JP2011033586A - Observation method, incident timing setting method, and observation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To observe a sample with high contrast in the observation of an observation range containing a region where a sample is present and a region where the sample is not present. <P>SOLUTION: This observation method includes the step of irradiating the observation range containing the sample A with a pulselike terahertz wave L<SB>2</SB>to apply the first electromagnetic wave L<SB>2</SB>, which is reflected from or transmitted through the observation region, and a pulselike second electromagnetic wave L<SB>1</SB>, of which the wavelength is shorter than that of the terahertz wave L<SB>2</SB>, to an optical crystal 8 and the step of detecting the second electromagnetic wave L<SB>1</SB>emitted from the optical crystal 8. The second electromagnetic wave L<SB>1</SB>is applied to the optical crystal 8 in the timing arranged to a phase wherein one of the electric field amplitude of the first electromagnetic wave L<SB>2</SB>reflected from or transmitted through the sample A present in the observation region and the electric field amplitude of the first electromagnetic wave L<SB>2</SB>reflected from or transmitted through a region other than the sample A in the observation range becomes larger than the other one of them. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an observation method, an incident timing setting method, and an observation apparatus.

Conventionally, as a sensing technique for a transparent substance (for example, water), a technique using terahertz waves is known (for example, see Non-Patent Document 1).
This sensing technology utilizes the fact that a terahertz wave has an intensity distribution according to its component distribution when the terahertz wave is passed through a transparent sample.

  In Non-Patent Document 1, a terahertz wave that has passed through a transparent sample is incident on an electro-optic crystal, while near-infrared light that is incident on the same optical path by a dichroic mirror is applied to the electro-optic crystal. When the electro-optic crystal is irradiated with terahertz waves, the characteristics change according to the electric field state. That is, sample information is recorded on the electro-optic crystal. When the near-infrared light passes through the electro-optic crystal in which the sample information is recorded, the near-infrared light is modulated during the passage. Therefore, the component distribution of the sample can be photographed by detecting the modulated near infrared light.

Edited by Junichi Nishizawa, “Basics and Applications of Terahertz Waves”, published by Industrial Research Institute, Inc., April 1, 2005, p160-161

  However, the terahertz wave incident on the electro-optic crystal is not only the terahertz wave incident on the electro-optic crystal after passing through the sample, but also the terahertz wave incident on the electro-optic crystal without passing through the sample has a spatial distribution of the electric field. Have. Therefore, if there is a region where the sample exists and a region where the sample does not exist in the observation range, some information is written in the electro-optic crystal even in the region where the sample exists. Is difficult to observe with high contrast.

  The present invention has been made in view of the above-described circumstances, and an observation method and an incident timing setting method capable of observing a sample with high contrast in observation of an observation range including a region where the sample exists and a region where the sample does not exist And to provide an observation device.

In order to achieve the above object, the present invention provides the following means.
The present invention irradiates a pulsed terahertz wave to an observation range including a sample, whereby a first electromagnetic wave reflected or transmitted through the observation range and a pulse shape having a shorter wavelength than the terahertz wave A sample in which the second electromagnetic wave is incident on the optical crystal and a step of detecting the second electromagnetic wave emitted from the optical crystal, wherein the second electromagnetic wave is present in the observation range. The phase at which one of the amplitude of the electric field of the first electromagnetic wave reflected or transmitted through the sample or the amplitude of the electric field of the first electromagnetic wave reflected or transmitted through the region within the observation range is larger than the other. An observation method for entering the optical crystal at a timing arranged in the above is provided.

  According to the present invention, when the first electromagnetic wave composed of a pulsed terahertz wave is irradiated to the observation range including the sample, the phase delay in the first electromagnetic wave is an amount corresponding to the refractive index distribution of each part of the sample. Alternatively, the amplitude changes due to absorption in the sample. Therefore, the first electromagnetic wave has a spatial change in its electric field waveform according to the presence or absence of the sample, the refractive index distribution and the absorption characteristic distribution in the sample. When the first electromagnetic wave is incident on the optical crystal, the electric field amplitude distribution of the first electromagnetic wave is reflected as the characteristic distribution of the optical crystal at a certain timing when the first electromagnetic wave passes through the crystal. Further, when the first electromagnetic wave propagates in the crystal, the amplitude thereof changes with the passage of time.

  When the electric field amplitude distribution of the first electromagnetic wave written in the optical crystal is read by the pulsed second electromagnetic wave having a shorter wavelength than the first electromagnetic wave, the optical crystal of the pulsed second electromagnetic wave The distribution of the electric field amplitude of the first electromagnetic wave incident on the optical crystal is read out at a timing coincident with the incidence on the optical crystal. In this case, the electric field amplitude of the first electromagnetic wave reflected or transmitted through the sample or the phase of the electric field amplitude of the first electromagnetic wave reflected or transmitted through the region other than the sample coincides with the phase that is larger than the other. By making the second electromagnetic wave incident on the optical crystal at the timing to suppress the influence of the first electromagnetic wave having the smaller amplitude, the amplitude distribution of the larger first electromagnetic wave can be read by the second electromagnetic wave. . As a result, the sample can be observed with good contrast.

In the above invention, the second electromagnetic wave is reflected in the sample existing in the observation range or reflected in the electric field amplitude of the first electromagnetic wave transmitted through the sample or in a region other than the sample in the observation range or the region. It is preferable that one of the electric field amplitudes of the first electromagnetic wave that has passed through is incident on the optical crystal at a timing at which the electric field amplitude is arranged to be substantially zero.
By doing so, the first electromagnetic wave on the side where the amplitude is almost zero is almost extinguished, so that the first electromagnetic wave on the side having the larger amplitude is not affected by the first electromagnetic wave. The electric field amplitude distribution of the electromagnetic wave can be read out by the second electromagnetic wave, and the sample can be observed with higher contrast.

