Device, method, and program

Abstract

A device according to the present disclosure comprises: an irradiation unit that is provided with a light-emitting source and periodically irradiates a sample with light from the light-emitting source to heat the sample; a detection unit that is provided with a detection body facing the sample and detects, via the detection body, the temperature distribution in the sample heated by the irradiation unit; a specifying unit that specifies information about thermal characteristics of the sample on the basis of phase delay calculated by performing lock-in analysis on a temperature response, which is a fluctuation of the temperature distribution detected by the detection unit; and an output unit that is provided with a different detection body from the detection body, detects light irradiated from the light-emitting source via the different detection body, and outputs a reference signal for the lock-in analysis to the specifying unit on the basis of a detection signal of the light.

Description

Device, Method, and Program

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

[0002] The present applicant filed a patent application for an information processing apparatus including an image acquisition unit that acquires a response image showing the time response of a change in temperature distribution in a region including a heated portion irradiated with periodic light on an object, and an output unit that outputs an image of a cross-sectional structure of the object estimated using the response image acquired by the image acquisition unit (Patent Document 1).

[0003] Further, the present applicant filed a patent application for an interface information specifying apparatus including a light source that emits light for heating a sample having a first layer and a second layer overlapping the first layer, an irradiation unit that equalizes the intensity distribution of the light from the light source and irradiates the entire surface on the first layer side of the sample with light, a detection unit that detects the temperature distribution of the surface on the second layer side of the sample, and a specifying unit that specifies information regarding the interface between the first layer and the second layer in the sample based on the temperature distribution detected by the detection unit (Patent Document 2).

[0004] Japanese Patent Application Laid-Open No. 2023-55585 International Publication No. 2023 / 048161

[0005] By the way, there is a case where the thermal characteristics of a sample are evaluated by detecting the temperature response of the sample while periodically heating the sample and performing lock-in analysis. In this evaluation method, when the thermal resistance of the sample is relatively low, the frequency dependence of the phase delay in the response signal of the sample becomes small. As a result, for example, the measurement error becomes large, and it may be difficult to evaluate the thermal characteristics.

[0006] The technology disclosed in this specification aims to enable the evaluation of a sample with relatively low thermal resistance in the evaluation of thermal characteristics using lock-in analysis.

[0007] To this end, the technology disclosed herein is an apparatus comprising: an irradiation unit equipped with a light source that periodically irradiates a sample with light from the light source to heat the sample; a detection unit equipped with a detector facing the sample that detects the temperature distribution in the sample heated by the irradiation unit via the detector; a specification unit that identifies information regarding the thermal characteristics of the sample based on a phase delay calculated by performing a lock-in analysis on the temperature response, which is the fluctuation of the temperature distribution detected by the detection unit; and an output unit equipped with another detector different from the detector that detects light irradiated from the light source via the other detector and outputs a reference signal for the lock-in analysis to the specification unit based on the detection signal of the light. Here, the output unit may output another reference signal to the detection unit that determines the sampling timing of the temperature distribution based on the detection signal of the light. Furthermore, the frequency f of the light source ｓ , the frame rate f of the detection unit ｒ , and the frequency f at which the specific part locks in. ａ This can be expressed by the following equations (1) and (2): f ｓ = f ｒ (m+1 / n) (1) f ｒ =nf ａ (2) m: natural number n: number of samples per period of the lock-in frequency, n≧4 The output unit may also be provided with a beam splitter that divides the light and is located in the optical path from the light source to the sample, and the other detector may detect the light from the light source that has been divided via the beam splitter. The other output unit may also be provided with another light source that irradiates light toward the detector, and outputs a periodic signal to the other light source that causes the other light source to periodically emit light based on the detection signal of the light detected by the other detector. The other light source may also be located within the detection area of ​​the detector together with the sample. The light source and the other light source may also be located on the opposite side of the detector from the sample.

[0008] From another perspective, the technology disclosed herein includes an irradiation unit equipped with a light source that periodically irradiates a sample with light from the light source to heat the sample; a detection unit equipped with a detector facing the sample that detects the temperature distribution in the sample heated by the irradiation unit via the detector; an identification unit that identifies information regarding the thermal properties of the sample based on a phase delay calculated by performing lock-in analysis on the temperature response, which is the fluctuation of the temperature distribution detected by the detection unit; and another detection unit different from the detector that detects the light irradiated from the light source via the other detection unit, and the detection signal of the light The apparatus comprises: an output unit that outputs a reference signal for the lock-in analysis to the specific unit based on a number and outputs another reference signal to the detection unit that determines the sampling timing of the temperature distribution based on the light detection signal; another output unit that provides another light source that irradiates light toward the detection object and outputs a periodic signal to the other light source that causes the other light source to periodically emit light based on the light detection signal detected by the other detection object; and a calibration unit that performs a lock-in analysis on the temperature response and calibrates the phase delay calculated based on the light detection signal emitted from the other light source detected by the detection object.

[0009] From another perspective, the technology disclosed herein is an apparatus comprising: an irradiation unit equipped with a light source that periodically irradiates a sample with light from the light source to heat the sample; a detection unit equipped with a detector facing the sample that detects the temperature distribution in the sample heated by the irradiation unit via the detector; an identification unit that identifies information regarding the thermal characteristics of the sample based on a phase delay calculated by performing a lock-in analysis on the temperature response, which is a fluctuation in the temperature distribution detected by the detection unit; and an output unit equipped with another light source that irradiates light toward the detector, outputs a periodic signal to the other light source that causes the other light source to periodically emit light, and outputs the periodic signal to the identification unit as a reference signal for the lock-in analysis.

[0010] From another perspective, the technology disclosed herein is an apparatus comprising: an irradiation unit equipped with a light source that periodically irradiates a sample with light from the light source to heat the sample; a detection unit equipped with a detector facing the sample that detects the temperature distribution in the sample heated by the irradiation unit via the detector; an identification unit that identifies information regarding the thermal properties of the sample based on a phase delay calculated by performing a lock-in analysis on the temperature response, which is a fluctuation in the temperature distribution detected by the detection unit; and a calibration unit that calibrates the phase delay in the temperature response detected by the detection unit by detecting light irradiated from the light source via another detector different from the detector, and / or by detecting light irradiated from another light source different from the light source onto the detector.

[0011] From another perspective, the technology disclosed herein is an apparatus comprising: an irradiation unit equipped with a light source that periodically irradiates a sample with light from the light source to heat the sample; a detection unit equipped with a detector facing the sample that detects the temperature distribution in the sample heated by the irradiation unit via the detector; an identification unit that identifies information regarding the thermal characteristics of the sample based on a phase delay calculated by performing lock-in analysis on the temperature response, which is a fluctuation in the temperature distribution detected by the detection unit; and an output unit equipped with another detector different from the detector that detects light irradiated from the light source via the other detector and outputs a reference signal to the detection unit that determines the sampling timing of the temperature distribution based on the detection signal of the light.

