Optical measuring device, optical measuring method, and computer program

Abstract

This technology enables more precise temperature control of light sources. [Solution] The optical measuring device (1) includes a light-emitting unit (11) that irradiates light onto the object to be measured, a light-receiving unit (12) that outputs a light-receiving signal, a disturbance generation unit (13) that generates a disturbance signal, and an adjustment unit (14) that adjusts the drive current based on the signal generated based on the light-receiving signal and the disturbance signal. The adjustment unit (14) further includes an amplitude changing unit (141) that changes the amplitude of the disturbance signal.

Description

Technical Field

[0001] The present invention relates to an optical measurement device, an optical measurement method, and a computer program.

Background Art

[0002] Patent Document 1 discloses suppressing noise by controlling the temperature of a light source in a technique for detecting the velocity of a fluid using Doppler shift.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, the drive current supplied to the light source is oscillated, and the drive current is adjusted based on the result. However, the relationship between the temperature and noise in the light source is complex, and there are cases where even if the drive current is adjusted, the temperature of the light source cannot reach a temperature range in which noise is suppressed.

[0005] One aspect of the present invention aims to realize a technique for more accurately adjusting the temperature of a light source.

Means for Solving the Problems

[0006] To solve the above problems, an optical measuring device according to one aspect of the present invention includes: a light-emitting unit that irradiates light onto a measuring object through which a fluid is flowing; a light-receiving unit that receives scattered light from the measuring object and outputs a light-receiving signal corresponding to the intensity of the scattered light; a disturbance generation unit that generates a disturbance signal that causes the drive current supplied to the light-emitting unit to fluctuate; and an adjustment unit that adjusts the drive current based on the signal generated based on the light-receiving signal and the disturbance signal, wherein the adjustment unit further includes an amplitude changing unit that changes the amplitude of the disturbance signal.

[0007] To solve the above problems, an optical measuring device according to one aspect of the present invention includes: a light-emitting unit that irradiates light onto a measuring object through which a fluid is flowing; a light-receiving unit that receives scattered light from the measuring object and outputs a light-receiving signal corresponding to the intensity of the scattered light; a disturbance generation unit that generates a disturbance signal that causes the drive current supplied to the light-emitting unit to fluctuate; and an adjustment unit that adjusts the drive current based on the signal generated based on the light-receiving signal and the disturbance signal, wherein the adjustment unit further includes an amplitude changing unit that changes the amplitude of the disturbance signal; a light intensity determination unit that determines whether the light power of the light irradiated by the light-emitting unit is within a specified light intensity range; an upper limit limiting unit that limits the upper limit of the drive current when the light power exceeds the specified light intensity; and a lower limit limiting unit that limits the lower limit of the drive current when the light power falls below the specified light intensity.

[0008] To solve the above problems, an optical measurement method according to one aspect of the present invention is an optical measurement method in an optical measurement device comprising: a light-emitting unit that irradiates light onto a measurement target through which a fluid is flowing; and a light-receiving unit that receives scattered light from the measurement target and outputs a light-receiving signal corresponding to the intensity of the scattered light, the method comprising: a disturbance generation step that generates a disturbance signal that causes the drive current supplied to the light-emitting unit to fluctuate; and an adjustment step that adjusts the drive current based on the signal generated based on the light-receiving signal and the disturbance signal, wherein the adjustment step further includes an amplitude changing step that changes the amplitude of the disturbance signal.

[0009] To solve the above problems, an optical measurement method according to one aspect of the present invention is an optical measurement method in an optical measurement device comprising: a light-emitting unit that irradiates light onto a measurement target through which a fluid is flowing; and a light-receiving unit that receives scattered light from the measurement target of the irradiated light and outputs a light-receiving signal corresponding to the intensity of the scattered light, the method comprising: a disturbance generation step that generates a disturbance signal that causes the drive current supplied to the light-emitting unit to fluctuate; and an adjustment step that adjusts the drive current based on the signal generated based on the light-receiving signal and the disturbance signal, wherein the adjustment step further comprises: an amplitude change step that changes the amplitude of the disturbance signal; a light intensity determination step that determines whether the optical power of the light irradiated by the light-emitting unit is within a specified light intensity range; an upper limit limit step that limits the upper limit of the drive current when the optical power exceeds the specified light intensity; and a lower limit limit step that limits the lower limit of the drive current when the optical power falls below the specified light intensity.

[0010] To solve the above problems, a computer program according to one aspect of the present invention provides a computer for an optical measuring device comprising: a light-emitting unit that irradiates light onto a measuring object through which a fluid is flowing; and a light-receiving unit that receives scattered light from the measuring object and outputs a light-receiving signal corresponding to the intensity of the scattered light. The computer for this device functions as a disturbance generation unit that generates a disturbance signal to cause fluctuations in the drive current supplied to the light-emitting unit; and an adjustment unit that adjusts the drive current based on the signal generated based on the light-receiving signal and the disturbance signal. The adjustment unit further functions as an amplitude changing unit that changes the amplitude of the disturbance signal.

[0011] To solve the above problems, a computer program according to one aspect of the present invention provides a computer for an optical measuring device comprising: a light-emitting unit that irradiates light onto a measuring object through which a fluid is flowing; and a light-receiving unit that receives scattered light from the measuring object and outputs a light-receiving signal corresponding to the intensity of the scattered light. The computer for this device functions as: a disturbance generation unit that generates a disturbance signal that causes fluctuations in the drive current supplied to the light-emitting unit; and an adjustment unit that adjusts the drive current based on the signal generated based on the light-receiving signal and the disturbance signal. The adjustment unit further functions as: an amplitude changing unit that changes the amplitude of the disturbance signal; a light intensity determination unit that determines whether the light power of the light irradiated by the light-emitting unit is within a specified light intensity range; an upper limit limiting unit that limits the upper limit of the drive current when the light power exceeds the specified light intensity; and a lower limit limiting unit that limits the lower limit of the drive current when the light power falls below the specified light intensity. [Effects of the Invention]

[0012] According to one aspect of the present invention, the temperature of the light source can be adjusted more precisely. [Brief explanation of the drawing]

[0013] [Figure 1] This is a block diagram showing an example configuration of the optical measuring device according to the present invention. [Figure 2] This figure shows an example of changing the amplitude of a disturbance signal according to the present invention. [Figure 3] This figure shows an example of adjusting the drive current according to the present invention. [Figure 4] This is a flowchart illustrating an example of the flow of the optical measurement method according to the present invention. [Figure 5] This is a block diagram showing an example configuration of the optical measuring device according to the present invention. [Figure 6] This figure shows an example of changing the amplitude of a disturbance signal according to the present invention. [Figure 7] This figure shows an example of adjusting the drive current according to the present invention. [Figure 8] This figure shows an example of the change in light intensity over time according to the present invention. [Figure 9]It is a diagram showing an example of adjusting a drive current according to the present invention. [Figure 10] It is a diagram showing an example of adjusting a drive current according to the present invention. [Figure 11] It is a diagram showing an example of limiting the amount of light according to the present invention. [Figure 12] It is a diagram showing an example of adjusting a drive current according to the present invention. [Figure 13] It is a diagram showing an example of the change over time of the amount of light according to the present invention. [Figure 14] It is a diagram showing an example of adjusting a drive current according to the present invention. [Figure 15] It is a diagram showing an example of adjusting a drive current according to the present invention. [Figure 16] It is a diagram showing an example of limiting the amount of light according to the present invention. [Figure 17] It is a diagram showing an example of adjusting a drive current according to the present invention. [Figure 18] It is a diagram showing an example of adjusting a drive current according to the present invention. [Figure 19] It is a flowchart showing an example of the flow of the light measurement method according to the present invention. [Figure 20] It is a block diagram showing an example of the configuration of the light measurement device according to the present invention. [Figure 21] It is a diagram showing an example of the relationship between the LD temperature and the average frequency according to the present invention. [Figure 22] It is a diagram showing an example of the relationship between the LD temperature and the average frequency according to the present invention. [Figure 23] It is a diagram showing an example of the relationship between the LD temperature and the average frequency according to the present invention. [Figure 24] It is a flowchart showing an example of the flow of the light measurement method according to the present invention.

Embodiments for Carrying Out the Invention

[0014] 〔Embodiment 1〕 Hereinafter, an embodiment of the present invention will be described in detail.

[0015] [[ID=*59*]](Outline of the Light Measurement Device 1) The optical measuring device 1 is a device that irradiates a target to be measured with light and measures the scattered light from the target. The target to be measured is, for example, a pipe through which a fluid flows. For example, the optical measuring device 1 estimates the flow velocity of the fluid flowing through the target by measuring the scattered light. The optical measuring device 1 may also be, for example, a medical device used to measure biological components such as blood.

[0016] (Configuration of optical measuring device 1) The configuration of the optical measuring device 1 will be described with reference to Figure 1. Figure 1 is a block diagram showing an example of the configuration of the optical measuring device 1. As shown in Figure 1, the optical measuring device 1 comprises a light-emitting unit 11, a light-receiving unit 12, a disturbance generation unit 13, and an adjustment unit 14.

[0017] (Light-emitting part 11) The light-emitting unit 11 irradiates light onto the object to be measured through which the fluid flows. Here, the light-emitting unit 11 may be, for example, a semiconductor laser. The object to be measured may be, for example, a conduit such as a tube through which a fluid flows. The fluid flowing through the object to be measured may be, for example, a light-scattering material. Specific examples of such fluids include blood flowing in the blood vessels of a living organism, ink, oil, wastewater, seasonings, etc. Specific examples of the object to be measured include tubes that make up the blood circuit of an artificial dialysis machine.

[0018] (Light receiving part 12) The light receiving unit 12 receives scattered light from the object being measured, which is emitted from the light emitting unit 11, and outputs a light receiving signal corresponding to the intensity of the scattered light.

[0019] The light-receiving unit 12, for example, receives scattered light (in this case, reflected light) from a laser beam irradiated onto the object to be measured. The scattered light received by the light-receiving unit 12 includes, for example, scattered light scattered by blood flowing through tubes constituting an extracorporeal circulation blood circuit (particularly by red blood cells, which are moving scatterers contained in the blood), and scattered light scattered by stationary tissues such as tubes. The received signal is a signal obtained by converting the intensity of the scattered light received by the light-receiving unit 12 into the intensity of a current or voltage.

