Devices and methods for image readout

Abstract

An image readout circuit which includes a mean circuit including circuitry configured to obtain a current output from an image sensor and is further configured to generate a signal representative of a mean of the current output from the image sensor or a signal representative of a total charge of the current output, over a first interval; and a variance circuit including circuitry configured to obtain the current output from the image sensor and is further configured to generate a signal representative of a variance of the current output from the image sensor over the first interval.

Description

[0001] DEVICES AND METHODS FOR IMAGE READOUT

[0002] Field

[0003] This present disclosure generally relates to image readout for X- ray detection and computed tomography .

[0004] Background

[0005] In computed tomography ( CT ) applications , classical indirect conversion front-end integrated circuits ( ICs ) integrate the photocurrent from the photodiode and output the total charge accumulated over a speci fic time period . However, this data does not reveal the spectral content of the received X-ray signal . According to some literature , analyzing the variance in the photocurrent of a photodiode may be an ef fective method for extracting the spectral content of the received X-ray signal .

[0006] Brief Description of the Drawings

[0007] In the drawings , like reference characters generally refer to the same parts throughout the di f ferent views . The drawings are not necessarily to scale , emphasis instead generally being placed upon illustrating the principles of the disclosure . In the following description, various aspects of the disclosure are described with reference to the following drawings , in which :

[0008] FIG . 1 shows a block diagram of an example of a computed tomography apparatus ;

[0009] FIG . 2 shows a block diagram of an example of an image readout circuit according to at least one aspect of the present disclosure ;

[0010] FIG . 3 show a graph of exemplary current output of an image sensor ;

[0011] FIG . 4 shows a block diagram of an example of an image readout circuit according to at least one aspect of the present disclosure ; and FIG . 5 shows a flow diagram of image readout method according to at least one aspect of the present disclosure .

[0012] FIG . 6 shows the circuit level implementation for the variance extraction according to at least one aspect of the present disclosure .

[0013] Description

[0014] The following detailed description refers to the accompanying drawings that show, by way of illustration, speci fic details and aspects in which the disclosure may be practiced . One or more aspects are described in suf ficient detail to enable those skilled in the art to practice the disclosure . Other aspects may be utili zed and structural , logical , and electrical changes may be made without departing from the scope of the disclosure . The various aspects described herein are not necessarily mutually exclusive , as some aspects can be combined with one or more other aspects to form new aspects . Various aspects are described in connection with methods and various aspects are described in connection with devices . However, it may be understood that aspects described in connection with methods may similarly apply to the devices , and vice versa . Throughout the drawings , it should be noted that like reference numbers are used to depict the same or similar elements , features , and structures . Throughout the drawings , it should be noted that proportions are not necessary to scale and that the si ze of features may be emphasi zed for ease of illustration .

[0015] FIG . 1 shows an example of a computed tomography ( CT ) apparatus 100 including image sensors and the image sensor arrangements . In the example of FIG . 1 , an X-ray tube 110 can be configured to continuously emit an X-ray radiation beam 111 having a defined aperture . An X-ray detector 120 can be configured to receive the X-rays . The X-ray detector 120 can include a number of e . g . , 30 ( in one example ) sensor arrangements 122 . The arrangement of X- ray tube 110 and X-ray detector 120 continuously rotates around an inner space 130 that is configured to receive a person, an animal or an obj ect to be examined . The X-ray detector 120 can exhibit a cylinder surface shape reception area that may have a width 123 in the range of 16 mm and a length 624 of about 1000 mm . For example , provided that a photodiode or pixel of the actual detector 120 has a square surface area of 1 mm x 1 mm, 16 photodiodes can be arranged along direction 120 and about 1000 photodiodes are arranged along direction 124 . Each one of the sensor arrangements 122 can include a set of 2 x 4 = 8 image sensors mounted on a ceramic substrate 128 . Also attached to the ceramic substrate 28 is electronic circuitry 129 disposed on a printed circuit board that provides interfacing and connectivity to a computer 140 . While the shown CT apparatus comprises or includes 16 slices of photodiodes in detector 120 disposed one adj acent to the other along direction 123 , a lower or a higher number of slices is also useful . Present manufacturing technology allows also the fabrication of image sensors of a suitable si ze so that even 32 or 256 slices are possible .

[0016] FIG . 2 illustrates a diagram of an image read-out circuit 200 according to one or more exemplary embodiments of this disclosure .

[0017] As depicted, the image read-out circuit 200 includes a mean circuit 210 and a variance circuit 220 . The mean circuit 210 and the variance circuit 220 may be connected in parallel to an image sensor, e . g . , to an output of an image sensor .

[0018] Further, the image readout circuit may include other circuitry, labeled misc . circuit 230 . For example , the misc . circuit 230 may include sample-and-hold circuits , ADCs , or other relevant circuitry used in readout circuits .

[0019] In at least one instance , the image readout circuit 200 can be integrated with, or be a part of , one or more image sensors , such as those found in a CT apparatus ( see e . g . , CT apparatus 100 in FIG . 1 ) . Alternatively, the image read-out circuit 200 may also be implemented independently, separate from the image sensors from which it receives signals .

[0020] In at least one example the mean circuit 210 includes circuitry configured to obtain current output from an image sensor . Further, the mean circuit 210 can include circuitry configured to generate, e.g., using the obtained current output from the image sensor, a signal.

[0021] In one example, the mean circuit 210 generates a signal representative or indicative of a mean or mean value of the current output from the image sensor. That is, the mean circuit 210 can generate or produce a signal which can be representative or indicative of mean or mean value of the amplitude of image sensor output over an interval of time, e.g., referred to as a first interval. For example, it can be the average over an interval determined by a clock signal or a trigger, e.g., from a system, e.g., CT system.

