JPS63246968A - Original reader - Google Patents

Abstract

PURPOSE:To contrive to reduce the preheat time of a fluorescent light by comparing the output of a temperature detection element and outputs of the 1st and 2nd reference voltage sources respectively so as to control the lighting of a light source, thereby applying accurate color separation. CONSTITUTION:A self control heat element 5 is used for preheating normally and a tube wall temperature of light source is detected by a temperature detection element 6 just before the reading and when the tube wall temperature of the light source is lower than a prescribed temperature range, the light source is lighted. Then the preheating by the self control heat element 5 and the fluorescent light itself is applied and after it is discriminated that the temperature reaches within a prescribed temperature range by the temperature detection element 6 to start the read. When the tube wall temperature of the light source is higher than the prescribed temperature range, it is awaited that the temperature reaches a prescribed temperature range, and the light source is lighted after the temperature detection element 6 detects the arrival of prescribed temperature range, and the light source is lighted to start reading. The preheat time of the fluorescent light is reduced and the fluorescent light is used at a temperature range with excellent light efficiency to attain accurate color separation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a document reading device that optically reads a document image, and more particularly to a temperature control device for a light source thereof.

2. Description of the Related Art Fluorescent lamps have been widely used as light sources in document reading devices that optically read document images.

In general, fluorescent lamps have the property that their spectral distribution (emission spectrum) characteristics change depending on the mercury vapor pressure.

When the temperature of the tube wall of a fluorescent lamp is low, the mercury vapor pressure is low, and the spectral distribution of the fluorescent lamp does not show the standard spectral distribution characteristics as shown in Part 31 To+, but instead has a spectral distribution with a lot of infrared light as shown in Part 3. As a result, in color document reading devices that separate color documents into red, green, and blue light and read them, accurate color separation is not possible, and the photoelectric conversion elements are also adversely affected. As shown in Figure 4, the luminous efficiency of a fluorescent lamp changes depending on the temperature of the tube wall, and if the tube wall temperature is too low or too high, the amount of light will be insufficient, which will adversely affect reading even when reading black and white originals. In order to solve this problem, a device (for example, Japanese Patent Laid-Open No. 61-801
No. 946), and a device in which a self-regulating heating element is attached to a fluorescent lamp as a preheating heater (for example, Japanese Patent Laid-Open No. 61-14
4964 (Japanese Patent Publication No. 154358/1983), and a method of providing a heat insulating heater around a fluorescent lamp and controlling the energization of the heat insulating heater to a temperature at which the luminous efficiency of the fluorescent lamp is maximized (for example, Japanese Patent Application Laid-open No. 154358/1982). There is.

Problems to be Solved by the Invention If the fluorescent lamp is turned on before reading the document, the temperature of the light source will rise more than necessary during continuous reading.
The luminous efficiency of the fluorescent lamp will deteriorate, which will have a negative effect on reading.Also, if the fluorescent lamp is preheated only by the self-regulating heating element, the response of the self-regulating heating element will decrease when the fluorescent lamp is cold, such as when the power is turned on. Because of the time, preheating takes time (Figure 5). A device that installs a heat-retaining heater around a fluorescent lamp and controls the energization of the heat-retaining heater to a temperature that maximizes the luminous efficiency of the fluorescent lamp requires a device that controls the amount of current applied to the heat-retaining heater.
This poses problems in terms of miniaturization and economy.

Means for Solving the Problems In order to solve the above problems, the present invention provides a light source for illuminating a document, a photoelectric conversion element for receiving reflected light from the document and converting it into an electrical signal, and a tube for the light source. Compare the self-regulating heating element and temperature detection element attached to the wall, the first and second reference voltage sources, and the output of the temperature detection element and the output of the first and second reference voltage sources, respectively. and a light source lighting control means for controlling lighting of the light source based on the outputs of the first and second comparators.

Function The present invention uses the above-mentioned means to constantly preheat with a self-regulating heating element, detect the temperature of the tube wall of the light source with a temperature detection element (for example, a thermistor) immediately before reading, and determine the temperature of the tube wall of the light source. When the temperature is lower than a predetermined temperature range, the light source is turned on, the self-regulating heating element and the fluorescent lamp itself preheat it, and the temperature detection element detects that the temperature has fallen within the predetermined temperature range before reading begins. .

