DISPOSITIF STIMULATEUR DE PHOTOLUMINESCENCE, PERMETTANT L'OBSERVATION ET L'ANALYSE DU PROCESSUS

DEVICE FOR STIMULATION OF PHOTOLUMINESCENCE AND THE OBSERVATION AND ANALYSIS OF THE SAME

Abrégé anglais

- Abstract -
A device for stimulation of photoluminescence and the observation
and analysis of the same, which has a laser for the irradiation of a surface to
be investigated, and an optical reception system, the optical axis of which runsin the emitted laser beam, and which casts the light of the stimulated fluores-
cence on a light analyzer. As specified by the invention, the laser is positi-
oned on the side of the optical reception system oriented towards the light ana-lyzer. The laser beam enters the optical exit axis of the optical reception sys-
tem, and passes through it in a direction reverse from the light received from
the fluorescing surface. The same ray path is used for the irradiation and reflect-
ion of the fluorescing surface, so that the irradiated surface and the reflect-
ed surface are always equally large.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a device for prospecting the ground remotely for
mineral deposits by means of
a laser which emits a beam and irradiates an area of
ground surface to stimulate the area of ground surface to
fluoresce light; the improvement comprising
an optical transmitter and receiver system
facilitating the irradiation and observation of a substantially
identical area of ground surface, said system defining a common
central optical path wherein the beam of such laser enters said
system and passes through said system along said optical path
and thereafter irradiates the area of ground surface, and
wherein said system receives fluoresce light from the
stimulated area of ground surface and passes the fluoresce
light in a direction reverse to the direction of the beam
through said system whereby the fluoresce light received from
the surface and passed through said system corresponds with the
irradiated surface.

2. In a device as claimed in Claim 1, wherein said laser
is positioned laterally from said optical path of said
transmitter and receiver system and said beam of said laser is
directed into said transmitter and receiver system by means of







an inclined dichroic reflector positioned in said optical path
between a light detector and said transmitter and receiver
system, said light detector converting said light fluoresced by
said area of ground into an electric signal.

3. In a device as claimed in Claim 1, wherein said
optical transmitter and receiver system comprises a reflecting
telescope.

4. In a device as claimed in Claim 3, wherein said
reflecting telescope is a Cassegrain telescope.

5. In a device as claimed in Claim 3, in which said
reflecting telescope compensates for inherent divergence of
said laser beam, expanding and collimating said laser beam
simultaneously and wherein said reflecting telescope condenses
said received light from said area of ground surface.

6. In a device as claimed in Claim 5, wherein said
reflecting telescope includes a large and small mirror and
wherein said small mirror is adjustable along said optical path
for modification of said irradiated and observed area of said
ground surface.







7. In a device as claimed in Claim 2, wherein said laser
beam defines a cross-sectional dimension and wherein said
device further includes a screen having an aperture positioned
between said dichroic reflector and said light detector, said
aperture corresponding in size to said cross sectional
dimension of said laser beam at said dichroic reflector.

8. A device for stimulating and sensing photoluminescence
in order to prospect the ground remotely for mineral desposits
comprising, in combination:
an excimer laser for emitting a beam, irradiating an
area of ground surface, and stimulating said area of ground
surface to fluoresce light;
a light detector for converting said light fluoresced
by said area of ground surface into an electric signal; and
an optical transmitter and receiver system disposed
between said light detector and said ground surface, said
system facilitating the irradiation and observation of a
substantially identical area of ground surface, said system
defining a central optical path and characterized in that
said excimer laser beam enters said optical path of
said transmitter and receiver system between the said light







detector and said transmitter and receiver system and
transverses through said system in reverse direction from said
light received by said system from said area of ground surface.

9. The device of Claim 8, wherein said laser is
positioned laterally from said optical path of said transmitter
and receiver system, and said beam of said laser is directed
into said transmitter and receiver system by means of an
inclined dichroic reflector positioned in said optical path
between said light detector and said transmitter and receiver
system.

10. The device of Claim 8, wherein said optical
transmitter and receiver system comprises a reflecting
telescope.

11. The device of Claim 10, wherein said reflecting
telescope is a Cassegrain telescope.

12. The device of Claim 10, in which said reflecting
telescope compensates for inherent divergence of said excimer
laser beam, expanding and collimating said excimer laser beam






simultaneously, and wherein said reflecting telescope condenses
said received light from said area of ground surface.

13. The device of Claim 12, wherein said reflecting
telescope includes a large and small mirror, and wherein said
small mirror is adjustable along said optical path for
modification of said irradiated and observed area of said
ground surface.


14. The device of Claim 9, wherein said laser beam defines
a cross-sectional dimension and wherein said device further
includes a screen having an aperture positioned between said
dichroic reflector and said light detector, said aperture
corresponding in size to said cross-sectional dimension of said
laser beam at said dichroic reflector.

11

Description

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The invention concerns a device of the type designated within the
higher concept of claim 1, for the stimulation of photoluminescence and the ob-
servation of the same. An analysis of the results of observations can occur in
various ways, and allows conclusions about the type of the luminescing substance,
such as ore, for example. This is widely known, and is described, for example,
in the book "Spectroscopy, Luminescence and Radiation Centers in Minerals", by
A.S. Marfunin, Springer Verlag, Berlin-Heidelberg-New York, 1979.

