JP2002218236A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader by which shading defects due to the warp of a fluorescent lamp are prevented without adjusting a gain every time of power supply. SOLUTION: This image reader for image-forming the image information of an original on a plurality of line sensors 300 through an image forming optical system and reading the images is provided with a means for turning on the fluorescent lamp (light source) 305a, an adjusting means for adjusting the gain of line sensor output signals, a memory (storage means) 309 for storing a gain adjustment value, a setting means for setting the gain adjustment value, and a CPU (arithmetic means) 304 for computing the adjustment value stored in the memory 309. When the power supply is applied, the result of computing the gain setting value stored in the memory 309 in the CPU 304 is set in the setting means.

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 for reading image information of a document by forming an image on a solid-state image sensor through an imaging lens.

[0002]

2. Description of the Related Art Conventionally, image information of a document or the like is formed on a plurality of line sensors (solid-state imaging devices such as CCDs) via an image forming optical system, and a color image is formed based on an output signal from the line sensor. Various image reading apparatuses for digitally reading information have been proposed.

FIG. 6 is a configuration diagram of an optical system of a conventional color image reading apparatus. In FIG. 6, reference numeral 100 denotes a platen glass on which a read image is arranged; 101, a bar-shaped light source for illuminating the original; It is a reflection shade to enhance.

Thus, the rod-shaped light source 101 and the reflection shade 102
(Not shown) illuminated by the mirror 103a, 1
The light is guided to the image forming optical system 104 via the elements 03b and 103c, and the image forming optical system 104 forms image information of the document on the solid-state image sensor 105. The mirror 103a moves the image information of the original in the sub-scanning direction A at the scanning speed v, and the mirrors 103b and 103c move at the speed v / 2 in synchronism therewith, so that the direction in which the solid-state image sensors (line sensors) 105 are arranged. It is possible to read image information by two-dimensional scanning together with (main scanning direction).

In such a configuration, the solid-state imaging device 1
The image information formed on the image 05 is converted into an electric signal,
There is a case where the image information is output as a print output by being sent to an output device (not shown) or a case where the input image information is sent to a storage device or the like, and is used as each image reading device. I have.

As a light source of the image reading apparatus having such a configuration, a halogen lamp, a fluorescent lamp, a xenon lamp or the like is used. Halogen lamps have usually been used as a light source for this type of image reading apparatus. However, although halogen lamps have light luminance, the temperature rise of the apparatus accompanying the temperature rise of the lamp is large, and power consumption of 200 to 300 W is required. As a result, power consumption required for the entire apparatus is increased.

In recent years, fluorescent lamps and xenon lamps of high luminance have been developed to solve the above problems, and are being used as light sources for image reading apparatuses.

In a fluorescent lamp or a xenon lamp, a small amount of mercury particles and a few Torrs of Ar or Kr, Xe are contained in a rod-shaped hollow tube.
In many cases, various phosphors are applied to the inner wall of the tube, and electrodes are arranged at both ends of the tube to seal the tube.

The discharge from the electrodes excites the phosphor coated on the inside of the tube with ultraviolet rays emitted from mercury or various gases, and emits visible light according to the emission characteristics of the phosphor.

As the phosphor, various phosphors are selected according to the spectral energy characteristics required as a light source. In particular,
In a color image reading device, a light source in a wide wavelength range corresponding to RGB or the like is required. In particular, when a light source with high luminance is required, a method of mixing phosphors of a plurality of colors and applying the mixture to the inner wall of a tube is used. Is used.

[0011]

However, the above-mentioned prior art has the following drawbacks.

That is, like a fluorescent lamp or a xenon lamp,
In an image reading apparatus using a light source using a phosphor as a light emitting source, it is desirable to read an image after stabilizing spectra emitted from mercury or various gases. Therefore, when the lamp is not turned on during standby or the like, the temperature inside the tube is controlled to be constant by, for example, attaching a heater outside the tube to stabilize the spectrum, thereby stabilizing the emission spectrum.

