WO2013047709A1

WO2013047709A1 - Digital holography method and digital holography device

Info

Publication number: WO2013047709A1
Application number: PCT/JP2012/074987
Authority: WO
Inventors: 司松尾
Original assignee: ウシオ電機株式会社
Priority date: 2011-09-30
Filing date: 2012-09-27
Publication date: 2013-04-04
Also published as: JPWO2013047709A1; WO2013047709A4; JP2016027407A; JP5888334B2; JP6079839B2

Abstract

[Problem] To provide a practical digital holography method and digital holography device having both a reflection mode and a transmission mode, and to enable the acquisition of high-precision holographic data without necessitating that the subject be made to float in mid-air. [Solution] Diffracted light from a subject (S), which is obtained by irradiating the subject (S) with light from a light source (1), and reference light, which does not include information about the subject, are made to interfere with each other on the imaging surface of an imaging element (2) to acquire hologram data. In the reflection mode, the subject (S) is irradiated with light from a first side by means of a reflection-diffraction light guiding system (31), while in the transmission mode, the subject (S) is irradiated with light from a second side, which is the opposite side from the first side, by means of a transmission-diffraction light guiding system (32). The reflection mode and the transmission mode are selected alternatively by a optical element that serves as a selector.

Description

Digital holography method and digital holography apparatus

The present invention relates to a digital holography capable of obtaining three-dimensional information of an object in real time by using light interference.

There is a need for a technique capable of recording and detecting three-dimensional information necessary for detection of defects such as chipping, dents, bulges, warping, and the like that are difficult to detect by conventional two-dimensional image processing and measurement of mechanical vibration. . Furthermore, there is a need to acquire three-dimensional information in real time for moving objects such as living cells. There is holography as a technique that can record and detect such three-dimensional information. Conventionally, a process of recording three-dimensional information on a high-resolution photographic plate and developing / reproducing it is required. It takes a long time from recording to reproduction, and it is difficult to obtain three-dimensional information of a moving object. It was.

In recent years, digital holography has been proposed that enables high-speed measurement by introducing advances in electronics technology such as higher computer speeds, larger storage capacities, and higher resolution and higher pixel imaging devices such as CCDs. ing. In this technique, an interference fringe is imaged by an image sensor, and a numerical calculation process based on a light diffraction phenomenon is performed on the image data of the interference fringe by a computer, thereby reproducing a three-dimensional image of the object on the computer. It is.
In digital holography, 1) development processing is not required, and a reproduced image can be obtained at the shooting site. 2) a reproduced image can be obtained on an arbitrary surface with one interference fringe image data. 3) hologram data (of interference fringes) Image data) can be easily transmitted and copied. Taking advantage of these advantages, research aimed at three-dimensional measurement of solids, fluids, living cells, mechanical vibrations, and the like using digital holography technology has been actively conducted.

FIG. 16 is a diagram showing an outline of a conventional digital holography device. In this digital holography device, light emitted from a light source 71 is split by a half mirror 72 into reference light and light for object irradiation. The object irradiation light divided by the half mirror 72 is applied to the object 74 through the reflection mirror 73, and the object light 75 is emitted from the object 74. The object light 75 enters the beam splitter 76. On the other hand, the reference light divided by the half mirror 72 is reflected by the reflection mirror 77 and enters the beam splitter 76.
Then, the object light transmitted through the beam splitter 76 and the reference light reflected by the beam splitter 76 are simultaneously incident on the imaging surface of the CCD camera 78, so that interference fringes generated by superimposing the object light and the reference light are imaged. Then, hologram data is obtained. A reconstructed image of the object 74 is obtained by performing calculation processing such as Fresnel transformation on the obtained hologram data by a computer (not shown).

Note that object light is light emitted from an object irradiated with light, and means diffraction light emitted from an object because holography uses a diffraction phenomenon. The apparatus shown in FIG. 16 is an apparatus in a transmission mode, and the transmitted diffracted light is object light. The transmission mode is a mode in which an interference fringe between diffracted light (transmitted diffracted light) transmitted through the object and emitted when the object is irradiated with light and the reference light is imaged.
In holography, a plane wave is generally used for reasons such as increasing the coherence between object light and reference light. The same applies to digital holography, and a light source that emits a plane wave such as a laser is used.

Many of the conventional digital holography devices are in-line devices, and take hologram data into consideration by making the reference light incident perpendicular to the imaging surface in the same way as the object light in consideration of the resolution limit of the image sensor. Yes. For this reason, the reproduced image obtained by calculating the hologram data is overlapped with a zero-order image or a conjugate image, making it difficult to obtain a clear reproduced image.
Therefore, a digital holography device using a phase shift interferometry has been proposed. The phase shift interferometry is a two-beam interferometer in which a piezoelectric element such as a piezo element or an element capable of changing an optical path length such as a spatial light modulator (SLM) is arranged in the optical path of reference light. In this method, the hologram data is obtained while changing the phase of the reference light in, for example, three or more stages. In a digital holography apparatus using such a phase shift interferometry, a clear image can be obtained by removing the 0th-order light and the conjugate image, and high-precision measurement is possible.
However, the phase shift interferometry cannot be applied to a moving object because it captures interference fringes while sequentially changing the phase of the reference light with a piezoelectric element or the like.
Patent Document 1 (Japanese Patent No. 4294526) discloses an element that converts reference light into reference light groups having different phase values and emits the light, and a Mach-Zehnder interferometer that forms an image in a transmission mode using the element. A constructed digital holography device is shown. As described in this document, the dynamic shape can be measured even when a single image is captured by spatially dividing and recording the interference state between the object beam and the reference beam.

