DE102010047061A1 - Optical spectrometer has several optoelectronic detection elements arranged in detector in series along incident direction of diffracted light, which have optoelectronic transducers to detect different spectral detection ranges - Google Patents

Abstract

The optical spectrometer (10) has a housing which comprises an inlet opening (1), a diffraction grating (2) and a spatially resolving detector (3). The light (L) passes into the diffraction grating through inlet opening. Several optoelectronic detection elements are arranged in detector in series along incident direction of diffracted light (S). Each detection element is provided with optoelectronic transducers (3-1-A,3-10-A,3-10-B,3-17-B,3-18-A,3-18-B) for detecting different spectral detection ranges simultaneously, and delivering electric signals.

Description

The invention relates to an optical spectrometer with a housing, which has an entrance slit, a diffraction grating and a spatially resolving detector with a plurality of optoelectronic detection elements, wherein the diffraction grating diffracts light, which falls through the entrance slit in the housing, depending on wavelength in the direction of different detector elements. Moreover, in such spectrometers further optical elements such as lenses or mirrors can be arranged in a known manner.

For the purposes of the invention, light is any electromagnetic radiation that can be manipulated by optical means and, in particular, includes ultraviolet (UV) and infrared (IR) radiation.

Depending on the design, optoelectronic semiconductor detectors have a spectrally limited detection sensitivity for light. In order to be able to measure samples spectrometrically in a broad spectral range, a plurality of spectrometers with spectrally different detection ranges are generally used, wherein the detection ranges of the different spectrometers typically partially overlap each other spectrally. Such a spectrometer system is, for example, in DE 10010213 A1 disclosed.

Different spectral detection ranges are present when the semiconductor detectors of the two spectrometers have a different spectral sensitivity curve, that is to say when the lower limit wavelengths of the spectrometers are not identical or the upper limit wavelengths of the spectrometers are not identical. The cut-off wavelengths of the detection range of a spectrometer describe the spectral detection range of its detector, which is defined for example in that the detector has at least 10% of its maximum spectral sensitivity in the relevant wavelength range. Regardless of this specification, a detector can also be used in certain applications in a broader spectral range, if the then limited sensitivity is sufficient.

For example, for a total spectral range from 400 nm to 1680 nm, a first spectrometer with a silicon detector (Si) having a detection range of 400 nm to 1100 nm, and a second spectrometer with an indium gallium arsenide detector (InGaAs ), which has a detection range of 950 nm to 1680 nm, used because Si detectors only up to a maximum of 1100 nm have a useful detection sensitivity. Near the upper cutoff wavelength, the detection sensitivity of Si detectors is low and they have a strong temperature dependence with respect to the signal amplitude they emit. For the longer wavelength portion of the spectrum, a more expensive InGaAs detector than the Si detector is typically used in the second spectrometer, whose detection sensitivity is advantageously less temperature dependent but has higher noise.

However, the use of two or more spectrometers in addition to the required large space still has the disadvantage that the optical paths from the sample to the respective detectors are different and that the spectrometer usually have a different optical structure, so that in the measured spectrum Discontinuity in the form of a jump arises. For sensitive applications, this leads to measurement errors.

The invention is therefore based on the object to improve a spectrometer of the type mentioned in order to allow for sensitive applications higher measurement accuracy.

The object is achieved by a spectrometer having the features specified in claim 1, and by an operating method having the features specified in claim 12.

Advantageous embodiments of the invention are specified in the subclaims.

According to the invention, at least one of the detection elements has two (or more) optoelectronic transducers which have a different composition for the simultaneous detection of two (or correspondingly many) different spectral detection regions, emit separate electrical signals and along an incident direction of the diffracted light onto the detector arranged one behind the other.

In the context of the invention, an optoelectronic transducer is a component that absorbs incident photons by means of a semiconductor material and into electrical charge carriers (electrons and holes). able to transform. Examples of optoelectronic transducers are photodiodes, phototransistors and photoresistors.

For the purposes of the invention, the simultaneous detection of different spectral detection ranges in different optoelectronic transducers means that a first spectral portion of the diffracted light incident on the detector is at least partially absorbed in the first optoelectronic transducer, while a second spectral portion of the diffracted, on the detector falling light penetrates the first opto-electronic transducer (substantially) undiminished and at least partially absorbed in the second opto-electronic converter. The optoelectronic conversion thus does not take place simultaneously in several optoelectronic converters due to the finite speed of light. Rather, simultaneous here means that photons that reach the detector surface simultaneously (ie, belong to the same wavefront), but have different energies (corresponding to different spectral detection ranges) are independently detectable in separate optoelectronic transducers.

The at least one detection element with a plurality of optoelectronic transducers arranged one behind the other can be referred to as a "sandwich" element. The photosensitive regions of the transducers are preferably arranged congruent and without offset. But they do not necessarily have to be congruent and can also be staggered. They can be arranged directly one above the other. Alternatively, at least one other layer (insulator or semiconductor) may be disposed between them. Additionally or alternatively, the transducers may be spaced apart by a gap, for example an air gap. In general, the mechanical arrangement and attachment of the optoelectronic transducers to one another is arbitrary, as long as they are both arranged one behind the other in the beam path of the relevant detection element. It is expedient, however, a minimum distance between the transducers.

