Light measuring apparatus

Abstract

To provide a light measuring apparatus that suppresses saturation of a photodetector.SOLUTION: A light source device 110 generates a wavelength-swept optical pulse train L1 including a plurality of optical pulses p1, p2, (omitted) having different center wavelengths. The photodetector 130 receives object light L2 obtained by irradiating a sample 2 with a wavelength-swept optical pulse train L1b. A saturation suppressor 150 is provided on an optical path of beams (L1, L1a, L1b, L2) guided within the light measuring apparatus 100, branches an incident beam into a main optical path and a sub optical path, and returns the beam to the main optical path after giving a delay to a sub-pulse on the sub optical path, thereby stretching at least one of the plurality of optical pulses p1 to pn.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a light measurement device. [Background technology]

[0002] Spectroscopic analysis is widely used for the component analysis and inspection of objects. In spectroscopic analysis, an object is irradiated with irradiating light and the spectrum of the resulting object light is measured. Then, based on the relationship between the spectrum of the object light and the spectrum of the irradiating light, optical characteristics such as reflectance characteristics (wavelength dependence) or transmittance characteristics can be obtained.

[0003] Wavelength-swept spectroscopy is known as one of the methods for measuring optical properties. A wavelength-swept spectrometer generates wavelength-swept light, whose wavelength changes over time, and irradiates the test object. The wavelength-swept light is a pulse or pulse train in which time and wavelength have a one-to-one relationship. The time waveform of the light obtained by irradiating the test object with the wavelength-swept light is then detected by a photodetector. The output waveform of the photodetector represents a spectrum in which the time axis corresponds to the wavelength.

[0004] 1 is a diagram showing a wavelength sweep type spectroscopic device 10. The spectroscopic device 10 includes a light source device 20, a spectroscopic head 30, and a processing unit 40.

[0005] The light source device 20 generates wavelength-swept light L1. The wavelength-swept light L1 is guided to the spectroscopic head 30. The irradiation optical system 31 of the spectroscopic head 30 irradiates the wavelength-swept light L1 onto the sample 2. The first photodetector 32 detects light (object light) L2 obtained as a result of irradiating the sample 2 with the wavelength-swept light L1. The object light L2 can be reflected light or transmitted light from the sample 2.

[0006] In the irradiation optical system 31, a part of the wavelength swept light L1 is branched off as reference light L3. The reference light L3 is measured by a second light receiver 33. As the light receiver 32, a photodetector such as a photodiode (PD) is used.

[0007] The first detection signal S1 generated by the first photodetector 32 and the second detection signal S2 generated by the second photodetector 33 are supplied to the arithmetic processing device 40. The object light L2 and the reference light L3 inherit the one-to-one time-wavelength correspondence of the wavelength-swept light L1. Therefore, the time waveform of the first detection signal S1 can be converted into the spectrum of the object light L2 by converting the time axis into wavelength. Similarly, the time waveform of the second detection signal S2 can be converted into the spectrum of the reference light L3 by converting the time axis into wavelength. The arithmetic processing device 40 calculates the ratio of each corresponding wavelength of the object light L2 to the reference light L3 and measures the spectral characteristics (reflectance and transmittance) of the sample 2. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-159973 [Patent Document 2] Japanese Patent Application Publication No. 2020-159971 Summary of the Invention [Problem to be solved by the invention]

[0009] In order to increase the S / N ratio in the spectrometer 10 of Figure 1, it is necessary to increase the intensity of the wavelength-swept light L1. This will increase the intensity of the object light L2 incident on the photodetector 32. The output of the photodetector is proportional to the input optical signal in the linear region, but will saturate if the input optical signal is too strong. Saturation of the photodetector will result in a decrease in measurement accuracy.

[0010] The present disclosure has been made in light of this situation, and one of its exemplary purposes is to provide a light measurement device that suppresses saturation of a light receiver. [Means for solving the problem]

[0011] An optical measurement device according to an embodiment of the present disclosure includes a light source device that generates a wavelength-swept optical pulse train including a plurality of optical pulses with different center wavelengths, and a photodetector that receives object light obtained by irradiating a sample with the wavelength-swept optical pulse train. The optical measurement device further includes a saturation suppressor that is provided on an optical path of a beam guided within the optical measurement device, splits the incident beam into a main optical path and a sub optical path, and returns the sub-pulse on the sub optical path to the main optical path after delaying it, thereby stretching at least one of the plurality of optical pulses.

