JPS6168849A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To achieve adequate luminous intensities for the blue, the red and the near ultraviolet regions and almost equalize the optical outputs of these three regions by charging the emitter tube with specific amounts of a sodium, a cesium and a thallium halide in addition to mercury and a rare gas. CONSTITUTION:An emitter tube 1 is charged with a sodium, a cesium and a thallium halide in addition to mercury and a rare gas. The amounts of a sodium halide, a cesium halide and a thallium halide are adjusted to 2-12mg, 0.4-2.4mg and 0.4-3mg per 1cm<3> internal volume of the emitter tube 1 respectively. The ratio by weight of the sodium halide to the thallium halide is adjusted to 3-8. And accordingly, a metal halide lamp having almost equally high optical outputs for the blue, the red and the near ultraviolet regions can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention is directed to the improvement of metal halide lamps that emit light strongly in the blue region, red region, and near-infrared region.

[Background of the invention]

Near-infrared light sources are used as light sources for optical character reading devices and graphic recognition devices.

Conventionally, halogen light bulbs (for example, Japanese Patent Application Laid-open No. 55-46211) have been used as such light sources, but halogen light bulbs have a light output in the blue region that is lower than that in the red and near-infrared regions. Because it is quite small, it has the disadvantage of non-uniform light output as a light source that uses the three regions of blue, red, and near-infrared at the same time, and the light output of the blue region is small compared to the input. There is.

[Purpose of the invention]

Therefore, the object of the present invention is to provide sufficiently high emission intensity in three regions: blue region, red region, and near-infrared region.

Another object of the present invention is to provide a metal halide lamp that has substantially uniform light output in the three regions.

[Summary of the invention]

In order to achieve the above object, the present invention provides a metal halide lamp having an arc tube in which electrodes are sealed at both ends and halides of sodium, cesium, and thallium are sealed in addition to mercury and a rare gas. , the amount of sodium halide enclosed is the inner volume of the arc tube 1
Adjust the amount of cesium halide to 2 to 12 mg per cm (0, 4 to 2, 4 mg per cm).
and the amount of thallium halide enclosed is the same < 1 cm'
The metal halide lamp is characterized in that the metal halide lamp is 0.4 to 3 mg per filler, and the weight ratio of the amounts of sodium halide and thallium halide is 3 to 8.

This characteristic configuration of the present invention makes it possible to provide a metal halide lamp that has large light output in the blue region, red region, and near-infrared region, and has approximately the same light output.

As a result, by using such a metal halide lamp as a light source of a character reading device, the performance of the device can be improved.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail by way of examples.

FIG. 1 shows the basic structure of a metal halide lamp according to the present invention. In the figure, an arc tube 1 with electrodes sealed at both ends is fixed to an outer tube 2 by a support plate 3 and a support rod 7. The external electrode lead wire 4 of the arc tube 1 is connected to the external electrode lead wire 6 of the outer tube 2 via molybdenum fi5.
electrically connected to. Luminous tube 1 has an inner diameter of 0.6cm
, made of quartz glass with a distance between electrodes of 8 cm. Inside it, there is a rare gas for starting and an internal volume of 1 cm3 of 1 arc tube 1.
Each tube contains 2.5 mg of mercury, 8 mg of sodium iodide, 1.6 mg of thallium iodide, and 1.6 mg of cesium iodide. This metal halide lamp with luminescent tube 1 has an input of 200W when lit horizontally.
1 in each of the blue region, red region, and near-infrared region.
A light output of 5W was obtained.

In addition, various experiments and studies were conducted on metal halide lamps other than the above-mentioned examples, and it was found that the amount of fillers to be filled in the arc tube 1 was as follows: In addition to an appropriate amount of rare gas and mercury for starting, 2 to 12 mg of sodium halide per 1 cm' of internal volume.

It was found that the cesium halide should be in the range of 0.4 to 2'4 mg, and the thallium halide should be in the range of 0.4 to 3 mg. The reason for this is that if the amount of sodium halide enclosed is less than 2 mg-cm-3, the vapor pressure of sodium will not be sufficiently high, and as a result, although the luminescence in the red region will be strong, the luminescence in the near-infrared region will be small, which is not desirable. do not have. If this amount exceeds 12 mg-cm-', unevaporated sodium from the enclosed sodium will become liquid and cover the inner wall of the tube during lighting, which will have a significant negative impact on the lamp's life characteristics. This is undesirable because it causes

In addition, the amount of cesium halide enclosed is 0.4 m g'
When it is less than cm-3, cesium atoms ionized in the arc diffuse toward the wall, resulting in a shortage of cesium atoms at the center of the arc, which cannot effectively cover the arc current, resulting in light emission in the near-infrared region. This is undesirable because the excited sodium atoms that occur are also ionized and the light emission of sodium in the near-infrared region is suppressed. And this enclosed amount is 2.4 m
Even if it exceeds g -cm-', the emission intensity in the near-infrared region is already saturated, so there is no effect, and expensive cesium halide is wasted, and the temperature of the arc decreases.

This is undesirable because the luminescence of thallium is suppressed.

In addition, the amount of thallium halide enclosed is 0.4mg ”c
If it is less than m-3, the vapor pressure of thallium will not be sufficiently high, and as a result, the emission of light in the blue region by thallium will become weak. If the enclosed amount exceeds 3 mg "Cm-", the vapor pressure of the thallium halide is too high and the arc becomes narrow, making the discharge unstable and undesirable.

Furthermore, it is desirable that the weight ratio of sodium halide to thallium halide in the contents filled in the arc tube is 3 to 8. The reason for this is that if the above-mentioned enclosed weight ratio is less than 3, the ratio of the luminescence intensity in the near-infrared region to the luminescence intensity in the blue region will be 0.9 or less, and the light output will become non-uniform. and,
When this enclosed weight ratio exceeds 8, the ratio of the luminescence intensity in the near-infrared region to the luminescence intensity in the blue region becomes 1.1 or more,
The optical output in each of the three wavelength ranges becomes non-uniform, which is undesirable.6
[Effects of the Invention] As described above, the present invention has made it possible to obtain a metal halide lamp which has an extremely large light output in the blue region, red region, and near-infrared region, and in which the light output in each of these regions is almost uniform. .

As a result, the performance of an optical character reading device using a metal halide lamp as a light source according to the present invention can be dramatically improved.

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram of a metal halide lamp according to the present invention. 1... Arc tube, 2... Outer tube, 3... Support plate, 4,
6...External electrode lead wire, S...Molybdenum foil, 7
...Support rod.

Claims (1)

[Claims] 1. Electrodes are sealed at both ends, and mercury is included as a filler.
In a metal halide lamp having an arc tube in which halides of sodium, cesium, and thallium are sealed in addition to a rare gas, the amount of the sodium halide enclosed is 2 to 12 mg per 1 cm^3 of the internal volume of the arc tube, and the above-mentioned The amount of cesium halide enclosed is 0.4 to 2.4 mg per 1 cm^3 of the inner volume of the arc tube, and the amount of thallium halide enclosed is 1 cm^3 of the inner volume of the arc tube.
0.4 to 3 mg per 3, and the weight ratio of the amount of the sodium halide and thallium halide is 3
A metal halide lamp characterized by having a temperature of ~8.