[0012] From another perspective, the technology disclosed herein is a method comprising the steps of: periodically irradiating a sample with light from a light source to heat the sample; detecting the temperature distribution in the heated sample via a detector; identifying information regarding the thermal properties of the sample based on a phase delay calculated by performing a lock-in analysis on the temperature response, which is a variation in the detected temperature distribution; and detecting light irradiated from the light source via a detector different from the detector, and outputting a reference signal for the lock-in analysis based on the detected light signal.

[0013] From another perspective, the technology disclosed herein is a program that causes a computer to perform the following functions: a function to detect the temperature distribution in a sample heated by periodically irradiating the sample with light from a light source via a detector; a function to receive a reference signal output based on the detection signal of the light detected by another detector different from the detector, where the light irradiated from the light source is detected by the other detector; and a function to identify information regarding the thermal properties of the sample by performing a lock-in analysis on the temperature response, which is the fluctuation of the detected temperature distribution, based on the reference signal and calculating the phase delay.

[0014] The techniques disclosed herein enable the evaluation of samples with relatively low thermal resistance in the evaluation of thermal properties using lock-in analysis.

[0015] This is a schematic diagram of the measuring device according to this embodiment. This is a diagram illustrating the acquired image of infrared thermography. This is a diagram for explaining synchronous undersampling. This is a diagram for explaining phase jitter. This is a diagram illustrating the phase relationship of each signal. This is a diagram showing the measurement results of the frequency dependence of the device-specific phase delay. This is a diagram for explaining the configuration for eliminating the device-specific phase delay. This is a functional configuration diagram of the computer. This is a diagram showing an example of the computer's hardware configuration. This is a diagram showing the measurement results of the thermal diffusivity before and after eliminating the device-specific phase delay. This is a diagram showing the phase delay when measurements were taken at a frequency above the critical frequency. This is a diagram showing the results of the thermal diffusivity mapping of the sample measured as shown in Figure 11. This is a thermal diffusivity histogram in the sample shown in Figure 12. This is a diagram showing the improvement of the measurement limit of thermal diffusivity in the sample thickness direction. This is a schematic diagram of the measuring device according to Modification 1. This is a schematic diagram of the measuring device according to Modification 2.

[0016] The embodiment will be described in detail below with reference to the attached drawings. <Configuration of the measuring device 1> Figure 1 is a schematic diagram of the measuring device 1 according to this embodiment. First, the configuration of the measuring device 1 to which this embodiment is applied will be described with reference to Figure 1.

[0017] As shown in Figure 1, the measuring device 1 to which this embodiment is applied includes a diode laser 10 that functions as a light source for heating the sample 100, a light guide unit 20 that guides the laser light from the diode laser 10 to the sample 100, a support unit 30 that supports the sample 100, an infrared thermograph 40 that acquires infrared radiation from the sample 100, a computer 50 that receives signals from the infrared thermograph 40, a signal generation unit 60 that generates periodic signals and outputs them to the diode laser 10 and the like, a calibration unit 70 that performs calibration of signals acquired from the sample 100, and a transmission unit 80 that transmits electrical signals between each functional component.

[0018] Here, the diode laser 10 and the light guide unit 20 irradiate the entire surface of the sample 100 with light that has a uniform intensity distribution. The diode laser 10 is a surface heating light source. This diode laser 10 outputs so-called multimode diode laser light (e.g., TEM01) in which the transverse mode is not single mode (TEM00). The diode laser 10 is not particularly limited, but for example, a blue diode laser with a wavelength of 455 nm and an output of 5000 mW is used.

[0019] The light guide unit 20 includes a fiber 21 which is a transmission path for transmitting laser light emitted from the diode laser 10, a collimator 23 provided at the tip of the fiber 21 for adjusting the laser light emitted from the fiber 21, a beam splitter 25 which splits the laser light emitted from the collimator 23, and an aperture 27 which focuses the laser light from the beam splitter 25 toward the sample 100.

[0020] Here, fiber 21 is composed of a multimode fiber capable of propagating laser light of different spatial modes in a mixed manner. Inside fiber 21, the laser light emitted from diode laser 10 is divided into meridional rays and skew-ray rays by controlling the incident angle of the laser light emitted from diode laser 10. In addition, the intensity distribution of the irradiated surface is made uniform by the repeated multiple reflections of the laser light emitted from diode laser 10 inside fiber 21.

[0021] The support unit 30 comprises a stage 31 which serves as a base for supporting the sample 100, and a vacuum chamber 33 which houses the stage 31 inside. The infrared thermograph 40 is positioned opposite the sample 100 to the light guide unit 20, and facing the sample 100. This infrared thermograph 40 detects infrared radiation emitted from the sample 100 and the infrared light-emitting diode 73 (described later).

[0022] The signal generation unit 60 includes a first signal generator (function generator) 61 that outputs a periodic signal to the diode laser 10, and a second signal generator 63 that outputs a periodic signal to a computer 50 or the like.

[0023] The calibration unit 70 includes a photodetector 71 that detects laser light emitted from the diode laser 10 and split by the beam splitter 25, and an infrared light-emitting diode (infrared LED) 73 that irradiates infrared light toward the infrared thermograph 40.

[0024] The transmission unit 80 includes a source signal line 81 connecting the first signal generator 61 and the diode laser 10, a trigger signal line 82 connecting the photodetector 71 and the second signal generator 63, a first reference signal line 83 connecting the second signal generator 63 and the infrared light-emitting diode 73, a second reference signal line 85 branching from the first reference signal line 83 and connecting the second signal generator 63 and the computer 50, a frame sync signal line 87 connecting the second signal generator 63 and the infrared thermography 40, and a temperature signal line 89 connecting the infrared thermography 40 and the computer 50.

[0025] In the measuring device 1 configured in this way, the laser light emitted from the diode laser 10 is irradiated onto the sample 100 via the fiber 21, collimator 23, beam splitter 25, and aperture 27. Here, a periodic signal (source signal) is input to the diode laser 10 from the first signal generator 61. As the diode laser 10 periodically emits laser light, the sample 100 is periodically heated.

[0026] Further, the temperature distribution of the periodically heated sample 100 is measured by the infrared thermography 40 on the side opposite to the heating surface in the sample 100, that is, the back surface of the sample 100. The infrared thermography 40 images (measures) a predetermined range including the region periodically heated by the diode laser 10 as an infrared image based on a frame rate at a predetermined interval. Here, a periodic signal (Frame SYNC) is input from the second signal generator 63 to the infrared thermography 40. Also, the temperature distribution data (Temp data), which is the temperature data measured by the infrared thermography 40, is output to the computer 50.

[0027] The computer 50, together with the infrared thermography 40, continuously performs the capture and calculation of the infrared image, and creates an averaged image from the amount of temperature change that changes over time (lock-in method). To explain further, the data obtained by the infrared thermography 40 is processed by the computer 50, and the thermal diffusivity in the thickness direction of the sample 100 is calculated. That is, in the measuring device 1, an evaluation method for evaluating the thermal characteristics of the sample 100 is executed.

