JP2020085545A - Optical space measuring device - Google Patents

Abstract

To provide an optical space measuring device which achieves measurement of the surface, a three-dimensional shape, the shape in a space, air flow and the like with high accuracy by imaging reflection light generated from a measurement object.SOLUTION: An optical space measuring device includes: a light source part for irradiating an optical frequency comb, or a light source part for irradiating super continuum light; a spectroscopic part which consists of a prism or a diffraction grating and separates the irradiation light irradiated from the light source part; and a detection part consisting of a hyperspectral camera for detecting the reflected light generated by reflection of spectroscopy generated via the spectroscopic part by the measurement object.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical space measuring device, and more particularly, to an optical space measuring device in which an optical frequency comb or supercontinuum light is used to enhance the detection sensitivity of a measurement target.

In detecting the position of an object in space, there are methods of measuring time of flight (ToF: Time of Flight) and a stereo camera. However, in the measurement by the ToF or stereo camera, it is required to improve the accuracy of the camera when detecting with high accuracy. Further, as another method of detecting the position of an object, an active stereo method or the like in which light is projected and the position is measured from the projected pattern is also used. In this method, it was necessary to project a complicated pattern toward the measurement target. In addition, three-dimensional measurement (position detection) cannot be performed unless the projection pattern is projected on the plane with a certain size. The resolution of the camera is required even in the case of the active stereo method.

Therefore, a technique has been disclosed in which the detection accuracy is improved by selecting the wavelength of the light that is irradiated toward the measurement target (see, for example, Patent Document 1). According to Patent Document 1, a first object provided with a first diffraction grating and a second object provided with a second diffraction grating are arranged so as to face each other at a constant interval, and monochromatic light is applied to these diffraction gratings. Is a method for detecting the relative positions of both objects using diffracted light generated by both diffraction gratings and aligning them, and two or more monochromatic light beams having a desired wavelength are provided on the same optical path axis. There is disclosed a positioning method which is combined with the above, detects the relative positions of both objects independently for each wavelength, and performs the positioning based on one or more detection signals of them. Here, a plurality of lateral Zeeman laser light sources are used, and each light is separated by a polarization beam splitter.

JP-A-6-42918

The technique disclosed in the above-mentioned Patent Document 1 or the like is intended for measurement of the surface of a wafer or the like. Therefore, it is not suitable for three-dimensional measurement of an object, expansion of measurement objects such as visualization of air flow.

Therefore, as a result of earnest studies to realize the expansion of the measurement target such as three-dimensional measurement of the object and visualization of the air flow, the inventor has achieved effective measurement.

The present invention has been made in view of the above points, and an optical space measurement that captures reflected light generated from a measurement target and realizes measurement of the surface, three-dimensional, further, shape in space, air flow, etc. with high accuracy. Provide the device.

That is, the optical space measuring apparatus according to the first aspect of the present invention includes a light source unit that emits an optical frequency comb, a spectroscopic unit that disperses the irradiation light emitted from the light source unit, and a spectroscopic unit that is generated via the spectroscopic unit. And a detection unit that detects reflected light generated by being reflected by the measurement target.

The optical space measuring device according to the second embodiment is configured such that a light source unit that irradiates the supercontinuum light, a spectroscopic unit that disperses the irradiation light emitted from the light source unit, and a spectroscopic light generated through the spectroscopic unit is measured. And a detection unit that detects reflected light generated by reflection.

The optical space measuring apparatus according to the third aspect is characterized in that the spectroscopic unit is a prism or a diffraction grating.

The optical space measuring apparatus according to the fourth mode is characterized in that the irradiation light from the light source unit is sheet-like irradiation light.

The optical space measuring apparatus according to the fifth mode is characterized in that the detecting unit is a hyperspectral camera.

