Photoconductor readout circuit

Abstract

The device (111) is proposed. The device (111) comprises: - electrical resistance R depending on the illumination (116) of the photosensitive area (118) of the photoconductor (114) photo at least one photoconductor (114) configured to indicate; at least one photoconductor readout circuit (112), said photoconductor readout circuit (114) being adapted to measure the electrical resistance R of said photoconductor (114); photo at least one photoconductor readout circuit (112) configured to determine a photoconductor readout frequency (Vp) of the photoconductor (114), the photoconductor readout circuit (112) comprising at least one bias voltage source (152) configured to apply at least one modulated bias voltage to the photoconductor (114); Equipped with.

Description

Technical Field

[0001] The present invention relates to a photoconductor readout circuit, a detector, and the use of a photoconductor readout circuit for reading out a photoconductor. Specifically, the photoconductor readout circuit can be used to determine the measurable voltage response of a photoconductor such as a lead sulfide photoconductor sensor.

Background Art

[0002] Photoconductors such as lead sulfide photoconductors require resistance value measurement for reading out. This may require a strong bias voltage and a circuit adapted to this voltage. The measurement is usually performed by comparison with other resistances. Usually, the resistance or the photoconductor is measured in a circuit such as a Wheatstone bridge. For example, a voltage divider circuit is known for reading out a photoconductor. Usually, a voltage amplifier is used together with a voltage divider to measure the signal from the photoconductor (see, for example, https: / / www.hamamatsu.com / resources / pdf / ssd / e06_handbook_compound_semiconductor.pdf).

[0003] However, in this known readout circuit, the resistance may drift as a response to an unmodulated bias voltage, probably due to an electrochemical process. In combination with a broadband infrared light source, the modulation of the light source becomes a problem, and usually at a low speed, the measurement time becomes long, resulting in high f-noise. There is a need for a cheaper and more reliable readout circuit that can adjust the measurement frequency regardless of the light modulation frequency.

[0004] CN208077480 describes an LED scintillation frequency control ware for 555 integrated circuit education belonging to the field of digital electronic technology. The oscillation circuit that constitutes the 555 integrated circuit is the focus and difficulty during the education of the digital electronic technology course. The utility model discloses a square wave oscillation circuit for the design of the 555 integrated circuit, and its "frequency" is controlled by the environmental irradiation intensity, and the function of controlling the LED flashing frequency by the light irradiation intensity is realized. The 555 integrated circuit for the digital electronic technology course experiment applied in this utility model gives knowledge to students, transfers the interest that students participated in the experimental education, and improves the education effect. Regarding the "555 timer IC", it is described at "555 timer IC - Wikipedia", en.wikipedia.org / w / index.php?title=555_timer_IC&oldid=919149415.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, the problem addressed by the present invention is to identify a photoconductor readout circuit and detector that at least substantially avoid the drawbacks of this kind of known circuit. In particular, an improved, particularly more reliable and cost-effective readout of the photoconductor would be desirable.

Means for Solving the Problems

[0006] This problem is solved by the present invention with the features of the independent patent claims. Advantageous developments of the present invention that can be realized individually or in combination are shown in the dependent claims and / or the following description and detailed embodiments.

[0007] As used herein, the terms "having", "comprising", and "including", and grammatical variations thereof, are used in a non-exclusive manner. Thus, the expression "A has B", as well as the expressions "A comprises B", or "A includes B", can refer to both the fact that, in addition to B, A includes one or more further components and / or elements, and the case where, in addition to B, no other components and / or elements are present in A.

[0008] In a first aspect of the present invention, an apparatus is disclosed. The apparatus is: - at least one photoconductor configured to exhibit an electrical resistance R that depends on the irradiation of a photosensitive region of the photoconductor; photo and at least one bias voltage source configured to apply at least one modulation bias voltage to the photoconductor, the photoconductor readout circuit being configured to determine the electrical resistance R of the photoconductor; - at least one photoconductor readout circuit, the photoconductor readout circuit comprising at least one bias voltage source configured to apply at least one modulation bias voltage to the photoconductor, the photoconductor readout circuit being configured to determine the electrical resistance R of the photoconductor; photo and comprising. comprising.

[0009] As used herein, the term "photoconductor", also referred to as a photoresistor, is a broad term and should be given the meaning that is ordinary and customary to those skilled in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to a photosensitive element capable of exhibiting a specific electrical resistance R that depends on the irradiation of a photosensitive region of the photoconductor. Specifically, the electrical resistance depends on the irradiation of the material of the photoconductor. As will be outlined in detail below, the photoconductor may include a photosensitive region containing a "photoconductive material". The photoconductor can be applied, for example, to a photosensitive detector circuit. photo Specifically, the electrical resistance depends on the irradiation of the material of the photoconductor. As will be outlined in detail below, the photoconductor may include a photosensitive region containing a "photoconductive material". The photoconductor can be applied, for example, to a photosensitive detector circuit.

[0010] As used herein, the term "irradiation" is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to electromagnetic radiation in one or more of the visible spectrum range, ultraviolet spectrum range, and infrared spectrum range. Therein, in accordance with ISO-21348 in part, the term "visible spectrum range" generally refers to the spectral range of 380 nm to 760 nm. The term "infrared (IR) spectrum range" generally refers to electromagnetic radiation in the range of 760 nm to 1000 μm, of which the range of 760 nm to 1.4 μm is generally called the near-infrared (NIR) spectrum range, and the range of 15 μm to 1000 μm is called the far-infrared (FIR) spectrum range. The term "ultraviolet spectrum range" generally refers to electromagnetic radiation in the range of 1 nm to 380 nm, preferably 100 nm to 380 nm. Hereinafter, the term "irradiation" is also expressed as "light". Preferably, the irradiation used within the present invention is visible light, i.e., light in the visible spectrum range, and / or infrared light, i.e., light in the infrared spectrum range.

[0011] As used herein, the term "photosensitive region of a photoconductor" generally refers to an area of a photoconductor that is sensitive to irradiation by, for example, an incident light beam. For example, the photosensitive region may preferably (but not necessarily) be continuous and may be a two-dimensional or three-dimensional region that can form a continuous region. A photoconductor can have one such photosensitive region or, alternatively, multiple such photosensitive regions. As used herein, "electrical resistance R depending on irradiation" photoThe term "is shown" generally refers to the electrical resistance of a photoconductor being adjusted and / or changed and / or varied depending on the irradiation of the photosensitive region, particularly the intensity of the irradiation. In particular, in response to irradiation, the electrical resistance is adjusted and / or changed and / or varied. When the photoconductor is irradiated, the photoconductor may exhibit a decrease in electrical resistance. The photoconductor may, when irradiated, have its electrical resistance decreased. Specifically, the electrical resistance of the photoconductor may decrease with an increase in the intensity of the incident light. The change between the dark resistance and the bright resistance is the measured or read amount. The term "dark resistance" as used herein generally refers to the electrical resistance of the photoconductor in a non-lighted state, i.e., a state without irradiation. The term "bright resistance" as further used herein refers to the electrical resistance of the photoconductor under irradiation. For measurement and / or reading, generally, a voltage divider circuit having non-linear behavior is known. The linear change in the resistance of the photoconductor results in a non-linear change in the voltage output. The present invention proposes a circuit function having linear behavior, as outlined in more detail below.

[0012] The photoconductor may comprise at least one photoconductive material. Since electrical resistance is defined as the reciprocal of electrical conductivity, the term "photoresistive material" may also be used to refer to the same kind of material. The photosensitive region may include at least one photoconductive material selected from the group consisting of lead sulfide (PbS); lead selenide (PbSe); mercury cadmium telluride (HgCdTe); cadmium sulfide (CdS); cadmium selenide (CdSe); indium antimonide (InSb); indium arsenide (InAs); indium gallium arsenide (InGaAs); extrinsic semiconductors, for example, doped Ge, Si, GaAs, organic semiconductors. However, other materials are also possible. Further possible photoconductive materials are described, for example, in WO2016 / 120392A1. For example, the photoconductor may be a photoconductor commercially available under the trademark Hertzstueck from trinamiX GmbH, D-67056 Ludwigshafen am Rhein, Germany.