[0028] As shown in FIG. 1, in the measuring device 1, two function generators, that is, the first signal generator 61 and the second signal generator 63 are provided. Here, the first signal generator 61 outputs a periodic signal (Source signal, frequency f ｓ ) to the diode laser 10 via the source signal line 81. Also, the second signal generator 63 outputs an alias signal (frequency f ａ ) to the infrared light emitting diode 73 via the first reference signal line 83, and outputs a reference signal (Ref signal, frequency f ａ ) for lock-in measurement to the computer 50 via the second reference signal line 85, and outputs a signal (Frame SYNC, frame rate f ｒ ) used as a frame sync to the infrared thermography 40 via the frame sync signal line 87.

[0029] In recent years, with the increasing performance and miniaturization of semiconductor devices, the rising heat density of these devices has become a concern. This increase in heat density necessitates improved heat dissipation performance. To address this, active development of high thermal conductivity materials for mounting on heat dissipation substrates is underway. In this context, evaluating the thermal conductivity of materials is essential. Furthermore, in recent years, material development has focused on improving thermal conductivity by combining dissimilar materials, which can result in localized and distributed thermal conductivity in heat dissipation substrates. Therefore, methods capable of evaluating distributed thermal conductivity are needed.

[0030] In this embodiment, the sample thickness direction thermal diffusivity distribution evaluation method using lock-in thermography periodic heating involves performing a lock-in analysis on the temperature response of the back surface (the other surface) of the sample 100 when the surface (one side) of the sample 100 is periodically heated with a diode laser 10, and determining the thermal diffusivity from the frequency dependence of the calculated phase lag. To further explain, the phase lag distribution is measured using an infrared thermograph 40. This measurement is performed for multiple heating frequencies, and the thermal diffusivity distribution is determined by analyzing the heating frequency dependence of the phase lag distribution. High-precision measurement achieved by such lock-in signal processing and phase integration by periodic heating, and by fitting each element of the infrared thermograph 40, non-scanning thermal diffusivity mapping measurement becomes possible.

[0031] <Measurement Principle> Next, the measurement principle used in this embodiment, namely the principle of measuring the thermal diffusivity in the thickness direction of a sample by the lock-in thermography periodic heating method, will be explained. In the measurement method in this embodiment, the back surface of the opaque sample 100 is periodically heated, so the temperature wave propagates one-dimensionally to the surface of the sample 100. Therefore, the heat conduction model is calculated by solving the transient one-dimensional heat conduction equation along the thickness direction of the sample 100.

[0032]

[0033] Here, T is the temperature response of sample 100, and t is time. When the back surface of sample 100 is periodically heated by a laser and the front surface is in an adiabatic state, the boundary conditions can be expressed as follows.

[0034]

[0035]

[0036] Here, λ is the thermal conductivity of sample 100, and d is the thickness of the sample. q is the input heat flux of the periodic heating source per unit area, and q o For a square wave input with an offset of 2, it is defined by the following equation.

[0037]

[0038] Here, ω = 2πf is the angular frequency, f is the heating frequency, and q is the heating frequency. o is the intensity amplitude of the heat source per unit area. The temperature response T of the sample 100 induced by q oscillates at the fundamental angular frequency, so the DC temperature T in the quasi-steady state is... ＤＣ (z) and AC temperature It can be expressed as follows using the following equation.

[0039]

[0040] Then, by substituting equation (5) into equation (1), we can obtain the following equation.

[0041]

[0042] Here, Therefore, by solving equation (6) using the boundary conditions in equations (2) and (3), the following equation is obtained as the AC component of the temperature response at the fundamental frequency.

[0043]

[0044] In this case, the amplitude component A and phase component θ of the temperature response can be expressed by the following equations.

[0045]

[0046] The response of equation (7) is measured in the frequency domain, and equation (8) is applied as the temperature response. The amplitude and phase are then determined by digital lock-in signal processing for the temperature parameter. Since the amplitude data has a large noise component due to surface characteristics, only the phase data may be used for evaluation.

[0047] <Images acquired by the infrared thermography 40> Figure 2 is a diagram illustrating the images acquired by the infrared thermography 40. Next, the images acquired by the infrared thermography 40 will be explained with reference to Figures 1 and 2. In this embodiment, the sample 100 and the infrared light-emitting diode 73 are placed within the field of view of the infrared thermography 40, that is, within the detection area of ​​the infrared thermography 40. The infrared light-emitting diode 73 is positioned so that its optical axis aligns with that of the laser light emitted from the collimator 23 of the light guide unit 20.

[0048] Here, as shown in Figure 2, in the acquired image obtained by the infrared thermography 40, a sample region 350 showing infrared radiation emitted from the sample 100 and a diode region 370 showing infrared radiation emitted from the infrared light-emitting diode 73 are arranged within the image region 300. To further explain, in Figure 2, the entire sample region 350 and the diode region 370 are arranged within the image region 300.

[0049] By placing the sample 100 and the infrared light-emitting diode 73 within the field of view of the infrared thermograph 40, it becomes possible to simultaneously measure the phase delay (details described later) acquired from both the sample 100 and the infrared light-emitting diode 73. In the illustrated example, the area of ​​the diode region 370 within the image region 300 is smaller than that of the sample region 350. This makes it possible to secure a larger area for the sample region 350. Therefore, in this configuration, the evaluation accuracy of the sample 100 can be maintained while simultaneously measuring the phase delay θ inherent to the infrared camera. Ｃ (Details will be provided later) can be eliminated.

[0050] <Synchronized Undersampling> Next, synchronous undersampling used in this embodiment will be described. First, when the sample 100 measured using the measurement principle described above has low thermal resistance, the frequency dependence of the phase delay becomes small. As a result, measurement by the measuring device 1 requires measurement up to relatively high frequencies. However, from the phase calculation principle by lock-in signal processing and the Nyquist sampling theorem, the generally measurable frequency is limited to 1 / 4 of the frame rate of the infrared thermography 40 (critical frequency). Therefore, the lower the thermal resistance of the sample, the less frequency dependence of the phase delay can be obtained, and measurement may become impossible.

[0051] In this embodiment, by applying undersampling to the calculation of phase lag based on temperature distribution data acquired by infrared thermography 40, lock-in measurement at frequencies above the critical frequency becomes possible. This enables measurement of thermal diffusivity in low thermal resistance samples.

[0052] In this case, when measuring at frequencies above the critical frequency with undersampling applied, the laser heating frequency (source signal), which is the heat input to the sample 100, and the lock-in frequency (alias signal) are different. Therefore, if the number of samples per period is different (asynchronous correlation), phase jitter may occur. As a result, phase jitter (details described later) may occur, in which the measured phase delay gradually shifts. Therefore, in this embodiment, lock-in measurement is performed by synchronous undersampling, which synchronizes the sampling timing. Here, synchronous answer sampling refers to the case where the number of samples per period of the alias signal is equal to each other and becomes a constant.

