Optical measuring device and optical measuring method

Abstract

To reduce the measurement time of the side mode suppression ratio.SOLUTION: An optical measurement device 10 according to the present disclosure comprises: a spectrometer 11 for splitting measurement object light; an operational amplifier 13; a photodiode 12; multiple feedback resistors Rf and a switch 14 which are connected in series between the inversion input terminal of the operational amplifier 13 and the output terminal of the operational amplifier 13; and a control unit 20 which switches which of the feedback resistors Rf is connected to the output terminal by controlling the switch 14 according to the light intensity. The control unit 20 reduces the number of feedback resistors Rf switched according to the light intensity in the side mode suppression ratio measurement mode compared to the normal measurement mode.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical measurement device and an optical measurement method.

Background Art

[0002] Conventionally, there are optical measurement devices such as an optical spectrum analyzer that can measure the optical spectrum of the light to be measured. FIG. 8 shows an example of the optical spectrum measured by the optical spectrum analyzer. As shown in FIG. 8, the optical spectrum analyzer can measure an optical spectrum with the wavelength on the horizontal axis and the light intensity on the vertical axis.

[0003] Many optical spectrum analyzers have a configuration including a linear amplifier. The linear amplifier uses a feedback resistor for feedback and can measure the light intensity within a wide measurement range by switching the magnitude of the resistance value of the feedback resistor. For example, Patent Document 1 discloses a linear amplifier (photodetector) configured to switch a plurality of feedback resistors having different resistance values.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The linear amplifier uses a high-resistance feedback resistor when the light intensity is low and a low-resistance feedback resistor when the light intensity is high. For example, when n feedback resistors Rf1 to Rfn can be switched and used, the linear amplifier selects any one of the n feedback resistors Rf1 to Rfn according to the magnitude of the detected light intensity and measures the light intensity using the selected feedback resistor.

[0006] When an optical measuring device measures an optical spectrum, the light intensity fluctuates depending on the wavelength as the wavelength of the light being measured is swept. The optical measuring device switches the feedback resistor of the linear amplifier according to the magnitude of the light intensity.

[0007] Switching the feedback resistor results in a switching time, which is a waiting period. During this switching time, the optical measuring device cannot measure light intensity. The switching time includes the time required to switch the feedback resistor and the time required for the system to stabilize after the switch.

[0008] When measuring an optical spectrum, large fluctuations in light intensity trigger the switching of the feedback resistor multiple times. This results in multiple switching cycles of the feedback resistor, thus prolonging the measurement time.

[0009] Figure 9 shows a conceptual diagram of the measurement time when the feedback resistor is switched from Rf1 to Rfn. When the feedback resistor is switched from Rf1 to Rfn in response to fluctuations in light intensity, a switching time occurs n-1 times. As a result, there is a period of time when measurement is not possible equal to the n-1 switching times, which increases the measurement time.

[0010] Many optical measurement devices, such as optical spectrum analyzers, have the capability to measure the side mode suppression ratio (SMSR), which is the difference between the light intensity of the peaks in the optical spectrum and the light intensity of the side peaks.

[0011] It is desirable to reduce the measurement time for the side-mode suppression ratio.

[0012] Therefore, the object of this disclosure is to provide an optical measuring device and an optical measuring method that can reduce the measurement time of the side mode suppression ratio. [Means for solving the problem]

[0013] Some embodiments of the optical measuring apparatus include a spectrometer for spectrally analyzing the light to be measured, an operational amplifier, a photodiode connected to the inverting input terminal of the operational amplifier and outputting a current corresponding to the light intensity of the light received from the spectrometer, a plurality of feedback resistors and switches connected in series between the inverting input terminal and the output terminal of the operational amplifier, and a control unit that switches which of the plurality of feedback resistors is connected to the output terminal by controlling the switches according to the light intensity, wherein the control unit reduces the number of feedback resistors switched according to the light intensity when in side-mode suppression ratio measurement mode compared to normal measurement mode. With such an optical measuring apparatus, it is possible to reduce the measurement time of the side-mode suppression ratio.

[0014] In one embodiment of the optical measuring device, the control unit may, when in the side-mode suppression ratio measurement mode, switch between two feedback resistors according to the light intensity. This reduces the number of feedback resistors to be switched between according to the light intensity to two, thereby reducing the measurement time for the side-mode suppression ratio.