[0013] For example, the photosensitive area may be irradiated by at least one irradiation source. The irradiation source may be, for example, an ambient light source, or may include it, and / or may be an artificial irradiation source, or may include it. As an example, the irradiation source may include at least one infrared emitter and / or at least one emitter for visible light and / or at least one emitter for ultraviolet light. As an example, the irradiation source may include at least one light-emitting diode and / or at least one laser diode. The irradiation source may in particular be one of the following irradiation sources: a laser, in particular a laser diode (however, in principle, other types of lasers can also be used alternatively or additionally); a light-emitting diode; an incandescent lamp; neon light; a flame source; an organic light source, in particular an organic light-emitting diode; a structured light source, and can include one or more of them. Alternatively or additionally, other irradiation sources can also be used. The irradiation source can generally be adapted to emit at least one light in the ultraviolet spectral range and the infrared spectral range. Most preferably, at least one irradiation source is adapted to emit light in the NIR and IR ranges, preferably in the range of 800 nm and 5000 nm, most preferably in the range of 1000 nm and 4000 nm.

[0014] The irradiation light source can include at least one non - continuous light source. Alternatively, the irradiation light source can include at least one continuous light source. The light source can be any light source having at least one emission wavelength that overlaps with the photosensitive wavelength of the photosensitive detector. For example, the light source can be configured to generate Planck radiation. For example, the light source can include at least one light - emitting diode (LED) and / or at least one laser light source. For example, the light source can be configured to generate irradiation by an exothermic reaction such as oxidation of a liquid or solid material or gas. For example, the light source can be configured to generate irradiation from a fluorescence effect. The irradiation light source can be configured to generate at least one modulated light beam. Alternatively, the light beam generated by the irradiation source can be unmodulated and / or can be modulated by further optical means. The irradiation source can include at least one optical chopper device configured to modulate a light beam from a continuous light source. The optical chopper device can be configured to periodically block the light beam from the continuous light source. For example, the optical chopper device can be or include at least one variable - frequency rotating disk chopper and / or at least one fixed - frequency tuning fork chopper and / or at least one optical shutter. The proposed device can measure and / or determine the resistance of a photoconductor independent of the light modulation frequency. Thus, the proposed device enables measurement of the photoconductor resistance of the irradiation light source without modulated light intensity.

[0015] As used herein, the term "photoconductor readout circuit" is a broad term and should be given the meaning that is ordinary and customary to those of ordinary skill in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to an electronic circuit configured to read at least one photoconductor and / or a plurality of photoconductors.

[0016] The photoconductor readout circuit is - At least one measurement voltage divider circuit, wherein the photoconductor is in series with at least one capacitor, and the capacitor is chargeable by the photoconductor; - At least one comparator circuit comprising at least one reference voltage divider circuit and at least one comparator, the comparator having at least one input, the first input being electrically connected to the output of the measurement voltage divider circuit, the comparator being configured to change between two output states when the input voltage at the first input is the same as at least one reference voltage; - At least one output terminal, wherein the electrical resistance R photo of the photoconductor is determinable from the charge and discharge frequency at the output terminal; and may comprise.

[0017] As used herein, the term "voltage divider circuit" is also referred to as a potential divider and is a broad term that should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to an electronic circuit configured to generate an output voltage signal that is a part of the input voltage signal of the voltage divider circuit. As used herein, the term "measurement voltage divider circuit" is a broad term that should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to a voltage divider circuit that includes at least one photoconductor to be measured. As used herein, the term "reference voltage divider circuit" is a broad term that should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to a voltage divider circuit that includes at least two reference resistors each having a known resistance such as pre-defined or predetermined. The reference voltage divider circuit may include at least two reference resistors each having a pre-defined or predetermined resistance. As used herein, the term "reference resistor" is a broad term that should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to a resistor having a known electrical resistance R i where i is a natural number and indicates the name of the resistor.

[0018] As used herein, the term "capacitor" is a broad term and should be given the meaning that is ordinary and customary to those of skill in the art and should not be limited to a special or customized meaning. Specifically and without limitation, this term can refer to at least one element configured to collect and / or store electrical energy, particularly electrons generated from a photoconductor. The capacitor is arranged in series with the photoconductor. The capacitor can be charged by the photoconductor. In particular, at least one output of the photoconductor can be electrically connected to at least one input of the capacitor. Electrical resistance R photo The smaller the electrical resistance R is, the faster the capacitor C is charged. In a general voltage divider, the maximum dynamic range of the output signal is achieved when the resistance values of both resistors are the same. A photoconductor may generally have a resistance value exceeding 100 kΩ. When the resistance value is large, high thermal noise may be generated in the circuit. Low-noise, high-temperature stability resistors based on metal foil technology are generally found to have lower resistance values and thus cannot be applied as voltage dividers. In the circuit according to the present invention, the resistor of the measurement voltage divider is replaced by a capacitor.

[0019] As used herein, the term "comparator circuit" is a broad term and should be given the meaning that is ordinary and customary to those of skill in the art and should not be limited to a special or customized meaning. Specifically and without limitation, this term can refer to an electronic circuit configured to compare at least one input voltage, specifically at least one measured voltage, with at least one reference voltage, specifically at least one known or predetermined reference voltage. The comparator circuit may be configured to output an output signal indicating the result of the comparison. The comparator circuit may be embodied as an inverting Schmitt trigger. The inverting Schmitt trigger can include a comparator and positive feedback to the non-inverting input of the comparator implemented by a voltage dividing circuit (in this case, a reference voltage divider).

[0020] The comparator circuit includes at least one comparator. As used herein, the term "comparator" is a broad term and should be given the ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, this term can refer to an electronic element configured to compare at least one input voltage with at least one reference voltage and to generate an output signal indicating the result of the comparison. A comparator, specifically an electronic comparator element, can be one or more of at least one operational amplifier; at least one Schmitt trigger; at least one logic element based on emitter-coupled logic (ECL); at least one transistor-transistor logic (TTL) such as at least one advanced Schottky (ASTTL), at least one FAST-Schottky, at least one high-speed CMOS, and at least one CMOS; and at least one tri-state logic comparator, or can include them. For example, the comparator can be or can include at least one operational amplifier and / or at least one additional electronic element configured to perform the recited operations. As used herein, the term "comparison" is a broad term and should be given the ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, this term can refer to performing at least one mathematical operation such as dividing or subtracting an input voltage by a reference voltage without limitation.

[0021] For the resistors of the reference voltage dividing circuit, only the ratio of the resistors may be important. The ratio of the reference resistors of the reference voltage dividing circuit may be the same as long as the resistance values of both resistors change by the same coefficient, and resistors can be used over a wide range of resistance values.

[0022] The comparator may be driven by a supply voltage. For example, two identical DC voltages in the range of ±0.001V to ±5000V, preferably ±1V to ±500V, more preferably ±2V to ±50V, may be applied to the supply input of the comparator. The comparator may be driven by a single supply voltage, and the supply voltage may be in the range of ±0.001V to ±5000V. Preferably, the supply voltage may be ±0.1V to ±500V, and most preferably, the supply voltage may be ±1V to ±50V. Alternatively, the comparator may be driven by a dual supply voltage that can be ±0.001V to ±5000V. Preferably, the supply voltage may be ±0.1V to ±500V, and most preferably, the supply voltage may be ±1V to ±50V. The dual supply voltage of the comparator can be symmetric or asymmetric.

[0023] The comparator has at least one input. For example, the comparator may have at least two inputs such as two input terminals. The comparator may include at least a first input and at least a second input. Specifically, the comparator may have an inverting input (-) and a non-inverting input (+). The output of the reference voltage divider may be connected to the non-inverting input of the comparator, while the output of the measurement voltage divider may be connected to the inverting input. In this way, the first input is electrically connected to the output of the measurement voltage dividing circuit, and the second input is electrically connected to the output of the reference voltage dividing circuit. The first input may be the inverting input, and the second input may be the non-inverting input. The reference voltage divider may be configured to provide positive feedback to the comparator. In particular, the reference voltage divider may be arranged such that a part of the output voltage of the comparator appears at the non-inverting input. In other embodiments, the comparator may include only one input. In this case, the comparator may include an internal comparison voltage.

