US3711700A - Disclosing light - Google Patents

Abstract

For dental, medical and other uses, with a disclosant phosphordye such as sodium fluorescein, a disclosing light emitting radiation substantially confined to the wavelength range between 380 and 505 nanometers (nm.) and free from infrared, yellow and ultraviolet. The light includes a source of light, which can be an incandescent lamp, a dichroic reflector behind it to reflect blue light forwardly and transmit the rest backwardly, a dichroic filter in front of the lamp to transmit blue light and reflect the infrared backwardly, and a viewing mirror for the parts irradiated, the mirror reflecting yellow light toward the observer and transmitting the other radiations. The ultraviolet, although it would excite the fluorescein, is filtered out because it would also make the natural teeth, and some kinds of artificial teeth, fluoresce and obscure the fluorescence of the fluorescein.

Description

United States Patent 91 Westlund, Jr. et a1.

[ 51 Jan. 16, 1973 1 DISCLOSING LIGHT [75] Inventors: Arnold E. Westlund, Jr., Manchester; Emery G. Audesse, Salem, both of Mass.

[73] Assignee: GTE Sylvania Incorporated [22] Filed: May 10, 1971 211 Appl. No 141,742

[52] US. Cl. ..240/4l.l5, 128/22, 128/23, 240/4659, 350/1, 350/311 [51] Int. Cl. ..A6lb 1/06 [58] Field of Search ....350/1, 311;240/41.15, 46.59; 128/22, 23

[56] References Cited UN lTED STATES PATENTS 2,798,943 7/1957 Prideaux ..350/l X 3,459,178 8/1969 Fleming ..l28/22 3,325,666 6/1967 Bird et a1. ..35()/l UX 3,255,342 6/1966 Seitz et al. ..240/4l.l5 X

OTHER PUBLICATIONS Schroeder et al., A Commercial Cold Reflector, Jour. of the SMPTE, Vol. 69, No. 5, May 1960, pps. 351-354.

Primary ExaminerDavid Schonberg Assistant ExaminerToby H. Kusmer Attorney-Norman J. OMalley, Laurence Burns and Joseph C. Ryan [57] ABSTRACT For dental, medical and other uses, with a disclosant phosphor-dye such as sodium fluorescein, a disclosing light emitting radiation substantially confined to the wavelength range between 380 and 505 nanometers (nm.) and free from infrared, yellow and ultraviolet. The light includes a source of light, which can be an incandescent lamp, a dichroic reflector behind it to reflect blue light forwardly and transmit the rest backwardly, a dichroic filter in front of the lamp to transmit blue light and reflect the radiated, the mirror reflecting yellow light toward the observer and transmitting the other radiations The ultraviolet, although it would excite the fluorescein, is

filtered out because it would also make the natural teeth, and some kinds of artificial teeth, fluorescc and obscure the fluorescence of the fluorescein.

1 Claim, 4 Drawing Figures 0R mew/41. 5

infrared, backwardly, and a viewing n i ror for the parts ir- PATENTEDJAH 16 I975 RELATIVE ENERGY SHEET 1 or 2 FIG.I

400 500 600 700 800 EMITTED LIGHT WAVELENGTH IN NANOMETERS MW m,

ATTORNEY PATENTEBJAMSIHH 3.711.700

sum 2 or 2 EMERY G.AUDESSE ARNOLD E. WESTLUND JR.

INVENTORS BYWMI ATTORNEY DISCLOSING ueur This invention relates to electric lighting devices, and 5 particularly to devices for dental and medical purposes, such as viewing a persons teeth for plaque, tartar (technically called calculus) and the like, and for examining the skin and eyes. Such devices are often called disclosing lights.

2. BriefSummary of Prior Art Devices for this purpose have previously used ultraviolet light from incandescent lamps with Wratten type filters or blacklight lamps. The former were inefflcient and yielded very little light on the person, and'the latter were cumbersome and presented a possible radiant energy hazard, because of the increased ultraviolet light.

In using the device, the teeth or other portions of the body to be observed were first treated with a 20 fluorescent material, a small drop generally being sufficient for use on teeth, and the resultant fluorescence observed.

It has been suggested to use on the teeth or other parts to be observed a phosphor-dye excitable to fluorescence by visible light, with a filter to absorb the visible light on both sides of the absorption curve, although the excitation curve, which is the important. one, was not mentioned.

BRIEF DESCRIPTION OF THE INVENTION We have discovered that the use of ultraviolet in a disclosing lamp was ineffective with a phosphor-dye such as fluorescein, because the teeth themselves 35 fluoresce white and this is not in much contrast to the yellow fluorescence of the sodium fluorescein. We have further discovered that in cutting off part of the excitation and absorption bands by keeping the exciting radiation above 380 nm. (nanometers), that, is above the ultraviolet, and keeping the exciting radiation largely below 525 nm., which means substantially confining it to the violet and blue, with its peak in the latter, we can obtain very good yellow fluorescence from the fluorescein in contrast to the nearly dark background provided by the teeth themselves.

