DE102018200124A1 - Illumination module for a spectrometer, spectrometer, method for operating a lighting module and method for producing a spectrometer - Google Patents

Abstract

The invention relates to a lighting module (100) for a spectrometer. The illumination module (100) comprises a white light source (102) having a laser source (104) for emitting a laser radiation and a conversion material (106) for emitting a directed white light radiation (108) using the laser radiation, a monochromator (110) for generating a monochromatic radiation (112) with changeable wavelength range using the white light radiation (108) and a light exit point (114) for directing the monochromatic radiation (112) onto a sample to be analyzed by means of the spectrometer (200).

Description

State of the art

The invention is based on a device or a method according to the preamble of the independent claims. The subject of the present invention is also a computer program.

Various technical applications require tunable wavelength monochromatic light sources. This is of particular interest in spectroscopy. Apart from expensive and technically complex methods such as lasers with external resonator, there is virtually no light source that already produces light of a narrow, but at the same time variable wavelength range. Although laser or LEDs emit a more or less monochromatic light, the wavelength is usually fixed and can not be adjusted. Combinations of red, green and blue light-emitting diodes, as in displays, are not to be understood as tunable sources in the relevant sense here. With such methods, only a color impression is produced. Physically, there is a mixture of always the same three wavelengths, with only their proportions vary. Tunable light sources, such as for laboratory applications, usually consist of a broadband, white light source and a downstream monochromator.

For example, the Czerny Turner monochromator is known. The light of the source is collimated by a concave mirror and directed to a grid.

Light of different wavelengths is diffracted there at a different angle and hits a second concave mirror, which focuses the collimated rays, so that each wavelength hits a certain point. An exit slit selects one of these bundles. Which wavelength this is, can be varied by turning the grid.

These commercially available light sources are usually large and expensive. There are limits to miniaturization because the resolution decreases with shorter beam paths, but the scattered light intensity increases, ie. H. The light intensity of unwanted wavelengths in the output beam is getting stronger. Basically, a compromise between size of the input aperture and resolution is to be made. Smaller apertures improve resolution but cost intensity because broadband light sources have a poor etendue (product of emitting surface and solid angle of radiation) and can not be arbitrarily focused, such as a laser.

Disclosure of the invention

Against this background, with the approach presented here, an illumination module for a spectrometer, a spectrometer, a method for operating a lighting module for a spectrometer, a device using this method, a corresponding computer program and a method for producing a spectrometer according to the main claims are presented , The measures listed in the dependent claims advantageous refinements and improvements of the independent claim device are possible.

The large Etendue broadband light sources such as gas discharge lamps, incandescent lamps, halogen lamps or light-emitting diodes can limit energy efficiency, resolution and stray light suppression. Optimizing one of the parameters is usually possible, but often involves compromising other parameters. Typical light sources for spectrometers use, for example, halogen light sources with 20 to 200 W power and produce about 1 nm wide spectral bands with at best 20 μW.

In contrast, the approach presented here creates a lighting arrangement consisting of a compact and efficient white light source in combination with a monochromator, such as a Czerny Turner monochromator. The white light source has a special conversion material which, for example when excited with red laser light, shows a directed white light emission. Physically noteworthy is not only the directional emission, but also the fact that photons can be converted from low to higher energies, ie shorter wavelengths. Advantageously, a laser source, preferably a low-cost laser diode, can be combined with this conversion material to form a white light source with a smaller etendue. By using such a tunable white light source, for example, a reflection spectrometer with a particularly compact design is made possible.

• eine Weißlichtquelle mit einer Laserquelle zum Aussenden einer Laserstrahlung und einem Konversionsmaterial zum Aussenden einer gerichteten Weißlichtstrahlung unter Verwendung der Laserstrahlung;
• einen Monochromator zum Erzeugen einer monochromatischen Strahlung mit änderbarem Wellenlängenbereich unter Verwendung der Weißlichtstrahlung; und
• eine Lichtaustrittsstelle zum Lenken der monochromatischen Strahlung auf eine mittels des Spektrometers zu analysierende Probe.