[0053] Figure 3 is a diagram illustrating synchronous undersampling. Here, we will explain the frequency relationship in synchronous undersampling while referring to Figure 3. In Figure 3, the horizontal axis represents time t, and the vertical axis represents temperature T. The solid line in Figure 3 represents the alias signal (lock-in frequency), the dashed line represents the source signal (laser heating frequency), and the plots indicate the lock-in sampling timing. In Figure 3, the subscript s represents the source signal (laser heating frequency), r is the frame rate of the infrared thermography 40, and a is the lock-in alias signal (lock-in frequency). In Figure 3, f represents each frequency, and P represents each period. Furthermore, in Figure 3, m is a natural number that determines the frequency relationship, called the undersampling order, and n is the number of samples per period of the lock-in frequency. That is the case.

[0054] As shown in Figure 3, equations (9) and (10) are derived from the relationship of periods. Furthermore, in lock-in measurement using undersampling, it is necessary to measure at frequencies that satisfy equations (9) and (10).

[0055]

[0056]

[0057] Here, we will explain the approach to determining the parameters in equations (9) and (10). First, the frequency f of the source signal. ｓ When m has a certain value, increasing the frame rate f of the infrared thermography 40 ｒ The frame rate of the infrared thermography 40 is f ｒ If is small, the measurement time will be longer to measure the same number of frames. Therefore, m is the frame rate f of the infrared thermography 40 while satisfying equation (9). ｒ A small value (such as 1 or 2) is chosen to maximize the value. Since n represents the number of samples per period, a larger value results in higher accuracy in constructing the waveform of the alias signal.

[0058] Next, we will explain the principle of measuring thermal diffusivity from the phase delay of the alias signal obtained by undersampling lock-in measurement. The temperature response T of the source signal. ｓ and the temperature response T of the alias signal a Each of these can be expressed by the following equations. Here, T ０ ω is the normalized temperature coefficient, ω is the angular frequency, t is time, and θ is the phase lag.

[0059]

[0060]

[0061] Since sampling is performed every (m+1 / n) periods of the source signal, (m+1 / n)P ｓ The temperature response is consistent for each. From this relationship, the following phase lag relationship can be obtained.

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069] Equation (19) shows that the thermal diffusivity in the thickness direction can be determined from the phase delay of the alias signal by lock-in measurement using undersampling. Equation (19) also shows that the thermal diffusivity in the in-plane direction of the sample can be determined by a similar measurement.

[0070] <Phase Jitter> Figure 4 is a diagram illustrating phase jitter. Next, we will explain phase jitter with reference to Figures 1 and 4.

[0071] First, even when measurements are taken at frequencies that satisfy equations (9) and (10) above, phase jitter may still occur. This is because the sampling timing of each frame of the camera does not perfectly match, resulting in asynchronous correlation.

[0072] To explain in more detail, as shown in Figure 4, the theoretical sample response is obtained by the camera's sampling timing in the theoretical frame. On the other hand, in the actual frame, a difference occurs between the theoretical frame and the real frame, i.e., jitter.

[0073] Therefore, in this embodiment, a frame sync is introduced to input the sampling timing of the infrared thermography 40 from an external signal. To explain further, a reference signal (Frame SYNC) is input from the second signal generator 63 to the infrared thermography 40 (see Figure 1). In other words, an external signal that determines the sampling timing of the infrared thermography 40 (see Figure 1) is input from the second signal generator 63. This allows for obtaining the phase difference θ between the actual sample response 100 and the reference signal. Based on this phase difference, the timing of each sample can be synchronized, and phase jitter is eliminated.

[0074] <Device-Specific Phase Delay> Next, we will explain the device-specific phase delay with reference to Figure 1. First, as shown in Figure 1, the measurement device 1 uses a diode laser 10 and an infrared thermograph 40. In this configuration using a diode laser 10 and an infrared thermograph 40, a device-specific phase delay may occur. To explain further, the signal measured using the infrared thermograph 40 may contain a device-specific phase delay. Furthermore, this device-specific phase delay has frequency dependence. As a result, low thermal resistance samples, in particular, which have a small change in the phase delay with respect to frequency, are more susceptible to the influence of this device-specific phase delay. Consequently, errors may occur in the thermal diffusivity calculated from the frequency dependence of the phase delay.

[0075] To explain further, the phase delay θ is actually measured by the lock-in signal processing. ｍ,ｓ The phase lag θ of the sample ｓ This includes not only the phase delay but also the delay amount inherent to the device system. Specifically, the phase delay θ that is actually measured. ｍ,ｓ This is the laser's inherent phase delay θ. Ｌ and the phase delay θ inherent to infrared cameras Ｃ Includes.

[0076]

[0077] In this embodiment, the signal calibration is performed due to the device's inherent phase delay, i.e., the laser's inherent phase delay θ. Ｌ and the phase delay θ inherent to infrared cameras Ｃ This eliminates the phase lag θ of the sample. ｓ The error in the thermal diffusivity calculated from this is reduced.

[0078] < Laser-specific phase delay θ Ｌ > In this embodiment, the laser-specific phase delay θ ＬThis is eliminated as follows. First, in the measuring device 1 shown in Figure 1, a photodetector 71 is provided. Then, a portion of the laser light emitted from the diode laser 10 is detected by the photodetector 71. Here, the rising edge timing of the signal detected by the photodetector 71 is used as the trigger for the reference signal output by the second signal generator 63. This eliminates the laser's inherent phase delay θ. Ｌ This can be eliminated. The reference signal output by the second signal generator 63 performs lock-in measurement with respect to the alias signal f ａ The following will be output.

[0079]

[0080] Furthermore, the signal detected by the photodetector 71 is also used to determine the phase of the periodic signal (Frame SYNC) used for frame syncing to prevent phase jitter in the aforementioned undersampling. Here, the phase of the signal used for frame syncing also needs to be free from the effects of laser-specific phase delay to achieve synchronous undersampling as shown in Figure 3. For this reason, in the illustrated example, the second signal generator 63 uses the signal detected by the photodetector 71 as a trigger to output the signal used for frame syncing to the infrared thermograph 40.

[0081] <Phase delay θ inherent to infrared cameras> Ｃ > In this embodiment, the phase delay θ is inherent to the infrared thermography 40, which is an infrared camera. Ｃ This is eliminated as follows. First, in the measuring device 1 shown in Figure 1, an infrared light-emitting diode 73 is provided. The infrared light emitted from the infrared light-emitting diode 73 is detected by the infrared thermograph 40. Then, the detected signal is processed as a lock-in signal to eliminate the phase delay θ of the infrared light-emitting diode 73. ｍ，ＬＥＤ You can obtain this.