[0024] The output signal of the comparator (also referred to as the output voltage) may depend on the result of comparing the input voltage and the reference voltage. The voltage at the first input is herein referred to as the input voltage, specifically the measured voltage signal V measis shown as. The voltage at the second input of the comparator or the internal reference voltage (e.g., in the case of a Schmitt trigger) is the reference voltage V ref is shown as. The comparator is configured to change between two output states when the input voltage at the first input is the same as the reference voltage.

[0025] The output signal can be a digital signal, particularly a binary digital output having two states shown as output states. The output state V out depends on which of the input voltage or the reference voltage is greater:

Number

[0026] When the measured voltage is lower than the reference voltage, the output voltage becomes "high". The "high" output state can be positive and particularly equal to the positive saturation voltage. When the measured voltage becomes equal to the reference voltage, i.e., by further charging the capacitor, the comparator changes the output state to "low", particularly to a state equal to the negative saturation voltage. In this case of switching from the high output state to the low output state, as a result of the negative saturation voltage of the output of the comparator, a negative voltage may appear at the non-inverting input. Therefore, for the same input signal, the output signal switches the potential at the output of the comparator to the opposite sign. Furthermore, the inverting Schmitt trigger can exhibit hysteresis. When the output state changes, the reference voltage of the non-inverting input changes, resulting in two different reference voltage values and two different values for switching the output state.

[0027]

Number

[0028] The photoconductive readout circuit may include at least one amplifier configured to amplify the output signal of the comparator circuit, particularly at least one impedance converter.

[0029] The device, particularly the photoconductive readout circuit, may include at least one coupling to at least one evaluation device. The photoconductive readout circuit can include at least one rectifier and at least one additional voltage divider for coupling to a low-voltage evaluation system such as at least one microcontroller for frequency measurement. The coupling can include at least one diode and at least one coupling voltage divider circuit. The coupling may be arranged at the output of the comparator circuit.

[0030] The photoconductor readout circuit includes at least one bias voltage source configured to apply at least one modulation bias voltage to the photoconductor. As used herein, the term "bias voltage source" refers to at least one voltage source configured to generate a bias voltage. The bias voltage may be a voltage applied across the photoconductor material. A typical readout circuit may be based on a voltage divider that is susceptible to variations in the bias voltage. Any noise in the bias voltage can be measured as the measured voltage at the output of the voltage divider. In the circuit according to the present invention, the reference voltage divider and the measurement voltage divider may be connected to the same potential that is the output voltage of the comparator. Thereby, the susceptibility to variations can be removed.

[0031] As used herein, the term "modulated bias voltage" refers to the fact that the bias voltage is a periodic time-dependent bias voltage and / or an alternating current (AC) bias voltage. The bias voltage source may be configured to vary the bias voltage for each charge and / or discharge. As used herein, the term "modulation" refers to a change in the polarization of the bias voltage on the photoconductor such that the net flow of charge carriers through the photoconductor becomes zero over the measurement period. Specifically, the bias voltage is selected such that the integral of charge carriers, such as the total current flowing through the photoconductor during the measurement period, is zero. The measurement period can be the time between two consecutive transitions of the bias voltage polarization in the same direction, such as from a rising edge, e.g., a positive edge, to a rising edge, or from a falling edge, e.g., a negative edge, to a falling edge. The change in the bias voltage associated with each charge or discharge can make it possible to protect the photoconductor from resistance drift. Typically, the photoconductor is measured with a DC bias voltage that can lead to the drift of ions in the photoconductor material or substrate (which can change the characteristics of the photoconductor). As proposed in the present invention, by using an AC bias voltage of an appropriate frequency, the drift of ions can be canceled out. The AC bias voltage can reduce noise such as flicker noise, 1 / f noise, or pink noise. The F noise can be significantly reduced by modulation of the measurement and realization of a high frequency. At the output, the frequency can be measured using one or more operations from the group consisting of at least one Fourier transform; counting of frequencies, edge detection, period length measurement, etc. The bias voltage can be from ±0.001 V to ±5000 V. Preferably, the bias voltage can be from ±0.1 V to ±500 V, and most preferably, the bias voltage can be from ±1 V to ±50 V. The bias voltage can be a switching between positive and negative. The photoconductor can be characterized by resistance asymmetry with respect to the positive and negative bias voltages. Since the integral of charge carriers over the measurement period in the proposed circuit is zero, the asymmetry can be made not to affect the resistance measurement. The electric field applied to the photoconductive material can be about 50 V / mm due to the bias voltage.

[0032] The photoconductor readout circuit can include a plurality of photoconductors. The photoconductors may be arranged in an array. The photoconductor readout circuit may be configured to determine the electrical resistance of each of the plurality of photoconductors. The photoconductor readout circuit for reading out the plurality of photoconductors may include at least one logic gate such as programmable logic, for example at least one field programmable gate array (FPGA), an integrated circuit having single or multiple input channels, a microprocessor having single or multiple inputs, etc. The FPGA may be configured as a free-running ring oscillator. Thereby, a very high time resolution can be generated in the measurement of the output frequency of the comparator.

[0033] The photoconductor readout circuit may further include at least one analog-to-digital converter (ADC) configured to convert the output signal into a digital signal, particularly for further evaluation.

[0034] The photoconductor readout circuit can be embodied as an integrated circuit. The term "integrated circuit" as used herein is a broad term and should be given the meaning that is ordinary and customary to those skilled in the art and should not be limited to a special meaning or a customized meaning. Specifically, without limitation, this term can refer to an electronic circuit on a substrate such as a semiconductor substrate. For example, the integrated circuit may be embodied as a microchip.

[0035] In one embodiment, the device may include at least one first electronic circuit. The first electronic circuit may be configured to generate at least one first output signal. The frequency of the first output signal may be a mathematical function of the measurement period of the photoconductor. The output of the photoconductor readout circuit may be a frequency that depends on the resistance of the photoconductor. A counter for measuring the frequency may be required as the output of the photoconductor readout circuit. Since a high frequency is required to reduce 1 / f noise, the counter may be configured to sample a high frequency with high precision and low noise, such as jitter.

[0036] The device may include at least one second photoconductor configured to exhibit an electrical resistance R that depends on the irradiation of its photosensitive area. photo2 The device may include at least one second electronic circuit configured to generate a second measurement period. The second electronic circuit may be configured to generate at least one second output signal. The frequency of the second output signal may be a mathematical function of the measurement period of the photoconductor and the measurement period of the second photoconductor.

[0037] The second electronic circuit may be a frequency mixer. In the case of dual detector applications where one detector measures the light intensity at a specific wavelength, such as in non-dispersive infrared spectroscopy for gas analysis, and one detector measures the light intensity at another wavelength, the two measurement signals need to be compared. Another example could be temperature measurement independent of emissivity, where the radiant output of the measurement target is measured at two different wavelengths and the signals are compared. The second electronic circuit that performs frequency counting may be configured to sample the two signals with the same accuracy and low noise. This may further increase the requirements and costs of the frequency counter. Alternatively, it is also possible to employ a period length counter. The requirements for the period length counter and the frequency counter may remain the same. The output signals of both photoconductor readout circuits for dual applications may be digitized individually. Since the output signals of both photoconductor readout circuits may be frequencies, both frequencies can be sampled by a frequency counter, which can be implemented in the form of a timer using a microcontroller, FPGA, Time-to-Digital Converter (TDC). This approach may require two input channels for the microcontroller and FPGA, or it may be necessary to employ two of these counters with very good time resolution. Additionally or alternatively, the frequencies of both photoconductor readout circuits can be mixed using a frequency mixer at the analog level before digitization. The frequency mixer may be, or may include, a non-linear electrical circuit configured to generate a new frequency from the two signals applied to it. The frequency mixer may be configured to take in the two applied signals and generate a new signal equal to the difference and sum of the original frequencies. The sum of the original frequencies, i.e., the output signals of the photoconductor readout circuits, can be filtered by a simple low-pass filter, while the difference can be sampled.

