Weighing instrument

Abstract

To provide a weighing device that can measure the weight and mass of an object with high precision while being miniaturized. [Solution] A weighing device comprising: a support having a mounting surface on which an object to be measured is placed, wherein the mounting surface is displaced according to the mass of the object to be measured; a mirror disposed on the support; a laser interferometer that uses laser light to detect changes in the optical path length to the mirror due to the displacement of the mounting surface; and a control unit that calculates the weight or mass of the object to be measured based on the detected change in the optical path length, wherein the laser interferometer comprises a laser light source that emits the laser light and a vibrator-type optical modulator that has a vibrating element and modulates the frequency of the laser light using the vibration of the vibrating element.

Description

Technical Field

[0001] The present invention relates to a weighing instrument.

Background Art

[0002] Patent Document 1 discloses a precision scale including a short-stroke measurement mechanism, a load receiver, a hanger for connecting the load receiver to the measurement mechanism, a leaf spring as a receiving means, and a fixing means for connecting the central portion of the leaf spring to the bottom of the hanger. In such a precision scale, since it is possible to protect the precision scale against a load applied from an unintended direction, the weighing of the object to be measured can be performed accurately.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the precision scale described in Patent Document 1, while miniaturization is facilitated by using a short-stroke measurement mechanism, there is a problem that the measurement accuracy cannot be sufficiently improved. Therefore, there is a demand for realizing a weighing instrument that can measure the weight and mass of the object to be measured with high accuracy while achieving miniaturization.

Means for Solving the Problems

[0005] The weighing instrument according to an application example of the present invention has a placement surface on which the object to be measured is placed, and a support portion on which the placement surface is displaced according to the mass of the object to be measured, a mirror disposed on the support portion, a laser interferometer that uses a laser beam to detect a change in the optical path length to the mirror accompanying the displacement of the placement surface, A control unit that calculates the weight or mass of the object to be measured based on the detected change in optical path length, Equipped with, The aforementioned laser interferometer is A laser light source that emits the aforementioned laser light, A vibrator-type optical modulator having a vibrating element and modulating the frequency of the laser light using the vibration of the vibrating element, It holds. [Brief explanation of the drawing]

[0006] [Figure 1] This is a schematic diagram showing the configuration of a weighing device according to the first embodiment. [Figure 2] This is a schematic diagram showing a modified version of Miller's work. [Figure 3] This is a schematic diagram showing the configuration of a weighing device according to the second embodiment. [Figure 4] This is a schematic diagram showing the configuration of a weighing device according to the third embodiment. [Figure 5] This is a schematic diagram showing a modified example of an optical component. [Figure 6] This is a schematic diagram showing the configuration of a weighing device according to the fourth embodiment. [Figure 7] This is a schematic diagram showing a modified version of Miller's work. [Figure 8] This is a schematic diagram showing the configuration of a weighing device according to the fifth embodiment. [Modes for carrying out the invention]

[0007] The weighing device according to the present invention will be described in detail below based on the embodiments shown in the attached drawings.

[0008] 1. First Embodiment First, the weighing apparatus according to the first embodiment will be described. Figure 1 is a schematic diagram showing the configuration of the weighing device 1 according to the first embodiment. In the figures of this application, the X-axis, Y-axis, and Z-axis are set as three mutually orthogonal axes. Each axis is represented by an arrow, with the tip of the arrow being "positive" and the base of the arrow being "negative". In the following explanation, for example, "X-axis direction" includes both the positive and negative directions of the X-axis. The same applies to the Y-axis and Z-axis directions. The Z-axis is parallel to the vertical axis, and the positive side of the Z-axis is also called "upward", and the negative side of the Z-axis is also called "downward".

[0009] The weighing device 1 shown in Figure 1 comprises a support unit 2, a mirror 3, a laser interferometer 4, and a control unit 5. The support unit 2 has a mounting surface 221 on which the object to be measured 9 is placed, and the mounting surface 221 is displaced according to the mass of the object to be measured 9. The mirror 3 is positioned on the support unit 2. The laser interferometer 4 has a laser light source 42 and an oscillator-type optical modulator 44, and uses laser interference technology with laser light L to detect the change in optical path length S3 to the mirror 3 due to the displacement of the mounting surface 221. The laser light source 42 emits laser light L. The oscillator-type optical modulator 44 has a vibrating element 442, and modulates the frequency of the laser light L using the vibration of the vibrating element 442. The control unit 5 calculates the weight of the object to be measured 9 based on the detected change in optical path length S3.

[0010] The mounting surface 221 is displaced according to the mass of the object to be measured 9. The laser interferometer 4 can detect the displacement of the mounting surface 221 with high precision using laser light L. Therefore, the control unit 5 can accurately calculate the weight of the object to be measured 9. Furthermore, since the laser interferometer 4 has an oscillator-type optical modulator 44, it is easy to miniaturize. Thus, with the above configuration, a weighing device 1 that can measure the weight of the object to be measured 9 with high precision can be realized while achieving miniaturization. The parts of the weighing device 1 will be described in detail below.

[0011] 1.1.Support part The support unit 2 shown in Figure 1 comprises a weighing pan 22 having a mounting surface 221, an elastic body 23, a base 24, and an optical path conversion unit 25. The weighing pan 22 having the placement surface 221 is a tray on which the object to be measured 9 is placed. The bottom surface of the weighing pan 22 shown in FIG. 1 is the placement surface 221 on which the object to be measured 9 is placed. The placement surface 221 is a surface facing upward.

[0012] The elastic body 23 is connected to the back surface 222 located opposite to the placement surface 221 of the weighing pan 22. The elastic body 23 is a member that is disposed between the weighing pan 22 and the base 24 and elastically deform under a load. The elastic body 23 shown in FIG. 1 is, as an example, a coil spring. A load due to the mass of the object to be measured 9 placed on the placement surface 221 is applied to the elastic body 23. As a result, the elastic body 23 elastically deform in the Z-axis direction according to the mass of the object to be measured 9. That is, the elastic body 23 displaces the placement surface 221 by a displacement amount corresponding to the mass of the object to be measured 9. Therefore, the elastic body 23 only needs to be a member having a predetermined correlation with the weight of the object to be measured 9 in terms of its elastic deformation amount.

[0013] According to such a configuration, by simply placing the object to be measured 9 on the placement surface 221 of the weighing pan 22, the weight of the object to be measured 9 can be easily measured. As a result, the weighing instrument 1 that can easily perform the measurement operation can be obtained.