Also, if the tube wall temperature of the light source is higher than a predetermined temperature range, the system waits until it reaches the predetermined temperature range, and after the temperature detection element detects that the temperature has reached the predetermined temperature range, the light source is turned on and reading begins. .

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a diagram for explaining the operation of one embodiment of the present invention.

In FIG. 1, 1 is a document, 2 is a fluorescent lamp that is a light source for illuminating the document 1, 3 is a lens that forms an image of the document on a photoelectric conversion element 4, 5 is a self-control heating element, and 6 is a thermistor, etc., for example. The temperature detection element 7 is lower than the tube wall temperature (T degree in FIG. 4, hereinafter referred to as T degree) at which the amount of light emitted from the light source 2 is maximum, and the amount of light emitted from the light source 2 is 80% of the maximum amount of light emitted.
(When the tube wall temperature is TL degrees in FIG. 4, it is hereinafter referred to as TL degrees). The first comparator that compares the output with the output outputs 'I' if the detected temperature is TL degrees or higher, and outputs 201 otherwise. 9 is higher than the tube wall temperature (T degrees) at which the amount of light emitted by the light source 2 is maximum;
A second circuit that generates an output voltage of the temperature detection element 6 when the amount of light emitted from the light source 2 is 80% or more of the maximum amount of light emitted (when the tube wall temperature is TH degrees in FIG. 4, hereinafter referred to as TH degrees). A second comparator compares the output of the reference voltage source 10 and the output of the temperature detection element 6, and if the detected output is TH degree or less, the output is 1.
1', otherwise outputs 'O'. The first and second reference voltage sources 8.10 are capable of arbitrarily setting the output voltage of the temperature detection element 6 when the tube wall temperature is within the above-described range. 11 is a light source lighting control means for controlling the lighting of the fluorescent lamp 2 based on the comparison results of the first and second comparators 7.9, and 12 is a reading scanning control means for controlling reading scanning. As mentioned above, fluorescent lamps generally have a spectral distribution (emission spectrum) depending on the mercury vapor pressure.
Because the characteristics change, when the tube wall temperature of a fluorescent lamp is low,
The mercury vapor pressure is not kept low, resulting in a spectral distribution with a large amount of infrared light, and for this reason, accurate color separation cannot be performed in a color document reading device that separates and reads a color document into red light, green light, and blue light. Furthermore, as shown in Figure 4, the luminous efficiency of a fluorescent lamp changes depending on the temperature of the tube wall, and if the tube wall temperature becomes too low or too high, there will be insufficient light intensity, which will have a negative effect on reading even when reading black and white originals. . For this reason, it is best to always control the tube wall temperature of the fluorescent lamp 2 to the temperature at which the amount of emitted light is maximum and the standard spectral distribution is obtained (degree T in Figure 4), that is, the temperature at which the best luminous efficiency is achieved. Although this is ideal, in reality preheating takes a long time and control becomes difficult, making it impractical. Therefore, the spectral distribution characteristics are almost the same as the standard spectral distribution without affecting the processing of the output signal of the photoelectric conversion element 4. It becomes more practical by controlling the temperature within the range that can be obtained.

The operation of the embodiment of the present invention will be explained using FIG. 1.
! When the power is turned on, the self-regulating heating element 5 is energized and performs self-control so that the tube wall temperature of the fluorescent lamp becomes T degrees. However, as shown in FIG. It takes time for the tube wall temperature of the lamp 2 to reach a temperature (hereinafter referred to as T degrees) at which the luminous efficiency is maximum and a standard spectral distribution is obtained. In other words, immediately after the power is turned on, the tube wall temperature is low and the fluorescent lamp emits a large amount of infrared light, making it impossible to perform accurate color separation when reading a color document. Therefore, when a reading start command is given, the temperature detection element 6 detects the tube wall temperature (TM degrees) of the fluorescent lamp, and the first and second comparators 7.9 adjust the tube wall temperature of the fluorescent lamp to a predetermined value. Temperature range (
TL degree or more and TH degree or less) is determined. The tube wall temperature of the fluorescent lamp detected immediately after the power is turned on is TL.
When TM<TL<TH, the first and second comparators 7.9 as shown in FIG.
The outputs of are 'OI and 21', and at this time, the fluorescent lamp lighting control means 11 turns on the fluorescent lamp 2 and preheats the fluorescent lamp not only by the self-regulating heating element 5 but also by the heat generated by the fluorescent lamp itself. By doing so, the preheating time can be shortened. After that, when the tube wall temperature of the fluorescent lamp 2 rises and reaches a predetermined temperature range, that is, when TL:i;TM≦TH, the outputs of the first and second comparators 7.9 become eV and 11', Reading is started by the reading scanning control means 12 while the fluorescent lamp 2 is turned on.