[0020] (Disturbance generation unit 13) The disturbance generation unit 13 generates a disturbance signal that causes the drive current supplied to the light-emitting unit 11 to fluctuate. The drive current is the current used to drive the light-emitting unit 11. For example, if the light-emitting unit 11 is a semiconductor laser, the light-emitting unit 11 oscillates according to the drive current. The disturbance signal is a signal that causes the drive current to fluctuate. The disturbance signal may, for example, be a square wave with a pulse duty cycle of 50%, repeating at a constant amplitude and a constant period.

[0021] (Adjustment section 14) The adjustment unit 14 adjusts the drive current based on the signal generated based on the received light signal and the disturbance signal. The signal generated based on the received light signal is a signal that indicates frequency information obtained by performing frequency analysis on the beat signal caused by the Doppler shift of the light emitted from the light-emitting unit 11, which is included in the received light signal.

[0022] The scattered light incident on the light-receiving unit 12 includes, for example, scattered light scattered by stationary tissue (e.g., tubes constituting an extracorporeal blood circulation circuit) and scattered light scattered by red blood cells contained in the blood, which are moving objects. The scattered light scattered by red blood cells exhibits a Doppler shift corresponding to the movement speed of the red blood cells.

[0023] Therefore, the scattered light from stationary tissue and the scattered light from red blood cells interfere with each other due to the coherence of the laser light. The received signal output from the light receiving unit 12 includes an optical beat signal resulting from this interference.

[0024] The adjustment unit 14 performs frequency analysis on the optical beat signal, for example, using digital signal processing (DSP), such as FFT (Fast Fourier Transform), to calculate the power spectrum P(f).

[0025] Then, the adjustment unit 14 calculates the mean power frequency (MPF) based on the power spectrum P(f), for example. Specifically, the adjustment unit 14 multiplies the power spectrum P(f) and the frequency vector f and integrates them over a specified bandwidth (here, f0 to f1) to calculate the first moment, 1stM = Σ{f·P(f)}. Next, the adjustment unit 14 integrates the power spectrum P(f) over a specified bandwidth (here, f0 to f1) to calculate Ps = Σ{P(f)}. Then, the adjustment unit 14 calculates the average frequency by dividing the first moment 1stM by the above Ps.

[0026] Furthermore, the relationship between the flow velocity of a fluid such as blood flowing inside the object being measured and its average frequency is such that the average frequency increases as the flow velocity increases. Therefore, as an example, the flow velocity of the fluid may be estimated from the average frequency calculated by the adjustment unit 14. In this case, the optical measurement device 1 constitutes a device for estimating the flow velocity of a scattered fluid using the so-called laser flowmetry method.

[0027] As an example, the adjustment unit 14 adds the disturbance signal to the signal generated based on the received light signal to generate a drive current. Here, the drive current supplied to the light-emitting unit 11 will oscillate slightly in synchronization with the disturbance signal. As a result, the average frequency calculated by the adjustment unit 14 will also oscillate slightly in synchronization with the disturbance signal.

[0028] Furthermore, the adjustment unit 14 is configured, for example, to include a multiplier (not shown). The average frequency calculated by the adjustment unit 14 is input to one side of the multiplier. The disturbance signal generated by the disturbance generation unit 13 is input to the other side of the multiplier. The multiplier calculates the phase difference between the average frequency and the disturbance signal by multiplying them together. In other words, the multiplier operates as a phase comparator.

[0029] With the above configuration, it is possible to easily compare the signal generated based on the received light signal with the disturbance signal.

[0030] Furthermore, the adjustment unit 14 adjusts the drive current based on the signal generated based on the received light signal and the disturbance signal, for example, so that the semiconductor laser, which is the light-emitting unit 11, oscillates in single mode.

[0031] In optical measurement devices that utilize the laser Doppler effect, such as optical measurement device 1, optical coherence is important. To improve measurement accuracy, it is necessary to maintain the laser oscillation in a single mode with high optical coherence. In the estimation of the flow rate of scattered fluid by the laser flowmetry method, when the laser oscillation state shifts from single mode to so-called multimode, where multiple oscillation wavelengths exist, the amplitude of the optical beat signal decreases due to the decrease in optical coherence, and consequently the measured signal-to-noise ratio (SNR) decreases.

[0032] When a semiconductor laser is oscillating in multimode, its power spectrum P1M(f) has fewer low-frequency components and more high-frequency components compared to the power spectrum P1(f) when it is oscillating in single mode. This is because, in multimode operation, the amplitude of the optical beat signal decreases due to reduced optical coherence. In particular, the increase in high-frequency components is thought to be related to impulsive noise caused by mode hopping. As a result, the average frequency of the power spectrum P1M(f) is greater than the average frequency of the power spectrum P1(f).

[0033] Normally, the higher the fluid velocity flowing inside the object being measured, the higher the average frequency. Therefore, when a semiconductor laser is oscillating in multimode, a higher fluid velocity is incorrectly estimated compared to when the semiconductor laser is oscillating in single mode, even though the actual fluid velocity is the same.

[0034] When the temperature of a semiconductor laser (LD (Laser Diode) temperature) changes, the oscillation mode of the semiconductor laser also changes between single-mode and multi-mode. For example, in the relationship between LD temperature and average frequency, the average frequency increases in the LD temperature range where the semiconductor laser oscillation mode is multi-mode. Also, as an example, in the relationship between LD temperature and average frequency, the average frequency decreases in the LD temperature range where the semiconductor laser oscillation mode is single-mode.

[0035] The temperature of a semiconductor laser changes due to the heat generated by the semiconductor laser itself. Here, the amount of heat generated by the semiconductor laser itself changes depending on the magnitude of the drive current supplied to the semiconductor laser.

[0036] If the oscillation mode of a semiconductor laser is locally multimode within the LD temperature range, then by increasing or decreasing the drive current supplied to the semiconductor laser, the amount of heat generated by the semiconductor laser will change, which will also change the temperature of the semiconductor laser and thus change the oscillation mode from multimode to single-mode.

[0037] As an example, consider the case where, as the LD temperature increases, the oscillation mode of the semiconductor laser, which is the light-emitting unit 11, shifts to multimode, and the average frequency increases. In this case, the minute oscillation of the average frequency calculated by the adjustment unit 14 is in phase with the disturbance signal. Therefore, the output of the multiplier of the adjustment unit 14 becomes a positive output. At this time, if the drive current supplied to the light-emitting unit 11 is reduced, the temperature of the light-emitting unit 11 decreases, and the oscillation mode of the light-emitting unit 11 shifts from multimode to single mode.

[0038] As another example, consider the case where, as the LD temperature decreases, the oscillation mode of the semiconductor laser, which is the light-emitting unit 11, shifts to multimode, and the average frequency increases. In this case, the minute oscillations of the average frequency calculated by the adjustment unit 14 are out of phase with the disturbance signal. Therefore, the output of the multiplier of the adjustment unit 14 becomes a negative output. At this time, if the drive current supplied to the light-emitting unit 11 is increased, the temperature of the light-emitting unit 11 rises, and the oscillation mode of the light-emitting unit 11 shifts from multimode to single mode.

[0039] With the above configuration, even if the oscillation mode of the semiconductor laser, which is the light-emitting unit 11, becomes a multi-mode unsuitable for measuring the flow velocity of blood flowing inside the object to be measured, the oscillation mode can be switched to a single mode suitable for measuring flow velocity by adjusting the drive current as described above. Therefore, with the above configuration, changes in the characteristics of the laser light emitted from the light-emitting unit 11 can be suppressed, and the flow velocity can be measured appropriately.

[0040] Furthermore, the adjustment unit 14 is further equipped with an amplitude changing unit 141.

[0041] (Amplitude changing section 141) The amplitude changing unit 141 changes the amplitude of the disturbance signal. For example, the amplitude changing unit 141 switches between a first disturbance application period in which the disturbance signal has a first amplitude and a second disturbance application period in which the disturbance signal has a second amplitude that is larger than the first amplitude. The disturbance application period is the period in which the disturbance signal is applied. Here, for example, the first disturbance application period may be longer than the second disturbance application period.

[0042] Figure 2 shows an example of changing the amplitude of a disturbance signal. In Figure 2, the vertical axis represents the magnitude of the disturbance signal, and the horizontal axis represents time. The amplitude changing unit 141 may, as an example, change the amplitude of the disturbance signal between a first amplitude, which is a small amplitude, and a second amplitude, which is a large amplitude, as shown in Figure 2. The large amplitude is the amplitude obtained by increasing the small amplitude. That is, the large amplitude is an amplitude that is larger than the small amplitude. Here, as an example, the large amplitude of the disturbance signal may consist of an upper large amplitude that increases the amplitude in the positive direction of the disturbance signal, and a lower large amplitude that increases the amplitude in the negative direction of the disturbance signal, as shown in Figure 2.

[0043] With the above configuration, multiple types of disturbance signal amplitudes can be set. Here, the degree of decrease or increase in the drive current supplied to the light-emitting unit 11 is calculated based on the oscillation of the average frequency obtained as a result of the fluctuation of the drive current due to the disturbance signal. For this reason, the magnitude of the disturbance signal amplitude is proportional to the amount of adjustment of the drive current, and the larger the amplitude, the greater the difference in average frequencies at both ends of the amplitude in multimode, so the sensitivity to the slope of the average frequency increases and the transition to single mode becomes faster. On the other hand, considering measurement accuracy, it is preferable that the amplitude of the disturbance be as small as possible as it has less impact on the measurement. In contrast, with the above configuration, by making the magnitude of the disturbance amplitude variable as a first amplitude and a second amplitude, it is possible to choose whether to prioritize high measurement accuracy or high sensitivity of drive current adjustment.

[0044] The first disturbance application period is the period during which the disturbance signal has a first amplitude. That is, the first disturbance application period is the period during which the disturbance signal has a small amplitude. The second disturbance application period is the period during which the disturbance signal has a large amplitude, which is larger than the small amplitude. That is, the second disturbance application period is the period during which the disturbance signal has a second amplitude, which is larger than the first amplitude. As an example, as shown in Figure 2, the first disturbance application period during which the disturbance signal has a small amplitude may be longer than the second disturbance application period during which the disturbance signal has a large amplitude. Furthermore, the amount of adjustment of the drive current obtained by the first disturbance application and the amount of adjustment of the drive current obtained by the second disturbance application may be calculated independently.