[0014] In addition, by using the elastic deformation of the elastic body 23, the mass of the object to be measured 9 can be converted into the displacement amount of the placement surface 221 without consuming energy. Therefore, the weighing instrument 1 with low power consumption can be obtained. Note that the elastic body 23 is not limited to a coil spring, and for example, in addition to mechanical springs such as metal springs such as leaf springs, rubber springs composed of rubber, elastomers, etc., there are also magnetic springs using the magnetic repulsive force of permanent magnets, electromagnetic springs using the magnetic repulsive force of electromagnets, electrostatic springs using electrostatic force, and the like.

[0015] Note that the placement surface 221 only needs to be a surface on which the object to be measured 9 can be placed, and is not limited to a surface facing upward. For example, when the object to be measured 9 is placed on the support portion 2 by hooking it, the surface such as a hook on which the object to be measured 9 is hooked becomes the placement surface.

[0016] The base 24 is placed on the floor surface, the upper surface of the table, etc., and sandwiches the elastic body 23 with the weighing pan 22. The optical path conversion unit 25 is provided on the optical path of the laser beam L and converts the optical path of the laser beam L. The optical path conversion unit 25 is composed of optical elements such as a reflecting mirror, a lens, an optical fiber, etc. For example, a reflecting mirror is used as the optical path conversion unit 25 shown in FIG. 1. The optical path conversion unit 25 shown in FIG. 1 converts the optical path of the laser beam L incident from the minus side of the X-axis toward the plus side of the X-axis so as to be upward. Also, the optical path of the laser beam L reflected by the mirror 3 and directed downward is converted so as to be toward the minus side of the X-axis. By providing such an optical path conversion unit 25, the degree of freedom in arranging the laser interferometer 4 with respect to the mirror 3 can be increased. As a result, the weighing instrument 1 can be made smaller, thinner, lighter, etc. Note that the optical path conversion unit 25 may be provided as necessary. For example, when the laser interferometer 4 is arranged on the base 24 or when the laser interferometer 4 is arranged below the base 24, it may be omitted. In the latter case, the laser beam L can be introduced above the base 24 through a through hole (not shown) formed in the base 24.

[0017] 1.2 Mirror The mirror 3 shown in FIG. 1 is arranged at the center of the back surface 222 located opposite to the placement surface 221 of the weighing pan 22. When the object to be measured 9 is placed on the placement surface 221, the weighing pan 22 is displaced downward according to the mass of the object to be measured 9. Along with that, the back surface 222 and the mirror 3 arranged on the back surface 222 are also displaced downward by the same displacement amount as the placement surface 221. Therefore, by using the laser interferometer 4 to detect the change S3 in the optical path length from the laser interferometer 4 to the mirror 3, the weight of the object to be measured 9 can be accurately measured.

[0018] The mirror 3 is not particularly limited as long as it is a material that reflects the laser light L. For example, the mirror 3 may be a glass mirror, a metal mirror, or a resin mirror. The mirror 3 shown in Figure 1 has a flat reflective surface. For this reason, the incident angle of the laser light L is set to approximately 90° for the mirror 3 shown in Figure 1. As a result, the reflection angle is also approximately 90°.

[0019] Note that the placement of mirror 3 is not limited to the above-mentioned positions. For example, mirror 3 may be placed on the bottom surface or edge of the weighing pan 22, or it may be connected to the weighing pan 22 via any connecting member (not shown).

[0020] Furthermore, the elastic body 23 shown in Figure 1 is a coil spring and has a cylindrical shape overall. Therefore, when viewed from below, the connection between the elastic body 23 and the back surface 222 forms an annular shape that surrounds the mirror 3 located in the center of the back surface 222. In other words, the elastic body 23 is connected to the annular portion of the back surface 222 that is located outside the mirror 3. With this configuration, when the object to be measured 9 is placed on the mounting surface 221, the posture of the weighing pan 22 is suppressed to change significantly. That is, the elastic body 23 can be elastically deformed while maintaining a good horizontal state of the mounting surface 221. This suppresses the occurrence of measurement errors due to unintended tilting of the mirror 3 and the instability of the object to be measured 9 due to unintended tilting of the mounting surface 221. The annular shape can be a circular annular shape, a square annular shape, etc.

[0021] Figure 2 is a schematic diagram showing a modified version of mirror 3. The weighing instrument 1 shown in Figure 2 is the same as the weighing instrument 1 shown in Figure 1, except that the shape of mirror 3 is different. The mirror 3 shown in Figure 2 is a corner cube mirror. A corner cube mirror is a retroreflective mirror. Retroreflectiveness is the property that light incident on a mirror is reflected back along the incident light path, regardless of the angle of incidence. By using a corner cube mirror as mirror 3, even if the weighing pan 22 tilts and the mirror 3 tilts as a result, much of the incident light on mirror 3 can be returned to the optical path conversion unit 25. This suppresses a decrease in the detection accuracy of the change in optical path length S3 by the laser interferometer 4, even if the weighing pan 22 tilts. In addition, the tolerance for misalignment between mirror 3 and the optical path conversion unit 25 is increased, making it possible to realize a weighing device 1 that is easy to assemble. Furthermore, mirror 3 may be a retroreflective mirror other than a corner cube mirror. Examples of retroreflective mirrors include a corner cube prism with internal reflectivity, a retroreflector sheet, and the like.

[0022] 1.3. Laser Interferometer The laser interferometer 4 shown in Figure 1 uses laser light L to detect the change S3 in optical path length to the mirror 3 due to the displacement of the mounting surface 221. The laser interferometer 4 shown in Figure 1 includes a laser light source 42, an oscillator-type optical modulator 44, a beam splitter 46, a photodetector 47, and a signal processing unit 48. For such a laser interferometer 4 having an oscillator-type optical modulator 44, for example, the laser interferometer disclosed in Japanese Patent Application Publication No. 2022-38156 is preferably used. Because such a laser interferometer 4 has an oscillator-type optical modulator 44, it can be made smaller, lighter, and consume less power.

[0023] Examples of the laser light source 42 include the laser light source disclosed in Japanese Patent Publication No. 2022-38156. By using a semiconductor laser such as a VCSEL (Vertical Cavity Surface Emitting Laser), further miniaturization of the laser interferometer 4 can be achieved.

[0024] The oscillator-type optical modulator 44 applies a modulation signal to the laser light L using a vibrating element 442. An example of the oscillator-type optical modulator 44 is the optical modulator disclosed in Japanese Patent Application Publication No. 2022-38156. The oscillator-type optical modulator 44 has a vibrating element 442. Examples of the vibrating element 442 include a quartz crystal oscillator, a silicon crystal oscillator, a ceramic crystal oscillator, etc. The quartz crystal oscillator may be an AT crystal oscillator, a tuning fork crystal oscillator, or any other type of oscillator. Since these oscillators utilize the mechanical resonance phenomenon, they have a high Q value and can easily stabilize their natural frequency. Therefore, the signal-to-noise ratio (S / N ratio) of the modulation signal applied to the laser light L using the vibration of the vibrating element 442 can be easily increased. As a result, the change in optical path length S3 to the mirror 3 due to the displacement of the mounting surface 221 can be detected with high accuracy, and a weighing device 1 capable of accurately measuring the weight of the object 9 can be realized.