: A device of the type under discussion is known from the firm
Scintrex, 222 Snidercroft Road, Concord, Ontario, Canada, in which the stimulat-ion of the fluorescence occurs through an Excimer laser operating in the ultra-


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violet range, of which a specific divergence oF rays is characteristic, on thebasis of which an enlargement of the cross-section of the beam occurs at increas-
ing distance. This has a consequence that the size of the surface stimulated toluminescence is dependent on the distance of observation.

A telescope is used for observing the surface stimulated to
luminescence. In order to attain coaxiality of the telescope with the emltted
laser beam, a deflection mirror is provided on the beam entrance side, thus on
the side of the telescope oriented to the irradiated surface, in the area of theoptical entrance axis, through which the beam of the laser is deflected from thelaterally positioned laser into the optical axis and directed ontQ the surface
to be stimulated.

This known arrangement has the disadvantage that only at a com-
pletely specific distance can it be attained, that the surFace irradiated and
that observed by the optical reception system is equal. Because of the size of
the cross-section of the laser beam, dependent on distance, the irradiated and
the observed surface do not coincide at all distances.

Through DE 05 32 14 0~9, a spectral fluorometer of the type con-
cerned is known, in which the light of the stimulated fluorescence fails on a
concave grid of an optical reception system, from which the radiation is, in a
specific manner, laterally reflected, and arrives in the laterally positioned
parts of the reception optics. The concave grid has an aperture in its center,
through which the beam of a laser, positioned behind the concave grid and provided
with its own optics, strikes the surface to be investigated. This known spectral

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fluorometer is thus constructed essentially similar to the known device previ-
ously described, and thus has the same disadvantages.

Accordingly3 the task of the invention lies in creating a device
of the type under discussion for st;mulating photoluminescence and for observ-
ing the same, which makes possible an agreement between the surface irradiated
and stimulated to luminescence, and of the surface observed.

This task, which serves as the basis of the invention, is solved
through the patterns cited in the characteristics of patent claim 1. The basis
of this pattern is the concept of providing optics for the emitted laser beam
and for the received light, providing the same path of rays~ only in opposite
directions, so that, on the light detector, independently of the distance of theluminescence surface, this surface is always directly reflected, and never more
and never less. This even applies if the reception optics are adjusted, in order
to more or less enlarge the laser beam, and to enlarge the irradiated surface,
in order, for example, to thereby alter the energy density on the irradiated sur-
face or even to simpl~ alter the size of this surface.

The laser can be positioned laterally from the optical exit axis
of the reception optics, so that its beam is directed into the optical receptionsystem by means of an inclined dicroitic mirror positioned in the optical exit
axis. This mirror thus reflects the light of the laser, and, on the other hand,lets through the light of the fluorescing surface, the wave lengths of which can,
for example9 lie in the range of between 380 nm and 700 nm.

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The reception optics system is a reflecting telescope, prefer-
ably a Cassegrain telescope, in which the large concave mirror exhibits an aper-ture lying in the optical exit axis through which the light concentrated by a
small concave mirror positioned opposite the large concave mirror exits.

Between the dicroitic mirror and the light detector, there is
positioned an aperture~ the opening of which corresponds to the dimensions of
the beam of the laser.

The invention should be explained in greater detail through an
example of execution as depicted in the diagram.

Figure l shows an example of the device as specified by the in-
vention with a f;rst adjustment of the reception optics;
and:

Figure 2 shows an example of execution with a second adjustment
of the reception optics.

The device shown essentially schematically in figures l and 2
èxhibits ~ laser (l), the beam of which (2) is directed, by means of an inclin-
ed dicroitic mirror (3) and by means of an opening aperture (4) in a large con-
cave mirror (5), onto a small concave mirror (6) of a Cassegrain telescope (7).
The small concave mirror spreads the beam of the laser, and casts its light on
the 1arge concave mirror (S), which reflects the light of the laser, projecting
it onto a surface (8) indicated by the cross-hatching, which is thus stimulated
to fluorescence. The outer limit of the light of the laser, after reflection

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by the small concave mirror (6), is depicted by thick lines (9, 10), as well
as (11, 12), whereby the direction of the light is indicated by the arrows
(13, 14).

The light of the surface (8) stimulated to fluorescence arrives
at the large concave mirror (5), from which it is directed to the small concave
mirror (6), which produces a concentration of rays (15) indicated by the dotted
line, which9 through the opening aperture (4), enters the dicroitic mirror (3)
and a slit (16), into the light detector (17). The external rays of the light
coming from the surface (8) are indicated by the dotted lines (18 to 21), where-by the direction is symbolized by arrows (22 to 24).

Figures 1 and 2 differ through this: in figure 1, the small con-
cave mirror (6) is shifted in the direction of the arrow (25), so that the beam
of the laser leaving the optic system is indicated; this is clear through the
divergence of the lines (11, 12) to the surface (8).

In the case of figure 2, the small concave mirror (6) is displaced
in the direction of the arrow (26), so that the emerging beam of the laser is
concentrated, which is clear through the parallelity of the lines (11, 12) in
figure 2. It is to be seen that the lines (18, 19), at each position of the
small concave mirror (6), have the same course as the lines (Il, 12), so that
the surface (8) stimulated to fluorescence has the same range as the surface
viewed by the telescope (7).