  Further, the present invention is a method for setting the timing of incidence of the second electromagnetic wave in the observation method, wherein the observation range is reflected or irradiated by irradiating a pulsed terahertz wave to the observation range. Causing the first electromagnetic wave and the second electromagnetic wave transmitted through the optical crystal to enter the optical crystal while changing an incident timing of the second electromagnetic wave with respect to the first electromagnetic wave, and the first electromagnetic wave emitted from the optical crystal. After performing the step of acquiring the intensity distribution of the electromagnetic wave 2 and the step of storing the acquired intensity distribution in association with the incident timing in the case where the sample is disposed within the observation range and the case where the sample is not disposed, For each incident timing of the electromagnetic wave 2, the intensity distribution of the second electromagnetic wave stored without arranging the sample and the sample are arranged and stored. A step of correcting one of the intensity distributions of the second electromagnetic wave by subtracting one from the other or dividing one by the other, and an absolute value of a difference between the maximum intensity and the minimum intensity in the corrected intensity distribution of the second electromagnetic wave An incident timing setting method is provided that performs the step of selecting an incident timing at which the maximum becomes.

  According to the present invention, first, the first electromagnetic wave is incident on the optical crystal without placing the sample in the observation range, and the second electromagnetic wave is applied to the optical crystal while shifting the incident timing of the second electromagnetic wave. The intensity distribution obtained by making the incident and detecting the second electromagnetic wave emitted from the optical crystal is stored together with the incident timing of the second electromagnetic wave. Next, the same detection as described above is performed in a state where the sample is disposed within the observation range, and the obtained intensity distribution of the second electromagnetic wave is stored together with the incident timing of the second electromagnetic wave. Then, one of the intensity distributions of the second electromagnetic wave when the sample detected when the second electromagnetic wave is incident at the same incident timing and the sample not arranged are subtracted from the other, or one is divided by the other. It corrects by doing. By selecting the timing at which the absolute value of the difference between the maximum intensity and the minimum intensity is maximized in the corrected second electromagnetic wave intensity distribution, the second intensity distribution is less affected by the other intensity distribution. The incident timing of the electromagnetic wave can be set.

  Further, the present invention is a method for setting the timing of incidence of the second electromagnetic wave in the observation method, irradiating a pulsed terahertz wave to the observation range without placing a sample in the observation range, The first electromagnetic wave and the second electromagnetic wave that are reflected in or transmitted through the observation range are incident on an optical crystal while changing the incident timing of the second electromagnetic wave with respect to the first electromagnetic wave. An intensity distribution of the second electromagnetic wave emitted from the crystal is acquired, the acquired intensity distribution is stored in a database in association with the incident timing, a sample is arranged in the observation range, and the observation range The first electromagnetic wave reflected by or transmitted through the observation range by irradiating a pulsed terahertz wave to the first electromagnetic wave and the second electromagnetic wave Incidently entering the optical crystal while changing the incident timing of the second electromagnetic wave with respect to the magnetic wave; acquiring the intensity distribution of the second electromagnetic wave emitted from the optical crystal; and acquiring the acquired intensity distribution After performing the step of storing in association with the timing, the second electromagnetic wave intensity distribution and the sample stored in the database are stored and stored for each incident timing of the second electromagnetic wave. In the step of correcting one of the two electromagnetic wave intensity distributions by subtracting one from the other or dividing one by the other, and the corrected second electromagnetic wave intensity distribution, the absolute value of the difference between the maximum intensity and the minimum intensity is An incident timing setting method is provided that performs the step of selecting the largest incident timing.

  According to the present invention, the first electromagnetic wave is incident on the optical crystal in advance without shifting the sample within the observation range, and the second electromagnetic wave is incident on the optical crystal while shifting the incident timing of the second electromagnetic wave. Since the intensity distribution obtained by detecting the second electromagnetic wave emitted from the optical crystal and the incident timing of the second electromagnetic wave are stored as a database, the sample is not arranged at each observation. It is not necessary to perform the work of acquiring the intensity distribution of the second electromagnetic wave for each incident timing of the second electromagnetic wave. Therefore, the second electromagnetic wave in which one intensity distribution is least affected by the other intensity distribution is obtained only by acquiring the intensity distribution of the second electromagnetic wave while shifting the incident timing in a state where the sample is arranged in the observation range. Can be set. As a result, the incident timing of the second electromagnetic wave capable of observing the sample with high contrast can be set.

  Further, the present invention is a method for setting the timing of incidence of the second electromagnetic wave in the above observation method, wherein a sample is placed in the observation range and a pulsed terahertz wave is irradiated to the observation range. The step of causing the first electromagnetic wave and the second electromagnetic wave reflected or transmitted through the observation range to enter the optical crystal while changing the incident timing of the second electromagnetic wave with respect to the first electromagnetic wave. And acquiring the intensity distribution of the second electromagnetic wave emitted from the optical crystal, and storing the acquired intensity distribution in association with the incident timing. The sample is arranged based on the intensity of one of the second electromagnetic waves emitted from the optical crystal corresponding to the region where the sample does not exist in the intensity distribution of the electromagnetic wave. A step of generating an intensity distribution of the second electromagnetic wave when not being performed, and one of the intensity distribution of the second electromagnetic wave stored and the intensity distribution of the second electromagnetic wave when the generated sample is not disposed Correcting by subtracting or dividing one by the other, and selecting an incident timing at which the absolute value of the difference between the maximum intensity and the minimum intensity is the largest in the corrected second electromagnetic wave intensity distribution, An incident timing setting method is provided.