[0025] Furthermore, the oscillator-type optical modulator 44 includes an oscillator circuit that generates a reference signal Ss using the oscillator element 442 as a signal source (source oscillator). Examples of oscillator circuits include inverter-type oscillator circuits and Colpitts-type oscillator circuits. These oscillator circuits can generate a reference signal Ss with high frequency stability by using the oscillator element 442, which has a high Q value for mechanical resonance phenomena. This also increases the signal-to-noise ratio of the reference signal Ss, and thus increases the signal-to-noise ratio of various signals based on the reference signal Ss. In addition, by using the oscillator element 442 as a signal source, less power is required to generate the reference signal Ss. For this reason, the laser interferometer 4 having the oscillator-type optical modulator 44 also contributes to reducing the power consumption of the weighing instrument 1.

[0026] Furthermore, the oscillator-type optical modulator 44 is small and lightweight. Therefore, the laser interferometer 4 having the oscillator-type optical modulator 44 also contributes to the miniaturization and weight reduction of the weighing instrument 1.

[0027] The beam splitter 46 splits the laser light L emitted from the laser light source 42 into two beams. One beam of laser light L returns to the beam splitter 46 via the mirror 3. The other beam of laser light L returns to the beam splitter 46 via the oscillator-type optical modulator 44. Both beams of laser light L are combined in the beam splitter 46 and received as interference light by the photodetector 47.

[0028] The light-receiving element 47 detects the intensity of the interference light (optical beat) and outputs a received signal S1 (optical beat signal). Examples of the light-receiving element 47 include a photodiode and a phototransistor.

[0029] The signal processing unit 48 calculates the change in optical path length S3 to the mirror 3 due to the displacement of the mounting surface 221, based on the received light signal S1 and the reference signal Ss generated using the vibrating element 442 as a signal source.

[0030] For example, the pre-processing unit and demodulation unit disclosed in Japanese Patent Application Publication No. 2022-38156 can be applied to the signal processing unit 48. In the pre-processing unit, the received signal S1 is pre-processed based on a reference signal Ss, and in the demodulation unit, the mirror displacement signal is demodulated from the pre-processed signal based on the reference signal Ss. The mirror displacement signal is a signal (phase change) that is added to the laser light L in accordance with the displacement of the mirror 3. The method of detecting such displacement by the laser interferometer 4 is called the optical heterodyne method. According to the optical heterodyne method, even when the phase of light cannot be directly measured, the change in optical path difference can be detected by slightly differentiating the frequencies of the two interfering laser beams L and detecting the optical beat. This makes it possible to detect the change in optical path length S3 to the mirror 3 with very high accuracy.

[0031] 1.4. Control Unit The control unit 5 shown in Figure 1 calculates the weight of the object to be measured 9 based on the change in optical path length S3 to the mirror 3 due to the displacement of the mounting surface 221, which is detected by the laser interferometer 4.

[0032] The control unit 5 calculates the weight of the object 9 when the elastic body 23 elastically deforms in the Z-axis direction according to the mass of the object 9, based on the change in optical path length S3 and the spring constant of the elastic body 23. Specifically, the load due to the mass of the object 9 corresponds to the product of the spring constant of the elastic body 23 and the amount of deformation of the elastic body 23 calculated from the change in optical path length S3. Based on this relationship, the control unit 5 calculates the load due to the mass of the object 9. Then, it calculates the weight of the object 9 from this load. Furthermore, if the gravitational acceleration at the location where the weighing scale 1 is installed is known, the control unit 5 calculates the mass of the object 9 from the calculated weight.

[0033] Therefore, in addition to the function of performing the above calculations, the control unit 5 may also have a function of storing the spring constant of the elastic body 23, the refractive index of the optical path of the laser light L, the gravitational acceleration of the location where the weighing device 1 is installed, and so on.

[0034] Each function of the signal processing unit 48 and the control unit 5 is realized by hardware, for example, a CPU, memory, and an interface. Such hardware may include, for example, a microcontroller. The CPU is a Central Processing Unit. Examples of memory include any non-volatile memory (ROM), any volatile memory (RAM), or a removable external memory element. Examples of interfaces include a digital input / output port such as USB (Universal Serial Bus). The functions of the signal processing unit 48 and the control unit 5 are realized by the CPU executing a program pre-loaded into memory. Alternatively, instead of, or in conjunction with, the method in which the CPU executes a program to realize the above functions, a method in which hardware such as an FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), other integrated circuits, or discrete components realizes the above functions may be used.

[0035] 2. Second Embodiment Next, a weighing apparatus according to the second embodiment will be described. Figure 3 is a schematic diagram showing the configuration of the weighing device 1 according to the second embodiment. The second embodiment will be described below, focusing on the differences from the first embodiment, and similar matters will be omitted from the description. In Figure 3, components similar to those in the first embodiment are denoted by the same reference numerals.

[0036] In the weighing device 1 according to the first embodiment described above, the weight of the object to be measured 9 is calculated based on the change S3 in the optical path length to the mirror 3 by the laser interferometer 4 and the spring constant of the elastic body 23. In contrast, the weighing device 1 according to the second embodiment employs a so-called force balance weighing method.

[0037] The support unit 2 shown in Figure 3 includes a weighing pan 22 having a mounting surface 221, an optical path conversion unit 25, a connecting body 262, an electromagnetic coil 264, and a magnet 266.

[0038] The connector 262 connects the weighing pan 22 and the electromagnetic coil 264. Specifically, the connector 262 has an upper part 262a extending downward from the back surface 222 of the weighing pan 22, a lower part 262b surrounding the magnet 266 located below the weighing pan 22, and a mirror mounting part 262c.

[0039] The mirror 3 shown in Figure 3 is attached to the mirror mounting section 262c. The optical path of the laser beam L emitted from the laser interferometer 4 is converted by the optical path conversion unit 25 and incident on the mirror 3. The optical path of the laser beam L reflected by the mirror 3 is converted by the optical path conversion unit 25 and returns to the laser interferometer 4.

