Imaging system

Abstract

Present invention concerns a broadband short-wave infrared (SWIR) phosphor-conversion light emitting device including the same are disclosed in this application. More particularly the invention relates to the use of a material containing lead-halide-perovskite-comprising microcrystals, for instance in the form of films or coatings, as a phosphor-conversion material, for instance in a sheet form or as a material, for instance in the form of a sheet, as a layer or a coating, for light emission in the SWIR or the second near infrared wavelength region (NIR-II) between 900nm and 1600nm.

Description

[0001] IMAGING SYSTEM

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns in general an imaging system comprising a shortwave infrared broadband emission device.

[0004] BACKGROUND OF THE INVENTION

[0005] The short-wave infrared (SWIR) spectral region (700nm-2.5pm) is of great interest for a wide range of applications such as optical communications, sensing, medical imaging, security, chemical and nutritional screening, machine vision, and spectroscopy. In the SWIR region, the second NIR region (NIR-II, 1000-1880 nm) has recently emerged as a promising area for biomedical imaging and sensing due to the high degree of transparency exhibited by biological tissues in this wavelength window, reduced scattering, and lower tissue autofluorescence compared to the first NIR region (NIR-I, 700-900nm).

[0006] The conventional SWIR light source, a halogen lamp, can produce a broadband emission in the range of 400-2200nm, but generates lots of heat and operates at temperatures between 130-540°C depending on the power. Besides the low energy efficiency, the high operation temperature could cause thermal damage and limits its application in biology, medical imaging, and agriculture. Other emitters in the SWIR region including organic dyes and inorganic nanoparticles such as quantum dots (QDs), carbon nanotubes (CNTs), and rare-earth-doped nanoparticles have been also developed.

[0007] On the one hand, NIR-II lasers using various materials, including rare-earth-doped crystals, transition-metal-doped crystals, and colloidal quantum dots, have shown high output power, narrow spectral linewidth, and tunability, but their cost and complexity limit their widespread use.

[0008] On the other hand, SWIR LEDs have been developed using materials including indium gallium arsenide (InGaAs), GalnAsP, InP, lead sulfide (PbS), and lead selenide (PbSe). These LEDs have shown high efficiency and stability and have been used for SWIR imaging and sensing applications. However, their output power is still limited, and the emission bandwidth are often narrow. For instance, commercial SWIR LEDs often show a full-width-at-half-maximum (FWHM) of 40-60 nm. To achieve a broadband SWIR light source, it often requires an array of LEDs emitting at different wavelengths. Other than a direct LED, a phosphor-conversion material, for instance in the form of a sheet, as a layer or a coating, can be used to convert one wavelength of blue light to the targeted light emission wavelengths. For example, Ni2+-containing phosphor materials have been used to convert pump light of 600-670nm (the primary light source) to SWIR emission in the 1000-1700nm range with a FWHM of 350nm. (EP3800675A1). The phosphors, need to be prepared under high-temperature processes (1000-1500°C).

[0009] There is thus a clear need in the art for broadband short-wave infrared (SWIR) phosphor-conversion light emitting devices, where under second NIR region (NIR-II, 1000-1880 nm)

[0010] SUMMARY OF THE INVENTION

[0011] Other than a direct LED on a target, present invention uses a phosphor-conversion material, for instance a sheet or coating, containing lead-halide-perovskite- comprising microcrystals with a anyone of the compounds of the groups consisting of Br and Cl, as CsPbB microcrystals or CsPbCh microcrystals or a combination thereof, to convert 250nm-500nm wavelength light to emits wavelengths in the 900- 1600 nm range. Temperature modification of this phosphor-conversion material to change the SWIR emission intensity of emission light.