  According to the present invention, an intensity distribution based on the intensity of the second electromagnetic wave emitted from the optical crystal corresponding to a region where no sample exists in the observation range is generated, and the second electromagnetic wave obtained from the observation range is generated. Therefore, it is sufficient to acquire the intensity of the representative second electromagnetic wave from the optical crystal corresponding to the region where the sample does not exist for correction. Thus, it is possible to set the incident timing of the second electromagnetic wave capable of observing the sample with high contrast. At this time, it is not necessary to perform measurement separately between the state in which the sample is not disposed and the state in which the sample is disposed, and the incident timing can be set easily and quickly.

  Further, the present invention is a method for setting the timing of the incidence of the second electromagnetic wave in the observation method, wherein the second electromagnetic wave is applied to the optical crystal in a state where the first electromagnetic wave is not incident on the optical crystal. A background intensity distribution obtained by detecting the second electromagnetic wave emitted from the optical crystal by being incident on the crystal is stored, a sample is placed in the observation range, and a pulse is applied to the observation range. The incident timing of the second electromagnetic wave with respect to the first electromagnetic wave is changed between the first electromagnetic wave and the second electromagnetic wave that are reflected in the observation range or transmitted through the observation range by irradiating a terahertz wave having a shape Incident on the optical crystal while acquiring the intensity distribution of the second electromagnetic wave emitted from the optical crystal, and the incident timing of the acquired intensity distribution. And subtracting the intensity distribution of the background stored in advance from the intensity distribution of the second electromagnetic wave stored for each incident timing of the second electromagnetic wave, or Corresponding to the size of the sample in the step of dividing and correcting, the step of Fourier transforming the corrected intensity distribution of the second electromagnetic wave for each incident timing of the second electromagnetic wave, and the Fourier transformed intensity distribution An incident timing setting method is provided that performs a step of selecting an incident timing at which a frequency component to be maximized is selected.

  According to the present invention, the intensity distribution of the background that is acquired as the second electromagnetic wave emitted from the optical crystal even when only the second electromagnetic wave is incident without the first electromagnetic wave being incident is stored. Since the intensity distribution of the second electromagnetic wave acquired by entering the first electromagnetic wave is corrected by the stored intensity distribution of the background, the background noise is determined from the corrected intensity distribution of the second electromagnetic wave. Has been removed. Then, by examining the frequency component intensity corresponding to the sample size by Fourier transforming the intensity distribution from which the background noise has been removed, it is possible to easily find the timing at which the intensity distribution of the sample portion changes abruptly. The Fourier transform component shows a curve in which the intensity decreases as the frequency increases. However, when the contrast is not good, the intensity decrease at high frequencies becomes large. The frequency at which the intensity decrease due to this contrast reduction is clearly observed becomes higher as the sample size becomes smaller. Therefore, by examining the intensity change of the frequency according to the sample size and selecting the timing at which the intensity is maximized. The incident timing of the second electromagnetic wave that can detect the boundary between the region where the sample exists and the region where the sample does not exist can be set.

  Further, the present invention provides a first irradiation unit that irradiates a first electromagnetic wave composed of a pulsed terahertz wave to an observation range including a sample, and the first that reflects in the observation range or transmits through the observation range. An optical crystal that makes the electromagnetic wave incident thereon, a second irradiation unit that makes the pulsed second electromagnetic wave having a wavelength shorter than the terahertz wave incident on the optical crystal, and the second emitted from the optical crystal The second electromagnetic wave incident from the second irradiation unit is reflected or reflected by the sample existing in the observation range. The phase of the electric field of the first electromagnetic wave transmitted through the region or the phase where one of the amplitude of the electric field of the first electromagnetic wave reflected in the region other than the sample within the observation range or transmitted through the region is larger than the other. Providing an observation device that is.

  In the above invention, the incident timing of the second electromagnetic wave is determined by the amplitude of the electric field of the first electromagnetic wave reflected or transmitted by the sample existing in the observation range or the observation range. It is preferable that the phase is set such that one of the amplitudes of the electric field of the first electromagnetic wave reflected or transmitted through the region other than the sample is substantially zero.

  According to the present invention, it is possible to observe a sample with high contrast in observation of an observation range including a region where the sample exists and a region where the sample does not exist.

It is a whole lineblock diagram showing the observation device concerning one embodiment of the present invention. FIG. 2 is a diagram illustrating (a) a terahertz wave before incidence on a sample and (b) a terahertz wave after passing through a stage in the observation apparatus of FIG. 1. 2 is a flowchart for explaining a method of setting the incident timing of near-infrared light to an electro-optic crystal in the observation apparatus of FIG. It is a whole block diagram which shows the 1st modification of the observation apparatus of FIG. It is a whole block diagram which shows the 2nd modification of the observation apparatus of FIG. It is a figure explaining the incident direction of the terahertz wave and near-infrared light in the observation apparatus of FIG. It is a whole block diagram which shows the 3rd modification of the observation apparatus of FIG. It is a figure explaining what performs sum frequency mixing or difference frequency mixing as an optical crystal of the observation apparatus of FIG. It is a flowchart explaining the 1st modification of the setting method of the incident timing of FIG. It is a flowchart explaining the 2nd modification of the setting method of the incident timing of FIG. It is a flowchart explaining the 3rd modification of the setting method of the incident timing of FIG.

