JP6995376B2 - 3D object information measuring device - Google Patents

Description

The present invention relates to a measuring device that measures complex amplitude information or phase information of light, which is three-dimensional structural information of an object. The present invention relates to a three-dimensional object information measuring device using an interference meter.

With the development of industry, industry, and medicine in recent years, more accurate and high-speed measurement technology is required. In particular, the complex amplitude information and phase information of the light of an object are important three-dimensional information and are very useful for understanding phenomena such as the structure and deformation of an object.

For example, complex amplitude measurement of objects that emit refraction or objects illuminated by natural light or heat from a thermal light source is important for applications such as precise shape measurement of products, dynamic observation of living organisms, and imaging of internal structures of living organisms. It is also important to obtain three-dimensional shape information of the object structure such as the thickness distribution and refractive index of the object, and optical measurement technology with features such as non-invasive, non-contact, high sensitivity, and parallel processability is indispensable. It has become.

In addition, phase information is also important as three-dimensional information, and it is required to accurately grasp the wavefront of the emitted light of the laser and to measure the wavefront of the transmitted light in order to grasp the information of the structure of the transparent object. For example, wavefront information (phase information) is widely applied, such as measurement of invisible gas jet flow, detailed inspection of lenses, and measurement of thickness / refractive index distribution of transparent objects such as cells and droplets. Further, if it is a reflective object, the phase information can accurately measure the shape of the surface of the object.

(Background of complex amplitude information measurement)
The simplest method for observing phenomena that occur at high speed, such as movement of an object or minute changes in shape, is to directly capture only the brightness information (intensity information) of the object with a high-speed camera. However, in order to accurately measure the object information, not only the brightness information (intensity information) but also the complex amplitude information (that is, the brightness information (intensity information) and the phase information) are required. For example, in shooting with a high-speed camera, there is a problem that only the strength information of an object can be recorded, and it cannot be applied to a transparent object.

As a method for solving the above problems, an optical measurement technique for obtaining complex amplitude information by an interference measurement method is disclosed. As an example, FIG. 19 shows an optical system using a holographic apparatus. In the holographic apparatus 50 shown in FIG. 19, the light (object irradiation light) and the reference light for irradiating the measurement target 100 with the laser beam emitted from the laser light source 51, which is a light source having high coherence, with the beam splitter 52. Separate into. The object irradiation light irradiates the measurement target 100 through the objective lens 53a, the lens 54a, and the mirror 55a. The object light, which is the reflected light from the measurement target 100, is incident on the CCD camera 57 via the beam splitter 56. On the other hand, the reference light is incident on the CCD camera 57 via a path in which the measurement target 100 does not exist, specifically, a mirror 55b, an objective lens 53b, a lens 54b, a mirror 55c, and a beam splitter 56. As a result, the CCD camera 57 captures an interference fringe between the reference light and the object light, and the computer performs a predetermined calculation based on the interference fringe to obtain complex amplitude information (intensity information and phase information) of the measurement target 100. Is obtained.

In these holographic devices, interference fringes are created by irradiating the image pickup element of the CCD camera 57 with reference light at a right angle. Therefore, it is difficult to obtain a clear reproduced image because not only the necessary + 1st-order diffraction image but also the unnecessary 0th-order diffraction image and -1st-order diffraction image overlap with the reproduction image obtained by Fresnel conversion of the interference fringes. It has become. Therefore, in order to obtain a clear reproduced image without a 0th-order diffraction image or a -1st-order diffraction image, a phase-shift digital holography apparatus that shifts the phase of the reference light into a plurality of steps has been proposed (Patent Document 1). For example, a phase shift digital holography apparatus that shifts the phase of the reference light into three or four stages by using a piezoelectric element has been proposed. Further, as a method of shifting the phase of the reference light, a phase shift digital holography apparatus using a phase plate has also been proposed.

In such a phase shift digital holography apparatus, the phase of the reference light is changed by, for example, π / 2 [rad], and a plurality of interference fringes are recorded in the CCD camera 57. By numerically calculating the plurality of interference patterns, it is possible to obtain a reproduced image without a 0th-order diffraction image or a -1st-order diffraction image. However, since a plurality of interference fringes are required, there is a problem that it is not possible to record and reproduce a phenomenon that occurs at high speed when the object moves quickly or when the minute shape changes quickly, that is, when the object changes rapidly.

On the other hand, Patent Document 2 has a phase obtained by interfering a plurality of reference lights having different phase values with each other and an object light emitted from a subject irradiated with the light in order to solve the above problem. We are proposing a digital holography device equipped with a reproduction image generation unit that creates a reproduction image of a subject based on distribution data. That is, the phase shift element that converts the incident light into a reference light group consisting of a plurality of reference lights having different phase values and emits the light, and the phase distribution data generated by interfering the reference light group with the object light. It includes an image pickup unit having an image pickup surface for recording, and the reproduction image generation unit generates a reproduction image of a subject based on the information of the phase distribution data.

According to the configuration of the digital holography apparatus, it is possible to simultaneously obtain a plurality of reference lights having different phase values from the incident light. The phase distribution data obtained by interfering the reference light group composed of a plurality of reference lights with the object light is in a state where the reference light of each phase value and the object light interfere with each other. Therefore, if the information of the phase distribution data is used, it is possible to obtain a plurality of data in which the reference light having different phase values and the object light interfere with each other in one shooting, so that the information necessary for obtaining a clear reproduced image can be obtained. Can be obtained instantly. Therefore, it is possible to realize real-time observation of a moving subject or a subject such as an instantaneous image deformation of the subject.

However, in the above digital holography device,
・ Requires a highly coherent light source such as a laser light source ・ Noise associated with the laser light source is generated ・ Since the interference between the reference light and the object light is used, the device is large and complicated due to the large number of optical elements used.・ Since high installation accuracy is required for optical elements, there is a problem that installation is difficult and installation time is long.

The self shown in Non-Patent Document 1 and Non-Patent Document 2 is used as an interference measurement using light with low coherence such as natural light, fluorescence, and light from a thermal light source without using a light source having high coherence such as laser light. There is an interference method. FIG. 20 is a schematic configuration diagram of the measuring device 60 described in Non-Patent Document 1. The measuring device 60 is a method of generating two types of light waves on the same optical path by using a spatial light modulator (SLM) 61 and recording the fringes generated as a result of their interference with each other. It is necessary to change the pattern to be used and record it sequentially. Therefore, although the measuring device 60 can be simplified, since a diffractive optical element such as SLM61 is used, the diffraction efficiency is lowered and the reproduced image is deteriorated. There is a problem that aberrations occur and image distortion occurs, and because it is a sequential recording method, it is not possible to realize real-time observation of subjects such as moving subjects and subjects that deform instantly. ..

Non-Patent Document 3 proposes a method of dividing a light wave into two and tilting one of the wavefronts of the light wave in order to reproduce an image in one recording. In Non-Patent Document 3, it is necessary to improve coherence by using a narrow band bandpass filter in order to incline one of the light waves. Further, when the light wave is divided into two, the two light waves pass through different optical paths, so that there is a problem that they are easily affected by external disturbance such as vibration.

Non-Patent Document 4 proposes a method of using a lens having a polarization characteristic to reproduce an image in one recording. However, this method theoretically requires a special lens having polarization characteristics, but there is a problem that it is difficult to actually realize this element, and even if it is realized, it is extremely expensive.

Non-Patent Document 5 also reports a technique of generating two light waves with different polarizations and performing phase shift using a Pockels cell to reproduce an image, but since a special element is used, it is general purpose. There is a problem that it is not possible to measure dynamic objects because it is poor in nature and needs to be recorded sequentially.

(Background of phase information measurement)
Conventional interference measurement techniques that use reference light to measure phase are extremely vulnerable to external disturbances such as vibration and temperature, and must be immune to disturbances for practical use. Therefore, a new interferometry technique that suppresses the influence of disturbance by an interferometry method that uses self-interference through the same optical path without using reference light has been reported. However, since it is necessary to sequentially record a plurality of interference fringe images and a time interval is required to acquire each image, there is a problem that the image is eventually affected by external vibration.

