KR102373676B1 - THz SENSOR AND METHOD FOR DETECTING THEREOF - Google Patents

Abstract

The present technology discloses a terahertz sensor and a method for controlling the same. According to the embodiment according to the present technology, terahertz measured using a cheap black body source light source that irradiates infrared light and an optical part that includes a beam interrupter, an aperture, and a terahertz wave filter with reduced alignment time By estimating the noise equivalent voltage of the terahertz sensor using the QCL light source from the noise equivalent voltage of the sensor, it is possible to reduce the installation cost and management cost for the board measurement device using the terahertz sensor, and to shorten the alignment time of the optics. Accordingly, it is possible to quickly measure the physical properties of the board to be tested.

Description

THz SENSOR AND METHOD FOR DETECTING THEREOF

The present invention relates to a terahertz sensor and a method for measuring the same, and more particularly, based on the amount of infrared light irradiated to a board from a blackbody source light source that generates infrared light of a predetermined wavelength and the amount of infrared light emitted through the board It relates to a technology that can measure the physical properties of a board using a terahertz wavelength.

The terahertz wave (THz wave), which simultaneously goes through the dielectric permeability of radio waves and the straightness of light waves in terms of its spectral position, is an electromagnetic wave located between microwaves and infrared rays, and its frequency is defined as a section of approximately 0.1 to 10 THz.

In addition, terahertz waves, which are well absorbed by moisture, can be applied as new technologies in imaging, spectroscopy, and communication fields. Terahertz waves can be used to see through the inside of opaque objects, or to analyze biological mechanisms and cosmic signals of molecular kinetic energy levels. In addition, the use of terahertz waves enables ultra-high-speed, short-range wireless communications that are far superior to microwaves and millimeter waves.

A terahertz wave generator using such a pulsed light source technology includes a photoconductive antenna and an optical rectification method, and a terahertz wave generator using a continuous wave light source technology includes a photomixer and a hot hole laser. (Hothole Laser), Free Electron Laser (Free Electron Laser), quantum cascade laser (Quantum Cascade Laser) and the like.

Meanwhile, terahertz time-domain spectroscopy is a method of analyzing a material using a terahertz pulse wave, and since the amplitude and phase of the terahertz signal can be simultaneously known, the permittivity or thickness of the material can be calculated without approximation. Since the terahertz pulsed spectroscopy system is constructed using an expensive QCL (Quantum Cascade Laser), it is large in size and high in price. Optical components are also expensive and have disadvantages in that it takes a long time to prepare for optical alignment when measuring once.

In order to overcome and compensate for these shortcomings, the present applicant used a terahertz wave sensor that measures the physical properties of the board with the amount of infrared light of terahertz wave irradiated to the board and the amount of infrared light emitted through the board instead of a QCL (Quantum Cascade Laser) light source. We would like to propose a method for producing a low-cost infrared light source as a black body source light source.

Accordingly, an object of the present invention is to provide a terahertz sensor capable of reducing installation and management costs by using a low-cost black body source light source irradiating infrared rays and low-cost optical components, and a method for measuring the same.

Another object of the present invention is to provide a terahertz sensor and a method for measuring the same, which can reduce the measurement time by shortening the alignment time of an optical unit by the terahertz sensor and the measuring method thereof.

The object of the present invention is not limited to the object mentioned above, and other objects and advantages of the present invention not mentioned can be understood by the following description, and will be more clearly understood by the examples of the present invention. Further, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof indicated in the appended claims.

Technical problem according to an embodiment of the present invention for achieving the above object,

a light source unit irradiating a black body source light source that generates infrared rays of a predetermined wavelength; an optical unit passing the infrared light irradiated from the light source unit according to a predetermined chopper frequency; a terahertz sensor for measuring physical properties of the board with the amount of infrared light of a predetermined wavelength of the optical unit irradiated to the board and the amount of infrared light passing through the board; a detection unit configured to detect the amount of infrared light irradiated from the terahertz sensor and the amount of infrared light that has passed through the board; and an analyzer configured to quantitatively evaluate the terahertz sensor by analyzing the detected amount of irradiated infrared light and the amount of infrared light that has passed through the board.