[0045] The above configuration allows for the temporary increase in the amplitude of the disturbance signal. While the ability to vary the amplitude allows for the selection of high measurement accuracy and high sensitivity in adjusting the drive current, prioritizing sensitivity and only using large amplitudes raises concerns about the impact on measurement accuracy. In contrast, with the above configuration, for example, if the second amplitude is larger than the first amplitude, the duration of the first disturbance application can be extended, i.e., the frequency of the second amplitude occurring can be reduced. This allows for the simultaneous achievement of sensitivity to avoid multimode interference while minimizing the adverse effects on measurement accuracy.

[0046] (Adjustment amount of drive current) As an example, the adjustment unit 14 changes the amount of adjustment of the drive current based on the amplitude of the disturbance signal changed by the amplitude changing unit 141.

[0047] Figure 3 shows an example of adjusting the drive current. ST1 to ST4 in Figure 3 all show examples of the relationship between the LD drive current and the average frequency. Here, the LD temperature may, for example, be changed in conjunction with the magnitude of the drive current (LD drive current) supplied to the semiconductor laser, which is the light-emitting unit 11.

[0048] As shown in ST1 of Figure 3, in a graph illustrating an example of the relationship between LD drive current and average frequency, two peaks may be adjacent, forming a local valley. Here, the drive current transitions towards the lower average frequency before and after the minute oscillation. Therefore, when the amplitude of the disturbance signal consists only of the width of the minute oscillation, i.e., the minute amplitude, if the width of this local valley is larger than the minute amplitude, the drive current may fall into the local valley located midway between the two peaks, and may become unable to exit multimode.

[0049] On the other hand, the disturbance signal whose amplitude has been changed by the amplitude changing unit 141 may have a second amplitude that is larger than the width of the local trough, as shown in ST1 in Figure 3, for example. Furthermore, the average frequencies obtained for the first amplitude and the second amplitude may be calculated independently. Now, consider the case where the drive current before oscillation due to the disturbance signal, i.e., the pre-oscillation current, drops into the local trough. In this case, the adjustment unit 14 detects the average frequency at the tip of the large amplitude (the position of the dotted circle in Figure 3). Here, as shown in ST2 in Figure 3, when the magnitude of the large amplitude is sufficiently large, the average frequency at the tip of the large amplitude becomes lower than the average frequency in the local trough. At this time, as shown in ST3 in Figure 3, the adjustment unit 14 changes the amount of current of the pre-oscillation current from the amount of current in the local trough to the amount of current at the tip of the large amplitude. Finally, as shown in ST4 in Figure 3, the pre-oscillation current descends from the base of the peak and reaches a single mode.

[0050] With the above configuration, even if the drive current drops into a local valley during adjustment, it is possible to escape the local valley and reach single mode. In conventional technology, once a local valley larger than the amplitude is reached, both the high-temperature and low-temperature sides become peaks, making it impossible to escape thereafter. As a result, the average frequency transitions to a value higher than it should be, and measurement accuracy deteriorates. However, by using a large amplitude in combination, it is possible to find the single-mode region outside the local valley, and by transitioning to that region, the local valley can be escaped, enabling more stable and accurate measurements.

[0051] (Flow of optical measurement method S1) The flow of the optical measurement method S1 will be explained with reference to Figure 4. The optical measurement method S1 is an optical measurement method in an optical measurement device 1 that includes a light-emitting unit 11 that irradiates light onto a measurement target through which a fluid is flowing, and a light-receiving unit 12 that receives scattered light from the measurement target and outputs a received signal corresponding to the intensity of the scattered light. Figure 4 is a flowchart showing an example of the flow of the optical measurement method S1. As shown in Figure 4, the optical measurement method S1 includes a disturbance generation step (step) S11 and an adjustment step (step) S12.

[0052] (Step S11) In step S11, the disturbance generation unit 13 generates a disturbance signal that causes the drive current supplied to the light-emitting unit 11 to fluctuate. The disturbance generation unit 13 has been described above, so its explanation is omitted here.

[0053] (Step S12) In step S12, the adjustment unit 14 adjusts the drive current based on the signal generated based on the received light signal and the disturbance signal. Here, the amplitude changing unit 141 changes the amplitude of the disturbance signal. The adjustment unit 14 and the amplitude changing unit 141 have been described above, so their explanation is omitted here.

[0054] [Embodiment 2] Other embodiments of the present invention will be described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0055] (Overview of Optical Measurement Device 1A) The optical measuring device 1A is similar to the optical measuring device 1 in Embodiment 1 in that it irradiates the object to be measured with light and measures the scattered light from the object to be measured.

[0056] (Configuration of optical measuring device 1A) Figure 5 is a block diagram showing an example configuration of the optical measuring device 1A. As shown in Figure 5, the optical measuring device 1A comprises a light-emitting unit 11, a light-receiving unit 12, a disturbance generation unit 13, and an adjustment unit 14.

[0057] (Light-emitting part 11) The light-emitting unit 11 irradiates light onto the object being measured through which the fluid is flowing. Here, the light-emitting unit 11 may be, for example, a semiconductor laser. The light-emitting unit 11 of the optical measuring device 1A has the same configuration as the light-emitting unit 11 of the optical measuring device 1, so its description is omitted here.

[0058] (Light receiving part 12) The light-receiving unit 12 receives scattered light from the object being measured, which is emitted from the light-emitting unit 11, and outputs a light-receiving signal corresponding to the intensity of the scattered light. The light-receiving unit 12 of the optical measuring device 1A has the same configuration as the light-receiving unit 12 of the optical measuring device 1, so its description is omitted here.

[0059] (Disturbance generation unit 13) The disturbance generation unit 13 generates disturbance signals that cause fluctuations in the drive current supplied to the light-emitting unit 11. The disturbance generation unit 13 in the optical measuring device 1A has the same configuration as the disturbance generation unit 13 in the optical measuring device 1, so its description is omitted here.

[0060] (Adjustment section 14) The adjustment unit 14 adjusts the drive current based on the signal generated based on the received light signal and the disturbance signal. The signal generated based on the received light signal is a signal that indicates frequency information obtained by performing frequency analysis on the beat signal caused by the Doppler shift of the light emitted from the light-emitting unit 11, which is included in the received light signal. Furthermore, as an example, the adjustment unit 14 adjusts the drive current based on the signal generated based on the received light signal and the disturbance signal so that the semiconductor laser, which is the light-emitting unit 11, oscillates in single mode.

[0061] The adjustment unit 14 of the optical measuring device 1A includes an amplitude changing unit 141, a light intensity determination unit 142, an upper limit limit unit 143, and a lower limit limit unit 144.

[0062] (Amplitude changing section 141) The amplitude changing unit 141 changes the amplitude of the disturbance signal. For example, the amplitude changing unit 141 switches between a first disturbance application period in which the disturbance signal has a first amplitude and a second disturbance application period in which the disturbance signal has a second amplitude that is larger than the first amplitude. The disturbance application period is the period in which the disturbance signal is applied. Here, for example, the first disturbance application period may be longer than the second disturbance application period.

[0063] Figure 6 shows an example of changing the amplitude of a disturbance signal. In Figure 6, the vertical axis represents the magnitude of the disturbance signal, and the horizontal axis represents time. The amplitude changing unit 141 may, as an example, change the amplitude of the disturbance signal between a first amplitude, which is a small amplitude, and a second amplitude, which is a large amplitude, as shown in Figure 6. The large amplitude is the amplitude obtained by increasing the small amplitude. That is, the large amplitude is an amplitude larger than the small amplitude.

[0064] With the above configuration, it is possible to set multiple types of amplitudes for disturbance signals.

[0065] The first disturbance application period is the period during which the disturbance signal has a first amplitude. That is, the first disturbance application period is the period during which the disturbance signal has a small amplitude. The second disturbance application period is the period during which the disturbance signal has a large amplitude, which is larger than the small amplitude. That is, the second disturbance application period is the period during which the disturbance signal has a second amplitude, which is larger than the first amplitude. As an example, as shown in Figure 6, the first disturbance application period during which the disturbance signal has a small amplitude may be longer than the second disturbance application period during which the disturbance signal has a large amplitude.

[0066] The above configuration allows for a temporary increase in the amplitude of the disturbance signal.

[0067] (Light amount determination unit 142) The light intensity determination unit 142 determines whether the light power of the light emitted by the light-emitting unit 11 is within the range of a specified light intensity. The specified light intensity is a predetermined upper and lower limit for the magnitude of the light power emitted by the light-emitting unit 11. Here, for example, the light-emitting unit 11 is driven according to a drive current that fluctuates due to a disturbance signal, so the range of the specified light intensity may be shown by the range of the magnitude of the corresponding disturbance signal, as shown in Figure 6. Alternatively, for example, the range of the specified light intensity may be shown by the range of the corresponding drive current.

[0068] The light intensity determination unit 142 acquires a detection signal corresponding to the light intensity of the light emitted by the light-emitting unit 11, for example, via a sensor. A specific example of such a sensor is a back monitor PD (Photo Detector). Based on the detection signal, the light intensity determination unit 142 then determines whether the light power of the light emitted by the light-emitting unit 11 is within the range of a specified light intensity. Here, the light intensity determination unit 142 compares the light power with the upper and lower limits of the specified light intensity.

[0069] (Upper limit section 143) The upper limit limiting unit 143 limits the upper limit of the drive current when the optical power exceeds a specified light intensity. Figure 7 shows an example of drive current adjustment when the optical power transitions to exceed the specified light intensity. A specific example of when the optical power transitions to exceed the specified light intensity is when the average frequency gradually decreases as the LD temperature rises. ST5, ST6, and ST7 in Figure 7 all show examples of the relationship between the LD drive current and the average frequency. As an example, consider the case where the average frequency is declining to the right and the drive current is transitioning towards the upper limit of the specified light intensity, as shown in ST5 in Figure 7. Here, as the LD drive current increases and the optical power gradually increases by adjusting the drive current which is controlled to lower the average frequency, the light intensity limit is reached as shown in ST6 in Figure 7. At this time, the upper limit limiting unit 143 limits the upper limit of the drive current so that the optical power does not exceed the specified light intensity range, even when the average frequency is in the lower direction, as shown in ST7 in Figure 7. Figure 8 shows the change in light intensity over time, which fluctuates according to the drive current that fluctuates with disturbance signals, and the specified light intensity range. Here, T1, T2, and T3 represent the temporal positions corresponding to ST5, ST6, and ST7 in Figure 7, respectively. As shown in Figure 8, even if the drive current is continuously adjusted, the light intensity can remain within the specified range without exceeding the upper limit.