Further, Patent Document 2 (Japanese Patent Publication No. 2002-526815) discloses a method of applying a principle of off-axis digital holography, taking a single interference fringe image, and obtaining an amplitude image and a phase image of the object therefrom. It is disclosed. Even with this method, since it is sufficient to capture a single image, the shape can be measured even when the object is moving (dynamic shape can be measured).
This document shows a digital holography device composed of a Michelson interferometer that is basically designed to form an image in reflection mode. The reflection mode is a mode in which diffracted light (reflected diffracted light) reflected and emitted from an object when the object is irradiated with light is incident on the imaging surface of the image sensor as object light and interferes with reference light.

As shown in FIG. 2B, the light emitted from the light source is spread in the diameter direction and enters the beam splitter. The light incident on the beam splitter is divided into one light that passes through the beam splitter and the other light that is reflected by the beam splitter. One light is reflected by the tilted mirror, then enters the beam splitter, is reflected by the beam splitter, and is imaged as reference light. The other light is applied to the sample through the objective lens, and is reflected by the sample to become object light. This object light is incident on the beam splitter and is transmitted through the beam splitter to be imaged. An off-axis hologram can be recorded by using the tilted mirror and causing the reference light to interfere with the object light at a predetermined angle.

Also, this document shows a digital holography device composed of a Mach-Zehnder interferometer that is basically designed to form an image in a transmission mode. As shown in FIG. 2C of the same document, the light emitted from the light source is spread in the diameter direction and enters the beam splitter. This light is divided into one light transmitted through the beam splitter and the other light reflected by the beam splitter. One light enters the sample, passes through the sample, and forms object light. The object light is collected by the objective lens, enters the beam splitter, is reflected by the beam splitter, and is imaged. On the other hand, the other light is expanded in beam diameter, reflected by an inclined mirror, and then transmitted through a beam splitter and imaged as reference light.

Japanese Patent No. 4294526 Special Table 2002-526815 WO2008 / 123408 publication

As described above, digital holography is expected to be applied to observation of various objects and three-dimensional measurement, but there are various objects to be observed and measured. Therefore, there are objects suitable for reflection mode digital holography and those suitable for transmission mode digital holography. In some cases, it is better to perform both the reflection mode and the transmission mode for one object.
However, as seen in Patent Document 2, there are only conventional digital holography devices that can operate only in the reflection mode and devices that can operate only in the transmission mode. There was no digital holography device that could be operated on. Therefore, in order to perform both the reflection mode and the transmission mode for one object, it is necessary to prepare both the reflection mode device and the transmission mode device.

Patent Document 3 (WO 2008/123408) is known as the only device that can perform both the reflection mode and the transmission mode. FIG. 17 is a diagram showing a digital holography device disclosed in Patent Document 3. As shown in FIG. As shown in FIG. 17, Patent Document 3 discloses a first optical system 110 that irradiates light to an object 119, a second optical system that guides diffracted light and reference light emitted from the object 119 to an imaging device, and A digital holography apparatus including: an imaging device 165 that captures an interference image between the diffracted light and the reference light; and a processing device 201 that generates a three-dimensional image of the object from the interference image for each irradiation direction acquired by the imaging device 165 Is disclosed. The imaging device 165 is provided with an imaging device for transmitted diffracted light and an imaging device for reflected diffracted light separately, and hologram data is individually acquired by the imaging device for transmitted diffracted light and the imaging device for reflected diffracted light.

However, the digital holography device disclosed in Patent Document 3 has the following problems.
FIG. 18 is a schematic diagram showing problems of the digital holography device of Patent Document 3. As shown in FIG. 18 (1), in the digital holography device of Patent Document 3, the side on which the object 119 is irradiated with light (plane wave) to obtain diffracted light is limited to one side of the object 119. This is a device that can irradiate light only from one side of the object 119, and diffracted light (reflected diffracted light) reflected from one side by irradiating light from one side is one 117 of the first objective lens. The diffracted light (transmitted diffracted light) transmitted to the other side is made to reach the transmitted diffracted light imaging device via the other 121 of the first objective lens. As described above, the reason why the light is irradiated only from one side of the object 119 is considered to be because the interference fringes by the reflected diffracted light and the interference fringes by the transmitted diffracted light are simultaneously imaged.