Preferably, the light source unit includes: a light beam interrupter for passing a black body source light source having an infrared wavelength in a terahertz cycle; an aperture that determines the power intensity of the blackbody source light source passing through; and a terahertz wave filter that transmits infrared of a terahertz wavelength among the black body source light sources of the infrared wavelength of the terahertz cycle.

Preferably, the analysis unit uses the table value derived based on the ratio of the noise equivalent voltage (QCL NEP) of the terahertz sensor using the QCL light source and the noise equivalent voltage (BBS NEP) of the terahertz sensor using the black body source light source to the beam interceptor. a database building module that matches and stores the frequency and wavelength of an operation module for calculating the noise equivalent voltage (BBS NEP) of a terahertz sensor using a black body source (BBS) light source; a table value reading module for reading a stored table value matched to a noise equivalent voltage (BBS NEP) of a terahertz sensor using the calculated black body source light source; and an estimation module for estimating the noise equivalent voltage (QCL NEP) of the terahertz sensor using the QCL light source based on the read table value and the noise equivalent voltage (BBS NEP) of the terahertz sensor using the light source.

Preferably, the operation module measures a signal-to-noise ratio with the amount of infrared light of terahertz wave provided to the board and the amount of infrared light that has passed through the board, and the incident infrared irradiance (E) and the detection element from the measured signal-to-noise ratio. The reactivity may be calculated from the product of the response area A _D ratio, and a noise equivalent voltage (BBS NEP) may be derived from the calculated reactivity and the noise ratio.

Preferably, the noise may be provided as a voltage measured from the amount of infrared light passed through the board after blocking the infrared rays provided to the board.

In another embodiment of the present invention using the above-described terahertz sensor, the terahertz sensor measurement method includes a noise equivalent voltage (QCL NEP) of a terahertz sensor using a QCL light source and noise of a terahertz sensor using a black body source light source. A database construction step of matching and storing the table value derived based on the ratio of the equivalent voltage (BBS NEP) to the frequency and wavelength of the beam interrupter; an operation step of calculating a noise equivalent voltage (BBS NEP) of a terahertz sensor using a black body source (BBS) light source; a table value reading step of reading a stored table value matching a noise equivalent voltage (BBS NEP) of a terahertz sensor using the calculated black body source light source; and estimating the noise equivalent voltage (QCL NEP) of the terahertz sensor using the QCL light source based on the read table value and the noise equivalent voltage (BBS NEP) of the terahertz sensor using the light source.

According to the terahertz sensor and the measuring method thereof according to the present invention having the configuration as described above, the low-cost black body source light source irradiating infrared light, a light beam interrupter, an aperture, and a terahertz wave filter are included in the low-cost and alignment By estimating the noise equivalent voltage of the terahertz sensor using the QCL light source from the noise equivalent voltage of the terahertz sensor measured using the time-reducing optics, the installation and management costs for the board measuring device using the terahertz sensor are reduced. It can be reduced, and as the alignment time of the optical part is shortened, the effect of quickly measuring the physical properties of the board to be tested is obtained.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical spirit of the present invention together with the detailed description of the present invention to be described later, so the present invention is a matter described in such drawings should not be construed as being limited only to
1 is a block diagram of an apparatus for measuring a board using a terahertz sensor according to an embodiment of the present invention.
2 is a waveform diagram illustrating a noise equivalent voltage of a terahertz sensor using a black body source light source according to an embodiment of the present invention.
3 is a waveform diagram illustrating a noise equivalent voltage of a terahertz sensor using a QCL light source applied to an embodiment of the present invention.
4 is a diagram illustrating a detailed configuration of an analysis unit of an apparatus for measuring a board using a terahertz sensor according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. However, in describing the embodiments, descriptions of technical contents that are well known in the technical field to which the present invention pertains and are not directly related to the present invention will be omitted as much as possible. This is to more clearly convey the essence of the present invention by omitting unnecessary description.

1 is a block diagram of a board test apparatus using a terahertz sensor according to an embodiment of the present invention. Referring to FIG. 1 , the board test apparatus S using a terahertz sensor includes a light source unit 100, an optical unit ( 200 ), a terahertz sensor 300 and a board 400 , a detection unit 500 , and an analysis unit 600 .