[0015] In one embodiment of the optical measuring device, the control unit may set the number of feedback resistors to be switched according to the light intensity to three when the side-mode suppression ratio measurement mode is selected. This reduces the number of feedback resistors to be switched according to the light intensity to three, thereby reducing the measurement time for the side-mode suppression ratio.

[0016] In one embodiment of the optical measuring device, the device further includes an input unit capable of receiving user input, and the control unit may transition to the side-mode suppression ratio measurement mode when the input unit receives an input to start the side-mode suppression ratio measurement mode. This allows the device to transition to the side-mode suppression ratio measurement mode in response to user input.

[0017] In an optical measuring device according to one embodiment, the control unit can execute a feedback resistor setting mode. In the feedback resistor setting mode, the number of feedback resistors to be switched according to the light intensity is the same as in the normal measurement mode, and the side mode suppression ratio is measured. Based on the measured side mode suppression ratio, the control unit may decide which of the plurality of feedback resistors to use in the side mode suppression ratio measurement mode. This makes it possible to measure the side mode suppression ratio using the optimal feedback resistor.

[0018] In an optical measuring device according to one embodiment, if the control unit transitions to the side-mode suppression ratio measurement mode after executing the feedback resistance setting mode, it may execute the side-mode suppression ratio measurement mode using the feedback resistance determined in the feedback resistance setting mode. This allows the side-mode suppression ratio to be measured using the determined feedback resistance after the optimal feedback resistance has been set.

[0019] In one embodiment of the optical measuring device, a display unit may be further provided, and the control unit may cause the display unit to display a message indicating that there is a region where the measurement accuracy of the light intensity decreases when transitioning to the side-mode suppression ratio measurement mode. This allows the user to understand that there is a region where the measurement accuracy of the light intensity decreases when measuring in the side-mode suppression ratio measurement mode.

[0020] The optical measurement method according to some embodiments includes a spectrometer that spectrally analyzes the measured light, an operational amplifier, a photodiode connected to the inverting input terminal of the operational amplifier and outputting a current corresponding to the light intensity of the light received from the spectrometer, and a plurality of feedback resistors and switches connected in series between the inverting input terminal and the output terminal of the operational amplifier. The optical measurement method in the optical measurement device includes a feedback resistor switching step of switching which of the plurality of feedback resistors is connected to the output terminal by controlling the switch according to the light intensity. The feedback resistor switching step is performed by reducing the number of feedback resistors to be switched according to the light intensity in the side mode suppression ratio measurement mode compared to the normal measurement mode. According to such an optical measurement method, it is possible to reduce the measurement time of the side mode suppression ratio.

Advantages of the Invention

[0021] According to the present disclosure, it is possible to provide an optical measurement device and an optical measurement method capable of reducing the measurement time of the side mode suppression ratio.

Brief Description of the Drawings

[0022] [Figure 1] It is a diagram showing a schematic configuration of an optical measurement device according to an embodiment. [Figure 2] It is a diagram for explaining the side mode suppression ratio. [Figure 3] It is a diagram showing an example of the resistance values of a plurality of feedback resistors. [Figure 4] It is a diagram showing an example of the switching of the feedback resistor in the normal measurement mode. [Figure 5] It is a diagram showing an example when the number of feedback resistors to be switched in the side mode suppression ratio measurement mode is two. [Figure 6] It is a diagram showing an example of the switching of the feedback resistor in the side mode suppression ratio measurement mode. [Figure 7A] It is a conceptual diagram showing an example of the measurement time in the normal measurement mode. [Figure 7B]This is a conceptual diagram showing an example of measurement time in the side-mode suppression ratio measurement mode. [Figure 8] This figure shows an example of an optical spectrum measured by a conventional optical measuring device. [Figure 9] This is a conceptual diagram illustrating an example of measurement time in conventional optical spectrum measurement. [Modes for carrying out the invention]

[0023] Hereinafter, one embodiment of this disclosure will be described with reference to the drawings.

[0024] Figure 1 shows a schematic configuration of an optical measuring device 10 according to one embodiment. The optical measuring device 10 is a device that has the function of measuring the optical spectrum of light to be measured.

