JP2729995B2 - Fluorescent lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to illumination of an original such as a copying machine, which illuminates the original in a slit shape and exposes the slit-illuminated original surface via a lens system. The present invention relates to a fluorescent lamp used when projecting onto a paper or a photosensitive drum, and further relates to a fluorescent lamp directly disposed near a document surface or an irradiated surface. [Prior art and its problems] Fluorescent lamps are being widely used in various applications including the above-mentioned industrial fields because of their low power consumption and excellent luminous efficiency. These applications require a large amount of light anyway, but fluorescent lamps that emit the required amount of light with low power consumption by being lit with high-frequency power have been put to practical use. Fluorescent lamps have a phosphor coated on the inner surface of the arc tube, but the light emitted from the phosphor is more radiated into the arc tube than light emitted outside the arc tube. The interior is very bright. For this reason, in the case of a linear light source, an aperture portion is formed without applying a fluorescent substance to an elongated portion of the inner surface of the arc tube along the tube axis direction, and light in the arc tube is emitted from the aperture portion. Has been done. By the way, when a linear fluorescent lamp is used as an illumination light source for a copying machine or the like, the irradiance distribution on the illumination surface of the lamp tube surface is reduced because the amount of light at both ends of the fluorescent lamp is reduced.
The central part was large and the parts near both ends were small. When such an irradiation surface is imaged by a SELFOC lens array (trade name), the illuminance of the imaging surface near both ends is naturally low, and the image is projected on the surface to be irradiated by a normal optical lens system. In this case, there is a problem that the peripheral portion becomes darker on the surface to be illuminated in accordance with the "cosine fourth power rule". In order to solve this, it is necessary to increase the amount of light at both ends than at the center and to make the illuminance on the surface to be irradiated a predetermined distribution. Therefore, for example, along the longitudinal direction of the fluorescent lamp, between the illumination light source and the surface to be illuminated, a dimming means having a narrow opening at the center and a wide opening at both ends is provided by the dimming means. The light amount was being adjusted. In some cases, a fluorescent lamp whose discharge path length is much larger than the width of the original is used to suppress a decrease in illuminance at the end of the original. However, these methods do not effectively use the amount of light emitted from the illumination light source, and require a volume occupied by the dimming means, or have a disadvantage that a fluorescent lamp that is longer than necessary is used. When such a light source is incorporated into a small and lightweight device, the functionality of the device has been significantly impaired. [Object of the Invention] The present invention has been made in view of such circumstances,
The purpose is to provide a fluorescent lamp having a long effective emission length even if the overall length of the lamp is short, which is suitable for being incorporated into a small and lightweight device, and which can provide a predetermined distribution of illuminance on an irradiated surface. It is to provide a new fluorescent lamp. [Configuration of the invention and its operation] To achieve the above object, the fluorescent lamp of the present invention is:
A pair of internal electrodes are arranged at both ends of the inside of the tube-shaped arc tube, and a phosphor is applied to the inner wall of the arc tube except for a linear aperture portion along the tube axis direction, and the outer surface of the arc tube facing the aperture portion Are provided with a plurality of third electrodes connected to a power supply, and a reflective film insulated from the third electrodes is provided at a predetermined position on the wall surface of the portion of the arc tube to which the phosphor is applied. That is, when a plurality of third electrodes connected to the power supply are arranged at predetermined positions facing the aperture portion on the outer surface of the tubular valve, the glass constituting the tubular valve is a derivative, and thus acts as a capacitor, and the third electrode functions as a capacitor. In the vicinity of the disposed inside, accumulation and divergence of ions and electrons in the plasma occur according to the frequency. That is, since the barrier discharge occurs, the density of ions and electrons increases, and the luminance of that portion relatively increases. Since the reflective film insulated from the third electrode is provided, the brightness of the aperture portion facing the third electrode increases. Therefore, by appropriately designing the positions and lengths of the plurality of third electrodes and the reflective film, a predetermined luminance distribution can be obtained, and a fluorescent lamp having a luminance distribution according to the purpose of use can be obtained. FIG. 1 is an explanatory view of a fluorescent lamp for reading an image, in which a pair of electrodes 2a and 2b connected to a high-frequency power supply 1 are connected to a tube-shaped light emitting tube 3 having a discharge path formed in a straight line. At both ends inside. Then, third electrodes 4a and 4b, that is, a plurality of third electrodes are arranged on the outer surface of the linear portion surrounding the discharge path of the arc tube 3 and near the electrodes 2a and 2b. . The third electrodes 4a and 4b are formed of a single elongated strip-shaped electrode plate, and the third electrode 4a and 4
Although divided into 4b, each may be constituted by an independent electrode plate. Further, reflection films 9a and 9b are provided on the wall surface of the arc tube 3 on which the third electrodes 4a and 4b are arranged. The reflection films 9a and 9b may be provided on either the outer surface or the inner surface of the arc tube 3. As shown in FIG. 2, the inner surface of the arc tube 3 is coated with the phosphor 5, but the linear aperture 6 is not coated with the phosphor 5 in the tube axis direction of the arc tube 3.