[0070] The above configuration allows for limiting the amount of drive current to prevent excessive increases in light power. When measuring blood, applying excessively strong light power can damage the blood, so it is crucial to keep the light intensity within a certain range. On the other hand, simply stopping operation when the light intensity exceeds the limit prevents the drive current from being adjusted at the light intensity boundary, and even if multimodes occur at the light intensity boundary due to the influence of ambient temperature, etc., it cannot be detected. In contrast, the above configuration allows for proper adjustment of the drive current even at the light intensity boundary by limiting the light intensity while simultaneously performing adjustments for the current.

[0071] In response to the optical power exceeding the specified light intensity, the upper limit limit unit 143 reduces the drive current, for example, so that the optical power decreases and falls below the upper limit of the specified light intensity. Figures 9 and 10 show examples of adjustment of the drive current before and after oscillation when the optical power exceeds the specified light intensity. A specific example of when the optical power exceeds the specified light intensity is when the luminous efficiency of the LD changes due to the influence of ambient temperature, etc., and the light intensity changes even if the drive current is constant. ST8, ST9, and ST10 in Figure 9 all show examples of the relationship between the LD drive current and the average frequency. As an example, consider the case where the drive current takes a value close to the current amount corresponding to the upper limit of the specified light intensity, as shown in ST8 in Figure 9. Here, even if the drive current is constant, if the optical power increases due to a change in the luminous efficiency of the LD, etc., the range of the specified light intensity corresponding to the drive current moves in the direction of decreasing drive current, as shown in ST9 in Figure 9. At this time, the upper limit limit unit 143 reduces the drive current, as shown in ST10 in Figure 9, so that the optical power decreases and falls below the upper limit of the specified light intensity.

[0072] Figure 10 shows the change over time of the drive current that fluctuates due to the disturbance signal, and the change over time of the drive current before fluctuation due to the disturbance signal, i.e., the pre-fluctuation current. When the optical power exceeds the upper limit of the specified light intensity, the upper limit limiting unit 143 reduces the pre-fluctuation current, as shown in section T4 of Figure 10, as an example. Figure 11 shows an example of limiting the light intensity before and after fluctuation when the drive current is adjusted in response to the optical power exceeding the specified light intensity. For example, even if the drive current remains constant, the optical power of the LD may increase due to a change in the luminous efficiency of the LD, as shown in section T5 of Figure 11, and reach the upper limit of the specified light intensity. In this case, when the upper limit limiting unit 143 reduces the pre-fluctuation current, the rate of increase in the pre-fluctuation optical power slows down, as shown in section T6 of Figure 11. Even after the increase in the pre-fluctuation optical power stops, the upper limit limiting unit 143 continues to reduce the pre-fluctuation current, causing the optical power to decrease, and the pre-fluctuation optical power continues to decrease, as shown in section T7 of Figure 11. Subsequently, the optical power falls below the upper limit of the specified light intensity, as shown in section T8 of Figure 11. Here, the upper limit limiting unit 143 may, for example, reduce the drive current so that the optical power gradually decreases without abruptly changing it, causing it to fall below the upper limit of the specified light intensity.

[0073] The above configuration allows the light power to be changed in a decreasing direction so that it falls below the upper limit of the specified light intensity. When the object being measured is blood, applying too much light power above a certain level may damage the blood. Therefore, by continuing the oscillation while keeping the light intensity within a certain range, it becomes possible to correctly adjust the drive current even at the boundary of the specified light intensity. However, in the case where the average frequency is sloping downwards, as in ST9 in Figure 9, the adjustment of the drive current will try to shift the average frequency downwards, so even if the oscillation is continued, it will not be possible to return to the specified light intensity range. In contrast, the above configuration makes it possible to draw the light power into the specified light intensity range even if the specified light intensity range is in the opposite direction to the direction of the average frequency decrease. Furthermore, while abruptly returning to the light intensity range may cause the measured value to fluctuate, by gradually changing the current amount in the direction of the light intensity range, it is possible to smoothly transition to the light intensity range without the measured value fluctuating.

[0074] Furthermore, in response to the optical power exceeding the specified light intensity, the amplitude changing unit 141 controls the waveform of the disturbance signal, for example, so that the drive current does not exceed the current amount of the drive current before the disturbance signal causes fluctuation. In other words, when the optical power exceeds the upper limit of the specified light intensity, the amplitude changing unit 141 controls the waveform of the disturbance signal, for example, as shown in section T4 of Figure 10, so that the drive current does not exceed the current amount of the current before the fluctuation.

[0075] Figure 11 shows the time-dependent change in optical power fluctuating due to a disturbance signal, and the time-dependent change in optical power before fluctuation due to the disturbance signal, i.e., the pre-fluctuation optical power. As an example, as shown in sections T6 and T7 of Figure 11, the upper limit unit 143 may fluctuate the drive current so that it does not exceed the pre-fluctuation current even in sections where the optical power exceeds the specified light intensity, and also in the specified light intensity boundary section. Furthermore, as shown in section T8 of Figure 11, once the optical power enters the specified light intensity range, it may be returned to the oscillation in both positive and negative directions as in normal light intensity. In addition, when fluctuating without exceeding the fluctuation current at the specified light intensity boundary, the amplitude of the fluctuating disturbance signal may be increased.

[0076] The above configuration prevents the optical power from exceeding the upper limit of the specified light intensity significantly due to fluctuations caused by disturbance signals. In normal oscillation, the oscillation is performed by making the amplitude move in both positive and negative directions relative to the pre-oscillation current. However, with the above configuration, by making the oscillation at the light intensity boundary move in the direction relative to the pre-oscillation current and within the light intensity range, safer oscillation that suppresses exceeding the light intensity limit becomes possible. Furthermore, if the amplitude in the direction within the specified light intensity range is made, for example, twice the size of the normal amplitude, oscillation of the same magnitude as the amplitude in both positive and negative directions at normal light intensity becomes possible, and the same drive current adjustment as at normal light intensity becomes possible even at the upper limit boundary of the specified light intensity.

[0077] (Lower limit section 144) The lower limit limiting unit 144 limits the lower limit of the drive current when the optical power falls below a specified light intensity. Figure 12 shows an example of adjusting the drive current when the optical power transitions to a state below the specified light intensity. A specific example of when the optical power transitions to a state below the specified light intensity is when the average frequency gradually decreases as the LD temperature decreases. ST11, ST12, and ST13 in Figure 12 all show examples of the relationship between the LD drive current and the average frequency. As an example, consider the case where the average frequency is sloping downwards to the left and the drive current is transitioning towards the lower limit of the specified light intensity, as shown in ST11 in Figure 12. Here, as the LD drive current decreases and the optical power gradually decreases by adjusting the drive current which is controlled to lower the average frequency, the light intensity reaches the lower limit as shown in ST12 in Figure 12. At this time, the lower limit limiting unit 144 limits the lower limit of the drive current so that the optical power does not fall below the specified light intensity range, even when the average frequency is in the downward direction, as shown in ST13 in Figure 12. Figure 13 shows the time-dependent change in light intensity and the specified light intensity range, which fluctuates according to the drive current that is affected by disturbance signals. Here, T9, T10, and T11 correspond to the time positions ST11, ST12, and ST13 in Figure 12, respectively. As Figure 13 shows, even if the drive current is continuously adjusted, the light intensity can remain within the specified light intensity range without falling below the lower limit.

[0078] The above configuration allows for limiting the amount of drive current to prevent excessive reduction in optical power. If the optical power falls below the specified light intensity, the measured signal-to-noise ratio decreases, making it impossible to obtain measurement values ​​with sufficient accuracy. Therefore, maintaining optical power within the specified light intensity range is extremely important. With the above configuration, even if the adjustment direction of the drive current is below the specified light intensity range, the oscillation can continue while maintaining the optical power necessary for measurement, and the adjustment of the drive current can be continued.

[0079] In response to the optical power falling below the specified light intensity, the lower limit limit unit 144 increases the drive current, for example, so that the optical power changes in an increasing direction and exceeds the lower limit of the specified light intensity. Figures 14 and 15 show examples of adjustment of the drive current before and after oscillation when the optical power falls below the specified light intensity. A specific example of when the optical power falls below the specified light intensity is when the luminous efficiency of the LD changes due to aging or other factors, and the initial light intensity falls outside the range of the specified light intensity. As an example, consider the case where the drive current falls below the current amount corresponding to the lower limit of the specified light intensity, as shown in ST14 in Figure 14. In this case, the lower limit limit unit 144 increases the drive current, as shown in ST15 in Figure 14, so that the optical power changes in an increasing direction and exceeds the lower limit of the specified light intensity.

[0080] Figure 15 shows the change over time of the drive current that fluctuates due to the disturbance signal, and the change over time of the drive current before the fluctuation due to the disturbance signal, i.e., the pre-fluctuation current. When the optical power falls below the lower limit of the specified light intensity, the lower limit limit unit 144 increases the pre-fluctuation current, as shown in section T12 of Figure 15, as an example. At this time, the optical power changes in the increasing direction and exceeds the lower limit of the specified light intensity. Figure 16 shows an example of limiting the light intensity before and after fluctuation when the drive current is adjusted in accordance with the optical power falling below the specified light intensity. Here, as an example, when the optical power of the LD falls below the lower limit of the specified light intensity, the lower limit limit unit 144 may increase the drive current so that the optical power gradually increases without abruptly changing it, as shown in section T13 of Figure 16, so that it exceeds the lower limit of the specified light intensity.

[0081] The above configuration allows the optical power to be increased so that it exceeds the lower limit of the specified light intensity. If the optical power falls below the lower limit of the specified light intensity, the measured signal-to-noise ratio decreases and measurement values ​​with sufficient accuracy cannot be obtained. Therefore, by continuing the fluctuation while limiting the light intensity, it is possible to adjust the drive current even at the lower limit boundary of the specified light intensity. However, if the initial light intensity has already fallen below the lower limit of the specified light intensity due to aging or other reasons, it is not possible to return to the specified light intensity range. In contrast, with the above configuration, even if the initial light intensity is below the lower limit of the specified light intensity, it is possible to gradually increase the drive current to bring the optical power back into the specified light intensity range and transition to sufficient optical power to obtain the measured signal-to-noise ratio necessary for measurement. Furthermore, while abruptly returning to the light intensity range may cause the measurement values ​​to fluctuate, gradually increasing the value allows for a smooth transition back to the light intensity range without fluctuations in the measurement values.