Further, when the tube wall temperature of the fluorescent lamp is higher than TH degrees during continuous reading, that is, when TL<TH<TM, the outputs of the first and second comparators 7.9 are 11' as shown in FIG. 101, the fluorescent lamp lighting control means 11 does not turn on the fluorescent lamp 2 and waits until the temperature of the tube wall of the fluorescent lamp 2 falls. After that, when the tube wall temperature of the fluorescent lamp 2 decreases and reaches a predetermined temperature range, that is, when TL5TM≦TH, the first
The outputs of the second comparator 7.9 become 11' and 11', the fluorescent lamp 2 is turned on, and the reading scanning control means 12 starts reading. In this case, if the fluorescent lamp is cooled using a cooling fan, the time required for cooling can be shortened. Further, if the tube wall temperature of the fluorescent lamp 2 is within a predetermined temperature range, that is, if TL≦TM≦TH, the fluorescent lamp 2
With this configuration, there is no need to always turn on the fluorescent lamp, the preheating time of the fluorescent lamp is shortened, and the standard spectral distribution of a fluorescent lamp can always be obtained, resulting in high luminous efficiency. Since fluorescent lamps are used in the temperature range, accurate color separation can be performed without adversely affecting photoelectric conversion elements.

Effects of the Invention As described above, the document reading device of the present invention has a simple configuration and can perform accurate color separation because the fluorescent lamp is always used in the temperature range where the standard spectral distribution of the fluorescent lamp can be obtained. Moreover, the preheating time of the fluorescent lamp can be shortened even when the power is turned on.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a document reading device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of the same device, FIG. FIG. 4 is a diagram showing the distribution characteristics, FIG. 4 is a diagram showing the relationship between the tube wall temperature of a fluorescent lamp and the relative amount of emitted light, and FIG. 5 is a diagram showing the characteristics of a self-regulating heating element. 1... Original, 2... Fluorescent light, 3... Lens, 4...
...Photoelectric conversion element, 5...Self-controlled sexual intercourse i? A element,
6...Temperature detection element, 7.9...Comparator, 8.10
... Reference voltage source, 11 ... Light source lighting control means, 12
...Name of reading control agent Patent attorney Toshio Nakao Haka18 Figure 1 Figure 2 (TL < TH) Figure 3 (a) (b)

Claims (6)

[Claims] (1) a light source that illuminates the original; a photoelectric conversion element that receives reflected light from the original and converts it into an electrical signal; a self-controlling heating element and a temperature detection element that are attached to the tube wall of the light source; and a second reference voltage source, first and second comparators that respectively compare the output of the temperature detection element and the output of the first and second reference voltage sources, and and a light source lighting control means for controlling lighting of the light source based on the output of the comparator. (2) The document reading device according to claim 1, wherein the light source is a fluorescent lamp. (3) The voltage generated by the first reference voltage source is lower than the tube wall temperature of the light source when the standard spectral characteristics of the light source are obtained and the amount of light emitted by the light source reaches its maximum, and the amount of light emitted by the light source is lower than the maximum amount of light emitted. 3. The document reading device according to claim 1, wherein the voltage is equal to the output voltage of the temperature detection element when the temperature is 80% or more. (4) The voltage generated by the first reference voltage source is equal to the output voltage of the temperature detection element when the tube wall temperature of the light source is 30 degrees or more and 38 degrees or less. The document reading device described in Section 1. (5) The voltage generated by the second reference voltage source is higher than the tube wall temperature of the light source when the standard spectral characteristics of the light source are obtained and the amount of light emitted by the light source is at its maximum, and the amount of light emitted by the light source is higher than the maximum amount of emitted light. 3. The document reading device according to claim 1, wherein the voltage is equal to the output voltage of the temperature detection element when the temperature is 80% or more. (6) The voltage generated by the second reference voltage source is equal to the output voltage of the temperature detection element when the tube wall temperature of the light source is 38 degrees or more and 55 degrees or less. The document reading device described in Section 2.