JPH05276319A - Picture reader - Google Patents

Abstract

PURPOSE:To minimize a pre-heat time of a hot cathode fluorescent tube. CONSTITUTION:The picture reader comprising a cathode ray fluorescent tube 30 preheated and driven to emit light through the use of a pre-heat circuit and a fluorescent tube lighting drive circuit 31 and arranged so as to emit the light onto an original face and comprising a picture read circuit 20 reading a picture through the reception of a reflected light from an original face is provided with lighting time count storage means 41, 42, 43, 48, extinguish time count storage means 41, 42, 43, 48, a pre-heat time length storage means 43, pre-heat time length selection means 41, 42, and pre-heat drive signal generating means 41, 42, and an optimum pre-heat time length PTi is automatically selected for the lighting this time based on a history relating to a preceding lighting time length Ti and extinguish time lengths ti occurred so far in the hot-cathode fluorescent tube 30 and a pre-heat circuit 31P is pre-heated and driven.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus which receives light reflected from a document surface to read an image.

[0002]

2. Description of the Related Art A hot-cathode fluorescent tube which is preheated and driven to emit light by using a preheating circuit and a fluorescent tube lighting drive circuit and arranged so as to be able to irradiate light on a document surface, and an image which receives light reflected from the document surface An image reading device formed by including an image reading circuit for reading is known. As shown in FIG. 5, the fluorescent tube drive circuit (31) of such an image reading apparatus comprises a preheating circuit 31P and a fluorescent tube lighting drive circuit 31L. When a lighting command is issued, the preheating circuit 31P is first activated to activate hot cathode fluorescent light. The filament of the tube is heated, and then the fluorescent tube lighting drive circuit 31L is activated to emit light.

In FIG. 5, a lighting command, that is, a lighting signal F
When LON is output (“L level”), the preheating circuit 31
A current flows between point T1 and point T2 of P, and the capacitor C is charged. While being charged, the transistor Q
Since the base voltage of 2 is low, the transistor Q2 is off. Therefore, since the transistors Q3 and Q6 are turned on, a heating current flows through the filament (not shown) through the terminals Fil3 and Fil4. After that, when the capacitor C is charged to a level at which the transistor Q2 turns on, the transistors Q3 and Q6 turn off and the heating current flowing through the filament is cut off.

Then, the well-known fluorescent tube lighting drive circuit 31L operates and a lighting current flows from the terminals Fil1 and Fil2 to light the hot cathode fluorescent tube. On the other hand, when a turn-off command, that is, a turn-off signal (FLON) is output (“H level”), the hot cathode fluorescent tube is turned off.

That is, the conventional fluorescent tube drive circuit 31 is
Since the control unit outputs the lighting / extinguishing signal FLON (L level / H level) to drive and control the preheating circuit 31P and the fluorescent tube lighting driving circuit 31L, the preheating circuit 31P includes the resistor R and the capacitor shown in FIG. It is formed so as to be preheated for a fixed time determined by the circuit constant with C.

[0006]

By the way, since the hot cathode fluorescent tube irradiates the document surface with light, and the image reading circuit reads the image by receiving the reflected light from the document surface, The amount of light emitted from the cathode fluorescent tube must be kept constant. Here, the circuit constant (R × C) is generally set relatively large with a certain margin. This is to prevent deterioration of read image quality due to insufficient preheating time.

However, when reading a number of originals in succession, the preheating time is wasted, which may hinder an increase in reading speed as a whole. However, it is not always the case that a number of originals are continuously read, and therefore it is not possible to set the circuit constant to a small value in line with continuous reading.

Thus, conventionally, the circuit constant has been carefully set in consideration of the operation of the apparatus, that is, the ratio between continuous reading and intermittent reading, but it must be set to a large value. It was

An object of the present invention is to provide an image reading apparatus capable of achieving high-speed reading while ensuring high-quality reading while shortening the preheating time.

[0010]

According to the present invention, the preheating time length of this time is automatically selected from the history of the previous lighting time length of the hot cathode fluorescent tube and the previous extinguishing time length of the hot cathode fluorescent tube so as to eliminate the unnecessary preheating time. It is configured to be possible.