A lighting module for a spectrometer is presented, the lighting module having the following features:

• a white light source having a laser source for emitting a laser radiation and a conversion material for emitting a directed white light radiation using the laser radiation;
• a monochromator for generating a monochromatic radiation with changeable Wavelength range using white light radiation; and
• a light exit point for directing the monochromatic radiation to a sample to be analyzed by means of the spectrometer.

A spectrometer may be understood to mean a device for measuring or displaying a spectrum. A white light source can be understood as a light source for emitting broadband electromagnetic radiation. By a laser source, for example, a laser diode or an arrangement of a plurality of laser diodes can be understood. A conversion material may, for example, be understood as meaning a layer having a core of inorganic nanocrystals and a surface coated with organic ligands. The conversion material can be applied to the laser source, for example in the form of a layer, or designed as a separate component. A monochromator can be understood to mean an optical device for the spectral isolation of a specific wavelength from an incidental amount of electromagnetic radiation. For example, the monochromator can be designed as a Czerny Turner monochromator. The wavelength of the monochromatic radiation can be changed, for example, by adjusting a diffraction grating to diffract the white light radiation. A light exit point can be understood, for example, to be an opening in a housing of the illumination module or a light-transmitting section of the illumination module.

For example, the light source may have at least one optical element arranged between the laser source and the conversion material for directing the laser radiation onto the emission element. Additionally or alternatively, the light source may comprise at least one further optical element connected downstream of the conversion material, for example in the form of a diaphragm, for focusing the white-light radiation onto a component of the monochromator.

According to one embodiment, the laser source may comprise at least one laser diode. Additionally or alternatively, the laser source may be configured to emit infrared radiation as the laser radiation. Additionally or alternatively, the conversion material may be amorphous. As a result, the lighting module can be produced in a particularly cost-effective manner and operated efficiently.

According to a further embodiment, the monochromator can comprise at least one collimating element for collimating the white-light radiation, at least one diffraction element for generating the monochromatic radiation by wavelength-dependent bending of the white-light radiation, at least one deflecting element for directing the monochromatic radiation onto the light exit point or a combination of at least two of said optical elements respectively. By a collimating element, for example, a concave mirror or other rectifying element can be understood. For example, a diffractive element can be understood to mean an adjustable diffraction grating, for example a MEMS grating. For example, a deflecting element can also be understood to mean a concave mirror or another reflecting element. As a result, the monochromator can be produced with a small number of components and thus particularly cost-effectively and compactly.

It is particularly advantageous if the diffraction element is designed as an adjustable diffraction grating. The collimation element and / or the deflecting element can be designed as a concave mirror. As a result, the lighting module can be realized as compact as possible.

The illumination module may according to another embodiment comprise a capsule and a closure element for closing the capsule to a housing. In this case, the white light source and the monochromator can be arranged or arranged in the housing. Under a capsule, for example, a cup-shaped component can be understood. A closure element may be understood to mean, for example, a plate-shaped lid. As a result, the lighting module can be protected from environmental influences.

The white light source and / or the diffraction element can be arranged on the closure element or can be arranged. Additionally or alternatively, the collimating element and / or the deflecting element can be arranged or arranged on an inner wall of the capsule. Also by this embodiment, the design of the lighting module can be kept as compact as possible.

It is particularly advantageous if the closure element is designed as a printed circuit board. The closure element may additionally or alternatively have the light exit point. As a result, the closure element can serve for making electrical contact with the white light source or components of the monochromator. Thus, additional components for electrical contact can be omitted.

• einem Beleuchtungsmodul gemäß einer der vorstehenden Ausführungsformen; und
• einem Detektor zum Detektieren einer von der Probe reflektierten Strahlung, wobei der Detektor am Beleuchtungsmodul angeordnet oder anordenbar ist.

The approach presented here also creates a spectrometer with the following features:

• a lighting module according to one of the preceding embodiments; and
• a detector for detecting a radiation reflected from the sample, wherein the detector is arranged or can be arranged on the illumination module.

A detector may be understood to mean a photosensitive component such as, for example, a CMOS or CCD sensor, a photodiode or a phototransistor or an array of a plurality of such photosensitive components.

