OPTICAL DEVICE

Abstract

An optical device includes an emitting apparatus and an optical guide. The emitting apparatus includes a first aperture for emitting an excitation radiation therethrough, the excitation radiation includes at least one light radiation having a wavelength included in a predefined spectral range. The optical guide extends longitudinally between first and second ends thereof and is internally provided with a core which is suitable for propagating radiation with a wavelength included in the predefined spectral range and defining an inlet aperture at the first end and an outlet aperture at the second end, the inlet aperture facing the first aperture so as to be passed through by at least a portion of the excitation radiation when it is emitted by the emitting apparatus and the outlet aperture is directed towards an unknown sample when the optical device is in a first operating condition.

Claims

1. An optical device (100) comprising: an emitting apparatus (1) comprising a first aperture (2) and which is configured to emit an excitation radiation (3) through said first aperture (2), said excitation radiation (3) comprising at least one light radiation having a wavelength included in a predefined spectral range, an optical guide (9) which extends longitudinally between a first end (10) thereof and a second end (11) thereof and which is internally provided with a core (13) which is configured to propagate radiation at a wavelength included in said predefined spectral range and defining an inlet aperture (14) at said first end (10) and an outlet aperture (15) at said second end (11), said inlet aperture (14) facing said first aperture (2) so as to be passed through by at least a portion of said excitation radiation (3) when said excitation radiation is emitted by said emitting apparatus (1), and said outlet aperture (15) being configured to be directed towards an unknown sample (16) when said optical device (100) is in a first operating condition, wherein said optical guide (9) comprises a reflective surface (18) which at least partially delimits said core (13), said reflective surface (18) being a regular optical surface with respect to radiation with a wavelength included in said predefined spectral range and being suitable for reflecting the portion of the excitation radiation (3) which is projected into said core (13) through the inlet aperture (14) so as to propagate said excitation radiation (3) out of said optical guide (9) through said outlet aperture (15) in order to illuminate the unknown sample (16), wherein said optical device (100) comprises a gap (20) which is arranged between said first aperture (2) and said inlet aperture (14), said gap (20) being configured to receive a reference sample (21) so that the excitation radiation (3) emitted by said emitting apparatus (1) through said first aperture (2) illuminates the reference sample (21) when said optical device (100) is in a second operating condition, in which said reference sample (21) is received in said gap (20).

2. The optical device according to claim 1, wherein said core (13) is configured to propagate a first light signal (19) which is introduced into said core (13) through said outlet aperture (15) so as to transmit said first light signal (19) towards said first aperture (2) through said inlet aperture (14), said first light signal (19) corresponding to at least a portion of the excitation radiation (3) which is emitted by said outlet aperture (15) and which is reflected by said unknown sample (16) when said optical device (100) is in said first operating condition.

3. The optical device according to claim 1, wherein said predefined spectral range is defined between 200 nm and 2500 nm.

4. The optical device according to claim 1, wherein said emitting apparatus (1) is a diffuse light source.

5. The optical device according to claim 1, wherein said emitting apparatus (1) comprises: a cavity (27) which is delimited by an internal surface (8), at least one light source (6) which is configured to project a first light radiation (7) on said internal surface (8), wherein said internal surface (8) is suitable for reflecting the first light radiation (7), thereby giving rise to said excitation radiation (3).

6. The optical device according to claim 5, wherein said internal surface (8) is at least partially spherical in such a manner that said excitation radiation (3) is of the type substantially diffused at said first aperture (2).

7. The optical device according to claim 5, further comprising an optical barrier (32) which is opaque to the first light radiation (7), said optical barrier (32) being arranged in the cavity (27) of said emitting apparatus (1) between said light source (6) and said first aperture (2) so as to intercept the first light radiation (7), preventing the first light radiation from directly reaching said first aperture (2).

8. The optical device according to claim 1, wherein said core (13) of said optical guide (9) has a circular cross-section which is constant over the entire longitudinal extent of said optical guide (9).