The spectrometer according to the invention with a multi-layered construction of at least one detection element can be viewed in spectrally sequential arrangement as a wide-range spectrometer with two (or more) line or matrix detectors, which have different spectral detection areas due to mutually different types of optoelectronic transducers, which are illuminated via the same beam path. wherein the two detector rows or detector arrays at least partially overlap each other. The arrangement of these detectors in the same spectrometer in the same illumination beam path allows a high detection accuracy, since the light does not need to be divided into two different spectrometers and thus beam paths.

Preferably, the first, the diffraction grating facing opto-electronic transducer for detecting a shorter-wavelength spectral detection range and the second, remote from the diffraction grating optoelectronic transducer for detecting a longer wavelength spectral detection range, which spectrally overlaps the shorter wavelength detection range is formed, since the incident light so first on the first An optoelectronic transducer whose semiconductor layer (s) absorbs light in the shorter wavelength detection region outside the overlap region (partially) absorbs light in the overlap region partially and allows light in the longer wavelength detection region outside the overlap region to pass almost without absorption, so that it together with the unabsorbed portion of the Overlap region can be detected in the second optoelectronic transducer with high efficiency. As a result of this sequence of the optoelectronic transducers, the first optoelectronic transducer acts as a spectral filter for the shorter-wavelength detection region, with the exception of the overlap region, which allows a compact design. In the case of the detection area designated as shorter-wave, the upper limit wavelength is smaller than the upper limit wavelength of the detection area designated as longer-wavelength. The upper limit wavelength of the detection area designated as shorter-wave lies in the detection area designated as longer-wavelength - the two detection areas overlap one another. The lower limit of the shorter-wavelength detection range is thus smaller than the lower limit of the longer-wavelength detection range, which in turn is smaller than the upper limit of the shorter-wavelength detection range, which is smaller than the upper limit of the longer-wavelength detection range.

The spectral overlap of the shorter-wavelength detection range and the longer-wavelength detection range allows the compensation of temperature-dependent fluctuations of the electrical signals with high accuracy, if a (spectral) sensitivity of the optoelectronic transducer substantially temperature-independent or at least (significantly) less temperature-dependent than a corresponding (spectral) sensitivity of another opto-electronic transducer. From the electrical signals of the sandwich element can be determined with high accuracy, the internal temperature of the sandwich element, by means of which the compensation can be performed. In conjunction with the uniform beam path, this enables particularly high measuring accuracy.

Embodiments with more than two optoelectronic transducers per sandwich element are also possible. At least two of them must according to the invention have different spectral detection ranges from one another.

For example, in embodiments having multiple sandwich elements, the sandwich elements may represent a true subset of all detector elements. Alternatively, all the detector elements may be formed in multiple layers.

A combination of different semiconductor layers is known, for example, from InGaAs detectors with Si-based readout amplifiers. Here, the Si preamplifier serves as a carrier for InGaAs photodiodes. Both semiconductors are connected to each other by means of ball grids ("ball grids"), with illumination from the InGaAs side. According to the invention, the Si layer can be formed to detect light shorter than the wavelength detectable in the InGaAs. For this purpose, for example, the Si preamplifier of the InGaAs detector can be supplemented by a Si detector whose photosensitive surface lies just below the photosensitive surface of the InGaAs photodiodes. For this purpose, the silicon is etched for this purpose, for example, from the side facing away from the InGaAs, that is to say from the side facing the light, in order to avoid light losses and to tune the characteristic of the spectral sensitivity. For the purposes of the invention, the Si detector is the first optoelectronic transducer and the InGaAs detector is the second optoelectronic transducer.

In addition, an InGaAs detector matrix is known which is applied directly to a Si carrier provided with readout and amplification electronics ( Abhay M. Joshi et al .: "Monolithic InGaAs-on-silicon Short Wave Infrared Detector Arrays" in Imaging and Spectroscopy SPIE Vol. 2999, 211-224, 1997 ). Again, according to the invention, the Si layer can be formed for the detection of light (first optoelectronic transducer) which is shorter than the light detectable in the InGaAs (second optoelectronic transducer).

Preferably, several, in particular all, detection elements each have two different optoelectronic transducers for the simultaneous detection of two different spectral detection ranges. Thus, due to the filtering effect of the first optoelectronic transducer on light in the shorter-wavelength detection range, different wavelength ranges can be recorded with the same detection element.

Advantageously, a long-pass filter covers a real portion of the detector up to and including its long-wave end. This avoids that unwanted higher diffraction orders reach the detector and are detected there. The longpass filter can be applied directly to the detector. Alternatively, it can be arranged on a separate support, for example made of glass, which is expediently arranged directly on the detector. The separate carrier may be matched in its thickness so that the focal lines of the respective wavelength ranges are adapted to the different distances of the individual detectors from the diffraction grating. As a result, a greater accuracy of measurement can be achieved.

Embodiments in which an evaluation unit processes a first electrical signal of a detection element as a raw signal for the absorbed energy in a first wavelength range and a second electrical signal of the same detection element as a raw signal for the absorbed energy in a second wavelength range, the lower limit wavelength thereof, are particularly preferred k-times the lower limit wavelength of the first wavelength range and whose upper limit wavelength is k times the upper limit wavelength of the first wavelength range, where k is a quotient of two diffraction orders to be detected. For example, k = 2: 1, then the lower limit of the second wavelength range is twice the lower limit of the first wavelength range and the upper limit of the second wavelength range is twice the upper limit of the first wavelength range. Thus, the first and the second diffraction order of different wavelengths can be detected simultaneously with the same detection elements. The spectral width of the entire detector can thus be used twice, which doubles the spectral resolution of the spectrometer. As an alternative to the first and second diffraction order, for example, the second and the third diffraction order of different wavelengths can be detected simultaneously with the same detection elements (k = 3: 2). In a three- or multi-layer structure of the sandwich element, so three or more successively arranged optoelectronic transducers, three or more different diffraction orders corresponding to three or more wavelength ranges can be detected simultaneously with the same detection elements, the upper and lower limits of the second, third and optionally higher wavelength ranges in each detection element corresponding to many different multiples of the upper and lower limits of the first wavelength range.