An observation method, an incident timing setting method, and an observation apparatus 1 according to an embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the observation apparatus 1 according to the present embodiment includes a light source 2 that generates pulsed near-infrared light (for example, femtosecond pulsed laser light) L ₁ , and a near-red light from the light source 2. a beam splitter 3 which splits the external light L ₁ 2 one in the optical path, disposed in the optical path of one divided by the beam splitter 3, a terahertz wave irradiation optical system 4 for generating a terahertz wave L _2, on the other optical path The provided near-infrared light irradiation optical system 5, a stage 6 on which a sample A such as a cell disposed in the middle of the terahertz wave irradiation optical system 4 is placed, and these irradiation optical systems 4 and 5 are guided. A beam splitter 7 for combining the terahertz wave L ₂ and the near-infrared light L ₁ , an electro-optic crystal 8 disposed at the subsequent stage of the beam splitter 7, and a near-infrared light transmitted through the electro-optic crystal 8. and a detection optical system 9 for detecting the L ₁ Eteiru.

The terahertz wave irradiation optical system 4, a terahertz wave radiating element 11 for converting the near-infrared light L ₁ one of the near-infrared light L ₁ which is divided by the beam splitter 3 to the terahertz wave L _2, the terahertz wave A condenser lens 10 that converts the terahertz wave L ₂ radiated from the radiating element 11 into substantially parallel light, and a lens 12 that adjusts the beam diameter of the terahertz wave L ₂ transmitted through the sample A on the stage 6 are provided. Yes.

Near-infrared light irradiation optical system 5, and the other near-infrared light half-wave plate 15 to arrange the linearly polarized light the polarization state of the L ₁ of the divided near-infrared light L ₁ by the beam splitter 3, converting near-infrared light L optical path length adjusting optical system 13 for adjusting the optical path length between the beam splitter 3 and 7 of _1, substantially parallel light by increasing the near-infrared light L ₁ of the light flux diameter which is adjusted to the optical path The beam expander 14 is provided.

Optical path length adjusting optical system 13, and two movable mirrors 13a folding the near-infrared light L _1, and the fixed mirror 13b which is disposed opposite to one of the movable mirrors 13a, a movable mirror 13a is fixed mirror 13b A moving mechanism (not shown) for moving in the direction of arrow B is provided. By moving the movable mirror 13a with respect to the fixed mirror 13b, thereby making it possible to adjust the near-infrared light L ₁ phase.

Electro-optic crystal 8 by the terahertz wave L ₂ is irradiated, a nonlinear optical crystal distribution of the refractive index varies depending on the electric field state. For example, ZnTe: zinc telluride can be mentioned. By irradiating the electro-optic crystal 8 with the terahertz wave L ₂ having the spatial distribution of the electric field, the distribution of the electric field amplitude is written (reflected) as the refractive index distribution. When the near-infrared light L ₁ is passed through the written area, the polarization direction of the near-infrared light L ₁ can be changed. Since the written information disappears instantaneously, it is necessary to make the near-infrared light L ₁ incident on the electro-optic crystal 8 immediately after the terahertz wave L ₂ so that it can be read out immediately after the information is written.

The detection optical system 9 includes an imaging optical system 19 that forms an image of near-infrared light L ₁ that has passed through the electro-optic crystal 8, a polarizer 16 that is disposed orthogonal to the half-wave plate 15, and the polarization the near-infrared light L ₁ having passed through the child 16 and a CCD camera 17 for acquiring two-dimensional intensity distribution imaging. Here, the CCD camera 17 is disposed at a position optically conjugate with the sample A. Near-infrared light L ₁ is transmitted through the electro-optic crystal 8 terahertz wave L ₂ is irradiated, the polarization state becomes elliptically polarized because of the birefringence induced by the electric field of the terahertz wave L ₂ Yes. Therefore, by detecting only the near-infrared light L ₁ having passed through the polarizer 16, and it is capable of imaging only components whose polarization state has changed. In place of the CCD camera 17, a CMOS camera may be employed. In the figure, reference numeral 18 denotes a mirror, and reference numeral 27 denotes a condenser lens.

Further, the optical path length adjusting optical system 13 and the CCD camera 17 are provided with an incident timing of near-infrared light L ₁ described later output from the optical path length adjusting optical system 13 and the near-infrared light L output from the CCD camera 17. A storage unit 28 is connected to store _one intensity distribution in association with each other.

Here will be described the below incident timing of the near-infrared light L ₁ of the electro-optic crystal 8 in the observation apparatus 1 according to this embodiment.
As shown in FIG. 2 (a), before entering the sample A, the electric field phase and waveform of the respective portions of the terahertz wave L ₂ are almost the same. On the other hand, as shown in FIG. 2B, the phase of the terahertz wave L ₂ ′ that has passed through the sample A is compared with the terahertz wave L ₂ that has not passed through the sample A due to the refractive index of the sample A. Be late. Further, the waveform of the terahertz wave L ₂ ′ that has passed through the sample A is deformed by absorption in the sample A.

As a result, the phase of the terahertz wave L ₂ ′ that has passed through the sample A and the terahertz wave L ₂ that has not passed through the sample A are shifted in the time axis direction. 2B, the terahertz wave L ₂ ′ that has passed through the sample A at a position where the electric field amplitude of the terahertz wave L ₂ that has not passed through the sample A becomes substantially zero is large. There is a phase with an amplitude (eg, peak amplitude).

In the electro-optic crystal 8, the refractive index is changed depending on the electric field amplitude of the incident terahertz waves L ₂ and L ₂ ′. Therefore, in the phase where the electric field amplitude of one terahertz wave L ₂ is almost zero. Only the change in refractive index due to the other terahertz wave L ₂ ′ occurs. Therefore, the refractive index of the other terahertz wave L ₂ ′ is substantially extinguished by making the near-infrared light L ₁ incident at a timing coincident with the phase so that the refractive index change due to the one terahertz wave L ₂ is substantially extinguished. only it can be superimposed on the near-infrared light L ₁ information changes, so that it can be detected by the detection optical system 9 such near-infrared light L _1.

