JP2001236923A - Xenon arc lamp with reduced electromagnetic interference - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a xenon arc lamp with reduced emission of electromagnetic interference wave and improved lifetime of the lamp. SOLUTION: An improved arc lamp is equipped with a body made of a ceramic, an anode made of wolfram, a cathode disposed facing the anode, and an inner space filled with xenon gas. The anode 300 is provided with a curved face 312 that is for connecting its tip region 310 and shoulder region 308 smoothly with a rounded shape and that functions to stabilize the arc in operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to arc lamps and, more particularly, to devices and methods used to extend the noiseless operating life of arc lamps.

[0002]

2. Description of the Related Art Short wavelength arc lamps are powerful spots that can accumulate light within a reflector in applications such as medical endoscopes, instrumentation and video lighting. Bring the light source. The short-wavelength arc lamp is also used in an industrial endoscope, for example, for inspecting the inside of a jet engine.
In recent years, it has also been applied to color television receiver projection systems. All such applications must comply with certain electromagnetic emission standards set forth in the United States by the Federal Communications Commission.

[0003] A typical short wavelength arc lamp includes an anode and a cathode having a sharp tip. The anode and cathode are arranged along the longitudinal axis of a cylindrical and sealed concave chamber. Xenon is sealed in the chamber at a pressure of several atmospheres. As of February 24, 1998
U.S. Pat. No. 5,721,465 to Roy D. Roberts discloses such a typical short wavelength arc lamp. This lamp produces a large level of electro-magnetic interference when an arc is formed between the cathode and anode electrodes.
nterference, EMI).

[0004] Over time, the relatively sharp tip of the cathode tends to wear and become less sharp. For this reason,
Electric arcs are formed and contact on many different spots on the anode surface. Prior art anodes had sharp shoulders to keep the arc away. Whenever an arc is formed at a new spot on the anode surface, suddenly large radio interference is emitted. The conventional solution is to replace the lamp with a new good lamp. In fact, due to EMI problems, the useful life of the lamp has been less than 200 hours. This is because the resulting interference can disrupt other important circuits in the application.

[0005]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a xenon arc lamp with reduced EMI emissions.

It is another object of the present invention to provide a xenon arc lamp with improved lamp life.

[0007] In summary, an embodiment according to the present invention comprises a ceramic body, a tungsten anode supported by a base, a cathode suspended by a support system and opposed to the anode, The present invention relates to an improvement of an arc lamp having an internal space containing xenon gas. The focus of the improvement is on reducing electromagnetic radiation, such as occurs at small lamp currents, and extending lamp life. Electromagnetic radiation is controlled by both rounding the anode electrode head and increasing the operating temperature of the anode electrode head.

An advantage of the present invention is that a lamp is provided that operates quieter for a much longer time than lamps of conventional construction.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects and advantages of the invention will be apparent from the following detailed description of the preferred embodiments, read in conjunction with the accompanying drawings.
It will be clear to the skilled person.

FIG. 1 is a view showing an embodiment of a short wavelength xenon arc lamp according to the present invention.
00 is attached. The lamp 100 includes a stem 103 supported by a tripod suspension support system 104.
Having a cathode 102 and a neck portion 10 for preventing heating
7 with ceramic body 7 and ceramic body 1
08, an elliptical reflecting surface mirror 110, a lens 112 made of sapphire, and a base 114 made of copper. The interior space 116 is filled with xenon gas. A conical window sleeve 118 supports the lens 112.

The head of the anode 106 is a rounded head, as is characteristic of the present invention. The neck 107 is empirically sized to allow for an appropriate operating temperature at the arc interface. The anode is usually made of tungsten, the base is made of copper, and all heat sinks are made of aluminum. Generally, the neck 107
Is thin enough that the temperature of the round head of the anode during operation can rise so that EMI emissions are sufficiently avoided. However, also in order to be able to extend the useful life of the lamp, the neck 10
7 must be thick enough so that the temperature of the round head does not rise too high so as not to melt or sublime the tungsten. A thicker neck can provide a wider passage for the accumulated heat to escape to the heat sink. At very high temperatures, the tungsten evaporates and blows out, thereby causing cooling, depositing on mirror reflectors and lens surfaces, and darkening the lamp.