Are formed, and the third electrodes 4 a and 4 b are arranged at positions facing the aperture section 6. The reflection films 9a and 9b are provided in portions other than the aperture section 6, and are insulated from the third electrodes 4a and 4b. This is because the discharge becomes unstable if conducting. In addition,
7a, 7b, 7c are capacitors, and in the illustrated example, electrodes 2a, 2b
Although the and the third electrodes 4a and 4b are connected to the same high-frequency power supply 1, they may be connected to separate high-frequency power supplies. Next, as a specific numerical example, the outer diameter of the tubular arc tube 3 is 4.1 mm and the length of the discharge path, that is, the distance between the electrodes 2a and 2b is 63.5 m.
m, and 20 ktor of krypton gas (2
5 ° C.) and Zn ₂ Si as phosphor 5
O ₄ : Mn is applied, and the width of the aperture 6 is 2.4 mm
It is. High-frequency power having a frequency of 50 KHz is applied between the electrodes 2a and 2b. The voltage is 495 V, the discharge current is 10 mA, and the power consumption is about 5 W. On the other hand, the third electrodes 4a and 4b have a width of 1.5
An aluminum foil having a thickness of 1 mm was adhered to the outer surface of the arc tube, and the length of each was 11.5 mm, and it extended 9.5 mm toward the center from the tips of the electrodes 2a and 2b. And
The high-frequency power source 1 is connected via a capacitor 7c having a capacitance of 25 pF.
Connect to The capacitor 7 connected to the electrodes 2a and 2b
The capacitance of both a and 7b is 110 pF. And the third electrode 4
The amount of electricity supplied to a, 4b is about 2.2 W, and therefore, in this embodiment, the total power consumption is about 7.2 W.
A little less than 30% of the electricity input to a and 4b. The amount of electricity supplied to the third electrodes 4a, 4b can be changed by changing the output of the high frequency power supply 1. Reflective films 9a, 9b
Is mainly composed of magnesium oxide, titanium oxide or the like, but may be any as long as it has excellent reflection characteristics. In the present embodiment, the reflection films 9a and 9b
Is equal to the length of the third electrodes 4a and 4b, so that they match. The luminance distribution of the fluorescent lamp was measured. To measure the luminance distribution, a photo guide with a slit width of 0.5 mm at the tip was brought into contact with the aperture section 6 and this photo guide was measured for 1 m.
The light from the aperture section 6 was guided to the light receiver while moving at an m pitch, and the output of the photodiode of the light receiver was recorded. Further, as a comparative example, the luminance distribution of a fluorescent lamp having neither the third electrode nor the reflective film was measured. The results are shown in FIG. 3. In FIG. 3, the maximum luminance of each of the two fluorescent lamps is indicated by a relative value with 100 being the maximum luminance. As can be understood from this, the portion where the third electrodes 4a, 4b and the reflection films 9a, 9b are provided has the highest luminance, and the third electrodes 4a, 4b
The luminance is higher by about 30% than in the central part where 4b and the reflective films 9a and 9b are not provided. On the other hand, in the comparative example in which the third electrodes 4a and 4b and the reflective films 9a and 9b are not provided, the luminance distribution is almost flat, and the luminance distribution is constant. The brightness of the portion where the third electrodes 4a, 4b and the reflection films 9a, 9b are arranged can be adjusted by changing the size of the third electrodes 4a, 4b and the reflection films 9a, 9b and the capacitance of the capacitor 7c. it can. Therefore, even in the case where a large amount of light is required at both ends than at the center, such as a lamp for illuminating a document of a copier, the illuminance distribution on the illuminated surface, which is a photoelectric conversion surface, can be achieved without using light control means. Can be made uniform. Therefore, the utilization rate of the radiated light is high, and the length of the discharge path can be used almost as the illuminated area. Therefore, it is necessary to use a fluorescent lamp that is longer than necessary as in the related art. Is also gone. For this reason, not only a convenient fluorescent lamp can be provided as a small and lightweight fluorescent lamp, but also an excellent fluorescent lamp for an optical machine employing a slit exposure illumination system such as a copying machine. Further, as in the present embodiment, the reflection films 9a and 9b and the third electrode 4
a, 4b does not necessarily have to match, the third electrode 4a, 4
Reflection films 9a and 9b are also provided in parts where b is not arranged,
Conversely, the third electrodes 4a, 4b may be arranged in portions where the reflection films 9a, 9b are not provided, and the luminance distribution can be arbitrarily changed by a combination of the two, so that not only the copying machine but A fluorescent lamp having a luminance distribution according to the purpose can be obtained. [Effects of the Invention] As described above, according to the present invention, in a fluorescent lamp having a linearly long aperture, the radiation intensity of light can be arbitrarily changed along the longitudinal direction. The required illuminance distribution required in the surface in the longitudinal direction of the fluorescent lamp can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of an embodiment of the present invention, and FIG.
FIG. 3 is a cross-sectional view taken along the line II, and FIG. 3 is an explanatory diagram of a luminance distribution. 1 high frequency power supply, 2a, 2b power supply 3 light emitting tube, 4a, 4b third electrode 5 phosphor, 6 aperture part 9a, 9b reflection film

   ────────────────────────────────────────────────── ─── Continuation of front page                   (56) References JP-A-62-281256 (JP, A)                 JP-A-63-141256 (JP, A)                 JP-A-63-58752 (JP, A)                 Tokiko Hei 7-27773 (JP, B2)

Claims (1)

(57) [Claims] Placing a pair of internal electrodes at both ends inside the tube-shaped arc tube,
On the inner wall of the arc tube, a phosphor is applied except for a linear aperture portion along the tube axis direction, and a plurality of third electrodes connected to a power source are provided on the outer surface of the arc tube facing the aperture portion, A fluorescent lamp, characterized in that a reflection film insulated from the third electrode is provided at a predetermined position on a wall surface of a portion of the arc tube to which the phosphor is applied.