Preferably, a first detection element, in whose direction the diffraction grating diffracts a diffraction order of a wavelength of the incident light, and a second detection element, in the direction of which the diffraction grating diffracts another diffraction order of the same wavelength of the incident light, both each have two optoelectronic transducers for the simultaneous detection of two different ones Spectral detection areas on. As a result, an internal temperature of the detector without separate temperature sensors can also be determined in arrangements in which two different diffraction orders are diffracted to the same detection elements.

In embodiments in which only a true subset of the detection elements is designed in a sandwich construction or only one of a plurality of optoelectronic transducers is used for detection, advantageously one of the detection elements which do not have two optoelectronic transducers for the simultaneous detection of two different spectral detection areas first true subset of an optoelectronic transducer for detecting the first spectral detection range and a second real subset of an optoelectronic transducer for detecting the second spectral detection range, wherein these two subsets are disjoint. In the intermediate detection region, one or two of the sandwich elements are then preferably arranged, in particular for enabling a temperature fluctuation compensation. As a result, only a part of the detector needs to be equipped with a temperature-insensitive but more expensive opto-electronic converter.

In this case, a spectral long-pass filter is preferably arranged in front of a true subset of those detection elements which have an optoelectronic transducer for the shorter-wavelength spectral detection range. This avoids that unwanted higher diffraction orders reach the relevant detection elements and are detected there. The long-pass filter for the shorter wavelength range is required if the ratio of the longest wavelength to the shortest wavelength to be detected is greater than 2: 1, otherwise for the wavelength range from twice the shortest wavelength to be detected no clear wavelength allocation of the detected light longer possible would. Without a long-pass filter, light of the first and second orders of diffraction (half wavelength) would strike the same detector element.

Expediently, the first optoelectronic transducer is (essentially) a semiconductor layer of silicon and the second optoelectronic transducer (essentially) a semiconductor layer of at least one of the materials indium gallium arsenide, germanium and lead sulfide.

Advantageously, the first optoelectronic transducer may be a semiconductor layer etched from a side facing the diffraction grating. This allows a compact design with little effort.

Embodiments in which an evaluation unit determines a value of a temperature of the relevant detection element based on at least one electrical signal of the first optoelectronic transducer and at least one electrical signal of the second optoelectronic transducer are preferred. This eliminates the need for separate temperature sensors. The temperature value according to the invention can be determined, for example, in the unit ° C or K, but alternatively it can also depend on the temperature according to any one-to-one function.

Embodiments in which an evaluation unit determines a value of a temperature of the detector based on four electrical signals of two multilayer detection elements (with two optoelectronic transducers) are particularly preferred, the two detection elements corresponding to two different wavelength ranges or two different diffraction orders of the same wavelength range. As a result, an internal temperature of the detector without separate temperature sensors can also be determined in arrangements in which two different diffraction orders are diffracted to the same detection elements.

für M Beugungsordnungen, M optoelektronische Wandler (i = A, B, ...) und M Detektionselemente (p = 1, ... M).Expediently, the evaluation unit determines the value of the temperature of the detector by solving the equation system

for M diffraction orders, M optoelectronic transducers (i = A, B, ...) and M detection elements (p = 1, ... M).

Advantageously, the evaluation unit can use the determined value of the temperature to normalize an electrical signal of another detection element, in particular of a detection element with only one (used) optoelectronic transducer for detecting the shorter-wavelength spectral detection range, according to a temperature-dependent spectral sensitivity. As a result of this compensation of the temperature-dependent fluctuations in the spectral sensitivity of the detection elements, as already described above, the measurement accuracy is improved.

Embodiments in which a semiconductor layer of an optoelectronic transducer has an electronic preamplifier for a semiconductor layer of the other optoelectronic transducer are particularly compact.

Zeckmäßigerweise a long-pass filter is arranged in the incident light, the wavelengths below the shortest wavelength spectral detection range blocks. This avoids that unwanted higher orders of diffraction and undesired short-wave light get into the detector and there falsify the measurement of the desired wavelengths, the invention will be explained in more detail with reference to embodiments.

In the drawings show:

1 a wide-area spectrometer with a single sandwich element and

2 a wide-range spectrometer in which all detection elements are designed in sandwich construction.

In all drawings, like parts bear like reference numerals.