An observation method using the observation apparatus 1 according to the present embodiment configured as described above will be described below.
In order to observe the sample A such as a transparent cell using the observation apparatus 1 according to the present embodiment, the sample A is placed on the stage 6 and the pulsed near-infrared light L ₁ is emitted from the light source 2. Let

The near-infrared light L ₁ branched by the beam splitter 3 and incident on the terahertz wave irradiation optical system 4 is deflected by the mirror 18, condensed by the condenser lens 27, and passed through the terahertz wave radiating element 11. Thus, after being converted into the terahertz wave L ₂ and converted into substantially parallel light by the lens 10, the observation range including the sample A on the stage 6 is irradiated.

In the region where the sample A in the observation range is present, the terahertz wave L ₂ is retarded phase by the refractive index of the sample A, the the waveform by the absorption of the sample A was modified terahertz wave L _{2 '.} On the other hand, in the region where the sample A is not present, the terahertz wave L ₂ is as it is transmitted without modification of the phase delay and waveform. The terahertz wave L ₂ is adjusted in its beam diameter by the lens 12.

The sample A is a transparent cell or the like, but the terahertz wave L ₂ ′ transmitted through the sample A is modulated by the sample A and has a distribution of the electric field amplitude corresponding to the refractive index and absorption distribution in the sample A. It becomes like this. When the terahertz waves L ₂ and L ₂ ′ having the electric field amplitude distribution superimposed on the information of the sample A by being transmitted through the observation range are incident on the electro-optic crystal 8, A refractive index distribution corresponding to the electric field amplitude distribution of the terahertz waves L ₂ and L ₂ ′ is generated.

On the other hand, the near-infrared light L ₁ branched by the beam splitter 3 and incident on the near-infrared light irradiation optical system 5 is transmitted through the half-wave plate 15, thereby causing birefringence in the electro-optic crystal 8. The direction of rotation of the linearly polarized light is set so that the polarization state changes at this time. The phase of the near-infrared light L ₁ whose polarization state is set is adjusted by the optical path length adjusting optical system 13, the beam diameter is expanded by the beam expander 14, and the terahertz wave is output by the beam splitter 7. The light is merged into the same optical path as L ₂ and L ₂ ′ and is incident on the electro-optic crystal 8.

In this case, in the present embodiment, by adjusting the optical path length of near-infrared light irradiation optical system 5 by the optical path length adjusting optical system 13, the incident timing of the electro-optic crystal 8 of the near-infrared light L ₁ It has been adjusted. That is, the near-infrared light L ₁ has substantially zero electric field amplitude of the terahertz wave L ₂ incident on the electro-optic crystal 8 without passing through the sample A, and passes through the sample A and enters the electro-optic crystal 8. The terahertz wave L ₂ ′ is incident on the electro-optic crystal 8 at a timing substantially coincident with the phase at which the electric field amplitude becomes sufficiently large.

Thereby, a change in the refractive index of the electro-optic crystal 8 due to the terahertz wave L ₂ incident on the electro-optic crystal 8 without passing through the sample A is suppressed, and the terahertz wave L incident on the electro-optic crystal 8 after passing through the sample A is suppressed. _The refractive index distribution by ₂ ′ alone, that is, the refractive index distribution of the sample A can be accurately read out by the near-infrared light L ₁ .

The near-infrared light L ₁ on which the information on the refractive index distribution of the sample A is superimposed by being transmitted through the electro-optic crystal 8 is allowed to pass through the polarizer 16, so that only the component changed by the electro-optic crystal 8 is transmitted. Is extracted by the CCD camera 17. Thereby, an image of the observation range including the sample A is acquired. In this the image, the influence of the terahertz wave L ₂ having passed through the region in which sample A is not present have been removed, with high contrast, it is possible to perform a clear observation of the sample A.

Next, the incident timing setting method of the near-infrared light L ₁ of the electro-optic crystal 8 in the observation method will be described below with reference to FIG.
The incident timing setting method according to the present embodiment includes a step of acquiring data without sample A performed without placing the sample A on the stage 6, and acquisition of data with sample A performed by placing the sample A on the stage 6. a method, based on the acquired sample a has data and sample a without data, and a timing calculation step of calculating the timing of incidence of near-infrared light L _1.

Since the acquisition step of data without sample A and the acquisition step of data with sample A are the only differences between whether or not sample A is placed, here, the acquisition step of data without sample A will be described. Description of the acquisition step is omitted.
In the step of acquiring data without sample A, the terahertz wave L ₂ and the near-infrared light L ₁ are made incident on the electro-optic crystal 8 in a state where the sample A is not placed in the observation range (step S1), and the optical path length adjusting optical system 13 is operated to obtain the intensity distribution of the near infrared light L ₁ while shifting the incident timing of the near infrared light L ₁ with respect to the terahertz wave L ₂ .

Specifically, in the step of acquiring the data without sample A, the step of initializing the incident timing of the near-infrared light L ₁ , the terahertz wave L ₂ transmitted through the observation range, and the near-infrared light L ₁ are electrically connected. the incident step S3 to be incident on the optical crystal 8, the intensity distribution obtaining step S4 to acquire to the intensity distribution imaging the near-infrared light L ₁ having passed through the electro-optic crystal 8 by the CCD camera 17, the near-infrared acquired If the storage step S5 of storing the intensity distribution of the light L ₁ in the storage unit 28 together with the incident timing of the time, it is determined whether or not was acquired intensity distribution at all of the incident timing, not completed, The timing variation step S6 in which the optical path length adjusting optical system 13 is operated to shift the incident timing by a predetermined variation range, and steps S3 to S6 are performed over a predetermined incident timing range. And a repeating step S7 to repeat.

