JP2023128431A - Optical measurement device and optical measurement method - Google Patents

Abstract

To improve measurement accuracy of high-speed change in an object.SOLUTION: An optical measurement device (10) includes: a first phase plate (13a); a second phase plate (13b) opposed to the first phase plate across an object (OB); and an analyzer (12b) on which polarized light emitted from the second phase plate is incident. The first phase plate decomposes the incident polarized light into first and second polarized light (W2a, W2b) and emits them with predetermined time difference (ΔT). The second phase plate eliminates the predetermined time difference.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical measurement device and an optical measurement method.

Various techniques have been developed to observe and measure high-speed phenomena. For example, strobe photography is commonly used to photograph an object by repeatedly emitting instantaneous light. However, strobe photography does not necessarily have a high time resolution, and it is difficult to measure extremely high-speed phenomena on the order of f (femto) seconds (10 ⁻¹⁵ seconds), for example. An example of such an ultrafast phenomenon is the behavior of plasma generated by laser irradiation. Non-Patent Document 1 discloses a technique for measuring plasma behavior using two temporally separated probe lights generated by a Michelson interferometer.

“Single-shot two-dimensional spectral interferometry for ultrafast laser-produced plasmas” Y. Hama, K. Kondo, Z. Zoubir et al., Optics letters 31 1917 (2006).

However, the technique of Non-Patent Document 1 lacks accuracy and stability of the time delay between the two probe lights. Furthermore, since an ultra-narrow band interference filter is used to omit temporal recombination, the contrast of the obtained image cannot be said to be good.

An object of one aspect of the present invention is to provide an optical measurement device and an optical measurement method that improve the accuracy of measuring high-speed changes in a target object.

In order to solve the above problems, an optical measurement device according to one aspect of the present invention is an optical measurement device that optically measures temporal changes in an object, and includes a first phase plate into which polarized light is incident. a second phase plate that faces the first phase plate with the object in between, and into which the polarized light emitted from the first phase plate and that has passed through the object is incident; an analyzer into which the polarized light emitted from the second phase plate is incident; The second phase plate eliminates the predetermined time difference between the first and second polarized lights and outputs a composite polarized light that is a combination of the first and second polarized lights.

According to one aspect of the present invention, it is possible to provide an optical measuring device and an optical measuring method that improve the accuracy of measuring high-speed changes in a target object.

1 is a diagram illustrating an optical measurement device according to an embodiment of the present invention. FIG. 2 is an enlarged view of a part of the optical measurement device. FIG. 2 is a diagram illustrating an optical measurement device for observing laser wake generated by laser irradiation. It is a figure showing the result of photographing a laser wake. FIG. 3 is a diagram showing the intensity distribution of laser wake.

Embodiments of the present invention will be described below. FIG. 1 depicts an optical measurement device 10 according to an embodiment of the invention. The optical measurement device 10 is an optical measurement device that optically measures temporal changes in the object OB, and functions, for example, as a microscope that magnifies and displays the object OB.

The object OB can change at extremely high speed (for example, on the order of f (femto) seconds, on the order of 10 f seconds or less). An example of the object OB is a laser wake. A laser wake is a compression wave of electron plasma that is generated by irradiating a gas with ultra-intense laser light and follows the propagation path of the laser light. The density state of the laser wake changes in extremely short time intervals. This time interval (change time Tc) is, for example, 15 [f seconds].

The optical measuring device 10 includes a light source 11, a polarizer (polarizing plate) 12a, an analyzer (polarizing plate) 12b, phase plates 13a, 13b, lenses 14a to 14d, a filter 15, and an imager 16. Note that XYZ coordinates are set in which the direction of the optical axis A of the laser beam L0 is the Z axis.

The light source 11 emits laser light L0. The light source 11 can be a continuous wave (CW) laser or a pulsed laser. As the pulse laser, for example, a titanium (Ti) sapphire laser (hereinafter referred to as "TiS laser") can be used. A TiS laser can generate linearly polarized light with a wide band and short pulses by utilizing the nonlinear optical effect of gas.