In one embodiment, the spectrometer may include a translucent cap. The cap can form a detector housing with the closure element. In this case, the detector may be arranged in the detector housing so that the detector and the light exit point are not opposite each other. Under a translucent cap, for example, a transparent plastic cap can be understood. The detector may be mounted, for example, on a side facing away from the housing side of the closure element. As a result, the detector can be integrated into the spectrometer in a space-saving and protected from environmental influences.

In addition, the spectrometer may have an opaque blocking element. The blocking element may be arranged in the detector housing between the detector and the light exit point in order to obstruct a direct light path between the detector and the light exit point. A mirror element may be understood to mean a component made of an opaque material. As a result, it is possible to prevent light emerging from the housing from falling directly onto the detector. Thus, misdetections can be avoided.

• Einschalten der Laserquelle, um die Weißlichtstrahlung bereitzustellen; und
• Ansteuern des Monochromators ansprechend auf das Einschalten, um den Wellenlängenbereich der monochromatischen Strahlung zu ändern.

Furthermore, the approach presented here creates a method for operating a lighting module according to one of the preceding embodiments, wherein the method comprises the following steps:

• Turning on the laser source to provide the white light radiation; and
• Driving the monochromator in response to turning on to change the wavelength range of the monochromatic radiation.

This method can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

The approach presented here also creates a device that is designed to perform the steps of a variant of a method presented here in appropriate facilities to drive or implement. Also by this embodiment of the invention in the form of a device, the object underlying the invention can be solved quickly and efficiently.

For this purpose, the device may comprise at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, at least one interface to a sensor or an actuator for reading sensor signals from the sensor or for outputting data or control signals to the sensor Actuator and / or at least one communication interface for reading or outputting data embedded in a communication protocol. The arithmetic unit may be, for example, a signal processor, a microcontroller or the like, wherein the memory unit may be a flash memory, an EPROM or a magnetic memory unit. The communication interface can be designed to read or output data wirelessly and / or by line, wherein a communication interface that can read or output line-bound data, for example, electrically or optically read this data from a corresponding data transmission line or output in a corresponding data transmission line.

In the present case, a device can be understood as meaning an electrical device which processes sensor signals and outputs control and / or data signals in dependence thereon. The device may have an interface, which may be formed in hardware and / or software. In the case of a hardware-based embodiment, the interfaces can be part of a so-called system ASIC, for example, which contains a wide variety of functions of the device. However, it is also possible that the interfaces are their own integrated circuits or at least partially consist of discrete components. In a software training, the interfaces may be software modules that are present, for example, on a microcontroller in addition to other software modules.

Also of advantage is a computer program product or computer program with program code which can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and for carrying out, implementing and / or controlling the steps of the method according to one of the embodiments described above is used, especially when the program product or program is executed on a computer or a device.

Finally, the approach presented here provides a method for producing a spectrometer according to one of the preceding embodiments, wherein the method comprises the following step:

Place the detector on the lighting module to make the spectrometer.

• 1 eine schematische Darstellung eines Beleuchtungsmoduls gemäß einem Ausführungsbeispiel;
• 2 eine schematische Darstellung eines Spektrometers gemäß einem Ausführungsbeispiel;
• 3 eine schematische Darstellung eines Spektrometers gemäß einem Ausführungsbeispiel;
• 4 eine schematische Darstellung einer Weißlichtquelle gemäß einem Ausführungsbeispiel;
• 5 eine schematische Darstellung einer Weißlichtquelle gemäß einem Ausführungsbeispiel;
• 6 eine schematische Darstellung einer Vorrichtung gemäß einem Ausführungsbeispiel;
• 7 ein Ablaufdiagramm eines Verfahrens zum Betreiben eines Beleuchtungsmoduls gemäß einem Ausführungsbeispiel; und
• 8 ein Ablaufdiagramm eines Verfahrens zum Herstellen eines Spektrometers gemäß einem Ausführungsbeispiel.

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. It shows:

• 1 a schematic representation of a lighting module according to an embodiment;
• 2 a schematic representation of a spectrometer according to an embodiment;
• 3 a schematic representation of a spectrometer according to an embodiment;
• 4 a schematic representation of a white light source according to an embodiment;
• 5 a schematic representation of a white light source according to an embodiment;
• 6 a schematic representation of a device according to an embodiment;
• 7 a flowchart of a method for operating a lighting module according to an embodiment; and
• 8th a flowchart of a method for producing a spectrometer according to an embodiment.

