JPS63224556A - Information reader - Google Patents

Abstract

PURPOSE:To attain light quantity control with simple constitution by detecting the conducting current of a resistor of temperature dependant resistor preheating a light source, and controlling the electrifying to the resistor of temperature dependance by the detected output. CONSTITUTION:In applying power to read an original, the temperature dependant resistor 8 is electrified at the same time and the preheat of a fluorescent light 5 is started. The current is detected by a current detector 9 and when the current reaches I2 or below, the fluorescent light 5 reaches a tube wall temperature T1 lighted at a luminescence characteristic required for reading, the fluorescent light 5 is lighted and reading is started. In applying the read continuously, the fluorescent light 5 is heated and the tube wall temperature may reach T2. In such a case, the conducting current of the resistor 8 is detected by the detector 9 and it is detected that the tube wall temperature reaches T2 or over by the current and a detection signal is sent to a current control means 10. The means 10 stops the power application to the resistor 8 to prevent the temperature rise of the fluorescent light 5.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to optical information reading devices such as facsimiles and OCR, and more particularly to controlling the amount of light from a light source made of a fluorescent lamp.

2. Description of the Related Art Fluorescent lamps have been commonly used as light sources for information reading devices. Fluorescent lamps have different luminous characteristics (light intensity, spectral distribution, etc.) due to the vapor pressure of mercury vapor sealed inside the glass tube.
There is a difference in the vapor pressure, and the vapor pressure changes depending on the tube wall temperature of the fluorescent lamp. For example, when the tube wall temperature is low, the vapor pressure decreases, the amount of emitted light decreases, and a large amount of infrared light components are emitted, making it impossible to obtain a spectral distribution suitable for reading. Furthermore, when the tube wall temperature is high, the vapor pressure increases and the amount of emitted light decreases.

Therefore, when using a fluorescent lamp as a light source, it is necessary to use it at a tube wall temperature at which the luminescent characteristics are stable.

Conventionally, therefore, a light intensity control method was used in which a self-temperature-controlling heater made of a temperature-dependent resistor was attached to a fluorescent lamp to preheat the fluorescent lamp at a constant temperature, and a temperature detector made of a heat-retaining heater and a thermistor was installed around the fluorescent lamp. A light amount control method has been proposed in which a fluorescent lamp is preheated at a constant temperature to a tube wall temperature that maximizes the luminous efficiency of the accompanying fluorescent lamp. For example, JP-A-61-144964 and JP-A-61-154358.

Problems to be Solved by the Invention However, such conventional light amount control methods have had various problems, including the following.

First, in the case of light intensity control using a fluorescent lamp with a self-regulating heater, power is not supplied to the heater when the device is not powered, so when reading is performed immediately after power is supplied to the device, the fluorescent lamp Since it is not possible to determine whether the temperature of the tube wall has risen to a level at which reading can be performed, reading is performed while the luminescent characteristics of the fluorescent lamp are unstable. In addition, in the case of light intensity control using a fluorescent lamp with a heater and a thermistor,
Many parts and circuits were required, such as a heater control circuit, a thermistor 9 temperature detection circuit, etc.

Therefore, the present invention detects that the tube wall temperature of the fluorescent lamp has increased to a point at which the light emission characteristics become stable, and also controls the amount of light without requiring many parts or circuits.

Means for Solving the Problems The technical means of the present invention for solving the above-mentioned problems is to control the light amount of the fluorescent lamp by detecting the current flowing through a temperature-dependent resistor that preheats the fluorescent lamp. It is.

action The effect of this technical means is as follows.

That is, the temperature of the temperature-dependent resistor measured in advance vs.
From the current characteristics, determine the permissible current range within the tube wall temperature range where the fluorescent light emission characteristics are stable, and control the current flow to the temperature-dependent resistor to keep it within the permissible range, as well as control the lighting of the fluorescent light source. It is something.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

In FIG. 1, 1 is a document on which information is written, 2 is a platen roller that conveys the document 1 during reading, 3 is a presser plate that presses the document 1 against the platen roller 2 and generates a conveying force, and 4 is the document after it has been read. 1 is a guide plate that guides the document 1; 6 is a fluorescent lamp that illuminates the reading position of the document 1; 6 is a one-dimensional image sensor that receives reflected light from the document 1 and converts it into an electrical signal; A lens that focuses light on the one-dimensional image sensor 6; 8, a temperature-dependent resistor that preheats the fluorescent lamp 6; 9, a current detector that detects the current flowing through the temperature-dependent resistor 8;
Reference numeral 10 denotes an energization control means for controlling the energizing current to the temperature-dependent resistor 8 and controlling the lighting of the fluorescent lamp 5.

The temperature dependent resistor 8 generates heat at a constant temperature when energized.
As shown in Figure 2, its temperature resistance characteristics are as shown in Figure 2. At low temperatures, the resistance value is low, so the current flowing increases and the self-heating effect increases, and at high temperatures, the resistance value is high, so the current flowing becomes small. It is also called a constant temperature heating element because it has the characteristic of reducing its self-heating effect and always maintains a constant temperature.