The light source unit 100 may be provided as a black body source that oscillates laser light having a wavelength in a predetermined range (1 to 30 μm). That is, the black body source repeatedly oscillates a set wavelength variable range at a set frequency speed according to an AC signal supplied from the outside, and then amplifies and irradiates the oscillated infrared light based on a predetermined gain. At this time, the temperature of the black body source is constantly maintained at 50 ~ 1000 ℃. Therefore, the temperature of the light source using the existing QCL is

In this case, the irradiated infrared light passes through the optical unit 200 and is transmitted to the terahertz wave sensor 400 .

Here, in the optical unit 200 , a beam chopper 210 , an aperture 220 , and a terahertz wave filter 230 may be sequentially mounted. Here, the beam interrupter 210 intercepts the laser light supplied from the black body source at a predetermined period to obtain an AC output and then amplifies it. For convenience in the description of the present invention, the beam interrupter 210 is described as a chopper of a rotating fan-shaped shielding plate, but a small shielding plate moves back and forth by a cam and a tuning fork that vibrates by a tuning fork oscillator The method of fixing the shielding board to the substrate is applicable, but is not limited thereto.

For such a shielding substrate, when a metal is used, light of all wavelengths is interrupted. For example, when a shielding substrate made of a single crystal plate of potassium chloride is used, laser light with a wavelength of 23 μm or less is not interrupted, and only laser light higher than that is interrupted. do. Accordingly, laser light having an infrared wavelength having a wavelength longer than 23 μm is output from the chopper 210 .

In addition, the aperture 220 controls the amount of laser light by determining the size of the laser light passing through the beam interrupter 210 . A series of processes for controlling the amount of laser light of infrared wavelength that has passed through the beam interrupter 210 using the aperture 220 is based on the existing actual diameter of the laser, the dimensions of the aperture and parabolic radiation plane, and the shape of the given amount of light. It is the same or similar to the general process of regulating.

In addition, the terahertz wave filter (THz: 230) may be provided to pass only terahertz waves among the laser light passing through the aperture 220. That is, the terahertz wave filter 230 performs a function of passing infrared rays having a terahertz wave frequency component among the laser light passing through the aperture 220 , and the infrared rays passing through the terahertz wave filter 230 are It is transmitted to the terahertz sensor 300 . Accordingly, in the case of a light source using the existing QCL, a terahertz wave of continuously variable frequency is provided to the terahertz sensor 300 using an optical system using a collimating lens, a chopper, a shutter, and an image lens, whereas the black body source In the case of a light source using a light source using a beam interrupter, an aperture, and a shutter, the terahertz wave with continuously variable frequency is provided to the terahertz sensor 300, thereby reducing the installation cost due to low-cost optical components and reducing the optical alignment time. This is reduced

In addition, the terahertz sensor 300 may be provided as an antenna-coupled bolometer sensor, and the infrared light of the terahertz wave passing through the terahertz wave filter 230 is irradiated to the board 400 to be tested and the board ( 400) performs a function of measuring the amount of infrared light of the terahertz wave that has passed through, and the amount of infrared light that has passed through the irradiated infrared light (incident infrared irradiance E) and the board 400 to be tested (signal voltage Vs) is It is transmitted to the detection unit 500 .

The detection unit 500 amplifies the amount of irradiated infrared light and the amount of infrared light that has passed through the board 400 to a predetermined gain, and then triggers the amplified board of a predetermined frequency band using an AC signal supplied from the outside. It may include a lock-in amplifier (Lock-in Amplifier) for extracting the amount of the irradiated infrared light of the 400 and the infrared light that has passed through the board (400). Accordingly, the terahertz wave signal of the board 400 amplified by a predetermined gain may be extracted by the lock-in amplifier while being triggered using the AC signal and transmitted to the analysis unit 600 .

The analysis unit 600 may continuously and high-speed acquire the amount of infrared light irradiated from the detection unit 500 and the amount of output infrared light. Then, the analysis unit 500 searches for the intensity of the terahertz wave power of the board 400 and uses the terahertz wave to prevent the intensity of the terahertz wave from exceeding a predetermined threshold based on the search result. A stable amount of infrared light in which the power intensity of the terahertz wave does not exceed a predetermined threshold is obtained by intermitting the phase.

