and may be determined on a lamp-to-lamp basis for even more precision, such a temperature measurement may suffice to determine the light output, and thus to provide a signal with which to correct deviations from one lamp to another.
In almost all cases, the coldest spot will be very near a lamp base of the fluorescent lamp, as shown. More particular, in the case where the electrode stems of the lamp are different, it is the long stem end of the envelope which has the lowest temperature. However, in some cases, such as with internal convection forced ventilation, reduced power input etc., as discussed above, the coldest spot may be located differently, and some gauge measurement may be required. In particular for the last two cases, the invention provides advantages, in that otherwise these cooling air currents might cool the lamp envelope to a different lowest temperatures, such that an inhomogeneous back-lighting arises. By determining the light output through measuring the temperature or other parameter, this effect may be corrected by increasing the power supplied to the lamp.
b shows a fluorescent lamp with a lamp envelope 30 and an optical sensor 34. Optical sensor 34 measures directly the optical intensity of the lamp. Thereto the sensor 34 is connected to the control device (not shown here) and may be provided in a position where it will hardly or not at all throw a visible shadow, e.g. at the back of the lamp, as seen from the direction of the LCD. Note that the sensor need not be at a position of maximum intensity, as long as the maximum intensity can be calculated form the measurement. In that way, measurements from different sensors may be compared. If desired, more than one optical sensor may be provided, to determine an average light output value for the lamp.
c shows a lamp envelope 30, with first and second lamp bases 31 and 32, respectively, across which a voltage meter 35 is connected. A current meter 36 is connected in series with the lamp. Both meters 35 and 36 are connected to the control device (not shown).
In use, the voltage meter 35 measures the lamp voltage, and the current meter 36 measures the lamp current. In case the lamps are operated with a preset lamp current or lamp voltage, the corresponding meter may of course be dispensed with, because the relevant value is already known. For fluorescent lamps, the relationship of the lamp voltage V, the lamp current I and the envelope temperature T are known, or may be determined on a lamp-to-lamp basis for even more accuracy. It is also possible to actively measure the lamp voltage when the lamp is “off” or in a low power state, e.g. between power pulses, at a lamp current of 1 mA, or a few mA. This does not disturb normal lamp operation.
With the measured values, a look-up table or the like may be employed by the control unit or a lamp operator to determine the light output of the lamps, and adjust lamp power through adjusting the current I, if necessary.
Other known devices to determine the light output may also be contemplated, as long as they provide information, on the basis of which the operation of the relevant lamps may be controlled.
a and 4b diagrammatically show two different sensor device arrangements for a device according to the invention.
Herein, 40 denotes a first fluorescent lamp, and 41 denotes a second fluorescent lamp. A movable optical sensor device is denoted with 42 and has a viewing window that subtends a solid angle a. The sensor device 42 is connected to the control device (not shown).
The movable sensor device 42 is rotatable around some axis, in the direction of arrow B, such that, in a first position, the sensor device 42 is able to measure the intensity of the first lamp 40, and in a second position, the intensity of the second lamp 41. Due to the viewing window of the sensor device 42, the measurements are substantially independent, and do not influence each other.
The sensor device 42 is a first example of a single sensor that is able to provide measurements for each group of lamps. In this case there are two groups of one lamp each. Of course, any other number of lamps or groups could be provided as well, as long as the movable sensor device is able to measure the desired lamps, e.g. through correspondingly narrowing the viewing window or otherwise.
b shows an alternative sensor device arrangement. Herein, 40 and 41 denote a first and second fluorescent lamp, respectively. A movable voltmeter 43 is connectable to first connections 44 across first lamp 40, and to second connections 45 across second lamp 41, by moving in the direction of arrow C. The movable voltmeter 43 is connected to the control device (not shown).
The movable voltmeter 43 is a sensor device that is able to measure more than one lamp (group). The number of measurable lamps or groups of lamps may be increased by suitably providing the connections therefore. Instead of providing a movable voltmeter, it is of course also possible to provide suitable circuitry to connect the voltmeter to the relevant connections with the lamps which should be measured.
| Number | Date | Country | Kind |
|---|---|---|---|
| 04103471.1 | Jul 2004 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB05/52354 | 7/15/2005 | WO | 00 | 1/17/2007 |