[0025] The light measuring device 10 comprises a spectrometer 11, a photodiode 12, an operational amplifier 13, a plurality of feedback resistors Rf1 to Rfn, a switch 14, an AD converter 15, a DA converter 16, resistors Ra1 and Ra2, an input unit 17, a display unit 18, a storage unit 19, and a control unit 20.

[0026] The spectrometer 11 spectrally separates the light to be measured. The spectrometer 11 may be any spectrometer capable of spectrally separating light. For example, the spectrometer 11 may be a monochromator using a diffraction grating.

[0027] The spectrometer 11 extracts light of a specific wavelength from the light to be measured and outputs it to the photodiode 12. By sweeping the wavelength of the light output by the spectrometer 11 to the photodiode 12 and measuring the light intensity at each wavelength, the light measuring device 10 can measure the light spectrum.

[0028] The photodiode 12 is connected to the inverting input terminal of the operational amplifier 13. When the photodiode 12 receives light output from the spectrometer 11, it outputs a current Ip corresponding to the light intensity of the light received from the spectrometer 11. The relationship between the light intensity of the light received by the photodiode 12 and the current output by the photodiode 12 is determined by the photosensitivity of the photodiode 12.

[0029] The operational amplifier 13 may be any operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal.

[0030] Multiple feedback resistors Rf1 to Rfn are connected in parallel between the inverting input terminal of the operational amplifier 13 and the switch 14. In Figure 1, n feedback resistors Rf1 to Rfn are shown, but the number of feedback resistors Rf1 to Rfn can be any number of 3 or more. Note that when there is no need to distinguish between feedback resistors Rf1 to Rfn, they may simply be referred to as "feedback resistor Rf" in the explanation.

[0031] Multiple feedback resistors Rf1 to Rfn each have different resistance values. In this embodiment, Rf1 has the largest resistance value, and the resistance values ​​decrease as the numbers Rf2, Rf3, and so on increase. Rfn has the smallest resistance value.

[0032] Multiple feedback resistors Rf1 to Rfn may each have feedback capacitors Cf1 to Cfn connected in parallel. In this embodiment, the feedback capacitors Cf1 to Cfn will be omitted from the explanation.

[0033] Switch 14 is connected between the multiple feedback resistors Rf1 to Rfn and the output terminal of the operational amplifier 13. In other words, the multiple feedback resistors Rf1 to Rfn and switch 14 are connected in series between the inverting input terminal of the operational amplifier 13 and the output terminal of the operational amplifier 13.

[0034] Switch 14 switches which of the multiple feedback resistors Rf1 to Rfn is connected to the output terminal of the operational amplifier 13, in accordance with a command from the control unit 20. Switch 14 connects one of the multiple feedback resistors Rf1 to Rfn to the output terminal of the operational amplifier 13.

[0035] The switch 14 may be a switch of any configuration that can turn on / off the electrical connection between each of the multiple feedback resistors Rf1 to Rfn and the output terminal of the operational amplifier 13.

[0036] When switch 14 selects feedback resistor Rfi from among multiple feedback resistors Rf1 to Rfn, the voltage at the output terminal of operational amplifier 13, i.e., the output voltage Vo of operational amplifier 13, is expressed by the following formula. Vo = -Rfi × Ip

[0037] The AD converter 15 converts the output voltage Vo of the operational amplifier 13 from an analog value to a digital value. The AD converter 15 outputs the output voltage Vo, which has been converted to a digital value, to the control unit 20. The AD converter 15 may be an AD converter with any configuration.

[0038] The DA converter 16 converts the digital voltage set by the control unit 20 into an analog voltage and outputs it. The DA converter 16 may be any configuration of DA converter.

[0039] Resistors Ra1 and Ra2 are used to divide the voltage output by the DA converter 16. The node connecting resistors Ra1 and Ra2 is connected to the non-inverting input terminal of the operational amplifier 13. The voltage output by the DA converter 16 is divided by resistors Ra1 and Ra2 and input to the non-inverting input terminal of the operational amplifier 13.

[0040] The DA converter 16, resistors Ra1 and Ra2 form a circuit for canceling the offset voltage of the operational amplifier 13. The offset voltage of the operational amplifier 13 is typically around a few millivolts. To cancel this offset voltage, resistor Ra1 typically has a resistance of a few ohms, and resistor Ra2 has a resistance value that is significantly larger than resistor Ra1.