[0082] Furthermore, in response to the optical power falling below a specified light intensity, the amplitude changing unit 141 controls the waveform of the disturbance signal, for example, so that the drive current does not fall below the current amount of the drive current before the disturbance signal causes fluctuation. In other words, when the optical power falls below the lower limit of the specified light intensity, the amplitude changing unit 141 controls the waveform of the disturbance signal, for example, as shown in section T12 of Figure 15, so that the drive current does not fall below the current amount of the current before the fluctuation.

[0083] Figure 16 shows the change over time of the optical power fluctuating due to the disturbance signal, and the change over time of the optical power before the fluctuation due to the disturbance signal, i.e., the pre-fluctuation optical power. As an example, as shown in section T13 of Figure 16, when the optical power of the LD falls below the lower limit of the specified light intensity, the lower limit limit unit 144 may fluctuate the drive current so that it does not fall below the pre-fluctuation current. As shown in section T14 of Figure 16, even in sections where the light intensity outside and inside the specified light intensity range are mixed at the specified light intensity boundary, the lower limit limit unit 144 may fluctuate the drive current so that it does not fall below the pre-fluctuation current. Furthermore, as shown in section ST15 of Figure 14, once the optical power enters the specified light intensity range, it may return to the fluctuation in both positive and negative directions as at normal light intensity. In addition, when fluctuating without falling below the fluctuation current at the specified light intensity boundary, the amplitude of the fluctuating disturbance signal may be increased.

[0084] The above configuration prevents the optical power from falling significantly below the lower limit of the specified light intensity due to fluctuations caused by disturbance signals. If the optical power falls below the lower limit of the specified light intensity, the measured signal-to-noise ratio decreases, and measurement values ​​with sufficient accuracy cannot be obtained. Therefore, maintaining the optical power within the specified light intensity range is extremely important. In normal oscillation, oscillation is performed by making the amplitude oscillate in both positive and negative directions relative to the pre-oscillation current. However, with the above configuration, even below the specified light intensity or at the lower limit boundary of the specified light intensity, oscillation is performed in the direction relative to the pre-oscillation current and within the light intensity range, enabling more accurate measurements with suppressed light intensity reduction. Furthermore, if the amplitude in the direction within the specified light intensity range is made, for example, twice the size of the normal amplitude, oscillation of the same magnitude as the amplitude in both positive and negative directions at normal light intensity becomes possible, and the same drive current adjustment as at normal light intensity becomes possible even at the lower limit boundary of the specified light intensity.

[0085] (Adjustment amount of drive current near the boundary of the specified light intensity) As an example, the adjustment unit 14 changes the amount of adjustment of the drive current based on the amplitude of the disturbance signal changed by the amplitude changing unit 141. Figure 17 shows an example of drive current adjustment when the amount of current corresponding to the boundary of the specified light intensity is included in the section corresponding to multimode. As an example, consider the case where the amount of current corresponding to the lower limit of the specified light intensity is on the mountainside corresponding to multimode, as shown in ST16 in Figure 17. Here, the drive current transitions in the direction of the lower average frequency before and after the minute oscillation. Therefore, when the amplitude of the disturbance signal consists only of the width of the minute oscillation, i.e., the minute amplitude, if the width of the section from the mountaintop corresponding to multimode to the amount of current corresponding to the lower limit of the specified light intensity (hereinafter referred to as the "mountaintop lower limit section") is larger than the minute amplitude, the drive current may remain at the amount of current corresponding to the lower limit of the specified light intensity and may not be able to exit multimode.

[0086] On the other hand, the disturbance signal whose amplitude has been changed by the amplitude changing unit 141 may have a second amplitude that is larger than the width of the lower limit section of the peak, as shown in ST16 of Figure 17, for example. Furthermore, the average frequencies obtained for the first amplitude and the second amplitude may be calculated independently. Now, consider the case where the pre-oscillation current takes the amount of current corresponding to the lower limit of the specified light intensity. In this case, the adjustment unit 14 detects the average frequency at the tip of the large amplitude (the position of the dotted circle in Figure 17). Here, as shown in ST17 of Figure 17, when the magnitude of the large amplitude is sufficiently large, the average frequency at the tip of the large amplitude becomes lower than the average frequency at the lower limit of the specified light intensity. At this time, as shown in ST18 of Figure 17, the adjustment unit 14 changes the amount of current of the pre-oscillation current from the amount of current corresponding to the lower limit of the specified light intensity to the amount of current at the tip of the large amplitude. Finally, as shown in ST19 of Figure 17, the pre-oscillation current descends the base of the peak corresponding to the multimode and reaches the single mode.

[0087] With the above configuration, when adjusting the drive current, even if the boundary of the specified light intensity is located on the mountain slope corresponding to multimode, it is possible to escape the multimode on that boundary and reach single mode. In addition, the luminous efficiency of the LD may change due to the influence of ambient temperature, etc., during measurement, and the multimode peak itself may shift. Even if it is single mode at the start of measurement, for example, if the position of the multimode peak gradually moves toward the lower temperature, the LD current adjustment will gradually shift toward the lower temperature in order to maintain single mode, but once it reaches the light intensity boundary it cannot move any further and will climb onto the mountain slope of the multimode that has shifted to the light intensity boundary. Even in such cases, with the above configuration, it is possible to detect the plain beyond the multimode beyond the large amplitude and change the current amount to reach single mode.

[0088] (Controlling large amplitude waveforms in disturbance signals) The control of large amplitude waveforms in disturbance signals will be explained with reference to Figures 6 and 18. Figure 18 shows an example of adjusting the drive current with large amplitude waveform control. Specifically, Figure 18 shows an example of adjusting the drive current when the pre-oscillation current is increased from the current amount corresponding to the lower limit of the specified light intensity, i.e., the lower limit of the drive current, to the current amount corresponding to the upper limit of the specified light intensity, i.e., the upper limit of the drive current. In Figure 18, solid circles indicate the position of the pre-oscillation current, and dotted circles indicate the position of the peak of the large amplitude.

[0089] As an example, the amplitude changing unit 141 controls the waveform of the disturbance signal so that when the amplitude is increased, the drive current fluctuates so that the optical power does not exceed the upper limit of the specified optical intensity. As an example, the drive current at large amplitudes may be set so that the difference between the optical intensity before fluctuation and the optical intensity after large amplitude, i.e., the optical intensity width at large amplitudes, is less than or equal to half of the specified optical intensity range, and when the optical intensity of the current before fluctuation is greater than the center value of the upper and lower limits of optical intensity, the amplitude changing unit 141 may control the amplitude of the disturbance signal to increase in the negative direction, as shown in ST21 in Figures 6 and 18.

[0090] The above configuration ensures that even when disturbance signals cause large-amplitude fluctuations in the drive current, the light intensity does not exceed the upper limit of the specified light intensity. When measuring blood, applying excessively strong light power can damage the blood, so it is crucial to keep the light intensity within a certain range. When causing large-amplitude fluctuations in the drive current due to disturbance signals, it is also necessary to keep the fluctuations within this specified light intensity range. The above configuration makes it possible to achieve both light power control within the specified light intensity range and control of local valleys caused by large amplitude fluctuations.

[0091] Furthermore, the amplitude changing unit 141 controls the waveform of the disturbance signal so that, for example, when the amplitude is increased, the drive current fluctuates so that the optical power does not fall below the lower limit of the specified optical intensity. For example, the drive current at large amplitudes may be set so that the difference between the optical intensity before fluctuation and the optical intensity after large amplitude, i.e., the optical intensity width at large amplitude, is less than or equal to half of the specified optical intensity range, and when the optical intensity of the current before fluctuation is less than the center value of the upper and lower limits of optical intensity, the amplitude changing unit 141 may control the amplitude of the disturbance signal to increase in the positive direction, as shown in ST20 in Figures 6 and 18.

[0092] The above configuration ensures that even when disturbance signals cause large-amplitude fluctuations in the drive current, the light intensity does not fall below the lower limit of the specified light intensity. Controlling the optical power within the specified light intensity range is crucial to maintaining the signal-to-noise ratio necessary for obtaining measurement values ​​with sufficient accuracy. On the other hand, when causing large-amplitude fluctuations in the drive current due to disturbance signals, these fluctuations must remain within this specified light intensity range. The above configuration makes it possible to achieve both optical power control within the specified light intensity range and control for escaping local valleys caused by large amplitude fluctuations.

[0093] Furthermore, regarding the configuration of the adjustment unit 14 of the optical measuring device 1A, other than those described above, the configuration is the same as that of the adjustment unit 14 of the optical measuring device 1, so a detailed explanation is omitted here.

[0094] (Flowchart of optical measurement method S1A) The flow of the optical measurement method S1A will be explained with reference to Figure 19. The optical measurement method S1A is an optical measurement method in an optical measurement device 1A that includes a light-emitting unit 11 that irradiates light onto a measurement target through which a fluid is flowing, and a light-receiving unit 12 that receives scattered light from the measurement target and outputs a light-receiving signal corresponding to the intensity of the scattered light. Figure 19 is a flowchart showing an example of the flow of the optical measurement method S1A. As shown in Figure 19, the optical measurement method S1A includes a disturbance generation step (step) S11, an amplitude change step (step) S121, light quantity determination steps (steps) S122 and S124, an upper limit limit step (step) S123, and a lower limit limit step (step) S125.

[0095] (Step S11) In step S11, the disturbance generation unit 13 generates a disturbance signal that causes the drive current supplied to the light-emitting unit 11 to fluctuate. The disturbance generation unit 13 has been described above, so its explanation is omitted here.

[0096] (Steps S121~S125) In steps S121 to S125, the adjustment unit 14 adjusts the drive current based on the signal generated based on the received light signal and the disturbance signal. The configuration of the adjustment unit 14 has been described above, so it will not be explained here.

[0097] (Step S121) In step S121, the amplitude changing unit 141 changes the amplitude of the disturbance signal. The amplitude changing unit 141 has been described above, so its explanation is omitted here.

[0098] (Steps S122 and S124) In steps S122 and S124, the light intensity determination unit 142 determines whether the light power of the light emitted by the light-emitting unit 11 is within the range of the specified light intensity. The light intensity determination unit 142 has been described above, so its explanation is omitted here.

