JPS62227265A - Original reader - Google Patents

Abstract

PURPOSE:To obtain a device having high luminance and a long life, and to improve the efficiency of an original reading, by providing the first shield which covers a high frequency impressing means that impresses a high frequency on an electrode, and a discharge tube, and has an aperture part through which light passes, and the second shield which covers the aperture part, and opening the aperture part in the operating time of an original. CONSTITUTION:An illumination unit 22 consists of a discharge tube 10, an electrode 11, a high frequency input terminal 14, and a high frequency generating source. A reflecting shade 12 having an aperture part 15 is provided at the periphery of the discharge tube 10, and a high frequency lamp power source is provided within a shield 17, and whole of the unit except the rectangular aperture part 15 is shielded including the side part of the discharge tube in a longitudinal direction. The aperture part 15 is shielded by a shield 13 before the lighting of the discharge tube, and when a signal to read the original is inputted, a high frequency voltage is impressed on the electrode 11. By the lighting of the discharge tube, the illumination unit starts to scan the original, and the aperture part 15 is separated from the shield 13, and a beam of light is irradiated on the original. All of the shields are formed by conductive members, and are earthed, thereby, a noise, such as an electrode wave, etc., can be shielded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to a document reading device used in an electrophotographic device or the like.

(Background Art) Conventionally, a fluorescent lamp or a halogen lamp has been used as a light source for a document reading device.

However, the lifespan and brightness of these light sources are determined by the filament inside the light source, and it is difficult to prevent the filament from deteriorating, so the lifespan is short, and if a large current is applied to the filament, the filament will burn out. The drawback was that high brightness could not be obtained.

In order to solve this problem, a light source that does not have a filament inside has been proposed.

FIG. 11 is a cross-sectional view of this light source without a filament inside.

In the figure, 4 is a discharge tube whose inner wall is coated with phosphor 3, and mercury and inert gas are sealed inside.

A protruding cylindrical portion 7 is formed in the lamp 4 so as to include the transformer 2. The transformer 2 includes a core 5 and a coil 5, and both ends of the coil 5 wound around the core 5 are connected to an AC power source 8.

When a high frequency voltage is applied to the coil 5 from the AC power source 8, a high frequency electromagnetic field is generated around the coil 5. The electric energy of this electromagnetic field excites the mercury gas in the lamp 4, and the ultraviolet rays of the mercury caused by this excitation are converted into visible light by the phosphor 3 applied to the surface of the lamp 4.

Unlike conventional fluorescent lamps, halogen lamps, etc., these light sources do not have electrodes inside the lamp, so the filament does not break when used, and high brightness is achieved because large amounts of power can be input to the coil. And it has a long life.

When this light source was used in a document reading device, a problem arose in that the document reading device malfunctioned or did not operate.

(Objective) The present invention solves the above problems and provides a document reading device that has high brightness, has a long life, and does not adversely affect the document reading device.

(Summary of the Invention) To achieve the above object, the present invention provides a document reading device in which an illumination device relatively scans the document. A first electrode provided in contact with or near a wall, a high frequency applying means for applying a high frequency to the electrode, and a first electrode that covers the discharge tube and has an opening through which light passes.
A document reading device comprising a shield and a second shield covering the opening, the second shield covering the opening when the discharge tube is lit, and opening from the opening when manipulating the document. .

(Example) The present inventors investigated why malfunctions or non-operations occur when a light source that does not have a filament inside the discharge tube is used in a document reading device, and found that by the time the discharge tube lights up, It was confirmed that the main cause was that a large amount of noise, especially noise caused by electromagnetic waves, was generated and had an adverse effect on the control circuit of the document reading device.

The technical object of the present invention is to solve this problem.

First, the light source section according to the present invention will be explained.

FIG. 4 shows an embodiment of the light source section.

In the figure, numeral 1 indicates a high-frequency lamp power supply, IO is a discharge lamp, the glass is ordinary soda glass or pyrex glass, and the inner surface is coated with a predetermined phosphor. Furthermore, the discharge lamp is filled with mercury and an inert gas.