[0038] For example, mixing two frequencies f1 = 10000 Hz and f2 = 9960 Hz to get f Mixed=f1 - f2 = 40 Hz can be filtered, which can be measured with very high resolution even using an ordinary period or frequency counter. In this way, while reducing requirements and costs, especially the number of counters, the resolution can be increased. The measurement resolution depends on the heterodyne factor, especially the ratio f1 / f of the carrier f1 to the beat frequency f Mixed and can be increased by the ratio f1 / f of the carrier f1 to the beat frequency f Mixed In the example described, the heterodyne factor is 10000 / 40 = 250. Thus, a period counter with a resolution of 100 nanoseconds can resolve a change in the period length of 400 picoseconds.

[0039] Frequency mixers are generally known to those skilled in the art. A wide variety of frequency mixers are available, especially in different frequency ranges, noise levels, package forms, as integrated circuits or as discrete components.

[0040] The device may include at least one temperature - sensitive element. The signal of the temperature - sensitive element can be used to correct one or both of the first output signal and the second output signal of the first electronic circuit.

[0041] The device may include at least one third resistor that has the same temperature dependence as the photoconductor and exhibits an irradiation - independent electrical resistance. The third resistor may be either a photoconductor darkened so as not to receive irradiation or a non - photosensitive resistor. The device may include at least one third electronic circuit configured to generate a third frequency. The third frequency may function as a reference frequency. The reference frequency may be used by at least two electronic circuits to generate a frequency difference from the irradiated photoconductor. The measured resistance and the specific detectivity at the measured wavelength may drift due to thermal changes, such as environmental temperature effects, instability of the thermoelectric cooler employed, etc. Therefore, an additional dark photoconductor covered so that its active region is not irradiated at all can be employed. The output frequency of this detector is used as the reference f Refcan be achieved. By using a dual mixer configuration, f Mixed1 = f1 - f Ref and f Mixed2 = f2 - f Ref the difference between can be measured with high precision. By calculating the quotient f Mixed1 / f Mixed2 the temperature dependencies of f1 and f2 can be removed. For example, if the temperature coefficient of the photoconductor is α, the quotient with respect to temperature T is, [Equation] and thus is temperature-independent.

[0042] Furthermore, the frequency divider can be adopted in such a way that its frequency output is an integer division of a power of 2 of the input signal, and the power can be freely selected. In the case of the fifth power, the output frequency is 1 / 32 of the input frequency. To measure the temperature of the photoconductor, an inexpensive temperature sensor such as a negative temperature coefficient thermistor (NTC) can be constructed. The temperature dependence of the dark resistance can be calibrated at the factory, and the measured value can be corrected with a temperature dependence calibration factor.

[0043] In a further aspect of the present invention, a detector including at least one photoconductor readout circuit according to the present invention is disclosed. The detector further comprises at least one evaluation device configured to determine an output signal at at least one output of the device, in particular the output signal of the photoconductor readout circuit. The evaluation device is configured to determine the electrical resistance R photo of the photoconductor by evaluating the output signal.

[0044] As used herein, the term "evaluation device" generally refers to any device designed to determine and / or generate at least one voltage output signal in a voltage output. As an example, the evaluation device may be or may comprise one or more integrated circuits such as one or more application specific integrated circuits (ASICs), and / or one or more data processing devices, for example one or more computers, preferably one or more microcomputers and / or microcontrollers, or may include these. Additional components may be included, such as one or more preprocessing devices and / or data collection devices, for example devices for receiving and / or preprocessing one or more voltage signals, for example one or more analog-to-digital converters and / or one or more filters. Further, the evaluation device can include one or more data storage devices. The evaluation device can include one or more interfaces, for example one or more wireless interfaces and / or one or more wired interfaces. In particular, the evaluation device can include at least one data processing device, in particular an electronic data processing device that can be designed to determine at least one output voltage signal. The evaluation device can also be designed to completely or partially control at least one irradiation source, and / or to control at least one voltage source, and / or to adjust at least one load resistor. The evaluation device can further include one or more additional additional components, for example one or more electronic hardware components and / or one or more software components, for example one or more measurement units and / or one or more evaluation units and / or one or more control units. For example, the evaluation device can include at least one measurement device adapted to measure at least one output voltage signal, for example at least one voltmeter. The evaluation device may be configured to perform one or more operations from the group consisting of at least one Fourier transform; counting of frequencies, edge detection, period length measurement, etc.

[0045] The detector may include at least one irradiation light source.

[0046] For further details regarding this aspect of the invention, particularly further details of the photoconductor readout circuit, the evaluation device and any irradiation source, reference can be made to the description of the photoconductor readout circuit provided in more detail above and below.

[0047] In a further aspect of the invention, the use of the device according to the invention for the purpose of reading out one or more of at least one PbS sensor, at least one PbSe sensor, or at least one pixelated sensor array comprising a plurality of pixels (each pixel comprising at least one PbS or PbSe sensor) is disclosed. In particular, the device according to the invention can be used in medium or low bias voltage applications, for example applications where the device is battery-powered or needs to operate at low power, such as sensor nodes, portable measurement devices, devices in explosive atmospheres, etc., enabling an improved signal-to-noise ratio and thus high signal quality. For example, the voltage divider circuit can be used in a spectrometer, a moisture meter, a thickness measuring instrument, a gas analyzer, or any other type of instrument that uses a photoconductor as a sensor element with the photoconductor. The present device can be used for optical sensors. For example, the voltage divider circuit can be used in optical sensors that utilize the so-called FiP effect, such as WO2012 / 110924A1, WO2014 / 097181A1, WO2016 / 120392A1. Known voltage divider circuits cannot measure changes in resistance with high resolution without optical modulation. For example, a spectrometer using a photoconductive detector can only be realized with a dispersive element and multiple pixels. A single-pixel spectrometer uses other current-generating detectors such as InGaS, Si photodiodes, etc. for stability to enable measurements without optical modulation. Since the device according to the invention can measure changes in the resistance of a photoconductor with high precision without optical modulation, a single-pixel spectrometer based on, for example, a Michelson interferometer or a Fabry-Perot interferometer can also be realized by a photoconductive detector. The proposed device having all the advantages described above can be used to realize a single-pixel spectrometer.

[0048] In summary, in the context of the present invention, the following embodiments are considered particularly preferred.

[0049] Embodiment 1: - At least one photoconductor configured to exhibit an electrical resistance R depending on the irradiation of the photosensitive region of the photoconductor; photo and at least one photoconductor readout circuit configured to determine the electrical resistance R of the photoconductor, the photoconductor readout circuit comprising at least one bias voltage source configured to apply at least one modulation bias voltage to the photoconductor. - At least one photoconductor readout circuit configured to determine the electrical resistance R of the photoconductor, the photoconductor readout circuit comprising at least one bias voltage source configured to apply at least one modulation bias voltage to the photoconductor. photo and at least one photoconductor readout circuit configured to determine the electrical resistance R of the photoconductor, the photoconductor readout circuit comprising at least one bias voltage source configured to apply at least one modulation bias voltage to the photoconductor. is provided.

[0050] Embodiment 2: The device according to the preceding embodiment, wherein the bias voltage is a periodic time-dependent bias voltage, the bias voltage being selected such that the integration of the charge carriers flowing through the photoconductor over the measurement period is zero, the measurement period being defined by the time between two consecutive transitions of the bias voltage polarization in the same direction.