This was unexpected, because the wavelengths exciting sodium fluorescein were left in some doubt by the prior art, and The Merck Index-an Encyclopedia of Chemicals and Drugs (8th Ed. 1968; Merk & Co., Rahway, N. 1.), states that sodium fluorescein responds best to radiation of 3600 Angstrom Units (360 nm.), which is in the ultraviolet region. The Pharmacological Basis of Therapeutics" (4th Ed.) by Goodman and Gilman, says that the absorption maximum in water is 4935 Angstrom Units (493.5 nm.), but this only adds to the confusion, and in any event the absorption maximum is not necessarily the excitation maximum. Even a non-fluorescent material has an absorption maximum, although it doesn't have an excitation maximum, nor any excitation at all.

We have discovered that in order to get the maximum excitation and the maximum effect from the yellow fluorescence, the cutoff of the light output from the disclosing lamp must have a very sharp cutoff at about 525 nm. to emit as much as possible of the exciting visible light without emitting any appreciable light of the color of the fluorescein fluorescence. This can be achieved with ,a dichroic or interference filter infront of an electric lamp such as an incandescent lamp. The filter will transmit between 380 nm. and 525 nm., and cut offelswhere.

To emphasize the desired spectral pattern further, a dichroic reflector can be used behind the lamp, to reflect forwardly light of380 525 nm. and transmit the infrared b ackwardly and out of the beam. The reflector 0 can reflect all of the visible light if desired, and the burden of cutting out the undesired wavelengths be put on the filter.

When using the device, stray ambient light can obscure the fluorescence by illuminating the teeth directly, but we have found that the use of a dichroic mirror for viewing the irradiated teeth is very effective, if it is designed to reflect light in the yellow, or emitting, range, but transmit blue light and infrared, which will therefore not affect the observer. To prevent the ambient light from passing through the mirror toward the observer, a shield is preferably provided in back of the mirror and spaced therefrom. The spacing gives a region in which the radiations transmitted from the front of the mirror are trapped. The shield and any walls which define the space around the mirror should have low reflectivity. The yellow light to be reflected would be between about 560 and 590 nm. A person can then shine the light on his teeth and observe the results in the mirror.

Because of the nature of dichroics, the filter in front of the lamp will also transmit some of the very far red between 700 to 800 nanometers, but this will not affect the operation of the device, because of the extremely low sensitivity of the eye to such far red light.

Mimr tllefilt qyill n ottgansmit infrared adiation,

but will reflect it 95, which Fre'VfifiifiTheatin the portion of tlie body on which the radiation falls. This heating effect of the infrared could otherwise be quite serious.

The result can be a very compact disclosing lamp for medical and dental purposes, although if desired, the filter and a suitable lamp or lamps can be used in a large, overhead fixture, or in other ways.

The device is, however, especially useful in the form of a lighting unit for observing a small area.

The lamp, filter and reflector can be held in position in a plastic housing, and in a portable unit the reflector could preferably, for most purposes, bring the light to a focus about 2 to 4 inches in front of the filter.

The dichroic coatings can be made in the usual manner for such coatings, that is, they can be built up on a backing plate of glass, for example with a series of alternate layers ofmagncsium fluoride and zinc sulfide, each layer being about a quarter wavelength thick.

The spectral transmittance characteristics of this coating for normal incident light should be as follows for greatest effectiveness: p

l. The average transmittance should be greater than 80 percent between 380 and 490 nm.,as measured in 10 nm. increments, and no individual valley should be less than 70 percent 2. The 50 percent transmittance point in the bluegreen wavelengths should lie between 495 and 505 nm.

3. The 10 percent transmittance point in the bluegreen wavelengths should lie between 510 and 525 nm.

Transmittance between 550 and 660 nm should be less than 2 percent.

Some deviation from these requirements is permissible, but the greater the deviation the less will be the effectiveness.

A switch for turning the lamp off and on can be incorporated in the device, so that the user will have everything under his immediate control.

BRIEF DESCRIPTION OF DRAWINGS Other objects, features and advantages of the invention will be apparent from the following specification taken in connection with the accompanying drawings, in which:

FIG. 1 is a longitudinal cross section of a device according to the invention;

FIG. 2 is a spectral energy distribution curve of the light output of the device;

FIG. 3 is a plan view of the device; and

FIG. 4 is a front elevation of the device.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, the tubular incandescent lamp 1 is shown held by its base 2 in the usual contact receptacle 3, into which the usual threaded portion 4 of the base fits, and which is attached to the housing 5. In the customary manner, the receptacle 3 makes electrical contact with the outer metal shell 6 of the base, and with the eyelet contact 8 of the base 2, said eyelet contact being attached to the outer metal shell through the insulating glass plug 9 in the manner customary in the art.

The lead-in wires 10,11 extend out of the housing through a bushing 12, held in the usual manner by a nut 13 on a threaded portion 14 of said bushing 12. Wire is electrically connected to the helical coil 3 and wire 11 extends through on-off switch 15 and wire 16 to the socket. The wires are covered with insulation.

The push button 17 actuates the switch 15 in the usual manner, being set into the housing 5.