[0012] The invention relates to a broadband short-wave infrared (SWIR) phosphor- conversion light emitting device. More particularly the invention relates to the use of a material containing lead-halide-perovskite-comprising microcrystals, for instance in the form of films or coatings, as a phosphor-conversion material, for instance in a sheet form or as a material, for instance in the form of a sheet, as a layer or a coating, for light emission in the SWIR or the second near infrared wavelength region (NIR- II) between 900nm and 1600nm.

[0013] The present invention solves the problems of the related art by a phosphor- conversion material, for instance in the form of a sheet, as a layer or a coating, that can generate a broadband emission in the SWIR wavelength range from 900nm to 1600nm. The phosphor conversion material, for instance in the form of a sheet, as a layer or a coating, can be processed by room-temperature wet-chemistry and can be easily applied, deposited, or embedded on / in different substrates / hosting matrices of large areas. In accordance with the purpose of the invention, as embodied and broadly described herein, the invention is broadly drawn to an imaging system comprising a photosensitive area of photo-electric device to transform incoming radiation energy into electrical displacement signals [5] and a 250-600 nm electromagnetic radiation source [1], whereby the electromagnetic radiation source [1] is positioned to irradiate a wavelength converting material which wavelength converting material comprises lead-halide-perovskite-material with CsPbB microcrystals or with CsPbCh microcrystals or a combination thereof [2], to convert the 250-600 nm wavelength electromagnetic radiation into an electromagnetic radiation emission in a 900-1600 nm wavelength range and whereby the wavelength converting material [2] is positioned to irradiate the photosensitive area of photo-electric device [5] and whereby the imaging system further comprises an IR pass filter > 900 nm which is positioned in alignment with and between the wavelength converting material [2] and the photosensitive area of the photo-electric device [5].

[0014] In accordance with the purpose of the invention, as embodied and broadly described herein, the invention can be drawn to an imaging system comprising a photosensitive area of photo-electric device to transform incoming radiation energy into electrical displacement signals [5] and a 250-580 nm electromagnetic radiation source [1], whereby the electromagnetic radiation source [1] is positioned to irradiate a wavelength converting material which wavelength converting material comprises lead-halide-perovskite-material with CsPbB microcrystals or with CsPbCh microcrystals or a combination thereof [2], to convert the 250-580 nm wavelength electromagnetic radiation into an electromagnetic radiation emission in a 900-1600 nm wavelength range and whereby the wavelength converting material [2] is positioned to irradiate the photosensitive area of photo-electric device [5] and whereby the imaging system further comprises an IR pass filter > 900 nm which is positioned in alignment with and between the wavelength converting material [2] and the photosensitive area of the photo-electric device [5].

[0015] In accordance with the purpose of the invention, as embodied and broadly described herein, the invention can also be drawn to an imaging system comprising a photosensitive area of photo-electric device to transform incoming radiation energy into electrical displacement signals [5] and a 250-500 nm electromagnetic radiation source [1], whereby the electromagnetic radiation source [1] is positioned to irradiate a wavelength converting material which wavelength converting material comprises lead-halide-perovskite-material with CsPbB microcrystals or with CsPbCh microcrystals or a combination thereof [2], to convert the 250-500 nm wavelength electromagnetic radiation into an electromagnetic radiation emission in a 900-1600 nm wavelength range and whereby the wavelength converting material [2] is positioned to irradiate the photosensitive area of photo-electric device [5] and whereby the imaging system further comprises an IR pass filter > 900 nm which is positioned in alignment with and between the wavelength converting material [2] and the photosensitive area of the photo-electric device [5].

[0016] In one aspect of the invention, the photo-electric device [5] is functionally connected to a processor or computer system.

[0017] Another aspect of the invention is that the imaging system further comprises a transparent stage [2] for holding an object or a sample [3] to be imaged, whereby the transparent stage [2] is positioned in alignment with and between IR pass filter > 900 nm and the photosensitive area of the photo-electric device [5].

[0018] In still another aspect of the invention, the photo-electric device [5] is a camera incorporating a InGaAs sensor for measurement near-infrared wavelength in the range of 900-1700 nm.