As shown in the figure, the lamp has a tubular shape, which is a preferable shape as a light source used for slit exposure in a document reading device. Reference numeral 11 denotes an electrode provided on the end side of the discharge lamp connected to a high-frequency lamp power source, and covering the circumferential surface of the lamp. The material may be any ordinary conductor, but copper, stainless steel, etc., which are less likely to oxidize, are preferable.

When a high frequency voltage is applied between the electrodes, the mercury gas is excited by the high frequency electric field generated, and the ultraviolet rays generated thereby are converted into visible light by the phosphor coated on the inner wall of the discharge lamp.

With this configuration, the discharge lamp emits light uniformly in the longitudinal direction, has high brightness, and has a long life, so it is very effective as an illumination light source for an original reading device.

FIG. 5 is a diagram showing another electrode shape. The electrode is wound in a coil shape multiple times near the center of the discharge tube in the longitudinal direction of the discharge tube. It is preferable to wind the electrodes near the center of the tube in the longitudinal direction in order to improve the discharge state. According to this shape, it is possible to apply higher power to the electrode than in FIG. 4, and even higher brightness can be obtained, which is more preferable. In addition, the high frequency used in the embodiments of FIGS. 5 and 6 is 106 to 1
0'Hz is preferred.

FIG. 1 is a cross-sectional view of an embodiment of the invention.

In the figure, the lighting unit 22 includes a discharge tube 10° electrode 1
1, a high frequency input terminal 14, and a high frequency generation power source (not shown). There is an opening 15 around the discharge tube 10.
A light beam emitted from the discharge tube passes through an opening 15 and is guided to the document side. A high frequency lamp power source (not shown) is provided within the shield 17. This illumination unit 22 is also shielded at the side portions in the longitudinal direction of the discharge tube, and the entire area other than the rectangular opening 15 is shielded.

This opening 15 is shielded by a shield 13 attached to the lower part of the document table shown in FIG. 11, which will be described later.

Before lighting the discharge tube, the opening 15 is in the above state and the shield 13 is closed.
is shielded by When a document reading signal (not shown) is input, a high frequency voltage is applied to the electrode 11 through the terminal 14.
is applied to When the discharge tube lights up, the illumination unit starts scanning the document, and the opening 15 is separated from the shield 13.
The light beam is irradiated onto the original.

All of the shields are made of conductive materials, and are also grounded to block noise such as electromagnetic waves.

As shown in Figure 4, high-frequency power is input to the lamp via an input power source, a high-frequency oscillation circuit, an amplifier, and a transmission line.The above-mentioned lighting unit is equipped with a high-frequency oscillation circuit and a transmission line to reduce power loss. It is also preferable because it reduces noise and blocks noise.

Further, although this embodiment has been described using a so-called document table moving type, it goes without saying that the same thing is possible with a document table moving type. In this configuration, the opening 15 is shielded by the shield 13 by scanning the original, so the configuration is very simple, reliable, and very preferable.

FIG. 2 shows another embodiment, in which when the discharge tube is lit, the shield 13 is moved along the guide 18 by a drive mechanism (not shown) such as a plunger.

Similarly, in FIG. 3, the shield 13 provided at the opening of the illumination unit 22, which has a high frequency power source inside and is completely shielded except for the opening, moves in the direction of the arrow along the guide 18. This configuration is effective in shielding noise when it increases due to an unexpected accident at any time, that is, even during scanning.

Next, the operation timing of the shield 13 will be explained.

(Hereinafter, the shield 13 will be referred to as a shutter.) The circuit configuration is shown in the block diagram of FIG. 8.

The reflected power is detected by a reflected power detection circuit between the amplifier and the transmission line. This reflected power is the main cause of noise. This reflected power is A/D converted and compared with a predetermined value set in advance by the control section, and when it becomes smaller than the predetermined value, the shutter is released and document scanning begins.

This sequence is shown in the flowchart of FIG.

It goes without saying that this shutter release includes the illumination unit 22 starting scanning in the embodiment shown in FIG.

When the scanning of the original is completed and the illumination unit and the original have returned to their predetermined relative positions, the opening is covered with a shutter again. Therefore, this shutter does not need to cover the opening while the discharge tube is lit (although it may cover the opening at the same time as or after the discharge tube is turned off).