As far as can be understood from FIG. 17, it must be considered that the object is in a state of floating in the air. However, in reality, light is irradiated with an object placed on something like a container or a table, and hologram data is acquired. For example, as shown in FIG. 18B, in consideration of translucency, the object S is placed on a transparent glass petri dish 81 and irradiated with light.
In this case, there is no problem with the transmitted diffracted light, but the reflected diffracted light is captured through the petri dish 81 with respect to the reflected diffracted light. For this reason, spherical aberration occurs due to the influence of the thickness and refractive index of the petri dish 81. FIG. 18B shows a state in which transmitted diffracted light propagates in a state different from the original state depending on the thickness and refractive index of the petri dish 81. Due to such spherical aberration, the apparatus of Patent Document 3 cannot obtain highly accurate hologram data. If the object can be held in the air, it may be possible to prevent problems, but it is not possible when observing minute objects such as bacteria, and soft. In the case of a thin object, if it is held between both sides, it will be deformed or damaged, so it is often impossible.

In the configuration of Patent Document 3, as described above, the viewpoint in the reflection mode and the viewpoint in the transmission mode differ by 180 °. Therefore, the object cannot be observed in the reflection mode or the transmission mode from the same viewpoint. When it is necessary to observe an object in both the reflection mode and the transmission mode from the viewpoint on the same side for some reason, the apparatus of Patent Document 3 cannot be used.
As described above, it is difficult to say that the device of Patent Document 3 is a practical device for obtaining highly accurate hologram data.

In order to obtain hologram data with high accuracy, it is desirable to place a spatial filter on the optical path of the laser beam irradiated to the object. FIG. 19 is a schematic diagram of a spatial filter.
As shown in FIG. 19, the spatial filter includes a lens 82 and a pinhole plate 83, and the pinhole of the pinhole plate 83 is disposed at the light condensing position of the lens 82, so that dust and scratches on the optical element can be obtained. The noise generated by the above is removed. For example, if dust is attached or scratched on the mirror surface that reflects light, the wave surface may be disturbed by the scratch or dust, or interference fringes may be generated due to the effect of the scratch or dust. It becomes impossible to obtain hologram data with high accuracy only by interference fringes due to light. In order to prevent this problem, it is desirable to use a spatial filter.

It is desirable that the spatial filter is disposed as close to the object as possible in the optical path of the light applied to the object. If a spatial filter is arranged on the optical path away from the object, and if an optical element such as a lens or a mirror is further arranged between the spatial filter and the object, dust or dirt on the surface of these optical elements will be removed. The effect of scratches cannot be removed.
Here, in FIG. 17 (Patent Document 3), it is conceivable to arrange a spatial filter on the optical path close to the object 119, for example, between the mirror 115 and the object 119. However, this place is also on the optical path of the reflected diffracted light reflected from the object 119. If the spatial filter is disposed here, the reflected diffracted light cannot pass through the pinhole of the spatial filter, and thus there is a problem that the reflected diffracted light cannot be imaged by the imaging device 165.

In FIG. 17, in order to avoid the above problem, the spatial filter must be separated to the position where the optical path of the irradiation light and the optical path of the reflected diffracted light are separated. Even if the position closest to the object 119 is selected, the position is between the mirror 105 and the beam splitter 107. Even if the spatial filter is arranged at this position, the optical elements such as the beam splitter 107, the second objective lens 109, the polarization beam splitter 111, and the mirror 115 exist from here to the object 119. Therefore, there is no point in arranging a spatial filter. That is, it is practically impossible with the apparatus of Patent Document 3 to obtain highly accurate hologram data using a spatial filter.

The present invention has been made to solve such problems, and firstly, it is an object of the present invention to provide a practical digital holography method for performing both the reflection mode and the transmission mode. .
A second object of the present invention is to provide a practical digital holography device capable of performing both the reflection mode and the transmission mode.
A third object of the present invention is to make it possible to acquire highly accurate hologram data without placing an object in the air.
A fourth object of the present invention is to make it possible to acquire hologram data with higher accuracy by using a spatial filter.