[0082] In this configuration, the phase delay θ of the sample 100 obtained by lock-in signal processing ｍ，ｓ , and the phase delay θ of the infrared light-emitting diode 73 ｍ，ＬＥＤBoth have a phase delay θ inherent to the infrared thermography 40. Ｃ This includes the phase delay θ inherent to infrared cameras. Therefore, by taking the difference between the two, the phase delay θ inherent to infrared cameras can be obtained. Ｃ This eliminates the inherent phase delay θ of the infrared thermography 40, which is eliminated by the infrared light-emitting diode 73. Ｃ This depends on the frequency of the reference signal used for lock-in measurement. Therefore, as shown in Figure 1, the frequency at which the infrared thermography 40 operates is the same as the frequency of the alias signal that is input to the computer 50.

[0083]

[0084]

[0085] <Functions of the second signal generator 63> As described above, undersampling lock-in measurement, which includes the elimination of phase delay specific to the device system, requires signal inputs of three frequencies: the laser heating frequency, the lock-in frequency, and the frame rate of the infrared thermography 40. Therefore, in order to synchronize the timing, the trigger function of the second signal generator 63 is used, as shown in Figure 1.

[0086] In Figure 1, a portion of the laser light split by the beam splitter 25 is detected by the photodetector 71. This detected signal is then input to the second signal generator 63 as a trigger and used as a reference signal in the lock-in signal processing, thereby eliminating the laser's inherent phase delay.

[0087] Furthermore, in Figure 1, the sample 100 and the infrared light-emitting diode 73 are placed within the camera's field of view, and their phase delays are simultaneously measured by the infrared thermograph 40. By taking the difference between the two, the phase delay θ inherent to the infrared thermograph 40 is calculated. Ｃ This eliminates the phase delay θ inherent in this infrared thermography 40. Ｃ The elimination of this can be performed, for example, by the computer 50. To further explain, the phase delay distribution calculation unit 52 of the computer 50 may perform a process to calibrate the device-specific phase delay.

[0088] Furthermore, an infrared light-emitting diode 73 is used to eliminate the phase delay inherent in the infrared thermography 40, but this infrared light-emitting diode 73 has its own inherent phase delay θ. ＬＥＤ This occurs. This infrared light-emitting diode 73 has an inherent phase delay θ. ＬＥＤ For example, a detection element such as a photodetector is used to determine the phase delay θ of the infrared light-emitting diode 73. ＬＥＤ It can be eliminated by actually measuring it.

[0089] <Relationship of Each Phase> Figure 5 is a diagram illustrating the relationship of each signal's phase. Next, the relationship of each signal's phase will be explained with reference to Figures 1 and 5. First, each signal shown in Figure 5 will be explained. The first signal generator 61 outputs a periodic signal SG1. In addition, the diode laser 10 emits laser light upon receiving the periodic signal SG1 from the first signal generator 61. The photodetector 71, which detects the laser light from the diode laser 10, outputs a detection signal SG2. Furthermore, the detection signal SG2 is triggered by the photodetector 71, and the second signal generator 63 outputs a periodic signal SG3.

[0090] Furthermore, upon receiving a periodic signal SG3 from the second signal generator 63, the infrared light-emitting diode 73 emits infrared radiation. The timing at which the infrared light-emitting diode 73 emits infrared radiation is the emission timing signal SG4. In addition, the measurement signal SG5 is a signal obtained by measuring the response of the sample 100, which is periodically heated by receiving laser light from the diode laser 10.

[0091] Here, between the periodic signal SG1 of the first signal generator 61 and the detection signal SG2 of the photodetector 71, there is a laser-specific phase delay θ. Ｌ This occurs. Furthermore, between the periodic signal SG3 of the second signal generator 63 and the emission timing signal SG4 of the infrared light-emitting diode 73, the phase delay θ that is actually measured occurs. ｍ,ＬＥＤ This occurs. Furthermore, between the periodic signal SG3 of the second signal generator 63 and the measurement signal SG5 of the sample 100, the phase delay θ that is actually measured occurs. ｍ,ｓ This will occur.

[0092] <Frequency Dependence of Device-Specific Phase Delay> Figure 6 shows the measurement results of the frequency dependence of the device-specific phase delay. In Figure 6, the horizontal axis represents frequency, and the vertical axis represents the device-specific phase delay. Now, referring to Figure 6, we will explain the measurement results of the frequency dependence of the phase delay specific to the measurement device 1 shown in Figure 1. Here, the laser-specific phase delay θ Ｌ and the phase delay θ inherent to infrared cameras Ｃ Each of these was measured using the apparatus shown in Figures 7(B) and 7(C), which will be described later.

[0093] As shown in Figure 6, it was confirmed that the system-specific phase delay is frequency-dependent. Specifically, the system-specific phase delay increases as the frequency increases. Also, the laser-specific phase delay θ increases as the frequency increases. Ｌ and the phase delay θ inherent to infrared cameras Ｃ Each of these increases. Also, at each frequency, the laser-specific phase delay θ Ｌ The phase delay θ inherent to infrared cameras is greater than the phase delay θ of infrared cameras. Ｃ It's bigger.

[0094] <Configuration for eliminating device-specific phase delay> Figure 7 is a diagram illustrating the configuration for eliminating device-specific phase delay. To further explain, Figure 7(A) is a diagram illustrating device-specific phase delay, Figure 7(B) is a diagram illustrating the measurement method for laser-specific phase delay, and Figure 7(C) is a diagram illustrating the measurement method for infrared camera-specific phase delay.

[0095] In the above, we have described how a phase delay inherent to the device system occurs in the measuring device 1 shown in Figure 1, and a configuration for eliminating this device-specific phase delay. However, a device-specific phase delay can also occur in configurations other than those shown in Figure 1. Furthermore, the configuration for eliminating the device-specific phase delay may also be different from the one shown in Figure 1.

[0096] For example, a phase delay inherent to the device system also occurs in the measuring device 101 shown in Figure 7(A). This measuring device 101 includes a signal generator 110, a diode laser 120 which is a light source, an infrared thermography camera 130 which is an infrared camera, and a lock-in signal processing unit 140 which is a computer that performs lock-in signal processing, in order to measure the sample 100.

[0097] In this measuring device 101, a periodic signal is input from the signal generator 110, and the diode laser 120 emits laser light. This laser light is irradiated onto the sample 100, and the infrared thermograph 130 acquires temperature distribution data. Then, by performing lock-in signal processing on this temperature distribution data, a phase delay θ is applied. ｍ,ｓ This is measured. This measured phase delay θ ｍ,ｓ This is the inherent phase delay θ of the diode laser 120. Ｌ and the phase delay θ inherent to the infrared thermography 130 Ｃ Includes.

[0098] Here, as shown in the configurations in Figures 7(B) and 7(C), the laser-specific phase delay θ Ｌ and the phase delay θ inherent to infrared cameras Ｃ This can also be measured. To further explain, the phase delay θ measured by the measuring device 101 is determined using these measured values. ｍ,ｓ Therefore, the phase delay θ inherent to the diode laser 120 Ｌ and the phase delay θ inherent to the infrared thermography 130 Ｃ It may be excluded.

