JPH0417497B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image reading device, and sometimes an image reading device that exposes a document to light using a halogen lamp.

Halogen lamps, fluorescent lamps, and the like are known as light sources for exposing a document in an image reading device. Among them, halogen lamps are widely used because they emit a large amount of light and have relatively flat color characteristics.

On the other hand, optical reading of images has traditionally been done by e.g.
This is done using a CCD sensor, but in recent years,
As the sensitivity of CCD sensors has improved, it has become possible to shorten the storage time of the sensor, but on the other hand,
When an AC power supply is used for the halogen lamp as the light source, it becomes susceptible to variations in the amount of light emitted depending on the power supply frequency, and there is a problem in that the read image data includes ripple irregularities.

Furthermore, if the halogen lamp is turned on by applying a DC voltage to prevent the ripple unevenness described above, a sudden voltage is applied at the start of lighting, which may adversely affect the life of the halogen lamp.

The present invention has been made in view of the above points, and has been developed over a long period of time when reading original images.
It is an object of the present invention to provide an image reading device that can convert into a digital image signal with high precision.

In order to achieve the above object, an image reading device of the present invention generates a digital image signal from an original by moving relative to the original. Conversion means for converting supplied power into DC voltage (in the embodiment, rectifier circuits D2, D3, C4, C5, CH
1, CH2), a halogen lamp (halogen lamp 9) that generates light to be irradiated onto the document using the converted DC voltage, and a digital converter for each pixel that converts the reflected light from the document irradiated by the halogen lamp into a digital A photoelectric conversion means (CCD 15) for converting into an image signal, and a signal failure means (color main unit) for generating an instruction signal for instructing the start of reading the document
CPU 35) and control means (soft start circuit 39, etc.) for controlling the DC voltage applied to the halogen lamp, and the control means gradually increases the voltage in response to an instruction signal from the signal generation means. The DC voltage is controlled so as to increase, and the relative movement is started after the amount of light irradiated by the halogen lamp is stabilized.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings. However, in the following explanation, a laser beam printer (hereinafter referred to as LBP) will be used as an example.

FIG. 1 shows a schematic configuration of an LBP to which the present invention is applied, and the reference numeral 9 in the figure is a halogen lamp for document illumination, which is moved in the direction shown by arrow A in the figure by a drive means (not shown). to scan the original 16. The reflected light from the original 16 is reflected by the mirror 10,
11, 12, lens 13, and R (red), G
An image is formed on the CCD 15 through a filter 14 consisting of a (green) and a B (blue) filter. CCD1
The image signal from 5 is sent to the processing device 17, which drives the laser device 18 according to the image signal.
A laser beam corresponding to an image signal generated from the photosensitive drum 2 is deflected by a polygon 20 that is driven to rotate at high speed by a scanner motor 19.
1 through the secondary charger 23 provided near the
The photosensitive drum 21, which has been primarily charged in advance by the primary charger 22, is exposed to light.
An electrostatic latent image corresponding to the original image is formed thereon. This electrostatic latent image becomes a complete latent image by full-surface exposure by the exposure device 27, and the developing devices 24, 25, 25 corresponding to the filter color selected by the filter 14
Development is performed by.

In synchronization with the above operation, the transfer paper is pulled out from the paper cassette 1 by the paper feed roller 2, and is wound around the transfer roller 5 via the conveyance roller 4 by the registration roller 3 in synchronization with the above operation. The toner attached to the surface of the photosensitive drum 21 due to the above-mentioned developing operation is transferred to the transfer roller 5 by the transfer pole 6.
The image is transferred to the transfer paper wrapped above.

The above development-transfer process consists of the three R, G, and B
This process is carried out three times through a color filter 14, and the transfer paper on which a color image corresponding to the image on the original document 16 has been transferred is sent by a conveyor belt 7 to a fixing roller 8, where it is fixed and discharged from the machine.

Next, a schematic configuration of the processing device 17 shown in FIG. 1 is shown in FIG. 2.

The output of CCD15 in Figure 1 is CCD input port 2
9 converts the data into serial data pixel by pixel.
The signal is sent to the CCD signal processing circuit 30. In the CCD signal processing circuit 30, a shading circuit first performs light amount correction, and then A/D conversion is performed. A signal conversion circuit 31 dither-processes the output signal of the CCD signal processing circuit 30, and the output of the signal conversion circuit 31 is transmitted to the scanner motor 19 and laser via a scanner motor drive circuit 33 and a laser drive circuit 34, respectively. device 18
Drive synchronously.

The above operations are controlled by the CPU 35 installed in the LBP, which controls the processing of the entire main body.

Further, a halogen lamp controller 36 is connected to the CPU 35. The halogen lamp controller 36 corrects the light intensity of the halogen lamp 9 by direct current control according to the filter color of the filter 14 used, and has a configuration as shown in FIG. 3, for example.

The halogen lamp 9 in Fig. 3 is a transistor Q.
1, Q2, and a switching regulator using a transformer Tr1 to turn on the DC current. On the secondary side of the transformer Tr1, there is a normal diode D2,
A halogen lamp 9 is connected to a rectifier circuit including D3, capacitors C4 and C5, and choke transformers CH1 and CH2, and an overvoltage sensor 60 for lamp protection. A DC voltage obtained by rectifying an AC voltage applied from terminals L1 and L2 by a bridge diode D1 and smoothing it by capacitors C1 and C2 is applied to both ends of the transistors Q1 and Q2 connected in series.