In order to solve the above-described problem, the invention according to claim 1 of the present application passes the object through the object with the diffracted light from the object obtained by irradiating the object with the light emitted from the light source and the light emitted from the light source. A digital holography method for acquiring hologram data by causing interference on the imaging surface of an imaging device with reference light obtained by guiding without any problem,
When the object from the first side is irradiated with the light from the light source, the reflected diffracted light reflected from the object to the first side and emitted is interfered with the reference light on the image pickup surface of the image pickup device to obtain hologram data. Performing a reflection mode to
When the light from the light source is irradiated on the object from the second side opposite to the first side, the transmitted diffracted light that is transmitted through and emitted from the first side and the reference light are reflected on the imaging surface of the image sensor. And performing a transmission mode of acquiring hologram data by causing interference,
The step of performing the reflection mode and the step of performing the transmission mode are alternatively selected and performed in different time zones.
In order to solve the above problem, the invention described in claim 2 does not include object information from diffracted light from an object obtained by irradiating an object with light emitted from a light source and diffracted light from the object. A digital holography method for acquiring hologram data by causing interference with an imaging surface of an imaging device with reference light extracted in a state,
When the object from the first side is irradiated with the light from the light source, the reflected diffracted light reflected from the object to the first side and emitted is interfered with the reference light on the image pickup surface of the image pickup device to obtain hologram data. Performing a reflection mode to
When the light from the light source is irradiated on the object from the second side opposite to the first side, the transmitted diffracted light that is transmitted through and emitted from the first side and the reference light are reflected on the imaging surface of the image sensor. And performing a transmission mode of acquiring hologram data by causing interference,
The step of performing the reflection mode and the step of performing the transmission mode are alternatively selected and performed in different time zones.
In order to solve the above problem, the invention described in claim 3 is such that the diffracted light from the object obtained by irradiating the object with the light emitted from the light source and the light emitted from the light source through the object. A digital holography device that obtains hologram data by causing interference on the imaging surface of the imaging device with reference light obtained by guiding without
A light guide system for reflected diffracted light that guides light from the light source to the object in order to obtain reflected diffracted light that is diffracted light that is reflected and emitted from the object;
A light guide system for transmitted diffracted light that guides light from the light source to the object in order to obtain transmitted diffracted light that is diffracted light that is transmitted through and emitted from the object;
An imaging device in which the imaging surface is located at a position where the reflected diffracted light can be incident and at which the transmitted diffracted light can be incident;
A reference light guide system that guides light from the light source to the imaging surface of the image sensor without passing through an object,
There is provided a selection optical element for selectively selecting whether to enter the reflection mode by entering the reflected diffracted light on the imaging surface of the image sensor or to enter the transmission mode by entering the transmitted diffracted light.
The light guide system for reflected diffracted light irradiates light from the light source to the object from the first side,
The light guide system for transmitted diffracted light irradiates the object with light from the light source from a second side opposite to the first side,
An imaging optical path, which is an optical path from the object to the imaging surface of the imaging element, is set on the first side of the object.
In order to solve the above problem, the invention described in claim 4 does not include object information from diffracted light from an object obtained by irradiating an object with light emitted from a light source and diffracted light from the object. A digital holography device for acquiring hologram data by causing interference with an imaging surface of an imaging element with reference light extracted in a state,
A light guide system for reflected diffracted light that guides light from the light source to the object in order to obtain reflected diffracted light that is diffracted light that is reflected and emitted from the object;
A light guide system for transmitted diffracted light that guides light from the light source to the object in order to obtain transmitted diffracted light that is diffracted light that is transmitted through and emitted from the object;
An imaging device in which the imaging surface is located at a position where the reflected diffracted light can be incident and at which the transmitted diffracted light can be incident;
A reference light guide system that extracts reference light from reflected diffracted light or transmitted diffracted light without including object information and guides it to the imaging surface of the image sensor,
There is provided a selection optical element for selectively selecting whether to enter the reflection mode by entering the reflected diffracted light on the imaging surface of the image sensor or to enter the transmission mode by entering the transmitted diffracted light.
The light guide system for reflected diffracted light irradiates light from the light source to the object from the first side,
The light guide system for transmitted diffracted light irradiates the object with light from the light source from a second side opposite to the first side,
An imaging optical path, which is an optical path from the object to the imaging surface of the imaging element, is set on the first side of the object.
In order to solve the above problem, the invention described in claim 5 has a configuration in which, in the configuration of claim 3 or 4, an imaging optical system including a lens is provided on the imaging optical path.
In order to solve the above problem, the invention according to claim 6 is the configuration according to

claim

3, 4 or 5, wherein the imaging optical system includes at least a part of the optical elements in the reflection mode and the transmission mode. Are shared.
In order to solve the above problem, the invention described in claim 7 has a configuration in which, in the configuration of

claim

3, 4, 5 or 6, the imaging optical system is a telecentric optical system.
In order to solve the above problem, the invention according to claim 8 is the structure according to any one of claims 3 to 7, wherein the imaging optical path extends straight from the object to the imaging surface. Have.
In order to solve the above-mentioned problem, according to a ninth aspect of the present invention, in the configuration according to any of the third to eighth aspects, the light guide system for reflected diffracted light guides light to the object through the imaging optical path. A first spatial filter is provided on the optical path until reaching the imaging optical path, and zero or only one is provided on the optical path from the first spatial filter to the imaging optical path. Equipped with a mirror,
The light guide system for transmitted diffracted light includes a second spatial filter, and includes zero or only one mirror on the optical path from the second spatial filter to the object. It has a configuration.
In order to solve the above-described problem, the invention according to claim 10 is the configuration according to any one of claims 3 to 9, wherein the selection optical element is a first optical element disposed on a main optical path extending from the light source. A selection optical element, and a main optical path is branched into an optical path of the reflected diffracted light guide system and an optical path of the transmitted diffracted light guide system, and the first selection optical element is: A configuration that selectively selects whether the light from the light source travels along the optical path of the reflected diffracted light guide system or the optical path of the transmitted diffracted light guide system Have
In order to solve the above-described problem, the invention according to claim 11 is the structure according to any one of claims 3 to 10, wherein a first beam splitter is provided on the imaging optical path, and the reflected diffracted light is provided. The light guide system guides light from the light source to the first beam splitter, and the first beam splitter splits the light guided by the reflected diffracted light guide system in the reflection mode. The first state where one of them is directed to the object.
In order to solve the above-mentioned problems, the invention according to claim 12 is the main optical path extending from the light source as the selection optical element in the configuration of