In recent years, as a technique for solving the above problem, some techniques capable of instantly acquiring a phase image have been reported. For example, as a method for measuring the wavefront of light, a shearing interferometer is used in which a wavefront reflected from the surface to be inspected and a wavefront slightly deviated from the reflected wavefront are superposed. The shearing interferometer does not require a reference light separate from the wavefront to be measured, and records interference with itself, so it has the advantage of being less susceptible to disturbance. Further, among the shearing interferometers, a radial shearing interferometer capable of measuring a plurality of interference images in one shot by using polarization has been proposed (Non-Patent Document 6). However, the radial shearing interferometer described in Non-Patent Document 6 has a very large number of optical elements required for the interferometer, optical adjustment is complicated and difficult, and the optical system is large, which is a small and inexpensive device. It has a problem that it is difficult to put it into practical use.

Further, a technique for measuring the wavefront with a simpler interferometer by using a diffractive element has also been reported (Non-Patent Document 7). Since this device does not require a complicated interferometer but uses a diffractive element, it is greatly affected by the diffractive element, and the diffraction efficiency differs depending on the polarization direction, resulting in deterioration of the reproduced image. Further, since the optical path is divided into two, there is a problem that it is easily affected by a disturbance.

Further, a wavefront measurement technique that combines two Sagnac interferometers, which are relatively simple interferometers without the need for a diffractive element, has also been proposed (Non-Patent Document 8). However, since it requires sequential recording, it is greatly affected by vibration, and there is a problem that wavefront measurement cannot be performed instantly.

On the other hand, according to the configuration of the digital holography apparatus of Patent Document 2, it is possible to obtain a plurality of images in which the reference light having different phase values and the object light interfere with each other in one shooting, so that the reproduced image is of course. , The phase image can also be reproduced instantly. Then, it is possible to realize real-time observation of the subject, such as a moving subject or an instantaneous deformation of the image of the subject.

However, since the above digital holography device uses interference due to reference light,
-Since many optical elements are used, the device becomes large and complicated.-High position accuracy is required for the optical elements, which makes installation difficult and lengthens the installation time.-There are problems such as being vulnerable to external disturbance.

Japanese Unexamined Patent Publication No. 2005-283683 (published on October 13, 2005) Patent No. 4294526

J. Rosen, and G. Brooker, Opt. Let. 32,912-914 (2007). W. Qin, and et. al. , Journal of Biomedical Optics 19, p. 060503 (2014). J. Hong, and M. K. Kim, Opt. Let. 38,5196-5199 (2013). Z. Zhu, and Z. Shi, Frontiers in Optics 2015, Paper FTh4D. 2, (2015). D. N. Naik, G. et al. Pedrini, and W. Osten, Opt. Exo. 21, p. 3990 (2013). N. Gu, L. Huang, Z. Yang, and C.I. Rao, Opt. Exp. 19,4703 (2011). N. I. T. Arellano, D. I. S. Garcia, A. M. Garcia, G.M. R. Zurita, A. M. Perez, J. et al. M. M. Gomez, G.M. R. Lopez, A. G. Rosas, and L. G. Lettuce ,, Rev. Mex. Fis. 58,335 (2012). N. I. T. Arellano, D. I. S. Garcia, and A. M. Garcia, Opt. Exp. 21, 31983 (2013).

The present invention has been made to solve the above-mentioned various problems.
-It is possible to obtain three-dimensional object information of an object using an object that self-lumines by fluorescence, an object illuminated by natural light or light from a thermal light source, or an coherent light source such as laser light. The optical element group is simple and easy to obtain, and the arrangement and adjustment of the optical element is easy. It is an object of the present invention to provide a three-dimensional object information measuring device capable of measuring phase information) or phase information at high speed.

The three-dimensional object information measuring device according to the present invention is
A linear polarization converter that converts object light coming from an object into linear polarization,
A shearing interferometer that causes shearing interference of the object light converted to linear polarization, and
A circular polarization conversion unit that converts the vertical polarization and horizontal polarization of the interference light by the shearing interferometer into circular polarization, and
The interference fringe acquisition unit that records the circular polarization by one shooting, and
A calculation unit that calculates complex amplitude information of the object from the recorded image of the interference fringe acquisition unit,
It is a three-dimensional object information measuring device equipped with
In the recorded image, the phase differs depending on the pixel, and the phase is different.
The calculation unit
An extraction unit that extracts pixels from the recorded image for each phase and generates a plurality of extraction data consisting of pixels having the same phase and pixels lacking pixel values.
An interpolation unit that generates a plurality of interpolation data that approximates a plurality of interference images having different phases by performing pixel interpolation for each of the plurality of extracted data.
An arithmetic unit that calculates complex amplitude information or phase images from the plurality of interpolated data,
It is a three-dimensional object information measuring device characterized by being provided with.

The shearing interferometer may be a radial shearing interferometer.

The radial shearing interferometer
The light incident from the linear polarization conversion unit is divided into two, and one of the two divided lights is re-incidented and the other is re-incidented in the same optical path as the one light in the opposite direction. Polarized beam splitting element that combines with the light of
Two lenses arranged in the optical path with different focal lengths and
Equipped with
The light coupled by the polarized beam dividing element may be output as the interference light.

The interference fringe acquisition unit is
A polarizing element array having a plurality of types of polarization regions in which the polarization direction and the phase shift amount of the incident light are different from each other,
An image sensor coupled to the polarizing element array and having pixels having a one-to-one correspondence with each of the polarization regions.
It may be a polarizing element array type image pickup apparatus provided with.

The object light is Fourier transformed light.
The shearing interferometer causes the Fourier planes of the object light to interfere with each other.
The interference fringe acquisition unit records the interference fringes of the circular polarization, and records the interference fringes.
The calculation unit may calculate the complex amplitude information by obtaining the complex amplitude of the spatial coherence function from the plurality of interpolation data by using a phase shift method and performing an inverse Fourier transform.

The object light is light that the coherent light reflects or passes through the object.
The shearing interferometer causes the object lights to interfere with each other.
The interference fringe acquisition unit records the interference fringes of the circular polarization, and records the interference fringes.
The arithmetic unit obtains a phase-contrast image of the interference light from the plurality of interpolated data by using a phase shift method, and reconstructs the phase-contrast image from the Zernike polynomial, Legendre polynomial, or the central portion with reference to the central portion. The phase image may be calculated by reconstructing the wavefront by applying the above method.

According to the present invention, the device can be configured with simple components, optical adjustment is easy, it is highly robust to external disturbances, and complex amplitude information or light such as a moving object or a shape-changing object is used. It is possible to provide a three-dimensional object information measuring device capable of instantaneously measuring three-dimensional information such as a wave surface (phase image information).

