Apparatus, method, and program

Abstract

This apparatus comprises an acquiring unit that acquires a response waveform output from a device in response to an input signal, and an identifying unit that identifies parameters of an exponential function that approximates the response waveform, wherein: the identifying unit identifies the parameters of the exponential function by means of parameters calculated by linearly approximating a relationship between the logarithm of the signal value of the response waveform and time; and the identifying unit calculates parameters a and b by fitting the logarithm Log (f) of the signal value f of the response waveform and time t by means of the least squares method using the relational expression Log (f)=a-bt, and identifies a parameter A and a parameter T of the exponential function f=A·exp(-t / T) as A=EXP(a) and T=1 / b.

Description

Apparatus, method and program

[0001] The present invention relates to an apparatus, a method, and a program.

[0002] Patent Document 1 and the like state that "noise is reduced by averaging the digital voltage signal output by the ADC circuit 5" (paragraph 0069 of Patent Document 1). [Prior art documents] [Patent documents] [Patent Document 1] JP 2022-102462 A [Patent Document 2] CN 114670959 A General disclosure

[0003] In a first aspect of the present invention, an apparatus is provided, comprising: an acquisition unit that acquires a response waveform output from a device in response to an input signal; and an identification unit that identifies parameters of an exponential function that approximates the response waveform.

[0004] In the above-described device, the specifying unit may specify a parameter of the exponential function using a parameter calculated by linearly approximating the relationship between the logarithm of the signal value of the response waveform and time.

[0005] In the above-described device, the identification unit may calculate parameters a and b by fitting the logarithm Log(f) of the signal value f of the response waveform and time t using a relational expression Log(f) = a - bt by the least squares method, and identify parameters A and T of the exponential function f = A · exp(-t / T) as A = EXP(a) and T = 1 / b.

[0006] In any of the above devices, the acquisition section may acquire an output signal output from the device in response to the input signal being supplied to the device.

[0007] In the above apparatus, the acquisition section may estimate the response waveform from a comparison result between a series of the output signals output from the device each time the input signal is supplied to the device and different thresholds.

[0008] The above-mentioned device may further include a supply unit that supplies the input signal to the device, and the acquisition unit may detect the timing at which the series of output signals crosses the threshold and the timing at which the series of output signals crosses the threshold again, based on the timing corresponding to the input signal being supplied from the supply unit to the device.

[0009] Any of the above-described devices may further comprise a determining unit that determines whether the device is good or bad based on the exponential function that includes the parameter identified by the identifying unit.

[0010] In the above apparatus, the determining section may determine whether the device is good or bad based on the interval between when the response waveform crosses a reference value and when it crosses the reference value again.

[0011] In any of the above apparatuses, the device may be a light receiving element that outputs an electrical signal in response to an input of an optical signal.

[0012] In a second aspect of the present invention, a method is provided, comprising an acquisition step of acquiring a response waveform output from a device in response to an input signal, and an identification step of identifying parameters of an exponential function that approximates the response waveform.

[0013] In a third aspect of the present invention, there is provided a program that, when executed by a computer, causes the computer to function as an acquisition unit that acquires a response waveform output from a device in response to an input signal, and an identification unit that identifies parameters of an exponential function that approximates the response waveform.

[0014] The above summary of the invention does not list all of the necessary features of the present invention, and subcombinations of these features may also constitute inventions.

[0015] 1 shows a test system 1 according to an embodiment; 2 shows the operation of a test apparatus 200; 3 shows a response waveform estimated by an acquisition unit 203; 4 shows an example of application of a signal generation unit 201, a supply unit 202, and an acquisition unit 203; and 5 shows an example of a computer 1200 in which aspects of the present invention may be embodied in whole or in part.

[0016] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention as claimed. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0017] 1 shows a test system 1 according to an embodiment. The test system 1 includes a device under test (DUT) 100 and a test apparatus 200.