1 represents a multichannel optical spectrometer 10 with a spectral detection range of λ _min = 310 nm (lower limit wavelength) to λ _max = 1680 nm (upper limit wavelength), wherein only the first diffraction order (m = 1) of the incident light L is detected. The spectrometer 10 includes for this purpose an entrance slit 1 , an imaging diffraction grating 2 , a detector 3 with a carrier 4 - For example, a substrate of alumina ceramic (Al ₂ O ₃ ) -, a control and evaluation 5 and for example two temperature sensors 6 in contact with the detector 3 stand and can be omitted in alternative embodiments. The concrete structure of the beam path is known to the person skilled in the art. In front of the entrance slit 1 is an optical long-pass filter 7 arranged. In front of a partial area of the detector 3 is an optical long-pass filter 8th arranged. The spectrometer is enclosed 10 from a housing 9 , Not shown are known connections to the power supply and an external interface to the control and evaluation 5 , The interface can be used, for example, for transmitting the measured values and / or for controlling and / or programming the control and evaluation unit 5 serve.

The detector 3 For the sake of clarity of the drawing, for example, only eighteen equal width, separate detection elements 3.1 ... 3.18 on, which can be referred to as pixels. The detection elements 3.1 ... 3.9 are pure silicon detectors with a respective Si semiconductor layer system as a single optical converter 3.1.A ... 3.9.a for optoelectronic conversion of diffracted light S in the wavelength range of 310 nm to 950 nm. Each of the optoelectronic transducers 3.1.A ... 3.9.a comprises in a known manner a p-doped Si layer and an n-doped Si layer and thus has its own pn junction. The detection elements 3.11 ... 3.18 on the other hand, they are pure indium gallium arsenide detectors with a respective InGaAs semiconductor layer system as a single optoelectronic transducer 3.11.B ... 3.18.B for optoelectronic conversion in the wavelength range from 1100 nm to 1680 nm and intermediate layers 3.11.A ... 3.18.A , for example made of silicon. The intermediate layers 3.11.A ... 3.18.A may be formed together from a continuous substrate or separately. Each of the optoelectronic transducers 3.11.B ... 3.18.B consists in a known manner of a p-doped InGaAs layer and an n-doped InGaAs layer and thus has its own pn junction.

The detection element 3.10 , to which, for example, the wavelength range of 950 nm to 1100 nm is diffracted, is a sandwich element with two different optoelectronic transducers 3.10.A and 3.10.B educated. The first optoelectronic converter 3.10.A is a silicon layer system with a pn junction as in any Si converter 3.1.A ... 3.9.a , the second optoelectronic transducer 3.10.B is an InGaAs layer system with a pn junction as in any of the InGaAs converters 3.11.B ... 3.18.B , The two optoelectronic converters 3.10.A and 3.10.B represent two successively arranged photodiodes that form simultaneously disjoint space charge zones, so that in each of these transducers can take place simultaneously independent of the other transducer optoelectronic conversion. The detection elements 3.1 ... 3.10 with respective Si converter 3.1.A ... 3.10.A may be considered a first detector row A and the detection elements 3.10 ... 3.18 with respective InGaAs converter 3.10.B ... 3.18.B be regarded as a second detector line B, which overlap each other geometrically and spectrally in the region of the sandwich element. The detection in the overlapping wavelength range (950 nm to 1100 nm) is carried out both with the InGaAs detector A and with the Si detector B. Although the latter has a lower noise, but in turn has a higher temperature dependence than the InGaAs detector A. ,

The carrier 4 is only indicated in the figure and points, for example, in front of the photosensitive areas of the detection elements 3.P Recesses (not shown) or transparent sections (not shown) on. For clarity, in the figure are the substrates of the detection elements 3.P - In the case shown Si substrates on which the Si layers 3.pA are arranged - not shown separately.

The longpass filter 7 blocks light L of a wavelength of, for example, up to 300 nm and allows light L of a wavelength from, for example, 310 nm almost completely to the entrance slit 1 happen. The longpass filter 8th lets in the grid 2 diffracted light S below a wavelength of, for example, 550 nm maximum, for example, 1% transmission to the detector 3 to and points above. for example, 590 nm at least, for example, 90% transmittance. The non-detection Si interlayers 3.11.A ... 3.18.A (Alternatively, a continuous cover substrate) in front of the layers of the optoelectronic transducer 3.11.B ... 3.18.B serve as filters for blocking higher diffraction orders (m ≥ 2).

An overview of the fate of the different wavelengths λ of the incident light L is given in the following table: λ fate ≤ 300 nm First through long pass filter 7 away. 310 to 590 nm Absorption in Si detector A without prior filtering; Diffraction orders m ≥ 2 in advance by long-pass filter 7 away. 590 to 600 nm Absorption in Si detector A with or without long pass filter 8th (Position of the filter edge); Diffraction orders m ≥ 2 in advance by long-pass filter 7 away. 600 to 950 nm Absorption in Si detector A with long-pass filter 8th ; Diffraction orders m ≥ 2 in advance by long-pass filter 8th away. 950 to 1100 nm Absorption in Si detector A and in InGaAs detector B with long-pass filter 8th ; Diffraction orders m ≥ 2 in advance by long-pass filter 8th away. 1100 to 1680 nm Absorption in the InGaAs detector B; Diffraction orders m ≥ 2 in advance by Si intermediate layers 3.11.A ... 3.11b sufficient thickness removed.

The electrical signals of the detection elements 3.P (p = 1 ... 18), that of the control and evaluation unit 5 be supplied to the energy W upon detection of light, are U _{i, p} = D _{i, p} (T) x W (λ _p ), in the present example, for p = 1 ... 9, i = A; for p = 10, i = A or i = B, and for p = 11 ... 18, i = B. The detector 3 So there are 19 electrical signals U _{i, p} from.