[0022] In other examples, the mean circuit generates a signal representative of a total charge of current output, e.g., over an interval of time (first interval) .

[0023] In at least one example, the variance circuit 220 includes circuitry configured to obtain the current output from the image sensor and is further configured to generate a signal representative or indicative of a variance or variance value of the current output from the image sensor. That is, the variance can be the average variance over a (specific) interval determined by a clock signal or trigger. In other examples, the variance may be produced or extracted continuously and integrated over specific time intervals determined by a clock or trigger, e.g., from a system, e.g., CT system.

[0024] For example, FIG. 3 is an example of graph 300 of a current or current output signal (in amps) vs time (in seconds from an image sensor, e.g., a photosensor / photodector , e.g., a photodiode. Such a current or current output signal can be from an image sensor in an X-ray sensor or CT apparatus using a scintillator where the photodiode has a bandwidth of 20 MHz or larger. The current signal graphed in graph 300 can be input to an image readout circuit such as the image readout circuit 200 of FIG. 2. As shown, the current output signal can be analyzed or thought of as having two parts or aspects . Namely, the current output signal has a high variance part 310 and a low variance part 320 .

[0025] The high variance part 310 in the signal may correspond to or indicate the detection of high-energy X-ray photons , while low variance part 320 corresponds or indicates the presence of low- energy X-rays . The CT apparatus or X-ray sensor detecting these X-rays can include scintillator material which is used for converting received X-ray photons into light photons . These photons can then be captured by an image sensor which subsequently outputs an electrical current signal in response to the received light photons .

[0026] In general , there are fewer high energy X-ray photons detected and more low energy X-ray photons in the use of CT apparatus or X-ray sensor .

[0027] FIG . 4 shows a block diagram of an image readout circuit 400 according to at least one exemplary embodiment of the present disclosure .

[0028] The image readout circuit 400 , like the image readout circuit 300 includes a mean circuit 410 and a variance circuit 420 . Both the mean circuit 410 and the variance circuit 420 can receive as input , current output from an image sensor .

[0029] For example , in cases where the image sensor includes a photodiode ( PD) , its output can be connected or coupled to the inputs of both the mean circuit 410 and the variance circuit 420 . For instance , an anode or cathode terminal of the PD may be connected to the input terminals of the mean circuit 410 and the variance circuit 420 .

[0030] According to at least one example , the image sensor, e . g . , photodiode PD, outputs a current or current signal .

[0031] According to at least one example , the mean circuit 410 is configured to output a signal representative or indicative of the mean of the current signal (image sensor output) inputted to the image readout circuit 400.

[0032] In FIG. 4, the mean circuit 410 can include a first amplifier circuit 412. For instance, the first amplifier circuit or first band-limited circuit 412 is configured to filter the current output obtained or received from the image sensor so as to process only a first frequency portion of the current output from the image sensor / photodiode PD. That is, the current output is filtered so that only a first frequency portion remains which is then further processed. In at least one instance, the first bandlimited circuit 412 processes the first frequency portion by amplifying the first frequency portion of the current output.

[0033] In at least FIG. 4, the first amplifier circuit 412 includes or has an operational amplifier Opl and a capacitor Cfb which is coupled in a feedback loop of the operational amplifier Opl, e.g., arranged between the output 416 and the ( inverting) input 414 of the opamp OP1. The other input (non-inverter input) may be coupled to a reference potential, e.g., ground.

[0034] Further in FIG. 4, the image readout circuit 400 also includes a variance circuit 420. For instance, the variance circuit 420 includes circuitry configured to obtain current output from the image sensor (e.g., photodiode PD) and is further configured to generate a signal representative or indicative of a variance of the current output from the image sensor.

[0035] In at least the example of FIG. 4, the variance circuit 420 includes a second amplifier circuit 422. The second amplifier circuit or second band-limited circuit 422 is configured to filter the current output obtained or received from the image sensor (e.g., photodiode PD) so as to process only a second frequency portion of the current output from the image sensor / photodiode PD. That is, the current output is filtered so that only a second frequency portion remains which is process. The processing of the second frequency portion may include amplifying the second frequency portion of the current output. The variance circuit 420 further includes a non-linear circuit 426, which is coupled to the second amplifier circuit 422, In particular, the variance circuit 420 is arranged or configured so that the input of the non-linear circuit 426 obtains or receives the output from the amplifier circuit 422. The nonlinear circuit 426 can be configured to generate a non-linearly output, e.g., non-linearly process output, from the second bandlimited amplifier 422. In at least one example, the non-linear circuit 426 can be a squaring circuit. The squaring circuit can output a signal, e.g., a current, that is the square of its input, e.g., the amplitude values of the output is the square of the corresponding amplitude values of the input.

[0036] The variance circuit 420 further includes an integrator circuit 428. In at least this example, the integrator circuit 428 is configured to integrate an output of the non-linear circuit 426. The integrator can output a signal, e.g., voltage, that is proportional to the cumulative sum (integral) of the input voltage over time.

[0037] In FIG. 4, the second amplifier circuit 422 can also include an operational amplifier (opamp) Op2. A load or resistive element RL may be coupled between an input and an output of the opamp Op2. Further capacitors, e.g., Cl, C2, and C3 may be arranged with respect to the inputs and outputs of the opamp Op2 as shown.

[0038] For example, the capacitor Cl and the resistor RL filter the signal from the photo diode in order to select only the high frequency portion and also decouple the DC bias level of the Op2 from the Opl . The capacitors C2, C3 and C4 are used to define the AC gain of the amplifier 422. The Op2 can operate as a current conveyor which copies the current lx and ly with two separate terminals to the non-linear circuit 426.