claim

3, 5, 6, 7, 8, or 9. And a main optical path is branched into an optical path of the reflected diffracted light guide system and an optical path of the transmitted diffracted light guide system. The optical element for selection alternatively selects whether the light from the light source travels along the optical path of the light guide system for reflected diffracted light or the light path of the light guide system for transmitted diffracted light Is what
A first beam splitter is provided on the imaging optical path, the light guide system for reflected diffracted light guides light from a light source to the first beam splitter, and the first beam splitter is Taking a first state in which the light guided by the light guide system for reflected diffracted light in the reflection mode is divided and one of the lights is directed to the object;
The reference light guide system guides the other light divided by the first beam splitter in the reflection mode to the imaging surface of the imaging element without passing through the object,
The first optical element for selection is a second beam splitter, and is provided with a drive unit for changing the arrangement position of the second beam splitter, and the drive unit is a second beam splitter in the reflection mode. In order to prevent light from traveling to the optical path of the transmission diffracted light guide system, the second beam splitter is arranged on the main optical path in the transmission mode. A part of the light is allowed to travel along an optical path of the light guide system for transmitted diffraction light,
The first beam splitter is arranged as a second optical element for selection, and the first beam splitter is provided with a switching unit for changing the state of the first beam splitter,
The switching unit sets the first beam splitter to the first state in the reflection mode, and sets the first beam splitter to the second state in the transmission mode. The second state is guided by the reflected diffracted light guiding system and reaches the first beam splitter so that the reflected diffracted light guiding system is also used as the reference light guiding system. The light is incident on the imaging surface of the image sensor without passing through the object.
In order to solve the above-described problem, the invention according to claim 13 is the configuration according to claim 12, wherein the reference light guide system transmits the other light transmitted through the first beam splitter in the reflection mode. Returns the other light to the first beam splitter so as to enter the imaging surface of the imaging device via the first beam splitter,
A beam stopper that can be disposed on an optical path for returning the other light to the first beam splitter, and a stopper driving unit that drives the beam stopper are provided. In some cases, the beam stopper is not disposed on the optical path, and in the transmission mode, the beam stopper is disposed on the optical path.
In order to solve the above problem, according to a fourteenth aspect of the present invention, in the configuration according to the third to twelfth aspects, the reference light guide system has the reflected diffracted light or the incident light incident on the imaging surface of the imaging element. An off-axis optical element is provided that allows reference light to enter the imaging surface of the imaging element in a state where a predetermined angle is given to the direction of the transmitted diffracted light.
In order to solve the above-mentioned problem, the invention according to claim 15 is directed to the direction of the reflected diffracted light or transmitted diffracted light when entering the imaging surface of the image sensor in the configuration of claim 13. An off-axis optical element is provided that makes reference light incident on the imaging surface of the imaging element in a state where a predetermined angle is given,
The off-axis optical element includes a first off-axis mirror provided on the optical path in front of the first beam splitter by the reflected diffracted light guiding system, and the reference light guiding system configured to transmit the other light. A second off-axis mirror provided on the optical path when returning to the first beam splitter;
The first off-axis mirror is provided with a drive unit. The drive unit sets the first off-axis mirror in the first posture in the reflection mode and the first off-axis mirror in the transmission mode. The off-axis mirror is in the second position,
The first posture is a posture in which the predetermined angle is not given by the first off-axis mirror, and the second posture is a posture in which the predetermined angle is given by the first off-axis mirror. It has a configuration that there is.
In order to solve the above-mentioned problem, in the invention of claim 16, in the structure of claim 15, the optical path is traced in the direction opposite to the traveling direction of light from the first beam splitter toward the light source. The first off-axis mirror is the first mirror;
When the reference light guide system traces the light from the first beam splitter in the direction opposite to the traveling direction on the optical path for returning the other light to the first beam splitter, the second off-axis mirror is The first mirror is configured.