[0012] Any combination of the above elements, or mutual substitution of elements or expressions between methods, devices, systems, etc., are also valid aspects of the present invention or the present disclosure. Furthermore, the description in this section (Means for Solving the Problems) does not explain all essential features of the present invention, and therefore, subcombinations of the described features may also constitute the present invention. [Effects of the Invention]

[0013] According to an aspect of the present disclosure, saturation of the optical receiver can be suppressed, enabling more accurate measurements. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing a wavelength sweep type spectroscopic device. [Figure 2] FIG. 1 is a diagram illustrating a light measurement device according to an embodiment. [Figure 3] 3 is a diagram illustrating the operation of the light measurement device of FIG. 2. [Figure 4] FIG. 2 illustrates a saturation suppressor according to an embodiment. [Figure 5] 5 is a diagram illustrating the operation of the saturation suppressor of FIG. 4. FIG. [Figure 6] FIG. 2 illustrates a saturation suppressor according to an embodiment. [Figure 7] FIG. 2 illustrates a saturation suppressor according to an embodiment. [Figure 8] FIG. 2 illustrates a saturation suppressor according to an embodiment. [Figure 9]FIG. 10 is a diagram showing an example of the configuration of a light source device according to Modification 2. [Figure 10] FIG. 10 is a diagram showing an example of the configuration of a light source device according to Modification 3. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Outline of the embodiment) A summary of some exemplary embodiments of the present disclosure is provided. This summary is intended to provide a simplified overview of some concepts of one or more embodiments in order to provide a basic understanding of the embodiments as a prelude to the more detailed description that follows. It is not intended to limit the scope of the invention or disclosure. Furthermore, this summary is not an exhaustive overview of all possible embodiments, nor does it limit essential elements of the embodiments. For convenience, the term "one embodiment" may refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed herein.

[0016] According to one embodiment, an optical measurement device includes a light source device that generates a wavelength-swept optical pulse train including a plurality of optical pulses with different center wavelengths, and a photodetector that receives object light obtained by irradiating a sample with the wavelength-swept optical pulse train. The optical measurement device further includes a saturation suppressor that is provided on an optical path of a beam guided within the optical measurement device, splits the incident beam into a main optical path and a sub optical path, delays the sub-pulses on the sub optical path, and then returns the sub-pulse to the main optical path, thereby stretching at least one of the plurality of optical pulses.

[0017] The object light contains multiple optical pulses corresponding to the multiple optical pulses contained in the wavelength-swept optical pulse train. If the intensity of each optical pulse incident on the optical receiver is high, the output signal from the optical receiver will saturate, making accurate spectrum measurement difficult. With the above configuration, by widening the pulse width of the optical pulses and lowering the peak, it is possible to suppress the intensity peak while avoiding energy loss of the object light incident on the optical receiver, thereby suppressing saturation in the optical receiver and improving measurement accuracy.

[0018] In one embodiment, the saturation suppressor may stretch the optical pulses so that they do not overlap with adjacent optical pulses, i.e., while maintaining the separation of the optical pulses, thereby enabling measurements to be made without destroying the one-to-one correspondence between wavelength and time.

[0019] In one embodiment, the spacing between the optical pulses is T, the delay of the sub-path is Δt, and when the mth sub-pulse forming the output pulse of the saturation suppressor is buried in noise, T>Δt×m may satisfy the following relationship.

[0020] In one embodiment, the saturation suppressor may include a two-port input, two-port output optical coupler that receives the incident beam at a first input port, and a delay optical path disposed between a second input port of the optical coupler and a second output port of the optical coupler, and the stretched optical pulse may be emitted from the first output port of the optical coupler.

[0021] In one embodiment, the saturation suppressor may include a total reflection mirror that forms a secondary optical path, i.e., free space may be used as the secondary optical path.

[0022] In one embodiment, the sub-path sub-pulses may be returned to a junction upstream of the branch point of the main and sub-paths, so that the beam is repeatedly guided along its original path, with repeated attenuation and delay, resulting in a smooth optical pulse.

[0023] In one embodiment, the sub-pulses on the secondary path may be returned to a junction downstream of the branch point of the primary and secondary paths.

