Dynamic range extension of SPAD-based devices

Abstract

A radiation-sensitive device is disclosed. The device includes multiple single-photon avalanche diodes (SPADs) and circuitry configured to adapt the readout rates of the multiple SPADs to the intensity of incident radiation. A correlated method for increasing the dynamic range of a radiation-sensitive device including multiple SPADs is also disclosed. This method includes adapting the readout rates of the multiple SPADs to the intensity of incident radiation.

Description

Technical Field

[0001] This disclosure pertains to the field of SPAD-based devices for measurements requiring a large dynamic range, such as point-of-care testing, electronic nose applications, and ambient radiation sensing. Background Technology

[0002] In the field of luminescent and fluorescent radiation sensors, there is a need to detect radiative emissions with a large dynamic range (DR). Such sensors can be used, for example, in point-of-care (PoC) testing, electronic nose (E-nose) type applications, or environmental radiation sensor applications.

[0003] In Proof-of-Concept (PoC) applications, the presence of biological or chemical substances in fluids or air can be detected through their interaction with complementary substances, potentially resulting in chemiluminescence or fluorescence emission. The level of emitted radiation can dynamically vary between extremely low and extremely high levels. To achieve complete signal capture, radiation sensors suitable for this application must exhibit a very high dynamic range.

[0004] A photon counter based on a single-photon avalanche diode (SPAD) provides the ability to detect very low levels of radiation by counting individual photons. The lowest level of detectable signal may be limited by noise due to the dark count rate (DCR). The highest level of detectable signal may be limited by the speed of the SPAD diode itself, the capacity of the counter associated with the SPAD, and / or the capabilities of the associated circuitry. In some applications, this can limit the dynamic range of SPAD-based sensors.

[0005] Some sensor implementations may include a large number of SPADs to improve the signal-to-noise ratio at low radiation levels. However, such a large number of SPADs may lead to an increase in associated circuitry, potentially further limiting the achievable dynamic range.

[0006] In other prior art sensor implementations, different SPAD regions can be used in combination with one or more pinholes within a single device to adjust the intensity of radiation incident on different SPAD regions. For example, stacked pinholes with displacement holes in a black medium can be implemented to reduce the intensity of incident radiation. Sensors implementing such a solution may be large, may require additional components, and may exhibit a relatively poor signal-to-noise ratio.

[0007] Therefore, there is a need to provide a radiation sensor with a large dynamic range suitable for PoC testing or electronic nose applications without compromising the signal-to-noise ratio, or without requiring additional components or significantly increasing the device size.

[0008] Therefore, the purpose of at least one embodiment of at least one aspect of this disclosure is to eliminate or at least mitigate at least one of the aforementioned disadvantages of the prior art. Summary of the Invention

[0009] This disclosure belongs to the field of SPAD-based devices, and specifically relates to SPAD-based devices having a large dynamic range suitable for point-of-care testing, electronic nose applications, and environmental radiation sensing applications.

[0010] According to a first aspect of this disclosure, a radiation-sensitive device is provided, comprising a plurality of single-photon avalanche diodes (SPADs) and circuitry configured to adapt the readout rate of the plurality of SPADs to the intensity of incident radiation.

[0011] Advantageously, by adapting the readout rate, the amount of time a given SPAD can be used to detect photon impacts can be correspondingly adapted. Since each SPAD can only record a single photon impact event between each readout cycle, a relatively long readout time, for example, during relatively high-intensity incident radiation, can result in a large number of SPADs failing to record photon impact events, thus limiting the radiation intensity that can be measured. By adapting the readout rate to the intensity of the incident radiation, the number of SPADs that fail to record photon impact events can be minimized, thus increasing the dynamic range of radiation-sensitive devices while maintaining a sufficient signal-to-noise ratio.

[0012] The circuit can be configured to increase the readout rate in response to the intensity of the incident radiation exceeding a threshold. The circuit can also be configured to decrease the readout rate in response to the intensity of the incident radiation being equal to or below a threshold.