[0018] [1-1. Device Under Test 100] The device under test 100 is an example of a device, and outputs an output signal in response to an input signal. For example, the device under test 100 may be a light-receiving element that outputs an electrical signal in response to an input optical signal. In this embodiment, as an example, the device under test 100 may be a single-photon avalanche diode (SPAD), which may be arranged in an array to form a silicon photomultiplier (SiPM). The device under test 100 may be tested for pass / fail by a test apparatus 200.

[0019] [1-2. Test Apparatus 200] The test apparatus 200 is an example of an apparatus, and may test the device under test 100. The test apparatus 200 may include a signal generating section 201, a supplying section 202, an acquiring section 203, an identifying section 204, and a judging section 205. The test apparatus 200 may further include a power supply section (not shown) that supplies power to the device under test 100.

[0020] [1-2-1. Signal Generating Section 201] The signal generating section 201 generates an input signal to be supplied to the device under test 100. The signal generating section 201 may generate an impulse-shaped input signal and supply it to the supplying section 202. The signal generating section 201 may supply the input signal to the supplying section 202, causing the supplying section 202 to supply the input signal to the device under test 100. In response to supplying the input signal to the device under test 100, the signal generating section 201 may supply an acquisition instruction signal to the acquiring section 203, instructing the acquiring section 203 to acquire an output signal from the device under test 100.

[0021] Supplying Section 202 The supplying section 202 supplies an input signal to the device under test 100. The supplying section 202 may supply the input signal generated by the signal generating section 201 to the device under test 100.

[0022] In the present embodiment, as an example, the supplying section 202 may be a light source such as a laser light source, and may supply an instantaneous optical signal to the device under test 100, which is a light receiving element. Alternatively, the supplying section 202 may be electrically connected to the device under test 100 and supply an electrical signal to the device under test 100. The supplying section 202 may supply an input signal to the device under test 100 once, or may supply the same input signal multiple times.

[0023] [1-2-3. Acquiring Section 203] The acquiring section 203 acquires a response waveform output from the device under test 100 in response to an input signal. The response waveform may be a waveform of an impulse response from the device under test 100, and in this embodiment, as an example, may be a waveform that instantaneously rises from zero to a peak value and then exponentially decays to zero.

[0024] The acquisition section 203 may acquire an output signal output from the device under test 100 in response to an input signal being supplied to the device under test 100, or may acquire an output signal in response to receiving an acquisition instruction signal from the signal generation section 201.

[0025] If the output signal fluctuates slowly and it is possible to sample the signal value at each point in time within the series of output signals to the extent that the response waveform can be estimated, the acquisition unit 203 may estimate the response waveform by connecting the signal values ​​at each sampling timing.

[0026] When the output signal fluctuates sharply and it is not possible to sample the signal value at each time point within the series of output signals to an extent that allows estimation of the response waveform, the acquiring section 203 may estimate the response waveform using the sampling results of the series of output signals output from the device under test 100 multiple times. In this way, the acquiring section 203 can estimate, as the response waveform, the waveform of the signal component that does not contain the noise component among the signal components and noise components included in the series of output signals output from the device under test 100 in response to a single input of the input signal. The acquiring section 203 may estimate the response waveform using a so-called Shmoo plot.

[0027] For example, the acquiring section 203 may estimate a response waveform from a comparison result between a series of output signals output from the device under test 100 and different thresholds each time an input signal is supplied to the device under test 100. In the present embodiment, as an example, the acquiring section 203 may use a timing (also referred to as a reference timing) corresponding to the supply of an input signal from the supplying section 202 to the device under test 100 as a reference, detect the timing at which the series of output signals cross a threshold and the timing at which the series of output signals cross a threshold again, and may detect these timings a reference number of times for each threshold value. In this way, the acquiring section 203 may acquire a Shmoo plot, with the horizontal axis and vertical axis representing time and signal value, respectively, showing the signal value for each elapsed time from the reference timing. In this case, the acquiring section 203 may include a comparator, one input terminal of which may be supplied with the output signal from the device under test 100, and the other input terminal may be applied with a voltage corresponding to the threshold. The reference number may be any number, such as 10 times.