[0024] In one embodiment, the sub-pulses on the secondary path may be returned to a junction that also serves as a branch point for the primary and secondary paths.

[0025] In one embodiment, the saturation suppressor may include a beam splitter or a half mirror provided at the branch point of the main optical path and the sub-optical path. Since the beam splitter and the half mirror have a wider bandwidth than the optical coupler, it is preferable to use the beam splitter or the optical coupler when it is desired to make the saturation suppressor act over a wider bandwidth.

[0026] In one embodiment, the light source device may include a pulse light source that generates broadband pulsed light having a continuous spectrum, and a pulse stretcher that shapes the broadband pulsed light into a wavelength-swept optical pulse train. The saturation suppressor may receive the broadband pulsed light or the output light of the pulse stretcher as an incident beam.

[0027] In one embodiment, the light source device may include a pulse light source that generates broadband pulsed light having a continuous spectrum and a pulse stretcher that shapes the broadband pulsed light into a wavelength-swept optical pulse train. The pulse stretcher may include a demultiplexer that branches the broadband pulsed light into multiple beams, a fiber group including multiple fibers that impart different delays to the multiple beams, and a multiplexer that combines the output beams of the multiple fibers. The saturation suppressor may stretch a beam guided through one of the multiple fibers. Depending on the spectroscopic characteristics (reflection characteristics, absorption characteristics, and transmission characteristics) of the object to be measured, the light intensity reaching the optical receiver may be high in a specific wavelength range. In such cases, saturation of the optical receiver can be suppressed by stretching the beam guided through the fiber corresponding to that wavelength range. Furthermore, since the wavelength band covered by the saturation suppressor is narrowed, the design of the saturation suppressor is simplified.

[0028] In one embodiment, a plurality of saturation suppressors may be provided, each of which may expand the beam guided in a corresponding one of the fibers.

[0029] In one embodiment, the optical receiver may be a photodiode.

[0030] (Embodiment) The present disclosure will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing are designated by the same reference numerals, and redundant descriptions will be omitted where appropriate. Furthermore, the embodiments are illustrative and do not limit the disclosure, and all features and combinations thereof described in the embodiments are not necessarily essential to the disclosure.

[0031] The dimensions (thickness, length, width, etc.) of each component shown in the drawings may be enlarged or reduced as appropriate for ease of understanding. Furthermore, the dimensions of multiple components do not necessarily represent their relative sizes. Even if a component A is drawn thicker than another component B in the drawings, it is possible that component A is thinner than component B.

[0032] (Embodiment) 2 is a diagram showing a light measurement device 100 according to an embodiment. The light measurement device 100 includes a light source device 110, an irradiation optical system 120, a light receiver 130, a processing device 140, and a saturation suppressor 150.

[0033] The light source device 110 generates a wavelength swept optical pulse train L1, which is a pulse train including a plurality of optical pulses p1 to pn with different center wavelengths. The plurality of optical pulses p1 to pn have different center wavelengths and are arranged at intervals on the time axis. The center wavelengths of the plurality of optical pulses p1 to pn are λ1 to λ n The wavelength components contained in the i-th pulse pi are treated as having the same wavelength λi.

[0034] Saturation suppressor 150 is provided on the optical path of the beam that is guided within optical measurement device 100. Saturation suppressor 150 splits the incident beam into a main optical path and a sub-optical path, and stretches at least one of the multiple optical pulses p1 to pn by delaying the sub-pulse on the sub-optical path and then returning it to the main optical path.

[0035] In this embodiment, the wavelength swept optical pulse train L1 including all the optical pulses p1 to pn is incident on the saturation suppressor 150. Therefore, the saturation suppressor 150 stretches each of the optical pulses p1 to pn on the time axis. Assuming that the energy of each pulse is conserved, the peak intensity of each pulse decreases. It is desirable that the saturation suppressor 150 stretches each of the optical pulses p1 to pn so that they do not overlap with adjacent optical pulses.

[0036] The irradiation optical system 120 receives the wavelength swept optical pulse train L1a including optical pulses pa1 to pan whose peaks have been suppressed by the saturation suppressor 150, and irradiates the wavelength swept optical pulse train L1b onto the sample 2. The photoreceiver 130 receives the object light L2 obtained as a result of irradiating the wavelength swept optical pulse train L1b onto the sample 2. This object light L2 also includes a plurality of pulses pb1 to pbn corresponding to the plurality of pulses p1 to pn.

