JPH02144888A - Illumination device - Google Patents

Abstract

PURPOSE:To have a desired amount of light emission accurately and precisely by furnishing a temp. controlling means, which performs heating and cooling of a light source in accordance with change in the light quantity from the light source. CONSTITUTION:A lightup means 6 to perform lighting-up of a fluorescent lamp 1 as a light source is connected with a timing generator 5, which sends sampling signals A, B at certain interval to appropriate sample holds 7, 8, and these are connected with a photo-diode 4 and a comparator 9, respectively, and signal from this comparator 9 changes over a switch 10 of a heater 3 from ON to OFF and vice versa so as to perform temp. control of fluorescent lamp 1. That is, either heating or cooling of this fluorescent lamp 1 is made according to change in the light quantity of the fluorescent lamp 1. This accomplishes accurate control of the metal vapor pressure to put into the condition with high light emitting efficiency, and thus the desired light quantity can be obtained.

Description

[Detailed description of the invention] (Industrial application field) The present invention can be applied to, for example, a copying machine or a facsimile machine.

The present invention relates to lighting devices that can be used in printers and the like, and particularly to lighting devices equipped with temperature-controllable light sources.

(Prior Art) In recent years, various information systems have been developed with the rapid development of the information industry, and many of these systems are equipped with lighting devices that use low-pressure mercury lamps such as fluorescent lamps as light sources. . For example, copying machines and facsimile machines are provided with a document illumination device, and liquid crystal printers are provided with an exposure device.

By the way, since the luminous efficiency of low-pressure mercury lamps changes depending on the mercury vapor pressure inside the tube, the temperature of the light source has traditionally been controlled in various ways.For example, fluorescent lamps used for indoor lighting, etc. When the light source is turned on, the temperature is set so that the mercury vapor pressure in an equilibrium state between the heat generated by the input energy and the heat dissipated by the light source is an appropriate value.

In this case, the above method has the disadvantage that the mercury vapor pressure in the equilibrium state changes depending on the environmental temperature of the light source.

In addition, since it takes a long time to reach the above equilibrium state, conventionally a temperature detection means is provided on the tube surface of the light source, and depending on the temperature detected by the temperature detection means, heating is performed with a heater or with a fan. Devices have been devised to provide cooling.

(Problem II to be solved by the invention) However, in such a conventional example, the temperature distribution on the tube surface of the light source changes with changes in the environmental temperature and the passage of time, so an appropriate detected temperature cannot be obtained. There was a drawback that it was difficult to provide the temperature detection means at a certain location.

In addition, 1. In normal cases, there is a difference between the internal temperature of the light source and the surface temperature of the light source, which should be used as a standard. The disadvantage was that it could not be done.

When the above-mentioned illumination device is applied to a copying machine, etc., the amount of light is unstable until the light source reaches an equilibrium state, resulting in uneven density in one image. In order to avoid this, there is a problem in that the so-called warm-up time becomes long. Furthermore, in the conventional example described above, since the amount of light emitted from the light source is adjusted only by temperature control, it takes time to obtain the desired amount of light emitted, and this also reduces the warm-up time of the device. The problem was that it was too long.

Therefore, the present invention has been made to solve the problems of the prior art described above, and its purpose is to accurately and quickly obtain a desired amount of light emission by accurately controlling the temperature of the light source. The objective is to provide a possible lighting device.

(Means for Solving the Problems) In order to achieve the above object, the present invention involves generating a discharge in metal vapor to excite metal atoms, and causing a transition from this excited state to a lower energy state. The illumination device includes a light source that generates light according to the present invention, and is characterized by being provided with temperature control means that heats or cools the light source in accordance with changes in the amount of light from the light source.

(Function) The luminous efficiency of the light source of the present invention having the above configuration varies greatly depending on the metal vapor pressure, which changes with the temperature of the light source. In this case, the luminous efficiency is maximum at a given metal vapor pressure and tends to decrease regardless of whether the vapor pressure is high or low (see Figure 3 below), but the value at which the vapor pressure is maximum If the vapor pressure is lower than this maximum value, the light intensity of the light source decreases with time, while if the vapor pressure is higher than this maximum value, the light intensity of the light source increases with time.

If the light source is heated or cooled according to changes in the light intensity of the light source as in the present invention, the temperature of the light source, that is, the metal vapor pressure, can be accurately controlled. A desired amount of light can be obtained with high luminous efficiency.

(Example) Hereinafter, the present invention will be explained based on illustrated embodiments.

Figures 1rl11 to 5 show an embodiment of the lighting device according to the present invention, and Figure 2 shows its appearance. A resin-type heater 3 with a nichrome wire 2 stretched around it is wound around it, and by passing a current through the nichrome wire 2, the fluorescent lamp 1 is heated. Here, an opening (not shown) is formed in this heater 3, and a photodiode 4 as a light amount detection means, which will be described later, is disposed at a position facing the opening, and a fluorescent lamp is connected to the heater 3. The configuration is such that the amount of light emitted from the sensor is detected.