In this case, D _{i, p} (T) is the spectral sensitivity of the optoelectronic transducers 3.pi λ in the diffracted on them wavelength ranges _p depending on the temperature of the optoelectronic converter concerned 3.pi , It must be before using the spectrometer 10 be determined at a plurality of (at least two) temperatures T _k in the intended operating temperature range with monochromatic light of known power in a so-called calibration passage. The sensitivity at any Intermediate temperatures can be calculated, for example, by linear interpolation in a known manner. Alternatively, a parameterized model function can be adapted to the measured temperature values T _k by means of a mathematical compensation calculation in a known manner, for example by determining the smallest deviation squares.

For the two optoelectronic converters 3.10.A and 3.10.B of the sandwich element 3.10 the irradiated light energy W (λ ₁₀ ) is identical, so that for the ratio of the signals U _{i, p} at a current temperature T _{D of} the two optoelectronic converters:

From this ratio of the current signal values U _{A, 10} / U _{B, 10} , an actual temperature value T _D for the detector element can be determined on the basis of the spectral sensitivity functions D _{i, 10} (T) 3.10 be determined. For this purpose, for example _, the quotient function q ₁₀ (T) can be formed from the spectral sensitivity functions D _{i, 10} (T):

By means of the inverse function q ₁₀ ^-1 to be determined from the quotient function q ₁₀ (T), the current temperature value T _D can then be calculated:

Alternatively, reversal functions D _{i, p} ^-1 can be determined from the spectral sensitivity functions D _{i, p} (T) and the current temperature value T _D can be determined on the basis of the ratio of the signal values U _{A, 10} and U _{B, 10} .

On the basis of the current temperature value T _D and the previously determined spectral sensitivity functions D _{i, p} (T), temperature-dependent fluctuations of the electrical signals U _{i, p of} all the detection elements 3.pi be compensated. To determine the actual momentary light power in the wavelength range λ ≤ 1100 nm are from the control and evaluation 5 because of the lower noise, for example, only the signals U _{A, p of} the Si converter 3.1.A ... 3.10.A used and standardized according to the respective spectral sensitivity functions D _{A, p} (T) temperature-dependent and output via an interface:

The temperature determination on the ratio of the electrical signals U _{i, p} in the overlapping wavelength range has compared to a temperature measurement with a conventional, on the outside of the detector 3 applied separate temperature sensor 6.1 the advantage that does not affect the surface temperature of the wearer 4 but rather the two optoelectronic transducers 3.10.A and 3.10.B averaged temperature T of the actual detection element 3.10 is determined and thus influences by temperature gradients (non-uniform heating, for example, due to heat conduction) are minimized. The temperature influence on the spectral sensitivity of the InGaAs detector at the long-wave end λ _max can additionally be determined either with an external temperature sensor 6.2 as close as possible to the detecting semiconductor layer or by the current detected detector temperature T _D (which, however, exactly only in the middle of the detector 3 prevails) are compensated. Which single compensation option or a combination of both works best depends on the thermal conditions in the spectrometer 10 especially where the lowest temperature gradients exist. The person skilled in the art is able to decide, with regard to the thermal conditions, which type of compensation causes the most accurate measurement in each case.

In real embodiments (not shown), the detector has 3 for example, a total of 256 (p = 1 ... 256) detection elements. Other numbers are possible. The above considerations apply accordingly. In the overlapping wavelength range of the detectors A and B then there are several detection elements (pixels), of which at least one as described above is a sandwich element. Alternatively, several detection elements can be used 3.P be designed as sandwich elements, in particular in the region of overlapping detection areas of the different detector types.

Generally applies to the ratio of the electrical signals U _{A, P} and U _{B, p of} the optoelectronic transducer 3.pA and 3.pB a sandwich detection element 3.P :

Indicates the detector 3 a plurality of sandwich elements, a separate temperature value T _D can be determined for several of them, in particular for each of them. In order to reduce the influence of noise of the InGaAs converter on the temperature value T _D determined from the different optoelectronic converters, a combined temperature value T _{D can be determined} from the signals of several sandwich elements in the overlapping spectral range. Thus, a smoothing of the determined temperature can be carried out, for example by moving averaging with a predetermined time constant. This can be done, for example, in the control and evaluation unit 7 happen.

2 shows a multi-channel optical spectrometer 10 with a spectral detection range of λ _min = 400 nm to λ _max = 1680 nm, which detects only the first diffraction order (m = 1) and the second diffraction order (m = 2) of the incident light L. The construction of the spectrometer 10 is essentially the same as in 1 shown device, however, is the entire photosensitive surface of the detector 3 executed in sandwich structure. Again, the detector points 3 purely for the sake of clarity only eighteen detection elements 3.1 ... 3.18 on. All eighteen detection elements 3.P (p = 1 ... 18) each have two optoelectronic transducers 3.pi (i = A, B). These are, for example, the first optoelectronic transducers 3.pA in each case around an Si layer with a first pn junction and in the second optoelectronic transducers 3.pA to an indium-gallium arsenide layer with a second pn junction, whose electrical signals in a known manner the control and evaluation 5 be supplied.

Exemplary are the first optoelectronic transducers 3.pA all in a first level and the second optoelectronic transducers 3.pB all arranged in a second level. The second optoelectronic transducers 3.pB are further from the diffraction grating 2 removed as the first optoelectronic transducers 3.pA and on the diffraction grating 2 opposite side of the first opto-electronic converter 3.pA arranged. The entirety of the first optoelectronic transducers 3.pA the detection elements 3.P can be used as the first line detector A (here Si) and the entirety of the second optoelectronic converter 3.pB be considered as a second line detector B (here InGaAs). Detector B is located along the direction of incidence of the diffracted light S behind detector A.