[0041] The input unit 17 includes an interface that can accept operations from the user. The input unit 17 may include, for example, buttons, rotary knobs, etc.

[0042] The display unit 18 can display various types of data. For example, the display unit 18 can display the light spectrum measured by the light measuring device 10. The display unit 18 may include, for example, an LCD (Liquid Crystal Display) or an organic EL (Electro-Luminescent) display.

[0043] The storage unit 19 is, for example, a semiconductor memory, magnetic memory, or optical memory, but is not limited to these. The storage unit 19 may function as, for example, a main memory, an auxiliary memory, or a cache memory. The storage unit 19 stores any information used in the operation of the optical measuring device 10. For example, the storage unit 19 may store a system program, an application program, various data, etc.

[0044] The control unit 20 includes at least one processor, at least one dedicated circuit, or a combination thereof. The processor is a general-purpose processor such as a CPU (Central Processing Unit) or GPU (Graphics Processing Unit), or a dedicated processor specialized for a specific process. The dedicated circuit is, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0045] The control unit 20 reads programs, data, etc., stored in the memory unit 19 and executes various functions.

[0046] Next, we will explain the operation of the light measuring device 10.

[0047] The optical measuring device 10 sweeps the wavelength of the light output by the spectrometer 11 to the photodiode 12 while the light to be measured is input to the spectrometer 11. At this time, by measuring the light intensity of each wavelength, an optical spectrum as shown in Figure 8 can be measured.

[0048] The optical measuring device 10 can measure the side mode suppression ratio by measuring the optical spectrum. In this embodiment, the "side mode suppression ratio" may also be referred to as "SMSR (Side Mode Suppression Ratio)".

[0049] The side-mode suppression ratio will be explained with reference to Figure 2.

[0050] In the optical spectrum shown in Figure 2, peak 101 is the peak with the highest light intensity. Side peak 102 is the second largest peak at wavelengths smaller than peak 101. Side peak 103 is the second largest peak at wavelengths larger than peak 101.

[0051] The side-mode suppression ratio is represented by reference numerals 104 and 105 in Figure 2. Reference numeral 104 is the difference between the light intensity of peak 101 and the light intensity of side peak 102. Reference numeral 104 may also be referred to as the side-mode suppression ratio of side peak 102. Reference numeral 105 is the difference between the light intensity of peak 101 and the light intensity of side peak 103. Reference numeral 105 may also be referred to as the side-mode suppression ratio of side peak 103. The side-mode suppression ratio is usually expressed in units of [dB].

[0052] Referring again to Figure 1, the switching of feedback resistors Rf1 to Rfn will be explained. The control unit 20 controls the switch 14 according to the light intensity obtained from the AD converter 15, and switches which of the multiple feedback resistors Rf1 to Rfn, Rf, is connected to the output terminal of the operational amplifier 13.

[0053] The following relationship generally exists between the magnitude of the feedback resistor Rf and various characteristics: • A higher resistance value for the feedback resistor Rf results in a lower noise level, while a lower resistance value results in a higher noise level. • A larger resistance value for the feedback resistor Rf results in a larger output voltage Vo, while a smaller resistance value results in a smaller output voltage Vo. • A higher resistance value for the feedback resistor Rf results in a narrower bandwidth, while a lower resistance value results in a wider bandwidth.

[0054] Due to these characteristics, the control unit 20 controls the switch 14 so that a feedback resistor Rf with a high resistance value is selected when the light intensity is low, and so that a feedback resistor Rf with a low resistance value is selected when the light intensity is high. Here, the expression "selecting a feedback resistor Rf" means that the switch 14 is controlled so that the selected feedback resistor Rf is connected to the output terminal of the operational amplifier 13.

[0055] Figure 3 shows an example of the resistance values ​​of feedback resistors Rf1 to Rf8 when there are 8 feedback resistors Rf1 to Rfn, i.e., n=8.

[0056] In the example shown in Figure 3, the resistance value of feedback resistor Rf1 is 1 GΩ. The resistance value of feedback resistor Rf2 is 100 MΩ, which is an order of magnitude smaller than the resistance value of feedback resistor Rf1. In this way, the resistance values ​​become progressively smaller by an order of magnitude, and the resistance value of feedback resistor Rf8 is 100 Ω.