A polarizer 12a, a phase plate 13a, an object OB, a lens 14a, a phase plate 13b, an analyzer 12b, lenses 14b to 14d, a filter 15, and an imager 16 are arranged in this order on the optical axis A of the laser beam L0. .

The polarizer 12a and the analyzer 12b pass the linearly polarized component contained in the incident light. The polarizer 12a and the analyzer 12b have polarization axes Da and Db, respectively, and pass linearly polarized light in a polarization direction parallel to the polarization axes Da and Db. The analyzer 12b functions as an analyzer into which the polarized light L3 emitted from the phase plate 13b (second phase plate) is incident.

The polarization axis Da of the polarizer 12a is along the polarization direction of the laser beam L0 emitted from the light source 11. The polarizer 12a is installed in front of the light source 11, and removes a polarization component (polarization noise) perpendicular to the polarization axis Da included in the laser light L0.

The polarization axis Db of the analyzer 12b is orthogonal to the polarization axis Da of the polarizer 12a. The angle between the polarization axes Da and Db is, for example, in the range of 90°±12°. Here, for ease of understanding, the polarization axis Da of the polarizer 12a is the Y-axis direction, and the polarization axis Db of the analyzer 12b is the X-axis direction.

The polarizer 12a and the analyzer 12b can be made of, for example, a thin film or dichroic glass. As explained below, when a pulsed laser is used as the light source 11, it is preferable that the polarizer 12a and the analyzer 12b are a thin film polarizing plate and a dichroic glass polarizing plate, respectively.

The reason why the polarizer 12a is a thin film polarizing plate is to maintain the pulse width of the laser beam L1 after exiting the polarizer 12a. In other words, when the polarizer 12a is made of dichroic glass, the pulse waveform of the laser beam is distorted in the polarizer 12a, and the pulse width of the laser beam L1 emitted from the polarizer 12a becomes wider than the original pulse width of the laser beam L0. There is a tendency. This widening of the pulse width may impede observation of the object OB at ultra-high speed. This is because, as will be described later, the pulse width PW of the laser beam is preferably equal to or less than the change time Tc of the object OB. That is, if the pulse width becomes wider and becomes longer than the change time Tc, observation of the object OB at ultra-high speed will be hindered.

The reason why the analyzer 12b is made of dichroic glass is to improve the contrast of the image by using dichroic glass that has good polarized light extraction properties. Unlike the polarizer 12a, the broadening of the pulse width caused by the analyzer 12b does not impede observation of the object OB at ultrahigh speed. The pulse width of the laser beam becomes a problem when it passes through the object OB, and even if the pulse width widens after passing through the object OB, it does not affect the observation of the object OB.

Note that, as long as the influence on the pulse width of the laser beam L0 from the light source 11 is small, a member other than the thin film polarizing plate may be used as the polarizer 12a.

The above is a description of the case where a pulsed laser having an extremely narrow pulse width (for example, on the order of f seconds) is used as the light source 11. When a light source with a pulse width wider than a certain level is used as the light source 11, or when a CW laser is used, appropriate materials can be used for the polarizer 12a and the analyzer 12b. For example, both the polarizer 12a and the analyzer 12b may be dichroic glass polarizing plates.

The phase plates 13a and 13b are made of an anisotropic birefringent material (eg, birefringent crystal) and impart a phase difference to incident light. The phase plate 13a functions as a first phase plate into which the polarized light L1 is incident. The phase plate 13b faces the phase plate 13a (first phase plate) with the object OB in between. The phase plate 13b functions as a second phase plate into which the polarized light L2 that is emitted from the phase plate 13a (first phase plate) and has passed through the object OB is incident.