In addition, the light emitted light amount vs. tube wall temperature characteristic of the fluorescent lamp 5 has a chevron-shaped characteristic as shown in FIG. Then, the operating temperature range of the fluorescent lamp 6 is between T1 and T2. Furthermore, the spectral distribution of the fluorescent lamp 6 becomes a spectral distribution suitable for reading when the temperature exceeds the lower limit temperature 74 of the operating temperature range. Therefore, the allowable range (T) of the tube wall temperature within which the luminescent characteristics of the fluorescent lamp 6 are suitable for reading.

The allowable range (I, to I2) of the current flowing through the temperature-dependent resistor 8 at T2) is determined.

Next, the operation of the configuration of this embodiment will be explained.

information? When reading the written document 1, the information reading device is first powered on. At this time, temperature dependent resistor 8
At the same time, the lamp 5 becomes energized and preheating of the fluorescent lamp 5 starts, and the current detector 9 detects the energizing current, and when the current value becomes less than x2, the tube wall temperature at which the fluorescent lamp 5 can be turned on with the luminous characteristics necessary for reading is reached. At T1, the fluorescent lamp 6 is turned on and reading begins. The temperature-dependent resistor 8 is controlled to self-heat so that the tube wall temperature (approximately 40'C) is reached at which the amount of light emitted by the fluorescent lamp 6 is maximized. However, if reading is performed continuously, the fluorescent lamp 5 may be heated due to heat generated by the fluorescent lamp 50 and heat generated by circuit components within the device, and the tube wall temperature may rise to 40° C. or higher. At this time, the current flowing through the temperature-dependent resistor 80 is detected by the current detector 9, and the tube wall temperature is determined from the current value at 40°C.
When it is detected that the temperature has increased above 'C, the energization control means 10
The energization control means 10 then stops energizing the temperature-dependent resistor 8, thereby preventing the temperature of the fluorescent lamp 6 from rising. In addition, if the installation conditions of the device are particularly bad, for example, if the device is installed in a place that receives direct sunlight or if the temperature inside the device exceeds the upper limit temperature T2 of the operating temperature range, the current detection It is detected from the current value 11 detected by the lamp 9 that the tube wall temperature has risen to the upper limit temperature 72 or higher, and a detection signal is sent to the energization control means 10, which then turns on the fluorescent lamp. prohibit.

That is, if the tube wall temperature of the fluorescent lamp 6 is between the tube wall temperature T at which the luminous intensity required for reading is 4 or more and T2, the fluorescent lamp 6 is turned on, and if it becomes 72 or more, it is turned off. The lighting of the fluorescent lamp 5 is controlled based on the output of the current detector 9 so as to stop the operation. Furthermore, the energization control means 10 includes a fluorescent lamp 5 using the temperature dependent resistor 8.
In order to shorten the preheating time, lighting control may be performed to turn on the fluorescent lamp 5 during preheating.

In addition, in the explanation of the operation of this embodiment, the platen roller 2,
The holding plate 3, the guide plate 4, the one-dimensional image sensor 6, and the lens 7 have the same functions as the components conventionally used in optical information reading devices such as facsimiles and OCR, so their functions are simple. The explanation will be omitted.

Effects of the Invention The present invention controls the light amount of the fluorescent lamp by detecting the current flowing through the temperature-dependent resistor I that preheats the fluorescent lamp, so there is no need for a temperature detector such as a thermistor or a temperature detection circuit. This simplifies the configuration.

Furthermore, since the temperature of the tube wall of the fluorescent lamp can be maintained within a temperature range in which the light emission characteristics of the fluorescent lamp are stable, stable reading is always possible.

[Brief explanation of drawings]

FIG. 1 is a side view of an information reading device according to an embodiment of the present invention (FIG. 2 is a temperature-dependent resistance characteristic diagram of a temperature-dependent resistor;
FIG. 3 is a graph showing the luminous intensity and S tube wall temperature characteristics of a fluorescent lamp. 6... Fluorescent lamp, 8... Temperature dependent resistor, 9... Current detector, 1o... Current flow control means. Name of agent: Patent attorney Toshio Nakao and 1 other person! −
1 Hara Maki? -Platen roller J--4〒4 circles 4-Itto id 5 Sentence 5-11 firelight 10--1 distance view 1 @ Yohan

Claims (2)

[Claims] (1) A light source consisting of a fluorescent lamp that illuminates a document containing information, a one-dimensional image sensor that receives reflected light from the document by this light source and converts it into an electrical signal, and a one-dimensional image sensor that receives the reflected light from the one-dimensional image sensor. a temperature-dependent resistor for preheating the light source; a current detector for detecting the current flowing through the temperature-dependent resistor; An information reading device equipped with an energization control means for controlling energization. (2) The information reading device according to claim 1, wherein the energization control means controls the lighting of the light source.