[0057] Figure 3 also shows the noise level when each feedback resistor Rf is selected. In the example shown in Figure 3, the noise level when feedback resistor Rf1 is selected is -90 dBm, which is the lowest noise level. The noise level when feedback resistor Rf8 is selected is -20 dBm, which is the highest noise level.

[0058] Hereafter, we will explain using the case where the optical measuring device 10 is equipped with multiple feedback resistors Rf1 to Rf8 as shown in Figure 3 as an example.

[0059] The optical measuring device 10 has a normal measurement mode and a side-mode suppression ratio measurement mode. The side-mode suppression ratio measurement mode is a mode that enables high-speed measurement of the side-mode suppression ratio. The optical measuring device 10 can measure the side-mode suppression ratio using either the normal measurement mode or the side-mode suppression ratio measurement mode.

[0060] <Normal measurement mode> First, the operation of the optical measuring device 10 when measuring the side-mode suppression ratio in normal measurement mode will be explained with reference to Figure 4.

[0061] In normal measurement mode, the control unit 20 controls the switch 14 to select one feedback resistor Rf from among the eight feedback resistors Rf1 to Rf8 according to the light intensity.

[0062] In the example shown in Figure 4, the control unit 20 selects feedback resistors Rf1 to Rf8 according to the light intensity as follows. If light intensity is less than P1: Select feedback resistor Rf1. If light intensity is above P1 and below P2: Select feedback resistor Rf2. Light intensity is above P2 and below P3: Select feedback resistor Rf3. Light intensity is P3 or higher but less than P4: Select feedback resistor Rf4. Light intensity between P4 and P5: Select feedback resistor Rf5. Light intensity is P5 or higher but less than P6: Select feedback resistor Rf6. If the light intensity is P6 or higher but less than P7: Select feedback resistor Rf7. Light intensity P7 or higher: Select feedback resistor Rf8

[0063] When measuring the optical spectrum with this setup, as the wavelength of the light output by the spectrometer 11 to the photodiode 12 is swept from smaller wavelengths to larger wavelengths, a switchover of the feedback resistor Rf occurs at the wavelengths indicated by the white circles in Figure 4.

[0064] For example, referring to the side peak 102, just before the wavelength approaches the wavelength of side peak 102, the control unit 20 switches the feedback resistor Rf from feedback resistor Rf2 to feedback resistor Rf3. Also, immediately after the wavelength passes the wavelength of side peak 102, the control unit 20 switches the feedback resistor Rf from feedback resistor Rf3 to feedback resistor Rf2.

[0065] In the example shown in Figure 4, the control unit 20 performs the operation of switching the feedback resistor Rf 14 times when measuring the optical spectrum. Since a waiting time occurs when switching the feedback resistor Rf, the more times the feedback resistor Rf is switched, the longer the time required to measure the optical spectrum becomes.

[0066] The control unit 20 can calculate the side-mode suppression ratio by measuring the optical spectrum and calculating the difference between the light intensity of peak 101 and the light intensity of side peak 102, and the difference between the light intensity of peak 101 and the light intensity of side peak 103.

[0067] <Side-mode suppression ratio measurement mode> Next, we will explain the operation of the optical measuring device 10 when it measures the side-mode suppression ratio in side-mode suppression ratio measurement mode.

[0068] The input unit 17 can receive an operation from the user to start the side mode suppression ratio measurement mode.

[0069] When the input unit 17 receives an operation from the user to start the side-mode suppression ratio measurement mode, the control unit 20 switches to the side-mode suppression ratio measurement mode.

[0070] When the control unit 20 switches to the side-mode suppression ratio measurement mode, it reduces the number of feedback resistors Rf that are switched according to the light intensity compared to the normal measurement mode.

[0071] Figure 5 shows an example of a side-mode suppression ratio measurement mode where the number of feedback resistors Rf that are switched according to the light intensity is set to two.

[0072] In the example shown in Figure 5, the control unit 20 uses only the feedback resistors Rf3 and Rf7 in the side-mode suppression ratio measurement mode. That is, the control unit 20 switches only the two feedback resistors Rf depending on the light intensity.

[0073] In side-mode suppression ratio measurement mode, the choice of which of the multiple feedback resistors Rf1 to Rf8 to use is predetermined and stored in the memory unit 19.