  In the step of acquiring data with sample A, after the step of acquiring data without sample A, it is confirmed whether or not sample A is placed (step S8). If sample A is not placed, sample A is obtained. Is placed (step S9), and steps S2 to S7 are repeated.

Timing calculation step, for each incident timing of the near-infrared light L _1, near infrared storing the intensity distribution of the near-infrared light L ₁ stored in acquisition step without Sample A data, the acquisition step of the sample A with data by using the intensity distribution of the external light L _1, the subtraction or one one from the other and a correction step S10 of correcting by dividing the other hand, in the corrected near intensity distribution of the infrared light L _1, the maximum intensity It includes a calculation step S11 for calculating the absolute value of the difference from the minimum intensity, and a selection step S12 for selecting the incident timing at which the calculation result is the largest.

Then, the thus By performing the observation by setting the incident timing is selected, it is possible to observe the high contrast with reduced influence of the terahertz wave L ₂ having passed through the region in which sample A is not present.

As described above, according to the observation apparatus 1 and the observation method according to the present embodiment, the transparent sample A such as cells arranged in the observation range is distinguished from the region that is not the sample A, and a clear observation is performed with high contrast. There is an advantage that you can.
Further, according to the incident timing setting method according to the present embodiment, the near-incident timing of the infrared light L ₁ for use in the observation method can be set easily, to be implemented easily observed with high contrast Can do.

In the present embodiment, the near infrared at a timing at which the electric field amplitude is the peak of the electric field amplitude of the terahertz wave L ₂ that is not transmitted through the sample A becomes substantially zero, and the terahertz wave L ₂ transmitted through the sample A _' The light L ₁ is incident on the electro-optic crystal 8. Alternatively, the electric field amplitude of the terahertz wave L ₂ that is not transmitted through the sample A becomes a peak, the near-infrared light L ₁ at timing when the electric field amplitude is substantially zero in the terahertz wave L _{2 'transmitted} through the sample A The light may enter the electro-optic crystal 8.

In the present embodiment, the timing at which one of the electric field amplitudes of the terahertz wave L ₂ not transmitted through the sample A or the terahertz wave L ₂ ′ transmitted through the sample A is substantially zero is selected. Even when the electric field amplitude does not become exactly zero, a timing at which the amplitude is sufficiently low with respect to the other may be adopted.

In the present embodiment, the optical path length adjusting optical system 13 is disposed in the near infrared light irradiation optical system 5 and the optical path length of the near infrared light irradiation optical system 5 is adjusted, so that the terahertz wave L _{2 is} reduced. was decided to adjust the incident timing of the near-infrared light L _1, and or together with this alternative, it may be to place the terahertz wave irradiation optical system 4 optical path length adjustment optics (not shown).

  In the present embodiment, as shown in FIGS. 4 to 8, a placement surface 8 a on which the sample A is placed may be provided on the surface of the electro-optic crystal 8. In FIG. 4, reference numeral 20 is a condenser lens, reference numerals 21 and 22 are parabolic mirrors, reference numeral 23 is an objective lens, reference numeral 24 is a quarter-wave plate, reference numeral 25 is a polarizer, and reference numeral 26 is an imaging lens. . 4, 5, and 7, the optical path length adjusting optical system 13 includes triangular prisms 13 a ′ and 13 b ′.

With this configuration, the terahertz wave L ₂ can be incident on the electro-optic crystal 8 immediately after passing through the sample A, and observation can be performed with high resolution without being limited in spatial resolution by the optical system. There is an advantage that you can. As a result, even a sample A as small as a cell can be observed with high accuracy with a simple configuration and high spatial resolution.

Further, by transmitting terahertz wave L ₂ on the mounting surface 8a of the electro-optic crystal 8 as shown in FIGS. 5 and 6, by placing a reflective film 27 that reflects near-infrared light L _1, the terahertz wave L ₂ and it may be possible to configure the direction of incidence of the near-infrared light L ₁ of the electro-optic crystal 8 in the reverse direction. In this way, since the near-infrared light L ₁ is not transmitted through the sample A, the near-infrared light L ₁ is not modulated by the sample A for reading, by the terahertz wave L _2, indicated by oblique lines E in FIG. 6 Information written in the region of the electro-optic crystal 8 can be read more accurately.

Further, as shown in FIG. 7, a confocal observation apparatus may be configured.
In the example shown in FIG. 7, in the middle of the near-infrared light irradiation optical system 5 of an observation apparatus 1 of FIG. 5, it provided the scanner (proximity galvanometer mirror) 30 for scanning the near-infrared light L ₁ is two-dimensionally, the objective A confocal pinhole 31 is disposed at a position optically conjugate with the focal position of the lens 23. Thus, the near-infrared light L ₁ only the light detector from the region E of the mounting face 8a vicinity of the electro-optic crystal 8 the focal position of the objective lens 23 is disposed (e.g., photomultiplier tube) by 32 Can be detected. Therefore, a clear image can be obtained even if the electro-optic crystal 8 itself is configured to be relatively thick.