FIG. 7 is a perspective view of a conventionally known fluorescent lamp.

The fluorescent lamp 201 includes sockets 202a, 202
b, both ends of which are supported by the sockets 202a,
A current is supplied from a pin 202b (not shown). An aperture (optical opening) is provided in a predetermined area of the fluorescent lamp 201.
A strong light is emitted in the direction of arrow a, and a relatively weak light is emitted from a region other than the aperture section 203. In addition, a light amount sensor 204 including a photodiode or the like is provided at an appropriate position of the fluorescent lamp 201, and detects a current corresponding to the light amount emitted from the fluorescent lamp 201.

In this type of image reading apparatus, the light intensity of a fluorescent lamp is detected by a light intensity sensor, and the light intensity is controlled by a light intensity controller so that the light intensity of the fluorescent lamp is constant.

However, the fluorescent lamp itself may be warped by heat generated when the fluorescent lamp is turned on. In the case of the above configuration, the distance between the fluorescent lamp and the light amount sensor changes, and a problem arises that the light amount cannot always be kept constant. Depending on the gain setting value of the line sensor, white correction by shading cannot be performed normally, which may affect a captured image.

The above problem can be dealt with by adjusting the gain of the line sensor when the power is turned on. However, if the gain is adjusted each time the power is turned on, a long warm-up time is required.

The present invention has been made in view of the above problems, and an object thereof is to provide an image reading apparatus capable of preventing shading failure due to warpage of a fluorescent lamp without performing gain adjustment each time power is turned on. Is to provide.

[0019]

According to a first aspect of the present invention, there is provided an image forming apparatus for forming an image of an original on a plurality of line sensors via an imaging optical system and reading the image. In the reading device, means for turning on the light source, adjusting means for adjusting the gain of the line sensor output signal, storage means for storing a gain adjustment value, setting means for setting the gain adjustment value, and storage in the storage means A calculating means for calculating the adjusted value, wherein a result obtained by calculating the gain set value stored in the storage means at power-on is set by the setting means.

According to a second aspect of the present invention, in the first aspect of the present invention, the gain adjustment value stored in the storage means is set by the setting means when a predetermined time elapses after the power is turned on. And

According to a third aspect of the present invention, in the first aspect of the present invention, the gain is adjusted when a predetermined time elapses after the gain is set, and the gain adjustment value is stored in the storage means. .

[0022]

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

FIG. 1 is a block diagram showing a basic configuration of a control system of an image reading apparatus according to the present invention. In FIG. 1, reference numeral 300 denotes a color line sensor for converting reflected light from a light source into an electric signal; Line sensor 300
Is an analog signal processing circuit for extracting a signal component from the signal and adjusting an offset and a gain.

Reference numeral 302 denotes the analog signal processing circuit 301
A for converting the signal output from the
A / D conversion circuit 303 is a circuit that performs image processing such as shading correction and input masking on the output signal of the A / D conversion circuit 302.

Reference numeral 305 denotes a fluorescent lamp unit, and 305a
Is a white fluorescent lamp having a plurality of phosphors, 305b is a fluorescent lamp heater for heating the fluorescent lamp 305a, and 305c is a thermistor for detecting the temperature of the fluorescent lamp 305a. 30
7, an inverter circuit for controlling lighting of the fluorescent lamp 305a;
A / 308 for converting the thermistor output into a digital signal
This is a D conversion circuit, and the converted digital signal is connected to the CPU circuit 304, and the feedback signal controls the fluorescent lamp heater 305 b via the amplifier 306.

Reference numeral 309 denotes a memory.
Controls the analog processing circuit 301 by the CPU circuit 304, adjusts the peak value when a uniform density original serving as a reference is read, to a predetermined value, and stores the adjustment result. The CPU circuit 304 includes a fluorescent lamp heater 305b.
Lighting control of the inverse circuit 307,
It also controls the image processing circuit 303.

