JPS63138869A - Image reader - Google Patents

Abstract

PURPOSE:To improve the stability of an original face illuminance by constituting a light source by a rare gas discharge tube and improving the leading characteristic of the original face illuminance. CONSTITUTION:The read section is provided with the ceiling plate 21 and a frame 27 formed in its cross section as nearly pi-shape by the said ceiling plate 21 and parallel side plates 23, 25 provided perpendicularly thereto. The frame 27 is subjected to an alumite processing and the processing of electric insulation. A xenon discharging tube 29 is sealed with gaseous xenon therein and a high frequency voltage in 20 - 30kHz is applied between electrodes 71 and 73 provided at both ends of the discharging tube to light through a cold cathode discharge. An auxiliary electrode 75 is fitted to the tube surface in the longitudinal direction of the xenon discharging tube 29. The auxiliary electrode 75 attracts electrons radiated from the electrode 71 or 73 and to apply quick and sure discharge, and the straight stability of plasma is ensured at the start of lighting and also during the lighting is ensured to attain the stability of the original face illuminance.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an image reading device that is connected to, for example, a personal computer and reads an original image according to instructions from the personal computer. The present invention relates to an image reading device that enables stabilization of illuminance characteristics.

(Prior Art) Image reading devices of this type that use a fluorescent tube or an LED (light emitting diode) array as a light source are conventionally known.

As is well known, a fluorescent tube collides electrons emitted from an electrode with mercury particles, converting the emitted ultraviolet rays into visible light and irradiating them.

However, since this fluorescent tube contains mercury vapor, it has the following problems when used as a light source for an image reading device.

In other words, the brightness of the fluorescent tube is affected by mercury vapor pressure, that is, the environmental temperature, so as shown in Figure 10, from the start of lighting, the document surface has sufficient illuminance for reading processing (indicated by the dashed line in the figure). It takes a long time to reach this point, about 15 seconds, and the rise characteristics are poor. In addition, since it is easily affected by changes in the outside temperature, in order to stabilize the amount of light, a dimmer is used to monitor the light m of the fluorescent tube and maintain a sufficient level of illuminance on the document surface. However, this light control device has problems in that it is large in size, heavy, and expensive.

On the other hand, as shown in FIG.
A large number of individual elements 501 are arranged and a condensing lens 503 is bonded onto the LED element 501, as shown in FIG. 9.

However, as can be understood from the light distribution characteristics shown in FIG. 11, which shows the illuminance of the document surface in the longitudinal direction, the LED array described above produces bright and dark areas on the document surface corresponding to the arrangement of the LED elements 501. There is a problem in that so-called wavy development occurs in illuminance, and a separate circuit for correcting this wavy development is required, resulting in a complex device configuration.

Furthermore, since the LED element is made of a semiconductor, it has a problem of poor stability with respect to temperature.

(Problems to be Solved by the Invention) As described above, in the conventional image reading device described above, those using a fluorescent tube as a light source have poor startup characteristics, and are large and heavy in order to stabilize the amount of light. There are problems such as the need for a large dimming Vt setting, and for those using an LED array as a light source, the temperature stability of the LED element is poor, requiring a separate circuit to correct the wavy development mentioned above. There were some problems, such as:

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide an image reading device with stable document surface illuminance and a compact size.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the image 8i reading device of the present invention is characterized in that the light source is constituted by a rare gas discharge tube.

(Function)- In the present invention, a rare gas discharge tube is used as a light source,
This rare gas discharge tube is a cylindrical glass tube in which a rare gas such as xenon is sealed.

Since this rare gas discharge tube is a cold cathode discharge tube and does not contain mercury, it has an extremely good start-up from the start of lighting until reaching the specified illuminance. Furthermore, the illumination intensity relative to the ambient temperature is also maintained stably. Furthermore, sufficient illuminance can be obtained even with a small tube diameter, making it possible to downsize the device.

(Embodiment) FIG. 1 shows a side sectional view showing the structure of an embodiment of the apparatus according to the present invention.

In this embodiment, a device main body 100 on a box and a device main body 10
Paper feeding unit 200. It includes a reading section 300 and a paper ejecting section 400. Document insertion slot 1 of device main body 100
The original inserted from
After the original document surface image information is read by the reading section 300, the document is discharged to the outside of the apparatus main body 100 by the paper discharging section 400.

The paper feed section 100 includes a first document detector 3 that detects an inserted document, a paper feed roller 5 that is driven when the first document detector 3 detects insertion, and a feed roller 5 that is driven when the first document detector 3 detects the inserted document. A second document detector 7 is provided to detect the document.