That is, the image reading apparatus according to the present invention is
A hot-cathode fluorescent tube which is preheated and driven to emit light by using a preheating circuit and a fluorescent tube lighting drive circuit and arranged so as to be able to irradiate light on the original surface, and an image reading circuit which reads an image by receiving reflected light from the original surface In an image reading apparatus formed including, a lighting time counting storage unit that stores a lighting time length until the light is turned off while counting the time when the hot cathode fluorescent tube is turned on, and the hot cathode fluorescent tube From the extinction time counting storage means for storing the extinction time length up to the current time while counting the elapsed time from the extinction time last time, from the last extinction time length and the extinction time length of the hot cathode fluorescent tube Preheating time length storage means for storing a predetermined preheating time length at the time of lighting, and lighting time length stored in the lighting time count storage means based on the lighting command and stored in the extinction time count storage means Disappearing The preheating time length selecting means for reading the time length and searching the preheating time storage means to select the preheating time length, and the preheating driving signal for outputting the preheating driving signal for driving the preheating circuit for the selected preheating time length. And a generating means.

[0012]

In the present invention having the above-described structure, the lighting time counting and storing means counts and stores the lighting time length while the hot-electrode fluorescent tube is turned on. On the other hand, while the light is off, the off-time counting storage means counts and stores the off-time length. When there is a lighting command, the preheating time length selecting means reads the previous lighting time length and the previous extinguishing time length from both the count storage means and searches the preheating time length storage means to automatically determine the preheating time length. select. Then, the preheat drive signal generation means outputs the preheat drive signal for the preheat time length to activate the preheat circuit.

Therefore, if the past history, that is, the previous lighting time length and the previous extinguishing time length are set in advance in the preheating time length storage means, the hot cathode fluorescent tube is lit at the minimum preheating time at any time. As a result, high-quality reading is possible with high image quality as a whole.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image reading apparatus according to the present invention will be described below with reference to the drawings. The image reading apparatus shown in FIGS. 1 to 3 has a basic configuration of a preheating circuit 31P of a hot cathode fluorescent tube 30 and a fluorescent tube lighting drive circuit 31L similar to that of a conventional example (FIG. 5), and lighting. Time counting storage means (41, 42,
43, 48) and turn-off time counting storage means (41, 42, 4)
3, 48), preheating time length storage means (43), preheating time length selection means (41, 42), and preheating drive signal generation means (4).
1, 42) are provided to turn on the hot cathode fluorescent tube 30 last time.
It is configured so that the optimum and minimum current preheating time length can be automatically selected according to the history of the turn-off time length.

The same or common parts as those of the conventional example (FIG. 5) are designated by the same reference numerals, and the description thereof will be simplified or omitted.

First, the overall structure of this apparatus will be described with reference to FIG. This device is roughly classified into a detection element (CCD sensor).
10, an image reading circuit 20, a hot cathode fluorescent tube 30 as a light source, a drive circuit 31 for the hot cathode fluorescent tube 30, a document feeding device (stepping motor 32, motor drive circuit 33), and a control unit 40.
It consists of and.

The detection element 10 is formed of a large number of pixels and receives the reflected light from the white reference surface (not shown) and the original and converts it into a corresponding voltage signal. The detection element 10 is driven by the timing circuit 11 and the detection element 1
The voltage signal from 0 (each pixel) is converted into a digital signal via the amplifier 12 and the A / D converter 13 and input to the image reading circuit 20. A document is moved and supplied to the detection element 10 by a feeding mechanism including a stepping motor 32 and a driver 33.

The control section 40 includes a CPU 41 and a ROM.
42, RAM 43, interface 44, timer circuit 48, etc., which are connected by a data bus 45, a control bus 46 and an address bus 47.
The ROM 42 stores a program that exerts the drive control function of the entire apparatus as well as the shading correction function.

The lighting time counting and storing means is a means for counting the time during which the hot cathode fluorescent tube 30 is turned on and storing the lighting time length Ti until the hot cathode fluorescent tube 30 is turned off.
It comprises a ROM 42, a timer circuit 48 and a RAM 43. Specifically, when the lighting signal FLON is output (“L level”) and the preheating is finished and the lighting is started (ST16 and 17 in FIG. 4), the counting storage is started (ST18) and the turn-off command (ST19) is issued. Stop counting when there is (ST
20). That is, when the light is turned on, the timer circuit 48 performs the counting operation, and when the turn-off command is issued, the CPU 41 causes the ROM 42 to operate.
It is supposed that the count value (Ti) is read based on the program and written in the RAM 43.