According to the optical space measuring apparatus of the present invention, a light source unit that irradiates an optical frequency comb or a light source unit that irradiates supercontinuum light, a spectroscopic unit that disperses the irradiation light emitted from the light source unit, and a spectroscopic unit are used. Since the spectroscopically generated spectrum is provided with a detection unit that detects the reflected light generated by being reflected by the measurement target, the reflected light generated from the measurement target is imaged and measured using the characteristics of the optical frequency comb or supercontinuum light. Measurements on the surface of the object, in three dimensions and in space can be realized with high accuracy.

It is the whole optical space measuring device schematic diagram. It is a schematic graph which shows the characteristic of an optical frequency comb. It is a schematic graph which shows the characteristic of supercontinuum light. It is a schematic diagram which shows the mode of spectroscopy when a prism is used for a spectroscopy part. It is a schematic diagram which shows the mode of spectroscopy when a diffraction grating is used for a spectroscopy part. It is a 1st schematic diagram which shows the mode of spectroscopy of a sheet-like irradiation light. It is a 2nd schematic diagram which shows the mode of spectroscopy of a sheet-like irradiation light.

As shown in the schematic view of FIG. 1, the optical space measuring apparatus 1 of the present invention includes a light source unit 10, a spectroscopic unit 20, and a detection unit 30. Then, the processing unit 40 is connected to the light source unit 10 and the detection unit 30 by the signal line 5. The spectrum generated via the spectroscopic unit 20 is applied to the measurement target 90, and the spectrum is reflected on the surface of the measurement target 90. The individual reflected light reflected is detected by the detection unit 30. From the measurement of the wavelength of the reflected light, the position (distance) of the measurement target 90, the shape of the surface 91 of the measurement target 90, and the like are obtained by the processing unit 40. The measurement target 90 is a convenience letter, a three-dimensional object, or an article as illustrated. It is not limited to these, and includes particles of smoke floating in a predetermined space.

The light source unit 10 is the first light source unit 11 that emits the optical frequency comb (L1). The light source unit 10 is the second light source unit 12 that emits supercontinuum light (L11). Since the light rays have different properties, either the first light source unit 11 or the second light source unit 12 is installed in the light source unit 10. In the figure, the optical frequency comb (L1) and the first light source unit 11, and the supercontinuum light (L11) and the second light source unit 12 are shown in the same drawing for the sake of space.

The optical frequency comb (L1) and the supercontinuum light (L11) are light beams generated by combining laser lights having a plurality of wavelengths having extremely uniform properties. Therefore, these (L1 and L11) are so-called white light rays obtained by mixing respective wavelengths (each color) as a base, and are sometimes referred to as white laser light. Therefore, the optical frequency comb (L1) and the supercontinuum light (L11) have essentially different properties from the natural light of sunlight and artificial white light such as incandescent lamps or fluorescent lamps. The properties of the optical frequency comb (L1) and the supercontinuum light (L11) are as follows.

The optical frequency comb (L1) emitted from the first light source unit 11 is an optical signal having a comb-shaped spectrum of components arranged at equal intervals on the frequency axis and has coherent interference. Light with good coherence and stable short laser pulse of femto (1/1000 trillion) second. When the frequency spectrum of the light wave modulated by the repetitive wave is obtained, a comb-shaped spectrum of parallel combs with small regular intervals before and after the optical frequency is obtained. The obtained spectral lines (tooth of the optical comb) are arranged at positions of integral multiples of the modulation frequency.

FIG. 2 is a schematic diagram showing the characteristics of the optical frequency comb (L1). In the schematic diagram, the horizontal axis represents frequency and the vertical axis represents light intensity. The optical frequency comb (L1) is a light source having a plurality of spectra and having good straightness, and at the same time, the frequency intervals (see arrows in the figure) are arranged in a row. Therefore, the individual frequency bands are clearly separated. From this state, it is called a comb. Therefore, light having a stable intensity appears for each specific wavelength at regular intervals.

The optical frequency comb (L1) generator (first light source unit 11) is equipped with, for example, a Fabry-Perot resonator in which both surfaces of an electro-optic crystal (lithium niobate LiNbO ₃ ) are sandwiched by mirrors. Stable laser light is incident on the resonator and phase modulation by microwaves is applied. Then, the optical frequency comb (L1) is emitted from the first light source unit 11.