The phase plate 13a imparts a phase difference ΔF (time difference ΔT) to the incident light. On the other hand, the phase plate 13b eliminates (reduces) the phase difference ΔF (time difference ΔT) imparted to the incident light. As will be described later, the phase plate 13a decomposes the incident polarized light L1 into polarized light W2a and W2b (first and second polarized light, see FIG. 2 described later), and divides the incident polarized light L1 into polarized light W2a and W2b (first and second polarized light, see FIG. 2 described later), and then divides the incident polarized light L1 into polarized light W2a and W2b (first and second polarized light, see FIG. 2 to be described later), and divides the input polarized light L1 into polarized light W2a and W2b (first and second polarized light, see FIG. 2, which will be described later). Emits light. In addition, the phase plate 13b eliminates the time difference ΔT (predetermined time difference) between the polarized lights W2a and W2b (first and second polarized lights), and generates a polarized light L3 (synthesized polarized light) which is a combination of the first and second polarized lights. is emitted.

The phase difference ΔF and time difference ΔT provided by the phase plate 13a are defined by the following equations (1) and (2).
ΔF=(2π・Δn・d)/λ... Formula (1)
ΔT=c/(Δn・d)... Formula (2)
λ: Wavelength of laser beam L0 (center wavelength)
Δn: (anisotropic) refractive index difference (=ne-no) of the phase plate 13a
ne: refractive index in the anisotropic axis Sa direction of the phase plate 13a
(Refractive index for polarized light W2a (first polarized light) described below)
no: refractive index in the direction perpendicular to the anisotropy axis Sa
(Refractive index for polarized light W2b (second polarized light) described below)
d: Thickness of phase plate 13a c: Speed of light

In order to eliminate (reduce) the phase difference ΔF (time difference ΔT), the phase plate 13b provides a phase difference ΔF2 and a time difference ΔT2 with substantially the same absolute value and opposite signs to the phase difference ΔF and time difference ΔT. (ΔF+ΔF2≒0, ΔT+ΔT2≒0). That is, the product "Δn·d" of the anisotropic refractive index difference Δn and the thickness d of the phase plates 13a and 13b is approximately equal, and the anisotropy axis Sb of the phase plate 13b is the anisotropy of the phase plate 13a. It is set to be substantially perpendicular to the axis Sa.

Note that the anisotropic axis Sa of the phase plate 13a forms an angle θa of approximately 45° with respect to the polarization axis Da (here, the Y axis) of the polarizer 12a, and the anisotropic axis Sb of the phase plate 13b , forms an angle -θb (θa+θb≈90°) with respect to the polarization axis Da (here, Y-axis) of the polarizer 12a.

Preferably, the phase plates 13a and 13b are made of the same material and have the same thickness. This is to ensure that the phase difference is imparted and eliminated by using materials with the same characteristics including wavelength dependence. As this material, for example, quartz can be used. For example, when the wavelength λ of the laser beam L0 is 800 [nm], the phase plates 13a and 13b can be made of 180 μm thick quartz crystal, and the phase difference ΔF can be approximately 4π (equivalent to 2λ). .

The lens 14a is arranged between the object 0B and the phase plate 13b (second phase plate), and functions as an objective lens for enlarging and representing the object 0B. As the lens 14a, for example, a lens with a magnification of several times to several hundred times (for example, a corrected magnification of 10 times at infinity) can be used.

The lens 14b is, for example, a tube lens, and is combined with the lens 14a (objective lens) to form an image of the object OB.

Lenses 14c and 14d are lenses for transferring images formed by lenses 14a and 14b, and are used when the distance between lens 14b and image pickup device 16 is large.

The filter 15 is a narrow band filter for removing external light other than the laser beam L0 from the light source 11, and has a wavelength characteristic that allows light with a wavelength λ of the laser beam L0 to pass through and does not pass light with a wavelength other than the wavelength λ. has. By narrowing the bandwidth of the filter 15 to, for example, 10 nanometers (full width at half maximum), the S/N ratio of measurement can be improved.

The imager 16 is an image sensor that images temporal changes in the object OB. The imager 16 records an image representing a temporal change of the object OB, which is formed using polarized light having a time difference ΔT.