In the above, the shutter and document scanning were controlled by detecting the reflected power, but without being limited to this, it is also possible to provide a light amount detection sensor and release the shutter when a predetermined amount of light is reached. The rise time of the discharge tube may be determined in advance, and the shutter may be released after this predetermined time.

Next, the present invention will be explained in detail using FIG. 9.

FIG. 9 is an explanatory diagram of the present invention, showing the relative intensities of input power, reflected power, and noise, with time plotted on the horizontal axis.

First, explanation will be given using FIG. 9(a).

As the discharge tube and electrodes, those having the shape shown in FIG. 5 are used.

When power is input at the time, the reflected power is about half of the input power, as shown by A in the figure, and this results in a large amount of noise.

When the discharge tube discharges at time t2, the reflected power rapidly decreases as shown by B in the figure.

The actual noise intensity is shown in FIG. 9(b).

In this way, a large amount of noise is generated before discharge, but
After discharge, the noise becomes extremely small and is at a level that is acceptable for practical use.

In the present invention, the noise is shielded during the period t1 to t2 when the noise is large, and the noise does not leak outside, thereby eliminating malfunctions and non-operations of the document reading device.

Further, by shielding the high frequency oscillation circuit, transmission line, and lamp, noise is further reduced, and a document reading device with even higher safety can be provided.

FIG. 10 is a sectional view of an image forming apparatus having a document reading device to which a ninth embodiment of the present invention is applied.

In the figure, 1.21 is a document placement cover, 22 is an illumination device of this embodiment, which moves integrally with the first mirror 23 in the A direction, and together with the second mirror 24 which also moves in six directions, so-called two pairs of illumination devices. 1 optical system is formed. 25 is an in-mirror lens, and 26 is a third mirror, which projects an optical image onto the photosensitive drum 27 by subjecting the document to slit exposure. 28
is a charger for forming a latent image on a photoreceptor having an insulating layer on its surface.

After the photosensitive drum is uniformly charged, image exposure is performed,
An electrostatic latent image is formed on the drum surface. 29 is a blank exposure lamp, which removes unnecessary charges on the drum. 3
0 is a developing device for visualizing the latent image thus formed.

On the other hand, cut paper as a recording material in the paper feed stacker 31 is fed by a pickup roller 32, passed through a paper feed guide 33, a visible image on the drum 27 is transferred by a transfer charger 34, and then transferred to a conveyance section 35. The sheet is conveyed, converted into a fixed image in a fixing device 36, and discharged to a sheet discharge stacker 37.

The developer remaining on the drum 27 during the transfer process is removed by the cleaner 3.
After the drum 27 is removed in step 8, the drum 27 is neutralized by a static eliminator 39 and a static eliminator 40 in order to erase the electric image remaining on the photoreceptor, and returns to its original state. In addition, 41 is a blank exposure lamp which forms a latent image bright portion in order to prevent development from being performed when the optical system is backed up.

(Effects of the Invention) As described above, according to the present invention, it is possible to provide a highly reliable document reading device with a simple configuration, high brightness, long life, and no malfunction or inoperation.

[Brief explanation of drawings]

FIGS. 1, 2, and 3 are cross-sectional views of embodiments of the present invention. FIGS. 4 and 5 are perspective views of a light source used in the present invention. FIG. 6 is a block diagram for explaining the present invention. Figure 7 is a flow chart according to the present invention Figure 8 is a block diagram according to the present invention Figures 9 (a) and 9 (b) are diagrams for explaining the present invention Figure 10 is an application of the present invention FIG. 11 is a cross-sectional view of the light source that forms the background of the present invention. In the figure, IO is a discharge tube, 11 is an electrode, and 12, 13, and 17 are shields.

Claims (2)

[Claims] (1) In a document reading device in which a lighting device relatively scans the document, the lighting device includes a discharge tube that generates visible light using a high-frequency electromagnetic field, and an electrode provided in contact with or near the wall of the discharge tube. , high frequency application means for applying high frequency to the electrode,
a first shield that covers the discharge tube and has an opening through which light passes; a second shield that covers the opening; the second shield covers the opening when the discharge tube is lit; A document reading device characterized in that an opening is opened when manipulating a document. (2) The document reading device according to claim 1, wherein the first shield is a reflection plate that guides light from the discharge tube toward the document side.