[0013] Advantageously, a threshold, such as a predetermined threshold, can define the readout rate required to ensure a sufficient signal-to-noise ratio while also providing increased dynamic range for radiation-sensitive devices. For example, by adapting the readout rate, the limits of measurable radiation intensity are adapted accordingly. By changing the readout rate, the number of SPADs among the multiple SPADs that can be read out within a given readout period can also be changed. Advantageously, defining a threshold allows for a trade-off between the number of available SPADs and the readout rate, thereby effectively compromising the achievable signal-to-noise ratio for dynamic range. It has been recognized that at high levels of incident radiation, there is a sufficient signal-to-noise ratio for a smaller number of SPADs, thus allowing for higher readout rates and consequently, larger dynamic range.

[0014] The threshold can be programmable.

[0015] Advantageously, the threshold can be defined by a user-programmable field, thus enabling a programmable trade-off between dynamic range and achievable signal-to-noise ratio. For example, the device may have one or more programmable registers for defining one or more thresholds.

[0016] In some embodiments, multiple thresholds may be defined. For example, as the intensity of the incident radiation increases from below a first threshold to above a first threshold, the readout rate of at least some of the multiple SPADs may increase from a first rate to a higher second rate. If the intensity of the incident radiation further increases from below a second threshold to above a second threshold, the readout rate of at least some of the multiple SPADs may further increase from a second rate to a higher third rate. It should be understood that if the intensity of the incident radiation decreases to cross a threshold, such as a second or first threshold, then the readout rate of at least some of the multiple SPADs will decrease accordingly.

[0017] The intensity of incident radiation can be determined by reading one or more cycles of at least a portion of multiple SPADs.

[0018] Advantageously, the determination of the intensity of the incident radiation can be used to determine the readout rate, and thus the amount of SPAD that can be read out, for subsequent determination of the intensity of the incident radiation.

[0019] The circuit can be configured to adapt the amount of SPADs among the multiple SPADs read out to the intensity of the incident radiation.

[0020] Advantageously, it allows the reading of the minimum number of SPADs required to achieve the desired signal-to-noise ratio. By minimizing the number of SPADs read, the overall readout rate can be maximized. That is, for a number of SPADs of "Num"... SPAD The SPADs, and the time required to read and reset the latches associated with each SPAD is "T". 1_SPAD The total readout time of multiple SPADs for radiation-sensitive devices is Num. SPAD ×T 1_SPAD Each SPAD can only record one event between each readout cycle. Therefore, the maximum number of photons that each SPAD can read per second is limited to 1 / (Num). SPAD ×T 1_SPAD Subtract any dark count rate contribution. If the intensity of the incident radiation increases such that more than one photon arrives per SPAD during the readout cycle, the recording of photon impact events may be lost. By minimizing the number of SPADs required, the total readout time can be reduced, thus increasing the rate at which any single SPAD can be read out, thereby minimizing the amount of lost photon impacts.

[0021] When the intensity of incident radiation is high, a small number of SPADs can be read to determine that intensity. When the intensity of incident radiation is relatively low, a relatively large number of SPADs can be read to determine that intensity.

[0022] Advantageously, when the intensity of incident radiation is high, a relatively large number of SPADs may not be needed to achieve the desired signal-to-noise ratio, so a relatively small number of SPADs can be used to increase the overall readout rate of the SPADs. The same principle applies to relatively low levels of incident radiation intensity, where a relatively large number of SPADs may be needed to achieve the desired signal-to-noise ratio, so a larger number of SPADs can be used, thereby reducing the overall readout rate of the SPADs.

[0023] Each of the multiple SPADs can have an associated single-bit counter for registering photon impacts.

[0024] Advantageously, by associating only a unit counter with each SPAD, the overall size of the radiation-sensitive device can be minimized. An alternative architecture could employ a multi-bit counter per SPAD to minimize the likelihood of lost photon impact events, which could result in costs associated with a larger overall device area.

[0025] It should be understood that the unit counter can be a latch or a switch. That is, in some embodiments, the unit counter can be one or more circuit components configured to record events (e.g., latch signals). Such a unit counter can be cleared to zero at a rate defined by the readout rate of the SPAD, for example, by resetting.

[0026] Furthermore, the term "readout" will be understood to correspond to the process of determining whether a unit counter has been set, such as when a latch has latched a photon impact event. For example, a readout SPAD array would include circuitry that determines which unit counter associated with the SPAD has counted (e.g., latched) a photon impact event.