[0040] The electromagnetic coil 264 is fixed to the outer surface of the lower part 262b. The electromagnetic coil 264 is electrically connected to the control unit 5. When the control unit 5 flows a current i through the electromagnetic coil 264, a magnetic field is generated around the electromagnetic coil 264, and an electromagnetic force is generated between it and the magnet 266. The control unit 5 has the function of adjusting the current i flowing through the electromagnetic coil 264 so that the load of the object to be measured 9 pushing the connecting body 262 downwards and the electromagnetic force of the electromagnetic coil 264 pushing the connecting body 262 upwards are in equilibrium (balanced). When the load and the electromagnetic force are in equilibrium, the control unit 5 obtains the current i flowing through the electromagnetic coil 264. Since this current i is proportional to the electromagnetic force, the weight of the object to be measured 9 can be calculated from the current.

[0041] Furthermore, whether or not the load and electromagnetic force are in equilibrium can be detected based on the change S3 in the optical path length to the mirror 3 by the laser interferometer 4. By inputting this change S3 in optical path length to the control unit 5, the required current i can be calculated. In other words, the control unit 5 has the function of calculating the weight of the object to be measured 9 based on the change S3 in the optical path length to the mirror 3 by the laser interferometer 4. In this specification, the state in which the forces (loads) are balanced is also referred to as "equilibrium."

[0042] In the second embodiment described above, the same effects as in the first embodiment can be obtained. Furthermore, the second embodiment is also useful because it can eliminate the effects of deterioration over time that can occur with mechanical springs and permanent magnets.

[0043] 3. Third Embodiment Next, a weighing apparatus according to the third embodiment will be described. Figure 4 is a schematic diagram showing the configuration of the weighing device 1 according to the third embodiment.

[0044] The third embodiment will now be described, focusing on the differences from the first embodiment, and similar aspects will be omitted. In Figure 4, components similar to those in the first embodiment are denoted by the same reference numerals.

[0045] In the weighing device 1 according to the first embodiment described above, the weight of the object to be measured 9 is calculated based on the change in optical path length S3 to the mirror 3 by the laser interferometer 4 and the spring constant of the elastic body 23. In contrast, the weighing device 1 according to the third embodiment calculates the weight of the object to be measured 9 based on the change in optical path length S3 due to the change in refractive index of the optical member 272 of the support part 2.

[0046] The support unit 2 shown in Figure 4 comprises a weighing pan 22 having a mounting surface 221, a base 24, and an optical member 272. The optical element 272 is connected to the back surface 222 of the weighing pan 22. The optical element 272 is positioned between the weighing pan 22 and the base 24, and its refractive index changes under the load of the mass of the object to be measured 9. The optical element 272 shown in Figure 4 is, as an example, a block-shaped element that transmits laser light L and is positioned in the optical path of the laser light L. The base 24 shown in Figure 4 has a through hole 242 that penetrates in the Z-axis direction. The laser light L emitted from the laser interferometer 4 is incident on the optical element 272 through the through hole 242.

[0047] The mirror 3 shown in Figure 4 is positioned on the optical element 272. Specifically, the mirror 3 shown in Figure 4 is formed at the interface between the optical element 272 and the back surface 222 of the weighing pan 22. With such a mirror 3, the light reflectivity of the back surface 222 can be utilized, thus ensuring good reflectivity. The laser light L incident on the optical element 272 propagates inside the optical element 272, is reflected by the mirror 3, and then propagates again inside the optical element 272 to return to the laser interferometer 4.

[0048] The laser interferometer 4 shown in Figure 4 uses laser light L to detect the change S3 in the optical path length to the mirror 3 due to the displacement of the mounting surface 221. The refractive index of the optical element 272 increases as the load due to the mass of the object being measured increases, as the optical element 272 is compressed. When the refractive index of the optical element 272 increases, the optical path length (optical distance) of the laser light L propagating through the optical element 272 also increases. In other words, the optical path length from the laser interferometer 4 to the mirror 3 increases.

[0049] The control unit 5 shown in Figure 4 stores the relationship between the magnitude of the load on the optical element 272 and the change in optical path length S3 to the mirror 3. Based on this relationship, the control unit 5 has the function of calculating the magnitude of the load based on the change in optical path length S3 to the mirror 3 and calculating the weight of the object to be measured 9.

[0050] Figure 5 is a schematic diagram showing a modified example of the optical component 272. The optical element 272 shown in Figure 5 is an optical fiber wound in a spiral shape along the upper surface of the base 24. The mirror 3 shown in Figure 5 is the end face of this optical fiber. The laser light L emitted from the laser interferometer 4 is incident on the optical fiber from the input / output end faces 31 and propagates in a spiral shape along the longitudinal direction of the optical fiber. It is then reflected by the mirror 3 and propagates again through the optical fiber to return to the laser interferometer 4. Therefore, the optical element 272 shown in Figure 5 can secure a long optical path length even in a space-saving manner. This allows for a large change in the optical path length when the optical element 272 is subjected to a load. As a result, the accuracy of calculating the weight of the object 9 to be measured can be improved.

[0051] The mirror 3 shown in Figure 5 is the end surface of the optical fiber. While a thin metal film may be deposited on this end surface to provide light reflectivity, it is preferable that light reflectivity is provided at the interface between the optical fiber and the outside air. Such a mirror 3 contributes to reducing the cost of the weighing device 1 due to its simple structure. The optical fiber used as the optical element 272 shown in Figure 5 may be a glass optical fiber or a resin optical fiber. However, considering the large rate of change in refractive index when subjected to a load, a resin optical fiber is preferred.

[0052] In the third embodiment described above, the same effects as in the first embodiment can be obtained. Furthermore, the third embodiment is also useful in that it can eliminate the effects of wind, convection, static electricity, magnetization of components, etc.

[0053] 4. Fourth Embodiment Next, a weighing apparatus according to the fourth embodiment will be described. Figure 6 is a schematic diagram showing the configuration of the weighing device 1 according to the fourth embodiment.

[0054] The following describes the fourth embodiment, focusing on the differences from the first embodiment, and omitting explanations of similar aspects. In Figure 6, components similar to those in the first embodiment are denoted by the same reference numerals.

[0055] The weighing device 1 according to the first embodiment described above uses the principle of a spring balance. In contrast, the weighing device 1 according to the fourth embodiment uses the principle of a balance scale. The support section 2 shown in Figure 6 includes a first weighing section 281, a second weighing section 282, a connecting section 283, and a fulcrum 284.

[0056] The first weighing unit 281 has a weighing pan 281a with a mounting surface 221. The weighing pan 281a with the mounting surface 221 is a tray on which the object to be measured 9 is placed. The bottom surface of the weighing pan 281a shown in Figure 6 is the mounting surface 221 on which the object to be measured 9 is placed.

