JPS63246967A - Original reader - Google Patents

Abstract

PURPOSE:To contrive to miniaturize the titled reader by using a heat from a drive resistor of a stepping motor causing internal temperature rise for preheating a fluorescent light, thereby eliminating the need for a preheater or a self-control heat element. CONSTITUTION:When a tube wall temperature of a fluorescent light detected by a temperature detection element 6 is lower than the tube wall temperature at which the lighting efficient of the light source is maximum and the standard spectrum distribution characteristic of the light source is obtained and the stimulated luminous quantity of the light source is 80% or over the maximum stimulated luminous quantity, a resistor selection circuit 12 controls the 1st stepping motor drive resistor 7 so as to be connected to a power supply 11 by an output of a comparator 10. Thus, the current driving the stepping motor 14 flows through the 1st stepping motor drive resistor 7 and the fluorescent light 2 is heated quickly by the heat generated in the 1st stepping motor drive resistor 7.

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 particularly to temperature control of its light source.

2. Description of the Related Art Fluorescent lamps are generally used as light sources in conventional document reading devices. The spectral distribution (emission spectrum) of fluorescent lamps changes depending on the mercury vapor pressure. When the tube wall temperature 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 shown in Figure 3-2, but instead shows the infrared rays shown in Figure 3-1. It exhibits a spectral distribution characteristic with a large amount of light, and therefore, when reading a color original, accurate color separation cannot be performed. Therefore, the problem has been how to raise the tube wall temperature of the light source to a temperature at which standard spectral distribution characteristics can be obtained.

Conventionally, in order to solve this problem, there is a method of preheating the fluorescent lamp by turning on the fluorescent lamp before reading the document to ensure the stability of the color temperature and brightness of the fluorescent lamp (for example, Japanese Patent Laid-Open No. 61-80
No. 946), and a method of installing a self-regulating heating element as a preheating heater in a fluorescent lamp (for example, Japanese Patent Application 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 fluorescent lamps deteriorates and reading is affected. Furthermore, if the fluorescent lamp is preheated only by the self-regulating heating element, it will take time to preheat when the fluorescent lamp is cold, such as when the power is turned on, due to the response time of the self-regulating heating element.

The method of installing a heat-retaining heater around a fluorescent lamp and controlling the energization of the heat-retaining heater to the temperature at which the luminous efficiency of the fluorescent lamp is maximized requires a heat-retaining heater and a power supply amount control device for the heat-retaining heater, making it more compact and economical. This becomes a problem.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides an optical system including at least a light source for illuminating an original, a temperature detection element for detecting the tube wall temperature of the light source, and a standard spectrometer for the light source. Provided between the output motor of the temperature detection element and this motor and the power supply when the temperature of the tube wall is lower than the temperature at which distribution characteristics are obtained and luminous efficiency is maximized, and the amount of light emitted by the light source is 80% or more of the maximum amount of light emitted. a first resistor disposed near the light source, a second resistor disposed at a position away from the light source, and energization of one of the first and second resistors according to a comparison output of the comparator. and a resistance selection circuit for selecting the resistance.

Effect of the present invention With the above-described configuration, the tube wall temperature of a fluorescent lamp is detected by a temperature detection element, and the tube wall temperature is determined when the detected output and the light emission rate of the light source are maximum and the standard spectral distribution characteristics of this light source are obtained. lower, and the amount of light emitted by the light source is 80% of the maximum amount of emitted light.
% or more, and when the output voltage of the temperature detection element is higher than the reference voltage (when the detected temperature is low), the current is applied to the first resistor. The current flows through the second resistor to preheat the fluorescent lamp, and at other times, current flows through the second resistor to set the tube wall temperature of the fluorescent lamp to an appropriate temperature.

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

FIG. 1 is a block diagram of a document reading device according to an embodiment of the present invention, in which 1 is a document to be read, 2 is a light source that illuminates the document 1, and 3 is a lens that forms an image of the document on a photoelectric conversion element 4. 5 is an optical system composed of a light source 2, a lens 3, and a photoelectric conversion element 4. 6 is a temperature detection element that detects the tube wall temperature of the light source 2; 7 and 8 are first and second stepping motor driving resistors selected by the resistance selection circuit 12 and connected to the power supply 11; 9 is a light emitting element of the light source. Reference voltage that generates the output voltage of the temperature detection element when the luminous intensity is lower than the temperature of the tube wall when the standard spectral distribution characteristics of this light source are obtained at its maximum and the amount of light emitted by the light source is 80% or more of the maximum amount of light emitted. 10 is a comparator that compares the output of the temperature detection element 6 with the output of the reference voltage source; 11 is a stepping motor driving power source; 13 is a stepping motor driving circuit;
4 is a four-phase stepping motor, 15 is a drive pulley, 1
6 is a driven pulley, and 17 is a conveyor belt. Note that the voltage of the reference voltage source 9 is lower than the tube wall temperature when the light emission rate of the light source is maximum and the standard spectral distribution characteristics of this light source can be obtained, and when the light emission amount of the light source is 80% or more of the maximum light emission amount. The output voltage range of the temperature detection element 6 can be arbitrarily set within the temperature range of the tube wall.

Ideally, fluorescent lamps should be used at the tube wall temperature when the luminous efficiency is maximum and the standard spectral distribution characteristics of this light source are obtained.
It is not practical because preheating takes a long time. Therefore, it is more practical to control the temperature at a temperature that provides a light amount that does not affect reading and that provides spectral distribution characteristics that are almost close to standard spectral distribution characteristics. be.