[0051] Embodiment 3: The photoconductor readout circuit is - At least one measurement voltage division circuit comprising at least one photoconductor configured to exhibit an electrical resistance R depending on the irradiation of the photosensitive region of the photoconductor and at least one capacitor in series with the photoconductor, the capacitor being chargeable by the photoconductor; photo and at least one comparator circuit comprising at least one reference voltage division circuit and at least one comparator, the comparator having at least one input, the first input being electrically connected to the output of the measurement voltage division circuit, the comparator being configured to change between two output states when the input voltage at the first input is the same as at least one reference voltage; - At least one output terminal for the electrical resistance R of the photoconductor - At least one output terminal for the electrical resistance R of the photoconductor photois at least one output terminal that can be determined from the charge and discharge frequency at the output terminal, A device according to any one of the preceding embodiments, comprising

[0052] Embodiment 4: The device according to the preceding embodiment, wherein the reference voltage dividing circuit includes at least two reference resistors each having a predefined or predetermined resistance.

[0053] Embodiment 5: The device according to any one of the preceding two embodiments, wherein the comparator is one or more of at least one operational amplifier; at least one Schmitt trigger; at least one logic element based on emitter-coupled logic (ECL); at least one transistor-transistor logic (TTL) such as at least one advanced Schottky (ASTTL), at least one FAST-Schottky, at least one high-speed CMOS, and at least one CMOS; and at least one tri-state logic comparator, or includes them.

[0054] Embodiment 6: The device according to any one of the preceding three embodiments, wherein the comparator is configured to compare the input voltage with at least one reference voltage and generate an output signal indicating the result of the comparison.

[0055] Embodiment 7: The device according to any one of the preceding four embodiments, wherein the charging and discharging speed of the capacitor depends on the resistance R photo

[0056] Embodiment 8: The device according to any one of the preceding five embodiments, wherein the photoconductive readout circuit includes at least one amplifier configured to amplify the output signal of the comparator circuit.

[0057] Embodiment 9: The device according to any one of the preceding embodiments, including at least one coupling to at least one evaluation device.

[0058] Embodiment 9: The device according to any one of the preceding embodiments, wherein the photosensitive region comprises at least one photoconductive material selected from the group consisting of lead sulfide (PbS); lead selenide (PbSe); mercury cadmium telluride (HgCdTe); cadmium sulfide (CdS); cadmium selenide (CdSe); indium antimonide (InSb); indium arsenide (InAs); indium gallium arsenide (InGaAs); extrinsic semiconductors, and organic semiconductors.

[0059] Embodiment 10: The device according to Embodiment 2, comprising at least one first electronic circuit configured to generate at least one first output signal, wherein the frequency of the first output signal is a mathematical function of the measurement period of the photoconductor.

[0060] Embodiment 11: The device according to the preceding embodiments, comprising at least one temperature-sensitive element, wherein the signal of the temperature-sensitive element is used to correct the first output signal of the first electronic circuit.

[0061] Embodiment 12: The device according to any one of the preceding two embodiments, comprising at least one second photoconductor configured to exhibit an electrical resistance R that depends on the irradiation of its photosensitive region. photo2 The device further comprises at least one second electronic circuit configured to generate a second measurement period, and the second electronic circuit is configured to generate at least one second output signal, wherein the frequency of the second output signal is a mathematical function of the measurement period of the photoconductor and the measurement period of the second photoconductor.

[0062] Embodiment 13: The device according to the preceding embodiment, wherein the second electronic circuit is a frequency mixer.

[0063] Embodiment 14: The device includes at least one third resistor that exhibits an irradiation-independent electrical resistance having the same temperature dependence as the photoconductor and the second photoconductor, and the third resistor is either a photoconductor darkened so as not to be irradiated or a non-photosensitive resistor. The device includes at least one third electronic circuit configured to generate a third frequency, and the third frequency functions as a reference frequency, and the reference frequency is used by at least two electronic circuits to generate the difference in frequency from the irradiated photoconductor. The device according to any one of the preceding two embodiments.

[0064] Embodiment 15: A detector includes at least one evaluation device configured to determine an output signal of at least one output of the device, and the evaluation device is configured to determine the electrical resistance R of the photoconductor by evaluating the output signal. photo A detector including at least one device according to any one of the preceding embodiments.

[0065] Embodiment 16: The evaluation device of the detector according to the preceding embodiment is configured to perform one or more operations from the group consisting of at least one Fourier transform, frequency counting, edge detection, period length measurement, etc.

[0066] Embodiment 17: Use of a device according to any one of the preceding embodiments for reading one or more of at least one PbS sensor, at least one PbSe sensor, or at least one pixelated sensor array including a plurality of pixels, each pixel including at least one PbS or PbSe sensor. Brief Description of the Drawings

[0067] Any further optional details and features of the present invention will become apparent from the following description of preferred exemplary embodiments in connection with the dependent claims. In this context, specific features may be implemented alone or in combination with other features. The present invention is not limited to the exemplary embodiments. The exemplary embodiments are schematically illustrated in the figures. Identical reference signs in the individual figures refer to identical elements or elements having the same function or elements corresponding to one another with respect to their function.

[0068] Specifically, in the following figures:

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0069] Exemplary Embodiment FIG. 1 shows, in a very schematic way, an exemplary embodiment of a detector 110 comprising at least one device 111 according to the present invention, which includes at least one photoconductor readout circuit 112. The device 111 comprises at least one photoconductor 114 configured to exhibit an electrical resistance R photo depending on the irradiation 116 of the photosensitive region 118 of the photoconductor 114.

[0070] The electrical resistance R photoIt may depend on the irradiation of the material of the photoconductor 114. The photosensitive region 118 of the photoconductor 114 may include a photoconductive material. The photosensitive region 118 may include at least one photoconductive material selected from the group consisting of lead sulfide (PbS); lead selenide (PbSe); mercury cadmium telluride (HgCdTe); cadmium sulfide (CdS); cadmium selenide (CdSe); indium antimonide (InSb); indium arsenide (InAs); indium gallium arsenide (InGaAs); extrinsic semiconductors, for example, doped Ge, Si, GaAs. However, other materials are also possible. Further possible photoconductive materials are described, for example, in WO2016 / 120392A1. For example, the photoconductor may be a photoconductor commercially available under the trade name Hertzstueck from trinamiX GmbH, D-67056 Ludwigshafen am Rhein, Germany.

[0071] For example, the photosensitive region 118 may be irradiated by at least one irradiation source 120. The irradiation source 120 may be, for example, an ambient light source or may include it, and / or may be an artificial irradiation source or may include it. The detector 110 may include at least one irradiation source 120 configured to irradiate the photosensitive region 118. As an example, the irradiation source 120 may include at least one infrared emitter and / or at least one emitter for visible light and / or at least one emitter for ultraviolet light. As an example, the irradiation source 120 may include at least one light-emitting diode and / or at least one laser diode. The irradiation source 120 may in particular be one or more of the following irradiation sources: lasers, in particular laser diodes (although in principle, alternatively or additionally, other types of lasers can also be used); light-emitting diodes; incandescent lamps; neon lights; flame sources; organic light sources, in particular organic light-emitting diodes; structured light sources. Alternatively or additionally, other irradiation sources can also be used. The irradiation source 120 can generally be adapted to emit at least one light in the ultraviolet spectral range, infrared spectral range. Most preferably, at least one irradiation source is adapted to emit light in the NIR and IR ranges, preferably in the range of 800 nm and 5000 nm, most preferably in the range of 1000 nm and 4000 nm. The irradiation source 120 may include at least one continuous light source or at least one non-continuous light source.

[0072] The photoconductive readout circuit 112 includes at least one measurement voltage-dividing circuit 122 including at least one photoconductor 114 and at least one capacitor C124 connected in series with the photoconductor 114. The capacitor C124 can be charged by the photoconductor 114. In particular, at least one output of the photoconductor 114 can be electrically connected to at least one input of the capacitor 124. Electrical resistance R photoThe smaller it is, the faster the capacitor C is charged. In a general voltage divider, the maximum dynamic range of the output signal is achieved when the resistance values of both resistors are the same. A photoconductor may generally have a resistance value exceeding 100 kΩ. When the resistance value is large, high thermal noise may occur in the circuit. Low-noise, high-temperature stability resistors based on metal foil technology are generally found at lower resistance values and thus cannot be applied as voltage dividers. In the circuit according to the present invention, the resistor of the measurement voltage divider is replaced by a capacitor 124. The capacitor C124 may further be grounded.