In the following description of favorable embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and similar acting, with a repeated description of these elements is omitted.

1 shows a schematic representation of a lighting module 100 according to an embodiment. The lighting module 100 for a spectrometer, such as a microspectrometer, includes a white light source 102 consisting of a laser source 104 and a conversion material 106 , The laser source 104 is designed to emit a laser radiation through which the conversion material 106 for emitting a directed white light radiation 108 is stimulated. Exemplary are the laser source 104 , such as a laser diode, and the conversion material 106 designed as a compact layer composite. Furthermore, the lighting module includes 100 a monochromator 110 , which is adapted to the whiteness radiation 108 in a monochromatic radiation 112 disassemble. The monochromatic radiation 112 falls through a light exit point 114 to a sample to be analyzed by means of the spectrometer.

According to this embodiment, the monochromator 110 as a Czerny Turner monochromator with a collimation element 116 in the form of a first concave mirror for collimating the white light source 102 emerging white light radiation 108 , a diffraction element 118 for generating the monochromatic radiation 112 by wavelength-dependent bending of the white light radiation 108 , here by way of example in the form of an adjustable MEMS diffraction grating, and a deflecting element 120 in the form of a second concave mirror for deflecting and bundling the diffraction element 118 emanating monochromatic radiation 112 in the direction of the light exit point 114 executed.

To protect against environmental influences is the lighting module 100 with a housing consisting of a through a plate-shaped closure element 122 closed capsule 124 executed, the white light source 102 and the monochromator 110 are arranged within the housing. The closure element serves this purpose 122 as a carrier for the white light source 102 and the diffraction element 118 , The collimation element 116 and the deflecting element 120 are on the other hand, the closure element 122 opposite inner wall of the capsule 124 arranged. An example is the light exit point 114 as a the deflector 120 opposite passage opening in the closure element 122 realized. It is particularly advantageous if the closure element 122 , as in 1 shown as an example, as a printed circuit board for electrical contacting of the white light source 102 , the diffraction element 118 or other components of the spectrometer is realized.

1 shows an example of a particularly compact embodiment. It is on the closure element 122 a VCSEL (Vertical Cavity Surface Emitting Laser) as a laser source 104 and a MEMS grating as a diffraction element 118 arranged. A MEMS grating is to be understood as meaning a MEMS component which corresponds to a single-axis micromirror, but instead of a mirror surface carries a diffraction grating. The laser source 104 is with a layer of the conversion material 106 coated. Optionally includes the white light source 102 one on the conversion material 106 directly resting, for example imprinted panel 126 , The collimation element 116 and the deflecting element 120 are in the capsule 124 , which is, for example, a metal-coated injection molded part integrated. The capsule 124 is on the closure element 122 fixed and thus forms a housing for the lighting module 100 , It is beneficial if all other inner surfaces of the capsule 124 are blackened. It is also beneficial if the capsule 124 , at least one stray light reduction element 128 which serves to reduce the stray light in the housing and either as a component of the capsule 124 or by adding more parts to the capsule 124 is realized. The at the deflection 120 bundled monochromatic radiation 112 leaves the lighting module 100 for example, through an opening or hole in the closure element 122 , The wavelength of the emerging radiation 112 can be changed by adjusting the MEMS grating.

2 shows a schematic representation of a spectrometer 200 according to an embodiment. The spectrometer 200 includes, for example, a lighting module 100 as previously stated by 1 is described. It is at one of the housing of the lighting module 100 opposite side of the closure element 122 a detector 202 for detecting one of a sample 204 reflected radiation 206 appropriate. According to this embodiment, the detector 202 from a translucent cap 208 housed together with the closure element 122 a detector housing around the detector 202 and the light exit point 114 forms. The detector 202 is laterally offset from the light exit opening 114 arranged and thus this is not opposite. The detector housing is provided with a partition wall in the form of an opaque blocking element 210 executed. The blocking element 210 is between the detector 202 and the light exit point 114 arranged and prevented so that the out of the lighting module 100 exiting monochromatic radiation 112 on the direct way, ie without detouring over the sample 204 , on the detector 202 falls.