As described below, according to the invention described in

claim

1 or 2 of the present application, since hologram data can be obtained for each object using reflected diffracted light and transmitted diffracted light, the state and shape of the object are examined in detail. It will be suitable for. At this time, since the reflection mode and the transmission mode are performed separately in time, the configuration of the optical system is simplified. According to the first aspect of the present invention, since the reference light is guided to the image sensor without passing through the object, stable reference light can always be obtained regardless of the condition of the object. For this reason, highly accurate hologram data can be acquired.
Further, according to the invention described in claim 3 or 4, since hologram data can be obtained for each object using reflected diffracted light and transmitted diffracted light, it is suitable for examining the state and shape of the object in detail. It will be a thing. At this time, since the reflection mode and the transmission mode are performed separately in time, the configuration of the optical system is simplified. In addition, since the reflection mode and the transmission mode can be performed by one apparatus, it is preferable in terms of workability in addition to the merit in cost. Furthermore, highly accurate hologram data can be obtained even when an object is placed on a transparent container, and observation in the reflection mode and observation in the transmission mode can be performed from the same viewpoint. According to the third aspect of the invention, since the reference light is guided to the image sensor without passing through the object, stable reference light can always be obtained regardless of the condition of the object. For this reason, highly accurate hologram data can be acquired.
According to the invention described in claim 6, in addition to the above effect, since the imaging optical system shares at least a part of the optical elements, the configuration of the optical system is simplified and the cost is reduced.
According to the seventh aspect of the invention, in addition to the above effect, since the imaging optical system is a telecentric optical system, it is possible to irradiate the object with plane waves in both the reflection mode and the transmission mode. For this reason, the object light is not distorted and correction calculation is not required.
According to the invention of claim 8, in addition to the above effect, the imaging optical path extends straight from the object to the imaging surface, so that the configuration of the optical system is simplified, and the wave front is disturbed. Less. For this reason, it can contribute to acquisition of hologram data with higher accuracy, and the cost is also low.
According to the ninth aspect of the invention, in addition to the above effect, since a spatial filter is used, more accurate hologram data can be obtained. Since the spatial filter is located on the optical path closer to the object, the effect of improving accuracy is higher.
According to the invention of claim 12, in addition to the above effect, the reflected diffracted light guiding system is also used as the reference light guiding system, so that the coherence of light is improved and more accurate in this respect. High hologram data can be acquired.
According to the thirteenth aspect of the invention, in addition to the above effect, the reference light guide system returns light to the first beam splitter and passes the light to the image sensor through the first beam splitter in the reflection mode. Therefore, the coherence of light is further improved in this respect, and more accurate hologram data can be acquired.
According to the invention of claim 14 or 15, in addition to the above effect, an off-axis operation is possible because the off-axis optical element is provided. Therefore, image reproduction can be performed with the true image separated from the zero-order image and the conjugate image.
According to the sixteenth aspect of the present invention, since the off-axis mirror is provided near the image pickup device, the incident position of the reference light on the image pickup surface of the image pickup device is not greatly shifted.

It is the figure which showed notionally the digital holography method which concerns on embodiment of this invention. 1 is a schematic front view of a digital holography device according to a first embodiment of the present invention. It is the front schematic of the digital holography device of the 2nd Embodiment of this invention. FIG. 6 is a schematic diagram showing a second beam expander 321 and a second spatial filter 326. It is the schematic which showed typically about the telecentricity of the imaging optical system 5 in the apparatus of FIG. It is the schematic which showed the control system of the digital holography apparatus of 2nd Embodiment. It is the schematic shown about operation | movement of the apparatus of 2nd Embodiment, and is the figure shown by contrasting about the advancing condition of each light in reflection mode and transmission mode. It is the figure which showed the outline of the operation | movement flow in reflection mode. It is the figure which showed the outline of the operation | movement flow in transparent mode. It is the schematic which showed the effect that the apparatus of 2nd Embodiment is equipped with the telecentric imaging optical system. It is a front schematic diagram of a digital holography device according to a third embodiment of the present invention. It is the figure which showed the change of the arrangement angle of the mirror for off-axis used in 3rd Embodiment. It is the schematic shown about operation | movement of the apparatus of 3rd Embodiment, and is the figure shown by contrasting about the advancing condition of each light in reflection mode and transmission mode. It is the front schematic of the digital holography device of the 4th Embodiment of this invention. It is the front schematic which showed the example of the reference light extraction unit 9 in embodiment shown in FIG. It is the figure which showed the outline of the conventional digital holography apparatus. It is a figure which shows the digital holography apparatus disclosed by patent document 3. FIG. It is the schematic shown about the problem of the digital holography apparatus of patent document 3. FIG. It is the schematic of a spatial filter.

Next, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described.
FIG. 1 is a diagram conceptually illustrating a digital holography method according to an embodiment of the present invention. In the digital holography method according to the embodiment, diffracted light (object light) from the object S obtained by irradiating the object S with light (plane wave) emitted from the light source 1 and light from the light source 1 are transmitted to the object S. This is a method of acquiring hologram data by causing interference between the reference light obtained without passing through the imaging surface of the imaging device 2.

One of the major feature points of this method is that the object light (reflected diffracted light) that travels as a diffraction reflected from the object S out of the light irradiated to the object S interferes with the reference light on the imaging surface to generate a hologram. Hologram data is obtained by causing the imaging surface to interfere with the reflection mode for obtaining data and the object light (transmitted diffracted light) that travels as diffracted light through the object S among the light irradiated to the object S and the reference light. The transmission mode is a method in which the reflection mode and the transmission mode are performed in separate steps. FIG. 1 (1) shows the reflection mode, and FIG. 1 (2) shows the transmission mode.
Either the reflection mode step or the transmission mode step may be first. In short, there are a step of obtaining hologram data using reflected diffracted light without using transmitted diffracted light, and a step of obtaining hologram data using transmitted diffracted light without using reflected diffracted light. Are performed at different times rather than simultaneously.