[0073] The photoconductor readout circuit 112 includes at least one comparator circuit 126 including at least one reference voltage dividing circuit 128 and at least one comparator 130. The comparator circuit 126 may be configured to compare at least one input voltage with at least one reference voltage and output an output signal indicating the result of the comparison. The comparator circuit 126 may be embodied as an inverting Schmitt trigger. The inverting Schmitt trigger can include a comparator 130 and positive feedback to the non-inverting input of the comparator implemented by a voltage dividing circuit (in this case, the reference voltage divider 128). The reference voltage dividing circuit 128 can include at least two reference resistors 132 (designated as R2 and R3 in FIG. 1), each having a predefined or predetermined resistance. The resistor R2 may be connected in series with the resistor R3. The resistor R2 may be connected to the output of the comparator 130. R3 may further be grounded. The comparator 130 may be one or more of at least one operational amplifier; at least one Schmitt trigger; at least one logic element based on emitter-coupled logic (ECL); at least one transistor-transistor logic (TTL) such as at least one advanced Schottky (ASTTL), at least one FAST-Schottky, at least one high-speed CMOS, and at least one CMOS; and at least one tri-state logic comparator, or may include them.

[0074] For the resistors of the reference voltage dividing circuit 128, only the ratio of the resistors may be important. The ratio of the reference resistors of the reference voltage dividing circuit may be the same as long as the resistance values of both resistors change by the same coefficient (which enables the use of resistors over a wide range of resistance values). The comparator 130 has at least one input 134, in particular two input terminals as shown in FIG. 1. The comparator may include at least one first input 136 and at least one second input 138. Specifically, the comparator 130 may have a non-inverting input (+) and an inverting input (-). The output of the reference voltage divider 128 may be connected to the non-inverting input of the comparator, while the output of the measurement voltage divider 122 may be connected to the inverting input. In this way, the first input 136 is electrically connected to the output of the measurement voltage dividing circuit 122, and the second input is electrically connected to the output of the reference voltage dividing circuit 128. The first input 136 may be an inverting input, and the second input may be a non-inverting input. The reference voltage divider 128 may be configured to provide positive feedback to the comparator 130. In particular, the reference voltage divider 128 may be arranged such that a part of the output voltage of the comparator 130 appears at the non-inverting input.

[0075] The output signal of the comparator 130 (also referred to as the output voltage) may depend on the result of comparing the input voltage at the first input 136 with at least one reference voltage. In the embodiment of FIG. 1, the reference voltage may be the input voltage at the second input 138. The voltage at the first input 136 is denoted herein as the measurement voltage signal V meas and the voltage at the second input 138 is denoted as the reference voltage signal V ref . The comparator 130 is configured to change between two output states when the input voltages at the first input and the second input are the same. The output signal can be a digital signal, in particular a binary digital output having two states shown as output states. The output state V out depends on which input voltage is greater:

Number

[0076] When the measured voltage is lower than the reference voltage, the output voltage becomes "high". The "high" output state may be positive, especially equal to the positive saturation voltage. When the measured voltage becomes equal to the reference voltage, i.e., by further charging the capacitor, the comparator changes the output state to "low", especially to a state equal to the negative saturation voltage. In this case of switching from the high output state to the low output state, as a result of the negative saturation voltage of the output of comparator 130, a negative voltage may appear at the non-inverting input. Therefore, for the same input signal, the output signal switches the potential at the output of comparator 130 to the opposite sign. Further, the inverting Schmitt trigger can exhibit hysteresis. When the output state changes, the reference voltage of the non-inverting input changes, resulting in two different reference voltage values, and thus two different values for switching the output state.

[0077]

Number

[0078] Detector 110 further comprises at least one evaluation device 142 configured to determine an output signal at at least one output 140 of the device, in particular of the photoconductive readout circuit 112. The evaluation device 142 is configured to determine the electrical resistance R of the photoconductor 114 by evaluating the output signal. photo The evaluation device 142 may be, or may comprise, one or more integrated circuits, such as one or more application-specific integrated circuits (ASICs), and / or one or more data processing devices, for example one or more computers, preferably one or more microcomputers and / or microcontrollers. Additional components may be included, such as one or more preprocessing devices and / or data collection devices, for example devices for receiving and / or preprocessing one or more voltage signals, such as one or more AD converters and / or one or more filters. Furthermore, the evaluation device 142 may include one or more data storage devices. The evaluation device 142 may include one or more interfaces, such as one or more wireless interfaces and / or one or more wired interfaces. In particular, the evaluation device 142 may include at least one data processing device, in particular an electronic data processing device designed to determine at least one output voltage signal. The evaluation device 142 may also be designed to completely or partially control at least one irradiation source and / or to control at least one voltage source and / or to adjust at least one load resistor. The evaluation device 142 may further include one or more additional additional components, such as one or more electronic hardware components and / or one or more software components, such as one or more measurement units and / or one or more evaluation units and / or one or more control units. For example, the evaluation device 142 may comprise at least one measuring device adapted to measure at least one output voltage signal, such as at least one voltmeter. The evaluation device 142 may be configured to perform one or more operations from the group consisting of at least one Fourier transform; counting of frequencies, edge detection, period length measurement, etc.

[0079] FIG. 2 shows a further embodiment of the device 111 and the photoconductive readout circuit 112. In addition to the elements shown in FIG. 1, in the embodiment of FIG. 2, the photoconductive readout circuit 112 comprises at least one additional amplifier 144, in particular at least one impedance converter configured to amplify the output signal of the comparator circuit 126. The additional amplifier 144 may be connected to a further voltage divider including resistors R1 and R4. The resistor R1 may be connected to the output of the further amplifier 144 and the resistor R4, and the resistor R4 may be grounded. The output of the further voltage divider may be connected to the non-inverting input of the additional amplifier 144.

[0080] FIG. 3 shows a further embodiment of the device 111 and the photoconductive readout circuit 112. In addition to the elements shown in FIG. 1, in the embodiment of FIG. 3, the photoconductive readout circuit 112 includes at least one coupling 146 to at least one evaluation device 142. The photoconductive readout circuit 112 may include at least one rectifier 148 and at least one further voltage divider 150 for coupling to a low-voltage evaluation system such as at least one microcontroller for frequency measurement. The coupling 146 may include at least one diode and at least one coupling voltage divider circuit. The coupling 146 may be arranged at the output of the comparator circuit 126.

[0081] The photoconductor readout circuit 112 comprises at least one bias voltage source 152 configured to apply at least one modulation bias voltage to the photoconductor 114. A general readout circuit may be based on a voltage divider that is susceptible to variations in the bias voltage. Any noise in the bias voltage can be measured as the measured voltage at the output of the voltage divider. In the circuit according to the present invention, the reference voltage divider 128 and the measurement voltage divider 122 may be connected to the same potential that is the output voltage of the comparator. Thereby, the susceptibility to variations can be removed. The modulation bias voltage can be a periodic time-dependent bias voltage and / or an alternating current bias voltage. The bias voltage source 152 may be configured to change the bias voltage for each charge and / or discharge. The modulation can be a change in the polarization of the bias voltage on the photoconductor 114 such that the net flow of charge carriers through the photoconductor 114 becomes zero over the measurement period. Specifically, the bias voltage is selected such that the integration of charge carriers such as the total current flowing through the photoconductor 114 over the measurement period is zero. The measurement period can be the time between two consecutive transitions of the bias voltage polarization in the same direction, such as from a rising edge (e.g., a positive edge) to a rising edge or from a falling edge (e.g., a negative edge) to a falling edge. The change in the bias voltage associated with each charge or discharge can make it possible to protect the photoconductor 114 from resistance drift. Usually, the photoconductor is measured with a DC bias voltage that can lead to the drift of ions in the photoconductor material or substrate (which can change the characteristics of the photoconductor). As proposed in the present invention, by using an alternating current bias voltage of an appropriate frequency, the drift of ions can be offset. The alternating current bias voltage can reduce noise such as flicker noise, 1 / f noise or pink noise. The F noise can be significantly reduced by modulation of the measurement and realization of a high frequency. At the output, the frequency can be measured using one or more operations from the group consisting of at least one Fourier transform; counting of frequencies, edge detection, etc. The bias voltage can be in the range of ±0.001 V to ±5000 V.Preferably, the bias voltage can be from ±0.1 V to ±500 V, and most preferably, the bias voltage can be from ±1 V to ±50 V. The bias voltage may be switched between positive and negative. The photoconductor 114 can be characterized by resistance asymmetry with respect to the positive bias voltage and the negative bias voltage. Since the integration of charge carriers over the measurement period in the proposed circuit is zero, the asymmetry can be made not to affect the resistance measurement. The electric field across the photoconductive material can be about 50 V / mm due to the bias voltage.