[0012] There is an operating current threshold, above which current the EMI generated by the lamp is usually eliminated. A problem arises if such a threshold increases over the normal operating time of the lamp. The large cathode-anode electrode current stabilizes the arc and prevents the arc from jumping across the electrode surface. Regarding lamps, such as for example the lamp proposed by Roy D. Roberts in U.S. Pat. No. 5,721,465,
Experiments were performed on the EMI threshold versus operating time. For the new lamp, the threshold was 16.8 amps. After 50 hours of use, the threshold is 1
It rose to 9.5 amps. After 300 hours of use, the lamp was noisy at all current values below 20.2 amps. In the four test units constructed according to embodiments of the present invention, the current threshold for low noise operation did not exceed 14.1 amps for an elapsed time of 0-300 hours.

Some advantages of the present invention can be realized by simply cutting the neck of the anode of a standard arc lamp. This is shown in FIG. 2 where the tungsten anode 200 is shown.
Has a diameter of 4.724 mm (0.4 mm) in some applications.
186 inches). The neck portion 202 has a length of 2..
718 mm (0.107 inch) and a diameter of 2.
It is formed to be 540 mm (0.100 inch). The neck part 202 separates the head part 204 and the stem part 206. The head portion 204 has a shoulder portion 208 which is formed sharply and sharply as in the related art.
And a flat upper surface 210. Neck 20
It has been observed in experiments that relatively small changes in 2 can cause large fluctuations in the operating temperature of the head section 204. Although the use of anode 200 improves noiseless operation, some stray arcs still tend to propagate along shoulder edge 208 and the outer edge of flat top surface 210.

All the advantages of the present invention can be realized by both cutting the neck of the arc lamp anode and rounding the head. This is shown in FIG. 3, where the diameter of the tungsten anode 300 is 0.1724 inches in one application. The neck portion 302 has a length of 2.718 mm (0.1
07 inches) and a diameter of 2.540 mm (0.1
00 inches). The neck portion 302 separates the head portion 304 and the stem portion 306. The head portion 304 has a shoulder portion 308 that is smoothly rounded and a tip portion 310 that is rounded. For example, the radius (curvature radius) of the shoulder portion 308
Is 0.508 mm (0.02 inch), and the radius (curvature radius) of the tip 310 is 1.854 mm (0.
0.073 inches). The curved surface (or conical surface) 312 is approximately 1.854 from the main portion of the head portion 304.
mm (0.073 inch).

With respect to the anode 300, the neck 30
2 that a relatively small change in shape can cause large fluctuations in the operating temperature of the head section 304;
Observed in experiments. In the anode 300,
Noiseless operation is greatly improved, and once formed, the arc tends to remain in place.

In general, one embodiment of the present invention is a xenon arc lamp that has a long operating life and reduced electromagnetic interference (EMI) emissions. Such lamps include a cathode electrode having a stem supported by a post. The cathode electrode is sealed inside the sealed ceramic body and the window.
The anode electrode is formed substantially of tungsten;
It has a tip portion arranged to face the cathode electrode. The tip is thermally coupled to a heat sink so that heat generated in the tip during operation can be dissipated.
The rounded head portion (round head portion) is formed on the tip of the anode electrode, and acts to equalize the thermal resistance to the heat sink from a plurality of points on the round head portion, It acts to stabilize the position of the arc between the cathode electrode and the anode electrode during operation. The anode electrode has a neck portion for preventing heating, and is disposed immediately below the round head portion. With this neck portion, the thermal resistance can be adjusted, and the operating temperature of the surface of the round head portion is maintained below the melting point of tungsten. Thus, the lamp current between the cathode and anode electrodes can be reduced to 14.1 amps or less without emitting substantial EMI over an operating time of at least 300 hours.