On the other hand, the extinguishing time count storage means is means for counting the elapsed time from the previous extinction time and storing the extinction time length ti up to the current time, which is also the CPU 41 and the ROM 4.
2, composed of a timer circuit 48 and a RAM 43,
It is executed in ST19, 21, and 11 of FIG. That is,
When the turn-off command, that is, the turn-off signal (FLON) is output (“H level”) (ST19), counting is started (ST21),
When the lighting signal FLON is output ("L level"), counting is stopped (ST11).

Further, the preheating time length storage means stores a preheating time length PTi for the present lighting, which is determined by a relationship between the previous lighting time length Ti, the previous extinction time length ti so far, and both of these time lengths Ti and ti. Is a means for correspondingly storing and is constituted by the RAM 43. That is, the preheating time length storage means (4
3), as shown in FIG. 3, the previous lighting time length T1 in the horizontal column.
~ T5, the preheating time length PTi determined by the previous turn-off time lengths t1 to t5 in the vertical column is stored as a table. For example, the previous lighting time length Ti is the longest time T5 (short time T
In 1), when the extinguishing time length ti is the shortest time t1 (long time t5), the preheating time length PTi is the minimum time PTss (the longest time PTll). The last lighting time length Ti is long (short), and the lighting time length ti up to this time is ti
If is short (long), the hot-cathode fluorescent tube 30 is still hot (cooled and cold) to a considerable temperature, so the preheating time length PTi may be shortened (must be long). That is, the preheating time length PTi of this time is stored in advance by the history of the previous lighting / off time length Ti · ti.
In this sense, in the case of the intermediate previous lighting time length T3 and the previous extinguishing time length t3, the preheating time length also becomes an intermediate value PTm.

Note that this storage form does not have to be a table form, and is formed so as to be stored as a function for calculating the present preheating time length PTi using the previous lighting time length Ti and the previous extinguishing time length ti as variables. You may.

Next, the preheating time length selection means, based on the lighting command (ST10), the lighting time length Ti stored in the lighting time count storage means and the extinction time length ti stored in the extinction time count storage means. Are read as the previous lighting time length and the previous extinguishing time length, respectively, and the preheating time length storage means (43) is searched to automatically select the preheating time length PTi for lighting this time.
2 and is executed in ST10, 12-14 of FIG.

The preheating drive signal generating means is means for outputting a preheating drive signal PREH ("H level") for driving the preheating circuit 31P for the selected preheating time length PTi,
It is composed of a CPU 41 and a ROM 42, and is executed in ST15 and ST16. In this embodiment, the photocoupler 5 shown in FIG.
3 (light emitting side element 51, light receiving side element 52) is provided instead of the conventional capacitor (C), and is formed so that the preheating time (PTi) can be controlled from the outside of the preheating circuit 31P. That is, by outputting the lighting signal FLON (“L level”) and simultaneously outputting the signal PREH (“L level”), the photocoupler 53 is turned on to lower the base voltage of the transistor Q2.
Turn off. Therefore, the transistors Q3 and Q6
Is turned on, the filament can be preheated. Then, when the actual preheating time Ta becomes equal to or longer than the selected preheating time length PTi (ST16), the preheating drive signal PTEH becomes OF.
F (“H level”) is performed and preheating is completed (ST1
7).

Next, the operation of this embodiment will be described. A lighting command, that is, a lighting signal FLON is output (“L level”) from the control unit 40 to the fluorescent lighting driving circuit 31L (ST1).
0) and the turn-off time counting storage means (41, 42, 43, 4)
8) stops counting the extinguishing time (ti). Therefore, the extinguishing time length ti is stored in the previous time.

Here, preheating time length selecting means (41, 4)
2) is a lighting time counting storage means (41, 42, 43, 4)
8) from the previous lighting time length Ti (for example, the longest lighting time T
5) is turned off time counting storage means (41, 42, 43, 4)
8) from the previous time off time ti (for example, the minimum time t
1) is read (ST12, 13), the preheating time length storage means (43) shown in FIG. 3 is searched, and the preheating time length PTi (for example, the minimum time length PTll) is selected (ST14).

Then, the preheating drive signal generating means (41, 4)
2) is the preheat drive signal PR for the selected preheat time length PTll
EH is output (“H level”) (ST15, 16).
Therefore, since the photocoupler 53 is turned on, the transistor Q2 is turned off, Q3 and Q6 are turned on, and the filament is preheated for the preheating time length PTll. And
The hot cathode fluorescent tube 30 is turned on at the same time when the preheating is completed (S
T17). This is automatically performed in hardware by the configuration of the fluorescent tube lighting drive circuit 31L.