[0028] The timing corresponding to the input signal being supplied to the device under test 100 may be the exact timing at which the input signal is supplied to the device under test 100, or the timing at which a predetermined time has elapsed since the input signal was supplied, or the timing at which the acquisition section 203 receives an acquisition instruction signal, or the timing at which a predetermined time has elapsed since the acquisition instruction signal was received.

[0029] The acquiring section 203 may acquire the Shmoo plot using other techniques. For example, the acquiring section 203 may change the threshold value while sampling a series of output signals output from the device under test 100 at different sampling times based on the reference timing each time an input signal is supplied to the device under test 100, and compare the samples with the threshold value. The acquiring section 203 may detect the timings at which the series of output signals cross the threshold and the timings at which the series of output signals cross the threshold again, based on the threshold value and the sampling time, a reference number of times. As an example, the acquiring section 203 may sample the series of output signals in response to a multi-strobe signal generated at predetermined intervals from the reference timing. In this way, the acquiring section 203 may acquire a Shmoo plot showing signal values ​​for each elapsed time from the reference timing, with the horizontal and vertical axes representing time and signal values, respectively.

[0030] The acquiring unit 203 may estimate a response waveform from the acquired Shmoo plot. In the present embodiment, as an example, each Shmoo plot indicates a signal value of an output signal at each time point, and therefore the acquiring unit 203 may estimate the response waveform by connecting coordinates of high density Shmoo plots. The acquiring unit 203 may supply information indicating the acquired response waveform (as an example, information indicating the signal value at each time point) to the identifying unit 204.

[0031] [1-2-4. Identification Unit 204] The identification unit 204 identifies parameters of an exponential function that approximates the response waveform. The identification unit 204 may identify parameters of an exponential function that approximates the attenuation portion after the peak of the response waveform.

[0032] The determination unit 204 may determine the parameters of the exponential function using parameters calculated by linearly approximating the relationship between the logarithm of the signal value f of the response waveform and time t. The parameters calculated by linearly approximating the relationship between the logarithm of the signal value f and time t may be the slope and intercept of the approximated linear function. For example, the determination unit 204 may calculate the parameters a and b by fitting the logarithm Log(f) of the signal value f of the response waveform and time t using the relational expression Log(f) = a - bt using the least squares method. The determination unit 204 may determine the parameters A and T of the exponential function f = A · exp(-t / T) as A = EXP(a) and T = 1 / b using the calculated parameters a and b. The logarithm may be a natural logarithm, for example.

[0033] The specifying unit 204 may supply the determining unit 205 with an exponential function including the specified parameters, that is, an approximation function of the response function.

[0034] [1-2-5. Judging Section 205] The judging section 205 judges the acceptability of the device under test 100 based on an exponential function including the parameters identified by the identifying section 204, i.e., an approximation function of the response waveform. The judging section 205 may judge the acceptability of the device under test 100 based on the extent of the spread of the response waveform identified from the approximation function, and may judge the acceptability of the device under test 100 based on the interval between when the response waveform crosses a reference value and when it crosses the reference value again. The judging section 205 may calculate the interval from the approximation function. The reference value may be, for example, half the peak value of the response waveform. In this case, the calculated interval may be the so-called half-width. The judging section 205 may judge the acceptability of the device under test 100 based on whether the calculated interval falls within a desired range.

[0035] According to the above-described test apparatus 200, the parameters of the exponential function that approximates the response waveform are identified, and therefore the response waveform is approximated by the exponential function, which allows the response waveform to be approximated with higher accuracy than when approximating the response waveform with other functions.

[0036] Furthermore, since the parameters of the exponential function are determined by parameters calculated by linearly approximating the relationship between the logarithm of the signal value of the response waveform and time, the parameters of the exponential function can be easily determined.