A circuit that controls the amount of light by controlling the oscillation of transistors Q1 and Q2 is configured as follows. In other words, CPU3 is activated in synchronization with the start of document scanning.
A lamp ON signal 45 sent from 5 is connected to a soft start circuit 39 via a photocoupler 37 and a remote circuit 38. The soft start circuit 39 has a low frequency oscillator 39A, and an oscillator 40 that controls the oscillation of transistors Q1 and Q2.
By gradually increasing the output pulse width of the pulse width modulator 41 having the halogen lamp 9 when the lamp is lit, sudden lighting of the halogen lamp 9 can be prevented.

The output of the pulse width modulator 41 is optically transmitted by the OPT 42 and connected to the transistors Q1 and Q2 via a drive circuit 43.

Furthermore, a correction circuit including comparators 44A and 44B using differential amplifiers is connected to the pulse width modulator 41, and its output pulse width is corrected. Of these, the comparator 44A feeds back and observes the voltage on the secondary side of the transformer Tr1, and accurately controls the voltage applied to the halogen lamp 9. The terminal of variable resistor VR1,
VR2, VR3 and transistors Q3, Q4, Q5
are connected in series, and via a variable resistor VR4 for adjusting the amount of light. Color signals R, G, and B corresponding to the scanning of each color are applied from the CPU 35 to the bases of the transistors Q3 to Q5, respectively.

In the above configuration, when a command to start scanning the original 16 is input to the CPU 35, the photocoupler 37,
Soft start circuit 3 via remote circuit 38
9 is activated, and by this soft start circuit 39, the halogen lamp 9 is first faded in. At the same time, one of the transistors Q3 to Q5 is selected by one of the signals R, G, and B corresponding to the filter color of the filter 14. and variable resistor VR3
After the light amount correction of the halogen lamp 9 corresponding to each color filter set by 5 to 5 is performed, the halogen lamp 9 moves in the direction of arrow A in FIG. 1, and scanning of the original is started.

As described above, scanning, development, and transfer are performed three times for each color, so the variable resistors VR1 and VR are controlled by the R, G, and B signals output from the CPU 35.
2, VR3 is selected, and the light amount correction of the halogen lamp 9 corresponding to each filter color is performed.

At this time, the light amount correction setting is performed as follows.

In an LBP or a color copying machine, the transmission characteristics of the R, G, and B filters expressed in specific energy and the emission characteristics of the halogen lamp for document scanning are as shown in FIG. That is, the spectral energy distribution of a halogen lamp is a value obtained by multiplying Planck's equation for a black body by the spectral emittance of tungsten, with less on the short wavelength side and more on the long wavelength side. As for the characteristics of the R, G, and B filters, the spectral energy increases in the order of B to G to R. To correct this, B, G,
The values of the variable resistors VR1 to VR3 may be set so that the voltage applied to the halogen lamp 9 is lowered in the order of R.

It should be noted that the overall light intensity correction can be performed using the variable resistor VR4, but it goes without saying that the settings of VR1 to VR4 described above may be changed by the operator using a lever provided on the scanning panel, etc. be.

As described above, according to the present invention, in an image reading device for generating a digital image signal from an original by moving relative to the original, power supplied from an AC power source is converted into a DC voltage. By means of a conversion means for converting into , and the converted DC voltage,
a halogen lamp that generates light to be irradiated onto the original; a photoelectric conversion unit that converts light reflected from the original irradiated by the halogen lamp into a digital image signal for each pixel; and a start of reading the original. and a control means for controlling the direct current voltage applied to the halogen lamp, and the control means gradually adjusts the voltage to The direct current voltage is controlled so that the voltage increases, and the relative movement is started after the amount of light irradiated by the halogen lamp is stabilized, thereby reducing the adverse effects of ripple unevenness when reading an original image. Moreover, since the relative movement is started after the amount of light irradiated by the halogen lamp becomes stable, it is possible to convert into a digital image signal with high accuracy. Further, by having the above-mentioned control means, it is possible to extend the life of the halogen lamp when applying a DC voltage to the halogen lamp.

[Brief explanation of drawings]

Fig. 1 is a schematic block diagram of the LBP to which the present invention is applied, Fig. 2 is a block diagram showing the structure of the processing device of the LBP of Fig. 1, and Fig. 3 is a block diagram showing the structure of the halogen lamp controller of Fig. 2. The circuit diagram and FIG. 4 are diagrams showing the transmission characteristics of each color filter and the light emission characteristics of the halogen lamp. 9...Halogen lamp, 14...Filter,
17... Processing device, 35... CPU, 36... Halogen lamp controller, 40... Oscillator, 4
1...Pulse width modulator, 44...Comparator,
VR1 to VR4...variable resistance.

Claims (1)

[Claims] 1. An image reading device for generating a digital image signal from a document by moving relative to the document, which converts power supplied from an AC power source into a DC voltage. a converting means; a halogen lamp that generates light to be irradiated onto the document using the converted DC voltage; and a halogen lamp for converting reflected light from the document irradiated by the halogen lamp into a digital image signal for each pixel. The apparatus includes a photoelectric conversion means, a signal generation means for generating an instruction signal instructing to start reading the document, and a control means for controlling a DC voltage applied to the halogen lamp, and the control means generates the signal. The DC voltage is controlled so that the voltage gradually increases in response to an instruction signal from the means, and the relative movement is started after the amount of light irradiated by the halogen lamp is stabilized. Image reading device.