Over a partial area of the detector 3 from a wavelength of for example m · λ = (1165 ± 5) nm, there is a long-pass filter 8th which allows at least for example 1% of diffracted light S up to a wavelength of, for example, λ = 560 nm and at least for example 90% at a wavelength of, for example, λ = 580 nm. The longpass filter 8th is applied directly on said subarea of the detector. In alternative embodiments (not shown), it may be arranged on a separate support, for example made of glass. The thickness of the support is then suitably adjusted so that the focal line of the second diffraction order (longer wavelengths) to the rear in the direction of the InGaAs converter 3.pB are shifted and thereby at least partially with respect to the diffraction grating 2 compensate for different detector positions. The focal line representing the line of the best focus of the diffraction grating 2 is generally not a straight line. The position and orientation of the planar detector 3 Therefore, it is expediently adapted to the focal line at the smallest distance (smallest distance in the subregions with the highest requirement for the spectral resolution). In front of the entrance slit 1 is a longpass filter 7 arranged, the wavelengths to, for example, λ = 390 nm substantially blocks and Wavelengths from, for example, λ = 400 nm almost completely pass. Wavelengths with λ ≤ 390 nm therefore need not be considered below.

Short-wave light S of the second order of diffraction (m = 2) with wavelengths between λ = 400 nm and λ = 840 nm, ie m · λ = 800 nm to m · λ = 1680 nm, is absorbed predominantly in the first line detector A, which from this in a known manner electrical signals U _{A, P} generated, and thus kept away from the second line detector B. Long-wave light of the first diffraction order (m = 1) with wavelengths between λ = 800 nm and λ = 1680 nm is not or only slightly absorbed by the first line detector A and thus almost completely transmitted to the second line detector B, the resulting known Way electrical signals U _{B, p} generated.

• 1. Herkömmliche polychromatische Messung von 400 nm bis 840 nm mit Si-Detektor und Langpassfilter.
• 2. Herkömmliche polychromatische Messung von 800 nm bis 1680 nm mit InGaAs-Detektor.
• 3. Erfindungsgemäße polychromatische Weitbereichsmessung von 400 nm bis 1680 nm.

With the basic optical structure according to the in 2 sketched embodiment, three different modes of operation can be realized:

• 1. Conventional polychromatic measurement from 400 nm to 840 nm with Si detector and long pass filter.
• 2. Conventional polychromatic measurement from 800 nm to 1680 nm with InGaAs detector.
• 3. Polychromatic long-range measurement according to the invention from 400 nm to 1680 nm.

The higher diffraction orders (m ≥ 3) are in the spectrometer 10 through the longpass filter 7 and 8th suppressed: diffraction order M = 1 m = 2 m = 3 Detection (absorption) Mainly in InGaAs (line detector B) predominantly in Si (line detector A) none without filter 800 ... 1160 nm 400 ... 580 nm to 390 nm because of Filter edge, filter 8th present or not 1160 ... 1170 nm 580 ... 585 nm Long-pass filter 7 Long-pass filter 8th Blocking up to 560 nm, passage from 580 nm 1170 ... 1680 nm 585 ... 840 nm 390 ... 560 nm due to long-pass filter 8th

The first diffraction order of the spectral band from 800 nm to 1680 nm thus becomes simultaneous with the second diffraction order of the spectral band from 400 nm to 840 nm onto the detector 3 directed. The evaluation unit 5 processed, for example, the electric signal U _{A, 1} of the optoelectronic converter 3.1.A of the detection element 3.1 as a raw signal for the absorbed energy in the wavelength range of 400 nm to 424.4 nm and the electrical signal U _{B, 1 of} the optoelectronic transducer 3.1.B the same detection element 3.1 as a raw signal for the absorbed energy in the wavelength range 800 nm to 848.8 nm. For the other detection elements corresponding, so far shorter wavelengths does not apply through the long-pass filter 8th be suppressed. Due to such dual use of the detection elements, the spectral resolution is approximately twice as large as that in 1 illustrated embodiment.

The in the diffraction orders m _{1 2} = 1 and m = 2 at an over the detector 3 uniform temperature T _D absorbed light energy W (λ _p / m _j ) can be determined on the basis of the recorded detector signals U _{i, p} (i = A, B) from the following system of equations:

D _{i, j, p} (T) is the spectral sensitivity of the optoelectronic transducers 3.pi at their associated wavelength λ _p / m _j . depending on the temperature of the relevant optoelectronic transducer 3.pi , It must be before using the spectrometer 10 be determined at a plurality of (at least two) temperatures T _k in the intended operating temperature range with monochromatic light of known power in a so-called calibration cycle:

The spectral sensitivity at any intervening temperatures can be calculated, for example, by linear interpolation in a known manner. Alternatively, a parameterized model function can be adapted to the measured temperature values T _k by means of a mathematical compensation calculation in a known manner, for example by determining the smallest deviation squares.