It is explanatory drawing which shows the principle of the 3D object information measuring apparatus which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the principle of obtaining 3D structure imaging from four interference images. It is a schematic block diagram of the 3D object information measuring apparatus which concerns on 1st Embodiment of this invention. It is explanatory drawing of the optical path in the 3D object information measuring apparatus shown in FIG. (A) is a side view showing the configuration of an interference fringe acquisition unit of the three-dimensional object information measuring device, (b) is a plan view of a polarizing element array of the interference fringe acquisition unit, and (c) is a plan view. It is a top view of the image pickup surface of the interference fringe acquisition part. It is a functional block diagram of the computer of the 3D object information measuring apparatus. (A) to (e) are diagrams for explaining the process of obtaining a reproduced image from the recorded image acquired by the interference fringe acquisition unit. It is a schematic block diagram which shows the mode in which a 3D object information measuring apparatus measures a reflective object illuminated by a light source. It is a schematic block diagram which shows the mode in which a 3D object information measuring apparatus measures a transmitted object illuminated by a light source. It is a schematic block diagram which shows the mode that the 3D object information measuring apparatus measures a celestial body. It is a schematic block diagram of the 3D object information measuring apparatus which concerns on the modification of 1st Embodiment of this invention. It is a schematic block diagram of the 3D object information measuring apparatus which concerns on Example 1 of this invention. (A) is a photograph of the LED which is the subject in Example 1, (b) is an enlarged photograph of the LED, and (c) is a photograph of the LED which is lit. (A) is a recorded image acquired by the interference fringe acquisition unit capturing the interference light at once in Example 1, and (b) is four images generated from the recorded image, (c). ) Is a spatial coherence function image obtained from four images. (A) and (b) are reproduced images of amplitude and phase obtained from the spatial coherence function image shown in FIG. 14 (c), respectively. (A) is a schematic configuration diagram of the three-dimensional object information measuring device according to the second embodiment of the present invention, and (b) is a photograph of an amplitude mask. (A) and (b) are an amplitude image and a phase image of the reproduced image focused on the amplitude mask in Example 2, respectively. (A) and (b) are an amplitude image and a phase image of the reproduced image focused on the LED in Example 2, respectively. It is a figure which shows an example of the conventional digital holography apparatus. It is a figure which shows another example of the conventional digital holography apparatus. It is explanatory drawing which shows the principle of the 3D object information measuring apparatus which concerns on 2nd Embodiment of this invention. It is explanatory drawing which shows the principle of obtaining a phase image from four interference images. It is a schematic block diagram of the 3D object information measuring apparatus which concerns on 2nd Embodiment of this invention. It is explanatory drawing of the optical path in the 3D object information measuring apparatus shown in FIG. (A) is a side view showing the configuration of an interference fringe acquisition unit of the three-dimensional object information measuring device, (b) is a plan view of a polarizing element array of the interference fringe acquisition unit, and (c) is a plan view. It is a top view of the image pickup surface of the interference fringe acquisition part. It is a functional block diagram of the computer of the 3D object information measuring apparatus. (A) to (e) are diagrams for explaining the process of obtaining a reproduced image from the recorded image acquired by the interference fringe acquisition unit. It is a schematic block diagram of the 3D object information measuring apparatus which concerns on the modification of the 2nd Embodiment of this invention. It is a schematic block diagram of the 3D object information measuring apparatus which concerns on Example 3 of this invention. (A) and (b) are an amplitude image and a phase image of a virtual light wave in an embodiment, respectively. (A) is a phase image acquired by the interference fringe acquisition unit capturing the interference light at once in Example 3, and (b) is acquired by sequentially imaging the interference light as in the conventional method. It is a phase image.

[First Embodiment: Complex Amplitude Information Measurement]
Hereinafter, the first embodiment of the present invention will be described with reference to the accompanying drawings.
[Principle of measurement]
The present invention obtains complex amplitude information or phase information by dividing an object light arriving from an object into two light with different wavefronts, interfering with each other using a shearing interferometer, and calculating and processing an interference fringe image. 3 It is a dimensional object information measuring device. In the first embodiment, an apparatus for measuring complex amplitude information will be described. As shown in FIG. 1, the Fourier surface created for the subject through a lens is divided into two, the wavefronts are shifted by a method such as enlarging or reducing each of the divided planes, and the wavefronts are superposed to obtain interference light. .. Then, by the phase shift method, a plurality of (preferably three or more) interference fringe images having different phases from each other are recorded from the interference light, and the spatial coherence function of the Fourier plane of the subject is obtained by calculation processing to obtain the spatial coherence function of the subject's three-dimensional structure. Acquire imaging (complex amplitude information). In the first embodiment, an interference image is photographed at one time by an interference fringe acquisition unit, and a plurality of interference fringe images having different phases from each other are constructed from the captured interference images to instantly acquire complex amplitude information of the subject. It is characterized by doing.

When obtaining the spatial coherence function of the Fourier plane of the subject, a plurality of (preferably three or more) interference fringe images having different phases from each other are required. In this embodiment, the plurality of images are acquired at one time. As an acquisition method, there are a method using an image pickup element coupled with a minute polarizing element array and a method using a plurality of (preferably 3 or more) image pickup elements and a polarizing element, but the latter has a problem that the device becomes large and complicated. There is. In the following embodiment, the former method will be described. More specifically, it is shown in FIG. 2 by the spatial division multiplexing used in the parallel digital holography (Patent No. 4294526, Japanese Patent Application No. 2008-031965) invented by the present inventors and capable of high-precision instantaneous three-dimensional measurement. As described above, four interference fringe images are acquired by one imaging (one shot), and arithmetic processing is performed to instantly measure complex amplitude information which is three-dimensional object information.

[Configuration of 3D object information measurement device]
FIG. 3 shows a schematic configuration of the three-dimensional object information measuring device 1 according to the first embodiment. The three-dimensional object information measuring device 1 is a digital holography device that measures three-dimensional structural information (complex amplitude information) of the object 10, and includes a lens 21, a linear polarization conversion unit 22, a circular polarization conversion unit 28, and a shearing interferometer. 2, an interference fringe acquisition unit 3, and a calculation unit 4. The object 10 is a self-luminous object or an object illuminated by natural light or light from a thermal light source.

The lens 21 serves to form a Fourier surface by transmitting the object light coming from the object 10. The linear polarization conversion unit 22 is a polarizing element and passes through the Fourier plane to convert object light into linear polarization.

(Searling interferometer)
The shearing interferometer 2 is a radial shearing interferometer in the present embodiment, and includes a polarization beam splitter (polarization beam splitting element) 23, a lens 24, a lens 25, a mirror 26, and a mirror 27. ..

The polarization beam splitter 23 splits the light incident from the linear polarization conversion unit 22 into two, and splits one of the two divided lights and the same optical path as the one light in the opposite direction. It combines with the other light that is willing to re-incident.

Specifically, as shown in FIG. 4, the light L1 incident from the linear polarization conversion unit 22 is divided into a vertically polarized light L2 and a horizontally polarized light L3. The vertically polarized light L2 and the horizontally polarized light L3 propagate in a common optical path in opposite directions to each other and are coupled again by the polarization beam splitter 23. That is, the vertically polarized L2 (solid line in FIG. 4) re-enters the polarizing beam splitter 23 via the lens 24, the mirror 26, the mirror 27, and the lens 25. On the other hand, the horizontally polarized light L3 (dotted line in FIG. 4) reverses the optical path of the vertically polarized light L2, that is, passes through the lens 25, the mirror 27, the mirror 26 and the lens 24, and is re-incidents into the polarizing beam splitter 23.

At this time, since the lens 24 and the lens 25 have different focal lengths from each other, the vertically polarized light L2 and the horizontally polarized light L3 pass through the lens 24 and the lens 25 in opposite directions, so that one is enlarged and the other is reduced. Will be done. For example, in this embodiment, the focal length of the lens 24 is 200 mm, and the focal length of the lens 25 is 220 mm. Since the vertically polarized light L2 passes through the lens 24 and the lens 25 in this order, the Fourier plane is magnified 220/200 = 1.1 times. On the other hand, since the horizontally polarized L3 passes through the lens 25 and the lens 24 in this order, the Fourier plane is reduced to 200/220 ≈ 0.91 times.

The vertically polarized light L2 and the horizontally polarized light L3 re-entering the polarizing beam splitter 23 are coupled and pass through the circular polarization conversion unit 28 which is a birefringent element, become circularly polarized light in opposite directions to each other, and are output as interference light. The output interference light reaches the interference fringe acquisition unit 3 which is an image pickup device.

The arrow in FIG. 4 corresponds to the optical axis. Therefore, for convenience, the arrow of the vertically polarized light L2 and the arrow of the horizontally polarized light L3 are shown in a staggered manner, but in reality, the arrows are the same.

(Interference fringe acquisition part)
In the present embodiment, the interference fringe acquisition unit 3 is a polarizing element array type image pickup device, and includes a polarizing element array 31, an image pickup surface 32, and a main body 33, as shown in FIG. 5 (a). .. The polarizing element array 31 and the imaging surface 32 are bonded to each other and bonded to the main body 33.

As shown in FIG. 5B, the polarizing element array 31 is formed by arranging four types of polarization regions having different polarization directions and phase shift amounts of incident light in a matrix. The area indicated by the left and right double arrows is the area through which the incident light passes without changing the phase. The region indicated by the upward-sloping double arrow is the region that delays the phase of the incident light by 1/4 wavelength (π / 2 [rad]), and the region indicated by the upper and lower double arrows is the region that delays the phase of the incident light by 1/2 wavelength. It is a region for delaying (π [rad]), and the region indicated by the double arrow rising to the left is a region for delaying the phase of the incident light by 3/4 wavelength (3π / 2 [rad]).