[0099] In the measuring device 201 shown in Figure 7(B), the phase delay θ inherent to the diode laser 120 is ＬThe measurement is performed. This measuring device 201 comprises a signal generator 210, a diode laser 120 which is a light source, a photodetector 230 which detects light, and a lock-in amplifier 240 which performs lock-in signal processing. In the measuring device 201, a periodic signal is input from the signal generator 210, and the laser light emitted by the diode laser 120 is detected by the photodetector 230. Then, the lock-in signal processing is performed by the lock-in amplifier 240 using this detected signal as a trigger, thereby reducing the laser's inherent phase delay θ Ｌ This is measured.

[0100] Furthermore, in the measuring device 301 shown in Figure 7(C), the phase delay θ is inherent to the infrared thermography 130. Ｃ The following is measured. Specifically, a periodic signal is input from the signal generator 310, and the infrared light-emitting diode 320 emits infrared light. The infrared thermograph 130 acquires temperature distribution data from the infrared light emitted from the infrared light-emitting diode 320. Then, by locking in the signal processing 340, the phase delay θ of the infrared light-emitting diode 320 is determined. ＬＥＤ and the phase delay θ inherent to the infrared thermography 130 Ｃ The phase lag, including this lag, is measured.

[0101] As explained in Figures 1 and 2 above, in the measuring device 1, the phase delay between the sample 100 and the infrared light-emitting diode 73 is measured simultaneously by placing them both within the field of view of the infrared thermograph 40. In this configuration, the area for placing the entire sample 100 within the field of view of the infrared thermograph 40 is limited. Therefore, for example, as shown in Figure 7(C), if the phase delay inherent to the infrared light-emitting diode 320 is measured separately, it becomes unnecessary to place the infrared light-emitting diode 320 within the field of view of the infrared thermograph 130, thus avoiding the limitation on the area of ​​the sample 100.

[0102] <Functional Configuration of Computer 50> Figure 8 is a functional configuration diagram of computer 50. Next, the functional configuration of computer 50 to which this embodiment is applied will be described with reference to Figures 1 and 8. As shown in Figure 8, computer 50 to which this embodiment is applied includes a data acquisition unit 51 that acquires temperature distribution data input from infrared thermography 40 (see Figure 1) and periodic signals input from a second signal generator 63, a phase delay distribution calculation unit 52 that calculates a phase delay distribution based on the temperature distribution data and periodic signals acquired by the data acquisition unit 51, a thermal diffusivity distribution calculation unit 53 that calculates a thermal diffusivity distribution based on the calculated phase delay, and a calculation result display unit 55 that displays the calculated thermal diffusivity result on a liquid crystal display (not shown). The thermal diffusivity distribution calculation unit 53 calculates the thermal diffusivity based on the above measurement principle.

[0103] In this embodiment, the computer 50 calculates the distribution of thermal diffusivity of the sample 100 (see Figure 1) based on the temperature distribution of the sample 100 detected by the infrared thermography 40. More specifically, the computer 50 calculates the distribution of thermal diffusivity in the thickness direction of the sample 100 based on the amplitude of the temperature response, which is the change (fluctuation) in the temperature distribution of the sample 100, and the delay of the response. The computer 50 also displays the calculation results, such as the distribution of thermal diffusivity, on a liquid crystal display (not shown).

[0104] <Hardware Configuration of Computer 50> Figure 9 shows an example of the hardware configuration of computer 50. As shown in Figure 9, computer 50 includes a CPU (Central Processing Unit) 501, which is a calculation means, and a main memory 503 and an HDD (Hard Disk Drive) 505, which are storage means. The CPU 501 executes various programs such as the OS (Operating System) and application software. The main memory 503 is a storage area that stores various programs and data used for their execution. The HDD 505 is a storage area that stores input data for various programs and output data from various programs. These components of computer 50 enable the execution of the various functional configurations described in Figure 8 and above.

[0105] The computer 50 is equipped with a communication interface (communication I / F) 507 for communicating with external devices such as the infrared thermograph 40. In addition, the program executed by the CPU 501 (for example, the program for calculating the thermal diffusivity) can be stored in the main memory 503 in advance, or it can be provided to the CPU 501 from a storage medium such as a CD-ROM, or it can be provided to the CPU 501 via a network (not shown).

[0106] <Measurement Results 1> Figure 10 shows the measurement results of thermal diffusivity before and after eliminating the phase delay inherent to the device system. In Figure 10, the horizontal axis represents frequency and the vertical axis represents phase delay. Next, the measurement results of thermal diffusivity before and after eliminating the phase delay inherent to the device system will be explained with reference to Figure 10.

[0107] In the measurement shown in Figure 10, a 3 mm thick pure copper sample 100 was measured using the measuring device 1 shown in Figure 1. The reference value for the thermal diffusivity of pure copper is 117 mm². ２ The value is / s. As shown in Figure 10, the thermal diffusivity of sample 100, measured before eliminating the phase lag inherent to the apparatus system, was 95.3 mm². ２The value was / s. On the other hand, the thermal diffusivity of sample 100, measured after eliminating the phase lag inherent to the device system, was 121.0 mm². ２ The value was / s. After eliminating the phase lag specific to this device system, the thermal diffusivity value of sample 100 was +3.4%, which matched the reference value with high accuracy.

[0108] <Measurement Results 2> Figure 11 shows the phase delay measured at frequencies above the critical frequency. In Figure 11, the horizontal axis represents frequency and the vertical axis represents phase delay. Next, referring to Figure 11, we will explain the fitting results with the phase delay averaged within sample 100, measured at frequencies above the critical frequency using undersampling lock-in measurement.

[0109] In the measurement shown in Figure 11, a 1 mm thick pure copper sample (sample 100) was measured using the measuring device 1 shown in Figure 1. Note that, unlike this measurement, conventional methods that do not employ undersampling lock-in measurement make it impossible to measure a 1 mm thick pure copper sample.

[0110] The infrared thermography 40 used for the measurement was the SC5200 from FLIR Systems Japan Co., Ltd. (FLIR). The maximum frame rate in full frame on the SC5200 is 100 Hz. Therefore, the frequency that can be measured by the conventional method is up to 25 Hz, which is 1 / 4 of the frame rate. Under these conditions, when undersampling was applied to the lock-in measurement as described above, measurements were taken in the range up to approximately 100 Hz, as shown in Figure 11. The measured thermal diffusivity was +4.2%, which matched the reference value with high accuracy.

[0111] Figure 12 shows the results of the thermal diffusivity mapping of sample 100, which was measured as shown in Figure 11. As shown in Figure 12, an image mapping the thermal diffusivity of sample 100 was obtained. In other words, by applying undersampling to the lock-in measurement, it was possible to avoid the limitation of the measurement frequency due to the sampling theorem. The limitation of the measurement frequency was determined solely by the lock-in detection limit due to the attenuation of the temperature amplitude. Here, the higher the frequency, the more the temperature amplitude attenuates, so the S / N ratio decreases, and the thermal diffusivity mapping is greatly affected by noise. Therefore, appropriate processing of measurement noise is necessary.