[0037] The processing device 140 converts the output of the light receiver 130 into a digital signal and processes it to generate spectrum data of the sample 2 and / or determine whether the sample 2 is good or bad.

[0038] The above is the configuration of the light measurement device 100. Next, the operation thereof will be described.

[0039] Fig. 3 is a diagram showing the operation of the optical measurement device 100 in Fig. 2. Fig. 3 shows the wavelength swept optical pulse train L1, the expanded wavelength swept optical pulse trains L1a and L1b, and the object light L2.

[0040] The wavelength swept optical pulse train L1 generated by the light source device 110 includes a plurality of optical pulses p1 to pn. Each pulse p1 to pn has a different center wavelength λ1 to λ n The light pulses p1, p2, ..., pn are generated at times t1, t2, ..., t n and wavelengths λ1, λ2...λ n There is a one-to-one correspondence between time and wavelength. This is called the uniqueness of time and wavelength.

[0041] λ1 and λ n The magnitude relationship between λ1>λ2>…>λn (positive chirp). Conversely, λ1<λ2<…<λ n may be satisfied (negative chirp).

[0042] The optical pulses p1 to pn are each stretched on the time axis by the saturation suppressor 150. As a result, the peaks of the stretched optical pulses pa1 to pan become lower than those of the original optical pulses p1 to pn.

[0043] When the wavelength-swept light pulse train L1b is irradiated onto the sample 2, some of the wavelengths of the wavelength-swept light pulse train L1b are absorbed according to the spectroscopic characteristics of the sample 2. In other words, focusing on the object light L2, light pulses having wavelengths corresponding to the absorption spectrum of the sample 2 are attenuated. In other words, the energy of each light pulse Lb1 to Lbn is attenuated at the corresponding wavelengths λ1 to λ n It has a correlation with the absorptance (in other words, reflectance or transmittance) of sample 2 in

[0044] The photoreceiver 130 measures the optical pulses pb1 to pbn contained in the object light L2. The electrical signal output from the photoreceiver 140 has a waveform corresponding to the object light L2 and includes a pulse train.

[0045] The processing device 140 converts the output signal of the light receiver 140 into a digital signal and takes it in. Then, it integrates the energy for each pulse. Since the energy of each pulse correlates with the absorptance of the corresponding wavelength in the sample 2, the integrated value of each of the multiple pulses is n represents the absorption spectrum of

[0046] The operation of the optical measurement device 100 is as described above.

[0047] According to this optical measurement device 100, the intensity peak of the object light L2 incident on the optical receiver 130 is suppressed. This makes it possible to suppress saturation in the optical receiver 130 while maintaining a sufficient S / N ratio, thereby enabling highly accurate measurements. Since this optical measurement device 100 does not use a dimming element or the like for attenuation, there is very little energy loss, and it has the advantage of being able to effectively utilize the energy of the original wavelength-swept optical pulse train L1. As described above, the energy of each pulse correlates with the absorptance of the corresponding wavelength in the sample 2, so when measuring the absorptance of the sample 2, more accurate measurements can be achieved by making maximum use of the energy of each optical pulse irradiated onto the sample 2.

[0048] Furthermore, the change over time in the waveform intensity of the optical pulse incident on the photodetector 130 becomes gentler. This means that the electrical signal output from the photodetector 130 becomes gentler, meaning that it does not contain high-frequency components. This eases the design requirements for the analog front-end circuit that amplifies the electrical signal and converts it into a digital signal. Specifically, since high-speed circuits are no longer required, the design becomes easier and costs can be reduced.

[0049] Next, an example of the configuration of the saturation suppressor 150 will be described.

[0050] 4 is a diagram illustrating a saturation suppressor 150A according to one embodiment. The saturation suppressor 150A includes an optical coupler 152 and a delay fiber 154. The optical coupler 152 is a 2×2 fiber coupler (also called a branching coupler) having two input ports and two output ports. The optical coupler 152 receives an incident beam at a first input port IN1. The delay fiber 154 is connected between a second output port OUT2 of the optical coupler 152 and the second input port IN2.