The filament in lamp 1 is at or near the focus of the reflector 18, which in the embodiment shown is an ellipsoid having one focus substantially at the lamp filament and the other focus a few inches, say from 2 to 4 inches, in front of the device. The reflector 18, which can be a surface of revolution, is of glass having a dichroic coating on its reflecting surface. The dichroic coating is designed to reflect visible light and transmit infrared.

In front of the reflector is the dichroic filter 20, which is flat, this reflects yellow and infrared back into the housing, and transmits blue, which is roughly the opposite of what the reflector 18 does. The edge 21 of the reflector 18 is spaced from the filter 20 by a coiled spring 21 which bears against the edge frame 22 of filter 20, reflector 18 being pushed back by the spring 21 to seat against the stop 22 in housing 5.

The dichroic mirror 23 is set on a projecting enclosing bracket 24 at the top front of the casing 5. The mirror is dichroic, reflecting yellow and transmitting blue and infrared, and is set at an angle to a plane transverse to thelongitudinal axis of the optical system, which comprises reflector l8, lamp 1 and filter 20, and is in position to reflect rays from the teeth or the like to the eye of the viewer. An angle of approximately 10 has been found very effective for the embodiment described, although the angle can be varied between 5 and 16 with good results.

The outer details of the housing are shown in FIGS. 3 and 4. When the words top," front" and the like are used herein, they refer to the corresponding portions of the device when in the position shown in FIG. I, that with the mirror 23 at the top, and with the end of the housing at filter 20 being considered the front, since it is the place where light emerges from the device.

In FIG. 2, the spectral energy distribution of the device is shown. The light output is seen to peak in the blue at about 490 nanometers and to extend from about 380 nanometers to about 525 nanometers, that is, from the violet to the green. There is no appreciable light in the yellow and orange but there is a narrow peak in the far red, which is unimportant because the sensitivity of the eye is very low in that region. FIG. 2 shows the energy distribution of the radiation from the device, and not the effect on the eye.

The front view of FIG. 3 shows the viewing mirror 23 the bracket 24 holding it, the face plate 25, the front of housing 5 and button 17. The profile in FIG. 4 shows the housing 5, the bushing 12 and the push button 17. Other styling than that shown can be used.

The dichroic coatings used in the embodiment described were deposited on glass plates which had a thickness between 0.047 to 0.062 inch. The lamp 1 was an l8-watt appliance lamp in a T7 bulb, that is in a bulb tubular in shape and seven-eighths inch in diameter.

This is a vacuum lamp in which the tungsten filament operates at a comparatively low temperature, less than in the usual gas filled bulb, so the ultraviolet emitted from the filament is small, and the glass of the bulb cuts it down somewhat more. The filter 20 has a fairly sharp cutoff between 350 and 380 nm. so that it also cuts out some of the residual ultraviolet, but this ultraviolet cut off from the filter is less necessary than it would be with a higher ultraviolet-content source.

The filter 20 used in the specific embodiment described had about percent transmittance at 380 nm., about 50 percent at 370 nm. and 8 percent at 350 nm. On the other end of the transmitted region, the transmission was slightly above 80 percent at 490 nm., about 60 percent at 500 nm 40 percent at 505 nm. and 6 percent at 525 nm.

The filter 20 used was a dichroic, or interference filter, with alternate quarter-wavelength thick layers of magnesium fluoride and zinc sulfide. The layers were deposited on light-transmissive glass backing plate, the layer on the glass being the fluoride, for good adherence, and the top, or thirteenth layer being of the fluoride, which gives a harder surface than the sulfide. The mirror 23 in which the teeth were viewed was the same.

The reflector 18 has 20 layers, each about onequarter wavelength thick, the one on the glass being magnesium fluoride. The layers then alternate ending in a zinc sulfide layer on the outer surface.

The coatings can be applied in the usual manner for dichroics.

Although a specific embodiment has been described above, various modifications and alterations will be apparent to a worker skilled in the art after reading the above specification, without departing from the spirit and scope of the invention, which is limited only by the claims.

What we claim is:

l. A disclosing light for self-examination of teeth treated with a phosphor dye excitable to fluorescence by visible light comprising: a housing containing an incandescent lamp; a dichroic reflector within said housing behind said lamp in position to reflect blue light and transmit infrared radiation; a filter within said housing in front of said lamp for transmitting blue light and reflecting back yellow light and infrared radiation, said filter having an average transmittance greater than 80 percent between 380 and 490 nm., as measured in nm. increments, and is not less than percent for any wavelength in that range, and in which the 50 percent transmittance point is between 490 and 505 nm., with the 10 percent transmittance point in the blue-green wavelengths between 510 and 525, with the transmittance between 550 and 660 nm. less than 2 percent; a dichroic viewing mirror attached to said housing and outside it in position such that a viewer using the light on his teeth can see the result in said mirror, the transmittance and reflectance characteristics of said mirror being about the same as of said filter; and a shield disposed behind said mirror to prevent ambient light from passing through said mirror toward said viewer.

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