[0074] The operation of the optical measuring device 10 when measuring the side-mode suppression ratio in side-mode suppression ratio measurement mode will be explained with reference to Figure 6.

[0075] In the example shown in Figure 6, the control unit 20 selects either the feedback resistor Rf3 or Rf7 according to the light intensity, as follows. Light intensity less than P4: Select feedback resistor Rf3 Light intensity P4 or higher: Select feedback resistor Rf7

[0076] When measuring the optical spectrum with this setup, as the wavelength of the light output by the spectrometer 11 to the photodiode 12 is swept from smaller wavelengths to larger wavelengths, a switchover of the feedback resistor Rf occurs at the wavelengths indicated by the white circles in Figure 6.

[0077] For example, referring to the side peak 102, when measuring in normal measurement mode, the feedback resistance Rf is switched at the wavelengths before and after the side peak 102, as shown in Figure 4. However, when measuring in side-mode suppression ratio measurement mode, the feedback resistance Rf is not switched at the wavelengths before and after the side peak 102.

[0078] In the example shown in Figure 6, the control unit 20 performs the operation of switching the feedback resistor Rf only twice when measuring the optical spectrum. In this way, the operation of switching the feedback resistor Rf is reduced compared to the normal measurement mode, so the optical measuring device 10 can reduce the measurement time of the side mode suppression ratio by measuring in side mode suppression ratio measurement mode.

[0079] The control unit 20 can calculate the side-mode suppression ratio by measuring the optical spectrum and calculating the difference between the light intensity of peak 101 and the light intensity of side peak 102, and the difference between the light intensity of peak 101 and the light intensity of side peak 103.

[0080] The fact that measurement time can be reduced when measuring in side-mode suppression ratio measurement mode compared to measurement in normal measurement mode will be further explained with reference to Figures 7A and 7B.

[0081] Figure 7A schematically shows the time taken to measure from wavelength f1 to wavelength f2 in the measurement shown in Figure 4.

[0082] As shown in Figures 4 and 7A, the switching of the feedback resistor Rf occurs seven times during the measurement from wavelength f1 to wavelength f2. Since the switching of the feedback resistor Rf occurs seven times, the time taken to measure from wavelength f1 to wavelength f2 is only t1, as shown in Figure 7A.

[0083] Figure 7B schematically shows the time taken to measure from wavelength f1 to wavelength f2 in the measurement shown in Figure 6.

[0084] As shown in Figures 6 and 7B, the switching of the feedback resistor Rf occurs only once during the measurement from wavelength f1 to wavelength f2. Because the switching of the feedback resistor Rf occurs only once, the time t2 for measuring from wavelength f1 to wavelength f2 is shorter than the time t1 shown in Figure 7A.

[0085] This section explains why the number of feedback resistors Rf that need to be switched according to light intensity can be reduced when measuring in side-mode suppression ratio mode compared to normal measurement mode.

[0086] Referring to Figure 4, selecting feedback resistor Rf7 is optimal for measuring peak 101. Similarly, selecting feedback resistor Rf3 is optimal for measuring side peaks 102 and 103.

[0087] Typically, when measuring the side-mode suppression ratio, the approximate levels of the light intensities of peak 101, side peak 102, and side peak 103 are often known. Therefore, even if only the feedback resistor Rf, which can accurately measure peak 101, side peak 102, and side peak 103, is used, peak 101, side peak 102, and side peak 103 can be measured accurately, and thus the side-mode suppression ratio can be measured accurately.

[0088] For example, in the example shown in Figure 4, the side-mode suppression ratio can be measured with the same measurement accuracy as when measuring in normal measurement mode, even if only feedback resistors Rf3 and Rf7 are used.

[0089] When measuring in side-mode suppression ratio measurement mode, for example, in the region where measurement with feedback resistor Rf4 or feedback resistor Rf5 is optimal in normal measurement mode, the measurement accuracy of light intensity may decrease slightly. To notify the user of this, the control unit 20 may display a message on the display unit 18 indicating that there is a region where the measurement accuracy of light intensity decreases when switching to side-mode suppression ratio measurement mode. However, even in this case, since there are no side peaks 102 and 103 in the region measured with feedback resistor Rf4 or feedback resistor Rf5, the measurement accuracy of the side-mode suppression ratio does not decrease.