[0027] The read rate can depend on the amount of SPAD to be read.

[0028] As mentioned above, the readout rate can be defined as 1 / (Num SPAD ×T 1_SPAD Therefore, a reduction in the amount of SPAD, for example, a reduction in Num SPAD This will increase the overall readout rate. Advantageously, the increase in readout rate will minimize the amount of lost photon impact events.

[0029] The circuit may include a control loop configured to adapt the readout rate and the amount of corresponding SPAD to be read out for one or more subsequent intensity measurements based on one or more measurements of the intensity of the incident radiation.

[0030] Advantageously, the provision of a control loop enables the radiation-sensitive device to dynamically adapt to changing conditions. For example, as the intensity of incident radiation increases, the device can correspondingly adapt the amount of SPAD used and / or the readout rate to ensure accurate measurement of the incident radiation intensity with a sufficient signal-to-noise ratio. Thus, by setting one or more thresholds during startup, the system, including the radiation-sensitive device, subsequently operates with a degree of autonomy, dynamically adapting the readout rate and the corresponding amount of SPAD in response to changes in the intensity of incident radiation.

[0031] According to a second aspect of this disclosure, a method is provided to increase the dynamic range of a radiation-sensitive device comprising a plurality of SPADs, the method comprising adapting the readout rate of the plurality of SPADs to the intensity of incident radiation.

[0032] Advantageously, by adapting the readout rate, the amount of time a SPAD can be used to detect photon impacts can be adapted accordingly. By adapting the readout rate to the intensity of the incident radiation, the number of SPADs that do not record photon impact events can be minimized, thus increasing the dynamic range of radiation-sensitive devices while maintaining a sufficient signal-to-noise ratio.

[0033] The method may include the amount of SPAD among multiple SPADs read out in relation to the intensity of the incident radiation.

[0034] This method may include reading out a small number of SPADs when the intensity of the incident radiation is high, and reading out a relatively large number of SPADs when the intensity of the incident radiation is relatively low.

[0035] According to a third aspect of this disclosure, the use of a radiation-sensitive device according to the first aspect in point-of-care testing or diagnostic applications or electronic nose applications is provided to determine the intensity of luminescence and / or fluorescence from a sample.

[0036] In such point-of-care testing or diagnostic applications or electronic nose applications, there is a particular need to detect radiation emissions with a very large dynamic range, because the level of chemiluminescent or fluorescent radiation emitted by the interaction between biological or chemical substances and complementary substances can vary dynamically between extremely low and extremely high levels.

[0037] According to a fourth aspect of this disclosure, an electronic nose or point-of-care device is provided, including a radiation-sensitive device according to the first aspect, wherein the radiation-sensitive device is configured to determine the intensity of luminescence and / or fluorescence from a sample.

[0038] According to a fourth aspect of this disclosure, a method is provided for using a radiation-sensitive device according to the first aspect in an environmental radiation sensing application.

[0039] Radiation-sensitive devices, implemented in imaging devices such as cameras (e.g., those on smartphones), are used to determine ambient radiation levels. The determined ambient radiation levels can then be used to adapt images captured by the imaging device. Furthermore, the determined ambient radiation levels can be used to configure the imaging device, for example, to control the operation of aperture, flash, etc.

[0040] Radiation-sensitive devices can be used to determine the level of ambient radiation in order to adjust the brightness of a screen or monitor.

[0041] The above description of the invention is merely exemplary and not restrictive. This disclosure includes one or more corresponding aspects, embodiments, or features, either alone or in various combinations, whether specifically stated (including claimed) in such combination or individually. It should be understood that features defined above according to any aspect of this disclosure or features relating to any specific embodiment of this disclosure below may be used alone or in combination with any other defined features in any other aspect or embodiment, or form another aspect or embodiment of this disclosure. Attached Figure Description

[0042] These and other aspects of this disclosure will now be described by way of example only with reference to the accompanying drawings, in which:

[0043] Figure 1 A SPAD-based sensor architecture according to an embodiment of this disclosure is illustrated;

[0044] Figure 2 This is a graph illustrating the amount of SPAD required as a function of the intensity of incident radiation, according to an embodiment of the present invention.