In the supercontinuum light (L11), a pulse emitted from a pulse laser is incident on a nonlinear medium such as a highly nonlinear fiber, and self-phase modulation, mutual phase modulation, four-wave mixing, Raman scattering, etc. generated in the nonlinear medium. It is light whose spectrum has been expanded to an ultra-wide band from the beginning due to the nonlinear optical effect. The supercontinuum light (L11) is a wide-angle laser light having a plurality of spectra and good straightness, and also having good frequency continuity. The supercontinuum light (L11) is generated by the second light source unit 12 by the above-described processing and is emitted from the second light source unit 12.

FIG. 3 is a schematic diagram showing the characteristics of supercontinuum light (L11). In the schematic diagram, the horizontal axis represents wavelength and the vertical axis represents spectral intensity. The supercontinuum light (L11) emitted from the second light source unit 12 has a wavelength range of 400 to 2400 nm, though it depends on the material of the optical fiber, and has a clearly wide wavelength range compared to the short wavelength laser beam. Have. Moreover, since the supercontinuum light (L11) is light generated based on the stable laser light as described above, the light intensity is also secured.

Here, returning to the schematic view of FIG. As described above, both the optical frequency comb (L1) and the supercontinuum light (L11) are light beams including a plurality of types (multi-regions) of wavelengths. Therefore, it is necessary to perform spectral analysis for each individual wavelength (each individual wavelength region) in consideration of the size of the measurement target and the resolution based on the wavelength. Therefore, the spectroscopic unit 20 is provided. A prism 21 or a diffraction grating 22 is used as the spectroscopic unit 20.

The schematic diagram of FIG. 4 is an example in which a prism 21 is used in the spectroscopic unit 20. The optical frequency comb (L1) or the supercontinuum light (L11) is emitted toward the prism 21 from the right side of the paper. The optical frequency comb (L1) is transmitted through the prism 21 to be separated into spectra, and emitted (emits light) from the prism 21 as a spectrum (L2). Similarly, the supercontinuum light (L11) is transmitted through the prism 21 to be spectrally separated, and is radiated (emits light) from the prism 21 as spectral (L12).

The schematic diagram of FIG. 5 is an example in which the diffraction gratings 22 and 23 are used in the spectroscopic unit 20. FIG. 5A is a schematic diagram of the transmission diffraction grating 22. An optical frequency comb (L1) or supercontinuum light (L11) is emitted toward the transmission type diffraction grating 22 from the right side of the paper. When the optical frequency comb (L1) is transmitted through the transmissive diffraction grating 22, it is separated into individual wavelengths (individual wavelength regions), and is radiated (emits light) from the transmissive diffraction grating 22 as spectrum (L2). .. In the case of supercontinuum light (L11), the spectrum (L2) is emitted (emits light) from the transmissive diffraction grating 22.

FIG. 5B shows the reflection type diffraction grating 23. The optical frequency comb (L1) or the supercontinuum light (L11) is emitted toward the reflection type diffraction grating 23 from the right side of the paper. When the optical frequency comb (L1) is reflected on the surface of the reflection type diffraction grating 23, it is split into individual wavelengths (individual wavelength regions) by fine irregularities (not shown) on the surface, and is split into spectra (L2). ) Occurs as reflected light. In the case of supercontinuum light (L11), the spectrum (L12) is generated as reflected light. In the case of the reflection type diffraction grating 23, a mirror (not shown) for appropriately reflecting the spectrum (L2, L12) is also properly provided.

As described above, the optical frequency comb (L1) and the supercontinuum light (L11) are light rays including a plurality of wavelength bands. Therefore, when the measurement target 90 is measured, the light rays of the original light source are dispersed according to the wavelength of the light, so that a specific wavelength can be selected according to the size and shape of the measurement target. Therefore, it is useful for controlling focus and improving resolution.