[0037] Furthermore, the logarithm Log(f) of the signal value f of the response waveform and time t are fitted by the least squares method using the relational expression Log(f) = a - bt to calculate the parameters a and b, and the parameters A and T of the exponential function f = A exp(-t / T) are specified as A = EXP(a) and T = 1 / b. Therefore, the parameters A and T can be reliably specified.

[0038] Furthermore, since an output signal output from the device under test 100 is acquired in response to an input signal being supplied to the device under test 100, it is possible to prevent noise (so-called dark pulses) that occurs unrelated to the supply of the input signal from being included in the response waveform.

[0039] Furthermore, since a response waveform is estimated from the results of comparing a series of output signals output from the device under test 100 with different thresholds each time an input signal is supplied to the device under test 100, it is possible to acquire the response waveform even when the response waveform itself is too fast to be acquired directly. Furthermore, since the response waveform is estimated from a series of multiple output signals, it is possible to estimate a response waveform from which noise components contained in each output signal have been removed.

[0040] Furthermore, based on the timing of supplying the input signal to the device under test 100, the timing at which the series of output signals crosses the threshold and the timing at which the series of output signals crosses the threshold again are detected, so that the shape of the response waveform can be estimated based on the timing for each threshold.

[0041] Furthermore, since the device under test 100 is a light receiving element, an approximation formula for the response waveform of the light receiving element can be easily determined.

[0042] Furthermore, since the quality of the device under test 100 is judged based on the approximate function, the device under test 100 can be tested by acquiring the approximate function.

[0043] Furthermore, the pass / fail of the device under test 100 is judged based on the interval between when the value of the output signal output from the device under test 100 crosses the reference value and when it crosses the reference value again, so that the pass / fail of the device under test 100 can be judged based on the degree of spread of the response waveform.

[0044] 2 shows the operation of the test apparatus 200. The test apparatus 200 identifies an approximation function of the response function of the device under test 100 by the processes of steps S101 to S115, and tests the device under test 100.

[0045] In step S101, the acquiring section 203 sets a threshold value to be compared with the output signal output from the device under test 100. Note that steps S101 to S105 (described later) may be repeated a predetermined number of times (also referred to as a default number of times). The default number of times may be any number greater than the reference number of times (i.e., the number of detections for each condition for acquiring a Shmoo plot). The acquiring section 203 may set different values ​​as the threshold value in the process of step S101 that is repeatedly executed the default number of times, or may set the same value as the threshold value in the process of step S101 that is repeatedly executed the default number of times.

[0046] In step S103, the supplying section 202 supplies an input signal to the device under test 100. In response to receiving an input signal from the signal generating section 201, the supplying section 202 may supply the input signal to the device under test 100. In one processing of step S103, the supplying section 202 may supply input signals to multiple devices under test 100 simultaneously, or may supply the same input signal to multiple devices under test 100. In each of the repeatedly executed steps of step S103, the supplying section 202 may supply the same input signal to each device under test 100.

[0047] In step S105, the acquiring section 203 acquires an output signal output from the device under test 100 in response to the input signal supplied to the device under test 100 in step S103. If the input signal is supplied to multiple devices under test 100 in step S103, the acquiring section 203 may acquire an output signal from each device under test 100.

[0048] The acquiring section 203 may acquire signal values ​​at at least one point in time from a series of output signals output from each device under test 100 in response to the supply of an input signal once in step S103. In the present embodiment, as an example, the acquiring section 203 may compare the series of output signals with the threshold set in step S101. The acquiring section 203 may detect, based on a reference timing, timings at which the series of output signals cross a threshold (e.g., timings at which they exceed the threshold) and timings at which they cross the threshold again (e.g., timings at which they fall below the threshold). As a result, the acquiring section 203 may acquire the signal values ​​at the detected timings as the threshold values.

[0049] In step S107, the acquisition unit 203 determines whether the process of step S105 has been repeated a predetermined number of times. If it is determined that the process of step S105 has not been repeated a predetermined number of times (step S107; No), the process may proceed to step S101 described above. If it is determined that the process of step S105 has been repeated a predetermined number of times (step S107; Yes), the process may proceed to step S109.