[0045] Figure 3 This is a graph illustrating the amount of SPAD required relative to the associated readout rate of the SPAD according to embodiments of the present invention; and

[0046] Figure 4 A radiation-sensitive device according to an embodiment of the present invention is described. Detailed Implementation

[0047] It has been recognized that in some applications, realizing a large number of SPADs can be beneficial in order to increase the signal-to-noise ratio (SNR) in SPAD-based devices, for example, to accurately detect very low light levels. That is, such devices can realize SPAD arrays comprising hundreds or even thousands of SPADs in order to accurately measure the intensity of incident radiation with sufficient SNR.

[0048] However, the maximum radiation intensity that can be measured from a given SPAD array can be determined by its saturation level.

[0049] Saturation can occur when the photon rate reaches the limit of what a SPAD device can perform detection on its own. For example, the fastest rate at which a SPAD-based device can count photon impact events is determined by the time between the photon impact event and the SPAD's recovery time. The recovery time is the time required for a given SPAD to recover and be ready again. This is referred to in the art as the "dead time." Depending on the specific quenching circuitry implemented, this recovery time can range from tens of nanoseconds to longer. For example, with a dead time of 100 nanoseconds, the maximum theoretical maximum photon count per SPAD would be 10-1 per second. 7 indivual.

[0050] Saturation may occur, either additionally or alternatively, when the circuitry associated with the SPAD (e.g., the read and count circuitry attached to each SPAD) reaches its limit.

[0051] In some examples, each individual SPAD has a dedicated readout bandwidth for registering photon impact events. This results in a physical limitation on the maximum measurable signal for a given architecture.

[0052] For example, in some examples, each SPAD has only a single latch to store photon impact events, such as a unit counter. This latch can be reset on each read. The minimum read interval is the time required to read all of these latches.

[0053] Figure 1 An example of a SPAD-based sensor architecture 100 according to an embodiment of the present invention is described, the sensor architecture 100 including a SPAD and an associated unit counter. Figure 1 The SPAD-based sensor architecture 100 provided in this disclosure provides an example of using a radiation-sensitive device comprising multiple SPADs to determine the intensity of incident radiation, wherein the circuitry is configured to adapt the readout rate of the multiple SPADs to the intensity of the incident radiation.

[0054] It should be understood that Figure 1 These are merely exemplary embodiments and are provided for the purpose of explaining the principles of this disclosure. For example, other embodiments may include substantially larger SPAD arrays and associated unit counters. For instance, some embodiments may include arrays having hundreds or even thousands of SPADs. Furthermore, exemplary devices embodying this disclosure, such as sensors suitable for POC or electronic nose applications, may include multiple SPAD arrays.

[0055] Figure 1 The SPAD-based sensor architecture 100 includes multiple SPADs 105-0 to 105-N. Figure 1Each SPAD has an associated unit counter 110-0 to 110-N. In some embodiments, the unit counters 110-0 to 110-N can be implemented using latches, switches, etc.

[0056] Unit counters 110-0 to 110-N can be coupled to processing circuit 115.

[0057] This processing circuit 115 can be configured to determine the intensity of the incident radiation using at least one of a plurality of SPADs 105-0 to 105-N, wherein the readout rates of the plurality of SPADs 105-0 to 105-N can be adapted to the intensity of the incident radiation.

[0058] The embodiments of this disclosure are based on the following principle: when multiple SPADs are used together to measure light intensity, the (statistical) signal-to-noise ratio is proportional to the square root of the following two parameters: (1) the number of SPADs used in the measurement, and (2) the time window for the measurement.

[0059] Thus, embodiments of this disclosure effectively compromise the excessive SNR at high radiation levels for dynamic range, as described in more detail below. It has been recognized that as the measured radiation intensity (i.e., signal level) increases, the size of the time window that must be measured decreases.

[0060] about Figure 1 The SPAD-based sensor architecture 100, since each SPAD 105-0 to 105-N has only one unit counter 110-0 to 110-N to store photon impact events, this unit counter needs to be reset each time it is read to avoid losing other photon impact events. The readout interval is the time required to read all unit counters 110-0 to 110-N.

