JPH05190151A - Electric discharge lamp for illuminating document - Google Patents

Abstract

PURPOSE:To prevent the unnecessary electric power consumption by installing plural pairs of electrodes in the axial direction on the outer surface of a glass bulb sealed with electric discharge gas and allowing the bulb to radiate by applying voltage only on an electrode corresponding to the width of rear-out document. CONSTITUTION:When the size of a document is small, a switch 6a is turned ON by a control circuit 7, and an inverter 4a as high frequency power source operates to apply each voltage to a pair of electrodes 3a and 3b, and electric discharge occurs. Then, the fluorescent body on the parts of the electrodes 3a and 3b radiates. While, if the size of the document is large, the switches 6a and 6b are turned ON by the circuit 7, and inverters 4a and 4b are operated to apply each voltage to the electrodes 3a, 3b and 3c, 3d, and electric discharge occurs, and the whole of an electric discharge lamp radiates. Accordingly, only the part corresponding to the width of the document can electric-discharge- radiate, and the unnecessary electric power consumption can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp used for illuminating a document such as a facsimile or a copying machine.

[0002]

2. Description of the Related Art Conventionally, in a device such as a facsimile, a fluorescent lamp has been mainly used as a discharge lamp for illuminating a document. For example, FIG. 3 is a perspective view of a conventional discharge lamp shown in Japanese Patent Publication No. 2-288151. 1 in the figure
Is a conventional discharge lamp, 2 is a glass bulb filled with a rare gas as a discharge gas, 3a and 3b are a pair of electrodes provided at both ends of the glass bulb, 8 is an external electrode provided outside the glass bulb, and 9 Is an insulating sleeve for fixing the joint between the external electrode 8 and the lead wire of the external electrode 8. Although not shown, a phosphor is applied to the inner surface of the glass bulb.

Next, the operation will be described. In the discharge lamp shown in FIG. 3, when a voltage is applied between the electrodes 3a and 3b, a discharge is generated and ultraviolet rays are generated accordingly. This ultraviolet light excites the phosphor layer on the inner surface of the glass bulb to generate visible light,
It is emitted from the glass bulb to the outside. The external electrode 8 plays a supplementary role of attracting the discharge generated between the electrodes 3a and 3b to the inner wall of the glass bulb and stabilizing the discharge.

[0004]

As described above, the conventional discharge lamp for illuminating an original document discharges and emits light between a pair of electrodes at both ends of the glass bulb, so that a constant power is always applied regardless of the width of the original document. In the case of a document that is consumed and has a narrow width, there is a problem that an unnecessary area is illuminated and power is consumed more than necessary.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a discharge lamp for illuminating a document which does not consume unnecessary power.

[0006]

In a discharge lamp for illuminating an original according to the present invention, a discharge gas is enclosed in a glass thin tube, and a plurality of pairs of electrodes are provided in the axial direction on the outer surface of the glass long tube for reading. A control circuit for applying a voltage to the electrodes according to the width of the original to emit light is provided.

[0007]

By selecting the electrodes to which a voltage is applied according to the size of the paper of the original by the control circuit, discharge is generated and light is emitted at the part to which the voltage is applied.

[0008]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of one embodiment, and FIG. 2 is a sectional view thereof. In the figure, 1 is a discharge lamp for illuminating a document of the present invention, and 2
Are elongated glass bulbs, 3a, 3b and 3c, 3d, which constitute a discharge lamp, and conductors as electrodes of a pair are arranged side by side in the axial direction of the outer surface of the glass bulb. 4a, 4b
Is an inverter which is a high frequency power source connected to a pair of electrodes via switches 6a and 6b. 7 is the above switch 6
a and 6b are operated and the inverters 4a and 4b are
It is a control circuit for operating b. The inner surface of the glass bulb is coated with the phosphor 5, and the glass bulb 2 is filled with 100 torr of xenon as a discharge gas. The width of the electrode is provided corresponding to the width of the original,
For A4 and A5 sizes, the electrode width is 3a and 3b is 1
It is suitable that 8 cm, 3 c and 3 d are about 6 cm.

The operation of the discharge lamp for illuminating a document having such a configuration will be described. When a voltage is applied between the pair of electrodes from the power source, a voltage is applied to the discharge space inside the glass bulb through the glass bulb which is a dielectric, and a discharge occurs. Ultraviolet rays generated at that time excite the phosphor layer, and visible light is generated.