3 shows a schematic representation of a spectrometer 200 according to an embodiment. In contrast to 2 is the detector 202 according to this embodiment as an array along the closure element 122 realized lined up light-sensitive components.

The 2 and 3 show by way of example a microspectrometer according to an embodiment. Protected by the at least in some places transparent cap 208 located at the bottom of the closure element 122 For example, a photodiode that serves as a detector 202 acts. It is advantageous if a direct exposure of the detector 202 through the monochromatic radiation 112 by means of an opaque barrier, above also blocking element 210 called, is prevented. About reflection or scattering on the approximated sample 204 However, light can go to the detector 202 reach. By scanning the MEMS grating and the resulting wavelength change of the monochromatic radiation 112 it is possible to record a reflection or absorption spectrum. External light is, for example, by a reference measurement with the laser source switched off 104 eliminated.

Diffuse backscattering is especially good to measure when the sample 204 as in the 2 and 3 shown, directly on the cap 208 is set so that distances and interfaces are optimally defined.

With diffuse backscatter and defined object distance, it is also advantageous if multiple detectors or an array as a detector 202 is used as in 3 shown. The location of the light detection on the array then provides information about the penetration depth of the light paths in the sample 204 and the distance covered. This can be exploited on the one hand to determine a depth-dependent scattering or absorption, on the other hand to distinguish absorption and scattering properties.

There are numerous concepts for simple spectrometers, in particular miniaturized spectrometers. However, the sample is usually broadband illuminated while the spectrometer analyzes the backscattered light. The beam path goes from the light source to the sample, from there to the monochromator and from there finally to the detector. The main reason for this is that inexpensive broadband light sources do not emit directional, but have a large etendue. With such sources, a monochromator costs a great deal of intensity. Although its output has a lower etendue again, the light backscattered by a diffusely reflecting sample is again undirected and is only incompletely detected by the detector. It is advantageous if the detector is integrated in this case in the monochromator, because so at least the light passing through the monochromator is completely detected.

In a directional white light source, however, it is of great advantage if the light emitted by it is first conducted into the monochromator instead of giving away the low etendue in the scattering on the sample. Although this arrangement, in which the radiation from the source to the monochromator, from there to the sample and finally from the sample to the detector, the light diffusely reflected by the sample is undirected, but the spectral intensity is much higher.

4 shows a schematic representation of a white light source 102 according to an embodiment, such as the above with reference to 1 described white light source. In the simplest case, there is the white light source 102 from a laser diode as a laser source 104 and a conversion layer as conversion material 106 , The conversion layer, which is characterized in that it causes a directed emission by excitation with the laser radiation, depending on the embodiment realized free-standing or as a coating on a transparent substrate or directly to the laser source 104 applied. The generated white light radiation 108 is then emitted from a surface at least as large as the aperture of the laser source 104 is. The solid angle corresponds at least to the solid angle of the laser beam, but is rather slightly larger.

5 shows a schematic representation of a white light source 102 according to an embodiment. In contrast to 4 is the white light source 102 realized according to this embodiment with other optical elements, such as a lens 500 or a similar element between the laser source 104 and the conversion material 106 for focusing the laser source 104 emitted laser beam. A smaller beam cross-section of the laser beam and thus of the white-light emitting surface brings only in special cases advantages for the beam path (the etendue can not improve this), but the higher radiation density on the conversion material 106 may be necessary if efficient white light generation is to take place above a certain threshold. Shown is the aperture 126 ,

6 shows a schematic representation of a device 600 according to an embodiment. The device 600 serves for example for operating a lighting module, as described above with reference to FIG 1 to 5 is described. For this purpose, the device comprises 600 an activation unit 610 for turning on the laser source by outputting a corresponding turn-on signal 612 , A drive unit 620 is configured to use the turn-on signal 612 a drive signal 622 to provide for driving the monochromator. The drive signal 622 serves to change the wavelength range of the monochromatic radiation, for example by adjusting a diffraction grating of the monochromator.