Further, the optical frequency comb (L1) emitted from the first light source unit 11 and the supercontinuum light (L11) emitted from the second light source unit 12 are both in the form of sheet-like irradiation light. The sheet-shaped irradiation light is a light beam that is irradiated in a strip shape, and also includes a form in which a plurality of irradiation devices (irradiation ports) are arranged side by side to imitate a strip shape. By increasing the number of irradiation devices, it is possible to irradiate light rays to a larger area. By using the sheet-like irradiation light, the irradiation area of the spectrum of the measurement target is expanded, and the efficiency of scanning of the measurement target is increased.

As can be seen from the schematic diagram of FIG. 6, the sheet-like spectrum (L2) or spectrum is irradiated by irradiating the long prism 21 with the optical frequency comb (L1) or the supercontinuum light (L11) of the sheet-like irradiation light. (L12) is emitted (emits light) from the prism 21.

Similarly, in FIG. 7A, a transmission type diffraction grating 22 on a long plate is prepared. The optical frequency comb (L1) or the supercontinuum light (L11) of the sheet-shaped irradiation light is emitted toward the transmission type diffraction grating 22, and the sheet-shaped spectrum (L2) or spectrum (L12) is emitted from the transmission type diffraction grating 22. It is illuminated (emits light). In FIG. 7B, a reflection type diffraction grating 23 on a long plate is prepared. The optical frequency comb (L1) or the supercontinuum light (L11) of the sheet-like irradiation light is emitted toward the reflection type diffraction grating 23, and the sheet-like spectrum (L2) or the spectrum is obtained through the reflection on the surface of the reflection type diffraction grating 23. (L12) emits light.

In order to irradiate the measurement target 90 with the spectrum (L2, L12) emitted from the spectroscopic unit 20 without leakage, the prism 21, the transmission type diffraction grating 22, and the reflection type diffraction grating 23 are provided with a servo motor ( (Not shown) is provided, and the angle and position are controlled by the processing unit 40.

As described above, the optical frequency comb (L1) or the supercontinuum light (L11) is dispersed into each wavelength included in each (each individual wavelength region), and the generated spectrum (L2) or (L12) is , Is irradiated to the measurement target 90 (see FIG. 1). Then, it is reflected on the surface 91 of the measurement target 90. The reflected light is detected by the detection unit 30. The reflected light (L3) based on the spectrum (L2) of the optical frequency comb (L1) is detected by the first detection unit 31. The reflected light (L13) based on the spectrum (L12) of the supercontinuum light (L11) is detected by the second detection unit 32.

A hyper spectrum camera is preferably used for the detection unit 30 (31, 32). The hyperspectral camera can individually acquire the light intensity in a very narrow wavelength range for the reflected light (L3, L13) of each wavelength reflected by the measurement target. Therefore, finer color information is more accurately determined. Further, not only the visible light region but also the near-infrared (750 to 1700 nm) region can be photographed, and the spectrum analysis of the region is also possible.

The output of the light source unit 10 (the first light source unit 11, the second light source unit 12) and the like are controlled, the position of the spectroscopic unit 20 is controlled, and the imaging data of the detection unit 30 (the first detection unit 31, the second detection unit 32) is used. The processing units 40 are connected to the respective units for the processing and the analysis based on them. The processing unit 40 is a known personal computer or the like. When analyzing the reflected light (L3, L13) generated from the measurement target 90 and processing the data, a known method for analyzing the color information of the reflected light such as the coaxial confocal method is used. In the case of the same system, the focal points are focused at different positions for each wavelength. Therefore, the distance to the object and the surface shape of the object can be obtained from the relationship between the wavelength and the focus. In particular, since the sheet-shaped irradiation light is generated, naturally the reflected light also becomes a sheet shape and the efficiency of scanning of the measurement target is improved, and the surface of the article as the measurement target, and further, the space as the measurement target. It also enables three-dimensional measurement of the particles inside.

The optical space measuring apparatus of the present invention has a great feature in that the light source is the optical frequency comb (L1) and the supercontinuum light (L11), and the characteristics of each light are as described above. Therefore, depending on the characteristics of each light, the following different usages are assumed.