The paper ejection section 300 also includes a transport roller 9 that transports the scanned original, and a third original detector 1 that detects the transported original.
1 and a paper ejection roller 13 for ejecting the transported document to the outside of the apparatus.

Then, the paper feed roller 5. The conveyance roller 9 and the paper discharge roller 13 are simultaneously driven by a step motor 15 via a belt 17. The step motor 15 is driven and controlled so as to start at the document detection timing of the first document detector 3, and to stop after a predetermined period of time has elapsed after the end of the conveyed document leaves the third document detector 11. ing.

Further, each of the rollers 5.9 and 13 is formed of a rubber roller at the lower stage and a plastic roller at the upper stage, and each of the upper stage plastic rollers is supported on a shaft so as to be able to move slightly in the vertical direction. Smooth document transport is possible without being affected by

FIG. 2 is a plan view of the reading section 200, and FIG. 4 is a side view taken in the direction of arrow A in FIG. 3.

As shown in FIGS. 1 and 3, this reading section 200
A top plate 21 and a parallel side plate 2 provided perpendicular to this top plate 21
3.25, the frame 27 is formed into a substantially π-shaped cross section.
It is equipped with

A xenon discharge tube 29, which will be described later, is positioned and fixed in the storage space within the frame 27. Further, a rod-shaped lens array 31 is attached to one side plate 23 of the frame, and of the light irradiated from the xenon discharge tube 29, the light reflected from the document reading surface is focused. A compression spring 33 is elastically mounted between this rod-shaped lens array 31 and the top plate 21, and a hexagonal wrench 35 provided at the lower end of this rod-shaped lens array 31 moves the rod-shaped lens array 31 in the vertical direction. The focal length can be adjusted by moving it. A light guiding section 37 is opened in the top plate 21 directly above the rod-shaped lens array 31.

Further, an image sensor 41 is provided on the top plate 21 of the frame 27 so that the light receiving element section 39 is located at the light guide section 37 . This image sensor 41 is a contact-type amorphous silicon image sensor, and has an original width (A
1728 light receiving elements 39 in the same length as 4 sizes)
are arranged, and document surface information can be read at a pixel density of 8 lines/aS. Therefore, fast response is possible,
Furthermore, since it is a close contact type, it is possible to downsize the device.

In addition, the image sensor 41 and the top plate 21111 are equipped with a scanning circuit for driving the light-receiving element section 39 and an i-width circuit for amplifying an analog signal proportional to the amount of light received by the light-receiving element section 39. The substrate 43 and the light receiving element portion 39 are made of conductive rubber on the lower side and insulating rubber on the upper side. ! Support body 4 having a structure
They are electrically connected via 5. Furthermore, this board 43 is connected to a harness connector 47 through which drive power is supplied, control signals, and image signals are input and output - and these image sensors 41 . The drive board 43 and the support body 45 are covered by an upper cover 49.

Further, along the bottom surface of the top plate 21 and the side surface of the rod-shaped lens array 31, a light shielding member 5o having an inverted cross section is fixed with a conductive adhesive. The light shielding member 50 is made of a conductive tape such as copper foil, and prevents scattered light (stray light) of the light irradiated by the xenon discharge tube 29 other than the reflected light from the document reading surface that is focused by the rod-shaped lens array 31. The light is prevented from entering the light receiving element section 39 from the light guide section 37, and electromagnetic waves and static electricity are removed.

On the other hand, a glass plate 5 is provided in the opening 51 of the π-shaped frame 27.
3 is attached by a fixed part @55. This glass plate 53 serves as a moving path for the original, and is made of transparent glass with excellent transparency.

As shown in FIG. 1, a reference color correction plate 61 is in surface contact with this glass plate 53, and this reference color correction plate 61 is urged upward with a weak elastic force by a pair of compression springs 57 and 59. has been done. This reference color correction plate 61 is a white plate for white reference correction to correct image signals including shading distortion noise and variations between pixels from the light receiving element section 39, and its outer surface is free from dirt. It has a strong special coating. The start of reading the white reference correction data is based on a timing signal from the first document detector 3 that detects the document.

Figure 4 shows the xenon emission 1! FIG. 5 is an external configuration diagram of the xenon discharge tube.

This xenon family! ! f! 29, xenon gas is sealed inside the tube, and between the electrodes 71 and 73 provided at both ends, 20~
A high frequency voltage of 30 kHz is applied to cause a cold cathode discharge to emit light. In this example, manufactured by Toshiba Corporation,
A low power consumption type xenon discharge tube with a tube diameter of 5.8 mm and an emission wavelength of 546 nm is used.