[0051] The path between the first input port IN1 and the first output port OUT1 is considered to be a main optical path 156, and the path from the second output port OUT2 back to the second input port IN2 via the delay fiber 154 is considered to be a sub-optical path 158. It can be seen that the saturation suppressor 150A splits the incident beam (incident pulse) into the main optical path and the sub-optical path, and returns the sub-pulse on the sub-optical path to the main optical path after giving it a delay.

[0052] 5 is a diagram illustrating the operation of the saturation suppressor 150A of FIG. 4. The upper part shows the input pulse Pi (p1, p2... in FIG. 3), and the lower part shows the output pulse Po (pa1, pa2... in FIG. 3). Assuming that there is zero loss, the branching ratio of the optical coupler 152 is 50%. The intensity of the input pulse Pi is I0. In this case, a pulse (called a sub-pulse) with an intensity I1 = I0 × 1 / 2 is coupled to the main optical path, and a sub-pulse with the same intensity I0 × 1 / 2 is coupled to the sub-optical path. The sub-pulse coupled to the sub-optical path returns to the input side via the delay fiber 154. The intensity I2 = I0 × (1 / 2), which is half the intensity of the sub-pulse that returned to the input side, is 2 A sub-pulse with the same intensity I0 × (1 / 2) is coupled into the main optical path. 2 The same process continues, with each delay (i=3, 4, ...) resulting in a sub-pulse with intensity I j =I0×(1 / 2) j This operation is repeated, and the output pulse becomes a superposition of multiple sub-pulses, stretching the pulse width of the input pulse Pi and suppressing the peak.

[0053] The delay in the subpath is Δt, which is chosen so that the trailing edge of the output pulse falls off smoothly and uniformly, i.e., so that the output pulse does not have multiple peaks or split into multiple pulses.

[0054] As shown in Figure 5, when a pulse is stretched, the tail (trailing edge) of the pulse moves closer to the next pulse. As mentioned above, it is desirable that the stretched optical pulses be separated from their neighbors. Separated pulses mean that there is a section between adjacent pulses where the intensity drops to the noise floor.

[0055] Let us now assume that the peak-to-peak amplitude of random noise is 2n. By averaging N times, the noise is suppressed, and n' = n / (√N). If the Mth pulse of the multiple pulses with intensities I1, I2, I3... contained in the emitted pulse Po is buried in noise n', then the subsequent pulses are treated as if they do not exist. In other words, m is the smallest integer that satisfies the following inequality: n'>I0×(1 / 2) m

[0056] Assume that the interval between incident pulses Pi is T. In order to prevent the influence of the tail of the current incident pulse on the next incident pulse, T>Δt×m The saturation suppressor 150A may be designed so that the following holds true:

[0057] 5 uses a branching coupler. The wavelength range of a branching coupler that is generally available and considered to be wideband is about 100 nm. Therefore, the wavelength range λ1 to λ n This is not suitable for measurements where the wavelength ranges over several hundred nanometers. For example, the wavelength of light obtained from an SC pulse light source is very broad, ranging from 900 nm to 1300 nm, so a configuration using a branching coupler cannot obtain flat characteristics. For such broadband optical measurements, it is preferable to use a configuration using a beam splitter instead of a branching coupler, as will be explained below.

[0058] FIG. 6 illustrates a saturation suppressor 150B according to one embodiment. The saturation suppressor 150B includes beam splitters BS1 and BS2 and total reflection mirrors M1 and M2. The beam splitter BS1 splits an incident pulse into a main optical path 156 and a sub-optical path 158. The beams propagating through the main optical path 156 and the sub-optical path 158 are combined at the beam splitter BS2. The total reflection mirrors M1 and M2 delay the light split by the beam splitter BS1 and guide it to the beam splitter BS2. A polarizing beam splitter (PBS) or a half mirror can be used as the beam splitters BS1 and BS2. The saturation suppressor 150B can expand a wideband incident pulse. With this configuration, the output pulse in FIG. 5 includes only a pulse having intensity I1 and a pulse having intensity I2, and the pulse width of the expanded output pulse is narrower than that in FIG. 4.

[0059] 7 is a diagram showing a saturation suppressor 150C according to one embodiment. The saturation suppressor 150C includes beam splitters BS3 and BS4 and total reflection mirrors M6 to M9. The beam splitter BS3 splits an incident pulse into a main optical path 156 and a sub optical path 158. The beams guided through the main optical path 156 and the sub optical path 158 are combined at the beam splitter BS4. The total reflection mirrors M6 and M7 delay the light split by the beam splitter BS3 and guide it to the beam splitter BS2.

