AU2001249162A1 - Combination uv inspection light and flashlight - Google Patents

Description

COMBINATION UV INSPECTION LIGHT AND FLASHLIGHT

Cross Reference to Related Applications

This patent application claims benefit of U.S. provisional Serial No.

60/188,958, filed March 13, 2000.

Background of the Invention

This invention concerns ultraviolet (UN or black) lights of a type used by

technicians in carrying out leak detection inspections by illuminating potential leak sites to

detect the presence fluorescent tracer dyes. This is commonly done in servicing air

conditioning refrigeration systems, automobile air conditioning systems components,

hydraulic machinery, etc.

The dyes are typically mixed with a compatible oil and injected into the

system. If leaks are present, a trace of the dye and oil mixture flow onto external surfaces.

This leakage fluoresces when illuminated with UN and sometimes blue light, emitting visible

light which can be seen by the technician.

Such UN lights particularly adapted for leak detection service applications

have been developed in recent years, utilizing selective reflection filters, sometimes referred

to as "dichroic" filters which transmit ultraviolet wavelengths and reflect back visible light to

maximize the user's ability to see any fluorescence that occurs. Such lights require high

wattage lamps as a UN source as compared with most other application of UN lights, which

therefore emit considerable heat energy. The use of reflecting or "dichroic" filters is a

significant improvement over absorbent filters used in the past selectively which absorbed

visible light from the high intensity light emitted by the lamps, since the filters themselves overheated if the light was used for long periods and sometimes cracked during such use.

For this reason, the dichroic filters have been designed to transmit infrared

radiation as well as UN to prevent overheating of the dichroic filter and other components.

This is described in copending U.S. application 08/964,839, filed on November 5, 1997 and

U.S. patent 5,905,268. In those lights, visible light is reflected back into the housing such

that some heating of the interior of the light occurs.

In another types of testing, dyed smoke is used to initially locate leak,

requiring a flashlight to detect the smoke. Also, it is often useful to have a flashlight

available in darkened locations in buildings where equipment is being serviced. The

previously UN lights have not been able to be used as an ordinary flashlight.

Accordingly, it is the object of the present invention to provide a UN light

which while utilizing a high intensity lamp as a powerful source of UN light does not result

in overheating of the light nor specifically the optical components eliminating visible light,

and which emits a very high proportion of the UN light generated by the lamp.

It is another object to provide such a UN light which is also conveniently

useable as a flashlight.

Summary of the Invention

The above objects as well as others which will become apparent upon a

reading of the following specification and claims are achieved by using a reflector rather than

a dichroic filter to selectively act to produce a beam of UN light while also directing the

visible and IR radiation out from the light.

The reflector selectively reflects only emitted UN light by the lamp, while transmitting visible and IR radiation. Such dichroic reflector is commonly known in the art

as a "cold mirror". The cold mirror reflector is angled with respect to the high wattage lamp

so that the UN light beam is directed out of a light housing through a first window formed on

one side of the light.

On the other hand, visible and infrared light is transmitted through the cold

mirror reflector and out from a second window in the front end of the light housing.

A detachable cap may be secured over the second housing wind to optionally

block the visible-infrared light beam from exiting the light housing.

Heating of the cold mirror reflector is minimized as none of the wavelengths

are absorbed by that optical element, nor is retained elsewhere within the light housing when

the cap is removed.

At the same time, the light is capable of a dual use, i.e., as a pure UN light

source and also as a flashlight increasing its utility to the user, particularly where tracer

smoke testing is to be practiced.

The light according to the invention is also compact and may be manufactured

at low cost.

Description of the Drawings

Figure 1 is a perspective exterior view of an embodiment of a light according

to the invention.

Figure 2 is a partially sectional view taken through the light shown in Figure

1.

Figure 3 is a top view of the partial section of Figure 2. Figure 4 is a partially sectional view taken through the center of the light

showing the reflector mounting.

Figure 5 is an enlarged partially sectional view of the head portion of an alternate embodiment of the invention.

