JPH05121048A - Lighting device - Google Patents

Abstract

PURPOSE:To provide a stable lighting device in which a quantity of light is irrespective of an environmental temperature or a lighting system by which a lamp can be light up/put out instantly as well as to provide an integrated compact lighting system by which three primary color emission becomes possible and emission control can be carried out independently. CONSTITUTION:An negative electrode 1 to emit electrons, a positive electrode 6 to impress voltage upon the negative electrode 1 and a phosphor 7 formed in the vicinity of the positive electrode 6 are provided in a closed vacuum cavity. In this lighting system, a back electrode 4 is provided in the vicinity of the negative electrode 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to an image scanner, a digital copying machine, which is used when reading an image.
The present invention relates to a lighting device for an image input device such as a facsimile.

[0002]

2. Description of the Related Art A sensor such as a one-dimensional array CCD is used for reading an image scanner, and it is the most popular reading method capable of forming an inexpensive, compact and high-resolution device. The illumination device of this type of image input device needs to illuminate the image in the arrangement direction of the photoelectric conversion elements, and uses an LED array, a fluorescent lamp, a line halogen lamp, or the like. In particular, fluorescent lamps are excellent in luminous efficiency and color rendering, and are frequently used as illumination devices for image input devices. Also in color image input devices, color image scanners using three fluorescent lamps each emitting three primary colors have become widespread.

[0003]

However, in the fluorescent lamp of the prior art, the vapor pressure of the mercury enclosed in the fluorescent lamp largely fluctuates with respect to temperature, so that the light quantity fluctuates greatly with respect to the ambient temperature. was there. Further, in the fluorescent lamp, the amount of light obtained is limited, and the optimum tube diameter of the lamp is about 40 mm, which makes it difficult to make it compact.

Therefore, the present invention solves such a problem, and an object of the present invention is to provide a stable lighting device in which the amount of light is not related to the ambient temperature. Moreover, it aims at providing the illuminating device which can turn on and off the lamp instantly. Moreover, it aims at providing the illuminating device which can emit three colors with a compact structure.

[0005]

In order to solve the above-mentioned problems, an illumination device of the present invention comprises a cathode that emits electrons, an anode that applies a voltage to the cathode, and the vicinity of the anode in a sealed vacuum cavity. And a back electrode provided in the vicinity of the cathode. Further, it is characterized in that the cathode and the back electrode are integrated with each other with the insulator interposed therebetween. Further, it is characterized in that at least three kinds of phosphors are integrally formed, and at least three pairs of cathode and back electrode are arranged corresponding to each phosphor. Further, it is characterized in that a U-shaped deflection electrode is arranged so as to surround the cathode.

[0006]

When a current is applied to the cathode placed in a closed vacuum cavity and a high voltage is applied to the anode with respect to the cathode, thermoelectrons are emitted from the cathode. Visible light is emitted when the thermoelectrons strike and excite the phosphor. If a negative voltage is applied to the back electrode, the amount of thermoelectrons emitted can be controlled. Further, by setting the deflection electrode provided near the cathode to the same potential as the cathode, it becomes possible to control the emission width on the phosphor according to the opening width of the back electrode. Further, by independently applying a negative voltage to the back electrodes provided corresponding to the three types of phosphors, the emission of any phosphor can be controlled at high speed.

[0007]

1 is a perspective view of a lighting apparatus showing a first embodiment according to the present invention, and FIG. 2 is a sectional view taken along the line AA 'in FIG. Details of the configuration will be described with reference to the drawings. The cathode 1 is
For example, ruthenium oxide is 10μm by screen printing
Is applied to the surface of the insulating material 3 such as a glass plate or ceramic. The surface is covered with an emitter 2 such as barium oxide in order to enhance the thermionic emission efficiency. On the surface of the insulating material 3 opposite to the surface on which the cathode 1 is coated, a back electrode 4 made of a conductive material such as aluminum is formed by a vapor deposition method or the like. Back electrode and cathode 1
The distance L_back with respect to each other, that is, the thickness of the insulating material 3 is about 0.1 mm.