9. The optical device according to claim 1, wherein said core (13) is a cavity which comprises at least one non-diffuse substance in the gaseous state which is substantially transparent to radiation with a wavelength included in said predefined spectral range, or said core (13) is a solid body which is constructed from non-diffusive material which is substantially transparent to radiation with a wavelength which is included in said predefined spectral range.

10. The optical device according to claim 2, further comprising an optical receiver (25) which is arranged to receive and collect at least a portion of said first light signal (19) or a second light signal (26) which passes through said first aperture (2), said second light signal (26) corresponding to at least a portion of the excitation radiation (3) which is reflected by said reference sample (21) when the optical device (100) is in said second operating condition.

11. The optical device according to claim 10, further comprising a spectrophotometer (28) which is operatively connected to said optical receiver (25) in order to receive a light radiation (29) which is transmitted by said optical receiver (25) on the basis of said first light signal (19) or said second light signal (26) received.

12. The optical device according to claim 1, further comprising a casing (30) enclosing said emitting apparatus (1).

13. The optical device according to claim 12, wherein said optical guide (9) is fixed in a removable manner to said casing (30).

14. The optical device according to claim 13, wherein said optical guide (9) is fixed in a removable manner to said casing by means of a sleeve (9a) which contains said optical guide (9).

15. The optical device according to claim 12, wherein said guide (9) extends at least partially outside said casing (30).

16. The optical device according to claim 15, wherein said outlet aperture (15) of said optical guide (9) is external to said casing (30).

17. The optical device according to claim 1, wherein said optical guide (9) extends longitudinally along a direction defining the optical axis (12) of said optical guide (9), and wherein the extension of said gap (20) along the direction of said optical axis (12) is equal to, or lower than, 10% of the extension of said core (13) along a direction perpendicular to said optical axis (12).

18. The optical device according to claim 1, wherein said optical guide (9) extends longitudinally along a direction which defines the optical axis (12) of said optical guide (9), and wherein the longitudinal extent of said optical guide (9) is equal to, or greater than, at least four times the extension of said gap (20) along the direction of said optical axis (12).

19. The optical device according to claim 1, wherein said optical device (100) comprises an optical component (38) arranged within said optical guide (9), wherein said optical component (38), which consists of a single lens or comprises a lens assembly, extends into said core (13) and is configured to change an angle of view framed through said outlet aperture (15).

20. An optical system (200) comprising an optical device (100) according to claim 1, and a hollow body (33) comprising a wall (34) which is provided with an internal surface (35) which delimits a containment zone (36) for an unknown sample (16), said wall (34) being provided with a through-hole (37) which is configured to receive said optical guide (9) of said optical device (100) in such a manner that the outlet aperture (15) of said optical device (100) is directed towards said containment zone (36) in order to illuminate an unknown sample (16) in said containment zone (36) by means of an excitation radiation (3).

21. An agricultural machine or an industrial machine (300) comprising an optical system (200) according to claim 20.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0158] Features and further advantages of the invention will be more apparent from the following detailed description of preferred, though non-exclusive embodiments thereof, which are illustrated, for exemplary and non-limiting purposes, with reference to the accompanying drawings wherein:

[0159] FIG. 1 is a schematic section view of an optical device according to an embodiment of the invention and in a first operating condition, provided with an additional optical component for the correction of the framed field, installed inside the optical guide

[0160] FIG. 2 shows the optical device of FIG. 1 without an additional optical component, seen in section, in a second operating condition, and

[0161] FIG. 3 is a schematic section view of an optical system and machine according to an embodiment of the invention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0162] Referring initially to FIG. 1, an optical device according to an embodiment of the invention is globally indicated by number 100.

[0163] The optical device 100 comprises an emitting apparatus 1 provided with a first aperture 2 and suitable for emitting an excitation radiation 3 through the first aperture 2.

[0164] Excitation radiation 3 comprises light radiation having wavelengths included in a predefined spectral range (900 nm-1700 nm).