FIG. 2 is a flowchart showing a control procedure of the image reading apparatus according to this embodiment.

After turning on the power, the gain adjustment value is read from the memory. This memory stores adjustment values adjusted when the fluorescent lamp is stabilized. Immediately after the fluorescent lamp is turned on, the line sensor output temporarily increases due to fluctuations in the infrared spectrum,
Thereafter, the light quantity decreases due to the warpage of the tube due to the self-heating of the fluorescent lamp (see FIG. 3). Since the line sensor output when the power is turned on is larger than the line sensor output when the light amount is stable, the gain adjustment value adjusted when the light amount is stable exceeds the gain target value and sometimes exceeds the shading target value. . In this case, in the shading correction for correcting the light distribution of the optical system, the correction of a portion exceeding the shading target value cannot be performed correctly, which affects an output image (see FIGS. 4 and 5). ).

Therefore, as the gain adjustment value set when the power is turned on, the result of calculating the gain adjustment value stored in the memory (the result obtained by reducing the predetermined ratio or the result obtained by uniformly reducing the predetermined value) is set.

Next, while waiting for a scan job, the time since power-on is counted. After a lapse of a predetermined time (time required for the inside of the tube to be stabilized by the self-heating of the fluorescent lamp heater and the lighting during the job), the gain adjustment value is read again from the memory, and this value is set as it is in the analog processing circuit.

After setting the gain adjustment value in the memory, the time is further counted. Then, when the predetermined time is counted, it is determined that the fluorescent lamp has become stable, and the gain is adjusted. The adjustment value is stored in a memory, and the stored adjustment data is used as data at the next power-on.

[0032]

As is apparent from the above description, according to the present invention, in an image reading apparatus which reads an image by forming image information of a document on a plurality of line sensors via an image forming optical system, Means for turning on the light source, adjustment means for adjusting the gain of the line sensor output signal, storage means for storing the gain adjustment value, setting means for setting the gain adjustment value, and adjustment value stored in the storage means Is provided, and when the power is turned on, the result of calculating the gain setting value stored in the storage means by the calculating means is set by the setting means, so that the gain is adjusted each time the power is turned on. Without this, an effect is obtained that shading failure due to warpage of the fluorescent lamp can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a control system of an image reading apparatus according to the present invention.

FIG. 2 is a flowchart showing a control procedure of the image reading apparatus according to the present invention.

FIG. 3 is a diagram showing a change over time in the amount of light.

FIG. 4 is a diagram illustrating gain adjustment and shading correction.

FIG. 5 is a diagram for explaining an influence at the time of shading failure.

FIG. 6 is a configuration diagram of an optical system of a conventional color image reading device.

FIG. 7 is a perspective view of a fluorescent lamp.

[Explanation of symbols]

 300 Line sensor 301 Analog signal processing circuit 302 A / D conversion circuit 303 Image processing circuit 304 CPU 305 Fluorescent lamp unit 305a Fluorescent lamp 305b Fluorescent lamp heater 305c Thermistor 306 Amplifier 307 Inverter circuit 308 A / D conversion circuit 309 Memory

Continuation of the front page F term (reference)

Claims (3)

[Claims] 1. An image reading apparatus for forming an image of a document on a plurality of line sensors via an image forming optical system and reading an image, wherein a light source is turned on, and a gain of a line sensor output signal is adjusted. Adjustment means, a storage means for storing a gain adjustment value, a setting means for setting the gain adjustment value, and a calculation means for calculating the adjustment value stored in the storage means. An image reading apparatus, wherein a result obtained by calculating a stored gain set value by the calculation means is set by the setting means. 2. The image reading apparatus according to claim 1, wherein when a predetermined time elapses after the power is turned on, the gain adjustment value stored in the storage unit is set by the setting unit. 3. The image reading apparatus according to claim 1, wherein the gain is adjusted when a predetermined time elapses after the gain is set, and the gain adjustment value is stored in the storage unit.