FIG. 1 is a block diagram showing the control system of this embodiment.

As shown in the figure, lighting means 6 for lighting the fluorescent lamp 1 is connected to a timing generator 5 for sending sampling signals A and B at predetermined intervals to corresponding sample holds 7.8. The sample hold 7.8 is connected to the photodiode 4 and the comparator 9, respectively, and the switch 10 of the heater 3 is turned ON and OFF based on the signal from the comparator 9, thereby controlling the temperature of the fluorescent lamp 1. This is a configuration for controlling.

By the way, for light sources that generate light by generating a discharge in metal vapor to excite metal atoms and making a transition from this excited state to a lower energy state, the luminous efficiency differs depending on the metal vapor pressure. There is a phenomenon called. Among such light sources, for example, a low-pressure mercury lamp uses mercury as a metal, and generates light (ultraviolet rays) with a wavelength of 253.7 nm through energy transition to mercury atoms.Furthermore, in the case of a fluorescent lamp, This ultraviolet light is irradiated onto a phosphor provided on the inner surface of the tube to obtain fluorescence from the phosphor.

Therefore, in the case of a low-pressure mercury lamp or a fluorescent lamp, the luminous efficiency of the light source depends on the vapor pressure of mercury, and its value varies greatly as shown in FIG. In this case, the luminous efficiency of the light source reaches its maximum when the value of mercury vapor pressure is approximately 10 mmH, so it is desirable to emit light from a fluorescent lamp or a low-pressure mercury lamp under a vapor pressure close to this value. In this embodiment, as in the conventional example, the mercury vapor pressure inside the tube in an equilibrium state is configured to be the above value.

Furthermore, in this embodiment, the temperature of the fluorescent lamp l is controlled based on the signal obtained from the photodiode 4, and the amount of light emitted from the fluorescent lamp l is as shown in FIG. 10
-1 mHg is the maximum value, and the vapor pressure decreases whether it is lower or higher than that value, so simply detecting the amount of light emitted will not tell you whether the mercury vapor pressure is too high or too low even if the amount of light decreases. It is unknown.

However, when such a light source is operated on and off, when the mercury vapor pressure is lower than the appropriate value, the subsequent light intensity decreases compared to the initial light intensity of one light, and conversely, when the mercury vapor pressure is higher than the appropriate value, It has the characteristic of improving the amount of light.

Therefore, in this embodiment, the temperature of the fluorescent lamp 1 is controlled by the following procedure.

First, when the power switch (not shown) is turned on, the timing generator 5 outputs a lighting signal at regular intervals as shown in FIG. 4, and the lighting means 6 is driven at the rHighJ timing of this signal. Turn on fluorescent lamp 1. The photodiode 4 detects the amount of light emitted from the fluorescent lamp 1, and sends a signal corresponding to the amount of light emitted to each sample hold 7.
．． Send on 8th. Here, from the timing generator 5,
As shown in FIG. 4, while the fluorescent lamp 1 is on, sampling signals A and B are output at regular intervals with shifted timing, and each signal A and B is sent to a sample hold 7.8. In hold 7.8, at the rHighJ timing of each sampling signal A, B,
Sample and hold the light emission amount signal inputted from the photon x, -+-''4.

The sampled and held signals are input to the comparator 9, and the sampled signal A is input to the comparator 9.
When the signal from the sample hold 7 corresponding to the sampling signal B is larger than the signal from the sample hold 8 corresponding to the sampling signal B, the switch 1O is closed, and when the signal is smaller than the signal B, the switch 1O is controlled to be opened.

FIG. 5 shows the output signal of the photodiode 4.
Figure (a) shows when the temperature of fluorescent lamp 1 is lower than the appropriate value (mercury vapor pressure is low), Figure (b) shows when the same temperature is appropriate, and Figure (C) shows when the same temperature is appropriate. The cases where the mercury vapor pressure is higher than the value (higher mercury vapor pressure) are shown. As can be understood from the figure, when the temperature of the fluorescent lamp 1 is low, the amount of light in the early stage of one lighting is greater than the amount of light in the later stage of lighting, and on the other hand, when the temperature of the fluorescent lamp 1 is high, the amount of light is less. .

Therefore, in this embodiment, when it is determined that the temperature of the fluorescent lamp 1 is low based on the signal obtained from the photodiode 4, the switch 10 is turned ON to supply current to the heater 3, and the fluorescent lamp 1 is turned on. Heat the lamp. On the other hand, when it is determined that the temperature of the fluorescent lamp l is high, the switch lO is turned off to prevent current from flowing through the heater 3, and the fluorescent lamp l is cooled by natural heat radiation. It becomes possible to control the temperature to an appropriate temperature.