[0165] The first aperture 2 defines a first plane surface 4 of the emitting apparatus 1.

[0166] In particular, the emitting apparatus 1 comprises an integrating sphere 5 that is internally hollow and provided with the first aperture 2. The cavity 27 is delimited by a spherical internal surface 8.

[0167] The emitting apparatus 1 also comprises a light source 6 suitable for projecting a first radiation 7 onto the internal surface 8 of the integrating sphere 5. The inner surface 8 of the integrating sphere 5 is suitable for reflecting the first light radiation 7 thus giving rise to the excitation radiation 3.

[0168] Referring to the figures, the optical device 100 comprises an optical barrier 32 that is opaque to the first light radiation 7. The optical barrier 32 is arranged in the cavity 27 of the emitting apparatus 1 between said light source 6 and the first aperture 2 so as to intercept the first light radiation 7, preventing it from directly reaching the first aperture 2.

[0169] The optical device 100 also comprises an optical guide 9 longitudinally extended between a first end thereof 10 and a second end thereof 11. The longitudinal extension of the optical guide 9 defines the optical axis 12 of the optical guide.

[0170] The optical guide 9 is internally provided with a core 13 defining an inlet aperture 14 at the first end 10 and an outlet aperture 15 at the second end 11.

[0171] The core 13 shown in the figures is a cavity. Optionally, the inlet aperture and/or the outlet aperture are closed by a corresponding optical window 31 that is transparent to the light radiation 3 emitted by the emitting apparatus 1.

[0172] The cavity 13, if sealed on both ends 10 and 11 by transparent, sealed optical windows, may comprise at least one gas, more preferably a mixture of gases, such as: argon or nitrogen or air.

[0173] In case only the transparent optical window is present to close the inlet aperture 15, the cavity 13 will naturally include air.

[0174] Referring to FIG. 1, the inlet aperture 14 is arranged at the first aperture 2 such that the excitation radiation 3 emitted by the emitting apparatus 1 passes through it while the outlet aperture 15 is intended to face an unknown sample 16 when the optical device 100 is in an initial operating condition.

[0175] The optical guide 9 comprises a tubular body 17 extended longitudinally between the first end 10 and the second end 11. The tubular body 17 is internally provided with a reflective surface 18 delimiting the core 13.

[0176] In particular, the optical guide 9 is made functional thanks to the reflective surface 18, obtained by an appropriate treatment of the tubular body 17.

[0177] The optical guide 9 may be supported by a sleeve where it is contained and which allows it to be handled. The sleeve is indicated in FIG. 2 by reference number 9a.

[0178] The core 13 of the optical guide 9 has thus a constant circular cross-section along the longitudinal extent of the optical guide 9, and both the inlet aperture 14 and the outlet aperture 15 have a circular shape. The core 13 also allows the direct passage of rays of light radiation 3 that do not hit the reflective surface 18 and may therefore enter and exit directly from the inlet aperture 14 and the outlet aperture 15, respectively.

[0179] The reflective surface 18, made for example of 24kt gold, is suitable for reflecting the light radiation 3 projected into the cavity 13 through the inlet aperture 14 such as to propagate the light radiation 3 out of the optical guide 9 through the outlet aperture 15.

[0180] The reflective surface 18 is a regular optical surface with respect to radiation with a wavelength included in the above predefined spectral range.

[0181] With reference to FIG. 1, the optical device 100 comprises a gap 20 arranged between the first aperture 2 and the inlet aperture 14, the gap 20 being suitable for receiving a reference sample 21 such that the light radiation 3 emitted by the emitting apparatus 1 through the first aperture 2 is intercepted and reflected by the reference sample 21 when the optical device 100 is in a second operating condition, wherein the reference sample 21 is received in the gap 20.

[0182] FIG. 1 also shows an optical component 38 arranged within the optical guide 9. The optical component 38 is extended into the core 13 and is apt to change the angle of view framed through the outlet aperture 15 of the optical device 100. The optical component 38 may be with a positive equivalent focal length to reduce the angle of view framed by the outlet aperture 15, or with a negative equivalent focal length to enlarge the aforesaid field angle.