[0057] The second weighing section 282 is the part where the compensation mass for the object to be measured 9 is set. Methods for setting the compensation mass in the second weighing section 282 include, for example, using electromagnetic force, using electrostatic force, using mass changes due to charging and discharging of capacitors or secondary batteries, using light radiation pressure, and placing weights on a tray. One or more of these methods may be used.

[0058] Of these, the method using electromagnetic force is implemented using electromagnetic coils, magnets, etc., as mentioned above. The method using electrostatic force is implemented, for example, using an electrostatic actuator.

[0059] The weighing device 1 according to this embodiment employs a so-called force-balance weighing method. Therefore, the compensation mass set in the second weighing section 282 is set so that the load due to it is in equilibrium (balanced) with the load due to the mass of the object to be measured 9 placed on the first weighing section 281. In Figure 6, as an example, there is a connector 262, an electromagnetic coil 264, and a magnet 266 similar to those in Figure 3. In this case, the weight of the object to be measured 9 is calculated from the compensation mass (electromagnetic force) when equilibrium is achieved.

[0060] Furthermore, whether the load due to the mass of the object under test 9 and the load due to the compensation mass are in equilibrium can be detected based on the change in optical path length S3 to the mirror 3 by the laser interferometer 4. By inputting this change in optical path length S3 to the control unit 5, the compensation mass required for equilibrium can be calculated. Then, the weight of the object under test 9 can be calculated from the compensation mass when equilibrium is achieved. In other words, the control unit 5 shown in Figure 6 has the function of calculating the weight of the object under test 9 based on the change in optical path length S3 to the mirror 3 by the laser interferometer 4.

[0061] In addition, weighing methods other than the force balance method may be employed. For example, when evaluating whether the mass of the object to be measured 9 is greater than or less than the reference mass, the change in optical path length S3 to the mirror 3 by the laser interferometer 4 may be used to evaluate the mass of the object to be measured 9.

[0062] The connecting portion 283 is a member that connects the first weighing section 281 and the second weighing section 282. As an example, the connecting portion 283 shown in Figure 6 extends horizontally, supporting the first weighing section 281 from below and supporting the second weighing section 282 from above.

[0063] The fulcrum 284 supports the central part of the connecting section 283 from below. As a result, the support section 2 functions as a balance that can examine the balance between the gravitational moment acting on the first weighing section 281 and the moment due to the electromagnetic force acting on the second weighing section 282. In other words, the connecting section 283 swings around the Y-axis as the pivot axis and comes to rest when the two moments are balanced.

[0064] The mirror 3 shown in Figure 6 is positioned on the support section 2. Specifically, a connecting section 283 is formed to protrude toward the opposite side (upwards) from the pivot point 284 shown in Figure 6, and the mirror 3 is positioned at this section. This mirror 3, as an example, has a reflective surface facing the positive X-axis. The optical path of the laser beam L emitted from the laser interferometer 4 is converted by the optical path conversion section 25 and incident on the mirror 3. The optical path of the laser beam L reflected by the mirror 3 is converted by the optical path conversion section 25 and returns to the laser interferometer 4. Note that the optical path conversion section 25 may be provided as needed and may be omitted depending on the arrangement of the laser interferometer 4.

[0065] The reflective surface of mirror 3 faces a direction different from the displacement direction of the mounting surface 221 (towards the positive X-axis). Mirror 3 oscillates around the Y-axis as its pivot axis, depending on the balance of the connection 283. Therefore, the optical path of the laser beam L incident on mirror 3 will fluctuate according to the oscillation angle. However, since the oscillation range is sufficiently narrow, the weight of the object 9 can be determined based on the change in optical path length S3 to mirror 3.

[0066] Figure 7 is a schematic diagram showing a modified version of mirror 3. The weighing apparatus 1 shown in Figure 7 is the same as the weighing apparatus 1 shown in Figure 6, except that the arrangement of mirror 3 is different. The mirror 3 shown in Figure 7 is positioned on the back surface 222 of the weighing pan 281a of the first weighing unit 281. Because the first weighing unit 281 is located at a large distance from the fulcrum 284 among the support units 2, the displacement when the object to be measured 9 is placed on the mounting surface 221 is large. Therefore, by positioning the mirror 3 on the back surface 222 of the weighing pan 281a, the rate of change in the optical path length when the object to be measured 9 is placed on the mounting surface 221 can be increased. As a result, the accuracy of calculating the weight of the object to be measured 9 can be improved.

[0067] Furthermore, depending on the rigidity of the connection part 283 and the weight of the object under test 9, the connection part 283 may deflect. In this case, the change in optical path length S3 detected by the laser interferometer 4 will be affected. Therefore, the control unit 5 may have a function to eliminate the effect of this deflection. For example, suppose the compensation mass when balanced is 1 mg, and the connection part 283 deflects so that the mounting surface 221 is displaced downward by 10 nm. In this case, the weight corresponding to the deflection of 10 nm can be subtracted from the weight of the object under test 9 calculated from the change in optical path length S3. Therefore, the control unit 5 may have a function to maintain the relationship between the compensation mass and the amount of deflection of the connection part 283 as a table or function.

[0068] The control unit 5 shown in Figures 6 and 7 has the function of adjusting the compensation mass so that the load exerted downward by the mass of the object to be measured 9 on the first weighing unit 281 and the load exerted downward by the compensation mass set on the second weighing unit 282 on the second weighing unit 282 are in equilibrium. Since the compensation mass when both loads are in equilibrium is equal to the mass of the object to be measured 9, the weight of the object to be measured 9 can be determined.

[0069] Furthermore, whether or not the two loads are in equilibrium is determined based on the change in optical path length S3 to the mirror 3 detected by the laser interferometer 4 (the change in optical path length to the mirror 3 due to the displacement of the mounting surface 221). By inputting this change in optical path length S3 to the control unit 5, the required compensation mass can be calculated.

[0070] In the fourth embodiment described above, the same effects as in the first embodiment can be obtained. In addition, in both Figure 6 and Figure 7, a retroreflective mirror may be used for mirror 3. This allows a large portion of the laser light L to be returned to the laser interferometer 4 even if the orientation of mirror 3 changes.

[0071] 5. Fifth Embodiment Next, a weighing apparatus according to the fifth embodiment will be described. Figure 8 is a schematic diagram showing the configuration of the weighing device 1 according to the fifth embodiment.

[0072] The fifth embodiment will now be described, focusing on the differences from the fourth embodiment, and similar aspects will be omitted. In Figure 8, components similar to those in the fourth embodiment are denoted by the same reference numerals.