[0061] “Num Sp "T" indicates the number of SPADs 10⁵⁻⁰ to 10⁵⁻⁴ required to achieve the desired SNR at minimum radiation intensity. The time required to read out and reset each unit counter 11⁰⁻⁰ to 11⁰⁻⁴ can be expressed in "T". 1_SPAD The value is indicated by "". Given the time required to read and reset each unit counter from 110-0 to 110-N, the total read time is Num. SP ×T 1_SPAD .

[0062] Since each SPAD 105-0 to 105-N can only record one event between each readout cycle, the maximum number of photons that each SPAD 105-0 to 105-N can read per second can be defined as:

[0063]

[0064] in:

[0065] -SPAD MAX(PHOTON / SEC) This corresponds to the number of photons that can be read per second for each SPAD from 10⁵⁻⁰ to 10⁵⁻⁴.

[0066] -Num SP It is the number of SPADs required to achieve the desired SNR at the minimum radiation intensity;

[0067] -T 1_SPAD This refers to the time required to read and reset each unit counter from 110-0 to 110-N; and

[0068] -DCR is the dark count rate.

[0069] If the intensity of the incident radiation increases, such that more than one photon arrives at each SPAD 10⁵⁻⁰ to 10⁵⁻⁴ during the readout period, the record of the photon impact event may be lost.

[0070] In embodiments of the invention, processing circuitry 115 may be configured to detect whether the intensity of the incident radiation has significantly increased above a minimum value, for which all SPADs 105-0 to 105-N are required to achieve the necessary SNR. For example, in some embodiments, processing circuitry may implement a control system and / or control loop.

[0071] For example, processing circuitry 115 can be configured to determine the intensity of incident radiation based on the number of unit counters 110-0 to 110-N set during one or more readout intervals. If processing circuitry 115 determines that the intensity of incident radiation is above a minimum level, the amount of SPADs 105-0 to 105-N that can be read out during that time interval can be adapted, and thus the readout rate of SPADs 105-0 to 105-N can be adapted accordingly.

[0072] For example, if the intensity of the incident radiation is twice the threshold defined by the minimum level required to satisfy the SNR, then the processing circuit 115 can be configured to begin reading only one-quarter of SPAD 105-0 to 105-N during each time interval. That is, when the radiation intensity level is doubled, it has a value equal to Num. Sp / 2 2 A number of SPAD data points might be sufficient.

[0073] In this way, the readout time can be reduced to a quarter, meaning the readout rate can be increased. Consequently, the maximum readable radiation level also increases fourfold.

[0074] In some embodiments, the processing circuitry may be configured to implement multiple such thresholds to correspondingly reduce or increase the number of SPADs and the associated readout rate, as referenced below. Figure 1 More detailed description.

[0075] Figure 1 An exemplary embodiment illustrates a SPAD-based sensor architecture 100, designed such that the number of SPADs 105-0 to 105-N used to measure radiation intensity decreases logarithmically with respect to the magnitude of the radiation level itself. For illustrative purposes only, this is shown as an array comprising 64 SPADs 105-0 to 105-N, each SPAD having an associated unit counter 110-0 to 110-N, such as a latch. It will be understood that in other embodiments, larger or smaller arrays of SPADs 105-0 to 105-N may be implemented. That is, in Figure 1 In the example, “Num Sp For example, the total number of SPAD 105-Ns required for the SPAD-based sensor architecture 100 to achieve the desired SNR is 64. The time T required to read out and reset each unit counter is... 1_SPAD It will be assumed to be 100ns.

[0076] For illustrative purposes, the use case will be described starting with low-intensity incident radiation. By default, the processing circuitry can be configured to read all SPAD 105-0 to 105-N at a first readout rate, as defined in Equation 1. The readout interval, i.e., the time required to read all unit counters, will be 64 × 100 ns = 6.4 μs. Therefore, SPAD 105-N will be read out at a maximum rate of 156,250 times per second.