On the lower surface of the upper plate 5 made of transparent glass,
The phosphor 7 is applied in a strip shape by screen printing or the like. The material of the phosphor is a phosphor capable of cathodoluminescence, for example, ZnS: Cu as a phosphor for green,
Al may be mentioned. 1 of this phosphor powder by a sedimentation method or the like
It is evenly coated at a rate of 10 mg / cm ² , and an anode 6 made of aluminum is formed thereon by vacuum vapor deposition to a thickness of 0.1 to 0.4 μm.

The deflection electrode 5 is made of a conductive and non-magnetic material such as brass and aluminum, and is arranged by bending it in a U-shape. The light emitting region on the phosphor surface is substantially determined by the U-shaped opening width W of the deflection electrode 5. For example, when the green deflection electrode 5 having an opening with a width of 2 mm is used, the light emitting area of the phosphor 7 is 2 mm.

As shown in FIG. 2, the above-mentioned component parts include an upper plate 5 coated with a phosphor 7 and side plates 10-a, 10-.
b, the bottom plate 9, and the side plates 10-c and 10-d shown in FIG. 1 form a vacuum cavity 20, and the vacuum degree is set to a vacuum degree of minus 5 to minus 8 torr. The material of the upper plate 5 is a transparent material, for example, lead glass.

Next, the lighting operation will be described. FIG. 3 is a lighting circuit diagram of the lighting device according to the present invention shown in FIG. The anode 6 has a DC voltage E of 5 to 30 kv, optimally 10 kv.
a is applied. A voltage Ec is applied to the cathode 1, and an emitter 2 applied to the surface of the cathode 1 by Joule heat
Is heated. Further, thermoelectrons are extracted from the surface of the emitter 2 by the electric field generated by the anode voltage Ea and accelerated toward the anode 6.

At the time of lighting, the control signal of the CTL section is High.
Then, the transistor Tr is turned on, and the potential of the back electrode 4 becomes substantially the same as that of the ground, that is, the cathode 1. Cathode 1
The thermoelectron stream emitted from the anode 6 is accelerated to the anode 6,
To excite the phosphor 7. When not lit, CTL
The control signal of the part becomes Low, the transistor Tr is turned off, and the potential of the back electrode 4 becomes Eb. As a result, the flow of thermoelectrons from the cathode 1, that is, the anode current is affected.
If an appropriate negative applied voltage Eb is selected, the anode current will be completely zero. According to the experiment, the gap La between the cathode 1 and the anode 6
When c was 30 mm, the anode voltage was 10 kV, and the gap Lb between the cathode 1 and the green deflection electrode 5 was 0.1 mm, the back electrode voltage Eb at which the anode current became zero was -40 V. The back electrode voltage Eb can be controlled at a lower voltage as the gap Lb between the cathode 1 and the back electrode 2 is smaller.

The formula for obtaining the back electrode voltage required to cut the cathode current from the calculation of the electric field strength is as follows.

[0014]

[Equation 1]

Since the light emission of the present invention is based on cathodoluminescence, there is almost no change in the light amount due to changes in the ambient temperature, and the change in the light amount from -20 to 60 degrees is 5% or less. In addition, the startability at the start of lighting is excellent, and the light output is stable within a few milliseconds after lighting. Furthermore, since the amount of light emitted from the phosphor is proportional to the current density, it is very easy to adjust the amount of light emitted, and it is possible to construct a lighting device with a wide light output from a light source with a large output to a light source with a small output.

Further, the lighting device according to the present invention can be turned on and off at an extremely high speed by controlling the back electrode voltage. The electronic control method of the present invention is the same electric field control as electronic control of a vacuum tube. Therefore, the response speed of turning on and off the phosphor can be set to about microsecond.

Further, as shown in Equation 1, the thickness Lb of the insulating material 3 is
The thinner E, the lower the voltage Eb of the back electrode can be. Therefore, the constituent electronic components of the electric circuit for controlling lighting can be made compact and the price can be reduced. Further, when the voltage Eb of the back electrode is fixed, the thinner the thickness Lb of the insulating material 3, the smaller the Lac can be made. That is, the entire length of the lighting device can be made smaller.