[0039] For the image readout circuit 400, the first frequency portion of the current output of the image sensor can be or include a low frequency portion of the current output and the second frequency portion of the current output can be or include a high frequency portion of the current output from image sensor. In one or more examples, the mean circuit 410 is configured to filter the current signal from the photodiode PD, e.g., filter out the high frequency part which corresponds to part of signal with high variance so that the low frequency part remains and is amplified. The resulting output produced from the mean circuit 410 is a signal representative or indicative of or corresponding to the mean of the current signal inputted to the image readout circuit 400.

[0040] In one or more examples, the variance circuit 420 is configured to filter the current signal from the photodiode PD, e.g., filter out the low frequency part so that the high frequency and high variance portion of the current signal remains and is amplified. The resulting output produced from the variance circuit 420 is a signal representative or indicative of the variance of the current signal inputted to the image readout circuit 400.

[0041] In at least one example, the low variance or low frequency portion of the current signal can correspond to a portion of the current signal that is less than or equal to 1 MHz and the high variance or high frequency portion of the current signal can correspond to a portion of the current signal that is equal to or greater to 1 MHz.

[0042] According to at least one aspect, the mean circuit 210 can have a low input impedance at the low frequency portion, e.g., have an input impedance of at less than [INSERT] at the low frequency portion. Further the mean circuit 210 can have a high input impedance at the high frequency portion, e.g., have an input impedance of at least [INSERT] at the high frequency portion.

[0043] According to at least one aspect, the variance circuit 220 can have a high input impedance at the low frequency portion, e.g., have an input impedance of at least three times higher than the mean circuit 210 at the low frequency portion. Further the variance circuit 220 can have a low input impedance at the high frequency portion, e.g., have an input impedance of less than or equal to one third of the impedance of the mean circuit 210 at the high frequency portion .

[0044] Further, the image readout circuit 400 may include additional circuits or circuitries . As shown in FIG . 4 , the image readout circuit may include more sample-and- hold circuits .

[0045] In particular, a first sample-and-hold circuit 440a can be connected to the output 416 of the mean circuit 410 . The first sample-and-hold circuit 440a is configured to sample and hold the voltage of an analog signal output from the mean circuit 410 .

[0046] Similarly, a second sample-and-hold circuit 440b can be connected to the output 430 of the variance circuit 420 . The second sample- and-hold circuit 440b is configured to sample and hold the voltage of an analog signal output from the variance circuit 410 .

[0047] Each of the first and second sample-and-hold circuits , 440a, 440b, can be implemented, for example , as a switch in series with a capacitor that is coupled to a reference potential , such as ground . The switch can be controlled by a synchroni zation signal that periodically causes it to close . For example , closing the switch of the first sample-and-hold circuit 440a can couple the first sample-and-hold circuit 440a to the mean circuit 410 . Similarly, closing a switch of the second sample-and-hold circuit 440b can couple the second sample-and-hold circuit 440b to the variance circuit 420 . This configuration allows for control of the sampling intervals . Other sample and hold circuits known to one skilled in the art can be used also .

[0048] In example of FIG . 4 , the first and second sample-and-hold circuits 440a and 440b are each coupled to a multiplexer circuit 450 . For instance , the multiplexer circuit 450 is configured to multiplex the signals held in the first and second sample-and- hold circuits 440a and 440b and output a signal combining the outputs from the first and second sample-and-hold circuits 440a and 440b . In FIG. 4, the image readout circuit 400 further includes an analog-to-digital converter (ADC) circuit 460. The ADC circuit can be configured to generate a digital output or digital signal from the output of the multiplexer circuit 450.

[0049] The output from the ADC 460 may be processed by an electronic circuitry which can include one or more other components, modules or circuits, labeled 470. In one case, the 470 may include a computer (e.g., one or more processors executing instructions stored on at least one non-transitory computer readable medium) . In at least one instance, the computer can be configured to generate one or more 2D or 3D representations of an individual or object. For example, if the image readout circuit 400 is incorporated into the CT apparatus 600, the computer may be configured to generate 2D or 3D representations of an individual or object in space 630 from the image information, e.g., from the output of the ADC. Other circuitry or modules may be included to further process the digital output, e.g., before a computer is used to generate a representation.

[0050] Further, in one or more examples, other information may be used and processed, e.g., in addition to the output of the ADC. In one example, the mean circuit may addition produce an output in addition to the mean output (Vmean) at 416.

[0051] For example, the mean circuit 410 may be configured to produce a coarse output 418, DCOARSE • The course may be produce from additional components of the mean circuit 410, such as a clock circuit CLK and circuit 419, which produces an output representing a rough or lower-resolution approximation of an analog signal. The output 418 or DCOARSE may be process and used with the output of the ADC 460 to produce more accurate image representations .

[0052] FIG. 5 shows a method 500 according to at least one exemplary embodiment of the present disclosure. The method 500 includes, at 510, obtaining a current output from an image sensor. The image sensor may be a part of X-ray sensor or CT apparatus system. At 520, the method 500 includes generating, by a mean circuit, a signal representative of a mean of the current output from the image sensor from the obtained current output of the image sensor.

[0053] At 530, the method 500 includes generating, by a variance circuit, a signal representative of a variance of the current output of the image sensor from the obtained current output. In at least one example, aspects of the method 520 and 530 can run parallel, e.g. , concurrently.

[0054] At 540, the method 500 includes generating a digital output signal including mean values and variance values of the current output of the image sensor.

[0055] FIG. 6 shows an example of a circuit arrangement 600 according to at least one exemplary embodiment of the present disclosure. The circuit arrangement 600 can be an aspect or part of image readout circuits disclosed herein. For instance, the circuit arrangement 600 can be one example of the variance circuit 420 of FIG. 4.

[0056] For example, transistors Ml to M4 basically may be a part of or implement components of the amplifier circuit 422 or opamp Op2. M5 to M10 implement the non-linear circuit 426 of FIG. 4. The resistors RBI, RB2, and current sources 10 to 4 can be included for DC biasing.