In each of the above-described embodiments, the electro-optic crystal 8 has been described as an example of the optical crystal. Instead, when two types of light L ₁ and L ₂ having different wavelengths are incident at the same time, A nonlinear optical crystal 8 ′ in which two lights L ₁ and L ₂ are sum frequency mixed or difference frequency mixed and another light L ₃ having the frequency of the sum or difference of the frequencies is emitted may be employed. By doing so, for example, in the case of sum frequency mixing, in the observation apparatus 1 shown in FIG. 1, the terahertz wave L ₂ and the near-infrared light L ₁ are simultaneously incident on the sample A and the nonlinear optical crystal 8 ′. Then, as shown in FIG. 8, the near-infrared light L ₁ that is not so modulated with the terahertz wave L ₂ (for example, wavelength 3 mm, frequency 0.1 THz) modulated according to the refractive index distribution of the sample A. (For example, wavelength 800 nm) is sum frequency mixed in the nonlinear optical crystal 8 ′, and the sum frequency mixed light L ₃ having another wavelength (for example, wavelength 799.79 nm) including information on the refractive index distribution of the sample A is the objective lens. 23 collects light. Therefore, an image of the sample A can be acquired by detecting this.

In each of the above embodiments, the terahertz wave L ₂ that has passed through the sample A is detected. Alternatively, the terahertz wave L ₂ reflected by the sample A is incident on the electro-optic crystal 8 or the nonlinear optical crystal 8 ', may measure the electric field waveform. In this way, in the case where the terahertz wave L ₂ is not transmitted through the sample A, it becomes possible to perform the measurement.

In the incident timing setting method according to the present embodiment, each time the observation, association and stores the near intensity distribution of the infrared light L ₁ when no mounting a sample A was obtained for each incident timing, Thereafter, it was decided to store in association to obtain the intensity distribution of the near-infrared light L ₁ to each incident timing when mounting a sample a. Alternatively, in advance, it may be previously created a database storing correspondence obtains the intensity distribution of the near-infrared light L ₁ to each incident timing when no mounting a sample A. In this case, as shown in FIG. 9, the sample A-less data acquisition step is omitted and the sample A is placed from the beginning (step S21). Instead, the sample A is placed from the database before correction. it may be set to be read out near the intensity distribution of the infrared light L ₁ when no location (step S22).

If the region where the sample A exists within the observation range and the region where the sample A does not exist can be distinguished in advance, as shown in FIG. 10, the near infrared light L stored in step S5 is stored. from one of the intensity distribution of the _first intensity distribution, the sample to obtain the intensity value of any position corresponding to the region where the sample a is not present, the intensity distribution of the intensity values and intensity values of all the positions You may generate | occur | produce artificially as an intensity distribution in case A does not exist (step S23). In this way, it is possible to set the incident timing for easily observing with good contrast while omitting acquisition of the intensity distribution when the sample A is not present.

Further, as shown in FIG. 11, the terahertz wave L ₂ only near-infrared light L ₁ without incident by incident on the electro-optic crystal 8, the electro-optic crystal 8 near infrared transmitted through the external light L ₁ The intensity distribution of the background may be stored in advance by imaging. In this case, after obtaining the intensity distribution of the near-infrared light L ₁ of each of all the incident timing, reads the intensity distribution of the background stored in advance (step S24), and the near-infrared light L ₁ for each timing of incidence, the intensity distribution of background read from the intensity distribution of the near-infrared light L ₁ that has been stored and corrected subtraction or division to (step S25), and the corrected intensity distribution Fourier transform ( In step S26), the timing at which the frequency component corresponding to the sample size becomes the largest in the Fourier-transformed intensity distribution may be selected (steps S11 and S12).

  By doing so, it is possible to perform observation in which a region where a high frequency component exists, for example, the outline of the sample A is clearly highlighted. In addition, in the image in which the sample can be observed with good contrast, the intensity of the frequency corresponding to the size of the sample is strong. Therefore, the timing at which the contrast is improved can be selected by searching for a position where the intensity is high. Since the corresponding frequency differs depending on the size of the sample, when there are a plurality of samples, a specific sample can be observed with high contrast by selecting the frequency to be searched.

  In this case, since impurities such as dust may also stand out, in this case, a low-pass filter may be used together to eliminate high frequency components above a predetermined level. In addition to this, a high-pass filter and a band-pass filter may be used in combination.

A Sample L ₁ Near infrared light (second electromagnetic wave)
L ₂ terahertz wave (first electromagnetic wave)
1 observation device 4 terahertz wave irradiation optical system (first irradiation unit)
5 Near-infrared light irradiation optical system (second irradiation unit)
8 Electro-optic crystal (optical crystal)
8 'Nonlinear optical crystal (optical crystal)
8a Mounting surface 9 Detection optical system

Claims (8)