[0019] In still another aspect of the invention, the imaging system as embodied or described here above, further comprising a cooling system to cool the wavelength converting material [2].

[0020] In still another aspect of the invention, the imaging system as embodied or described here above, the processor or computer system is adapted for constructing images from the recorded imaging data and for controlling the temperature of the wavelength converting material [2] so to regulate the electromagnetic radiation emission in a 900-1600 nm wavelength range, wherein the computer system is adapted for generating images of objects or samples irradiated by the wavelength converter [2] when the system is operational.

[0021] Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

[0022] The invention is further summarised in the following statements:

[0023] 1. An imaging system comprising a photosensitive area of photo-electric device to transform incoming radiation energy into electrical displacement signals [5] and a 250-600 nm electromagnetic radiation source [1],

[0024] - whereby the electromagnetic radiation source [1] is positioned to irradiate a wavelength converting material which wavelength converting material comprises lead-halide-perovskite-material with CsPbBr3 microcrystals or with CsPbCI3 microcrystals or a combination thereof [2], to convert the 250-600 nm wavelength electromagnetic radiation into an electromagnetic radiation emission in a 900 - 1600 nm wavelength range, and

[0025] - whereby the wavelength converting material [2] is positioned to irradiate the photosensitive area of photo-electric device [5], and

[0026] - whereby the imaging system further comprises an IR pass filter > 900 nm which is positioned in alignment with and between the wavelength converting material [2] and the photosensitive area of the photo-electric device [5].

[0027] 2. An imaging system according to statement 1, whereby the electromagnetic radiation source [1] is a 250-580 nm electromagnetic radiation source [1].

[0028] 3. The imaging system according to statement 1 or 2, whereby the photo-electric device [5] is functionally connected to a processor or computer system.

[0029] 4. The imaging system according to any one of statements 1 to 3, further comprising a transparent stage [2] for holding an object or a sample [3] to be imaged, whereby the transparent stage [2] is positioned in alignment with and between IR pass filter > 900 nm and the photosensitive area of the photo-electric device [5].

[0030] 5. The imaging system according to any one of statements 1 to 4, whereby the photo-electric device [5] is a camera incorporating a InGaAs sensor for measurement of near-infrared light with a wavelength in the range of 900-1700 nm.

[0031] 6. The imaging system according to any one of the statements 1 to 5, further comprising a heating system to heat the wavelength converting material [2].

[0032] 7. The imaging system according to any one of the statements 1 to 6, whereby the processor or computer system is adapted for constructing images from the recorded imaging data and for controlling the temperature of the wavelength converting material [2] so to regulate the electromagnetic radiation emission in a 900-1600 nm wavelength range, wherein the computer system is adapted for generating images of objects or samples irradiated by the wavelength converter [2] when the system is operational.

[0033] Detailed Description

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein :

[0036] FIG. 1 illustrates the absorption (dotted line) and SWIR emission (full line) spectra of CsPbB microcrystals (measured as powder in quartz cuvette)

[0037] FIG. 2 illustrates a comparison of the CsPbB SWIR emission spectrum with the absorption of biological samples (figure by Dr. Dominik J. Naczynski, Stanford University, adapted from Smith et al. (2009) Nat Nanotechnol. 4, 710.)

[0038] FIG. 3 is a schematic view comprises panel A and B, the panel A (Figure 3a) illustrates a simplified schematic of the imaging setup in transmission mode using CsPbB as SWIR light source and panel B (Figure 3b) illustrates a simplified schematic of the imaging setup in reflection mode using ambient SWIR light. The technical elements are indicated by a number code whereby 1 = Blue CW laser light (488 nm) guided through optical fiber, 2 = CsPbB film or crystals generating SWIR light, 3 = the Object, 4 = the IR pass filter (> 900 nm), 5 = the InGaAs camera (900- 1700 nm) and 6 is the SWIR light from ambient room lighting (TL lamp).