[0050] In step S109, the acquiring section 203 acquires a response waveform output from the device under test 100 in response to the input signal. The acquiring section 203 may use the acquisition result in step S105 to acquire a Shmoo plot showing signal values ​​for each elapsed time from a reference timing, and may estimate the response waveform by connecting coordinates of high density on the Shmoo plot. If input signals are acquired from multiple devices under test 100 in step S105, the acquiring section 203 may estimate a response waveform for each device under test 100.

[0051] In step S111, the parameter identifying unit 204 identifies parameters of an exponential function that approximates the response waveform. The parameter identifying unit 204 may identify the parameters by approximating the attenuation portion after the peak of the response waveform with an exponential function. The parameter identifying unit 204 may identify the parameters of the exponential function using parameters calculated by linearly approximating the relationship between the logarithm of the signal value f of the response waveform and time t. In the present embodiment, as an example, the parameter identifying unit 204 may calculate parameters a and b by fitting the logarithm Log(f) of the signal value f of the response waveform and time t using the relational expression Log(f) = a - bt using the least squares method, and may identify parameters A and T of the exponential function f = A · exp(-t / T) as A = EXP(a) and T = 1 / b using the calculated parameters a and b. When a response waveform is estimated for each device under test 100 in step S109, the parameter specifying section 204 may specify the parameters of the exponential function for each device under test 100.

[0052] In step S113, the approximate function specifying unit 204 specifies an exponential function including the specified parameters as an approximate function for the decay portion of the response function. The approximate function specifying unit 204 may further specify a linear function as an approximate function for the portion of the response waveform where the signal value instantaneously fluctuates from zero to the peak value.

[0053] In step S115, the judging section 205 judges the pass / fail of the device under test 100 based on the approximation function of the response waveform. As an example, the judging section 205 may judge the pass / fail of the device under test 100 based on the interval from when the response waveform crosses a reference value until when it crosses the reference value again.

[0054] In the above description, the identification unit 204 is described as identifying the parameters A and T of the exponential function f=A·exp(-t / T) from the parameters a and b calculated by approximating the relationship between the logarithm of the signal value f of a single response waveform acquired in step S109 and time t with a linear function of Log(f)=a-bt, but the parameters A and T may be identified by other methods. For example, the identification unit 204 may calculate the parameters a and b of the linear function from each of the multiple response waveforms, and identify the parameters A and T of the exponential function using the average value of the calculated parameter a and the average value of the parameter b. Alternatively, the identification unit 204 may calculate the parameters a and b of the linear function from each of the multiple response waveforms, and identify the parameters A and T of the exponential function using the calculated parameter a. ｅｌｅｍｅｎｔ = Multiple A calculated by EXP(a) ｅｌｅｍｅｎｔ The average value of ｅｌｅｍｅｎｔ = 1 / b ｅｌｅｍｅｎｔ The average value of may be specified as the parameter T. In these cases, the accuracy of the approximation of the response function can be improved. A plurality of response waveforms may be acquired by repeating the processes of steps S101 to S109.

[0055] 3 shows a response waveform estimated by the acquisition unit 203. The horizontal axis in the figure represents time, and the vertical axis represents signal value. In addition, in this figure, each coordinate position is illustrated with dark shading according to the density of the Shmoo plot showing the signal value over time, and the estimated response waveform is represented by connecting the darkest areas.

[0056] 4 shows an application example of the signal generating unit 201, the supplying unit 202, and the acquiring unit 203. Note that this figure shows an example in which multiple single-photon avalanche diodes are each used as a device under test 100. Multiple devices under test 100 may be arranged in an array on a substrate 105 to form a SiPM. Each device under test 100 may receive power from a power supply 208 and may be grounded via a resistor 209 having the same resistance value.

[0057] The supplying section 202 may be a laser light source and may supply the input signal supplied from the signal generating section 201 as an optical signal to each of the plurality of devices under test 100. The acquiring section 203 may acquire an output signal from each device under test 100 in response to receiving an acquisition instruction signal from the signal generating section 201.