As shown in FIG. 5 (c), the image pickup surface 32 is composed of image pickup elements such as CCDs and CMOS arranged in an array, and has a plurality of pixels, and each pixel is a polarizing element array 31. It is configured to correspond one-to-one with each polarization region shown in FIG. 5 (c). Further, the plurality of pixels are divided into four pixel groups P1 to P4 according to the phase of the incident light. Interference light with no phase delay is incident on the pixel group P1, interference light with a phase delay of 1/4 wavelength (π / 2 [rad]) is incident on the pixel group P2, and interference light with a phase delay of 1/4 wavelength (π / 2 [rad]) is incident on the pixel group P3. , Interference light whose phase is delayed by 1/2 wavelength (π [rad]) is incident, and interference light whose phase is delayed by 3/4 wavelength (3π / 2 [rad]) is incident on the pixel group P4.

With the above configuration, the two light waves incident on the interference fringe acquisition unit 3 that are circularly polarized in opposite directions are recorded as four types of interference fringe images having different polarization directions and phases. The data of the recorded image acquired by the interference fringe acquisition unit 3 in one shooting in this way is transmitted to the calculation unit 4.

(Calculation unit)
The calculation unit 4 is a part that serves to output three-dimensional information (complex amplitude information) of the object 10 from the recorded image acquired by the interference fringe acquisition unit 3 by calculation, and may be configured by, for example, a general-purpose personal computer. can. As shown in FIG. 6, the calculation unit 4 includes an extraction unit 41, an interpolation unit 42, and a calculation unit 43. Each of these parts is a functional block realized by causing the calculation unit 4 to execute the program. In addition, each of the above parts may be realized by hardware.

The process of calculating the three-dimensional information from the recorded image by the calculation unit 4 will be described with reference to FIG. 7. FIG. 7A shows a recorded image acquired by the interference fringe acquisition unit 3. Each pixel constituting the recorded image corresponds to each pixel of the image pickup surface 32 of the interference fringe acquisition unit 3. Specifically, the pixels B1 to B4 shown in different patterns are the pixels acquired by the pixel groups P1 to P4, respectively.

When the data of the recorded image is input to the calculation unit 4, the extraction unit 41 extracts pixels from the recorded image for each phase, and extracts four extraction data consisting of pixels having the same phase and pixels lacking pixel values. Generate. Specifically, as shown in FIG. 7B, only the extraction data D1a in which only the pixel B1 having no phase delay is extracted and the pixel B2 whose phase is delayed by 1/4 wavelength (π / 2 [rad]). Extracted data D2a from which the Extracted data D4a obtained by extracting only B4 is generated. As can be seen from FIG. 3B, in the extracted data D1a to D4a, the pixel values of all 3/4 pixels are missing.

Subsequently, the interpolation unit 42 of the calculation unit 4 generates four interpolation data D1b to D4b as shown in FIG. 7C by performing pixel interpolation for each of the four extracted data D1a to D4a. .. Specifically, the interpolation unit 42 extracts pixels from the recorded image for each phase, and generates four extraction data consisting of pixels having the same phase and pixels lacking pixel values. The interpolation process applicable to the present embodiment is not particularly limited, but for example, linear interpolation (first-order) is performed using the pixel values of the pixels having the same polarization and the same phase around the missing pixels for which the pixel values are to be calculated. Interpolation processing may be performed by calculating the pixel value of the missing pixel by interpolating). Alternatively, the pixel value of the missing pixel may be calculated by interpolating or extrapolating in the second or third order using the pixel values of the pixels having the same polarization and the same phase around the missing pixel. .. By such interpolation processing, the interpolation unit 42 can determine the pixel values of the missing pixels in the extracted data D1a to D4a and generate interpolation data D1b to D4b that are close to interference images having different phases from each other. In FIG. 7 (c), the interfering data D1b is approximated to an interference image having no phase delay, and the interfering data D2b is approximated to an interfering image whose phase is delayed by 1/4 wavelength (π / 2 [rad]). The data D3b is close to an interference image whose phase is delayed by 1/2 wavelength (π [rad]), and the interpolation data D4b is close to an interference image whose phase is delayed by 3/4 wavelength (3π / 2 [rad]). ..

The calculation unit 43 calculates the imaging (complex amplitude information) of the three-dimensional structure of the object 10 by obtaining the spatial coherence function of the Fourier plane of the object 10 from the interpolation data D1b to D4b generated by the interpolation unit 42. Specifically, the arithmetic unit 43 calculates the complex amplitude distribution of the imaging surface from the four interpolated data D1b to D4b by using an algorithm for reconstructing the image of the object 10, and the obtained complex amplitude distribution is obtained. A reproduced image of the object 10 can be obtained based on the above.

In the arithmetic processing of the arithmetic unit 43 in the present embodiment, the complex amplitude of the spatial coherence function is obtained by the phase shift method, and the reproduced image at an arbitrary depth position of the object 10 is acquired by the inverse Fourier transform. In this way, instantaneous 3D imaging is possible. The detailed flow of 3D imaging will be described below.

とすると、下記の式（１）によって、図７（ｄ）に示すような空間コヒーレンスの複素振幅を求める。

得られた空間コヒーレンスの複素振幅
Γ
から下記の式（２）によって任意の奥行ｚでの物体光の複素振幅

を求める。

ここで、ａはレンズによって拡大される倍率、ｆはレンズの焦点距離、λは中心波長を表す。このようにして、図７（ｅ）に示すような再生像（複素振幅情報）が得られる。Interpolated data D1b to D4b for simplification of explanation

Then, the complex amplitude of spatial coherence as shown in FIG. 7 (d) is obtained by the following equation (1).

Complex amplitude Γ of the obtained spatial coherence
From the following equation (2), the complex amplitude of the object light at an arbitrary depth z

Ask for.

Here, a is the magnification magnified by the lens, f is the focal length of the lens, and λ is the center wavelength. In this way, a reproduced image (complex amplitude information) as shown in FIG. 7 (e) can be obtained.

[Characteristics of this embodiment]
The three-dimensional object information measuring device 1 according to the present embodiment acquires a recorded image of interference light by one shooting by using a shearing interferometer, and the calculation unit 4 performs pixel extraction and pixel interpolation from one recorded image. , It is characterized in that a plurality of interpolation data are generated and complex amplitude information of an object is calculated from these interpolation data. The shearing interferometer does not require highly coherent reference light such as a laser light source because it divides the object light coming from the object into two lights and causes them to interfere with each other. Further, since the two lights obtained by dividing the object light pass through a common optical path, optical adjustment is easy, and robustness can be enhanced against external disturbances such as vibration and temperature change.

Further, since the interference fringe acquisition unit 3 acquires the interference fringe image by photographing the interference light at one time, it is possible to measure the complex amplitude information of the structure of the moving object or the object whose shape changes. Further, the polarizing element array type image pickup apparatus exemplified as the interference fringe acquisition unit 3 is commercially available as a polarization imaging camera. As the other elements of the three-dimensional object information measuring device 1, commercially available ones can be used. Therefore, the three-dimensional object information measuring device 1 can be configured with easily available elements.

Further, the three-dimensional object information measuring device 1 according to the present embodiment is characterized in that it can obtain complex amplitude information having an accuracy equal to or higher than the complex amplitude information of an object obtained by conventional sequential imaging. Here, since the plurality of interpolation data are generated by the interpolation processing, they are similar to, but not the same as, the plurality of interference images obtained by the conventional sequential shooting. Therefore, in general, the complex amplitude information obtained based on the interpolated data is expected to be inferior in accuracy to the complex amplitude information obtained based on a plurality of interference images obtained by sequential imaging. In fact, in the device for measuring complex amplitude information by the present invention (International Publication No. 2014/171256), as shown in [Table 1] and [Table 2], from the recorded image of the object obtained by one shooting. The obtained phase accuracy (Examples 1 to 4) was inferior to the phase accuracy (Comparative Examples 1 to 4) obtained from the recorded images of the objects obtained by the sequential imaging.

