Electric lamp and discharge devices: systems – High frequency starting operation for fluorescent lamp
Reexamination Certificate
2001-08-14
2003-12-16
Ho, Tan (Department: 2821)
Electric lamp and discharge devices: systems
High frequency starting operation for fluorescent lamp
C315S291000, C315S307000
Reexamination Certificate
active
06664735
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a lighting device provided with a lighting instrument with an incandescent lamp which is applied as a light source, and more particularly a dimmer for an incandescent lamp which is suitable for use in stage lighting or TV studio lighting.
2. Description of the Related Art
Although many lighting devices are used in the field of stage lighting or TV studio lighting and the like, a free adjustment of light for a light flux in the lighting equipment is an essential element and a smooth optical adjustment can be carried out, so that also at present, the lighting instrument with an incandescent lamp such as a halogen lamp which is applied as a light source is frequently used.
Optical adjustment of this incandescent lamp lighting device is carried out by controlling a phase angle of an electrical power supplied to the lighting instrument under application of a switching element such as a thyrister and the like.
However, it is well known in the art that when a voltage supplied to the incandescent lamp lighting equipment is controlled to perform an optical adjustment, a color temperature of the light flux generated by the incandescent bulb is substantially varied.
In particular, in the case of TV studio lighting using TV cameras, a variation in color temperature caused by optical adjustment may provide a substantial influence against image quality of TV screen image and this may provide a certain problem so that in order to solve this problem in the prior art, there have been provided some measures that a color filter is used at the lighting equipment to correct a color temperature, or in place of optical adjustment a radiating range angle of the lighting equipment is changed to adjust an illuminance at a lighted surface.
In general, it has been required that a light flux of the halogen lamp is proportional to a multiplication by 3.38 of a supplied voltage and a color temperature is proportional to a multiplication by 0.36 of a supplied voltage in reference to an experiment. Accordingly, a color temperature is proportional to a multiplication by 0.107 of a light flux.
For example, in the case that the halogen lamp with 3,200K at a rated voltage is used, optical adjustment of the light flux is performed to 50%, the color temperature is reduced down to 2,970K.
FIG. 1
is a graph showing a specific light flux against a color temperature in the prior art incandescent lighting equipment.
In regard to a less amount of variation in color temperature, although the prior art employed a system in which the reduction in color temperature is avoided by a correction measure with the color filter or adjustment of the lighting equipment as described above, both of them were troublesome measures and they were not necessarily a perfect measures.
In turn, in the gazette of Japanese Patent Publication No. Hei 8-1832 is proposed an optical adjustment method in which when a dimmer circuit is operated in a range of intensity of illumination between 0% and 50% of brightness, only one of a pair of silicon controlling rectifiers is turned on for a predetermined time period and the other silicon controlling rectifier is turned on from a starting point of ½ of an entire cycle to its end, and when the dimmer circuit is operated in a range of intensity of illuminance between 50% and 100% of brightness, the other silicon controlling rectifier circuit is turned on against a predetermined portion of the other half cycle, thereby a predetermined pulse duration period for controlling the intensity of illumination given by the lighting device is controlled, this proposal restricts an acoustic noise produced by the lighting device and the reduction in color temperature is not accommodated.
SUMMARY OF THE INVENTION
The present invention has been invented in reference to such circumstances as found in the prior art, and it is a first object of the present invention to provide a dimmer for an incandescent lamp in which the color temperature is raised fast even if the optical adjustment is carried out and the optical adjustment can be carried out with a less variation in color temperature.
In addition, it is a second object of the present invention to provide a dimmer for an incandescent lamp capable of adjusting light scarcely acknowledging a reduction in color temperature in which when a degree of adjustment of light is increased, the color temperature is maintained after the color temperature reaches the specified value.
In order to accomplish the aforesaid first object, the present invention provides a gist that a dimmer for performing one ignition for every one period of a power supply waveform is used, each of an electrical power of a positive half cycle and an electrical power of a negative half cycle is supplied to each of individual filaments of the bulb, a time of raising of the adjusted light at each of the filaments is displaced and a variation of the color temperature caused by the optical adjustment operation is reduced.
That is, a first aspect of the present invention consists in a dimmer for an incandescent lamp capable of adjusting light with a less variation in color temperature in which a phase angle controlling optical adjuster for performing one ignition operation every one period of the electrical power waveform is used and its ignition angle is changed continuously to perform an optical adjustment operation, each of the electrical power of positive half cycle and the electrical power of negative half cycle is supplied to each of the individual filaments.
In accordance with such means as described above, the electrical power of positive half cycle and the electrical power of negative half cycle are controlled continuously for optical adjustment, each of the electrical powers is supplied to individual filaments to cause one filament to be raised fast and the other filament to be raised in delay, resulting in that a variation in color temperature can be reduced remarkably when the optical adjustment is performed.
As an embodiment of the individual filaments in the aforesaid first aspect, it is possible to provide an embodiment in which the bulb having two filaments enclosed with an intermediate terminal installed in the same bulb is used.
In addition, a rated electrical power ratio of the two filaments enclosed in the aforesaid same bulb is changed to enable the characteristic in variation of color temperature to be optionally set.
As an embodiment of the individual filaments in the aforesaid first aspect, a plurality of bulbs are installed within the same lighting equipment, one bulb lit in optical adjustment in a positive half cycle and the other bulb lit in optical adjustment in a negative half cycle are discriminated to enable a similar effect to be attained. A plurality of bulbs defined in this case are two bulbs or more and they include both an even number and an odd number.
It is preferable that a rated electrical power ratio of a plurality of bulbs installed in the aforesaid same lighting equipment is changed.
As an embodiment of means for continuously changing an ignition angle of the phase angle controlling optical adjuster related to the aforesaid first aspect, it can be accomplished by arranging the optical adjustment controlling function signal generator forming the waveform synchronized with the power supply waveform and corresponded to one period of the power supply, a comparator and a switching element.
In order to accomplish the aforesaid second object, the present invention has a gist in which a dimmer capable of individually controlling the electrical power of positive half cycle and the electrical power of negative half cycle is used, each of the electrical power of positive half cycle and the electrical power of negative half cycle is supplied to each of the individual filaments of the bulbs, supplying of the electrical power in the second filament is started when the first filament while increasing the specific light flux reaches a specified color temperature (for example, 97% of the rated color
Kita Hiroshi
Tsuchizaki Kenichi
Dykema Gossett PLLC
Ho Tan
Marumo Electric Co., Ltd.
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