[0073] The fifth embodiment is the same as the fourth embodiment, except that the compensation mass set in the second weighing unit 282 is changed over time, the change in optical path length S3 to the mirror 3 is detected by the laser interferometer 4, and the control unit 5 calculates the mass of the object to be measured 9 based on the detection result of the change in optical path length S3.

[0074] In the weighing device 1 according to the fifth embodiment, the object to be measured 9 is placed on the mounting surface 221, a compensation mass is set and brought to equilibrium, and then the compensation mass is changed over time with a constant amplitude. For example, if the method for setting the compensation mass is to use electromagnetic force, the compensation mass is oscillated by changing the current flowing through the electromagnetic coil over time. The time change of the current at this time is set so that the optical path length oscillates with a constant amplitude. In addition, the laser interferometer 4 detects the change in optical path length S3 to the mirror 3 due to the displacement of the mounting surface 221. In Figure 8, as an example, the mirror 3 is placed at the connection part 283, but the placement of the mirror 3 is not limited to this as long as it is at a position on the support part 2 where the displacement of the mounting surface 221 can be detected. The control unit 5 then calculates the mass of the object to be measured 9 based on the amplitude of the change in optical path length S3. An example of the specific procedure is as follows.

[0075] First, the object to be measured 9 is placed on the mounting surface 221, and a compensation mass is set so that the support unit 2, which is a balance, is in equilibrium. Let i1 be the current flowing through the electromagnetic coil when equilibrium is achieved. Next, the current flowing through the electromagnetic coil is changed with a constant amplitude A, centered around current i1. As a result, the support unit 2, which is a balance, also swings with a constant amplitude. At this time, the current flowing through the electromagnetic coil can be expressed as i1 + Asin(t), where t is the time. Next, the laser interferometer 4 detects the amplitude B of the change in optical path length S3 to the mirror 3. There is a correlation between the detected amplitude B of the change in optical path length S3 and the mass of the object to be measured 9. Specifically, when the mass of the object to be measured 9 is small, the amplitude B of the change in optical path length S3 is large, and when the mass of the object to be measured 9 is large, the amplitude B of the change in optical path length S3 is small. Therefore, the control unit 5 calculates the mass of the object to be measured 9 based on the amplitude B of the change in optical path length S3 and the correlation that has been determined in advance.

[0076] Alternatively, conversely, the amplitude of the time change of the compensating mass may be set so that the optical path length detected by the laser interferometer 4 changes at a constant amplitude, regardless of the mass of the object 9 being measured. For example, if the method for setting the compensating mass uses electromagnetic force, the amplitude A of the current i1 + Asin(t) is adjusted so that the amplitude B of the change in optical path length S3 detected by the laser interferometer 4 is constant. The control unit 5 then calculates the mass of the object 9 being measured based on the amplitude A of the current i1 + Asin(t) (the amplitude of the time change of the compensating mass). An example of a specific procedure is as follows.

[0077] First, the object to be measured 9 is placed on the mounting surface 221, and a compensation mass is set so that the support unit 2, which is a balance, is in equilibrium. Let i1 be the current flowing through the electromagnetic coil when equilibrium is achieved. Next, the current flowing through the electromagnetic coil is changed with an appropriate amplitude, centered around current i1. This causes the support unit 2, which is a balance, to oscillate. At this time, the current flowing through the electromagnetic coil is expressed as i1 + Asin(t), where t is the time. Next, the amplitude B of the change in optical path length S3 to the mirror 3 is detected by the laser interferometer 4. Next, the amplitude A of the current i1 + Asin(t) is adjusted so that the detected amplitude B of the change in optical path length S3 remains constant. There is a correlation between the amplitude A of the current i1 + Asin(t) and the mass of the object to be measured 9. Specifically, when the mass of the object to be measured 9 is small, the amplitude A of the current i1 + Asin(t) can be small, and when the mass of the object to be measured 9 is large, the amplitude A of the current i1 + Asin(t) needs to be large. Therefore, the control unit 5 calculates the mass of the object to be measured 9 based on the amplitude A and the pre-determined correlation.

[0078] According to this fifth embodiment, the mass of the object to be measured 9 can be measured directly, regardless of the gravitational acceleration at the location where the weighing scale 1 is installed. Therefore, the fifth embodiment is useful in that it allows for more accurate measurement of the mass of the object to be measured 9 without being affected by gravitational acceleration. Furthermore, the same effects as those of the fourth embodiment can be obtained in the fifth embodiment described above.

[0079] 6. Variations Next, modified examples of each of the above embodiments will be described.

[0080] The weighing device 1 according to each of the above embodiments may be equipped with a windproof box. The windproof box houses the components of the weighing device 1 according to each of the above embodiments and protects the components from wind pressure. This suppresses a decrease in measurement accuracy due to wind. In other words, it is possible to prevent the weight of the object to be measured 9 from becoming an unintended measurement due to wind pressure.

[0081] Each of the above embodiments of the weighing scale 1 may be equipped with an ionizer (static eliminator). The ionizer is placed near the components of the weighing scale 1 according to each embodiment and removes static electricity from the components. This suppresses a decrease in measurement accuracy due to static charge. In other words, it is possible to prevent the weight of the object to be measured 9 from becoming an unintended measurement due to static charge.

[0082] Each of the above embodiments of the weighing scale 1 may be equipped with a demagnetizer. The demagnetizer is placed near the components of the weighing scale 1 according to each embodiment and demagnetizes the components. This suppresses a decrease in measurement accuracy due to the magnetization of the components. In other words, it is possible to prevent the weight of the object to be measured 9 from becoming an unintended measurement due to the magnetization of the components.

[0083] The weighing device 1 according to each of the above embodiments may be equipped with a light-transmitting medium in which the internal pressure and gas type are controlled. Such a medium is placed on the optical path of the laser beam L. This suppresses a decrease in measurement accuracy due to changes in the environment such as pressure, temperature, and humidity of the space in which the weighing device 1 is placed. In other words, since the change in optical path length due to changes in the environment can be suppressed, it is possible to prevent the weight of the object to be measured 9 from becoming an unintended measurement. Furthermore, if the internal pressure is set to below atmospheric pressure, the effect of air resistance on the displacement of the support part 2 can be reduced. In addition, by controlling the gas type, the effect of a mixed gas such as air on the optical path length (the effect of fluctuations in optical path length due to fluctuations in the components of the mixed gas) can be reduced.

[0084] Furthermore, the weighing device 1 according to each of the above embodiments may be equipped with at least two or more of the following: a windproof box, an ionizer, a demagnetizer, and the medium described above.