Further, in the normal interference measurement method using the reference light, it is desirable to interfere the object light of the same size with the reference light, but in the measurement method by radial shearing interference adopted by the present invention, the optical path having the same path is used. Since it is created by the interference of images with different magnifications propagated through the light, it includes an error (shear amount) due to the shear amount.

Therefore, as in the present embodiment, when the complex amplitude information of the object is calculated based on the interpolation data generated by the extraction / interpolation processing from the recorded image acquired by photographing the interference light by the shearing interferometer at one time, shearing is performed. Since it was expected that the error due to the shear amount by the interferometer would further increase and the accuracy of the complex amplitude information would be further reduced, the person skilled in the art could not come up with the present embodiment until the filing of the present application.

However, as a result of research, the present inventor has found for the first time that the error due to the shear amount can be reduced by the extraction / interpolation processing for the recorded image. That is, since the pixel value of the interpolated pixel in the interpolated data in the present embodiment is not an actually measured value but a value calculated by calculation, it can be obtained by actually performing sequential shooting as in the conventional case. Although it may be different from the interference image to be obtained, in the interpolated data, since the pixel value between adjacent pixels does not change suddenly (smoothing), the error reduction effect due to the shear amount is produced, and it is almost the same. It has been found that it is possible to calculate complex amplitude information with an accuracy equal to or higher than that obtained by conventional sequential imaging.

In this way, the inventors of the present invention reduce the error due to the shear amount by the extraction / interpolation processing, contrary to the above-mentioned expectations of the same traders at that time, and are clearer than the conventional imaging of the three-dimensional structure by sequential imaging. For the first time, I found that imaging was possible.

[Modification 1]
The present invention is not limited to the first embodiment, and various modifications can be made. Further, the technical scope of the present invention also includes an embodiment obtained by appropriately combining the technical means disclosed in the above-described embodiment.

For example, in the above embodiment, the self-luminous object is the measurement target, but the measurement target is not limited to the self-luminous object. For example, the three-dimensional object information measuring device 1 shown in FIG. 8 targets the reflecting object 11 illuminated by the light source 5. Further, the three-dimensional object information measuring device 1 shown in FIG. 9 targets the transmitted object 12 illuminated by the light source 5. Further, the three-dimensional object information measuring device 1'shown in FIG. 10 targets the celestial body 13.

The three-dimensional object information measuring device 1'is different from the three-dimensional object information measuring device 1 shown in FIG. 3 in that the lens 21 shown in FIG. 3 is not provided. This is because the object light arriving from a distant object such as the celestial body 13 forms a Fourier plane without going through the lens 21.

Further, the overall configuration is not limited to the above embodiment. The three-dimensional object information measuring device 1 ”shown in FIG. 11 includes a linear polarization conversion unit 22, a lens 21, a 1/2 wave plate 29a, a shearing interferometer 2, a 1/4 wave plate 29b, and interference fringe acquisition. The shearing interferometer 2 includes a polarization beam splitter 23, a lens 24, a lens 25, a mirror 26, and a mirror 27. The shearing interferometer 2 includes a unit 3 and a calculation unit 4. Three-dimensional object information measurement. Compared with the three-dimensional object information measuring device 1 shown in FIG. 3, the device 1 ”swap the positions of the linear polarization conversion unit 22 and the lens 21, and the circular polarization conversion unit 28 has the 1/2 wave plate 29a and the 1/4 wavelength. It differs in that it is replaced with a plate 29b. The object light converted to linear polarization by the linear polarization conversion unit 22 passes through the 1/2 wave plate 29a and the 1/4 wave plate 29b, so that the vertical polarization L2 and the horizontal polarization L3 are circularly polarized in opposite directions. And reaches the interference fringe acquisition unit 3.

Further, in the above embodiment, the three-dimensional object information measuring device using the radial shearing interferometer has been described, but the three-dimensional object information measuring device using other shearing interferometers such as the lateral shearing interferometer and the rotary shearing interferometer has been described. Is also included in the present invention. Even in a three-dimensional object information measurement device using these other shearing interferometers, the error due to the shear amount can be reduced by extraction / interpolation processing, so that clearer imaging than the conventional method by sequential imaging becomes possible. ..

Further, in the above embodiment, the three-dimensional object information measuring device using light has been described, but the device is not limited to light as long as it has wave nature, and has low coherence such as X-rays and electron beams. It goes without saying that a wave source can be used.

Hereinafter, Examples 1 and 2 of the present invention will be described, but the present invention is not limited thereto.

(Experimental conditions)
In the first embodiment, as shown in FIG. 12, a green LED 5a is used as a subject, and a three-dimensional object information measuring device 1 ”shown in FIG. 11 is used as a three-dimensional object information measuring device. In the device 1 ”, the focal distance of the lens 21 was 100 mm, the focal distance of the lens 24 was 200 mm, and the focal distance of the lens 25 was 220 mm. Further, the optical path length from the lens 21 to the lens 24 via the polarizing beam splitter 23 is 100 mm + 200 mm = 300 mm, and the optical path length from the lens 21 to the lens 25 via the polarizing beam splitter 23 is 100 mm + 220 mm = 320 mm, and the lens 24. The optical path length from the lens 26 to the lens 25 via the mirror 27 is 200 mm + 220 mm = 420 mm, and the optical path length from the lens 24 to the interference fringe acquisition unit 3 via the polarization beam splitter 23 is 200 mm, and the lens 25 is polarized. The optical path length to the interference fringe acquisition unit 3 via the beam splitter 23 was 220 mm.

13 (a) is a photograph of the LED 5a which is a subject, FIG. 13 (b) is an enlarged photograph of the LED 5a, and FIG. 13 (c) is a photograph of the lit LED 5a.

(Experimental result)
FIG. 14A shows a recorded image acquired by turning on the LED 5a and having the interference fringe acquisition unit 3 image the interference light at one time. FIG. 14B shows four interference images (interpolation data) generated by extracting and interpolating pixels (pixels having the same phase) having the same interference fringe image information from the recorded image. Further, a spatial coherence function image obtained from these four images using the above equation (1) is shown in FIG. 14 (c).

Further, the amplitude and phase reproduction images (reproduction distance z = 0, number of pixels 60 × 60) obtained from the spatial coherence function image using the above equation (2) are shown in FIGS. 15 (a) and 15 (b). show. From these reproduced images, the reflector, the LED5a chip, and the terminal portion above it could be confirmed.

(Experimental conditions)
In Example 2, as shown in FIG. 16A, a green LED 5a and an amplitude mask 6 are used as subjects, and a three-dimensional object information measuring device 1 ”shown in FIG. 11 is used as a three-dimensional object information measuring device. As shown in FIG. 16B, an “F” -shaped slit is formed in the amplitude mask 6, and the amplitude mask 6 is installed between the LED 5a and the linear polarization conversion unit 22.

(Experimental result)
Similar to the first embodiment, the LED 5a is turned on, the interference fringe acquisition unit 3 records the interference fringe image by one imaging, and the reproduced image is reproduced from the four images generated by extracting and interpolating the interference fringe image. Got 17 (a) and 17 (b) are an amplitude image and a phase image of the reproduced image focused on the amplitude mask 6. 18 (a) and 18 (b) are an amplitude image and a phase image of a reproduced image focused on the LED 5a. In FIG. 18, it can be seen that the LED 5a can be observed only by the light transmitted through the amplitude mask 6.

[Second embodiment: phase information measurement]
Hereinafter, the second embodiment of the present invention will be described with reference to the accompanying drawings.
[Principle of measurement]
The three-dimensional object information (phase information) measuring device according to the second embodiment of the present invention divides the light (measured light wave) that has passed or reflected from the object irradiated with the laser beam into two lights whose wavefronts are deviated. It is an interference measuring device that uses a shearing interferometer that interferes with each other. Generally, in measurement using shearing interference, as shown in FIG. 21, the measured light wave of the subject is divided into two, the wavefronts are shifted by a method such as enlarging or reducing each of the divided parts, and the wavefronts are overlapped. In addition, the interference light is obtained. Then, a plurality of (preferably three or more) interference fringe images (phase difference images) having different phases from each other are recorded from the interference light by the phase shift method, and the phase image of the subject is acquired by the calculation process. In the present embodiment, the interference light from the shearing interferometer is photographed at once by the interference fringe acquisition unit, and a plurality of interference fringe images having different phases from each other are formed from the captured interference images to instantly obtain a phase image of the subject. It is characterized by acquiring.