[0082] Comparator 130 may be driven by supply voltage 156. For example, two identical DC voltages in the range of ±0.001 V to ±5000 V, preferably ±1 V to ±500 V, more preferably ±2 V to ±50 V, may be applied to the supply input 158 of comparator 130. Comparator 130 may be driven by a single supply voltage 156, and the supply voltage 156 can be in the range of ±0.001 V to ±5000 V. Preferably, the supply voltage 156 can be from ±0.1 V to ±500 V, and most preferably, the supply voltage 156 can be from ±1 V to ±50 V. Alternatively, comparator 130 may be driven by a dual supply voltage that can be from ±0.001 V to ±5000 V. Preferably, the supply voltage 156 can be from ±0.1 V to ±500 V, and most preferably, the supply voltage 156 can be from ±1 V to ±50 V. The dual supply voltage of the comparator can be symmetric or asymmetric.

[0083] Furthermore, in FIG. 3, sub - figures 1) to 4) are shown. Sub - figure 1) shows an exemplary measured voltage signal V meas (unit: V) as a function of time (unit: ms). Sub - figure 2) shows an exemplary reference voltage V ref (unit: V) as a function of time (unit: ms). Sub - figure 3) shows an exemplary output of comparator 130. Sub - figure 4) shows an exemplary input voltage (unit: V) as a function of time (unit: ms) of evaluation device 142.

[0084] FIG. 4 shows a further embodiment of apparatus 111 and photoconductive readout circuit 112. In addition to the elements shown in FIG. 1, in the embodiment of FIG. 4, the photoconductive readout circuit 112 may comprise at least one bias voltage source 152 configured to apply at least one bias voltage to the photoconductor 114. As shown in FIG. 4, the photoconductive readout circuit 112 includes a coupling 146. In FIG. 4, the coupling 146 can include at least one metal-oxide-semiconductor field effect transistor (MOSFET) 154.

[0085] The resistors R2 and R3 in FIGS. 1-4 may alternatively or additionally be embodied as temperature-dependent resistors such as at least one negative temperature coefficient thermistor (NTC), or at least one temperature-sensitive diode, or at least one positive temperature coefficient thermistor (PTC), or at least one additional photoconductor. Thereby, the temperature dependence of the photoconductor 114 can be compensated.

[0086] FIGS. 5A-5C show further embodiments of apparatus 111 and photoconductive readout circuit 112 according to the present invention. In FIG. 5A, the comparator 130 is embodied as a Schmitt trigger 160. The readout circuit operates as described with respect to FIGS. 1-4, but the comparator 130 may include an internal comparison voltage used as a reference voltage. In FIG. 5B, the comparator 130 is embodied as an inverter gate. The inverter gate may operate like a Schmitt trigger, and the threshold of the input voltage in the comparator is adapted to the circuit technology used. In the case of transistor-transistor logic (TTL), the threshold is U e <0.8V for the low level and U e >2V for the high level. Alternatively, other digital circuit technologies such as CMOS may be used. In FIG. 5C, the comparator 130 may be embodied as an inverter circuit including discrete components such as two transistors. Embodiments are also possible in which the circuit is composed of discrete components configured to generate an oscillation having a frequency that depends on the conductivity of the photoconductor 114 instead of integrated components.

[0087] Figure 6 shows a further embodiment of the apparatus 111 and the photoconductive readout circuit 112. In addition to the elements shown in FIG. 1, in the embodiment of FIG. 6, the photoconductive readout circuit 112 includes at least one additional comparator 131, while the output of the first comparator 130 is connected to the inverting input of the additional comparator 131. The non-inverting inputs of the comparator 130 and the additional comparator 131 are connected to the same potential. A single DC voltage source, such as a TTL power supply or a battery having a constant DC supply voltage of V supply may be supplied. In this embodiment, the bias voltage applied on the photoconductor is still modulated so that the net flow of charge carriers through the photoconductor 114 becomes zero over the measurement period, varying its polarization between V supply and -V supply . Subfigure 1) shows an exemplary bias voltage (in volts) of the photoconductor 114 as a function of time (in milliseconds). Subfigure 2) shows an exemplary output of the comparator 130 as a function of time (in milliseconds). Subfigure 3) shows an exemplary output of the additional comparator 131 as a function of time (in milliseconds). The output of the additional comparator 131 can be phase-delayed by at least half a cycle compared to the output of the comparator 130. Alternatively, the comparator 130 and the additional comparator 131 may be replaced by a single comparator having two inputs and two outputs, where the outputs are differential from each other, which means that the output voltages have opposite polarities with respect to the common-mode operating point of the circuit.

[0088] FIG. 7 shows an embodiment in which the apparatus 111 includes a plurality of photoconductors. FIG. 7A shows an embodiment in which the apparatus 111 includes at least one second electronic circuit 162. In this embodiment, the apparatus 111 includes two photoconductors, a photoconductor 114 and a second photoconductor 164. The second electronic circuit 162 may be or include a frequency mixer. The frequencies f1 and f2 of both photoconductor readout circuits 112 can be mixed using a frequency mixer at an analog level before digitization. The frequency mixer may be or include a non-linear electrical circuit configured to generate a new frequency from two signals applied thereto. The frequency mixer may be configured to take in two applied signals and generate a new signal equal to the difference and sum of the original frequencies. The sum of the original frequencies, i.e., the output signals of the photoconductor readout circuit 112, can be filtered by a simple low-pass filter, while the difference can be sampled as visualized in FIG. 7A. The sampled difference can be measured by at least one counter 164.

[0089] For example, two frequencies f1 = 10000 Hz and f2 = 9960 Hz can be mixed and filtered to f Mixed = f1 - f2 = 40 Hz, which can be measured with very good resolution even using an ordinary period or frequency counter. In this way, the requirements and costs, especially the number of counters, can be reduced while the resolution can be increased. The measurement resolution can be increased by the heterodyne coefficient, especially the ratio f1 / f Mixed of the carrier f1 to the beat frequency f Mixed . In the example described, the heterodyne coefficient is 10000 / 40 = 250. Thus, a period counter with a resolution of 100 nanoseconds can resolve a change in the period length of 400 picoseconds.

[0090] Frequency mixers are generally known to those skilled in the art. A wide variety of frequency mixers are available, in particular, as integrated circuits or as discrete components, in different frequency ranges, noise levels, and package formats.