By irradiating the observation range including the sample with a pulsed terahertz wave, the first electromagnetic wave reflected or transmitted through the observation range and the pulsed second having a shorter wavelength than the terahertz wave Injecting the electromagnetic wave into the optical crystal;
Detecting the second electromagnetic wave emitted from the optical crystal,
The second electromagnetic wave is reflected in the sample existing in the observation range or transmitted through the sample. The amplitude of the electric field of the first electromagnetic wave reflected or transmitted through the region other than the sample in the observation range. An observation method in which one of the amplitudes of the electric field of one electromagnetic wave is incident on the optical crystal at a timing that is arranged in a phase larger than the other.   The second electromagnetic wave is reflected in the sample existing in the observation range or transmitted through the sample. The amplitude of the electric field of the first electromagnetic wave reflected or transmitted through the region other than the sample in the observation range. The observation method according to claim 1, wherein the optical crystal is incident on the optical crystal at a timing at which one of the amplitudes of the electric field of the electromagnetic wave is arranged at a phase where the amplitude is substantially zero. A method for setting the timing of incidence of the second electromagnetic wave in the observation method according to claim 1 or 2,
By irradiating the observation range with a pulsed terahertz wave, the second electromagnetic wave is reflected in the observation range or transmitted through the observation range, and the second electromagnetic wave is applied to the second electromagnetic wave. Changing the incident timing of the electromagnetic wave to the optical crystal, acquiring the intensity distribution of the second electromagnetic wave emitted from the optical crystal, and associating the acquired intensity distribution with the incident timing After performing the storing step when the sample is arranged within the observation range and when the sample is not arranged,
At each timing of incidence of the second electromagnetic wave, one of the intensity distribution of the second electromagnetic wave stored without arranging the sample and the intensity distribution of the second electromagnetic wave stored with the sample arranged is subtracted from the other or Incidence performing a step of correcting by dividing one by the other and a step of selecting an incident timing at which the absolute value of the difference between the maximum intensity and the minimum intensity is the largest in the corrected intensity distribution of the second electromagnetic wave Timing setting method. A method for setting the timing of incidence of the second electromagnetic wave in the observation method according to claim 1 or 2,
By irradiating the observation range with a pulsed terahertz wave without arranging a sample in the observation range, the first electromagnetic wave reflected in or transmitted through the observation range and the second electromagnetic wave Is incident on the optical crystal while changing the incident timing of the second electromagnetic wave with respect to the first electromagnetic wave, the intensity distribution of the second electromagnetic wave emitted from the optical crystal is acquired, and the acquired intensity distribution Is stored in a database in association with the incident timing,
A step of arranging a sample in the observation range and irradiating the observation range with a pulsed terahertz wave; and the first electromagnetic wave and the second electromagnetic wave reflected or transmitted through the observation range in the observation range; To the optical crystal while changing the incident timing of the second electromagnetic wave with respect to the first electromagnetic wave, acquiring the intensity distribution of the second electromagnetic wave emitted from the optical crystal, and And storing the intensity distribution in association with the incident timing,
At each incident timing of the second electromagnetic wave, one of the intensity distribution of the second electromagnetic wave stored in the database and the intensity distribution of the second electromagnetic wave stored by arranging the sample is subtracted from the other or The timing of performing the correction by dividing the value by the other and the step of selecting the incident timing at which the absolute value of the difference between the maximum intensity and the minimum intensity is the largest in the corrected intensity distribution of the second electromagnetic wave Setting method. A method for setting the timing of incidence of the second electromagnetic wave in the observation method according to claim 1 or 2,
The first electromagnetic wave reflected in the observation range or transmitted through the observation range by placing a sample in the observation range and irradiating the observation range with a pulsed terahertz wave, and the second electromagnetic wave To the optical crystal while changing the incident timing of the second electromagnetic wave with respect to the first electromagnetic wave, acquiring the intensity distribution of the second electromagnetic wave emitted from the optical crystal, and And storing the intensity distribution in association with the incident timing,
Based on the intensity of any of the second electromagnetic waves emitted from the optical crystal corresponding to the area where the sample does not exist in the obtained intensity distribution of the second electromagnetic wave, Generating an electromagnetic wave intensity distribution of 2;
Correcting by subtracting the other from one of the intensity distribution of the second electromagnetic wave stored and the intensity distribution of the second electromagnetic wave when the generated sample is not placed or dividing one by the other;
And a step of selecting an incident timing at which an absolute value of a difference between the maximum intensity and the minimum intensity is the largest in the corrected intensity distribution of the second electromagnetic wave. A method for setting the timing of incidence of the second electromagnetic wave in the observation method according to claim 1 or 2,
The intensity of background obtained by detecting the second electromagnetic wave emitted from the optical crystal by making the second electromagnetic wave incident on the optical crystal without causing the first electromagnetic wave to be incident on the optical crystal. Remember the distribution,
The first electromagnetic wave and the second electromagnetic wave that are reflected in the observation range or transmitted through the observation range by placing a sample in the observation range and irradiating the observation range with a pulsed terahertz wave. Changing the incident timing of the second electromagnetic wave with respect to the first electromagnetic wave, changing the incident timing to the optical crystal, acquiring the intensity distribution of the second electromagnetic wave emitted from the optical crystal, and the acquired intensity And storing the distribution in association with the incident timing,
Subtracting or dividing the intensity distribution of the background stored in advance from the intensity distribution of the second electromagnetic wave stored for each incident timing of the second electromagnetic wave;
Fourier transforming the acquired intensity distribution after correction for each incident timing of the second electromagnetic wave;
Selecting an incident timing at which a frequency component corresponding to the size of the sample is maximized in the Fourier-transformed intensity distribution. A first irradiation unit that irradiates a first electromagnetic wave composed of a pulsed terahertz wave with respect to an observation range including a sample;
An optical crystal that makes the first electromagnetic wave reflected or transmitted through the observation range incident on the observation range;
A second irradiating unit for injecting a pulsed second electromagnetic wave having a shorter wavelength than the terahertz wave toward the optical crystal;
A detection unit for detecting the second electromagnetic wave emitted from the optical crystal,
The incident timing of the second electromagnetic wave emitted from the second irradiation unit reflects the amplitude of the electric field of the first electromagnetic wave reflected or transmitted through the sample existing within the observation range, or the sample within the observation range. An observation apparatus in which one of the amplitudes of the electric field of the first electromagnetic wave reflected in or transmitted through the region other than is set to a phase larger than the other.   The incident timing of the second electromagnetic wave is reflected in a sample existing in the observation range or reflected in the region of the first electromagnetic wave transmitted through the sample or reflected in the region other than the sample in the observation range. The observation apparatus according to claim 7, wherein one of the amplitudes of the electric field of the transmitted first electromagnetic wave is set to a phase that is substantially zero.

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