[0077] If the intensity of the incident radiation increases above a predetermined threshold, the amount of SPAD 105-N readout can be reduced, and the corresponding readout rate can be increased. For example, in some embodiments, the predetermined threshold, which can be programmed by the user, can correspond to the amount of SPAD 105-N detected as photon impact events within a given readout interval. The predetermined threshold can correspond to the amount of SPAD 105-N detected as photon impact events from multiple readout intervals using a process of averaging, extrapolation, and / or interpolation. That is, in some embodiments, the intensity of the incident radiation can be determined by reading out one or more cycles of SPAD 105-N or an active subset of the SPAD, as described in more detail below.

[0078] Processing circuitry 115, configured to read and reset each unit counter 110-0 to 110-N, can determine that a threshold has been reached or exceeded. Processing circuitry 115 can then select a first subset 120 of SPADs 105-0 to 105-N for subsequent measurements of the intensity of the incident radiation. In some embodiments, when the intensity is determined to be below the threshold, the first subset 120 may correspond to one-quarter of the SPADs 105-0 to 105-N used to measure the incident radiation.

[0079] That is, in some embodiments, the processing circuit 115 may include a control loop configured to adapt the readout rate and the associated corresponding SPAD amount to be read for one or more subsequent intensity measurements based on one or more measurements of the intensity of the incident radiation.

[0080] although Figure 1 A first subset 120 comprising adjacent SPADs is depicted, but it should be understood that this is merely for illustrative purposes, and in other embodiments, the SPADs forming the first subset 120, or indeed any subsets 120, 125, may not need to be adjacent to each other. That is, in some embodiments, the SPADs 105-0 to 105-N selected to form subsets 120, 125 may be scattered or otherwise grouped within the array.

[0081] Only a quarter of the SPAD is needed to measure the intensity of incident radiation at the required SNR, and the readout interval becomes 16 × 100 ns = 1.6 μs. That is, the readout interval is also reduced to a quarter, thus increasing the readout rate fourfold to 1 / 1.6 μs = 625,000 reads per second. This increased readout rate directly increases the maximum intensity of incident radiation that can be measured, thereby increasing the dynamic range of the SPAD-based sensor architecture 100.

[0082] continue Figure 1 For example, if the intensity of the incident radiation increases above a second predetermined threshold, the amount of SPAD105-0 to 105-N read out can be further reduced, and the corresponding readout rate can be further increased. In some embodiments, the second threshold, and any of a plurality of thresholds that can actually be implemented, can be programmed by the user.

[0083] Processing circuitry 115, configured to read and reset each unit counter 110-0 to 110-N, can determine that a second threshold has been reached or exceeded. Processing circuitry 115 can then select a second subset 125 of SPADs for subsequent measurements of the intensity of the incident radiation. In some embodiments, the second subset 125 may correspond to one-quarter of the SPADs used in the first subset 120. That is, in some embodiments, the second subset 125 may be formed from a subset of the first subset 120 of SPADs 105-0 to 105-N.

[0084] Only a quarter of the previous amount of SPAD is needed to measure the intensity of incident radiation at the desired SNR, for example, one-sixteenth of the total amount of SPAD. The readout interval becomes 4 × 100 ns = 0.4 μs. That is, the readout interval is further reduced to one-quarter, so the readout rate is further increased to four times, reaching 1 / 0.4 μs = 2,500,000 readouts per second. The further increase in readout rate directly increases the maximum intensity of incident radiation that can be measured, thereby increasing the dynamic range of the SPAD-based sensor architecture 100.

[0085] Thus, when the intensity of the incident radiation is high, a relatively small number of SPADs, such as subset 125, can be read to determine the intensity, while when the intensity of the incident radiation is relatively low, a relatively large number of SPADs, such as subset 120 or all SPADs 105-0 to 105-N, can be read to determine the intensity.

[0086] This operating principle is in Figure 2 and Figure 3 The diagram illustrates this. Figure 2 The amount of SPAD that can be used to measure the incident radiation is shown relative to the intensity of the incident radiation. For illustrative purposes only, the intensity of the incident radiation has been scaled such that a value of "1" represents the minimum value for which all SPADs are needed to achieve the necessary SNR.

[0087] In this example, it can be seen that 1024 SPADs are needed to measure the intensity of the incident radiation with the necessary SNR.