The temperature dependence of the detection elements 3.pi measured signals U _{i, p} , as in the embodiment according to 1 by normalization with the spectral sensitivity of D _{i, j, p} (T _{D, p)} of the detection elements 3.pi based on their current temperature T _{D, p are} compensated. Specifically, this succeeds in two ways:
If, as in 2 the case, at least a first separate temperature sensor 6.1 , preferably a second separate temperature sensor 6.2 , at the detector 3 the one or more temperatures T ₁ (and optionally T ₂ ) measured therewith may be used as the current detector temperature T _{D, p} to determine the temperature dependence of the spectral sensitivity D _{i, j, p} (T) of the optoelectronic transducers 3.pi to compensate. If two separate temperature sensors 6.1 and 6.2 at the ends of the detector 3 are arranged, the temperature T _{D, p of} the respective detection element 3.P for example, by its distance to the temperature sensors 6 be calculated by interpolation between the measured temperatures T ₁ and T ₂ .

Even without separate temperature sensors 6 can - assuming or the actual requirement that along the detector 3 no temperature gradient, but one for all optoelectronic converters 3.pi same temperature T _D is present - this temperature T _D, for example, four detector signals U _{i, p are determined} at two different wavelengths λ _a and λ _b . If, for example, λ _b = k · λ _{a is} selected, where k = m ₂ : m _{1 is} the quotient of the two diffraction orders to be detected, here, for example, m ₁ = 1, m ₂ = 2 and thus k = 2: 1 = 2, For this purpose, the following equation system with the four unknown W (λ _a / k), W (λ _a ), W (k * λ _a ) and T _D can be solved:

For this purpose, the system of equations can be simplified at first. The determination of T _D can then take place, for example, by means of the inverse functions D _{i, j, p} ^-1 (T). Alternatively, for example, look-up tables (LUT) may be used to determine T _D.

To achieve a uniform temperature distribution across all optoelectronic converters 3.pi To a large extent, the detector can ensure 3 advantageously be thermally isolated from the environment.

From the inventively determined average temperature T _{D of} the detector 3 and the measured values T ₁ , T _{2 of} the external temperature sensors 6.1 . 6.2 may occur in the presence of a temperature gradient along the detector 3 the temperature T _{D, p of} each individual detector element are determined and used to correct its spectral sensitivities D _{i, j, p} (T).

In real embodiments (not shown), the detector has 3 For example, a total of 256 detection elements. Other numbers are possible as well as other spectral detection ranges. The above considerations apply accordingly.

Provided the detection elements 3.P three or more optoelectronic transducers 3.pi having pairs of different spectral detection ranges and output a corresponding number of signals U _{i, p} (i = A, B, C, ...), the above equation system can be extended to a corresponding number M ≥ 3 of simultaneously measurable diffraction orders. In general, the equation system can be formulated as follows:

For temperature determination, in the case of M = 3, three different wavelengths must be used on three different detection elements.

In 3 is the result of the diffraction of wavelengths λ of the incident light L at the grating 2 resulting beam direction on the line detectors A and B of a detector 3 with 256 detection elements 3.P each with two optoelectronic transducers 3.pi shown graphically. The effect of the long-pass filter 8th is not taken into account.

It is possible in all embodiments, the control and evaluation 5 outside the spectrometer 10 to arrange, for example, in another architectural space.

In all embodiments of the invention, the calculations for determining the temperature value T _{D can be made} immediately after the measurement of the electrical signals U _{i, p} or with a time interval thereof. In both cases, they can be used in the internal control and evaluation unit 5 or at a distance from the spectrometer 10 in an external evaluation unit (not shown). For this purpose, the raw (uncompensated) signal values U _{i, p} can be stored and / or output via an interface.

In all embodiments of the invention, the compensation of temperature fluctuations can take place immediately after the measurement of the electrical signals U _{i, p} or in temporal distance thereof. In both cases, they can be used in the internal control and evaluation unit 5 or at a distance from the spectrometer 10 in an external evaluation unit (not shown). For this purpose, the raw (uncompensated) signal values U _{i, p} and / or already determined temperature values T _D can be stored and / or output via an interface. As a result, the amount of data to be stored and / or transmitted can be minimized.

In all embodiments, the detector 3 a two-dimensional distribution of detection elements 3.pxy have, preferably in the form of perpendicular to each other arranged rows and columns. In such embodiments, a single detection element 3.pxy be designed as a sandwich element, while all other detection elements have only one spectral detection range. Alternatively, a true subset of the detection elements 3.pxy be designed as a sandwich element, while all other detection elements have only one spectral detection range. Alternatively, all detection elements 3.pxy be designed as a sandwich element. For example, a detector 3 256 × 256 detection elements 3.pxy comprising all two or more successively arranged optoelectronic transducers.

LIST OF REFERENCE NUMBERS

1

entrance slit

2

diffraction grating

3

detector

3.P

Detection element (p = 1 ... 18)

3.pi

Optoelectronic converter (i = A, B)

4

carrier

5

Control and evaluation unit

6

temperature sensor

7

Long-pass filter

8th

Long-pass filter

9

casing

10

spectrometer

L

Incident light

S

Bent light

T _1,2

temperature signals

U _{i, p}

Photoelectric signals

λ _min

Lower limit wavelength

λ _max

Upper limit wavelength

A

Slice detector

B

Slice detector

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10010213 A1 [0003]

Cited non-patent literature

• Abhay M. Joshi et al .: "Monolithic InGaAs-on-silicon Short Wave Infrared Detector Arrays" in Imaging and Spectroscopy SPIE Vol. 2999, 211-224, 1997 [0020]

Claims (15)