[0091] As shown in FIG. 7B, device 111 may include at least one third resistor 166 that exhibits an irradiation-independent electrical resistance having the same temperature dependence as photoconductor 114 and second photoconductor 164. The third resistor 166 may be either a photoconductor darkened so as not to receive irradiation or a non-photosensitive resistor. Device 111 may include at least one third electronic circuit 168 configured to generate a third frequency f Ref . The third frequency may function as a reference frequency. The reference frequency may be used by at least two electronic circuits 162, 168 to generate a frequency difference from the irradiated photoconductor. The measured resistance and the specific detectivity at the measured wavelength may drift due to thermal variations, such as environmental temperature effects, instability of the thermoelectric cooler employed, etc. Therefore, an additional dark photoconductor covered so that its active region is not irradiated at all can be employed. The output frequency of this detector can be made the reference f Ref . By using the dual mixer configuration shown in FIG. 7B, the difference between f Mixed1 = f1 - f Ref and f Mixed2 = f2 - f Ref can be measured with high precision. By calculating the quotient f Mixed1 / f Mixed2 , the temperature dependence of f1 and f2 can be removed. For example, if the temperature coefficient of the photoconductor is α, the quotient with respect to temperature T is

Equation

[0092] As shown in FIG. 7C, further, the frequency divider 170 can be adopted in such a manner that its frequency output is an integer division of a power of 2 of the input signal, and the power can be freely selected. In the case of the fifth power, the output frequency becomes 1 / 32 of the input frequency. To measure the temperature of the photoconductor, an inexpensive temperature sensor such as a negative temperature coefficient thermistor (NTC) can be constructed. The temperature dependence of the dark resistance can be calibrated at the factory, and the measured value can be corrected with a temperature dependence calibration coefficient.

Description of Reference Signs

[0093] List of Reference Numerals 110 Detector 111 Device 112 Photoconductor Readout Circuit 114 Photoconductor 116 Irradiation 118 Photosensitive Region 120 Irradiation Source 122 Measurement Voltage Divider Circuit 124 Capacitor 126 Comparator Circuit 128 Reference Voltage Divider Circuit 130 Comparator 131 Comparator 132 Reference Resistor 134 Input 136 First Input 138 Second Input 140 Output Terminal 142 Evaluation Device 144 Additional Amplifier 146 Coupling 148 Rectifier 150 Further Voltage Divider 152 Bias Voltage Source 154 MOSFET 156 Supply Voltage 158 Supply Input 160 Schmitt Trigger 162 Second Electronic Circuit 164 Counter 166 Third Resistor 168 Third Electronic Circuit 170 Divider

Claims

1. - An electrical resistance R that depends on the irradiation (116) of the photosensitive region (118) of the photoconductor (114) ｐｈｏｔｏ at least one photoconductor (114) configured as shown; - At least one photoconductor readout circuit (112), wherein the photoconductor readout circuit (112) determines the electrical resistance R of the photoconductor (114) ｐｈｏｔｏ and is provided with at least one bias voltage source (152) configured to apply at least one modulation bias voltage to the photoconductor (114), the at least one photoconductor readout circuit (112) An apparatus (111) comprising: wherein the modulation bias voltage is a periodic time-dependent bias voltage, and the modulation bias voltage is selected such that the integration of charge carriers flowing through the photoconductor (114) over a measurement period is zero, and the measurement period is defined by the time between two consecutive transitions of bias voltage polarization in the same direction; the apparatus (111) comprises at least one first electronic circuit, the first electronic circuit is configured to generate at least one first output signal, and the frequency of the first output signal is a mathematical function of the measurement period of the photoconductor (114); The device (111) has an electrical resistance R that depends on the irradiation of its photosensitive area ｐｈｏｔｏ２ and includes at least one second photoconductor (164) configured to exhibit ｐｈｏｔｏ２ , and the device (111) includes at least one second electronic circuit (162) configured to generate a second measurement period, the second electronic circuit being configured to generate at least one second output signal, the frequency of the second output signal being a mathematical function of the measurement period of the photoconductor (114) and the measurement period of the second photoconductor (164).

2. The photoconductor readout circuit (112) comprises: - at least one measurement voltage-divider circuit (122), wherein the photoconductor (114) is in series with at least one capacitor (124), and the capacitor (124) is chargeable by the photoconductor (114); at least one measurement voltage-divider circuit (122); - at least one comparator circuit (126) comprising at least one reference voltage-divider circuit (128) and at least one comparator (130), the comparator (130) comprises at least one input (134), a first input (136) is electrically connected to the output of the measurement voltage-divider circuit (122), and the comparator (130) is configured to change between two output states when the input voltage at the first input (136) is the same as at least one reference voltage; at least one comparator circuit (126); - at least one output terminal (140), the electrical resistance R of the photoconductor (114) ｐｈｏｔｏ is determinable from the charge and discharge frequency at the output terminal (140), at least one output terminal (140); and The apparatus (111) according to claim 1, comprising.

3. The apparatus (111) according to claim 2, wherein the reference voltage-divider circuit (128) comprises at least two reference resistors (132) each having a predefined or predetermined resistance.

4. The comparator (130) is one or more of, or includes, at least one operational amplifier; at least one Schmitt trigger; at least one logic element based on emitter-coupled logic (ECL); at least one transistor-transistor logic (TTL) such as at least one advanced Schottky (ASTTL); and at least one tri-state logic comparator. The comparator (130) is configured to compare the input voltage with at least one reference voltage and to generate an output signal indicating the result of the comparison, for the apparatus (111) according to claim 2 or 3.

5. The charge and discharge rate of the capacitor (124) depends on the electrical resistance R ｐｈｏｔｏ The device (111) according to any one of claims 2 to 4, which depends on

6. The photoconductive readout circuit (112) comprises at least one amplifier (144) configured to amplify the output signal of the comparator circuit, for the apparatus (111) according to any one of claims 2 to 5.

7. The apparatus includes at least one coupling (146) to at least one evaluation device (142), for the apparatus (111) according to any one of claims 1 to 6.

8. The photosensitive region (118) includes at least one photoconductive material selected from the group consisting of lead sulfide (PbS); lead selenide (PbSe); mercury cadmium telluride (HgCdTe); cadmium sulfide (CdS); cadmium selenide (CdSe); indium antimonide (InSb); indium arsenide (InAs); indium gallium arsenide (InGaAs); extrinsic semiconductors, organic semiconductors, for the apparatus (111) according to any one of claims 1 to 7.

9. The apparatus (111) includes at least one temperature-sensitive element, and the signal of the temperature-sensitive element is used to correct the first output signal of the first electronic circuit, for the apparatus (111) according to claim 1.

10. The second electronic circuit (162) is a frequency mixer, for the apparatus (111) according to claim 1.

11. The apparatus (111) includes at least one third resistor (166) having an irradiation-independent electrical resistance with the same temperature dependence as the photoconductor (114) and the second photoconductor, the third resistor (166) being either a photoconductor darkened so as not to be irradiated or a non-photosensitive resistor, and the apparatus (111) includes at least one third electronic circuit (168) configured to generate a third frequency, the third frequency functioning as a reference frequency, and the reference frequency being used by at least two electronic circuits (162, 168) to generate a frequency difference from the irradiated photoconductor, for the apparatus (111) according to claim 1 or 10.

12. The detector (110) comprises at least one evaluation device (142) configured to determine an output signal of at least one output of the photoconductor readout circuit (112) of the device (111), and the evaluation device (142) evaluates the output signal to determine the electrical resistance R of the photoconductor (114). ｐｈｏｔｏ A detector (110) having a device (111) according to any one of claims 1 to 11, which is configured to determine

13. The detector (110) according to claim 12, wherein the evaluation device (142) is configured to perform one or more operations from the group consisting of at least one Fourier transform; frequency counting, edge detection, period length measurement.

14. Use of the device (111) according to any one of claims 1 to 13, with reference to a device (111) for the purpose of reading at least one photoconductor. The device (111) has an electrical resistance R that depends on the irradiation (116) of the photosensitive region (118) of a photoconductor (114). ｐｈｏｔｏ at least one photoconductor configured to exhibit, as shown, At least one photoconductor readout circuit (112), wherein the photoconductor readout circuit (112) determines the electrical resistance R of the photoconductor (114) ｐｈｏｔｏ and has at least one bias voltage source (152) configured to apply at least one modulation bias voltage to the photoconductor (114), and the photoconductor has one or more of at least one PbS sensor, at least one PbSe sensor, or at least one pixelated sensor array including a plurality of pixels each including at least one PbS or PbSe sensor, and has at least one photoconductor readout circuit (112).

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