[0039] FIG. 4 provides a photographic of an insect in 3 photo panels (A, B & C) whereby panel A illustrates the image of an insect under ambient light, observed with a visible- light camera, panel B illustrates the image of the same insect under ambient light, observed with InGaAs camera (reflection mode) and panel C illustrates the image of the same insect illuminated from below by SWIR light from the CsPbB film, observed with InGaAs camera (transmission mode). Note that the body of the insect is semitransparent for SWIR light.

[0040] FIG. 5 provides a photographic of an insect in 2 photo panels (A & B) whereby panel A illustrates the image of a sitophilus oryzae under ambient light, observed with a visible-light camera (Wikipedia) and panel B illustrates the image of a Sitophilus oryzae illuminated from below by SWIR light from the CsPbBr3 film, observed with InGaAs camera. FIG. 6 illustrates the temperature dependence of the SWIR emission intensity of CsPbB microcrystals.

[0041] The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended embodiments and equivalents thereof.

[0042] The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended embodiments and equivalents thereof.

[0043] Several documents are cited throughout the text of this specification. Each of the documents herein (including any manufacturer's specifications, instructions etc.) are hereby incorporated by reference; however, there is no admission that any document cited is indeed prior art of the present invention.

[0044] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the embodiments. The drawings described are only schematic and are nonlimiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

[0045] Furthermore, the terms first, second, third and the like in the description and in the embodiments, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0046] Moreover, the terms top, bottom, over, under and the like in the description and the embodiments are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein. It is to be noticed that the term "comprising", used in the embodiments, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to the devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

[0047] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

[0048] Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the embodimented invention requires more features than are expressly recited in each embodiment. Rather, as the following embodiments reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the embodiments following the detailed description are hereby expressly incorporated into this detailed description, with each embodiment standing on its own as a separate embodiment of this invention.

[0049] Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following embodiments, any of the embodiments can be used in any combination.

[0050] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

[0051] Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein.

[0052] It is intended that the specification and examples be considered as exemplary only. Each and every embodiment is incorporated into the specification as an embodiment of the present invention. Thus, the embodiments are part of the description and are a further description and are in addition to the preferred embodiments of the present invention.

[0053] Each of the embodiments set out a particular embodiment of the invention.

[0054] The following terms are provided solely to aid in the understanding of the invention.

[0055] Definitions

[0056] In a distribution, full width at half maximum (FWHM) is the difference between the two values of the independent variable at which the dependent variable is equal to half of its maximum value. In other words, it is the width of a spectrum curve measured between those points on the y-axis which are half the maximum amplitude. Half width at half maximum (HWHM) is half of the FWHM if the function is symmetric. The term full duration at half maximum (FDHM) is preferred when the independent variable is time.

[0057] Particular and preferred aspects of the invention are set out in the accompanying independent and dependent embodiments. Features from the dependent embodiments may be combined with features of the independent embodiments and with features of other dependent embodiments as appropriate and not merely as explicitly set out in the embodiments.

[0058] Thus, the embodiments following the detailed description are hereby expressly incorporated into this detailed description, with each embodiment standing on its own as a separate embodiment of this invention.

[0059] EXAMPLES

[0060] Example 1

[0061] As demonstrated in figure 4 a photographic of an insect was made by the imaging system of present invention. The insect is shown in 3 photo panels (A, B & C) whereby panel A illustrates the image of an insect under ambient light, observed with a visible- light camera, panel B illustrates the image of the same insect under ambient light, observed with InGaAs camera (reflection mode) behind an IR pass filter (>900nm), and panel C illustrates the image of the same insect illuminated from below by SWIR light from the CsPbB film, observed with the InGaAs camera (transmission mode) behind an IR pass filter (>900nm). Note that the body of the insect is semitransparent for SWIR light so that the cerebral ganglion and intestine of the insect could be imaged.