Another major feature of the digital holography method of the embodiment is that the way of irradiating the object S with light differs between the reflection mode and the transmission mode. That is, as shown in FIG. 1A, in the reflection mode, the object S is irradiated with light from the light source 1 from the first side. On the other hand, as shown in FIG. 1B, in the transmission mode, the object S is irradiated with light from the second side opposite to the first side. In the reflection mode, the diffracted light reflected on the first side is incident on the image sensor 2, and in the transmission mode, the diffracted light transmitted on the first side is incident on the image sensor 2. That is, the image pickup side by the image pickup device 2 is the same in the reflection mode and the transmission mode.

Next, the digital holography device of each embodiment used for implementing the digital holography method of the above embodiment will be described. First, the digital holography device according to the first embodiment will be described. FIG. 2 is a schematic front view of the digital holography device according to the first embodiment.
As shown in FIG. 2, the digital holography device according to the first embodiment obtains a reflected diffracted light guiding system 31 that guides light from the light source 1 to an object S and obtains transmitted diffracted light in order to obtain reflected diffracted light. Therefore, a light guide system 32 for transmitted diffracted light that guides light from the light source 1 to the object S, a reference light guide system 33 that guides light from the light source 1 to the imaging surface of the image sensor 2 without passing through the object S, and reflection The imaging device 2 is provided with an imaging surface located at a position where the diffracted light and the reference light interfere with each other and the transmitted diffracted light and the reference light interfere with each other. In this apparatus, there is a selection optical element that selectively selects whether the reflection diffracted light is incident on the image pickup surface of the image pickup element 2 to enter the reflection mode or the transmission diffracted light to enter the transmission mode. Is provided.

As described above, the object light is emitted to the same first side in both the reflection mode and the transmission mode. Therefore, the image pickup device 2 is provided on the image pickup optical path Pi set on the first side. A first beam splitter 41 is provided on the imaging optical path Pi. Since the light for reflected diffracted light irradiates the object S through the imaging optical path Pi, the first beam splitter 41 is disposed in the middle of the imaging optical path Pi, and the light for reflected diffracted light is introduced from there. Yes.
In this embodiment, the imaging optical system 5 including a lens is provided on the imaging optical path Pi. The imaging optical system 5 is not necessary when the imaging device 2 is located relatively close to the object S and uses Fresnel diffraction (in the case of a Fresnel hologram). Further, the imaging optical system 5 is not necessary in the case of a Fourier transform hologram (lensless Fourier transform hologram) in which the reference light is a spherical wave. The imaging optical system 5 is necessary when a lens is used to form a Fraunhofer hologram (Fourier transform hologram), or when an interference image due to diffracted light from the object S is enlarged or reduced. .

In order to obtain a clear hologram reproduction image, it is necessary that the object beam and the reference beam sufficiently interfere to form interference fringes. For this purpose, the light source 1 needs to be in phase with a single wavelength (coherent). For this reason, a laser is used as the light source 1. For example, a He—Ne (helium neon) laser having a wavelength of 632.8 nm is used.
Although it is possible in principle to use different light sources for the object light and the reference light, it is very difficult to sufficiently align the wavelength and phase when using different light sources. For this reason, the light from one light source 1 is divided and used. That is, the light emitted from the light source 1 is divided by the reference light extraction beam splitter 42, and one is used as the reference light.

The optical element for selection is a movable mirror 43 in this embodiment. The movable mirror 43 is a movable mirror and selects whether to guide the irradiation light from the reference beam extraction beam splitter 42 to the reflected diffracted light guide system 31 or to the transmitted diffracted light guide system 32. It is like that.
Note that this embodiment is an in-line apparatus, and the reference light is incident on the imaging surface of the imaging device 2 perpendicularly in the same manner as the object light. As shown in FIG. 1, an integration beam splitter 44 is disposed on the imaging optical path Pi, and the reference light is reflected by the integration beam splitter 44 and enters the imaging surface of the imaging device 2 perpendicularly. ing. The reference light guide system 33 includes a reference light first mirror 331 and a reference light second mirror 332, and integrates the light extracted by the reference light extraction beam splitter 42. It has led to

In the method and apparatus of the embodiment, the hologram S is obtained by placing the object S in a container such as a petri dish. After the light source 1 is operated and hologram data is first obtained in, for example, the reflection mode, the movable mirror 43 is moved to obtain hologram data in the transmission mode. Each hologram data is processed by a computer (not shown in FIG. 1) to which the image sensor 2 is connected. A predetermined program (hereinafter referred to as an image reproduction program) for obtaining a reproduction image from hologram data is installed in the computer, and the reproduction image is displayed on the display by executing the image reproduction program. It is possible to measure the distance of a specific location or to display the reflectance distribution or transmittance distribution of the object S.
According to the method and apparatus of such an embodiment, hologram data can be obtained for each object S using reflected diffracted light and transmitted diffracted light. It becomes. For example, it can be suitably used to know both the reflectance distribution and the transmittance distribution on the surface of the object S.