Detailed Description

In the following detailed description, certain specific terminology will be

employed for the sake of clarity and a particular embodiment described in accordance with

the requirements of 35 USC 112, but it is to be understood that the same is not intended to be

limiting and should not be so construed inasmuch as the invention is capable of taking many

forms and variations within the scope of the appended claims.

Referring to the drawings, and in particular Figure 1, the UN light 10

according to the present invention includes a housing 11 comprised of an elongated handle 12

and head portion 14 both made of a suitable molded plastic.

A UN light beam window 16 faces to one side of the light 10, while a visible-

infrared window facing the end of light 10 is shown covered with a plastic cap 18.

Figure 2 shows the inner details of the UN light 10. A 12 volt 100 watt lamp

20 which is a powerful source of UN and visible radiation of a much greater power than the

type used with a standard flashlight. The lamp 20 may be of the Xenon type of high color

temperature (3500K) which produces substantial long wave ultraviolet emissions. The

envelop is made of quartz which is itself highly transmittive to long wavelength ultraviolet,

i.e., 340-380 nm. Such a lamp is available from Osram Sylvania under part number FCR

64625 HLX. The lamp 20 is located at the approximate focal point of a parabolic reflector

22, electro formed of nickel on an accurately shaped stainless steel mandrel. A focal length of

0.187 inches allows the lamp 20 to be approximately located at the focal point to maximize

beam concentration.

As described in copending U.S. application 09/491,413, filed on January 26,

2000 and U.S. application 08/964,839, filed on November 5, 1997, the parabolic reflector 22

is preferably coated to eliminate destructive interference which would reduce the intensity of

the reflected UN light

The surface of the parabolic reflector 22 has a plurality of coatings applied

thereto, one of aluminum and one of silicon dioxide. The interface of silicon dioxide and air,

and silicon dioxide and aluminum produces a double refraction in an opposite sense, which

offset each other to eliminate the potential destructive interference which otherwise could

occur.

The first coating is of aluminum, while the second coating is of silicon

dioxide. The thickness of the silicon dioxide should be uniform and accurately held to

achieve this effect, the thicknesses determined by the "quarter wave stack" principle.

The refractive index of each interface, i.e., the silicon dioxide and air, silicon

dioxide and aluminum determines the effective phase shift of the reflected light. A thickness

of aluminum of .057 microns and of silicon dioxide of .066 microns has been successfully

used for this purpose. The silicon dioxide-air interface causes an approximate 13 degree

forward phase shift, the silicon dioxide-aluminum interface a 13 degree lagging phase shift,

thereby offsetting each other.

Silicon dioxide coatings have heretofore been employed simply to protect the substrate from scratches and oxidation but have not been sufficiently uniform nor of the

proper thickness to achieve enhanced reflection of ultraviolet wavelengths.

A coated parabolic reflector suitable for this use is available from American

Galvano, 312 N. Cota St., Unit I, Corona, California 91720.

The lamp 20 can be powered from a 12 volt power source such as a vehicle

cigarette lighter socket by use of a plug connector 24 connected by cables 26, a strain fitting

28 at the entrance to the handle 12. An on-off switch 30 connects one lead to the lamp 20, a

connector 32 connecting the other lead. Batteries or an AC power source can also be used.

A lamp base 34 is provided with electrical terminals in conventional fashion.

A selective dichroic reflector 36 is mounted within the head portion 14

opposite the reflector 30 and lamp 20, inclined at 45° such as to redirect UN light emitted

from the lamp 20 and parabolic reflector 22 out through the window 16 in one side of the

housing 11. The selective reflector 36 acts as a beam splitter, transmitting visible and

infrared light while reflecting UN light such as to direct a pure UN beam out through the lens

window 16. The window 16 may be covered with a window lens constructed of borosilicate

glass which is believed to block shorter wavelengths of UN. light which might be hazardous

to the eyes, i.e., around 320 nm and lower.