[0099] (Step S122) In step S122, the light intensity determination unit 142 determines whether the light power of the light emitted by the light-emitting unit 11 exceeds the upper limit of the specified light intensity. If it exceeds the upper limit (step S122: YES), the process proceeds to step S123. If it does not exceed the upper limit (step S122: NO), the process proceeds to step S124.

[0100] (Step S123) In step S123, the upper limit limiting unit 143 limits the upper limit amount of the drive current. The upper limit limiting unit 143 has been described above, so its explanation is omitted here.

[0101] (Step S124) In step S124, the light intensity determination unit 142 determines whether the light power of the light emitted by the light-emitting unit 11 falls below the lower limit of the specified light intensity. If it falls below the lower limit (step S124: YES), the process proceeds to step S125. If it does not fall below the lower limit (step S124: NO), the process ends.

[0102] (Step S125) In step S125, the lower limit limiting unit 144 limits the lower limit amount of the drive current. The lower limit limiting unit 144 has been described above, so its explanation is omitted here.

[0103] [Embodiment 3] Other embodiments of the present invention will be described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0104] (Overview of Optical Measurement Device 1B) The optical measuring device 1B, like the optical measuring device 1 in Embodiment 1 and the optical measuring device 1A in Embodiment 2, is a device that irradiates a target to be measured with light and measures the scattered light from the target to be measured.

[0105] (Configuration of optical measuring device 1B) Figure 20 is a block diagram showing an example configuration of the optical measuring device 1B. As shown in Figure 20, the optical measuring device 1B includes a light-emitting unit 11, a light-receiving unit 12, a disturbance generation unit 13, an adjustment unit 14, a temperature control unit 15, and a target temperature changing unit 16.

[0106] (Light-emitting part 11) The light-emitting unit 11 irradiates light onto the object being measured through which the fluid is flowing. Here, the light-emitting unit 11 may be, for example, a semiconductor laser. The light-emitting unit 11 of the optical measuring device 1B has the same configuration as the light-emitting units 11 of the optical measuring devices 1 and 1A, so its description is omitted here.

[0107] (Light receiving part 12) The light-receiving unit 12 receives scattered light from the object being measured, which is emitted from the light-emitting unit 11, and outputs a light-receiving signal corresponding to the intensity of the scattered light. The light-receiving unit 12 of the optical measuring device 1B has the same configuration as the light-receiving units 12 of the optical measuring devices 1 and 1A, so its description is omitted here.

[0108] (Disturbance generation unit 13) The disturbance generation unit 13 generates disturbance signals that cause fluctuations in the drive current supplied to the light-emitting unit 11. The disturbance generation unit 13 in the optical measuring device 1B has the same configuration as the disturbance generation unit 13 in the optical measuring devices 1 and 1A, so its description is omitted here.

[0109] (Adjustment section 14) The adjustment unit 14 adjusts the drive current based on the signal generated based on the received light signal and the disturbance signal. The signal generated based on the received light signal is a signal that indicates frequency information obtained by performing frequency analysis on the beat signal caused by the Doppler shift of the light emitted from the light-emitting unit 11, which is included in the received light signal. In addition, the adjustment unit 14 changes the amount of adjustment of the drive current based on the amplitude of the disturbance signal changed by the amplitude changing unit 141, as an example.

[0110] The adjustment unit 14 of the optical measuring device 1B includes an amplitude changing unit 141, a light intensity determination unit 142, an upper limit limit unit 143, and a lower limit limit unit 144. The other components of the adjustment unit 14 of the optical measuring device 1B are the same as those of the adjustment unit 14 of the optical measuring device 1A, so their explanation is omitted here.

[0111] (Amplitude changing section 141) The amplitude changing unit 141 changes the amplitude of the disturbance signal. For example, the amplitude changing unit 141 switches between a first disturbance application period in which the disturbance signal has a first amplitude and a second disturbance application period in which the disturbance signal has a second amplitude greater than the first amplitude. Here, for example, the first disturbance application period may be longer than the second disturbance application period. For example, the amplitude changing unit 141 controls the waveform of the disturbance signal so that when the amplitude is increased, the drive current fluctuates so that the optical power does not exceed the upper limit of the specified light amount. Also, for example, the amplitude changing unit 141 controls the waveform of the disturbance signal so that when the amplitude is increased, the drive current fluctuates so that the optical power does not fall below the lower limit of the specified light amount. The amplitude changing unit 141 provided in the optical measuring device 1B has the same configuration as the amplitude changing unit 141 provided in the optical measuring device 1A, so its description is omitted here.

[0112] (Light amount determination unit 142) The light intensity determination unit 142 determines whether the light power of the light emitted by the light-emitting unit 11 is within the range of a specified light intensity. The light intensity determination unit 142 in the light measuring device 1B has the same configuration as the light intensity determination unit 142 in the light measuring device 1A, so its explanation is omitted here.

[0113] (Upper limit section 143) The upper limit limiting unit 143 limits the upper limit of the drive current when the optical power exceeds a specified light intensity. In response to the optical power exceeding the specified light intensity, the upper limit limiting unit 143 reduces the drive current, for example, so that the optical power decreases and falls below the upper limit of the specified light intensity. Also, in response to the optical power exceeding the specified light intensity, the amplitude changing unit 141 controls the waveform of the disturbance signal, for example, so that the drive current does not fluctuate above the current amount of the drive current before fluctuation due to the disturbance signal. The upper limit limiting unit 143 in the optical measuring device 1B has the same configuration as the upper limit limiting unit 143 in the optical measuring device 1A, so its explanation is omitted here.

[0114] (Lower limit section 144) The lower limit unit 144 limits the lower limit of the drive current when the optical power falls below a specified light intensity. In response to the optical power falling below the specified light intensity, the lower limit unit 144 increases the drive current, for example, so that the optical power changes in an increasing direction and exceeds the lower limit of the specified light intensity. Also, in response to the optical power falling below the specified light intensity, the amplitude changing unit 141 controls the waveform of the disturbance signal, for example, so that the drive current does not fall below the current amount of the drive current before the disturbance signal fluctuation. The lower limit unit 144 of the optical measuring device 1B has the same configuration as the lower limit unit 144 of the optical measuring device 1A, so its explanation is omitted here.

[0115] (Temperature control unit 15) The temperature control unit 15 controls the temperature of the light-emitting unit 11. For example, the temperature control unit 15 controls the temperature of the light-emitting unit 11 so that it approaches a target temperature. Here, the target temperature is the target temperature at which the temperature control unit 15 controls the temperature of the light-emitting unit 11. For example, the target temperature is the temperature at which the semiconductor laser, which is the light-emitting unit 11, is set to emit in single mode. Alternatively, for example, the target temperature may be set in advance.

[0116] The temperature control unit 15, for example, detects the temperature of the light-emitting unit 11 via a thermistor or the like. Next, the temperature control unit 15, for example, calculates a temperature error, which is the difference between the detected temperature and the target temperature. Then, the temperature control unit 15, for example, controls the temperature of the light-emitting unit 11 based on the calculated temperature error. Specifically, if the detected temperature is above the target temperature, the temperature control unit 15 cools the light-emitting unit 11 to bring its temperature closer to the target temperature. Also, specifically, if the detected temperature is below the target temperature, the temperature control unit 15 heats the light-emitting unit 11 to bring its temperature closer to the target temperature. Here, the temperature control unit 15 may, for example, control the temperature of the light-emitting unit 11 using a Peltier element or the like.

[0117] With the above configuration, the temperature of the light-emitting section 11 can be brought closer to the target temperature.

[0118] When the temperature control unit 15 detects the temperature of the light-emitting unit 11 via a thermistor, the temperature detected by the thermistor does not change instantaneously due to the heat capacity of the component connecting the light-emitting unit 11 and the thermistor (i.e., the time response is slow). On the other hand, it is relatively easy to locally change the temperature of the light-emitting unit 11 by changing the drive current (i.e., the time response is fast). Therefore, it is considered that local temperature changes of the light-emitting unit 11 due to adjustment of the drive current do not affect the temperature control of the light-emitting unit 11 by the temperature control unit 15. In other words, it is considered that the adjustment of the drive current and the temperature control do not interfere with each other.

[0119] (Target temperature change unit 16) The target temperature changing unit 16 changes the target temperature based on the adjustment result of the drive current by the adjustment unit 14. For example, if the adjustment unit 14 adjusts the drive current in a direction that decreases the drive current, the target temperature changing unit 16 will lower the target temperature. Also, for example, if the adjustment unit 14 adjusts the drive current in a direction that increases the drive current, the target temperature changing unit 16 will raise the target temperature.

[0120] Figures 21 to 23 show an example of the relationship between LD temperature, i.e., the temperature of the light-emitting unit 11, and the average frequency. Consider the example in Figure 21 where the target temperature is set to TE1°C. Here, after setting the target temperature, the relationship between the average frequency and the LD temperature may change due to aging degradation of the light-emitting unit 11, etc. In this case, as shown in Figure 21, the average frequency does not become minimum at the target temperature TE1°C, and therefore, the oscillation mode of the semiconductor laser, which is the light-emitting unit 11, may not be single-mode at the target temperature TE1°C. RL in Figure 21 is the range of LD temperature when the drive current is adjusted so that the optical power is within the range of the specified light intensity. That is, RL shows the range on the LD temperature axis in which the drive current can be adjusted under the specified light intensity conditions. RU in Figure 21 shows the range of LD temperature that changes with the actual adjustment of the drive current. That is, RU shows the actual adjustment range of the drive current on the LD temperature axis.

[0121] In the following example, we consider a case where the adjustment unit 14 adjusts the drive current in a direction that reduces the drive current in order to transition the oscillation mode to single mode, thereby lowering the LD temperature. In this case, as the drive current decreases, the optical power of the light emitted from the light-emitting unit 11 also decreases. However, if the optical power decreases to below a specified amount before the oscillation mode transitions to single mode, the lower limit of the drive current is restricted, making it difficult to transition to single mode.