[0183] FIG. 2 shows the reference sample 21 received in the gap 20.

[0184] Referring to FIGS. 1 and 2, the inlet aperture 14 and the outlet aperture 15 define a plane inlet surface 22 and, respectively, a plane outlet surface 23 of the optical guide 9, such surfaces 22 and 23 and the first plane surface 4 of the emitting apparatus 1 being parallel to each other. The outlet plane surface 23 is also parallel to a measurement plane surface 24 that best approximates the surface of the unknown sample 16 when the optical device 100 is in the first operating condition.

[0185] The optical device 100 comprises an optical receiver 25 that is external to the optical guide and arranged to receive and collect at least a portion of a first light signal 19 or of a second light signal 26 passing through the first aperture 2, wherein the first light signal 19 corresponds to at least a portion of the excitation radiation 3 emitted by the outlet aperture 15 and reflected by the unknown sample 16 when the optical device 100 is in the first operating condition and the second light signal 26 corresponds to at least a portion of the light radiation 3 reflected by the reference sample 21 when it is received in the gap 20.

[0186] The optical receiver 25 is at least partially contained within the empty space (cavity) 27 delimited by the internal surface 8 of the integrating sphere 5 so as to receive part of the first light signal 19 or the second light signal 26 projected into the cavity 27 of the emitting apparatus 1 through the first aperture 2.

[0187] The optical receiver 25 shown in the figures is arranged as opposite to the first aperture 2 with respect to the centre of the cavity 27 of the emitting apparatus 1. Specifically, the optical receiver 25 is arranged at a second aperture 2a of the emitting apparatus 1, along the normal to the first plane surface 4 of the emitting apparatus 1.

[0188] The optical device 100 also comprises a NIR spectrophotometer 28 operatively connected to the optical receiver 25 to receive and analyse a light radiation 29 sent from the optical receiver 25 based on the first light signal 19 or the second light signal 26 received. Specifically, the light radiation 29 corresponds to the rays of the first light signal 19 or the second light signal 26 detected by the optical receiver 25.

[0189] The NIR spectrophotometer 28 is operatively connected to the optical receiver 25 by optical fibres, or the optical receiver is designed to input light radiation 29 directly into the spectrophotometer, i.e., without interposing any electromagnetic radiation transmission means.

[0190] In addition, the optical device 100 is provided with a casing 30 that contains the emitting apparatus 1. The optical guide 9 is removably fixed to the casing 30 by its own sleeve 9a.

[0191] The casing 30 encloses the spectrophotometer 28, the optical receiver 25, the emitting apparatus 1, and the reference sample 21.

[0192] FIG. 3 schematically shows an optical system and machine according to one embodiment of the invention. The optical system, globally indicated by number 200, comprises the optical device 100 and a hollow body (duct) 33 comprising a wall 34 provided with an internal surface 35 that delimits a containment zone 36 of an unknown sample 16.

[0193] The wall 34 of the duct 33 is provided with a through-hole 37 configured to receive the sleeve 9a containing the optical guide 9 such that the outlet aperture 15 of the optical device 100 faces the containment zone 36 to illuminate the unknown sample 16 by an excitation radiation 3.

[0194] A machine comprising the optical system 200 is indicated by number 300.

[0195] The invention thus solves the proposed problem while achieving multiple benefits.

[0196] In particular, the invention allows the unknown sample to be illuminated in a way that is equivalent, or in any case very similar, to the reference sample placed near the first aperture 2, even when the unknown sample is (conspicuously) spaced apart from the first aperture 2. In particular, the average statistical distribution of the illuminating radiation, as a function of the spatial location in terms of intensity, spectral content and angular distribution, are kept similar.

[0197] The invention also allows to accurately measure the relative reflectance of the unknown sample spaced apart (with respect to the reference sample inside the optical device) and consequently also the absolute value thereof.