As a method for acquiring a phase difference image, there are a method using an image pickup element coupled with a minute polarizing element array and a method using a plurality of (preferably 3 or more) image pickup elements and a polarizing element. In the second embodiment below, the former method will be described. More specifically, it is shown in FIG. 22 by spatial division multiplexing using parallel digital holography (Patent No. 4294526, Japanese Patent Application No. 2008-031965) invented by the present inventors and capable of high-precision instantaneous three-dimensional measurement. As described above, four interference fringe images are acquired by one imaging. This makes it possible to acquire a phase image instantaneously (1 shot).

[Configuration of 3D object information measurement device]
FIG. 23 shows a schematic configuration of the three-dimensional object information measuring device 201 according to the second embodiment. The three-dimensional object information measuring device 201 is a device that acquires a phase image of the object 210, and interferes with the laser light source LA, the lens 221, the linear polarization conversion unit 222, the shearing interferometer 202, and the circular polarization conversion unit 228. It includes a stripe acquisition unit 203 and a calculation unit 204. The laser light source LA includes a drive unit LA1 and a laser diode LA2, and emits laser light. The object 210 is a transparent object.

The lens 221 converts the laser light emitted from the laser light source LA into parallel light. When the laser beam is parallel light, the lens 221 may not be provided. The object 210 is transparent and is installed between the lens 221 and the linear polarization conversion unit 222. The linear polarization conversion unit 222 is a polarizing element, and allows light that has passed through the object 10 to pass through and is polarized into linear polarization.

(Searling interferometer)
The shearing interferometer 202 is a radial shearing interferometer in the present embodiment, and includes a polarization beam splitter (polarization beam splitting element) 223, a lens 224, a lens 225, a mirror 226, and a mirror 227. ..

The polarization beam splitter 223 splits the light incident from the linear polarization conversion unit 222 into two, and of the above-mentioned two splits, one of the re-incident light and the same optical path as the one light are directed in opposite directions. It combines with the other light that is willing to re-incident.

Specifically, as shown in FIG. 24, the light L1 incident from the linear polarization conversion unit 222 is divided into a vertically polarized light L2 and a horizontally polarized light L3. The vertically polarized L2 and the horizontally polarized L3 propagate in the common optical path in opposite directions to each other and are coupled again by the polarization beam splitter 223. That is, the vertically polarized L2 (solid line in FIG. 24) re-enters the polarizing beam splitter 223 via the lens 224, the mirror 226, the mirror 227, and the lens 225. On the other hand, the horizontally polarized light L3 (dotted line in FIG. 24) reverses the optical path of the vertically polarized light L2, that is, re-enters the polarizing beam splitter 223 through the lens 225, the mirror 227, the mirror 226 and the lens 224.

At this time, since the lens 224 and the lens 225 have different focal lengths from each other, the vertically polarized light L2 and the horizontally polarized light L3 pass through the lens 224 and the lens 225 in opposite directions, so that one is enlarged and the other is reduced. Will be done. For example, in the second embodiment, the focal length of the lens 224 is 200 mm, and the focal length of the lens 225 is 220 mm. Since the vertically polarized light L2 passes through the lens 224 and the lens 225 in this order, the Fourier plane is magnified 220/200 = 1.1 times. On the other hand, since the horizontally polarized L3 passes through the lens 225 and the lens 224 in this order, the Fourier plane is reduced to 200/220 ≈ 0.91 times.

The vertical polarization L2 and the horizontal polarization L3 re-incidental to the polarization beam splitter 223 are coupled and pass through the circular polarization conversion unit 228. Here, since the refractive index of the circular polarization conversion unit 228 differs depending on the vibration direction of the linear polarization and the propagation speed differs, the position between the orthogonal linear polarization components after passing through the crystal of the circular polarization conversion unit 228. There is a phase difference. Therefore, the coupled vertically polarized light L2 and horizontally polarized light L3 become circularly polarized light in opposite directions to each other, and are output as interference light from the shearing interferometer 202. The output interference light reaches the interference fringe acquisition unit 203.

The arrow in FIG. 24 corresponds to the optical axis. Therefore, for convenience, the arrow of the vertically polarized light L2 and the arrow of the horizontally polarized light L3 are shown in a staggered manner, but in reality, the arrows are the same.

(Interference fringe acquisition part)
In the present embodiment, the interference fringe acquisition unit 203 is a polarizing element array type image pickup device, and includes a polarizing element array 231, an image pickup surface 232, and a main body 233 as shown in FIG. 25 (a). .. The polarizing element array 231 and the imaging surface 232 are bonded to each other and bonded to the main body 233.

As shown in FIG. 25B, the polarizing element array 231 is formed by arranging four types of polarization regions having different polarization directions and phase shift amounts of incident light in a matrix. The area indicated by the left and right double arrows is the area through which the incident light passes without changing the phase. The region indicated by the upward-sloping double arrow is the region that delays the phase of the incident light by 1/4 wavelength (π / 2 [rad]), and the region indicated by the upper and lower double arrows is the region that delays the phase of the incident light by 1/2 wavelength. It is a region for delaying (π [rad]), and the region indicated by the double arrow rising to the left is a region for delaying the phase of the incident light by 3/4 wavelength (3π / 2 [rad]).

As shown in FIG. 25 (c), the imaging surface 232 has a plurality of pixels such as CCDs and CMOS arranged in an array, and each pixel is one-to-one with each polarization region of the polarizing element array 231. It corresponds to. Further, the plurality of pixels are divided into four pixel groups P1 to P4 according to the phase of the incident light. Interference light with no phase delay is incident on the pixel group P1, interference light with a phase delay of 1/4 wavelength (π / 2 [rad]) is incident on the pixel group P2, and interference light with a phase delay of 1/4 wavelength (π / 2 [rad]) is incident on the pixel group P3. , Interference light whose phase is delayed by 1/2 wavelength (π [rad]) is incident, and interference light whose phase is delayed by 3/4 wavelength (3π / 2 [rad]) is incident on the pixel group P4.

With the above configuration, the two light waves that are circularly polarized in opposite directions incident on the interference fringe acquisition unit 203 are recorded as four types of interference fringe images (phase difference images) having different polarization directions and phases. The data of the recorded image acquired by the interference fringe acquisition unit 203 in one shooting in this way is transmitted to the calculation unit 204.

(Calculation unit)
The calculation unit 204 is a device that calculates the phase information of the object 210 from the recorded image acquired by the interference fringe acquisition unit 203, and can be configured by, for example, a general-purpose personal computer. As shown in FIG. 26, the calculation unit 204 includes an extraction unit 241, an interpolation unit 242, and a calculation unit 243. Each of these parts is a functional block realized by causing the calculation unit 204 to execute the program. In addition, each of the above parts may be realized by hardware.

The process of calculating the phase information from the recorded image by the calculation unit 204 will be described with reference to FIG. 27. FIG. 27A shows a recorded image acquired by the interference fringe acquisition unit 203. Each pixel constituting the recorded image corresponds to each pixel of the image pickup surface 232 of the interference fringe acquisition unit 203. Specifically, the pixels B1 to B4 shown in different patterns are the pixels acquired by the pixel groups P1 to P4, respectively.

When the data of the recorded image is input to the calculation unit 204, the extraction unit 41 extracts pixels from the recorded image for each phase, and extracts four extraction data consisting of pixels having the same phase and pixels lacking pixel values. Generate. Specifically, as shown in FIG. 27 (b), only the extraction data D1a in which only the pixel B1 having no phase delay is extracted and the pixel B2 whose phase is delayed by 1/4 wavelength (π / 2 [rad]). Extracted data D2a from which the Extracted data D4a obtained by extracting only B4 is generated. In the extracted data D1a to D4a, the pixel values of all 3/4 pixels are missing.