[0057] The capacitors C5 and C6 can provide AC decoupling. Cl, C2, AND C3, C4 may respectively correspond to capacitors Cl, C2 , C3, and C4 of block or component 420 in FIG. 4.

[0058] The arrangement 600 also includes an integrator or integrator circuit

[0059] 610 which can correspond to the integrator 428 of FIG. 4.

[0060] The following examples pertain to further aspects of this disclosure :

[0061] Example 1 is an image readout circuit which includes: a mean circuit including circuitry configured to obtain a current output from an image sensor and is further configured to generate a signal representative of a mean of the current output from the image sensor or a signal representative of a total charge of the current output , over a first interval ; and a variance circuit comprising circuitry configured to obtain the current output from the image sensor and is further configured to generate a signal representative of a variance of the current output from the image sensor over a second interval , (wherein the first interval can be the same as the second interval )

[0062] Example 2 is the subj ect matter of Example 1 , wherein the mean circuit and the variance circuit are optionally connected in parallel to an output of the image sensor .

[0063] Example 3 is the subj ect matter of Example 1 or 2 , wherein the mean circuit may further include a first band-limited ampli fier configured to filter the current output so as to process first frequency portion of the current output from the image sensor .

[0064] Example 4 is the subj ect matter of Example 3 , wherein to process a first frequency portion of the current output from the image sensor may include to ampli fy the first frequency portion of the current output .

[0065] Example 5 is the subj ect matter of Example 3 or 4 , wherein the variance circuit may further include : a second band-limited ampli fier, wherein the second band-limited ampli fier is configured to filter the current output so as to process only a second frequency portion of the current output from the image sensor, wherein the second frequency portion is di f ferent from the first frequency portion; a non-linear circuit configured to non-linearly process an output of the second band-limited ampli fier ; and an integrator circuit configured to integrate an output of the non-linear circuit .

[0066] Example 6 is the subj ect matter of Example 5 , wherein the second band-limited ampli fier configured to process only a second frequency portion of the current output from the image sensor may include to ampli fy the second frequency portion of the current output from the image sensor . Example 7 is the subj ect matter of Example 5 or 6 , wherein the non-linear circuit may optionally be a squaring circuit configured to generate a square an output of the second bandlimited ampli fier .

[0067] Example 8 is the subj ect matter of any of Examples 5 to 7 , wherein the first frequency portion of the current output may be a low frequency portion and the second frequency portion of the current output may be a high frequency portion, wherein the high frequency portion can be greater in frequency than the low frequency portion .

[0068] Example 9 is the subj ect matter of Example 8 , wherein the low frequency portion may be in a range from about 0 MHz to 1 MHz .

[0069] Example 10 is the subj ect matter of Example 8 or 9 , wherein the high frequency portion can be greater than or equal to about 1 MHz .

[0070] Example 11 is the subj ect matter of any of Examples 8 to 10 , wherein the mean circuit may have an input impedance of less than or equal to one third of the variance circuit at the low frequency portion and may have an input impedance of at least three times of the variance circuit at the high frequency portion .

[0071] Example 12 is the subj ect matter of any of Examples 8 to 11 , wherein the variance circuit may have an input impedance of at least three times of the mean circuit at the low frequency portion and has an input impedance of less than or equal to one third of the mean circuit at the high frequency portion .

[0072] Example 13 is the subj ect matter of any of Examples 1 to 12 , which may further include : a sample and hold circuit configured to hold output from the mean channel circuit and to hold output from the variance channel circuit ; a multiplexer circuit configured to multiplex at least output from the first sample and hold circuit and output from the second sample and hold circuit ; and an analog-to-digital converter (ADC ) configured to generate a digital output from output of the multiplexer circuit . Example 14 is the subj ect matter of any of Examples 1 to 13 , wherein to obtain the current output from the image sensor may optionally include to obtain the current output from an array of photodiodes .

[0073] Example 1A is a method for image readout circuit which includes : obtaining a current output from an image sensor ; generating, by a mean circuit , a signal representative of a mean of the current output from the image sensor or a signal representative of a total charge of current output from the obtained current output of the image sensor, an interval and; generating, by a variance circuit , a signal representative of a variance of the current output of the image sensor from the obtained current output over the interval ; and generating a digital output signal comprising mean values and variance values of the current output of the image sensor .

[0074] Example 2A is the subj ect matter of Example 1A, wherein generating by the mean circuit the signal representative of a mean of the current output from the image sensor may optionally include : filtering the current output from the image sensor to obtain a first frequency portion of the current output , and processing the first frequency portion of the current output .

[0075] Example 3A is the subj ect matter of Example 2A, wherein processing the first frequency portion of the current output may optionally include ampli fying the first frequency portion .

[0076] Example 4A is the subj ect matter of Example 2A or 3A, wherein generating, by the variance circuit , the signal representative of a variance of the current output of the image sensor may optionally include : filtering the current output from the image sensor to obtain a second frequency portion of the current output , processing the second frequency portion of the current output , generating a non-linear output using a non-linear circuit from the processed second frequency portion of the current output , and integrating, with an integrator circuit , output from the non-linear circuit . Example 5A is the subj ect matter of Example 4A, wherein processing the second portion of the current output may optionally include ampli fying the second frequency portion of the current output .

[0077] Example 6A is the subj ect matter of Example 4A or 5A, wherein generating the non-linear output from the processed second frequency portion of the current output may include squaring the output of the processed second frequency portion using a squaring circuit .

[0078] Example 7A is the subj ect matter of any of Examples 4A to 6A, wherein the first frequency portion of the current output may be a low frequency portion and the second frequency portion of the current output may be a high frequency portion, wherein the high frequency portion can be greater in frequency than the low frequency portion .