[0122] Therefore, when the adjustment unit 14 adjusts the drive current in a direction that decreases the drive current, the target temperature change unit 16 lowers the target temperature from TE1°C to TE2°C, as shown in Figure 21. As the target temperature change unit 16 lowers the target temperature, the LD temperature decreases. At this time, it is no longer necessary to lower the LD temperature solely by decreasing the drive current, so the drive current increases. As a result, the optical power of the light emitted from the light-emitting unit 11 also increases, and as shown in Figure 22, RL, which indicates the range in which the drive current can be adjusted, moves to a lower temperature. Also, as RL moves to a lower temperature, RU, which indicates the actual adjustment range of the drive current, can also move to a lower temperature, as shown in Figure 22. By repeating the above process by the target temperature change unit 16, as shown in Figure 23, the target temperature further decreases from TE2°C to TE3°C, and the temperature ranges RL and RU move to even lower temperatures. As a result, as shown in Figure 23, the LD temperature value with the minimum average frequency is included within the temperature range RU, and the oscillation mode shifts to single mode.

[0123] In the case where the adjustment unit 14 adjusts the drive current in a direction that increases the drive current in order to shift the oscillation mode of the semiconductor laser, which is the light-emitting unit 11, to single mode, thereby raising the LD temperature, the processing is the same as in the case described above, so the explanation is omitted here.

[0124] As an example, the target temperature changing unit 16 may increase the amount of change in the target temperature as the amount of change in the drive current increases.

[0125] With the above configuration, even if the relationship between the average frequency and the LD temperature in the light-emitting section 11 changes, the target temperature can be changed according to the state of the light-emitting section 11 after the change.

[0126] Furthermore, as an example, even when the limiting unit limits the amount of drive current, the amount of temperature change may be set based on the amount of change in the drive current before the limiting. That is, at the light intensity boundary, the amount of temperature change may be set based on the amount of LD adjustment current before current limiting, which is obtained as a result of controlling the waveform of the disturbance signal so that the drive current does not exceed the amount of drive current before the fluctuation caused by the disturbance signal, or so that the drive current does not fall below the amount of drive current before the fluctuation caused by the disturbance signal.

[0127] With the above configuration, even if the limiting unit does not actually change the amount of drive current and the optical power remains at the optical intensity boundary, the direction of temperature for transitioning to single mode can be detected with sufficient sensitivity, and the target temperature can be transitioned, so that the oscillation mode can be changed from multimode to single mode even at the optical intensity boundary.

[0128] Furthermore, the target temperature changing unit 16 may, as an example, further include a gain changing unit 161.

[0129] (Gain adjustment section 161) The gain changing unit 161 amplifies the amount of change in the target temperature when the limiting unit limits the amount of drive current. Here, the limiting unit is at least one of the upper limit limiting unit 143 and the lower limit limiting unit 144.

[0130] For example, if the limiting unit limits the amount of drive current, thereby reducing the amount of change in drive current, the amount of change in target temperature by the target temperature changing unit 16 will also decrease, potentially making it difficult to transition the oscillation mode from multimode to single mode in a short period of time. In this case, the gain changing unit 161, for example, increases the amount of change in target temperature.

[0131] With the above configuration, the period during which the oscillation mode is multimode can be made relatively short, and the oscillation mode can be transitioned from multimode to single mode in a relatively short period of time.

[0132] (Flowchart of optical measurement method S1B) The flow of the optical measurement method S1B will be explained with reference to Figure 24. The optical measurement method S1B is an optical measurement method in an optical measurement device 1B that includes a light-emitting unit 11 that irradiates light onto a measurement target through which a fluid is flowing, and a light-receiving unit 12 that receives scattered light from the measurement target and outputs a light-receiving signal corresponding to the intensity of the scattered light. Figure 24 is a flowchart showing an example of the flow of the optical measurement method S1B. As shown in Figure 24, the optical measurement method S1B includes a disturbance generation step (step) S11, an amplitude change step (step) S121, light quantity determination steps (steps) S122 and S124, an upper limit limit step (step) S123, a lower limit limit step (step) S125, a temperature control step (step) S13, and a target temperature change step (step) S14.

[0133] (Step S11) In step S11, the disturbance generation unit 13 generates a disturbance signal that causes the drive current supplied to the light-emitting unit 11 to fluctuate. The disturbance generation unit 13 has been described above, so its explanation is omitted here.

[0134] (Steps S121~S125) In steps S121 to S125, the adjustment unit 14 adjusts the drive current based on the signal generated based on the received light signal and the disturbance signal. The configuration of the adjustment unit 14 has been described above, so it will not be explained here.

[0135] (Step S121) In step S121, the amplitude changing unit 141 changes the amplitude of the disturbance signal. The amplitude changing unit 141 has been described above, so its explanation is omitted here.

[0136] (Steps S122 and S124) In steps S122 and S124, the light intensity determination unit 142 determines whether the light power of the light emitted by the light-emitting unit 11 is within the range of the specified light intensity. The light intensity determination unit 142 has been described above, so its explanation is omitted here.

[0137] (Step S122) In step S122, the light intensity determination unit 142 determines whether the light power of the light emitted by the light-emitting unit 11 exceeds the upper limit of the specified light intensity. If it exceeds the upper limit (step S122: YES), the process proceeds to step S123. If it does not exceed the upper limit (step S122: NO), the process proceeds to step S124.

[0138] (Step S123) In step S123, the upper limit limiting unit 143 limits the upper limit amount of the drive current. The upper limit limiting unit 143 has been described above, so its explanation is omitted here.

[0139] (Step S124) In step S124, the light intensity determination unit 142 determines whether the light power of the light emitted by the light-emitting unit 11 falls below the lower limit of the specified light intensity. If it falls below the lower limit (step S124: YES), the process proceeds to step S125. If it does not fall below the lower limit (step S124: NO), the process ends.

[0140] (Step S125) In step S125, the lower limit limiting unit 144 limits the lower limit amount of the drive current. The lower limit limiting unit 144 has been described above, so its explanation is omitted here.

[0141] (Step S13) In step S13, the temperature control unit 15 controls the temperature of the light-emitting unit 11. The temperature control unit 15 has been described above, so its explanation is omitted here.

[0142] (Step S14) In step S14, the target temperature changing unit 16 changes the target temperature based on the result of the adjustment of the drive current by the adjustment unit 14. The target temperature changing unit 16 has been described above, so its explanation is omitted here.

[0143] Furthermore, the above configurations enable the provision of stable medical care. Such effects contribute, for example, to achieving the United Nations' Sustainable Development Goals (SDGs), such as Goal 3, "Ensure healthy lives and promote well-being for all," and Goal 12, "Ensure responsible consumption and production."

[0144] [Examples of implementation using software] The functions of the optical measuring devices 1, 1A, and 1B (hereinafter referred to as "devices") can be realized by programs that cause computers to function as the devices, and by programs that cause computers to function as each control block of the devices.

[0145] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., memory) as hardware for executing the program. By executing the program using this control device and storage device, the functions described in each of the embodiments are realized.

[0146] The above program may be recorded on one or more computer-readable recording media, not temporary ones. These recording media may or may not be provided by the above device. In the latter case, the program may be supplied to the above device via any wired or wireless transmission medium.

[0147] Furthermore, some or all of the functions of each of the above control blocks can also be realized by logic circuits. For example, an integrated circuit in which logic circuits functioning as each of the above control blocks are formed is also included in the scope of the present invention. In addition, it is also possible to realize the functions of each of the above control blocks by, for example, a quantum computer.

[0148] Furthermore, each process described in the above embodiments may be performed by AI (Artificial Intelligence). In this case, the AI ​​may operate on the control device described above, or it may operate on other devices (for example, an edge computer or a cloud server).

[0149] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0150] 〔summary〕 An optical measuring device according to embodiment 1 of the present invention comprises: a light-emitting unit that irradiates light onto a measuring object through which a fluid is flowing; a light-receiving unit that receives scattered light from the measuring object and outputs a light-receiving signal corresponding to the intensity of the scattered light; a disturbance generation unit that generates a disturbance signal that causes the drive current supplied to the light-emitting unit to fluctuate; and an adjustment unit that adjusts the drive current based on the signal generated based on the light-receiving signal and the disturbance signal, wherein the adjustment unit further comprises an amplitude changing unit that changes the amplitude of the disturbance signal.

[0151] An optical measuring device according to aspect 2 of the present invention includes: a light-emitting unit that irradiates light onto a measuring object through which a fluid is flowing; a light-receiving unit that receives scattered light from the measuring object and outputs a light-receiving signal corresponding to the intensity of the scattered light; a disturbance generation unit that generates a disturbance signal that causes the drive current supplied to the light-emitting unit to fluctuate; and an adjustment unit that adjusts the drive current based on the signal generated based on the light-receiving signal and the disturbance signal, wherein the adjustment unit further includes an amplitude changing unit that changes the amplitude of the disturbance signal; a light intensity determination unit that determines whether the light power of the light irradiated by the light-emitting unit is within a specified light intensity range; an upper limit limiting unit that limits the upper limit of the drive current when the light power exceeds the specified light intensity; and a lower limit limiting unit that limits the lower limit of the drive current when the light power falls below the specified light intensity.

[0152] In the optical measuring device according to embodiment 3 of the present invention, in embodiment 1 or 2 above, the adjustment unit changes the amount of adjustment of the drive current based on the amplitude of the disturbance signal changed by the amplitude changing unit.

[0153] In the optical measuring device according to embodiment 4 of the present invention, in embodiment 1 or 2 above, the amplitude changing unit switches between a first disturbance application period in which the disturbance signal has a first amplitude and a second disturbance application period in which the disturbance signal has a second amplitude greater than the first amplitude.

[0154] In the optical measuring device according to embodiment 5 of the present invention, in embodiment 2, the amplitude changing unit controls the waveform of the disturbance signal such that when the amplitude is increased, the drive current fluctuates so that the optical power does not exceed the upper limit of the specified amount of light.

[0155] In the optical measuring device according to embodiment 6 of the present invention, in embodiment 2 above, when the optical power exceeds the specified amount of light, the amplitude changing unit controls the waveform of the disturbance signal so that the drive current does not exceed the amount of drive current before oscillation due to the disturbance signal.

[0156] In the optical measuring device according to embodiment 7 of the present invention, in embodiment 2 above, when the optical power exceeds the specified amount of light, the upper limit limit unit reduces the drive current so that the optical power changes in the decreasing direction and falls below the upper limit of the specified amount of light.

[0157] In the optical measuring device according to embodiment 8 of the present invention, in embodiment 2 above, the amplitude changing unit controls the waveform of the disturbance signal such that when the amplitude is increased, the drive current fluctuates so that the optical power does not fall below the lower limit of the specified light quantity.