[0085] Each of the above embodiments of the weighing instrument 1 may include a housing and a temperature and humidity control unit. The housing houses the components of each embodiment of the weighing instrument 1 and isolates the internal space from the outside. The temperature and humidity control unit adjusts the temperature and humidity of the internal space of the housing. This prevents unintended changes in the optical path length due to changes in temperature and humidity. Furthermore, when a liquid sample is placed in the internal space of the housing, the drying rate of the liquid sample can be controlled to be constant. For example, when continuously measuring the weight of a liquid sample, it becomes easier to eliminate the effects of drying and improve the accuracy of weight measurement. For example, when counting the number of ink droplets ejected from the head of an inkjet printer, the accuracy of counting based on the weight measurement result can be improved.

[0086] The control unit 5 of the weighing device 1 according to each of the above embodiments may have a function to continuously record or output measurement results such as the weight of the object to be measured 9. This allows, for example, when ink droplets are continuously ejected from the head of an inkjet printer, the pressure change upon impact, the weight change upon drying, etc., to be continuously recorded and output.

[0087] The weighing device 1 according to each of the above embodiments may be configured to simultaneously place multiple objects to be measured 9 on the placement surface 221. In this case, the control unit 5 may have a function to receive input for the number of objects to be measured 9, and a function to calculate the weight of each object to be measured 9 based on the measurement results of the multiple objects to be measured 9 and the input number. This makes it possible to easily measure the weight of each object.

[0088] 7. Effects of each of the above embodiments and each of the above modifications As described above, the weighing device 1 according to each embodiment and each modified example comprises a support unit 2, a mirror 3, a laser interferometer 4, and a control unit 5. The support unit 2 has a mounting surface 221 on which the object to be measured 9 is placed, and the mounting surface 221 is displaced according to the mass of the object to be measured 9. The mirror 3 is positioned on the support unit 2. The laser interferometer 4 uses laser light L to detect the change S3 in optical path length to the mirror 3 due to the displacement of the mounting surface 221. The control unit 5 calculates the weight or mass of the object to be measured 9 based on the detected change S3 in optical path length. The laser interferometer 4 also includes a laser light source 42 that emits laser light L, and a vibrator-type optical modulator 44 that has a vibrating element 442 and modulates the frequency of the laser light L using the vibration of the vibrating element 442. With this configuration, a laser interferometer 4 having an oscillator-type optical modulator 44 can be equipped, and the change in optical path length S3 to the mirror 3 due to the displacement of the mounting surface 221 can be accurately detected using laser interference technology. This makes it possible to realize a weighing instrument 1 that can measure the weight or mass of an object 9 with high precision while being miniaturized.

[0089] In the weighing device 1, the support part 2 has a weighing pan 22 having a mounting surface 221 and a back surface 222 located opposite the mounting surface 221, and the mirror 3 may be placed on the back surface 222. With this configuration, when the weighing pan 22 is displaced downward in accordance with the mass of the object 9 being measured, the back surface 222 and the mirror 3 positioned on the back surface 222 are also displaced downward by the same amount as the mounting surface 221. Therefore, if the mirror 3 is positioned on the back surface 222, the weight or mass of the object 9 being measured can be measured accurately.

[0090] In the weighing device 1, the support part 2 may have an elastic body 23. The elastic body 23 is connected to the back surface 222 of the weighing pan 22 and may elastically deform in accordance with the mass of the object to be measured 9 placed on the mounting surface 221. With this configuration, the elastic body 23 displaces the mounting surface 221 by an amount of displacement corresponding to the mass of the object to be measured 9. Therefore, the weight of the object to be measured 9 can be easily measured simply by placing the object on the mounting surface 221 of the weighing pan 22.

[0091] In the weighing device 1, the elastic body 23 may be connected to an annular portion of the back surface 222 of the weighing pan 22 that is located outside the mirror 3. With this configuration, when the object to be measured 9 is placed on the mounting surface 221, the orientation of the weighing pan 22 is suppressed to change significantly. In other words, the elastic body 23 can be elastically deformed while maintaining a good horizontal position of the mounting surface 221. This suppresses the occurrence of measurement errors due to unintended tilting of the mirror 3 and the instability of the object to be measured 9 due to unintended tilting of the mounting surface 221.

[0092] In the weighing device 1, the support section 2 may include a weighing pan 22 and an optical element 272. The weighing pan 22 has a mounting surface 221 and a back surface 222 located opposite the mounting surface 221. The optical element 272 is connected to the back surface 222 of the weighing pan 22, and its refractive index changes according to the mass of the object to be measured 9. The optical element 272 is also positioned in the optical path of the laser beam L and is transparent to the laser beam L. Furthermore, a mirror 3 is positioned on the optical element 272. With this configuration, the magnitude of the load due to the mass of the object being measured 9 can be calculated based on the change S3 in the optical path length to the mirror 3, and the weight or mass of the object being measured can be calculated.

[0093] In the weighing device 1, the mirror 3 may be formed at the interface between the optical element 272 and the back surface 222 of the weighing pan 22. With this configuration, the light reflectivity of the back surface 222 can be utilized in mirror 3, thus ensuring good reflectivity.

[0094] In the weighing device 1, the optical element 272 may be an optical fiber. Alternatively, the mirror 3 may be formed at the interface between the optical fiber and the outside air. This configuration allows for the creation of an optical element 272 that can secure a long optical path length even in a small space. This significantly increases the rate of change in the optical path length when the optical element 272 is subjected to a load. As a result, the accuracy of calculating the weight or mass of the object 9 can be improved.

[0095] In the weighing device 1, the support unit 2 may have a first weighing section 281, a second weighing section 282, a connecting section 283, and a pivot point 284. The first weighing section 281 has a mounting surface 221. The second weighing section 282 is set to a compensation mass for the object to be measured 9. The connecting section 283 connects the first weighing section 281 and the second weighing section 282. The pivot point 284 supports the connecting section 283 so that it swings. The control unit 5 sets the compensation mass for the second weighing section 282. Furthermore, a mirror 3 is positioned on the support unit 2. With this configuration, the weight or mass of the object to be measured 9 can be calculated from the compensatory mass when the support part 2 is in equilibrium.

[0096] In the weighing instrument 1, the control unit 5 may calculate the weight or mass of the object to be measured 9 based on the detection result of the change in optical path length S3 by the laser interferometer 4 and the setting result of the compensation mass. With this configuration, the weight or mass of the object 9 to be measured can be calculated from the compensated mass when equilibrium is reached, using a force-balance weighing method.