[0079] Example 8A is the subj ect matter of Example 7A, wherein the low frequency portion can be in a range from about 0 Mhz to about 1 Mhz .

[0080] Example 9A is the subj ect matter of Example 7A or 8A, wherein the high frequency portion can be greater than or equal to about 1 Mhz .

[0081] Example 10A is the subj ect matter of any of Examples 7A to 9A, wherein the mean circuit has can have an input impedance of less than or equal to one third of the variance circuit at the low frequency portion and can have an input impedance of at least three times the variance circuit at the high frequency portion .

[0082] Example 11A is the subj ect matter of any of Examples 7A to 10A, wherein the variance circuit can have an input impedance of at least 3 times the impedance of the mean circuit at the low frequency portion and can have an input impedance of less than or equal to one third of the impedance of the mean circuit at the high frequency portion . Example 12A is the subj ect matter of any of Examples 1A to 11A, wherein generating a digital output signal including mean values and variance values of the current output of the image sensor can optionally include : generating a sampling-and-holding output from the ampli fied the first portion of the current output ; generating a sampling-and-holding output from output from the integrator circuit ; multiplexing the sampling-and-hold outputs ; and generating, using an analog-to-digital converter (ADC ) , digital output from multiplexed sampling-and-hold outputs .

[0083] Example 13A is the subj ect matter of any of Examples 1A to 12A, wherein obtaining the current output from the image sensor may optionally include obtaining the current output from an array of photodiodes .

[0084] Example IB is a computed tomography apparatus including : an X- ray source configured to emit X-ray radiation beams ; an X-ray detector configured to receive emitted radiation from the X-ray, the X-ray detector including an image sensor circuit configured to output current based on the received radiation; an image readout circuit configured to receive the output current from the image sensor circuit of the X-ray detector, the image readout circuit including : a mean circuit including circuitry configured to obtain the output current from an image sensor and is further configured to generate a signal representative of a mean of the current output from the image sensor or a signal representative of a total charge of the current output , over a first interval ; and a variance circuit including circuitry configured to obtain the output current from the image sensor and is further configured to generate a signal representative of a variance of the current output from the image sensor over the first interval ; and at least one processor configured to obtain output from the image readout circuit , wherein the at least one processor is configured to generate a two-dimensional or three-dimensional representation of based on the obtained output from the image readout circuit . Example 2B is the subj ect matter of Example IB, wherein the mean circuit and the variance circuit are optionally connected in parallel to an output of the image sensor .

[0085] Example 3B . The computed tomography apparatus of Example IB or 2B, wherein the mean circuit further may optionally include a first band-limited ampli fier configured to filter the current output so as to process only a first frequency portion of the current output from the image sensor .

[0086] Example 4B is the subj ect matter of Example 3B, wherein to process a first frequency portion of the current output from the image sensor may optionally include to ampli fy the first frequency portion of the current output .

[0087] Example 5B is the subj ect matter of Example 3B or 4B, wherein the variance circuit may further include : a second band-limited ampli fier, wherein the second band-limited ampli fier is configured to filter the current output so as to process only a second frequency portion of the current output from the image sensor, wherein the second frequency portion is di f ferent from the first frequency portion; a non-linear circuit configured to non-linearly process an output of the second band-limited ampli fier ; and an integrator circuit configured to integrate an output of the non-linear circuit .

[0088] Example 6B is the subj ect matter of Example 5B, wherein the second band-limited ampli fier configured to process only a second frequency portion of the current output from the image sensor can optionally include to ampli fy the second frequency portion of the current output from the image sensor .

[0089] Example 7B is the subj ect matter of Example 5B or 6B, wherein the non-linear circuit may optionally be a squaring circuit configured to generate a square an output of the second bandlimited ampli fier .

[0090] Example 8B is the subj ect matter of any of Examples 5B to 7B, wherein the first frequency portion of the current output can be a low frequency portion and the second frequency portion of the current output can be a high frequency portion, wherein the high frequency portion is greater in frequency than the low frequency portion .

[0091] Example 9B is the subj ect matter of Example 8B, wherein the low frequency portion can be in a range from about 0 MHz to 1 MHz .

[0092] Example 10B is the subj ect matter of Example 8B or 9B, wherein the high frequency portion can be greater than or equal to about 1 MHz .

[0093] Example 11B is the subj ect matter of any of Examples 8B to 10B, wherein the mean circuit can have an input impedance of less than or equal to one third of the variance circuit at the low frequency portion and has an input impedance of less than or equal to one third of the mean circuit at the high frequency portion .

[0094] Example 12B is the subj ect matter of any of Examples 8B to 11B, wherein the variance circuit can have an input impedance of at least three times of the mean circuit at the low frequency portion and can have an input impedance of less than or equal to one third of the mean circuit at the high frequency portion .

[0095] Example 13B is the subj ect matter of any of Examples IB to 12B, which may further include a sample and hold circuit configured to hold output from the mean channel circuit and to hold output from the variance channel circuit ; a multiplexer circuit configured to multiplex at least output from the first sample and hold circuit and output from the second sample and hold circuit ; and an analog-to-digital converter (ADC ) configured to generate a digital output from output of the multiplexer circuit .

[0096] Example 14B is the subj ect matter of any of Examples IB to 13B, wherein image sensor circuit may optionally include an array of photodiodes .

[0097] Any of the aspects , examples , and / or embodiments described herein may be suitable or appropriately combined . The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any example or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other examples or designs.

[0098] For the purposes of the present disclosure, the phrase "A and / or B" means (A) , (B) , or (A and B) . For the purposes of the present disclosure, the phrase "A, B, and / or C" means (A) , (B) , (C) , (A and B) , (A and C) , (B and C) , or (A, B, and C) .