[0112] The thermal diffusivity mapping in Figure 12 is the result after noise processing. This noise processing is explained below. First, elements with low R-squared coefficients of determination during fitting were considered to be affected by noise, so the fitted thermal diffusivity results were treated as non-numeric. Next, the thermal diffusivity values ​​of the non-numeric elements were replaced with the average value of the thermal diffusivity of the elements surrounding that element. Finally, the influence of measurement noise was further reduced by applying a Gaussian filter to the elements in sample 100.

[0113] Figure 13 is a thermal diffusivity histogram of sample 100 in Figure 12. In Figure 13, the horizontal axis represents thermal diffusivity, and the vertical axis represents counts. As shown in Figure 13, the measured thermal diffusivity was 119.07 mm. ２ The result is / s, which is the reference value of 117 mm ２ It matched with / s with high accuracy.

[0114] <Measurement Results 3> Figure 14 shows the improvement in the measurement limit of thermal diffusivity in the sample thickness direction. In Figure 14, the horizontal axis represents thermal diffusivity, and the vertical axis represents sample thickness. Figure 14 also shows the conventional measurable range (conventional method) and the range that can be measured with this measurement (expanded range). The measurable limit shown by the dotted line in Figure 14 is calculated from the following equation derived from the transient one-dimensional heat conduction equation assuming an infinite medium. The plots in Figure 14 represent the measurable samples for the conventional and this measurement, respectively.

[0115]

[0116] As shown in Figure 14, it was confirmed that this measurement range allows for measurement of thinner samples compared to the conventional method. Therefore, it was confirmed that using the lock-in thermography periodic heating method in this measurement improves the measurement limit of the thermal diffusivity in the thickness direction of sample 100. Furthermore, in this measurement, it was possible to avoid the limitations of the measurable frequency determined by the principle of phase calculation by lock-in signal processing and the Nyquist sampling theorem.

[0117] <Modified Examples> Figure 15 is a schematic diagram of the measuring device 401 according to Modified Example 1. Figure 16 is a schematic diagram of the measuring device 601 according to Modified Example 2. In Figures 15 and 16, the same reference numerals are used for parts that are the same as in the above embodiment, and their detailed descriptions may be omitted. Next, modified examples of this embodiment will be described with reference to Figures 15 and 16.

[0118] In the above embodiment, the laser-specific phase delay θ in the measuring device 1 Ｌ and the phase delay θ inherent to infrared cameras Ｃ The explanation described how to eliminate both of these. However, it is not limited to this, as long as the configuration reduces the effects of the device's inherent phase delay. For example, the laser's inherent phase delay θ Ｌ and the phase delay θ inherent to infrared cameras Ｃ A configuration that eliminates either one of the two is also acceptable. Furthermore, the laser-specific phase delay θ Ｌ and the phase delay θ inherent to infrared cameras Ｃ It may also be possible to use a configuration that eliminates the phase delay in combination with other methods.

[0119] For example, as shown in the measuring device 401 in Figure 15, a photodetector 71 is provided, and the laser-specific phase delay θ Ｌ A configuration that eliminates this is also acceptable. Note that, unlike the above embodiment, the measuring device 401 does not include an infrared light-emitting diode 73 (see Figure 1).

[0120] Furthermore, as shown in the measuring device 601 in Figure 16, an infrared light-emitting diode 73 is provided, and the phase delay θ inherent to the infrared camera is included. ＣIt may be configured to exclude. Note that the measuring device 601 is configured not to include a photodetector 71 (see FIG. 1) unlike the above-described embodiment.

[0121] <Other Modification Examples> In the above description, it has been described that the infrared thermography 40 measures from the side opposite to the heating surface in the sample 100 heated by the diode laser 10, but it is not limited to this as long as the temperature distribution data of the sample 100 can be acquired. For example, the infrared thermography 40 may be configured to measure on the heating surface of the sample 100 heated by the diode laser 10. That is, heating and measurement may be performed on the same plane in the sample 100.

[0122] In the above description, it has been described that the infrared light-emitting diode 73 is provided on the side opposite to the infrared thermography 40 with the sample 100 interposed therebetween, but it is not limited to this as long as it is configured to be arranged within the angular field of view of the infrared thermography 40. For example, the infrared light-emitting diode 73 may be configured to be provided closer to the infrared thermography 40 side than the sample 100.

[0123] In the above description, when measuring the thermal diffusivity of the sample 100, the phase delay θ Ｌ of the laser itself and the phase delay θ Ｃ of the infrared camera itself are described as being simultaneously measured to remove them, but it is not limited to this. For example, at a timing different from the timing of measuring the thermal diffusivity of the sample 100, before or after the measurement of the thermal diffusivity, the phase delay θ Ｌ of the laser itself and the phase delay θ Ｃ of the infrared camera itself may be measured to remove them. More specifically, for example, using the measuring devices 201 and 301 described in FIG. 7, before and after the measurement of the thermal diffusivity, the phase delay θ Ｌ of the laser itself and the phase delay θ Ｃ of the infrared camera itself are measured, and a process of excluding the phase delay specific to the device may be performed based on these measured phase delays.

[0124] The above explanation describes the use of undersampling, but is not limited to this. For example, a configuration that does not use undersampling is acceptable if it can eliminate the device-specific phase delay. Also, a configuration that does use undersampling is acceptable if it does not eliminate the device-specific phase delay.

[0125] In the above explanation, it was described that the computer 50 performs lock-in signal processing using an infrared thermograph 40, but this is not limited to this. For example, instead of the infrared thermograph 40, a so-called lock-in thermograph that utilizes a lock-in method may be used.

[0126] In the above description, the thermal diffusivity in the thickness direction was explained, but a configuration that provides thermal diffusivity in the in-plane direction is also possible. Furthermore, in the above description, the entire surface of the sample 100 was described as being heated by the diode laser 10 and the light guide unit 20, but this is not the only option. For example, a configuration that heats only a part of the surface of the sample 100 is also possible, such as using so-called line heating or point heating.

[0127] The above description explains that the thermal diffusivity of sample 100 is output, but it is not limited to this. For example, the configuration may output information about thermal diffusivity such as the value of thermal diffusivity, a relative evaluation of thermal diffusivity (e.g., magnitude of thermal diffusivity), or a comparison result with prior evaluation data or theoretical values. Furthermore, the configuration may acquire information about the thermal properties of sample 100, not limited to thermal diffusivity, such as specific heat, thermal conductivity, and interfacial thermal resistance. In other words, the configuration may acquire information about the thermal properties of sample 100, which are physical properties related to heat. Additionally, the configuration may acquire information about the presence or absence of defects (e.g., cracks or voids) inside sample 100, or the distribution of materials (e.g., carbon fibers) that make up sample 100.