(Operation of optical measurement device 10)
The operation of the optical measurement device 10 will be explained below. FIG. 2 is an enlarged view of the vicinity of the phase plates 13a and 13b. In particular, the vicinity of the phase plates 13a and 13b is shown enlarged. FIG. 2(a) is a perspective view corresponding to FIG. 1, and FIG. 2(b) is a schematic diagram showing a state in which FIG. 2(a) is viewed from the side. Hereinafter, the operation of the optical measuring device 10 will be explained based on FIG. 2. Note that the lens 14a is omitted from FIG. 2 because it does not substantially affect the transition of the laser beams L1 to L4, which will be described below.

As described above, the laser beam L1 that is emitted from the light source 11 and passes through the polarizer 12a is incident on the polarizer 12a. Specifically, the laser beam L1 is polarized light (electromagnetic wave) W1 having an electric field that oscillates in the direction of the polarization axis Da of the polarizer 12a (here, the Y-axis direction).

The polarized light W1 incident on the phase plate 13a is separated into two polarized lights W2a and W2b, each having two different vibration directions, and is emitted. The polarized light W2a vibrates in the direction of the anisotropic axis Sa of the phase plate 13a, and the polarized light W2b vibrates in the direction perpendicular to the anisotropic axis Sa (here, the direction of the anisotropic axis Sb of the phase plate 13b). do. The polarized lights W2a and W2b have a time difference ΔT defined by the phase plate 13a. That is, the polarized light W2b is first emitted from the phase plate 13a, and then, after the time difference ΔT has elapsed, the polarized light W2a is emitted from the phase plate 13a.

The polarized lights W2a and W2b emitted from the phase plate 13a sequentially pass through the object OB and reach the phase plate 13b. Here, both cases are considered: (1) the state of the object OB does not change and (2) the state of the object OB changes during the time difference ΔT.

When the state of the object OB does not change during the time difference ΔT, the polarized lights W2a and W2b incident on the phase plate 13b are combined after the time difference ΔT is eliminated. As a result, polarized light W3 (combined polarized light) is emitted from the phase plate 13b. This polarized light W3 has the same polarization state as the polarized light W1 before being given a phase difference by the phase plate 13a. This polarized light W3 enters the analyzer 12b, and a polarized light W4 vibrating in the direction of the polarization axis Db of the analyzer 12b is output. Here, the polarized light W3 is linearly polarized light that vibrates in the direction of the polarization axis Da and does not have a vibration component in the direction of the polarization axis Db, so the intensity of the polarized light W4 is substantially zero.

On the other hand, when the state (for example, refractive index, transmittance) of the object OB changes during the time difference ΔT, this change imparts a phase difference and an intensity difference to the polarized lights W2a and W2b. Therefore, even if the time difference ΔT is canceled and the polarized lights W2a and W2b incident on the phase plate 13b are combined, they become a polarized light W3a different from the polarized light W3. This polarized light W3a is generally elliptically polarized light, unlike W3 which is linearly polarized light. That is, the polarized light W3a has a vibration component in the direction of the polarization axis Db, that is, an amplitude ΔIx in the direction of the polarization axis Db. As a result, the polarized light W3a that has entered the analyzer 12b is emitted as polarized light W4a having an amplitude ΔIx.

As described above, the intensity of the polarized light W4 (W4a) changes according to the change in the state of the object OB with the time difference ΔT. Thereby, the state change of the object OB with the time difference ΔT is measured. That is, the polarized light W3 (combined polarized light) has at least one of a phase difference or an intensity difference, which corresponds to a change in the object OB with a time difference ΔT (predetermined time difference), with respect to the polarized light L1. As a result, the optical measuring device 10 measures a temporal change in the object OB on the order of a time difference ΔT (predetermined time difference) or less.

Note that this phase difference corresponds to a change in the refractive index or density of the object OB with a time difference ΔT (predetermined time difference). For example, in a substance such as a gas or a plasma whose density is far lower than the cutoff frequency, the change in the density of the object OB is essentially a change in the refractive index of the object OB , since the refractive index is a function of density. It acts as a change and brings about a phase difference.