[0058] In the above application examples, the signal generating section 201 and the acquiring section 203 may be integrated as a digital module. Alternatively, the signal generating section 201 and the acquiring section 203 may be configured to include separate devices. For example, the signal generating section 201 may be configured to include a function generator. The acquiring section 203 may be configured to include an oscilloscope provided for each device under test 100.

[0059] [5. Modifications] In the above embodiment, the test apparatus 200 has been described as including the signal generating section 201, the supplying section 202, and the judging section 205. However, any of these may be omitted. If the test apparatus 200 does not include the signal generating section 201, the supplying section 202 may supply a predetermined input signal to the device under test 100 and may supply an acquisition instruction signal to the acquiring section 203 in response to the supply of the input signal. If the test apparatus 200 does not include the supplying section 202, the acquiring section 203 may acquire an output signal output from the device under test 100 in response to the input signal being supplied from the external device to the device under test 100, and the acquiring section 203 may acquire the acquisition instruction signal from the external device. Alternatively, the acquiring section 203 may instruct the external device to supply an input signal a predetermined time before the acquisition timing. If the test apparatus 200 does not include the determining section 205, the specifying section 204 may output an approximate function of the specified response waveform.

[0060] Furthermore, the test apparatus 200 has been described as having a single supplying section 202, acquiring section 203, identifying section 204, and judging section 205, but any one of these may be provided for each device under test 100.

[0061] Various embodiments of the present invention may be described with reference to flowcharts and block diagrams, where the blocks may represent (1) stages of a process in which operations are performed or (2) sections of apparatus responsible for performing the operations. Particular stages and sections may be implemented by dedicated circuitry, programmable circuitry provided with computer-readable instructions stored on a computer-readable medium, and / or a processor provided with computer-readable instructions stored on a computer-readable medium. Dedicated circuitry may include digital and / or analog hardware circuitry, and may include integrated circuits (ICs) and / or discrete circuits. Programmable circuitry may include reconfigurable hardware circuitry including logical AND, OR, XOR, NAND, NOR, and other logic operations, flip-flops, registers, memory elements such as field programmable gate arrays (FPGAs), programmable logic arrays (PLAs), and the like.

[0062] A computer-readable medium may include any tangible device capable of storing instructions that are executed by an appropriate device, such that the computer-readable medium having instructions stored thereon comprises an article of manufacture containing instructions that can be executed to create means for performing the operations specified in the flowcharts or block diagrams. Examples of computer-readable media may include electronic, magnetic, optical, electromagnetic, and semiconductor storage media. More specific examples of computer-readable media may include floppy disks, diskettes, hard disks, random access memories (RAMs), read-only memories (ROMs), erasable programmable read-only memories (EPROMs or flash memories), electrically erasable programmable read-only memories (EEPROMs), static random access memories (SRAMs), compact disc read-only memories (CD-ROMs), digital versatile discs (DVDs), Blu-ray (RTM) discs, memory sticks, integrated circuit cards, and the like.

[0063] The computer readable instructions may include either assembler instructions, Instruction Set Architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state-setting data, or source or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk®, JAVA®, C++, etc., and conventional procedural programming languages ​​such as the “C” programming language or similar programming languages.

[0064] The computer-readable instructions may be provided to a processor or programmable circuit of a programmable data processing device, such as a computer, locally or via a wide area network (WAN) such as a local area network (LAN) or the Internet, and the computer-readable instructions may be executed to create means for performing the operations specified in the flowcharts or block diagrams. Here, the computer may be a personal computer (PC), a tablet computer, a smartphone, a workstation, a server computer, a general-purpose computer, a special-purpose computer, or the like, or may be a computer system in which multiple computers are connected. Such a computer system in which multiple computers are connected is also called a distributed computing system, and is a broad definition of computer. In a distributed computing system, multiple computers collectively execute a program by each executing a portion of the program and passing data between the computers as needed during program execution.