Optical spectrometer ( 10 ) with a housing ( 9 ), which has an entrance slit ( 1 ), a diffraction grating ( 2 ) and a spatially resolving detector ( 3 ) with a plurality of optoelectronic detection elements ( 3.P ), wherein the diffraction grating light (L), that through the entrance slit ( 1 ) in the housing ( 9 ), depending on the wavelength in the direction of different detection elements ( 3.P ), characterized in that at least one of the detection elements ( 3.10 ) two optoelectronic transducers ( 3.10.A . 3.10.B ), which - for the simultaneous detection of two different spectral detection areas - have a different composition, - separate electrical signals (U _{A, 10} , U _{B, 10} ) and - along an incident direction of the diffracted light (S) on the detector ( 3 ) are arranged one behind the other. Spectrometer ( 10 ) according to claim 1, wherein several, in particular all, detection elements ( 3.P ) two different optoelectronic transducers ( 3.pA . 3.pB ) for the simultaneous detection of two different spectral detection areas. Spectrometer ( 10 ) according to the preceding claim, wherein a long-pass filter ( 8th ) a real portion of the detector ( 3 ) up to and including its long-wave end. Spectrometer ( 10 ) according to claim 2 or 3, wherein an evaluation unit ( 5 ) a first electrical signal of a detection element ( 3.1 ) is processed as a raw signal for the absorbed energy in a first wavelength range and a second electrical signal of the same detection element ( 3.1 ) as a raw signal for the absorbed energy in a second wavelength range whose lower limit wavelength is k times the lower limit wavelength of the first wavelength range and whose upper cut-off wavelength is k times the upper cut-off wavelength of the first wavelength range, where k is a quotient of two is to be detected diffraction orders. Spectrometer ( 10 ) according to one of claims 2 to 4, wherein a first detection element ( 3.P ), in the direction of which the diffraction grating ( 2 ) diffracts a diffraction order of a wavelength of the incident light (L), and a second detection element ( 3.P ' ), in the direction of which the diffraction grating ( 2 ) diffracts another diffraction order of the same wavelength of the incident light (L), both two optoelectronic transducers ( 3.P ( '). A . 3.P ( '). B ) for the simultaneous detection of two different spectral detection areas. Spectrometer ( 10 ) according to one of the preceding claims, wherein of the detection elements ( 3.P ), which are not two opto-electronic converters ( 3.pA . 3.pB ) for simultaneously detecting two different spectral detection ranges, a first true subset comprising an optoelectronic transducer for detecting the first spectral detection range and a second true subset comprising an optoelectronic transducer for detecting the second spectral detection range, the two subsets being disjoint. Spectrometer ( 10 ) according to the preceding claim, wherein in front of a true subset of those detection elements comprising an optoelectronic transducer ( 3.pA ) for the shorter wavelength spectral detection range, a spectral long-pass filter ( 8th ) is arranged. Spectrometer ( 10 ) according to one of the preceding claims, wherein a sensitivity of one of the optoelectronic transducers ( 3.10.A ) is substantially temperature-independent or at least less temperature-dependent than a corresponding sensitivity of the other optoelectronic transducer ( 3.10.B ) and / or wherein the first optoelectronic transducer ( 3.pA ) (essentially) a silicon semiconductor layer and the second optoelectronic converter ( 3.pB ) is (essentially) a semiconductor layer of at least one of the materials indium gallium arsenide, germanium and lead sulfide. Spectrometer ( 10 ) according to one of the preceding claims, wherein the first optoelectronic transducer ( 3.pA ) is a semiconductor layer, which differs from a diffraction grating ( 2 ) side is etched. Spectrometer ( 10 ) according to one of the preceding claims, wherein an evaluation unit ( 5 ) based on at least one electrical signal (U _{A, P} ) of the first optoelectronic transducer ( 3.pA ) and at least one electrical signal (U _{B, P} ) of the second optoelectronic transducer ( 3.pB ) a value (T _D ) of a temperature of the respective detection element ( 3.10 ). Spectrometer ( 10 ) according to one of the preceding claims, wherein an evaluation unit ( 5 ) on the basis of four electrical signals (U _{i, p} ) of two multilayer detection elements, a value (T _D ) of a temperature of the detector ( 3 ), wherein the two detection elements correspond to two different wavelength ranges or two different diffraction orders of the same wavelength range. Spectrometer ( 10 ) according to one of the preceding claims, in particular according to the preceding claim, wherein the evaluation unit ( 5 ) the value (T _D ) of the temperature by solving the equation system

for M diffraction orders, M optoelectronic transducer (i = A, B, ...) and M detection elements (p = 1, ... M) determined. Spectrometer ( 10 ) according to one of claims 10 to 12, wherein the evaluation unit based on the determined value (T _D ) of the temperature, an electrical signal of another detection element, in particular a detection element with only one optoelectronic transducer ( 3.pA ) for the detection of the shorter-wavelength spectral detection range, normalized according to a temperature-dependent spectral sensitivity. Spectrometer ( 10 ) according to one of the preceding claims, wherein a semiconductor layer of an optoelectronic transducer ( 3.10.A ) an electronic preamplifier for a semiconductor layer of the other optoelectronic transducer ( 3.10.B ) having. Spectrometer ( 10 ) according to one of the preceding claims, wherein in the incident light (L) a long-pass filter ( 7 ), which blocks wavelengths below the shortest wavelength spectral detection range.

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