Although the present invention has been described in terms of the presently preferred embodiments, it will be understood that the above description of these embodiments is not limiting. From the above description, it is apparent that those skilled in the art can make various modifications and variations.
It is therefore intended that the claims be interpreted as including all such alterations and modifications as fall within the true scope and spirit of the invention.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an embodiment of a cylindrical high intensity short wavelength arc lamp according to the present invention, arranged so that light is emitted to the right side of the drawing.

FIG. 2 illustrates the benefits of forming a neck cut in the anode of a standard arc lamp.

FIG. 3 illustrates the advantages of cutting the neck and the rounding of the head at the anode of a standard arc lamp.

[Explanation of symbols]

 100 Lamp 102 Cathode 103 Stem 104 Suspension Support System 106 Anode 107 Neck 108 Body 114 Base 116 Internal Space 200 Anode 202 Neck 204 Head 204 206 Stem 208 Shoulder 210 Top 300 Anode 302 Neck 304 Head 306 Stem 308 Shoulder part 310 Tip part 312 Curved surface

Claims (7)

[Claims] 1. An improved arc lamp, comprising: a ceramic body; a tungsten anode supported by a base; and a cathode suspended by a support system and opposed to said anode. An interior space containing xenon gas, wherein the improvement is to transfer the tungsten anode between the anode tip region and the anode shoulder region in a smooth and rounded shape. An arc lamp characterized in that the arc lamp is provided with a curved surface that acts to stabilize an arc during operation. 2. An arc lamp according to claim 1, wherein the operation of the arc lamp is effected without electromagnetic interference over an operating life in which the threshold value of the lamp current is relatively constant. An arc lamp characterized by the following. 3. The arc lamp according to claim 1, wherein the tungsten anode is sufficient to prevent the melting and scattering of the tungsten by providing a wide passage for escaping the accumulated heat to the heat sink. An arc lamp having a sufficiently thick neck to operate said curved surface at a lower temperature. 4. The arc lamp of claim 1, wherein the tungsten anode is driven so as not to exceed a minimum electrode current value during operation so as to reduce radiation of electromagnetic interference. An arc lamp characterized in that: 5. A ceramic body, a tungsten anode supported by a base, a cathode suspended by a support system and opposed to said anode, and an interior space containing xenon gas. A method for controlling and limiting electromagnetic radiation from a xenon arc lamp, comprising: forming a neck portion in a main stem so as to inhibit heat dissipation; Raising the operating temperature of the tip region; and rounding the outer shape of the head tip region by rounding the tip and shoulder of the anode electrode in the head tip region. These steps result in the generation of electromagnetic radiation during operation at a particular electrode current value. Wherein the reducing. 6. The method according to claim 5, wherein the step of raising the operating temperature of the head tip region is performed so that the melting point of tungsten is not exceeded and the arc between the electrodes is made relatively stable. Carrying out at a sufficiently high temperature that it can be maintained. 7. A xenon arc lamp having an extended operating life and reduced radiation of electromagnetic interference, the xenon arc lamp having a stem supported by a support system and having a sealed body and window. A cathode electrode encapsulated therein; substantially formed of tungsten, having a tip opposed to the card electrode, and further capable of releasing heat generated within the tip during operation. An anode electrode thermally connected to a heat sink; and a rounded head portion formed on the tip of the anode electrode, wherein the rounded head portion is formed from a plurality of points on a surface of the rounded head portion. While acting to equalize the thermal resistance to the heat sink, the arc position between the card electrode and the anode electrode during operation is determined. It acts to Joka,
A rounded head portion; formed in the anode electrode and disposed directly below the rounded head; and adjusting the thermal resistance to raise the operating temperature of the surface of the rounded head to the melting point of tungsten. Maintaining a lamp current between the card electrode and the anode electrode for at least 300 hours of operating time to emit substantial electromagnetic interference. Characterized in that it can be reduced to 14.1 amps or less.