[0128] In the above description, the calculation result display unit 55 is shown (outputs) the calculation result of the thermal diffusivity on a display (not shown), but it is not limited to this. For example, the information regarding the thermal diffusivity may be transmitted to another device other than the computer 50, or stored in the device itself.

[0129] Sample 100 is an example of a sample. Diode laser 10 is an example of a light source. Diode laser 10 and first signal generator 61 are an example of an irradiation unit. Infrared thermography 40 is an example of a detection object. Infrared thermography 40 and data acquisition unit 51 are an example of a detection unit. Thermal diffusivity distribution calculation unit 53 is an example of a specific unit. Photodetector 71 is an example of another detection object. Photodetector 71 and second signal generator 63 are an example of an output unit. Measurement device 1 is an example of a device. Infrared light-emitting diode 73 is an example of another light source. Infrared light-emitting diode 73 and second signal generator 63 are an example of another output unit. Phase delay distribution calculation unit 52 is an example of a calibration unit.

[0130] Now, various embodiments and modifications have been described above, but these embodiments and modifications can of course be combined to form a complete system. Furthermore, this disclosure is not limited in any way to the embodiments described above, and can be implemented in various forms without departing from the gist of this disclosure.

[0131] 1... Measuring device, 10... Diode laser, 20... Light guide unit, 40... Infrared thermography, 50... Computer, 70... Calibration unit, 71... Photodetector, 73... Infrared light-emitting diode

Claims

1. An apparatus comprising: an irradiation unit equipped with a light source that periodically irradiates a sample with light from the light source to heat the sample; a detection unit equipped with a detector facing the sample that detects the temperature distribution in the sample heated by the irradiation unit via the detector; a specification unit that identifies information regarding the thermal characteristics of the sample based on a phase delay calculated by performing a lock-in analysis on the temperature response, which is a fluctuation in the temperature distribution detected by the detection unit; and an output unit equipped with another detector different from the detector that detects light irradiated from the light source via the other detector and outputs a reference signal for the lock-in analysis to the specification unit based on the detection signal of the light.

2. The apparatus according to claim 1, wherein the output unit outputs to the detection unit another reference signal that determines the sampling timing of the temperature distribution based on the light detection signal.

3. Frequency f of the light source ｓ , the frame rate f of the detection unit ｒ , and the frequency f at which the specific part locks in. ａ The apparatus according to claim 2, which is represented by the following formulas (1) and (2). ｓ = f ｒ (m+1 / n) (1) f ｒ =nf ａ (2) m: natural number n: number of samples per period of the lock-in frequency, n ≥ 4 4. The apparatus according to claim 3, wherein the output unit is provided in the optical path from the light source to the sample and includes a beam splitter for splitting light, and the other detection unit detects the light from the light source that has been split via the beam splitter.

5. The apparatus according to any one of claims 1 to 4, further comprising another light source that irradiates light toward the detection object, and another output unit that outputs a periodic signal to the other light source that causes the other light source to periodically emit light based on the detection signal of the light detected by the other detection object.

6. The apparatus according to claim 5, wherein the other light source is arranged together with the sample within the detection area of ​​the detector.

7. The apparatus according to claim 6, wherein the light source and the other light source are provided on the opposite side of the sample from the detection body.

8. An irradiation unit equipped with a light source that periodically irradiates a sample with light from the light source to heat the sample; a detection unit equipped with a detector facing the sample that detects the temperature distribution in the sample heated by the irradiation unit via the detector; a specification unit that identifies information regarding the thermal characteristics of the sample based on a phase delay calculated by performing lock-in analysis on the temperature response, which is the fluctuation of the temperature distribution detected by the detection unit; an output unit equipped with another detector different from the detector that detects light irradiated from the light source via the other detector, outputs a reference signal for the lock-in analysis to the specification unit based on the detection signal of the light, and outputs another reference signal to the detection unit that determines the sampling timing of the temperature distribution based on the detection signal of the light; another output unit equipped with another light source that irradiates light toward the detector, and outputs a periodic signal to the other light source that causes the other light source to periodically emit light based on the detection signal of the light detected by the other detector; A device comprising: a calibration unit that calibrates the phase delay calculated by performing a lock-in analysis on the temperature response based on the detection signal of light emitted from the other light source detected by the detection body; 9. An apparatus comprising: an irradiation unit equipped with a light source that periodically irradiates a sample with light from the light source to heat the sample; a detection unit equipped with a detector facing the sample that detects the temperature distribution in the sample heated by the irradiation unit via the detector; an identification unit that identifies information regarding the thermal characteristics of the sample based on a phase delay calculated by performing a lock-in analysis on the temperature response, which is a fluctuation in the temperature distribution detected by the detection unit; and an output unit equipped with another light source that irradiates light toward the detector, which outputs a periodic signal to the other light source that causes the other light source to periodically emit light, and outputs the periodic signal to the identification unit as a reference signal for the lock-in analysis.

10. An apparatus comprising: an irradiation unit equipped with a light source that periodically irradiates a sample with light from the light source to heat the sample; a detection unit equipped with a detector facing the sample that detects the temperature distribution in the sample heated by the irradiation unit via the detector; an identification unit that identifies information regarding the thermal characteristics of the sample based on a phase delay calculated by performing lock-in analysis on the temperature response, which is a fluctuation in the temperature distribution detected by the detection unit; and a calibration unit that calibrates the phase delay in the temperature response detected by the detection unit by detecting light irradiated from the light source via another detector different from the detector, and / or by detecting light irradiated from another light source different from the light source onto the detector.

11. An apparatus comprising: an irradiation unit equipped with a light source that periodically irradiates a sample with light from the light source to heat the sample; a detection unit equipped with a detector facing the sample that detects the temperature distribution in the sample heated by the irradiation unit via the detector; an identification unit that identifies information regarding the thermal characteristics of the sample based on a phase delay calculated by performing lock-in analysis on the temperature response, which is a fluctuation in the temperature distribution detected by the detection unit; and an output unit equipped with another detector different from the detector that detects light irradiated from the light source via the other detector and outputs a reference signal to the detection unit that determines the sampling timing of the temperature distribution based on the detection signal of the light.

12. A method comprising: periodically irradiating a sample with light from a light source to heat the sample; detecting the temperature distribution in the heated sample via a detector; identifying information regarding the thermal properties of the sample based on a phase delay calculated by performing a lock-in analysis on the temperature response, which is a variation in the detected temperature distribution; and detecting light irradiated from the light source via another detector different from the detector, and outputting a reference signal for the lock-in analysis based on the detected light signal.

13. A program that causes a computer to perform the following functions: a function to detect the temperature distribution in a sample heated by periodically irradiating the sample with light from a light source via a detector; a function to receive a reference signal output based on the detection signal of the light detected by another detector different from the detector, where the light irradiated from the light source is detected by the other detector; and a function to identify information regarding the thermal properties of the sample by performing a lock-in analysis on the temperature response, which is the fluctuation of the detected temperature distribution, based on the reference signal and calculating the phase delay.

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