The above description does not assume that the laser light L0 is pulsed light. When the laser light L0 is pulsed light, the operation of the optical measuring device 10 can be explained as follows. That is, the phase plate 13a (first phase plate) converts the laser light L0 (pulsed light) into first and second pulsed lights corresponding to polarized light W2a and W2b (first and second polarized light), respectively. , divide and emit. The first and second pulsed lights pass through the object OB with a time difference ΔT (predetermined time difference). The phase plate 13b (second phase plate) eliminates the time difference ΔT, recombines the first and second pulsed lights, and emits the polarized light W3 (recombined pulsed light). The polarized light W3 (recombined pulsed light) has at least one of a phase difference or an intensity difference with respect to the polarized light W1 (pulsed light), which corresponds to a change in the object OB with a time difference ΔT.

As described above, in this embodiment, by generating the time difference ΔT using the phase plates 13a and 13b, it is possible to measure ultra-high-speed phenomena on the order of the time difference ΔT or less. For example, by setting the time difference ΔT to be on the order of f (femto) seconds or less, it is possible to measure a temporal change in the object OB on the order of 10 f seconds or less. Alternatively, the time difference ΔT may be set to be on the order of 0.1 p (pico) seconds or less, and a temporal change in the object OB on the order of p seconds or less may be measured.

That is, by separating the polarized light W1 into polarized light W2a and W2b having a time difference ΔT, adding the inside of the object OB, and then combining them after eliminating the time difference ΔT, the intensity corresponding to the temporal change of the object OB can be obtained. It is possible to obtain polarized light W4 as a differential signal. As a result, a clear time difference image can be obtained in ultra-high-speed phenomena on the f (femto) second scale. Highly accurate measurement is possible using signals with high intensity and high S/N ratio.

In this embodiment, by configuring the phase plates 13a and 13b from a birefringent material, the time difference ΔT can be determined with high precision, for example, attosecond, using the refractive index difference (Δn=ne-no) of the birefringent materials. Can be ordered.

It is preferable that the time difference ΔT is less than or equal to the change time Tc of the object OB. If the time difference ΔT is larger than the change time Tc of the object OB, the accuracy of measuring the temporal change of the object OB will be greatly reduced. Note that if the time difference ΔT is too small with respect to the change time Tc, the S/N ratio will become small, so it is preferable to set the time difference ΔT to a size that can ensure a constant S/N ratio.

When a pulsed laser is used as the light source 11, the pulse width PW of the laser is preferably equal to or less than the change time Tc of the object OB. If the pulse width PW is larger than the change time Tc of the object OB, the accuracy of measuring the temporal change of the object OB will decrease. That is, by appropriately setting the upper limit of the pulse width PW, it is possible to ensure accuracy in measuring temporal changes in the object OB. Note that if the pulse width PW is too small with respect to the change time Tc, the S/N ratio will become small, so it is preferable to set the pulse width PW to a size that can ensure a constant S/N ratio.

It is preferable that the laser pulse width PW and the time difference ΔT are on the same order of magnitude. By effectively utilizing both the time difference ΔT and the pulse width PW, measurement accuracy can be improved. As shown in the examples below, for example, by dividing a laser pulse with a pulse width of 8 [f seconds] into two pulses having a time difference ΔT of 5 [f seconds], the time interval of the object OB is 15 [f seconds]. f seconds] can be measured.

By constructing the phase plates 13a and 13b from the same material, the difference in wavelength dependence between the phase plates 13a and 13b can be substantially eliminated. In particular, when pulsed light with a narrow pulse width is used as the laser light L0, the width of the wavelength λ of the laser light L0 becomes large, and the wavelength dependence of the phase plates 13a and 13b may become a problem. This problem can be solved by constructing the phase plates 13a and 13b from the same material.

(Modified example)
A modification of the present invention will be explained. In a modified example, a time differential interferometer that measures temporal changes in the object OB is configured without using the lens 14a or the like for enlarging the image of the object OB.