[0158] In the optical measuring device according to embodiment 9 of the present invention, in embodiment 2 above, when the optical power falls below the specified amount of light, the amplitude changing unit controls the waveform of the disturbance signal so that the drive current does not fall below the amount of drive current before the disturbance signal causes fluctuation.

[0159] In the optical measuring device according to embodiment 10 of the present invention, in embodiment 2 above, when the optical power falls below the specified amount of light, the lower limit limit unit increases the drive current so that the optical power changes in an increasing direction and exceeds the lower limit of the specified amount of light.

[0160] An optical measurement method according to embodiment 11 of the present invention is an optical measurement method in an optical measurement device comprising: a light-emitting unit that irradiates light onto a measurement target through which a fluid is flowing; and a light-receiving unit that receives scattered light from the measurement target of the irradiated light and outputs a received signal corresponding to the intensity of the scattered light, the method comprising: a disturbance generation step that generates a disturbance signal that causes the drive current supplied to the light-emitting unit to fluctuate; and an adjustment step that adjusts the drive current based on the signal generated based on the received signal and the disturbance signal, wherein the adjustment step further includes an amplitude changing step that changes the amplitude of the disturbance signal.

[0161] A method for measuring light according to embodiment 12 of the present invention is a method for measuring light in a light measuring device comprising: a light-emitting unit that irradiates light onto a measurement target through which a fluid is flowing; and a light-receiving unit that receives scattered light from the measurement target of the irradiated light and outputs a light-receiving signal corresponding to the intensity of the scattered light, the method comprising: a disturbance generation step that generates a disturbance signal that causes the drive current supplied to the light-emitting unit to fluctuate; and an adjustment step that adjusts the drive current based on the signal generated based on the light-receiving signal and the disturbance signal, wherein the adjustment step further comprises: an amplitude change step that changes the amplitude of the disturbance signal; a light intensity determination step that determines whether the light power of the light irradiated by the light-emitting unit is within a specified light intensity range; an upper limit limit step that limits the upper limit of the drive current when the light power exceeds the specified light intensity; and a lower limit limit step that limits the lower limit of the drive current when the light power falls below the specified light intensity.

[0162] A computer program according to embodiment 13 of the present invention provides a computer for an optical measuring device comprising: a light-emitting unit that irradiates light onto a measuring object through which a fluid is flowing; and a light-receiving unit that receives scattered light from the measuring object and outputs a light-receiving signal corresponding to the intensity of the scattered light. The computer is configured to function as a disturbance generation unit that generates a disturbance signal to cause fluctuations in the drive current supplied to the light-emitting unit; and an adjustment unit that adjusts the drive current based on the signal generated based on the light-receiving signal and the disturbance signal. The adjustment unit is further configured to function as an amplitude changing unit that changes the amplitude of the disturbance signal.

[0163] A computer program according to embodiment 14 of the present invention provides a computer for an optical measuring device comprising: a light-emitting unit that irradiates light onto a measuring object through which a fluid is flowing; and a light-receiving unit that receives scattered light from the measuring object and outputs a light-receiving signal corresponding to the intensity of the scattered light. The computer is configured to function as: a disturbance generation unit that generates a disturbance signal that causes fluctuations in the drive current supplied to the light-emitting unit; and an adjustment unit that adjusts the drive current based on the signal generated based on the light-receiving signal and the disturbance signal. The adjustment unit is further configured to function as: an amplitude changing unit that changes the amplitude of the disturbance signal; a light intensity determination unit that determines whether the light power of the light irradiated by the light-emitting unit is within a specified light intensity range; an upper limit limiting unit that limits the upper limit of the drive current when the light power exceeds the specified light intensity; and a lower limit limiting unit that limits the lower limit of the drive current when the light power falls below the specified light intensity. [Explanation of Symbols]

[0164] 1, 1A, 1B Optical measuring device 11 Light-emitting part 12 Light receiving section 13 Disturbance generation unit 14 Adjustment section 15 Temperature control unit 16 Target temperature change unit 141 Amplitude changing section 142 Light amount determination section 143 Upper Limit Section 144 Lower limit section 161 Gain Change Section

Claims

1. A light-emitting unit that illuminates the object being measured through which the fluid is flowing, A light receiving unit receives scattered light from the object to be measured and outputs a light receiving signal corresponding to the intensity of the scattered light. A disturbance generation unit generates a disturbance signal that causes the drive current supplied to the light-emitting unit to fluctuate, The system includes an adjustment unit that adjusts the drive current based on a signal generated based on the light reception signal and the disturbance signal, The adjustment unit further comprises an amplitude changing unit that changes the amplitude of the disturbance signal. An optical measuring device characterized by the following features.

2. A light-emitting unit that illuminates the object being measured through which the fluid is flowing, A light receiving unit receives scattered light from the object to be measured and outputs a light receiving signal corresponding to the intensity of the scattered light. A disturbance generation unit generates a disturbance signal that causes the drive current supplied to the light-emitting unit to fluctuate, The system includes an adjustment unit that adjusts the drive current based on a signal generated based on the light reception signal and the disturbance signal, The adjustment unit is, An amplitude changing unit that changes the amplitude of the disturbance signal, A light intensity determination unit that determines whether the light power of the light emitted by the light-emitting unit is within a specified light intensity range, When the optical power exceeds the specified amount of light, an upper limit limiting unit limits the upper limit of the drive current, When the light power falls below the specified light intensity, a lower limit limit unit limits the lower limit amount of the drive current, An optical measuring device characterized by further comprising the following features.

3. The adjustment unit is characterized by changing the amount of adjustment of the drive current based on the amplitude of the disturbance signal that has been changed by the amplitude changing unit. The optical measuring device according to claim 1 or 2.

4. The amplitude changing unit is characterized by switching between a first disturbance application period in which the disturbance signal has a first amplitude and a second disturbance application period in which the disturbance signal has a second amplitude greater than the first amplitude. The optical measuring device according to claim 1 or 2.

5. The amplitude changing unit is characterized in that, when the amplitude is increased, it controls the waveform of the disturbance signal so that the drive current fluctuates in such a way that the optical power does not exceed the upper limit of the specified light intensity. The optical measuring device according to claim 2.

6. In response to the light power exceeding the specified light quantity, The amplitude changing unit is characterized by controlling the waveform of the disturbance signal so that the drive current does not exceed the amount of drive current before oscillation due to the disturbance signal. The optical measuring device according to claim 2.

7. In response to the light power exceeding the specified light quantity, The upper limit limiting unit is characterized by reducing the drive current so that the light power changes in a decreasing direction and falls below the upper limit of the specified light quantity. The optical measuring device according to claim 2.

8. The amplitude changing unit is characterized by controlling the waveform of the disturbance signal such that when the amplitude is increased, the drive current fluctuates so that the optical power does not fall below the lower limit of the specified light intensity. The optical measuring device according to claim 2.

9. In accordance with the fact that the light power falls below the specified light quantity, The amplitude changing unit is characterized by controlling the waveform of the disturbance signal so that the drive current does not fall below the amount of drive current before oscillation due to the disturbance signal. The optical measuring device according to claim 2.

10. In accordance with the fact that the light power falls below the specified light quantity, The lower limit limiting unit is characterized by increasing the drive current so that the light power changes in an increasing direction and exceeds the lower limit of the specified light quantity. The optical measuring device according to claim 2.

11. An optical measurement method in an optical measurement device comprising: a light-emitting unit that irradiates light onto a measurement target through which a fluid is flowing; and a light-receiving unit that receives scattered light from the measurement target and outputs a light-receiving signal corresponding to the intensity of the scattered light, A disturbance generation step generates a disturbance signal that causes the drive current supplied to the light-emitting section to fluctuate, Includes an adjustment step of adjusting the drive current based on the signal generated based on the light reception signal and the disturbance signal, The adjustment step further includes an amplitude modification step that changes the amplitude of the disturbance signal. A method for measuring light characterized by the following features.

12. An optical measurement method in an optical measurement device comprising: a light-emitting unit that irradiates light onto a measurement target through which a fluid is flowing; and a light-receiving unit that receives scattered light from the measurement target and outputs a light-receiving signal corresponding to the intensity of the scattered light, A disturbance generation step generates a disturbance signal that causes the drive current supplied to the light-emitting section to fluctuate, Includes an adjustment step of adjusting the drive current based on the signal generated based on the light reception signal and the disturbance signal, The adjustment process described above is: An amplitude changing step to change the amplitude of the disturbance signal, A light intensity determination step is to determine whether the light power of the light emitted by the light-emitting unit is within a specified light intensity range, If the optical power exceeds the specified amount of light, an upper limit limit step is performed to limit the upper limit of the drive current, If the light power falls below the specified light quantity, a lower limit limit step is performed to limit the lower limit amount of the drive current. A method for measuring light, further comprising:

13. A computer in an optical measuring device comprising: a light-emitting unit that irradiates light onto a fluid-flowing object to be measured; and a light-receiving unit that receives scattered light from the object to be measured and outputs a light-receiving signal corresponding to the intensity of the scattered light, A disturbance generation unit generates a disturbance signal that causes the drive current supplied to the light-emitting unit to fluctuate, This adjustment unit functions as an adjustment unit that adjusts the drive current based on the signal generated based on the received light signal and the disturbance signal. The adjustment unit is further configured to function as an amplitude changing unit that changes the amplitude of the disturbance signal. A computer program characterized by the following features.

14. A computer in an optical measuring device comprising: a light-emitting unit that irradiates light onto a fluid-flowing object to be measured; and a light-receiving unit that receives scattered light from the object to be measured and outputs a light-receiving signal corresponding to the intensity of the scattered light, A disturbance generation unit generates a disturbance signal that causes the drive current supplied to the light-emitting unit to fluctuate, This adjustment unit functions as an adjustment unit that adjusts the drive current based on the signal generated based on the received light signal and the disturbance signal. In the adjustment unit, An amplitude changing unit that changes the amplitude of the disturbance signal, A light intensity determination unit that determines whether the light power of the light emitted by the light-emitting unit is within a specified light intensity range, When the optical power exceeds the specified amount of light, an upper limit limiting unit limits the upper limit of the drive current, When the light power falls below the specified light intensity, a lower limit limit unit limits the lower limit amount of the drive current, A computer program characterized by further enhancing its functionality.

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