[0088] The x-axis of the graph represents time. As the intensity of the incident radiation increases over time, a first threshold is reached corresponding to the intensity of the incident radiation doubling. At this stage, the processing circuitry of the device embodying the invention will determine that the threshold has been reached or exceeded, and the number of SPADs used for subsequent measurements will be reduced to one-quarter, reaching 256. The corresponding normalized readout rate as a function of the number of SPADs used for measurement is shown. Figure 3This illustrates that when a threshold is exceeded, the read rate also increases fourfold. That is, as the number of SPADs used decreases from 1024 to 256, the read rate increases fourfold, from 0.0156 to 0.625. It should be noted that for illustrative purposes, the read rate has been scaled so that the maximum value is "1", and the actual read rate will depend on the time required to read and reset the latches associated with each SPAD, such as "T" as described above. 1_SPAD ".

[0089] Figure 2 and Figure 3 The description further describes how the number of SPADs and the associated readout rate can be adapted accordingly as the intensity of the incident radiation increases and decreases. In other words, the readout rate of multiple SPADs can be adapted to the intensity of the incident radiation.

[0090] Figure 4 An apparatus 400 including a radiation-sensitive device 420 according to an embodiment of the present invention is depicted. In some example embodiments, the apparatus 400 may be an apparatus for point-of-care (PoC) testing or electronic nose (E-nose) type applications or environmental radiation sensor applications.

[0091] The radiation-sensitive device 420 includes multiple SPADs 405. The multiple SPADs 405 can be arranged as one or more arrays of SPADs 405.

[0092] The radiation-sensitive device 420 also includes multiple unit counters 410, such as latches. Each of the multiple unit counters 410 is associated with a SPAD in a plurality of SPADs 405, as referenced above. Figure 1 As described. SPAD 405 and the associated unit counter 410 can be based on Figure 1 The SPAD-based sensor architecture 100 is arranged accordingly.

[0093] The radiation-sensitive device 420 also includes processing circuitry 415. In some embodiments, processing circuitry 415 may be configured to control a plurality of SPADs 405. For example, in some embodiments, processing circuitry 415 may be configured to control the quenching of SPADs 405, and / or the reset or activation of one or more SPADs 405. Processing circuitry 415 may also be configured to detect one or more faulty SPADs 405.

[0094] In some embodiments, the processing circuit 415 may be configured to read the unit counter 410. In some embodiments, the processing circuit 415 may also be configured to reset the unit counter 410 as needed. The processing circuit 415 may include at least one of a CPU, a microcontroller, a state machine, combinational logic, etc.

[0095] In some embodiments, the processing circuit 415 may be configured to use at least one of a plurality of SPADs 405 to determine the intensity of the incident radiation, wherein the readout rates of the plurality of SPADs are adapted to the intensity of the incident radiation.

[0096] In some embodiments, an aperture, lens, optical cover, grating, or one or more other optical devices may be disposed between SPAD 405 and the radiation source. Such devices may, for example, be configured to focus and / or diffuse radiation incident on SPAD 405. In some embodiments, one or more apertures may be stacked to form a stack of pinholes or displaced apertures. This stack may be disposed on or adjacent to SPAD 405. In such embodiments, at least some of the SPADs 405 of the radiation-sensitive device 420 may experience lower intensity incident radiation than other SPADs. By using such displaced apertures, in conjunction with any of the above-described techniques, the dynamic range of the radiation-sensitive device 420 can be further increased.

[0097] Although this disclosure has been described with reference to specific embodiments as described above, it should be understood that these embodiments are merely illustrative and the claims are not limited to these embodiments. In view of this disclosure, those skilled in the art will be able to make modifications and substitutions, which are considered to fall within the scope of the appended claims. Each feature disclosed or shown in this specification may be incorporated into any embodiment, either alone or in any suitable combination with any other feature disclosed or shown herein.