(Example)
Examples will be described below. FIG. 3 shows an optical measuring device 10 for observing laser wake generated by laser irradiation. The optical measurement device 10 according to the example is configured by adding a light source 11a to the optical measurement device 10 according to the embodiment. Note that elements similar to those in FIG. 1 are given the same numbers, and explanations are omitted.

Here, the object OB to be measured is a laser wake. That is, a laser wake was generated by irradiating the gas with ultra-high intensity laser light La from the light source 11a. Here, an electron beam E is also generated secondarily. As described above, the laser wake is a compression wave of electron plasma that is formed along the propagation path of the laser beam La (here, along the X axis). Electrons are accelerated by the electric field gradient of the compression wave and are emitted as an electron beam E. Here, a laser wake with a time scale (period) of approximately 15 [f seconds] was used.

As the light source 11, a TiS laser having the following specifications was used. That is, the laser beam L0 emitted from the light source 11 was set to "center wavelength λ: 800 [nm], pulse width PW: 8 [f seconds], and maximum energy: 100 [μJ]".

The phase plates 13a and 13b were made of quartz crystal (Quartz) with a thickness of 180 μm, and the phase difference ΔF was approximately 4π (equivalent to 2λ). As a result, the time difference ΔT is 5 [f seconds].

The lens 14a is an objective lens with a correction magnification of 10 times at infinity, the lens 14b is an aspheric tube lens with f (focal length) = 200 mm, and the lenses 14c and 14d are an objective lens with f = 100 and 150 mm, respectively. using a lens. The filter 15 was a narrow band filter of 10 nanometers (full width at half maximum).

FIG. 4 is a diagram showing the results of photographing a laser wake. FIG. 5 is a diagram showing the intensity distribution of laser wake. 4 and 5, (a) shows the laser wake image and intensity distribution of the comparative example, and (b) shows the laser wake image and intensity distribution of the example. The graph in FIG. 5 represents the intensity distribution of the laser wake in the X-axis direction, which is obtained by integrating the brightness and darkness of the image in FIG. 4 over the range of ΔY.

The comparative example used the shadow graph method. That is, an image of the laser wake was acquired by the imager 16 with the phase plates 13a, 13b and analyzer 12b removed. That is, in the comparative example, the single pulse of polarized light L1 passes through the object OB and enters the imager 16. On the other hand, in the embodiment, the single pulse of polarized light L1 is split into two pulsed lights (polarized lights W2a and W2b), which pass through the object OB with a time difference ΔT, are recombined, and enter the imager 16.

In the comparative example ((a) of FIG. 4), the laser wake image contains a lot of noise and is unclear. On the other hand, in the example (FIG. 4(b)), the laser wake image is clear. This point is shown more clearly from FIG. In the graph of the comparative example ((a) of FIG. 5), the period of laser wake is unclear, whereas in the graph of the example ((b) of FIG. 5), the period of laser wake is clear. .

Since the laser wake is a compressional wave of electron plasma, the refractive index changes according to the change in density. As a result, in this example, it is considered that a transient and local phase change occurs between the polarized lights W2a and W2b in accordance with the difference in refractive index at the time difference ΔT, and the intensity of the polarized light L4 changes. On the other hand, in the comparative example, it is not possible to detect a phase difference caused by such a time difference ΔT. It is thought that the comparative example detects a change in the amount of light transmitted due to the difference in refractive index itself. However, since the change in the amount of transmission is very small, the signal strength and, by extension, the S/N ratio are very small.

As described above, in this example, an ultra-high speed phenomenon of 15 [f seconds] could be measured with higher signal strength and higher S/N ratio than in the comparative example. That is, it has been shown that it is effective to use a pair of phase plates 13a and 13b to separate one polarized light into two polarized lights having a time difference ΔT, and to combine the polarized lights after passing through the object OB. Ta.

(Inventions understood from the above embodiments and modifications)
Inventions understood from the above embodiments and modifications will be described below.