In the case of the optical frequency comb (L1), individual lights are clearly separated for each frequency (each wavelength) as shown in the schematic diagram of FIG. The use of the optical frequency comb (L1) has the following advantages. (I) Since the spectrum (L2) that is strong and clearly separated by the narrow spectral width is obtained, the object at the specific position is more clearly separated. (Ii) Since the optical frequency comb (L1) itself is separated for each frequency, the required performance of the filter used when the specific wavelength is extracted by the optical filter is reduced. That is, even if it does not depend on the optical filter, it has high separation performance, and the efficiency in focusing is good. (Iii) Since the optical frequency comb (L1) is included separately for each frequency (for each of a plurality of wavelengths), it is possible to specify the three-dimensional position of many moving objects at the same time. For example, when an optical frequency comb (L1) having a wavelength range of 380 to 760 nm with an interval of 20 nm is generated, the three-dimensional position can be specified by 20 divisions.

In the case of the supercontinuum light (L11), it has a wide wavelength range as shown in the schematic view of FIG. The use of the supercontinuum light (L11) has the following advantages. (I) There is no defective region in the spectrum width as compared with the above-mentioned optical frequency comb (L1). From this, it becomes possible to specify a higher three-dimensional position according to the spectral performance of the light receiving unit (detection unit 30) side. (Ii) The number of parameters for controlling the light source is small, and the position of the specific object can be accurately measured only by the measuring device side. For example, in the case of supercontinuum light (L11) in the wavelength region of 380 to 760 nm, a bandpass filter with a width of 5 nm is attached to the light receiving unit (detection unit 30) side to specify the three-dimensional position by the resolution of 80 divisions. It will be possible. In addition, the bandpass filter is switched at high speed, and the measurement area can be expanded.

The selection of the optical frequency comb (L1) or the supercontinuum light (L11) as the light source is considered according to the measurement target. For example, in order to accurately measure a surface structure whose size, depth, and shape are known to some extent, such as confirmation of processing accuracy, the intensity of the light beam is high and the optical frequency comb (L1) with a uniform wavelength range is used. Use is preferred. Further, in the case of an object such as a driver's seat or the like, where there is a wide interior such as an air flow in the vehicle, it is preferable to use a supercontinuum light (L11) having a wide wavelength range. For example, an air flow containing smoke is ventilated into the vehicle, and the spectrum of supercontinuum light is applied to this to analyze the depth in three dimensions. Of course, these are examples, and they can be appropriately combined to take advantage.

The optical space measuring device of the present invention enables highly accurate measurement according to the measurement target by using the optical frequency comb or the supercontinuum light as the light source. In particular, the wavelength range used is wider than that of existing measuring devices using only limited types of laser light. Therefore, it is a promising alternative to the device.

1 Optical Space Measuring Device 10 Light Source Section 11 First Light Source Section 12 Second Light Source Section 20 Spectroscopic Section 21 Prism 22, 23 Diffraction Grating 30 Detecting Section 31 First Detecting Section 32 Second Detecting Section 40 Processing Section 90 Measurement Target L1 Optical Frequency Com L11 Supercontinuum light L2, L12 Spectral L3, L13 Reflected light

Claims (5)

A light source unit for irradiating an optical frequency comb,
A spectroscopic unit that disperses the irradiation light emitted from the light source unit,
An optical space measurement device, comprising: a detection unit configured to detect reflected light generated by the measurement target reflecting the spectrum generated via the spectroscopic unit. A light source unit that emits supercontinuum light,
A spectroscopic unit that disperses the irradiation light emitted from the light source unit,
An optical space measurement device, comprising: a detection unit configured to detect reflected light generated by the measurement target reflecting the spectrum generated via the spectroscopic unit. The optical space measurement device according to claim 1, wherein the spectroscopic unit is a prism or a diffraction grating. The optical space measuring device according to claim 1, wherein the irradiation light from the light source unit is a sheet-shaped irradiation light. The optical space measurement device according to claim 1, wherein the detection unit is a hyperspectral camera.

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