Further, an auxiliary electrode 75 is attached to the tube surface in the longitudinal direction of the xenon discharge tube 29. This auxiliary electrode 75
is provided to attract electrons emitted from the electrodes 71 or 73 for quick and reliable discharge.This ensures straight-line stability of the positive column not only at the start of lighting but also during continued lighting, and the document surface Stability of illuminance is ensured.

Further, an aperture 77 is provided on the tube surface, and the discharge tube 2
The aperture angle of 9 is maintained at approximately 60 degrees.

The discharge tube cover 78 supports the discharge tube 29, protects the auxiliary electrode 75, and blocks radiation from the back side of the discharge tube 29. Note that 81 and 83 are holders for fixing the discharge tube 29 and the discharge tube cover 78.

Furthermore, a high frequency voltage of 20 to 30 KH2 is applied to each electrode 71, 73 and the auxiliary electrode 75 from the power supply device via the cable 79, but the cable 79 of this embodiment is composed of a shielded cable, and the A wire coated in a net shape is grounded to the outside of the device. This prevents the generation of radiated noise from the cable 79 and avoids adverse effects on peripheral circuits and signal cables.

FIG. 6 shows the illuminance characteristics of the xenon discharge tube. In the figure, the horizontal axis indicates the lighting time from the start of lighting, and the vertical axis indicates the document surface illuminance. Further, a point g111A in the figure indicates sufficient illuminance for the image sensor 41 to read the original surface image.

As is clear from comparing the illuminance characteristics of the fluorescent tubes shown in the same figure and FIG. It is understood that the rise characteristics are excellent. Furthermore, even after the illuminance of the original surface reaches a sufficient value, the stability of the illuminance of the original surface is extremely good, so that a high-quality original surface image reading signal can be obtained. Moreover, the pipe diameter is φ5.88
- Since sufficient irradiation is obtained using a very thin xenon discharge tube, it is possible to downsize the optical system and, by extension, downsize the entire device.

FIG. 7 shows the light distribution characteristics of the xenon discharge tube, where the horizontal axis shows the left and right ends and the center in the longitudinal direction, and the vertical axis shows the illuminance on the document surface.

As can be seen from the same figure, the conventional LE shown in FIG.
Compared to the characteristics of the D array, the illuminance on the document surface within the effective range is extremely stable. Therefore, the shading correction circuit also has a simple configuration, and the device can be miniaturized.

[Effect of the invention] As explained above, according to the present invention, a light source is rare.

Since it is constructed with a gas discharge tube, the rise characteristics of the illuminance on the document surface are improved without being affected by the temperature of the surrounding ring 11, and the stability of the illuminance on the document surface is improved.

(2) Since the illuminance on the document surface is stable, there is no need for a light control device as in the case of a fluorescent tube, and the apparatus can be made more compact.

(3) Since a tube with a small diameter can be used, it is possible to downsize the optical system and reduce power consumption.

It has such excellent effects.　　　　　′

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of the device according to the present invention, FIG. 2 is a plan view showing the configuration of the reading section, FIG. 3 is a sectional view taken in the direction of arrow A in FIG. 2, and FIG. is a cross-sectional view showing the configuration of a xenon discharge tube, Figure 5 is a perspective view showing the external configuration of the xenon discharge tube, Figure 6 is an illuminance characteristic diagram of a xenon effi tube, and Figure 7 is a light distribution characteristic of a xenon discharge tube. Fig. 8 is a configuration diagram of a conventional LED array, Fig. 9 is an external view of the same LED array, Fig. 10 is an illuminance characteristic diagram of a fluorescent tube, and Fig. 11 is a diagram of an LED array.
It is a light distribution characteristic diagram of an array. 100... Apparatus main body 200... Paper feed section 300... Reading section 400... Paper discharge section 27... Frame 29... Xenon discharge tube (light source) 31... Rod-shaped lens array (collector) Optical means) 41... Image sensor (photoelectric conversion means) 71.73... Electrode 75... Auxiliary electrode

Claims (4)

[Claims] (1) A light source that irradiates the document, a condenser that converges the light emitted from the light source and reflected from the document, and a condenser that receives the light focused through the condenser and converts it into the light. What is claimed is: 1. An image reading device comprising: a photoelectric conversion means for generating a corresponding electric signal; and the light source is a rare gas discharge tube. (2) The image reading device according to claim 1, wherein the rare gas discharge tube is a xenon discharge tube. (3) The image reading device according to claim 1, wherein the rare gas discharge tube has a cylindrical shape. (4) The image reading device according to claim 1, further comprising an auxiliary electrode provided on the longitudinal outer wall surface of the rare gas discharge tube.