[0090] <Feedback Resistance Setting Mode> In the above explanation, it was assumed that when measuring in side-mode suppression ratio measurement mode, the choice of which of the multiple feedback resistors Rf1 to Rf8 to use Rf was predetermined.

[0091] The control unit 20 may execute the feedback resistance setting mode and, when measuring in the side mode suppression ratio measurement mode, automatically determine which of the multiple feedback resistors Rf1 to Rf8 to use.

[0092] In the feedback resistance setting mode, the control unit 20 measures the side mode suppression ratio by switching the same number of feedback resistors Rf according to the light intensity as in the normal measurement mode. That is, if the number of feedback resistors Rf to be switched in the normal mode is 8 (feedback resistors Rf1 to Rf8), the control unit 20 measures the side mode suppression ratio by switching the 8 feedback resistors Rf1 to Rf8 according to the light intensity.

[0093] The control unit 20 may measure the side-mode suppression ratio using the same number of switching feedback resistors Rf as in the normal measurement mode, and then, based on the measured side-mode suppression ratio, determine which of the multiple feedback resistors Rf1 to Rf8 to use in the side-mode suppression ratio measurement mode.

[0094] The control unit 20 may, for example, determine which of the multiple feedback resistors Rf1 to Rf8 to use in side-mode suppression ratio measurement mode based on the light intensities of peak 101, side peak 102, and side peak 103 measured when measuring the side-mode suppression ratio.

[0095] The control unit 20 can select the optimal feedback resistor Rf for measuring the side mode suppression ratio by executing a feedback resistor setting mode and automatically determining which of the multiple feedback resistors Rf1 to Rf8 to use when the side mode suppression ratio measurement mode is activated.

[0096] If the control unit 20 transitions to the side-mode suppression ratio measurement mode after executing the feedback resistance setting mode, it executes the side-mode suppression ratio measurement mode using the feedback resistance Rf determined in the feedback resistance setting mode.

[0097] The control unit 20 does not execute the feedback resistance setting mode every time, but may switch to the feedback resistance setting mode only when it determines, based on the results of measurements in the side mode suppression ratio measurement mode, that it is necessary to execute the feedback resistance setting mode. For example, the control unit 20 may switch to the feedback resistance setting mode when it determines, based on the results of measurements in the side mode suppression ratio measurement mode, that the light intensity of side peaks 102 and 103 is an intensity that cannot be accurately measured with a preset feedback resistance Rf.

[0098] According to the optical measuring device 10 of the above embodiment, it is possible to reduce the measurement time for the side mode suppression ratio. More specifically, the control unit 20 reduces the number of feedback resistors Rf that are switched according to the light intensity when in side mode suppression ratio measurement mode compared to normal measurement mode. This reduces the number of times switching time occurs to switch the feedback resistors Rf when measuring the optical spectrum to measure the side mode suppression ratio. In this way, the number of times switching time occurs can be reduced, so the optical measuring device 10 can reduce the measurement time for the side mode suppression ratio.

[0099] It will be apparent to those skilled in the art that this disclosure can be implemented in other predetermined forms besides the embodiments described above without deviating from its spirit or essential features. Therefore, the prior description is illustrative and not limiting. The scope of the disclosure is defined not by the prior description but by the added claims. Any modifications within their equivalent scope are incorporated therein.

[0100] For example, the arrangement and number of each component described above are not limited to those shown in the above description and drawings. The arrangement and number of each component may be configured arbitrarily, as long as it can achieve its function.

[0101] For example, in the embodiment described above, we explained the case where the number of feedback resistors Rf switched according to the light intensity in the side-mode suppression ratio measurement mode is two, but the number of feedback resistors Rf switched may also be three. Furthermore, the number of feedback resistors Rf switched is not limited to two or three, but can be any number less than the number of feedback resistors Rf switched in the normal measurement mode. [Explanation of Symbols]

[0102] 10. Optical measuring device 11 Spectrometer 12 Photodiodes 13. Operational Amplifier 14 switches 15 AD converters 16 DA converters 17 Input section 18 Display 19 Memory section 20 Control Unit Rf1~Rfn, Rf feedback resistor Ra1 resistor Ra2 resistance

Claims

1. A spectrometer that spectrally analyzes the light to be measured, Operational amplifier and A photodiode connected to the inverting input terminal of the operational amplifier outputs a current corresponding to the light intensity of the light received from the spectrometer, A plurality of feedback resistors and switches are connected in series between the inverting input terminal and the output terminal of the operational amplifier, A control unit that switches which of the plurality of feedback resistors is connected to the output terminal by controlling the switch according to the light intensity, Equipped with, The control unit reduces the number of feedback resistors that are switched according to the light intensity when in side-mode suppression ratio measurement mode compared to when in normal measurement mode, in an optical measuring device.