To explain the reading scan in this embodiment, when a scan start command is given, the light source 2 is turned on, and the stepping motor 14 moves the optical system 5 attached to the conveyor belt 17 and the document 1 relative to each other to form an image of the document. is read by the photoelectric conversion element 4.

In this case, in order to perform high-speed reading, a resistor is connected between the winding of the stepping motor 14 and the power supply 11 to apply a high voltage to reduce the time constant and increase the torque (L/nR drive method).

The temperature control method of this embodiment will be explained with reference to FIG. FIG. 2 is a diagram for explaining a method of controlling the temperature of a light source. In FIG. 2, the same parts as in FIG. 1 are given the same numbers. A fluorescent lamp 2 having thermal shoes 18 is used as a light source. The thermal shoe 18 is used to equalize the temperature of the tube wall of the fluorescent lamp 2, and has an opening (not shown) so as not to obstruct the illumination light onto the document. The first stepping motor drive resistor 7 is attached to a fluorescent lamp heat insulator,
The second stepping motor driving resistor 8 is provided in a well-ventilated location within the device.

The tube wall temperature of the fluorescent lamp is detected by the temperature detection element 6, and this detection output and the light emission rate of the light source are lower than the tube wall temperature at the maximum when the standard spectral distribution characteristics of this light source are obtained, and the amount of light emitted by the light source is A comparator 10 compares the output voltage of the reference voltage source 9 that generates the output voltage of the temperature detecting element when the amount of light emitted is 80% or more of the maximum light emission amount, and controls the resistance selection circuit 12 based on the output of this comparator. Let's do it. In other words, the tube wall temperature of the fluorescent lamp detected by the temperature detection element 6 is lower than the tube V temperature when the light source's luminous efficiency is maximum and the standard spectral distribution characteristics of this light source are obtained, and the luminous intensity of the light source is the maximum luminous intensity. When the temperature is lower than the temperature range of 80% or more, the resistor selection circuit 12 controls the first stepping motor drive resistor 7 to be connected to the power supply 11 based on the output of the comparator 10. Therefore, the current driving the stepping motor 14 is
The fluorescent lamp 2 is quickly warmed up by the heat generated by the first stepping motor driving resistor 7. After that, the luminous intensity of the fluorescent lamp 2 is lower than the tube wall temperature when the light source's luminous efficiency is maximum and the standard spectral distribution characteristic of this light source is obtained, and the luminous intensity of the light source is 8
When heated to a temperature range of 0% or higher, the output of the comparator 10 changes, and the resistor selection circuit 12 selects the second stepping motor drive resistor 8 and connects the power supply 11 and the second stepping motor drive resistor. 8.

The heat generated by the second stepping motor drive resistor 8 is radiated to the outside, so it does not affect the fluorescent lamp.
Can read originals.

Through the above operations, even when the tube wall temperature of the fluorescent lamp is low, after the power is turned on, the tube wall temperature can be quickly preheated to a temperature at which the necessary light intensity can be obtained and spectral distribution characteristics close to the standard spectral distribution characteristics can be obtained. be able to.

Further, in this embodiment, a four-phase motor is used as the stepping motor, but it goes without saying that the same effect can be obtained if the motor uses the same L/nR driving method.

Effects of the Invention As described above, according to the present invention, the heat generated by the stepping motor driving resistance, which is harmful to the internal temperature in conventional devices, is used for preheating fluorescent lamps, thereby improving the preheating heater and self-control. This eliminates the need for heat generating elements, making the device smaller and more economical.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a document reading device according to an embodiment of the present invention, Fig. 2 is a block diagram for explaining temperature control of the light source of the same device, and Fig. 3 is a characteristic showing the spectral distribution characteristics of a fluorescent lamp. It is a diagram. 1... Original, 2... Light source, 3... Lens, 4...
・Photoelectric conversion element, 5... Optical system, 6... Temperature detection element, 7.8... Stepping motor drive resistor, 9.
... Reference voltage source, 10... Comparator, 11... Power supply,
12...Resistance selection circuit, 13...Stepping motor drive circuit, 14...Stepping motor, 15...
・Drive pulley, 16... Driven pulley, 17... Conveyor belt Name of agent Patent attorney Toshio Nakao 1 person Figure 2

Claims (5)

[Claims] (1) an optical system including at least a light source that illuminates the original;
a temperature detection element that detects the tube wall temperature of the light source; a reference voltage source that generates a predetermined voltage; a comparator that compares the voltage of the reference voltage source with the output of the temperature detection element; and the optical system. a stepping motor that moves the document relative to the document;
A first resistor disposed between the stepping motor and the power source and disposed near the light source, a second resistor disposed at a position away from the light source, and a comparison output of the comparator to reduce the resistance of the first and second resistors. and a resistor selection circuit that selects energization to one of the resistors. (2) The document reading device according to claim 1, wherein the light source is a fluorescent lamp. (3) The document reading device according to claim 1 or 2, wherein the light source has heat-retaining shoes. (4) The voltage generated by the reference voltage source is lower than the tube wall temperature at which the standard spectral distribution characteristics of the light source are obtained and the luminous efficiency is at its maximum, and the amount of light emitted by the light source is 80% or more of the maximum amount of light emitted. The document reading device according to claim 1, 2, or 3, wherein the output voltage of the temperature detection element is the output voltage of the temperature detection element at the time of the change in temperature. (5) The voltage generated by the reference voltage source is the output voltage of the temperature detection element when the tube wall temperature of the light source is 30 degrees or more. Manuscript reading device.