[0062] Example 2

[0063] FIG. 5 provides a photographic of an insect in 2 photo panels (A & B) whereby panel A illustrates the image of a Sitophilus oryzae under ambient light, observed with a visible-light camera (Wikipedia) and panel B illustrates the image of a Sitophilus oryzae illuminated from below by SWIR light from the CsPbB film, observed with InGaAs camera. The Sitophilus oryzae's internal organs, including the ant, midgut, somatic bacteriomes, and the ovaries are clearly visible in the SWIR image.

[0064] Example 3

[0065] We also demonstrated the temperature dependence of the SWIR emission intensity of CsPbB microcrystals as is demonstrated in figure 6.

[0066] 3.1. Example of CsPbB microcrystals material preparation

[0067] Stoichiometric amounts of CsBr (0.633 mmol) and PbB (0.633 mmol) are dissolved in 1 mL dimethyl sulfoxide (DMSO) by vigorous stirring for 30 minutes until a semitransparent solution is obtained. Subsequently, 1 mL pure HBr is added dropwise to the precursor solution under constant stirring. An orange precipitate appears instantly, marking the formation of CsPbBr3 microcrystals. The product is then centrifuged (8500 rpm, 2 min) and washed twice with 1 mL ethanol. Finally, the powder is dried in vacuum at room temperature.

[0068] 3.2. Second example of CsPbCIxBr^-x; material preparation

[0069] CsPbCIxBr^-x; microcrystals with mixed halide content are synthesized starting from CsBr (0.633 mmol), PbB ( 0.211*(3-x) mmol) and PbC (0.211*x mmol), in which 0<x<3. The same protocol is then applied as described for the pure CsPbB microcrystals. 3.3. Example of imaging acquisition

[0070] Objects of interest are placed on a glass substrate. The sample is then positioned in the imaging system as illustrated in the figure 3A (transmission) or 3B (reflection mode).

Claims

Claims1. An imaging system comprising a photosensitive area of photo-electric device to transform incoming radiation energy into electrical displacement signals [5] and a 250-600 nm electromagnetic radiation source [1],- whereby the electromagnetic radiation source [1] is positioned to irradiate a wavelength converting material which wavelength converting material comprises lead-halide-perovskite-material with CsPbB microcrystals or with CsPbCh microcrystals or a combination thereof [2], to convert the 250-600 nm wavelength electromagnetic radiation into an electromagnetic radiation emission in a 900 - 1600 nm wavelength range, and- whereby the wavelength converting material [2] is positioned to irradiate the photosensitive area of photo-electric device [5], and- whereby the imaging system further comprises an IR pass filter > 900 nm which is positioned in alignment with and between the wavelength converting material [2] and the photosensitive area of the photo-electric device [5].

2. An imaging system according to claim 1, whereby the electromagnetic radiation source [1] is a 250-580 nm electromagnetic radiation source [1].

3. The imaging system according to claim 1 or 2, whereby the photo-electric device [5] is functionally connected to a processor or computer system.

4. The imaging system according to any one of claims 1 to 3, further comprising a transparent stage [2] for holding an object or a sample [3] to be imaged, whereby the transparent stage [2] is positioned in alignment with and between IR pass filter > 900 nm and the photosensitive area of the photo-electric device [5].

5. The imaging system according to any one of claims 1 to 4, whereby the photoelectric device [5] is a camera incorporating a InGaAs sensor for measurement of near-infrared light with a wavelength in the range of 900-1700 nm.

6. The imaging system according to any one of the claims 1 to 5, further comprising a heating system to heat the wavelength converting material [2].

7. The imaging system according to any one of the claims 1 to 6, whereby the processor or computer system is adapted for constructing images from the recorded imaging data and for controlling the temperature of the wavelength converting material [2] so to regulate the electromagnetic radiation emission in a 900-1600 nm wavelength range, wherein the computer system is adapted for generating images of objects or samples irradiated by the wavelength converter [2] when the system is operational.

Images