In addition, the analysis unit 600 measures the signal-to-noise ratio after digitizing and averaging the infrared light amount of the obtained board 400, and based on the measured signal-to-noise ratio, Responsivity, and Noise Equivalent Voltage ( Quantitative evaluation of the terahertz sensor 300 is performed based on NEP: Noise Equivalent Power.

That is, the quantitative evaluation of the terahertz sensor 300 is made with the noise equivalent voltage derived from the reactivity, and the responsivity is the amount of infrared light of the terahertz wave irradiated to the board 400 and the board 400 . It is derived as the ratio of the product of the reaction area of the detection element to the amount of infrared light that has passed through and satisfies Equation 1 below.

.. 식 1

.. Equation 1

Then, the noise equivalent voltage (NEP) is derived by dividing the measured noise by the above-described reactivity after blocking the amount of irradiated infrared light, and satisfies Equation 2 below.

... 식 2

... Equation 2

Here, E is the amount of infrared light radiated through the board 400, A _D is A detection area, Vn is a noise voltage, and Vs is a signal voltage.

이고, 90 ∼ 110 ㎛ 의 적외선인 경우 전압등가전압(NEP)은 1.06x10^{- 12}

임을 확인할 수 있다. 2 is a waveform showing the noise equivalent voltage (NEP), which is a quantitative evaluation of the terahertz sensor 300 measured in the board test apparatus using the black body source light source shown in FIG. 1 . Referring to FIG. 2 , the light flux interrupter The frequency of (210) is 24Hz, and in the case of infrared with a wavelength of 80 to 120 μm, the voltage equivalent voltage (NEP) is 2.34x10 ^-12

and the voltage equivalent voltage (NEP) is 1.06x10 ^{- 12} in the case of infrared rays of 90 ~ 110 ㎛

It can be confirmed that

임을 확인할 수 있다. 따라서, 도 2에 도시된 블랙바디 소스 광원을 이용한 테라헤르츠 센서(300)의 잡음등가전압(BBS NEP)와 QCL 광원을 이용한 잡음등가전압(QCL NEP)는 4 오더 정도의 차이가 발생된다.3 is a waveform diagram showing a noise equivalent voltage (NEP), which is a quantitative evaluation value of the terahertz sensor 300 measured using a QCL light source instead of the black body source light source shown in FIG. 1 . Referring to FIG. 3 , QCL The voltage equivalent voltage (NEP) of the terahertz sensor 300 measured using a 3THz light source is 2.5x10 ^-12

It can be confirmed that Therefore, the difference between the noise equivalent voltage (BBS NEP) of the terahertz sensor 300 using the black body source light source shown in FIG. 2 and the noise equivalent voltage (QCL NEP) using the QCL light source is about 4 orders of magnitude difference.

인 반면 블랙바디 소스(BBS) 광원을 이용한 테라헤르츠 센서(300)의 잡음등가전압(NEP)은 광속 단속기(210)의 주파수 24Hz에서 80 ∼ 120 ㎛ 의 적외선인 경우 4.17x10^-9

이고, 90 ∼ 110 ㎛ 의 적외선인 경우 1.89x10^-9

이다. 따라서, QCL 광원을 이용한 테라헤르츠 센서(300)의 잡음등가전압(QCL NEP)과 블랙바디소스 광원을 이용한 테라헤르츠 센서(300)의 잡음등가전압(BBS NEP)의 비는 광원의 파장에 대해 10배 내지 50배의 차이가 발생된다.That is, when the terahertz sensor 300 is an antenna-coupled bolometer type, the noise equivalent voltage (QCL NEP) of the terahertz sensor 300 using a QCL 3THz light source is 3.54x10 ^-8

On the other hand, the noise equivalent voltage (NEP) of the terahertz sensor 300 using a black body source (BBS) light source is 4.17x10 ^-9 in the case of infrared rays of 80 to 120 μm at a frequency of 24 Hz of the beam interrupter 210 .

and 1.89x10 ^-9 in the case of infrared rays of 90 to 110 μm

am. Therefore, the ratio between the noise equivalent voltage (QCL NEP) of the terahertz sensor 300 using the QCL light source and the noise equivalent voltage (BBS NEP) of the terahertz sensor 300 using the black body source light source is 10 for the wavelength of the light source. A difference of fold to 50 fold occurs.