Hereinafter, the principle of light emission will be described in detail. Since the discharge is performed through the glass which is the dielectric, the current is limited by the dielectric and the glow discharge does not evolve into the arc discharge. Further, the discharge is not concentrated at a specific place, and the discharge is generated from the entire inner surface of the glass bulb facing the external electrode. If the thickness of the glass is constant and the characteristics of the dielectric are uniform, the current density on the inner surface of the glass bulb facing the external electrode will be uniform, so the density of ultraviolet rays generated will also be substantially uniform. The generation of visible light is also almost uniform. Therefore, the luminance distribution on the lamp surface becomes almost uniform. In addition, the current flows only immediately after the polarity of the applied voltage is reversed, and otherwise the current is stopped by the accumulation of charges on the inner surface of the glass bulb. Therefore, a pulsed current flows through the lamp.

When the internal discharge state is observed in detail, the entire inner surface of the lamp facing the external electrode is covered with a substantially uniform light, and the thin thread-like discharge connecting the facing electrode is substantially constant. Many stripes are seen at intervals. When the rare gas is filled inside, the rare gas atoms are excited to the resonance level by collision with electrons by such discharge. Excited atoms at the resonance level collide with rare gas atoms at other ground levels to form excimers of diatomic molecules because the pressure of the rare gas is high. This excimer emits ultraviolet rays and returns to the two ground level noble gas atoms. The ultraviolet rays emitted by the excimer do not undergo self-absorption like the resonant ultraviolet rays of the atoms, so most of them reach the inner wall of the lamp and are converted into visible light by the phosphor.
That is, in the case of light emission by excimer, brighter light can be obtained.

When xenon is used as the rare gas, the glow discharge type lamp having electrodes inside has 14
In contrast to the large amount of 7 nm xenon resonance ultraviolet rays, this fluorescent lamp mainly emits ultraviolet rays of about 170 nm emitted by excimers. The long wavelength of ultraviolet rays is also advantageous in terms of the luminous efficiency and deterioration of the phosphor.

In the discharge lamp for illuminating a document, which has the above-described structure and light emission principle, when the size of the document is small, the switch 6a is turned on by the control circuit 7 to operate the inverter 4a which is a high frequency power source, and the electrode pair 3a, A voltage is applied to 3b to cause discharge. Along with that, electrode 3
The phosphors in portions a and 3b emit light.

On the other hand, when the document size is large, the control circuit 7
Switch 6a, 6b is turned on by the inverter 4a,
4b operates, a voltage is applied to the electrodes 3a, 3b and 3c, 3d to cause discharge, and the entire discharge lamp emits light.

In this embodiment, the case of two pairs of electrodes is shown, but by providing three or more pairs of electrodes, it is possible to cope with a larger width of the original. Further, in this embodiment, the inverters corresponding to the respective electrode pairs are connected, but one inverter may be used and its output may be supplied only to the required electrode pairs by a switching element such as a transistor. ..

In the above embodiment, 100T of xenon is used.
Although the discharge lamp of excimer light emission sealed at a high pressure of about orr has been described, it goes without saying that it can be applied to an external electrode type discharge lamp in which mercury or discharge gas is sealed at 20 Torr or less and a voltage is applied from the outer surface of the glass bulb.

[0017]

Since the present invention is constructed as described above, it has the following effects.

Since only the portion corresponding to the width of the document is discharged and emitted, unnecessary power is not required.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of FIG.

FIG. 3 is a perspective view showing a conventional discharge lamp.

[Explanation of symbols]

 1 Document Discharge Lamp 2 Glass Bulbs 3a, 3b, 3c, 3d Electrodes 4a, 4b, Inverter 5 Phosphor 7 Control Circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H05B 41/36 Z 9032-3K // H05B 41/16 Z 9249-3K (72) Inventor Junichiro Hoshizaki 2-14-40 Ofuna, Kamakura City Mitsubishi Electric Corporation Life Systems Research

Claims (1)

[Claims] 1. A glass thin tube is filled with a discharge gas, a plurality of pairs of electrodes are provided in the axial direction on the outer surface of the glass long tube, and a voltage is applied to the electrodes according to the width of the read document to emit light. Discharge lamp for illuminating documents, characterized by having a control circuit