Subsequently, the interpolation unit 42 of the calculation unit 4 generates four interpolation data D1b to D4b as shown in FIG. 27 (c) by performing pixel interpolation for each of the four extracted data D1a to D4a. .. Specifically, the interpolation unit 242 performs interpolation processing on pixels (referred to as missing pixels) in which the pixel values of the extracted data D1a to D4a are missing. The interpolation process applicable to the present embodiment is not particularly limited, but for example, linear interpolation (first-order) is performed using the pixel values of the pixels having the same polarization and the same phase around the missing pixels for which the pixel values are to be calculated. Interpolation processing may be performed by calculating the pixel value of the missing pixel by interpolating). Alternatively, the pixel value of the missing pixel may be calculated by interpolating or extrapolating in the second or third order using the pixel values of the pixels having the same polarization and the same phase around the missing pixel. .. By such interpolation processing, the interpolation unit 242 can determine the pixel values of the missing pixels in the extracted data D1a to D4a and generate the interpolation data D1b to D4b which are close to the interference images having different phases from each other. In FIG. 27 (c), the interfering data D1b is approximated to an interference image having no phase delay, and the interfering data D2b is approximated to an interfering image whose phase is delayed by 1/4 wavelength (π / 2 [rad]). The data D3b is close to an interference image whose phase is delayed by 1/2 wavelength (π [rad]), and the interpolation data D4b is close to an interference image whose phase is delayed by 3/4 wavelength (3π / 2 [rad]). ..

The calculation unit 243 calculates the phase information of the object 210 from the interpolation data D1b to D4b generated by the interpolation unit 242. Specifically, the calculation unit 243 obtains a phase difference image of two light waves by using a phase shift method, and obtains a phase image by performing a wavefront reconstruction process. As the algorithm for reconstructing the wavefront from the phase contrast image, a method using a Zernike polynomial, a method using a Legendre polynomial, a method of reconstructing with reference to the central part, or the like can be applied.

In the arithmetic processing of the arithmetic unit 243 in the second embodiment, the wavefront reconstruction processing is performed by the method of reconstructing with the central portion as a reference. The algorithm will be described in detail.

となる。この関係式はほかの倍率においても次の式のように成り立つ。

Ｎ回拡大した光波の位相についても、

が成り立つ。ここで，１，２，３…，Ｎ回拡大する式を足し合わせると、次の式が成り立つ。

この式の右辺の第二項は光波を２Ｎ＋１回拡大している波面を表すため、一様とみなせる。つまり、

が成り立つ。記録画像から得られた４枚の干渉縞画像を

とすると，下記の位相シフト法の式によって２つの光波の位相差
ΔＷ（ｘ／ｓ，ｙ／ｓ）
が求まる。

この位相差
ΔＷ（ｘ／ｓ，ｙ／ｓ）
を用いて、上記式から縮小した光波の位相画像
Ｗ（ｘ／ｓ，ｙ／ｓ）
を得る。The phase of the light wave before expanding the vertically polarized light L2 shown in FIG. 24 is W (x, y).
, When the magnification is s, the phase W (x / s, y / s) of the reduced horizontal polarization L3.
Phase W (sx, sy) of the vertically polarized light L2 expanded to
The phase relationship of

Will be. This relational expression holds as follows at other magnifications.

Regarding the phase of the light wave expanded N times,

Is true. Here, by adding the equations that expand 1, 2, 3 ..., N times, the following equation holds.

The second term on the right side of this equation represents the wavefront in which the light wave is expanded 2N + 1 times, so it can be regarded as uniform. in short,

Is true. Four interference fringe images obtained from the recorded image

Then, the phase difference between the two light waves is ΔW (x / s, y / s) according to the following phase shift method equation.
Is sought.

This phase difference ΔW (x / s, y / s)
Phase image W (x / s, y / s) of the light wave reduced from the above equation using
To get.

[Characteristics of this embodiment]
The three-dimensional object information measuring device 201 according to the present embodiment acquires a recorded image of interference light by a shearing interferometer in one shot, and in the calculation unit 204, a plurality of recorded images are extracted from one recorded image and pixel interpolation is performed. It is characterized by generating interpolated data and calculating the phase information of light from an object from these interpolated data. The shearing interferometer does not require highly coherent reference light such as a laser light source because it divides the object light coming from the object into two lights and causes them to interfere with each other. Further, since the two lights obtained by dividing the object light pass through a common optical path, optical adjustment is easy and robustness against external disturbance can be enhanced.

Further, since the interference fringe acquisition unit 203 acquires the interference fringe image by photographing the interference light at one time, it can be applied to the measurement of the phase information of the light from the structure of the moving object or the object whose shape changes. Further, the polarizing element array type image pickup apparatus exemplified as the interference fringe acquisition unit 203 is commercially available as a polarization imaging camera. As the other elements of the three-dimensional object information measuring device 1, commercially available ones can be used. Therefore, the three-dimensional object information measuring device 201 can be configured with easily available elements.

Further, the three-dimensional object information measuring device 201 according to the present embodiment is characterized in that phase information with an accuracy equal to or higher than that obtained by conventional sequential imaging can be obtained. Here, since the plurality of interpolation data are generated by the interpolation processing, they are similar to, but not the same as, the plurality of interference images obtained by the conventional sequential shooting. Therefore, in general, the phase information obtained based on the interpolated data is expected to be inferior in accuracy to the phase information obtained based on a plurality of interference images obtained by sequential imaging. In fact, in the measuring device by the present inventor (International Publication No. 2014/171256), as shown in [Table 1] and [Table 2], the phase obtained from the recorded image of the object obtained by one shooting. The accuracy (Examples 1 to 4) was inferior to the phase accuracy (Comparative Examples 1 to 4) obtained from the recorded images of the objects obtained by the sequential imaging.

Further, in the normal interference measurement method using the reference light, it is desirable to interfere the object light of the same size with the reference light, but in the measurement method by radial shearing interference adopted in this embodiment, the path is the same. Since it is created by the interference of images with different magnifications propagating in the optical path, it includes an error (shear amount) due to the shear amount.

Therefore, as in the present embodiment, the phase information of the light from the object is calculated based on the interpolation data generated by the extraction / interpolation processing from the recorded image acquired by photographing the interference light by the shearing interferometer at one time. It is expected that the error due to the shear amount will further increase and the accuracy of the phase information will further decrease. Therefore, those skilled in the art could not come up with the present embodiment until the filing of the present application.

However, in reality, the present inventor has found that the error due to the shear amount can be reduced by the extraction / interpolation processing for the recorded image. That is, since the pixel value of the interpolated pixel in the interpolated data in the present embodiment is not an actually measured value but a value calculated by calculation, it can be obtained by actually performing sequential shooting as in the conventional case. Although it may be different from the interference image to be obtained, in the interpolated data, since the pixel value between adjacent pixels does not change suddenly (smoothing), the error reduction effect due to the shear amount is produced, and it is almost the same. It is possible to calculate phase information with an accuracy equal to or higher than the phase information obtained by conventional sequential imaging.

As described above, in spite of the above prediction, the present inventors reduce the error due to the shear amount by the extraction / interpolation processing, so that the phase information with higher accuracy than the phase information obtained by the conventional sequential imaging can be obtained. I found for the first time that I could get it.

[Modification 2]
The present invention is not limited to the second embodiment, and various modifications can be made within the scope of the claims. Further, the technical scope of the present invention also includes an embodiment obtained by appropriately combining the technical means disclosed in the above-described embodiment.

For example, in the above embodiment, the transparent object is the measurement target, but the measurement target is not limited to the transparent object. For example, as in the three-dimensional object information measuring device 201'shown in FIG. 28, the reflection object may be the measurement target. good. The three-dimensional object information measuring device 201'is a configuration in which the three-dimensional object information measuring device 201 shown in FIG. 23 is further provided with a beam splitter 229. In the three-dimensional object information measuring device 201', the laser light emitted from the laser light source LA reaches the object 211, which is a reflecting object, via the lens 221 and the beam splitter 229, is reflected by the object 211, and then is linearly polarized. Reach unit 222. When the laser beam is reflected on the surface of the object 211, the phase changes depending on the shape of the object 211.