Accordingly, the analyzer 600 may estimate the noise equivalent voltage QCL NEP of the terahertz sensor 300 using the QCL light source based on the ratio of the noise equivalent voltage QCL NEP and the noise equivalent voltage BBS NEP.

That is, as shown in FIG. 4 , the analysis unit 600 determines the noise equivalent voltage (QCL NEP) of the terahertz sensor 300 using the QCL light source and the noise equivalent voltage of the terahertz sensor 300 using the black body source light source. A database building module 610 that matches and stores the table values derived based on the ratio of voltages (BBS NEP) to the frequency and wavelength of the beam interrupter 210, and a terahertz sensor using a BlackBody Source (BBS) light source. The operation module 620 that calculates the noise equivalent voltage (BBS NEP) of 300 reads the stored table value matching the noise equivalent voltage (BBS NEP) of the terahertz sensor 300 using the calculated black body source light source. The output is the table value reading module 630, and the noise equivalent voltage of the terahertz sensor 300 using the QCL light source based on the read table value and the noise equivalent voltage (BBS NEP) of the terahertz sensor 300 using the light source ( and an estimation module 640 for estimating QCL NEP).

That is, the database building module 610 of the analysis unit 600 includes the noise equivalent voltage (QCL NEP) of the terahertz sensor 300 using the QCL light source and the noise equivalent voltage of the terahertz sensor 300 using the black body source light source. The ratio of (BBS NEP) is matched to the frequency and wavelength of the beam interrupter 210 and stored as a table value.

Then, based on the ratio of the noise (Vn) and the signal voltage (Vs) of the terahertz sensor measured using the black body source light source based on the BBS calculation module 620, the noise equivalent voltage (BBS NEP) is calculated and the table value is read. It passes to module 630 .

Accordingly, the table value reading module 630 matches the received noise equivalent voltage (BBS NEP) and reads the table value recorded in the database, and then the read table value and the noise equivalent voltage (BBS NEP) are sent to the estimation module 640 . is transmitted

The estimation module 640 estimates the noise equivalent voltage (QCL NEP) of the terahertz sensor 300 using the QCL light source based on a preset relational expression from the received noise equivalent voltage (BBS NEP) and the table value (a), and the relation is Equation 3 below is satisfied.

QCL NEP=a*BBS NEP.. Equation 3

Here, a is a table value, and it can be seen that the table value is 0.1 or 0.05 for two regions of the same wavelength, respectively.

Accordingly, the noise of the terahertz sensor 300 measured using a cheap black body source light source that irradiates infrared light and an optical part that includes a beam interrupter, an aperture, and a terahertz wave filter with reduced alignment time. By estimating the noise equivalent voltage of the terahertz sensor 300 using the QCL light source from the equivalent voltage, the installation cost and management cost for the board test device using the terahertz sensor can be reduced, and the alignment time of the optics can be shortened. You can quickly measure the physical properties of the board you want to test according to.

In another embodiment of the present invention, the board test method using the terahertz sensor is a noise equivalent voltage (QCL NEP) of the terahertz sensor 300 using the QCL light source and the terahertz sensor 300 using the black body source light source. a database construction step of matching and storing the table value derived based on the ratio of the noise equivalent voltage (BBS NEP) to the frequency and wavelength of the beam interrupter 210; an operation step of calculating a noise equivalent voltage (BBS NEP) of the terahertz sensor 300 using a black body source (BBS) light source; a table value reading step of reading a stored table value matching the noise equivalent voltage (BBS NEP) of the terahertz sensor 300 using the calculated black body source light source; and estimating the noise equivalent voltage (QCL NEP) of the terahertz sensor 300 using the QCL light source based on the read table value and the noise equivalent voltage (BBS NEP) of the terahertz sensor 300 using the light source. Each step of the above-described board test method using the terahertz sensor is performed by the above-described database building module 610 , arithmetic module 620 , table value reading module 630 , and estimation module 640 . Detailed reference to the function is omitted.

Accordingly, the noise equivalent voltage of the terahertz sensor 300 measured using a low-cost black body source light source irradiating infrared light, a low-cost optical unit including a beam interrupter, an aperture, and a terahertz wave filter with reduced alignment time. By estimating the noise equivalent voltage of the terahertz sensor 300 using the QCL light source from You can quickly measure the physical properties of the desired board.

