JPS61192157A - Lighting equipment - Google Patents

Abstract

PURPOSE:To give a preheating in a most appropriate condition following a surface temperature by detecting the surface temperature of a light source and controlling a preheating voltage responding the then temperature of the light source. CONSTITUTION:The surface temperature of a light source 1 is detected by a sensor 13 and the most appropriate preheating voltage value for the said temperature is selected automatically by a temperature-preheating voltage conversion table 15 and furhtermore, the preheating voltage is impressed on the light source 1 through a power supply 16 and a stabilizer 12.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a lighting device that can automatically control the preheating voltage of a light source that requires preheating.

<Prior Art> Conventionally, reading devices such as facsimile machines, printers, and electrophotographic copying machines illuminate a document with light from a fluorescent lamp, convert this reflected light into an electrical signal using a charging conversion element, and read the document.

The above-mentioned reading device such as a facsimile machine is used immediately after the fluorescent lamp is turned on, but the overall light amount of the fluorescent lamp fluctuates rapidly immediately after the fluorescent lamp is turned on. Therefore, in the past, in order to preheat fluorescent lamps to prevent sudden changes in light intensity and insufficient light intensity, and to make the light intensity distribution uniform in the length direction of fluorescent lamps, shading plates were designed according to the experimentally determined light intensity distribution. It was corrected by a correction mechanism such as.

<Problems to be Solved by the Invention> However, in the past, preheating was always performed at a constant level regardless of conditions such as temperature, which caused the problem of insufficient preheating at low temperatures.

Particularly at low temperatures of 5 degrees Celsius or below, the inside of a fluorescent lamp's tube is not sufficiently warmed up immediately after it is turned on, and the mercury inside the tube cannot be sufficiently vaporized, and furthermore, the vapor pressure of vaporized mercury is not sufficiently diffused inside the tube. Because the light is not progressing, not only the overall light intensity fluctuates, but also the light intensity distribution in the tube length direction changes rapidly for several minutes immediately after the light is turned on.

Therefore, at low temperatures, not only does the overall light intensity of a fluorescent lamp increase rapidly immediately after it is turned on, but also the light intensity distribution in the tube length direction fluctuates over time, causing it to no longer match the experimentally determined light intensity distribution. . For this reason, there was a problem in that the light intensity distribution in the tube length direction was not uniformly corrected, resulting in poor reading.

The present invention relates to a completely new technique developed to solve the above-mentioned conventional problems, and its purpose is to provide a lighting device that can control a preheating voltage in accordance with temperature changes of a light source.

Means for Solving the Problems> An embodiment for solving the above problems will be described using a facsimile machine as an example.

FIG. 1 is a block diagram showing the reading section of a facsimile machine, in which light emitted from a light source 1 made of a fluorescent lamp is reflected at a document reading point 2, and is converted into photoelectric material via several mirrors 3 and a lens 4. The signal reaches the circuit 5, is converted into an electrical signal by the circuit 5, and is amplified by the amplifier 6.

A part of the signal from the amplifier 6 is transmitted to a maximum value detection circuit 7, where the maximum value of the reflected light is detected, and a threshold value generation section 8 determines the slice level for recording.

The signal from the amplifier 6 is converted into a digital signal by an A/Df conversion circuit 9 in relation to the slice level, and is output from an output terminal 10 as an image signal.

Further, the light source 1 is configured to be controlled by a signal from a lighting control input terminal 11 via a high frequency ballast 12.

Furthermore, the surface temperature of the light source 1 is measured by a temperature sensor 13 serving as a temperature detection means, and the signal from the sensor 13 is converted into a digital signal by an A/D conversion circuit 14, and this signal is used as a temperature detection means constituting a preheating voltage determining means. - The preheating voltage is transmitted to the lighting and preheating power source 16 via the preheating voltage conversion table 15, and the preheating voltage of the light source 1 is controlled via the high frequency ballast 12.

Effect> To explain the preheating effect of the device configured as above, the surface temperature of the light source 1 is detected by the temperature sensor 13, and the optimum preheating voltage value for the detected temperature is automatically determined by the temperature-preheating voltage conversion table 15. The selected preheating voltage is then applied to the light source l via the power supply 16 and the ballast 12. Therefore, even if the surface temperature of the light source 1 becomes low, preheating in an optimal state is always provided by following the surface temperature at that time.

<Example> In the above-mentioned example, the signal of the temperature sensor 13 that detected the surface temperature of the light source l was converted into a digital signal by the A/D conversion circuit 14, but without converting it into a digital signal,
A configuration in which the signal of the temperature sensor 13 is amplified, the analog change is used as is, the preheating voltage to be applied is determined by a preheating voltage determining means such as a transistor, and the preheating voltage is controlled via the power source 16 and the stabilizer 12. It may be.

If the preheating voltage is controlled using an analog signal as described above, there is an advantage that the overall control mechanism becomes simple.

<Effects of the Invention> As described above, the present invention is configured to detect the surface temperature of the light source and control the preheating voltage of the light source according to the temperature at that time, so that the light intensity changes when the surface temperature is low. It is possible to apply precise preheating to a light source that produces . Even in reading devices such as facsimile machines that use a fluorescent lamp as a light source, it is possible to suppress irregularities in the light intensity distribution and sudden fluctuations in the light intensity due to insufficient preheating immediately after the light is turned on. It has features such as being able to prevent the blackening phenomenon that occurs when mercury vapor is applied to the inner wall of the lamp and combines with the phosphor.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating an embodiment of the present invention.

Claims (1)

[Claims] It has a light source that is electrically turned on, a temperature detection means that detects the temperature of the light source, a preheating voltage determining means that determines a preheating voltage according to the temperature of the light source, and a power source for preheating and lighting the light source, A lighting device characterized in that a signal from the temperature detecting means is fed back to a power source via a preheating voltage determining means to control a preheating voltage of the light source.