The cold mirror reflector 36 preferably is of dichroic design utilizing a series

of coatings of a predetermined thickness to create selective reflection. This invention

contemplates a design of such coatings to produce selective reflection of UN light rather than

transmission of UN light as described in U.S. patent 5,905,268, so that a UN light beam is

directed out through the side facing window 16.

At the same time, the coatings are designed so that visible light is transmitted through the reflector 36 rather than reflected, so that a beam of visible light is directed out

through the window 38 covered by cap 18. Window 38 is also preferably covered with a

clear lens covering constructed of borosilicate glass to block any deep UN light.

As disclosed in U.S. Serial No. 09/491,413, filed on January 26, 2000,

dichroic optical elements from ZC & R Coatings for Optics, Inc. of Torrance, California are

preferred as having coatings of tantalum pentoxide which do not absorb UN.

A suitable cold mirror having a part number CM-UN-350 is commercially

available from ZC & R.

That particular cold mirror has a high percentage of reflectance and low

percentage of transmittance of wavelength in the range of 350 nm to 450 and a high

percentage of transmittance of wavelength from 600 nm to 1200 nm and higher. Deep UN,

i.e., below 340 nm is largely transmitted.

Thus, both visible and infrared are caused to be transmitted out of the light 10

to minimize heating and to create a visible beam for use in other tests and as a flashlight.

The coatings of the cold mirror reflector 36 can also be applied by ZC & R to

minimize blue visible light at wavelengths over 400 nm where the tracer dyes do not

fluorescence in response to such blue light in order to eliminate the need for "blue blocker"

eyeglasses which are necessary when the UV light beam also contains blue light.

Elimination of blue light in the UN beam is advantageous for some leak

testing applications as described in the above referenced copending application.

The cold mirror reflector 36 can comprise a rectangular piece of coated

borosilicate glass as seen in Figures 3 and 4. A molded-in groove 40 holds the reflector 36 in

position in the head 14 at a 45° angle. The cap 18 also of a molded plastic such as silicone can be opaque to block

the visible light, or the cap 18 can be removed to use the light 10 as a flashlight. If the visible

light does not interfere with observation of the fluorescence, since being directed at 90° to the

UN beam, the cap can be removed, tab 42 assisting in its removal, to maximize cooling of the

housing interior.

Alternatively, forward facing louvers 44 can shield vent openings 46 to

improve cooling with the cap 18 in place.

Claims (8)

Claims

1. A combination flashlight and light for use in inspection of leak sites and the like, comprising:

a housing;

a lamp mounted in said housing emitting intense UN, visible and infrared

radiation when said lamp is energized;

a power source for energizing said lamp;

a switch controlling connection of said power source to said lamp to control

energization of said lamp;

a dichroic cold mirror reflector mounted to said housing facing said lamp but

inclined thereto, said dichroic cold mirror reflector coated so as to reflect UN light from said

lamp laterally while transmitting visible and infrared light;

said housing having a first window located to receive said UN beam reflected

laterally from said dichroic cold mirror reflector to be allowed to exit out of said housing, and

a second window located aligned with said lamp and dichroic reflector to allow said visible

and infrared light to exit therethrough and out of said housing.

2. The UN light according to claim 1 further including a detachable cap

on said second window.

3. The UN light according to claim 2 further including vent holes in said

housing behind said dichroic cold mirror reflector.

4. The UN light according to claim 3 further including louvers facing said

second window.

5. The UN light according to claim 1 further including a parabolic

reflector having said lamp approximately located at the focal point thereof and concentrating

light emitted from said lamp and directing the same at said dichroic cold mirror reflector.

6. The UV light according to claim 1 wherein said first and second

windows have a window lens mounted therein constructed of borosilicate glass to block UV

below about 320 nm.

7. The UV light according to claim 1 wherein said dichroic cold mirror

reflector reflects a high percentage of light in the range of 350 to 450 nm and transmits light

in a range longer than 450 nm.

8. The UV light according to claim 1 wherein said dichroic cold mirror

reflector reflects a high percentage of in the range of 320 to 380 nm and transmits high

percentage of light in a range over 400 nm.