Although the above has been described with reference to the preferred embodiment of the present invention, those skilled in the art can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention described in the claims below. You will understand that you can.

A QCL light source was obtained from the noise equivalent voltage of a terahertz sensor measured using a low-cost black-body source light source that irradiates infrared light and a low-cost and reduced alignment time optic including a beam interrupter, aperture, and terahertz wave filter. By estimating the noise equivalent voltage of the used terahertz sensor, the installation and management costs for the board test device using the terahertz sensor can be reduced. It can bring very great progress in terms of operation accuracy and reliability, as well as performance efficiency, for a board measuring device and method using a terahertz sensor that can measure quickly, and the possibility of commercialization or sales of the applied terahertz sensor This is not only sufficient, but it is an invention that has industrial applicability because it can be clearly implemented in reality.

100: light source unit
200: optical unit
210: beam chopper
220 : aperture
230: terahertz wave filter
300: terahertz sensor
400: board
500: detection unit
600: analysis unit
610: database building module
620: arithmetic module
630: table value reading module
640: estimation module

Claims (6)

a light source unit irradiating a black body source light source that generates infrared rays of a predetermined wavelength;
an optical unit passing the infrared light irradiated from the light source unit according to a predetermined chopper frequency;
a terahertz sensor for measuring physical properties of the board with the amount of infrared light of a predetermined wavelength of the optical unit irradiated to the board and the amount of infrared light passing through the board;
a detection unit configured to detect the amount of infrared light irradiated from the terahertz sensor and the amount of infrared light that has passed through the board; and
and an analysis unit that performs quantitative evaluation of the terahertz sensor by analyzing the detected amount of irradiated infrared light and the amount of infrared light that has passed through the board;
The light source unit,
a beam interrupter that passes a black body source light source with an infrared wavelength in terahertz;
an aperture for determining the power intensity of the black body source light source passing through the beam interrupter; and
It is provided with a terahertz wave filter that passes infrared of a terahertz wavelength among the black body source light sources of the infrared wavelength of the terahertz cycle,
The analysis unit,
The table value derived based on the ratio of the noise equivalent voltage (QCL NEP) of the terahertz sensor using the QCL (Quantum Cascade Laser) light source and the noise equivalent voltage (BBS NEP) of the terahertz sensor using the black body source light source a database building module that matches and stores frequencies and wavelengths;
an operation module for calculating the noise equivalent voltage (BBS NEP) of a terahertz sensor using a black body source (BBS) light source;
a table value reading module for reading a stored table value matched to a noise equivalent voltage (BBS NEP) of a terahertz sensor using the calculated black body source light source; and
Terahertz comprising an estimation module for estimating the noise equivalent voltage (QCL NEP) of the terahertz sensor using the QCL light source based on the read table value and the noise equivalent voltage (BBS NEP) of the terahertz sensor using the light source sensor.
delete delete According to claim 1, wherein the operation module,
measuring the signal-to-noise ratio with the amount of infrared light of the terahertz wave provided to the board and the amount of infrared light that has passed through the board;
Calculate the reactivity from the product of the incident infrared irradiance (E) and the response area (A _D ) ratio of the detection element from the measured signal-to-noise ratio,
A terahertz sensor, characterized in that it is provided to derive a noise equivalent voltage (BBS NEP) from the calculated reactivity and noise ratio.
5. The method of claim 4, wherein the noise is
A terahertz sensor comprising a voltage measured from the amount of infrared light passing through the board after blocking the infrared light provided to the board.
The table value derived based on the ratio of the noise equivalent voltage (QCL NEP) of the terahertz sensor using the QCL (Quantum Cascade Laser) light source and the noise equivalent voltage (BBS NEP) of the terahertz sensor using the black body source light source Database construction step of matching and storing the frequency and wavelength;
an operation step of calculating a noise equivalent voltage (BBS NEP) of a terahertz sensor using a black body source (BBS) light source;
a table value reading step of reading a stored table value matching a noise equivalent voltage (BBS NEP) of a terahertz sensor using the calculated black body source light source; and
terahertz comprising an estimation step of estimating the noise equivalent voltage (QCL NEP) of the terahertz sensor using the QCL light source based on the read table value and the noise equivalent voltage (BBS NEP) of the terahertz sensor using the light source How to measure the sensor.

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