(1) An optical measurement device according to a first aspect of the present invention is an optical measurement device that optically measures temporal changes in a target object, and includes a first phase plate into which polarized light is incident, and a first phase plate into which polarized light is incident; a second phase plate that faces the first phase plate with an object in between, and into which the polarized light emitted from the first phase plate and that has passed through the object is incident; and the second phase plate. a polarizer into which the polarized light emitted from the first phase plate is incident, and the first phase plate decomposes the incident polarized light into first and second polarized light and emit the polarized light with a predetermined time difference. , the second phase plate eliminates the predetermined time difference between the first and second polarized lights and emits a composite polarized light that is a combination of the first and second polarized lights. Thereby, temporal changes in the object can be optically measured using the first and second polarized lights that pass through the object with a predetermined time difference.

(2) In the optical measuring device according to the second aspect of the present invention, the synthesized polarized light has at least a phase difference or an intensity difference with respect to the polarized light, which corresponds to a change in the object at the predetermined time difference. the optical measuring device measures temporal changes of the object on the order of the predetermined time difference or less; Thereby, temporal changes in the object can be optically measured using synthetic polarized light having at least one of a phase difference and an intensity difference that corresponds to changes in the object at a predetermined time difference.

(3) In the optical measuring device according to the third aspect of the present invention, the phase difference corresponds to a change in the refractive index or density of the object at the predetermined time difference. Thereby, temporal changes in the refractive index or density of the object can be optically measured.

(4) In the optical measurement device according to the fourth aspect of the present invention, the predetermined time difference is on the order of 0.1 p (pico) seconds or less, and the optical measurement device detects a change in the object on the order of p seconds or less. Measure. This makes it possible to measure changes in the object on the order of p seconds or less. Further, the predetermined time difference may be on the order of f (femto) seconds or less, and the optical measuring device may measure a change in the object on the order of 10 f seconds or less. This makes it possible to measure changes in the object on the order of p seconds or less.

(5) In the optical measurement device according to the fifth aspect of the present invention, the predetermined time difference is on the order of f (femto) seconds or less, and the optical measurement device measures changes in the object on the order of 10 f seconds or less. do. This makes it possible to measure changes in the object on the order of 10 f seconds or less.

(6) In the optical measuring device according to the sixth aspect of the present invention, the predetermined time difference ΔT is defined by the following equation. ΔT=c/(Δn·d), Δn: refractive index difference of the first phase plate with respect to the first and second polarized light, d: thickness of the first phase plate, c: speed of light. Thereby, the predetermined time difference ΔT can be appropriately set depending on the refractive index difference and thickness of the first phase plate.

(7) In the optical measuring device according to the seventh aspect of the present invention, the polarized light incident on the first phase plate is pulsed light, and the first phase plate converts the pulsed light into the first phase plate. 1, split into first and second pulsed lights corresponding to the second polarized light, and emit them, and the first and second pulsed lights move within the object with the predetermined time difference, The second phase plate eliminates the predetermined time difference, recombines the first and second pulsed lights, and emits the recombined pulsed light, and the recombined pulsed light , has at least one of a phase difference or an intensity difference with respect to the pulsed light, which corresponds to a change in the object at the predetermined time difference. Thereby, using pulsed light, temporal changes in the object can be measured more accurately.

(8) The optical measuring device according to the eighth aspect of the present invention includes an objective lens disposed between the object and the second phase plate to magnify and represent the object. This makes it possible to configure a microscope for enlarging an object and observing its temporal changes.

(9) In the optical measuring device according to the ninth aspect of the present invention, the first and second phase plates are made of the same material. As a result, even if the polarized light incident on the first phase plate has wavelength non-uniformity, it is easy to eliminate a predetermined time difference in the first phase plate by the second phase plate. Become. That is, if the wavelength dependencies of the first and second phase plates are different, even if the thicknesses of the first and second phase plates are adjusted, the predetermined time difference cannot be eliminated by the second phase plate. . For example, when the polarized light is pulsed light with a narrow time width, wavelength non-uniformity tends to become large.