2. In the optical measuring device according to claim 1, The control unit, in the side-mode suppression ratio measurement mode, sets the number of feedback resistors to be switched to two according to the light intensity, in an optical measuring device.

3. In the optical measuring device according to claim 1, The control unit, in the side-mode suppression ratio measurement mode, sets the number of feedback resistors to be switched to three according to the light intensity, in an optical measuring device.

4. In the optical measuring device according to claim 1, It also includes an input section that can accept user input, The optical measuring device, wherein the control unit switches to the side-mode suppression ratio measurement mode when the input unit receives an operation to start the side-mode suppression ratio measurement mode.

5. In the optical measuring device according to claim 1, The control unit, The feedback resistance setting mode is available. In the feedback resistance setting mode, the number of feedback resistors to be switched according to the light intensity is the same as in the normal measurement mode, and the side mode suppression ratio is measured. An optical measuring device that determines, based on the measured side-mode suppression ratio, which of the plurality of feedback resistors to use when in the side-mode suppression ratio measurement mode.

6. In the optical measuring device according to claim 5, The control unit, when transitioning to the side-mode suppression ratio measurement mode after executing the feedback resistance setting mode, executes the side-mode suppression ratio measurement mode using the feedback resistance determined in the feedback resistance setting mode, in an optical measuring device.

7. In the optical measuring device according to claim 1, It also includes a display unit, The optical measuring device includes a control unit that causes the display unit to display a message indicating that there is a region where the measurement accuracy of the light intensity decreases when transitioning to the side-mode suppression ratio measurement mode.

8. A method for measuring light in an optical measuring apparatus comprising: a spectrometer for spectrally analyzing light to be measured; an operational amplifier; a photodiode connected to the inverting input terminal of the operational amplifier and outputting a current corresponding to the light intensity of the light received from the spectrometer; and a plurality of feedback resistors and switches connected in series between the inverting input terminal and the output terminal of the operational amplifier, wherein The process includes a feedback resistor switching step in which the feedback resistor to connect to the output terminal is switched by controlling the switch according to the light intensity, among the plurality of feedback resistors. The optical measurement method is characterized in that the feedback resistor switching step is performed by reducing the number of feedback resistors to be switched according to the light intensity when in side-mode suppression ratio measurement mode compared to when in normal measurement mode.

9. In the optical measurement method described in claim 8, The aforementioned feedback resistor switching step is performed in the side-mode suppression ratio measurement mode by switching the number of feedback resistors to two according to the light intensity, in an optical measurement method.

10. In the optical measurement method described in claim 8, The aforementioned feedback resistor switching step is performed in the side-mode suppression ratio measurement mode by switching the number of feedback resistors to three according to the light intensity, in an optical measurement method.

11. In the optical measurement method described in claim 8, A method for measuring optical effects, further comprising the step of transitioning to the side-mode suppression ratio measurement mode upon receiving an operation to initiate the side-mode suppression ratio measurement mode.

12. In the optical measurement method described in claim 8, The aforementioned optical measurement method is capable of executing a feedback resistance setting mode. The aforementioned feedback resistor setting mode is, The steps include: measuring the side-mode suppression ratio by setting the number of feedback resistors that are switched according to the light intensity to the same number as in the normal measurement mode; A method for measuring optical effects, comprising the step of determining, based on the measured side-mode suppression ratio, which of the plurality of feedback resistors to use in the side-mode suppression ratio measurement mode.

13. In the optical measurement method according to claim 12, The optical measurement method is an optical measurement method in which, after performing the feedback resistance setting mode, the side mode suppression ratio measurement mode is performed using the feedback resistance determined in the feedback resistance setting mode.

14. In the optical measurement method described in claim 8, A method for measuring light, further comprising the step of displaying a message indicating that there is a region where the measurement accuracy of the light intensity decreases when transitioning to the side-mode suppression ratio measurement mode.

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