When turned on, the lighting time counting storage means (4
1, 42, 43, 48) count the lighting time length Ti and store the value (ST18). Specifically, when the turn-off command, that is, the turn-off signal (FLON) is output (“H level”) (ST19), the CPU 41 causes the timer circuit 4 to operate.
8 and stores it in the RAM 43. That is, the counting is stopped (ST20). At the same time, the extinction time count storage means (41, 42, 43, 48) counts and stores the extinction time length ti (ST21). That is, the timer circuit 4
Set 8. Hereinafter, it returns to ST10.

According to this embodiment, however, the lighting time counting storage means (41, 42, 43, 48), the extinguishing time counting storage means (41, 42, 43, 48) and the preheating time length storage means (43). ), Preheating time length selecting means (41, 42) and preheating drive signal generating means (41, 42) are provided, and from the history of the lighting time length Ti ahead of the hot cathode fluorescent tube 30 and the extinguishing time length ti so far. Since the optimal preheating time length PTi for this lighting is automatically selected and the preheating circuit 31P is preheat-driven, the preheating time PTi for this lighting can be made necessary and sufficient to minimize it. it can. Therefore, useless preheating can be eliminated, and high-speed image reading can be achieved as a whole.

The preheating time length storage means is the RAM 43.
Is formed from the previous lighting time length Ti and the previous lighting time length t
The preheating time length PTi corresponding to i is set to the hot cathode fluorescent tube 30.
Since it can be set according to the specifications of the detector element 10 and the detector element 10, it has wide applicability.

[0031]

As described above, according to the present invention, the hot cathode counting storage means, the extinguishing time counting storage means, the preheating duration storage means, the preheating duration selection means, and the preheating drive signal generating means are provided, and the hot cathode is provided. From the history of the previous lighting time length of the fluorescent tube and the past extinguishing time length, it is configured to automatically select the optimum preheating time length for lighting this time and preheat drive the preheating circuit. The required preheating time can be minimized by making it necessary and sufficient. Therefore, it is possible to eliminate unnecessary preheating and achieve high-speed image reading as a whole.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is likewise a circuit diagram showing a fluorescent tube drive circuit.

FIG. 3 is also a diagram for explaining a preheating time length storage unit.

FIG. 4 is likewise a flowchart for explaining the operation.

FIG. 5 is a circuit diagram showing a conventional example.

[Explanation of Codes] 10 Detection Element 20 Image Reading Circuit 30 Hot Cathode Fluorescent Tube 31 Fluorescent Tube Driving Circuit 31L Fluorescent Tube Lighting Driving Circuit 31P Preheating Circuit 40 Control Unit 41 CPU (Lighting Time Counting Storage Means, Off Time Counting Storage Means, Preheating 42 ROM (lighting time count storage means, extinction time count storage means, preheating time length selection means, preheat drive signal generation means) 43 RAM (lighting time count storage means, extinction time count) Storage means, preheating time length storage means) 48 timer circuit (lighting time counting storage means, extinguishing time counting storage means) 53 photocoupler PREH preheating drive signal

Claims (1)

[Claims] 1. A hot-cathode fluorescent tube which is preheated and driven to emit light by using a preheating circuit and a fluorescent tube lighting drive circuit and arranged so as to be able to irradiate light on the surface of the original, and an image which receives light reflected from the surface of the original. In an image reading apparatus including an image reading circuit for reading, a lighting time counting storage unit that stores a lighting time length until the light is turned off while counting the time that the hot cathode fluorescent tube is turned on, and An extinction time counting storage unit that stores the extinction time length up to the current time while counting the elapsed time from the previous extinction time of the hot cathode fluorescent tube, and the previous lighting time length and the previous extinction time length of the hot cathode fluorescent tube Preheating time length storage means for storing a preheating time length for this lighting, which is determined from both durations, and a lighting time length and the extinction time count stored in the lighting time count storage means based on a lighting command. In storage means A preheating time length selecting means for reading the stored turn-off time length and searching the preheating time storage means to select the preheating time length, and a preheating driving signal for driving the preheating circuit for the selected preheating time length. An image reading apparatus comprising: a preheating drive signal generating means for outputting.