[0060] In this embodiment, a portion of the beam directed from total reflection mirror M7 is transmitted through beam splitter BS4. The beam transmitted through beam splitter BS4 is delayed by total reflection mirrors M8 and M9 and returned to beam splitter BS3. The returned beam splits into a main optical path 156 and a secondary optical path 158.

[0061] This saturation suppressor 150C can expand a wideband input pulse. In addition, the output pulse contains three or more pulses, similar to the saturation suppressor 150A in Fig. 4, so the trailing edge of the pulse can be made gentle.

[0062] 8 is a diagram showing a saturation suppressor 150D according to one embodiment. The saturation suppressor 150D includes a beam splitter BS5 and total reflection mirrors M10 to M13. The beam splitter BS5 splits an incident pulse into a main optical path 156 and a sub optical path 158. The total reflection mirrors M10 to M13 delay the light split by the beam splitter BS5 and return the light to the beam splitter BS5. The beam returned to the beam splitter BS5 splits into the main optical path 156 and the sub optical path 158.

[0063] This saturation suppressor 150D can expand a wideband input pulse. The output pulse contains three or more pulses, similar to the saturation suppressor 150A in Fig. 4. Furthermore, compared to the configuration in Fig. 7, the number of beam splitters can be reduced to one.

[0064] Next, a modified example of the light measurement device 100 will be described.

[0065] (Variation 1) 2, the saturation suppressor 150 is inserted between the light source device 110 and the irradiation optical system 120 to stretch the wavelength swept light pulse train L1, but the present disclosure is not limited to this. For example, the saturation suppressor 150 may be incorporated into the irradiation optical system 120, or may be arranged on the optical path of the object light L2 to stretch the object light L2.

[0066] (Variation 2) The saturation suppressor 150 may be incorporated into the light source device 110. Fig. 9 is a diagram showing an example configuration (110E) of the light source device 110 according to Modification 2. The light source device 110E includes a pulse light source 112 and a pulse stretcher 114. The pulse light source 112 is, for example, an SC (Super Continuum) light source, and generates broadband pulsed light (SC pulse) L0 including a continuous spectrum over a wide band.

[0067] The pulse stretcher 114 shapes the broadband pulsed light L0 into a wavelength-swept optical pulse train L1. The pulse stretcher 114 includes a demultiplexer 115, a delay line 116 including multiple fibers FB1 to FBn, and a multiplexer 117. The demultiplexer 115 branches the broadband pulsed light L0 into multiple paths according to wavelength. The input end of each of the multiple fibers 116 is coupled to a corresponding one of multiple output ends of the demultiplexer 115. The multiple fibers FB1 to FBn have different lengths, and the length of each fiber FB1 to FBn (delay line 116) is determined so that the optical pulses p1 to pn included in the wavelength-swept light L1 have a predetermined interval T.

[0068] The multiplexer 117 is coupled to the output ends of the plurality of fibers 116, and spatially combines the light beams that have been guided through the plurality of fibers 116, and outputs the combined light beams.

[0069] The demultiplexer 115 and the multiplexer 117 may be an AWG (Arrayed Waveguide Grating) or other optical elements.

[0070] In the second modification, the saturation suppressor 150 can be provided on the optical path of the wideband pulsed light L0. For example, when the saturation suppressor 150 has the configuration shown in Fig. 4, the beam may be focused and coupled to the input end of the saturation suppressor 150 or to a fiber connected to the input end, as shown in (i) of Fig. 9. When the saturation suppressor 150 has the configurations shown in Figs. 6 to 8, the saturation suppressor 150 may be disposed at the position shown in (ii) of Fig. 9.

[0071] 9 (iii), a saturation suppressor 150 may be provided after the combiner 117. This makes it possible to simultaneously suppress the peak intensities of multiple pulses, and also reduces the number of required components, resulting in cost benefits.

[0072] (Variation 3) 10 is a diagram showing a configuration example (110F) of a light source device 110 according to Modification 3. In Modification 3, the saturation suppressor 150 is incorporated into the delay line 116. Specifically, it is inserted into one of the multiple channels branched by the demultiplexer 115. The position of the saturation suppressor 150 may be upstream or downstream of each of the fibers FB1 to FBn. Furthermore, the saturation suppressor 150 may be provided in multiple channels.