Hereinafter, Example 3 of the present invention will be described, but the present invention is not limited thereto.

(Simulation conditions)
In Example 3, a computer simulation was performed to confirm the effectiveness of the present invention. In the computer simulation, as shown in FIG. 29, the three-dimensional object information measuring device 201 according to the second embodiment described above was used as the three-dimensional object information measuring device. In the three-dimensional object information measuring device 201, the focal length of the lens 224 was 170 mm, and the focal length of the lens 225 was 175 mm. Further, the optical path length from the object 210 to the lens 224 via the polarizing beam splitter 223 is 170 mm, the optical path length from the lens 221 to the lens 225 via the polarizing beam splitter 223 is 175 mm, and the optical path length from the lens 224 to the mirror 226 and the mirror 226 The optical path length from the lens 224 to the interference fringe acquisition unit 203 via the polarizing beam splitter 223 is 170 mm, and the optical path length from the lens 225 to the polarizing beam splitter 223 is 170 mm + 175 mm = 345 mm. The optical path length to the interference fringe acquisition unit 203 via the beam was 175 mm. As a result, one of the light waves split by the polarizing beam splitter 223 is reduced to 170/175≈0.9714 times, and the other is expanded to 175/170≈1.0294 times.

The object 210, which is the subject, is assumed to be a droplet. 30 (a) and 30 (b) are an amplitude image and a phase image of a virtual light wave of an object 210, respectively. Further, it is assumed that the wavelength of the laser light from the laser light source LA is 532 nm, and the number of pixels of the interference fringe acquisition unit 203 is 300 × 300 pixels. The computer simulation adopted a method of reconstructing the wavefront with reference to the central part in the wavefront reconstruction process.

(simulation result)
The phase image reproduced by the third embodiment is shown in FIG. 31 (a). The correlation coefficient (similarity) of this phase image was 0.9874. Further, FIG. 31 (b) shows a phase image reproduced by a conventional method in which a plurality of phase difference images are acquired by sequential shooting. The correlation coefficient (similarity) of this phase image was 0.9873, which was lower than that of the phase image reproduced by Example 3. From this simulation result, it was found that the three-dimensional object information measuring device according to the second embodiment can reproduce a phase image as clear as or better than the phase information obtained by the conventional sequential imaging.

As described above, according to the present invention, complex amplitude information or phase information of a transparent object or an optical component, which is three-dimensional information of an object that emits fluorescence or an object illuminated by natural light or a light from a thermal light source, can be instantaneously obtained. Allows you to record. Instantly recording complex amplitude information, which is three-dimensional information, is the measurement of the distribution, shape, size, and density of biological microscopes, parts, industrial inspection equipment for products, particles, fluids, etc. for observing and measuring living organisms. Is important in. As a result, the present invention is effective in realizing drug discovery, product inspection equipment, product manufacturing equipment, and the like. In addition, instantly recording phase information, which is three-dimensional information, is an imaging device for pressure changes in gas jets, which is a structural measurement of transparent objects, a thickness distribution / refractive index distribution measuring device for transparent objects / living cells, and lasers. It can be developed as a wavefront measuring device for the emitted light of a high-power laser and a wavefront measuring device for the emitted light of an ultrashort pulse laser, which is a quality inspection of the above. This can greatly contribute to the development of products with high international competitiveness in the manufacturing industry and biotechnology industry, which drive Japan's economy.

1 3D object information measurement device (digital holography device)
1'3D object information measurement device (digital holography device)
1 ”3D object information measurement device (digital holography device)
2 Shearing interferometer 3 Interference fringe acquisition unit (imaging device)
4 Calculation unit (calculator)
5 Light source 5a LED
6 Amplitude mask 10 Object 11 Reflective object 12 Transmitting object 13 Astronomical object 21 Lens 22 Linear polarization converter (polarizer)
23 Polarization beam splitter 24 Lens 25 Lens 26 Mirror 27 Mirror 28 Circular polarization converter (birefringence element)
29a 1/2 wave plate 29b 1/4 wave plate 31 Polarizer array 32 Imaging surface 33 Main body 41 Extraction unit 42 Interpolation unit 43 Calculation unit B1 to B4 Pixels D1a to D4a Extraction data D1b to D4b Interpolation data L2 Vertical polarization L3 Horizontal polarization P1 to P4 pixel group 201 3D object information measurement device (interference measurement device)
201'3D object information measurement device (interference measurement device)
202 Shearing interferometer 203 Interference fringe acquisition unit (imaging device)
204 Calculator (Calculator)
210 Object 211 Object 221 Lens 222 Linear polarization converter (polarizer)
223 Polarization beam splitter 224 Lens 225 Lens 226 Mirror 227 Mirror 228 Circular polarization converter (birefringence element)
229 Beam splitter 231 Polarizer array 232 Imaging surface 233 Main unit 241 Extraction unit 242 Interpolation unit 243 Calculation unit LA Laser light source LA1 Drive unit LA2 Laser diode

Claims (6)

A linear polarization converter that converts object light coming from an object into linear polarization,
A shearing interferometer that causes shearing interference of the object light converted to linear polarization, and
A circular polarization conversion unit that converts the vertical polarization and horizontal polarization of the interference light by the shearing interferometer into circular polarization, and
The interference fringe acquisition unit that records the circular polarization by one shooting, and
A calculation unit that calculates complex amplitude information of the object from the recorded image of the interference fringe acquisition unit,
It is a three-dimensional object information measuring device equipped with
In the recorded image, the phase differs depending on the pixel, and the phase is different.
The calculation unit
An extraction unit that extracts pixels from the recorded image for each phase and generates a plurality of extraction data consisting of pixels having the same phase and pixels lacking pixel values.
An interpolation unit that generates a plurality of interpolation data that approximates a plurality of interference images having different phases by performing pixel interpolation for each of the plurality of extracted data.
An arithmetic unit that calculates complex amplitude information or phase images from the plurality of interpolated data,
A three-dimensional object information measuring device characterized by being equipped with. The three-dimensional object information measuring device according to claim 1, wherein the shearing interferometer is a radial shearing interferometer. The radial shearing interferometer
The light incident from the linear polarization conversion unit is divided into two, and one of the two divided lights is re-incidented and the other is re-incidented in the same optical path as the one light in the opposite direction. Polarized beam splitting element that combines with the light of
Two lenses arranged in the optical path with different focal lengths and
Equipped with
The three-dimensional object information measuring device according to claim 2, wherein the light coupled by the polarized beam dividing element is output as the interference light. The interference fringe acquisition unit is
A polarizing element array having a plurality of types of polarization regions in which the polarization direction and the phase shift amount of the incident light are different from each other,
An image sensor coupled to the polarizing element array and having pixels having a one-to-one correspondence with each of the polarization regions.
The three-dimensional object information measuring device according to claim 1, further comprising a polarizing element array type image pickup device. The object light is Fourier transformed light.
The shearing interferometer causes the Fourier planes of the object light to interfere with each other.
The interference fringe acquisition unit records the interference fringes of the circular polarization, and records the interference fringes.
The calculation unit is characterized in that the complex amplitude of the spatial coherence function is obtained from the plurality of interpolation data by using a phase shift method, and the complex amplitude information is calculated by performing an inverse Fourier transform. The three-dimensional object information measuring device according to any one of 4. The object light is light that the coherent light reflects or passes through the object.
The shearing interferometer causes the object lights to interfere with each other.
The interference fringe acquisition unit records the interference fringes of the circular polarization, and records the interference fringes.
The arithmetic unit obtains a phase contrast image of the interference light from the plurality of interpolated data by using a phase shift method, and reconstructs the phase contrast image with reference to a Zernike polynomial, a Legendre polynomial, or a central portion. The three-dimensional object information measuring apparatus according to any one of claims 1 to 4, wherein the phase image is calculated by reconstructing the wavefront by applying the method.

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