(10) An optical measurement device according to a tenth aspect of the present invention is an optical measurement method for optically measuring temporal changes in an object, which comprises a step of causing polarized light to enter a first phase plate; A step in which the polarized light incident on the first phase plate is decomposed into first and second polarized light having a predetermined time difference and emitted; a step in which the first and second polarized lights that have passed through the object are incident on a second phase plate; and a step in which the first and second polarized lights that have passed through the object are incident on a second phase plate and a step of emitting the second polarized light as a composite polarized light obtained by combining the first and second polarized light by eliminating the predetermined time difference. Thereby, temporal changes in the object can be optically measured using the first and second polarized lights that pass through the object with a predetermined time difference.

The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. are also included within the technical scope of the present invention.

10 Optical measurement device 11 Light source 12a Polarizer 12b Analyzer 13a, 13b Phase plates 14a to 14d Lens 15 Filter 16 Imager

Claims (10)

An optical measurement device that optically measures temporal changes in an object,
a first phase plate into which polarized light is incident;
a second phase plate that faces the first phase plate with the object in between, and receives the polarized light that has been emitted from the first phase plate and has passed through the object;
an analyzer into which the polarized light emitted from the second phase plate is incident;
Equipped with
The first phase plate decomposes the incident polarized light into first and second polarized light, and outputs the polarized light with a predetermined time difference,
The second phase plate is an optical measuring device, wherein the second phase plate eliminates the predetermined time difference between the first and second polarized lights and emits a composite polarized light that is a combination of the first and second polarized lights. The synthetic polarized light has at least one of a phase difference or an intensity difference with respect to the polarized light, which corresponds to a change in the object at the predetermined time difference,
The optical measuring device according to claim 1, which measures a temporal change in the object on the order of the predetermined time difference or less. The optical measuring device according to claim 2, wherein the phase difference corresponds to a change in refractive index or density of the object at the predetermined time difference. The predetermined time difference is on the order of 0.1 p (pico) seconds or less,
The optical measuring device according to any one of claims 1 to 3, which measures temporal changes in the object on the order of p seconds or less. The predetermined time difference is on the order of f (femto) seconds or less,
The optical measuring device according to any one of claims 1 to 4, which measures temporal changes in the object on the order of 10 f seconds or less. The optical measuring device according to any one of claims 1 to 5, wherein the predetermined time difference (ΔT) is defined by the following equation.
ΔT=c/(Δn・d)
Δn: refractive index difference of the first phase plate with respect to the first and second polarized light d: thickness of the first phase plate c: speed of light The polarized light incident on the first phase plate is pulsed light,
The first phase plate divides the pulsed light into first and second pulsed lights corresponding to the first and second polarized lights, and emits the split light,
The first and second pulsed lights pass through the object with the predetermined time difference,
The second phase plate eliminates the predetermined time difference, recombines the first and second pulsed lights, and emits the recombined pulsed lights,
The recombined pulsed light has at least one of a phase difference or an intensity difference with respect to the pulsed light, which corresponds to a change in the object at the predetermined time difference.
The optical measuring device according to any one of claims 1 to 6. The optical measuring device according to any one of claims 1 to 7, further comprising an objective lens disposed between the object and the second phase plate to magnify and represent the object. The optical measuring device according to any one of claims 1 to 8, wherein the first and second phase plates are made of the same material. An optical measurement method for optically measuring temporal changes in an object, the method comprising:
the polarized light is incident on the first phase plate;
a step in which the polarized light incident on the first phase plate is decomposed into first and second polarized light having a predetermined time difference and emitted;
the first and second polarized lights passing through the object with the predetermined time difference;
a step in which the first and second polarized light that has passed through the object enters a second phase plate;
a step in which the first and second polarized lights incident on the second phase plate have the predetermined time difference removed and output as composite polarized light that is a combination of the first and second polarized lights;
An optical measurement method comprising:

Images