[0099] Reference to "one embodiment" or "an embodiment" in the present disclosure means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase "in one embodiment" or "in an embodiment" are not necessarily all referring to the same embodiment. The appearances of the phrase "for example," "in an example," or "in some examples" are not necessarily all referring to the same example.

[0100] The words "plurality" and "multiple" in the description or the claims expressly refer to a quantity greater than one. The terms "group (of) ", "set [of] ", "collection (of) ", "series (of) ", "sequence (of)", "grouping (of)", etc., and the like in the description or in the claims refer to a quantity equal to or greater than one, i.e. one or more. Any term expressed in plural form that does not expressly state "plurality" or "multiple" likewise refers to a quantity equal to or greater than one.

[0101] The term "connected" can be understood in the sense of a (e.g. mechanical, optical and / or electrical) , e.g. direct or indirect, connection and / or interaction. For example, several elements can be connected together mechanically such that they are physically retained (e.g., a plug connected to a socket) and electrically such that they have an electrically conductive path (e.g., signal paths exist along a communicative chain) .

[0102] As used herein, unless otherwise specified the use of the ordinal adjectives "first", "second", "third" etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner.

[0103] As utilized herein, terms "module", "component," "system," "circuit," "element," "slice," "circuitry,", "IC" and the like are can refer to a set of one or more electronic components, a computer-related entity, hardware, software (e.g., in execution) , and / or firmware. For example, circuitry or a similar term can be a processor, a process running on a processor, a controller, an object, an executable program, a storage device, and / or a computer with a processing device. By way of illustration, an application running on a server and the server can also be circuitry. One or more circuits can reside within the same circuitry, and circuitry can be localized on one computer and / or distributed between two or more computers. A set of elements or a set of other circuits can be described herein, in which the term "set" can be interpreted as "one or more."

[0104] Such electric or electronic circuitry can be operated by a software application or a firmware application executed by one or more processors. The one or more processors can be internal or external to the apparatus and can execute at least a part of the software or firmware application. As yet another example, circuitry can be an apparatus that provides specific functionality through electronic components without mechanical parts; the electronic components can include one or more processors therein to execute executable instructions stored in computer readable storage medium and / or firmware that confer (s) , at least in part, the functionality of the electronic components. As another example, circuitry or similar term can be implemented in hardware such as application specific integrated circuit (ASIC) , programmable gate array (PGA) , discrete digital circuits, etc.) or in a combination of hardware and software (e.g., a software model executed by a corresponding processor) .

[0105] The term "semiconductor substrate" can mean any construction comprising semiconductor material, for example, a silicon substrate with or without an epitaxial layer, a silicon-on- insulator substrate containing a buried insulator layer, or a substrate with a silicon germanium layer .

[0106] A lateral direction is understood to mean a direction that runs , in particular, parallel to a main extension surface of the component , in particular of a layer . A vertical direction is understood to mean a direction that is oriented, in particular, perpendicular to the main extension surface of the component and / or layer . The vertical direction and the lateral direction are approximately orthogonal to each other .

[0107] Further, spatially relative terms , such as "beneath, " "below, " " lower, " " above , " "upper" and the like , may be used herein for ease of description to describe one element or feature ' s relationship to another element ( s ) or feature ( s ) as illustrated in the figures . The spatially relative terms are intended to encompass di f ferent orientations of the device in use or operation in addition to the orientation depicted in the figures . The apparatus may be otherwise oriented ( rotated 90 degrees or at other orientations ) and the spatially relative descriptors used herein may likewise be interpreted accordingly .

[0108] The term "data" as used herein may be understood to include information in any suitable analog or digital form, e . g . , provided as a file , a portion of a file, a set of files , a signal or stream, a portion of a signal or stream, a set of signals or streams , and the like . Further, the term "data" may also be used to mean a reference to information, e . g . , in form of a pointer . The term data, however, is not limited to the aforementioned examples and may take various forms and represent any information as understood in the art .

[0109] As used herein, a signal that is " indicative of" a value or other information may be a digital or analog signal that encodes or otherwise communicates the value or other information in a manner that can be decoded by and / or cause a responsive action in a component receiving the signal . The signal may be stored or buf fered in computer readable storage medium prior to its receipt by the receiving component and the receiving component may retrieve the signal from the storage medium . Further, a "value" that is " indicative of" some quantity, state , or parameter may be physically embodied as a digital signal , an analog signal , or stored bits that encode or otherwise communicate the value .

[0110] Unless otherwise stated, the words "about" and " substantially" as used herein are to be construed as meaning the normal measuring and / or fabrication limitations related to the value or condition which the word "about" or " substantially" modi fies . Unless expressly stated otherwise , the term "embodiment" is used herein to mean an embodiment of the present disclosure .

[0111] As used herein, a signal may be transmitted or conducted through a signal chain in which the signal is processed to change characteristics such as phase , amplitude , frequency, and so on . The signal may be referred to as the same signal even as such characteristics are adapted . In general , so long as a signal continues to encode the same information, the signal may be considered as the same signal . For example , a transmit signal may be considered as referring to the transmit signal in baseband, intermediate , and radio frequencies .

[0112] While the above descriptions and connected figures may depict device components as separate elements , skilled persons will appreciate the various possibilities to combine or integrate discrete features , functions into a single element . Such may include combining two or more components into a single component . Conversely, skilled persons will recogni ze the possibility to separate a single element into two or more discrete elements , such as splitting a single component into two or more separate components .

[0113] It is appreciated that implementations of methods detailed herein are exemplary in nature , and are thus understood as capable of being implemented in a corresponding device . Likewise , it is appreciated that implementations of devices detailed herein are understood as capable of being implemented as a corresponding method . It is thus understood that a device corresponding to a method detailed herein may include one or more components configured to perform each aspect of the related method .