[0098] List of reference numerals

[0099] 100 SPAD-based sensor architectures

[0100] 105-0……N SPAD

[0101] 110-0……N unit counter

[0102] 115 Processing Circuit

[0103] 120 First Subset

[0104] 125 Second Subset

[0105] 400 device

[0106] 405 SPAD

[0107] 410 Unit Counter

[0108] 415 Processing Circuit

[0109] 420 Radiation-sensitive equipment

Claims

1. A radiation-sensitive device (420), comprising: Multiple single-photon avalanche diodes (SPADs) (10⁵-0…N); as well as Circuit (115) is configured to adapt the readout rate of the plurality of SPADs to the intensity of the incident radiation. The circuit (115) is configured to adapt the amount of SPAD among the plurality of SPADs (105-0...N) read out in relation to the intensity of the incident radiation. The circuit (115) includes a control loop configured to determine, based on one or more measurements of the intensity of the incident radiation, the amount of the corresponding SPAD (105-0…N) to be read out for one or more subsequent intensity measurements, to suit the readout rate of the plurality of SPADs. SPADs (10⁵-0…N) are read out to determine the intensity of the incident radiation, and wherein the amount of SPAD readout for subsequent intensity measurements when the intensity is a first intensity is less than the amount of SPAD readout for subsequent intensity measurements when the intensity is a second intensity, wherein the first intensity is higher than the second intensity. Each of the plurality of SPADs (105-0…N) has an associated unit counter (110-0…N) for registering photon impacts, and the maximum number of photons read per second by each SPAD (105-0…N) is defined as follows: --Equation (1) in: SPAD MAX(PHOTON / SEC) This corresponds to the number of photons read per second for each SPAD (10⁵⁻⁰ to 10⁵⁻⁴). Num SP It is the number of SPADs required to achieve the desired SNR at the minimum radiation intensity; T 1_SPAD This is the time required to read and reset each unit counter (110-0...N); and DCR is the dark count rate.

2. The radiation-sensitive device (420) according to claim 1, wherein the circuit (115) is configured to: -In response to the intensity of the incident radiation exceeding a threshold, the readout rate is increased; - The readout rate is reduced in response to the intensity of the incident radiation being equal to or below the threshold.

3. The radiation-sensitive device (420) according to claim 2, wherein the threshold is programmable.

4. The radiation-sensitive device (420) according to any one of claims 1-3, wherein the intensity of the incident radiation is determined by reading one or more cycles of at least a portion of the plurality of SPADs (105-0...N).

5. The radiation-sensitive device (420) according to any one of claims 1-3, wherein the readout rate depends on the amount of SPAD (105-0...N) to be read out.

6. A method for increasing the dynamic range of a radiation-sensitive device (420) comprising a plurality of single-photon avalanche diodes (SPADs) (10⁵-0…N), the method comprising adapting the readout rate of the plurality of SPADs to the intensity of incident radiation. The amount of SPAD among the plurality of SPADs (10⁵-0…N) read out is adapted to the intensity of the incident radiation. The amount of corresponding SPAD (10⁵-0…N) to be read out for one or more subsequent intensity measurements is determined based on one or more measurements of the intensity of the incident radiation, in order to adapt the readout rate of the plurality of SPADs. SPADs (10⁵-0…N) are read out to determine the intensity of the incident radiation, and wherein the amount of SPAD readout for subsequent intensity measurements when the intensity is a first intensity is less than the amount of SPAD readout for subsequent intensity measurements when the intensity is a second intensity, wherein the first intensity is higher than the second intensity. Each of the plurality of SPADs (105-0…N) has an associated unit counter (110-0…N) for registering photon impacts, and the maximum number of photons read per second by each SPAD (105-0…N) is defined as follows: --Equation (1) in: SPAD MAX(PHOTON / SEC) This corresponds to the number of photons read per second for each SPAD (10⁵⁻⁰ to 10⁵⁻⁴). Num SP It is the number of SPADs required to achieve the desired SNR at the minimum radiation intensity; T 1_SPAD This is the time required to read and reset each unit counter (110-0...N); and DCR is the dark count rate.

7. The use of a radiation-sensitive device (420) according to any one of claims 1 to 5 in a point-of-care testing or diagnostic application or an electronic nose application to determine the intensity of luminescence and / or fluorescence from a sample.

8. An electronic nose or care point device comprising a radiation-sensitive device (420) according to any one of claims 1 to 5, wherein the radiation-sensitive device is configured to determine the intensity of luminescence and / or fluorescence from a sample.

9. The use of a radiation-sensitive device (420) according to any one of claims 1 to 5 in an environmental radiation sensing application.

Images