[0065] Examples of processors include computer processors, central processing units (CPUs), processing units, microprocessors, digital signal processors, controllers, microcontrollers, etc. A computer may have one processor or multiple processors. In a multiprocessor system with multiple processors, each processor executes a portion of a program and passes data between processors as needed during program execution, allowing the multiple processors to collectively execute the program. For example, in multitasking, each of the multiple processors may execute a portion of each task in small chunks by switching tasks at each time slice. In this case, which portion of a program each processor executes changes dynamically. Which portion of a program each of the multiple processors executes may also be statically determined by multiprocessor-aware programming.

[0066] 5 illustrates an example of a computer 1200 in which aspects of the present invention may be embodied, in whole or in part. Programs installed on the computer 1200 may cause the computer 1200 to function as or perform operations associated with an apparatus or one or more sections of the apparatus according to embodiments of the present invention, and / or to perform a process or steps of a process according to embodiments of the present invention. Such programs may be executed by the CPU 1212 to cause the computer 1200 to perform specific operations associated with some or all of the blocks in the flowcharts and block diagrams described herein.

[0067] A computer 1200 according to this embodiment includes a CPU 1212, a RAM 1214, a graphics controller 1216, and a display device 1218, which are interconnected by a host controller 1210. The computer 1200 also includes input / output units such as a communication interface 1222, a hard disk drive 1224, a DVD-ROM drive 1226, and an IC card drive, which are connected to the host controller 1210 via an input / output controller 1220. The computer also includes legacy input / output units such as a ROM 1230 and a keyboard 1242, which are connected to the input / output controller 1220 via an input / output chip 1240.

[0068] The CPU 1212 operates according to programs stored in the ROM 1230 and the RAM 1214, thereby controlling each unit. The graphics controller 1216 acquires image data generated by the CPU 1212 into a frame buffer or the like provided in the RAM 1214 or into the graphics controller 1216 itself, and causes the image data to be displayed on the display device 1218.

[0069] The communication interface 1222 communicates with other electronic devices via a network. The hard disk drive 1224 stores programs and data used by the CPU 1212 in the computer 1200. The DVD-ROM drive 1226 reads programs or data from the DVD-ROM 1201 and provides the programs or data to the hard disk drive 1224 via the RAM 1214. The IC card drive reads programs and data from an IC card and / or writes programs and data to an IC card.

[0070] The ROM 1230 stores therein a boot program or the like that is executed by the computer 1200 upon activation, and / or programs that depend on the hardware of the computer 1200. The input / output chip 1240 may also connect various input / output units to the input / output controller 1220 via a parallel port, a serial port, a keyboard port, a mouse port, etc.

[0071] The programs are provided by a computer-readable medium such as a DVD-ROM 1201 or an IC card. The programs are read from the computer-readable medium, installed in the hard disk drive 1224, RAM 1214, or ROM 1230, which are also examples of computer-readable media, and executed by the CPU 1212. Information processing described in these programs is read by the computer 1200, and brings about cooperation between the programs and the various types of hardware resources described above. An apparatus or method may be configured by implementing information manipulation or processing in accordance with the use of the computer 1200.

[0072] For example, when communication is performed between the computer 1200 and an external device, the CPU 1212 may execute a communication program loaded into the RAM 1214 and instruct the communication interface 1222 to perform communication processing based on the processing described in the communication program. Under the control of the CPU 1212, the communication interface 1222 reads transmission data stored in a transmission buffer processing area provided in the RAM 1214, the hard disk drive 1224, the DVD-ROM 1201, or a recording medium such as an IC card, and transmits the read transmission data to the network, or writes received data received from the network to a reception buffer processing area or the like provided on the recording medium.

[0073] Furthermore, the CPU 1212 may cause all or a necessary portion of a file or database stored on an external recording medium such as a hard disk drive 1224, a DVD-ROM drive 1226 (DVD-ROM 1201), an IC card, etc. to be read into the RAM 1214, and may perform various types of processing on the data on the RAM 1214. The CPU 1212 then writes back the processed data to the external recording medium.