7 shows a flowchart of a method 700 for operating a lighting module according to an embodiment. The procedure 700 For example, by the foregoing by means of 6 be executed described device. It is in one step 710 the laser source is turned on to provide the white light radiation. In a further step 720 In response to turning on the laser source, the monochromator is driven to change the wavelength range of the monochromatic radiation.

8th shows a flowchart as a method 800 for producing a spectrometer according to an embodiment. By means of the procedure 800 For example, the above with reference to the 2 and 3 described spectrometer can be produced. This will be done in an optional preparatory step 810 provided the lighting module and the detector. In a further step 820 For example, the illumination module and the detector are combined with each other by attaching the detector to the illumination module, such as the closure element of the illumination module.

If an exemplary embodiment comprises a "and / or" link between a first feature and a second feature, then this is to be read so that the embodiment according to one embodiment, both the first feature and the second feature and according to another embodiment either only first feature or only the second feature.

Claims (15)

Illumination module (100) for a spectrometer (200), wherein the illumination module (100) has the following features: a white light source (102) having a laser source (104) for emitting a laser radiation and a conversion material (106) for emitting a directional white light radiation (108) using the laser radiation; a monochromator (110) for generating a monochromatic radiation (112) having a changeable wavelength range using the white light radiation (108); and a light exit site (114) for directing the monochromatic radiation (112) onto a sample (204) to be analyzed by the spectrometer (200). Lighting module (100) according to Claim 1 in which the laser source (104) has at least one laser diode and / or is designed to emit infrared radiation as the laser radiation, and / or in which the conversion material (106) is amorphous. Illumination module (100) according to one of the preceding claims, wherein the monochromator (110) at least one collimating element (116) for collimating the white light radiation (108) and / or at least one diffraction element (118) for generating the monochromatic radiation (112) by wavelength-dependent bending the white light radiation (108) and / or at least one deflection element (120) for directing the monochromatic Radiation (112) on the light exit point (114). Lighting module (100) according to Claim 3 in which the diffraction element (118) is designed as an adjustable diffraction grating and / or the collimation element (116) and / or the deflection element (120) is designed as a concave mirror. Lighting module (100) according to one of the preceding claims, comprising a capsule (124) and a closure element (122) for closing the capsule (124) to a housing, wherein the white light source (102) and the monochromator (110) arranged in the housing or can be arranged are. Lighting module (100) according to Claim 3 and 5 or according to Claim 4 and 5 in which the white light source (102) and / or the diffraction element (118) is arranged or arrangeable on the closure element (122) and / or the collimation element (116) and / or the deflection element (120) are arranged on an inner wall of the capsule (124) or can be arranged. Lighting module (100) according to Claim 5 or 6 in which the closure element (122) is designed as a printed circuit board and / or has the light exit point (114). Spectrometer (200) with the following features: a lighting module (100) according to one of the preceding claims; and a detector (202) for detecting a radiation (206) reflected from the sample (204), the detector (202) being arranged or arrangeable on the illumination module (100). Spectrometer (200) according to Claim 8 , with a lighting module (100) according to one of Claims 5 to 7 and a translucent cap (208), wherein the cap (208) forms a detector housing with the closure member (122) and the detector (202) is disposed in the detector housing such that the detector (202) and the light exit site (114) are not opposed to each other , Spectrometer (200) according to Claim 9 lens with an opaque barrier member (210) disposed in the detector housing between the detector (202) and the light exit site (114) to obstruct a direct light path between the detector (202) and the light exit site (114). A method (700) for operating a lighting module (100) according to any one of Claims 1 to 7 wherein the method (700) comprises the steps of: turning on (710) the laser source (104) to provide the white light radiation (108); and driving (720) the monochromator (110) in response to the turn-on (710) to change the wavelength range of the monochromatic radiation (112). Method (800) for producing a spectrometer (200) according to one of the Claims 8 to 10 wherein the method (800) comprises the step of: arranging (820) the detector (202) on the illumination module (100) to produce the spectrometer (200). Apparatus (600) comprising units (610, 620) adapted to perform the method (700) of Claim 11 execute and / or control. Computer program adapted to perform the method (700) according to Claim 11 execute and / or control. Machine-readable storage medium on which the computer program is based Claim 14 is stored.

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