In this way, in this embodiment, temperature control is performed based on the light intensity of the fluorescent lamp l, so that more accurate temperature control can be performed than in the conventional example.

It becomes possible to reliably obtain the desired amount of light. Therefore, if this embodiment is applied to an exposure system such as a copying machine, a stable image without density unevenness can be quickly obtained.

FIG. 6 shows another embodiment of the lighting device according to the present invention. The same parts as in the previous embodiment are given the same reference numerals, and the description will be made as follows: 1. In this embodiment, the tube current flowing through the fluorescent lamp 1 is increased or decreased based on the amount of light from the fluorescent lamp 1 obtained by the photodiode 4. Furthermore, a fan 11 is provided to cool the fluorescent lamp 1 based on the detected temperature signal from the comparator 9.

between the photodiode 4 and the lighting means 6.

Average value detector 12. An inverter 13 and a clamp device 14 are connected respectively. The average value detector 12 is.

- It is composed of a second-order delay circuit and outputs the average value of the signal of the photodiode 4. Then, this average value signal is sent to the inverter 1.
3, and is supplied to the lighting means 6 via the clamp device 14 in order to prevent overcurrent from flowing into the fluorescent lamp 1. That is, with this configuration, when the amount of light emitted from the fluorescent lamp l is insufficient, it is possible to correct it to an appropriate value.

In this case, if the tube current is increased to increase the amount of light emitted by the fluorescent lamp 1, the self-heating of the fluorescent lamp 1 will increase, causing its temperature to rise too much above the appropriate value. In order to prevent this, in this embodiment, a timing generator 5.
If the sample hold 7.8 and the comparator 9 determine that the temperature of the fluorescent lamp 1 is high, the fan 11 is driven to cool the fluorescent lamp 1. Then, the tube current is controlled so that the amount of light from the fluorescent lamp l is constant. Note that if it is determined that the temperature of the fluorescent lamp 1 is lower than a predetermined value, the fan 11 is stopped.

In this embodiment having the above configuration and operation, even when the temperature of the fluorescent lamp 1 is low and the luminous efficiency is low, it is possible to obtain the same amount of light as when the temperature is appropriate, and the desired amount of light can be obtained more quickly. It is possible to obtain the amount of light. Therefore, when applied to a copying machine or the like, there is an effect that the warm-up time of the apparatus can be further shortened. Note that the other configurations and functions are the same as those of the previous embodiment, so their explanation will be omitted.

(Effects of the Invention) As described above, the present invention provides a temperature control means that heats or cools the light source according to changes in the light intensity of the light source, so it is possible to achieve more accurate temperature control than conventional devices. It becomes possible to perform control, and as a result, a desired amount of light can be quickly obtained at the time of starting up the device, etc.

Furthermore, if the energy input to the light source is controlled by M based on changes in the light intensity of the light source, even if the temperature of the light source is low and the luminous efficiency is low, for example, the tube current can be increased to This makes it possible to instantly obtain the same amount of light.

Furthermore, if the illumination device according to the present invention is used as a light source for reading manuscripts in copying machines and facsimile machines, or as a light source in LC printers, stable images without density unevenness can be obtained.
It also has the effect of shortening the warm-up time of the device.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an embodiment of the lighting device according to the present invention, Fig. 2 is a perspective view showing the external appearance of the same embodiment, and Fig. 3 shows the relationship between mercury vapor pressure and relative luminous efficiency. graph, 4th
The figure is a time chart showing the temperature control operation of the device shown in Fig. 1, and Fig. 5 is a graph showing the output signal of the photodiode.
FIG. 6 is a schematic configuration diagram showing another embodiment of the present invention. Explanation of symbols 1... Fluorescent lamp (light source) 2... Nichrome wire 3...
・Heater 4...Photodiode 5...
・Timing generator 6...Lighting means 7.8...Sample hold

Claims (4)

[Claims] (1) In a lighting device equipped with a light source that generates light by generating a discharge in metal vapor to excite metal atoms and making a transition from this excited state to a lower energy state, the illumination device may be configured to: 1. A lighting device comprising temperature control means for heating or cooling the light source. (2) The light source is blinked and the light amount A at the initial stage of lighting and the subsequent light amount B are detected, and when the light amount A is greater than the light amount B, the light source is heated, and when the light amount A is less than the light amount B, the light source is heated. 2. The lighting device according to claim 1, wherein the lighting device cools the light source. (3) The lighting device according to claim 1 or 2, characterized in that the method of heating the light source uses heat generated by the light source itself. (4) The lighting device according to any one of claims 1 to 3, further comprising means for controlling energy input to the light source.