FIG. 4 is a main sectional view of an illuminating device showing a second embodiment of this embodiment. Three sets of cathode units 10-G, 10-R, and 10-B each including the emitter 2, the cathode 1, the insulating material 3, and the back electrode 4 shown in FIG. 2 are arranged. The deflection electrodes 51 are electrically connected to all three sets in the E shape.

Next, the lighting operation will be described. FIG. 5 is a lighting circuit diagram of the lighting apparatus according to the present invention shown in FIG. The emission control of the green phosphor 4G will be described as an example. A DC voltage Ea of 5 to 30 kv, optimally 10 kv, is applied to the anode 6. A voltage Ec is applied to the cathode of the green cathode unit 10-G, and thermoelectrons generated by heat generation by Joule heat are drawn to the anode 6 and accelerated by the electric field generated by the anode voltage Ea.

When the green color is lit, the control signal of the CTL-G section becomes High, the transistor Tr-G is turned on, and the potential of the back electrode of the green cathode unit 10-G becomes the ground. As a result, the thermoelectron flow emitted from the cathode unit 10-G is accelerated to the anode 6, passes through the anode 6, and the phosphor 4 is discharged.
Excite G. The light emitting region on the phosphor surface is determined by the U-shaped opening width W of the deflection electrode 51 as described above.
When it is not lit, the control signal becomes Low in the CTL-G section, the transistor Tr-G is turned off, and the green cathode unit 10
The potential of the -G back electrode is Eb. As a result, the flow of thermoelectrons from the cathode of the green cathode unit 10-G is shut out.

By controlling the above-mentioned lighting operation in the same manner for the emission of other phosphors, the emission of the three kinds of phosphors can be independently controlled. Therefore, unlike a general fluorescent lamp, it is possible to provide a lighting device having a compact structure and capable of emitting light in three primary colors. It is effective to vapor-deposit a thin film on the inner surface of the vacuum cavity 20 so as to prevent it from being affected by an electromagnetic field from the outside and to prevent the electromagnetic field from being generated outside.

By using the illuminating device according to the present invention, it is possible to obtain an illuminating device in which the light source is excellent in startability and a stable light quantity can be obtained at the same time as starting. By using this as an illumination device of an image reading device, it becomes possible to obtain an output faithful to the density value of the image to be read.

Further, in the embodiment according to the present invention, the cathode luminescence at 5 kV or more is used to enhance the light emission efficiency, but it is also possible to use the light emission at 5 kV or less.

[0024]

As described above, according to the present invention, there is an effect that it is possible to provide a stable lighting device in which the amount of light is independent of the ambient temperature. Further, it is possible to provide an illuminating device capable of instantaneously turning on and off the lamp. Furthermore, it is possible to provide an integrated and compact lighting device capable of emitting light in three primary colors and independently controlling light emission.

[Brief description of drawings]

FIG. 1 is a perspective view of a lighting device according to a first embodiment of the present embodiment.

FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG.

FIG. 3 is a lighting circuit diagram of the lighting device showing the first embodiment according to the present invention.

FIG. 4 is a main sectional view of a lighting device according to a second embodiment of the present invention.

FIG. 5 is a lighting circuit diagram of a lighting device showing a second embodiment according to the present invention.

[Explanation of symbols]

 1 Cathode 3 Insulating Material 4 Back Electrode 6 Anode 7 Phosphor

Claims (4)

[Claims] 1. A sealed vacuum cavity is composed of a cathode that emits electrons, an anode that applies a voltage to the cathode, and a phosphor formed near the anode, and a back electrode is provided near the cathode. A lighting device characterized by the above. 2. The illuminating device according to claim 1, wherein the cathode and the back electrode are integrally formed with an insulator interposed therebetween. 3. The phosphor according to claim 1, wherein at least three types of phosphors are integrally formed, and at least three pairs of a cathode and a back electrode are arranged corresponding to each of the phosphors. Lighting equipment. 4. The illumination device according to claim 1, wherein a U-shaped deflection electrode is arranged so as to surround the cathode.