[0074] Various types of information, such as various types of programs, data, tables, and databases, may be stored on the recording medium and may undergo information processing. The CPU 1212 may perform various types of processing on data read from the RAM 1214, including various types of operations, information processing, conditional judgment, conditional branching, unconditional branching, information search / replacement, etc., as described throughout this disclosure and specified by the instruction sequences of the programs, and write the results back to the RAM 1214. The CPU 1212 may also search for information in a file, database, etc. on the recording medium. For example, if multiple entries each having an attribute value of a first attribute associated with an attribute value of a second attribute are stored on the recording medium, the CPU 1212 may search for an entry that matches a condition specified by the attribute value of the first attribute from among the multiple entries, read the attribute value of the second attribute stored in the entry, and thereby obtain the attribute value of the second attribute associated with the first attribute that satisfies a predetermined condition.

[0075] The above-described programs or software modules may be stored in a computer-readable medium on or near the computer 1200. A recording medium such as a hard disk or RAM provided in a server system connected to a dedicated communication network or the Internet can also be used as a computer-readable medium, thereby providing the programs to the computer 1200 via the network.

[0076] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0077] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and that the processes can be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, this does not mean that the processes must be performed in this order.

[0078] 1 Test system 100 Device under test 105 Board 200 Test equipment 201 Signal generation unit 202 Supply unit 203 Acquisition unit 204 Identification unit 205 Judgment unit 208 Power supply 209 Resistor 1200 Computer 1201 DVD-ROM 1210 Host controller 1212 CPU 1214 RAM 1216 Graphics controller 1218 Display device 1220 Input / output controller 1222 Communication interface 1224 Hard disk drive 1226 DVD-ROM drive 1230 ROM 1240 Input / output chip 1242 Keyboard

Claims

1. An apparatus comprising: an acquisition unit that acquires a response waveform output from a device in response to an input signal; and an identification unit that identifies parameters of an exponential function that approximates the response waveform.

2. The device according to claim 1, wherein the determination unit determines a parameter of the exponential function based on a parameter calculated by linearly approximating the relationship between the logarithm of the signal value of the response waveform and time.

3. The device according to claim 2, wherein the determination unit calculates parameters a and b by fitting the logarithm Log(f) of the signal value f of the response waveform and time t using the relational equation Log(f) = a - bt by the least squares method, and determines parameters A and T of the exponential function f = A · exp(-t / T) as A = EXP(a) and T = 1 / b.

4. The apparatus according to claim 1, wherein the acquisition section acquires an output signal output from the device in response to the input signal being supplied to the device.

5. The apparatus according to claim 4, wherein the acquisition unit estimates the response waveform from a comparison result between a series of the output signals output from the device each time the input signal is supplied to the device and different thresholds.

6. The apparatus according to claim 5, further comprising a supply unit that supplies the input signal to the device, wherein the acquisition unit detects the timing at which the series of output signals crosses the threshold and the timing at which the series of output signals crosses the threshold again, based on the timing corresponding to the input signal being supplied from the supply unit to the device.

7. The apparatus according to claim 1, further comprising a determination unit that determines whether the device is good or bad based on the exponential function including the parameters identified by the identification unit.

8. The apparatus according to claim 7, wherein the judgment section judges the quality of the device based on the interval from when the response waveform crosses a reference value until when it crosses the reference value again.

9. The apparatus according to claim 1, wherein the device is a light receiving element that outputs an electrical signal in response to an input of an optical signal.

10. A method comprising: an acquisition step of acquiring a response waveform output from a device in response to an input signal; and an identification step of identifying parameters of an exponential function that approximates the response waveform.

11. A program which, when executed by a computer, causes the computer to function as an acquisition unit that acquires a response waveform output from a device in response to an input signal, and an identification unit that identifies parameters of an exponential function that approximates the response waveform.

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