[0073] Depending on the sample 2, a specific wavelength band λ k In this case, the spectral intensity of the object light L2 may be strong only in a specific wavelength band λ k For such an application, a saturation suppressor 150A having a branching coupler as shown in FIG.

[0074] Although the embodiments of the present disclosure have been described using specific terms, this description is merely an example to facilitate understanding and does not limit the scope of the present disclosure or the claims. The scope of the present invention is defined by the claims, and therefore, embodiments, examples, and modifications not described herein are also included in the scope of the present invention. [Explanation of symbols]

[0075] L1 wavelength swept light L2 object light 2. Sample 100 Light measuring device 110 Light source device 112 Pulsed Light Source 114 Stretcher 115 Duplexer 116 Delay Lines 117 Multiplexer 120 Irradiation optical system 130 Receiver 140 Processing equipment 150 Saturation suppressor 152 Optical Coupler 154 Delay Fiber 156 Main optical path 158 Secondary optical path BS beam splitter M Total Reflection Mirror L0 broadband pulsed light L1 wavelength swept light L2 object light L3 reference beam

Claims

1. A light measurement device, comprising: a light source device that generates a wavelength swept optical pulse train including a plurality of optical pulses with different center wavelengths; a photodetector for receiving object light obtained by irradiating a sample with the wavelength swept light pulse train; Equipped with An optical measurement device characterized by further comprising a saturation suppressor that is provided on the optical path of the beam guided within the optical measurement device, splits the incident beam into a main optical path and a sub-optical path, delays the sub-pulse on the sub-optical path, and then returns it to the main optical path, thereby stretching at least one of the multiple optical pulses.

2. 2. The optical measurement device according to claim 1, wherein the saturation suppressor extends the optical pulse so that the optical pulse does not overlap with an adjacent optical pulse.

3. When the interval between the plurality of optical pulses is T, the delay of the sub-optical path is Δt, and the m-th sub-pulse forming the output pulse of the saturation suppressor is buried in noise, T>Δt×m 2. The optical measurement device according to claim 1, wherein the following relationship is satisfied:

4. The saturation suppressor comprises: a two-port input, two-port output optical coupler that receives the incident beam at a first input port; a delay path disposed between a second input port of the optical coupler and a second output port of the optical coupler; 4. The optical measurement device according to claim 1, further comprising: a first output port of the optical coupler, and the optical pulse after expansion is output from the first output port of the optical coupler.

5. 4. The optical measurement device according to claim 1, wherein the saturation suppressor includes a total reflection mirror that forms the secondary optical path.

6. 4. The optical measurement device according to claim 1, wherein the sub-pulse on the secondary optical path is returned to a junction point upstream of a branch point of the main optical path and the secondary optical path.

7. 4. The optical measurement device according to claim 1, wherein the sub-pulse on the secondary optical path is returned to a junction point downstream of a branch point of the main optical path and the secondary optical path.

8. 7. The optical measurement device according to claim 6, wherein the saturation suppressor includes a beam splitter or a half mirror provided at a branch point of the main optical path and the sub-optical path.

9. The light source device is a pulsed light source that generates broadband pulsed light having a continuous spectrum; a pulse stretcher that shapes the broadband pulsed light into the wavelength-swept optical pulse train; Equipped with 4. The optical measurement device according to claim 1, wherein the saturation suppressor receives the broadband pulsed light or the light emitted from the pulse stretcher as the incident beam.

10. The light source device is a pulsed light source that generates broadband pulsed light having a continuous spectrum; a pulse stretcher that shapes the broadband pulsed light into the wavelength-swept optical pulse train; Equipped with The pulse stretcher a demultiplexer that branches the broadband pulsed light into a plurality of beams; a fiber group including a plurality of fibers that impart different delays to the plurality of beams; a combiner for combining output beams from the plurality of fibers; Including, 4. The optical measurement device according to claim 1, wherein the saturation suppressor extends a beam guided through one of the plurality of fibers.

11. 11. The optical measurement device according to claim 10, wherein a plurality of said saturation suppressors are provided, and each saturation suppressor expands a beam propagating through a corresponding one of said fibers.

12. 4. The optical measurement device according to claim 1, wherein the light receiver is a photodiode.

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