[0114] All acronyms defined in the above description additionally hold in all claims included herein .

[0115] While embodiments of the present disclosure have been described above , it is obvious that further embodiments may be implemented . For example , further embodiments may comprise any subcombination of features recited in the claims or any subcombination of elements described in the examples given above . Accordingly, this spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein .

[0116] While the disclosure has been particularly shown and described with reference to speci fic embodiments , it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims . The scope of the disclosure is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced .

[0117] Reference Numeral List

[0118] 100 computed tomography ( CT ) apparatus

[0119] 110 X-ray tube / X-ray source

[0120] 120 X-ray detector

[0121] 122 sensor arrangements

[0122] 123 width direction

[0123] 128 substrate

[0124] 129 electronic circuitry

[0125] 130 inner space 130

[0126] 140 computer

[0127] 200 image readout circuit

[0128] 210 mean circuit

[0129] 220 variance circuit

[0130] 230 misc circuit

[0131] 300 graph of image sensor current output

[0132] 310 high variance part of current output

[0133] 320 low variance part of current output

[0134] 400 image readout circuit

[0135] 410 mean circuit

[0136] 412 first ampli fier circuit

[0137] 414 input to first ampli fier

[0138] 416 output of first ampli fier

[0139] 418 coarse output

[0140] 419 circuit

[0141] 420 variance circuit

[0142] 422 second ampli fier circuit

[0143] 424 input to variance circuit

[0144] 426 squaring circuit

[0145] 428 integrator circuit

[0146] 430 output of variance circuit

[0147] 440a first sample and hold circuit

[0148] 440b second sample and hold circuit

[0149] 450 multiplexer circuit

[0150] 460 analog-to-digital converter (ADC ) circuit

[0151] 470 electronic circuitry

[0152] 500 , 510-540 , method

[0153] Cfb feedback capacitor

[0154] Cl , C2 , C3 , capacitors for second ampli fier circuit Opl operational amplifier