[0097] In the weighing device 1, the control unit 5 may change the compensation mass over time with a constant amplitude. Alternatively, the laser interferometer 4 may detect the amplitude of the change in optical path length S3 to the mirror 3, and the control unit 5 may calculate the mass of the object to be measured 9 based on the amplitude of the change in optical path length S3. With this configuration, the mass of the object to be measured 9 can be measured directly, regardless of the gravitational acceleration at the location where the weighing scale 1 is installed.

[0098] In the weighing device 1, the control unit 5 changes the compensation mass over time, the laser interferometer 4 detects the change in optical path length S3 to the mirror 3, and the control unit 5 adjusts the amplitude of the time change of the compensation mass so that the amplitude of the detected change in optical path length S3 is constant, and calculates the mass of the object to be measured 9 based on the adjusted amplitude of the time change of the compensation mass. With this configuration, the mass of the object to be measured 9 can be measured directly, regardless of the gravitational acceleration at the location where the weighing scale 1 is installed.

[0099] In weighing device 1, mirror 3 may have retroreflective properties. With this configuration, even if the mirror 3 is tilted, a large portion of the incident light on the mirror 3 can be returned to the laser interferometer 4. This suppresses a decrease in the detection accuracy of the change in optical path length S3 by the laser interferometer 4. In addition, the tolerance for the misalignment of the mirror 3 is increased, making it possible to realize a weighing device 1 that is easy to assemble.

[0100] In the weighing instrument 1, the laser interferometer 4 may further include a beam splitter 46, a photodetector 47, and a signal processing unit 48. The beam splitter 46 splits the laser beam L into two beams. The photodetector 47 receives the interference light of one laser beam L that has undergone a Doppler shift at the mirror 3 and the other laser beam L that has passed through the oscillator-type optical modulator 44, and outputs a received signal S1. The signal processing unit 48 calculates the change in optical path length S3 to the mirror 3 based on the received signal S1 and a reference signal Ss generated using the oscillator 442 as a signal source. With this configuration, the change in optical path length S3 to mirror 3 can be detected with very high accuracy using the optical heterodyne method.

[0101] Although the weighing device of the present invention has been described above based on the illustrated embodiment, the present invention is not limited thereto. For example, the weighing device of the present invention may be configured such that each part of the above embodiment is replaced with any component having a similar function, or any component may be added to the above embodiment. Furthermore, the weighing device of the present invention may have a configuration that combines two or more of the above embodiments. [Explanation of Symbols]

[0102] 1...Weighing device, 2...Support unit, 3...Mirror, 4...Laser interferometer, 5...Control unit, 9...Object to be measured, 22...Weighing pan, 23...Elastic body, 24...Base, 25...Optical path conversion unit, 31...Input / output end faces, 42...Laser light source, 44...Oscillator-type optical modulator, 46...Beam splitter, 47...Photodetector, 48...Signal processing unit, 221...Mounting surface, 222...Back surface, 242...Through hole, 262...Connection Body, 262a...upper part, 262b...lower part, 262c...mirror mounting part, 264...electromagnetic coil, 266...magnet, 272...optical component, 281...first weighing part, 281a...weighing pan, 282...second weighing part, 283...connection part, 284...fulcrum, 442...vibrating element, i...current, i1+Asin(t)...current, L...laser light, S1...received signal, S3...change in optical path length, Ss...reference signal

Claims

1. A support having a mounting surface on which an object to be measured is placed, wherein the mounting surface is displaced according to the mass of the object to be measured, A mirror arranged in the support portion, A laser interferometer that uses laser light to detect changes in the optical path length to the mirror due to the displacement of the aforementioned mounting surface, A control unit that calculates the weight or mass of the object to be measured based on the detected change in optical path length, Equipped with, The aforementioned laser interferometer is A laser light source that emits the aforementioned laser light, A vibrator-type optical modulator having a vibrating element and modulating the frequency of the laser light using the vibration of the vibrating element, A weighing device characterized by having the following features.

2. The support portion has a weighing pan having the aforementioned surface and a back surface located opposite to the aforementioned surface, The weighing apparatus according to claim 1, wherein the mirror is arranged on the back surface.

3. The weighing apparatus according to claim 2, wherein the support portion is connected to the back surface of the weighing pan and has an elastic body that elastically deforms according to the mass of the object to be measured placed on the aforementioned surface.

4. The weighing apparatus according to claim 3, wherein the elastic body is connected to an annular portion of the back surface that is located outside the mirror.

5. The aforementioned support portion, A weighing pan having a back surface opposite to the aforementioned mounting surface and the mounting surface described above, An optical member connected to the back surface of the weighing pan, the optical member whose refractive index changes according to the mass of the object to be measured, It has, The optical member is arranged on the optical path of the laser light and has transparency to the laser light. The weighing apparatus according to claim 1, wherein the mirror is arranged on the optical member.

6. The weighing apparatus according to claim 5, wherein the mirror is formed at the interface between the optical member and the back surface of the weighing pan.

7. The optical component is an optical fiber, The weighing apparatus according to claim 5, wherein the mirror is configured at the interface between the optical fiber and the outside air.

8. The aforementioned support portion, The first weighing unit having the aforementioned mounting surface, A second weighing unit in which a compensation mass for the object to be measured is set, A connecting part that connects the first weighing section and the second weighing section, A pivot point that supports the connecting portion so that the connecting portion swings, It has, The control unit sets the compensation mass to the second weighing unit, The weighing apparatus according to claim 1, wherein the mirror is arranged on the support portion.

9. The weighing device according to claim 8, wherein the control unit calculates the weight or mass of the object to be measured based on the detection result of the change in optical path length by the laser interferometer and the setting result of the compensation mass.

10. The control unit changes the compensation mass over time with a constant amplitude. The laser interferometer detects the amplitude of the change in the optical path length, The weighing device according to claim 8, wherein the control unit calculates the mass of the object to be measured based on the amplitude of the change in the optical path length.

11. The control unit changes the compensation mass over time. The laser interferometer detects the change in the optical path length, The weighing device according to claim 8, wherein the control unit adjusts the amplitude of the time change of the compensated mass so that the amplitude of the detected change in optical path length is constant, and calculates the mass of the object to be measured based on the adjusted amplitude of the time change of the compensated mass.

12. The weighing apparatus according to claim 1, wherein the mirror has retroreflective properties.

13. The aforementioned laser interferometer further, A beam splitter that splits the aforementioned laser light into two beams, one and the other, A photodetector receives interference light from one of the laser beams that has undergone a Doppler shift by the mirror and the other laser beam that has passed through the oscillator-type optical modulator, and outputs a received signal. A signal processing unit that calculates the change in the optical path length based on the light-receiving signal and the reference signal generated using the vibrating element as a signal source, A weighing device according to any one of claims 1 to 12, having the following:

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