[0155] 0p2 operational amplifier

Claims

CLAIMS1 . An image readout circuit comprising : a mean circuit comprising circuitry configured to obtain a current output from an image sensor and is further configured to generate a signal representative of a mean of the current output from the image sensor or a signal representative of a total charge of the current output , over a first interval ; and a variance circuit comprising circuitry configured to obtain the current output from the image sensor and is further configured to generate a signal representative of a variance of the current output from the image sensor over the first interval .2 . The image readout circuit of claim 1 , wherein the mean circuit and the variance circuit are connected in parallel to an output of the image sensor .3 . The image readout circuit of claim 2 , wherein the mean circuit further comprises a first band-limited ampli fier configured to filter the current output so as to process a first frequency portion of the current output from the image sensor .4 . The image readout circuit of claim 3 , wherein to process the first frequency portion of the current output from the image sensor comprises to ampli fy the first frequency portion of the current output .5 . The image readout circuit of claim 3 or 4 , wherein the variance circuit further comprises : a second band-limited ampli fier, wherein the second bandlimited ampli fier is configured to filter the current output so as to process only a second frequency portion of the currentoutput from the image sensor, wherein the second frequency portion is di f ferent from the first frequency portion; a non-linear circuit configured to non-linearly process an output of the second band-limited ampli fier ; and an integrator circuit configured to integrate an output of the non-linear circuit .6 . The image readout circuit of claim 5 , wherein the second band-limited ampli fier configured to process only a second frequency portion of the current output from the image sensor comprises to ampli fy the second frequency portion of the current output from the image sensor .7 . The image readout circuit of claim 5 , wherein the non-linear circuit is a squaring circuit configured to generate a square an output of the second band-limited amp 1 i f i e r .8 . The image readout circuit claim 5 , wherein the first frequency portion of the current output is a low frequency portion and the second frequency portion of the current output is a high frequency portion, wherein the high frequency portion is greater in frequency than the low frequency portion .9 . The image readout circuit of claim 8 , wherein the low frequency portion is in a range from about 0 MHz to 1 MHz .10 . The image readout circuit of claim 8 , wherein the high frequency portion is greater than or equal to about 1 MHz .11 . The image readout circuit of claim 8 , wherein the mean circuit has an input impedance of less than or equal to one third of the variance circuit at the low frequencyportion and has an input impedance of at least three times of the variance circuit at the high frequency portion .12 . The image readout circuit of claim 8 , wherein the variance circuit has an input impedance of at least three times of the mean circuit at the low frequency portion and has an input impedance of less than or equal to one third of the mean circuit at the high frequency portion .13 . The image readout circuit of any of claims 1 to 12 , further comprising : a sample and hold circuit configured to hold output from the mean channel circuit and to hold output from the variance channel circuit ; a multiplexer circuit configured to multiplex at least output from the first sample and hold circuit and output from the second sample and hold circuit ; and an analog-to-digital converter (ADC ) configured to generate a digital output from output of the multiplexer circuit .14 . The image readout circuit of any of claims 1 to 12 , wherein to obtain the current output from the image sensor comprises to obtain the current output from an array of photodiodes .15 . A method for image readout circuit , the method comprising : obtaining a current output from an image sensor ; generating, by a mean circuit , a signal representative of a mean of the current output from the image sensor or a signal representative of a total charge of current output from the obtained current output of the image sensor, an interval and; generating, by a variance circuit , a signal representative of a variance of the current output of the image sensor from the obtained current output over the interval ; andgenerating a digital output signal comprising mean values and variance values of the current output of the image sensor .16 . The method of claim 15 , wherein generating by the mean circuit the signal representative of a mean of the current output from the image sensor comprises : filtering the current output from the image sensor to obtain a first frequency portion of the current output , and processing the first frequency portion of the current output .17 . The method of claim 16 , wherein processing the first frequency portion of the current output comprises ampli fying the first frequency portion .18 . The method of claim 16 , wherein generating, by the variance circuit , the signal representative of a variance of the current output of the image sensor comprises : filtering the current output from the image sensor to obtain a second frequency portion of the current output , processing the second frequency portion of the current output , generating a non-linear output using a non-linear circuit from the processed second frequency portion of the current output , and integrating, with an integrator circuit , output from the non-linear circuit .19 . The method of claim 18 , wherein processing the second portion of the current output comprises ampli fying the second frequency portion of the current output .20 . The method of claims 18 , wherein generating the non-linear output from the processed second frequency portion of the current output comprises squaring the output of the processed second frequency portion using a squaring circuit .21 . The method claim 18 , wherein the first frequency portion of the current output comprises a low frequency portion and the second frequency portion of the current output comprises a high frequency portion, wherein the high frequency portion can be greater in frequency than the low frequency portion .22 . The method of claim 21 , wherein the low frequency portion ranges from about / substantially 0 Mhz to about / substantially 1 Mhz .23 . The method of claim 21 , wherein the high frequency portion is greater than or equal to about 1 Mhz .24 . The method of claim 21 , wherein the mean circuit has an input impedance of less than or equal to one third of the variance circuit at the low frequency portion and has an input impedance of at least three times the variance circuit at the high frequency portion .25 . The method of claim 21 , wherein the variance circuit has an input impedance of at least 3 times the impedance of the mean circuit at the low frequency portion and has an input impedance of less than or equal to one third of the impedance of the mean circuit at the high frequency portion .26 . The method of any of 15 to 25 , wherein generating a digital output signal including mean values and variance values of the current output of the image sensor comprises : generating a sampling-and-holding output from the ampli fied the first portion of the current output ; generating a sampling- and-holding output from output from the integrator circuit ; multiplexing the sampling-and-hold outputs ; and generating, using an analog-to-digital converter (ADC ) , digital output from multiplexed sampling-and-hold outputs .27 . The method of any of claims 15 to 25 , wherein obtaining the current output from the image sensor comprises obtaining the current output from an array of photodiodes .28 . A computed tomography apparatus comprising : an X-ray source configured to emit X-ray radiation beams ; an X-ray detector configured to receive emitted radiation from the X-ray, the X-ray detector comprising an image sensor circuit configured to output current based on the received radiation; an image readout circuit configured to receive the output current from the image sensor circuit of the X-ray detector, the image readout circuit comprising : a mean circuit comprising circuitry configured to obtain the output current from an image sensor and is further configured to generate a signal representative of a mean of the current output from the image sensor or a signal representative of a total charge of the current output , over a first interval ; and a variance circuit comprising circuitry configured to obtain the output current from the image sensor and is further configured to generate a signal representative of a variance of the current output from the image sensor over the first interval ; and at least one processor configured to obtain output from the image readout circuit , wherein the at least one processor is configured to generate a two-dimensional or three-dimensional representation of based on the obtained output from the image readout circuit .29 . The computed tomography apparatus of claim 28 , wherein the mean circuit and the variance circuit are connected in parallel to an output of the image sensor .30 . The computed tomography apparatus of claim 28 , wherein the mean circuit further comprises a f irst band-limited ampli fier configured to filter the current output so as to process only a first frequency portion of the current output from the image sensor .31 . The computed tomography apparatus of claim 30 , wherein to process a first frequency portion of the current output from the image sensor comprises to ampli fy the first frequency portion of the current output .32 . The computed tomography apparatus of claim 30 , wherein the variance circuit further comprises : a second band-limited ampli fier, wherein the second bandlimited ampli fier is configured to filter the current output so as to process only a second frequency portion of the current output from the image sensor, wherein the second frequency portion is di f ferent from the first frequency portion; a non-linear circuit configured to non-linearly process an output of the second band-limited ampli fier ; and an integrator circuit configured to integrate an output of the non-linear circuit .33 . The computed tomography apparatus of claim 32 , wherein the second band-limited ampli fier configured to process only a second frequency portion of the current output from the image sensor comprises to ampli fy the second frequency portion of the current output from the image sensor .34 . The computed tomography apparatus of claim 32 , wherein the non-linear circuit comprises a squaring circuit configured to generate a square an output of the second bandlimited ampli fier .35 . The computed tomography apparatus of claim 32 , wherein the first frequency portion of the current output comprises a low frequency portion and the second frequency portion of the current output comprises a high frequency portion,wherein the high frequency portion is greater in frequency than the low frequency portion .36 . The computed tomography apparatus of claim 35 , wherein the low frequency portion ranges from about / substantially 0 MHz to about / substantially 1 MHz .37 . The computed tomography apparatus of claim 35 , wherein the high frequency portion is greater than or equal to about 1 MHz .38 . The computed tomography apparatus of claim 35 , wherein the mean circuit has an input impedance of less than or equal to one third of the variance circuit at the low frequency portion and has an input impedance of less than or equal to one third of the mean circuit at the high frequency portion .39 . The computed tomography apparatus of claim 35 , wherein the variance circuit has an input impedance of at least three times of the mean circuit at the low frequency portion and has an input impedance of less than or equal to one third of the mean circuit at the high frequency portion .40 . The computed tomography apparatus of any of claims 28 to 39 , further comprising : a sample and hold circuit configured to hold output from the mean channel circuit and to hold output from the variance channel circuit ; a multiplexer circuit configured to multiplex at least output from the first sample and hold circuit and output from the second sample and hold circuit ; and an analog-to-digital converter (ADC ) configured to generate a digital output from output of the multiplexer circuit .41 . The computed tomography apparatus of any of claims 28 to 39 , wherein image sensor circuit comprises an array of photodiodes .

Images