At this time, in the method and apparatus of the embodiment, since the reflection mode and the transmission mode are performed separately in time, the configuration of the optical system is simplified. Even with the configuration as shown in FIG. 15, hologram data based on reflected diffracted light and hologram data based on transmitted diffracted light can be obtained. However, with the configuration shown in FIG. Therefore, it is necessary to separate this and make it incident on each image sensor. For this reason, a complicated imaging optical system 5 is required. In fact, FIG. 15 shows a complicated imaging optical system using the polarization beam splitter 143 and the like. The imaging optical system means an optical system on the optical path of object light from the object to the imaging device.
On the other hand, according to the method or apparatus of the present embodiment, since the reflection mode and the transmission mode are temporally separated, optical separation is unnecessary. For this reason, the imaging optical system 5 becomes simple. The fact that the imaging optical system 5 is simple means that, in addition to cost advantages, the possibility of wavefront disturbance due to the use of more optical elements is reduced, so that more accurate hologram data can be obtained. There is an advantage.

Further, simultaneously performing the reflection mode and the transmission mode as shown in FIG. 15 means that the object S is irradiated with light from one side and reflected and reflected on one side and reflected on the other side. This means that the transmitted diffracted light that passes through is captured by the image sensor. In this case, as described above, high-accuracy hologram data cannot be obtained unless the object S is suspended and held in the air. However, when the reflection mode and the transmission mode are performed separately in time, the light can be irradiated from the opposite side in the transmission mode, and the imaging side can be the same side of the object S. it can. Therefore, highly accurate hologram data can be obtained even when the object S is placed in a container such as a petri dish, and observation in the reflection mode and observation in the transmission mode can be performed from the same side viewpoint. The device of the embodiment is such a device.

Performing the reflection mode and the transmission mode is suitable for examining the state and shape of the object S in detail as described above. However, the fact that this can be performed with one apparatus is not only cost-effective but also workable. This is also suitable. If a digital holography device that performs measurement in the reflection mode and a digital holography device that performs measurement in the transmission mode are prepared, the same can be achieved. In this case, the object S is taken out after measurement is performed using the device in the reflection mode. The measurement must be performed by setting the device in a transmission mode. According to the apparatus of this embodiment, there is no such problem.
Generally speaking, when the object S is an opaque body, hologram data cannot be acquired in the transmission mode. In the case of a transparent body, data can be acquired in both the transmission mode and the reflection mode. Interference fringes may occur, and accurate hologram data may not be obtained due to this influence. Considering these, the merit that the mode can be arbitrarily selected with one apparatus according to the property of the object S as the object is very large.

Also, the point that the reference light is guided to the image sensor 2 without passing through the object S is excellent in that a stable reference light is always obtained regardless of the conditions of the object S. In FIG. 15, the light transmitted through the object S is taken out and used as reference light. As described above, it is not impossible to make the reference light incident on the image sensor 2 through the same route as the object light route of light irradiation on the object S → object light → image sensor 2. However, if this is done, the reference light changes depending on the optical properties of the object S, so that stable light cannot always be used as the reference light. On the other hand, if the reference light is guided to the image sensor 2 without passing through the object S as in the present embodiment, the reference light is always stable without changing depending on the conditions of the object S. it can. For example, when measuring the light transmittance from the object S, according to the method or apparatus of this embodiment, there is an advantage that data having quantitativeness can be obtained.

Next, a digital holography device according to a second embodiment that is more practical will be described below. FIG. 3 is a schematic front view of a digital holography device according to a second embodiment of the present invention.
The digital holography device of the second embodiment includes a light guide system 31 for reflected diffracted light that guides light from the light source 1 to the object S to obtain reflected diffracted light, and light from the light source 1 to obtain transmitted diffracted light. A diffracted light guide system 32 for transmitting diffracted light to the object S, a reference light guide system 33 for guiding light from the light source 1 to the imaging surface of the image sensor 2 without passing through the object S, reflected diffracted light and reference light. The imaging device 2 in which the imaging surface is located at a position where the transmitted diffracted light and the reference light interfere with each other, and the reflected diffracted light is incident on the imaging surface of the imaging device 2 to enter the reflection mode or the transmitted diffracted light. And a control system (not shown in FIG. 3) for controlling the operation of the selection optical element.

In the second embodiment, the light guide system 31 for reflected diffracted light is partially used as a reference light guide system in order to improve the practicality of the apparatus. Specifically, in the second embodiment, a second beam splitter 45 is provided in place of the movable mirror 43 in the first embodiment. A drive unit 451 is attached to the second beam splitter 45. Further, the first beam splitter 41 is provided as in the first embodiment, but the first beam splitter 41 is provided with a switching unit 411 as a drive mechanism. The first beam splitter 41 and the second beam splitter 45 function as a selection optical element.

As shown in FIG. 3, the optical path extending from the light source 1 (hereinafter, the main optical path) can be branched by the second beam splitter 45 after being bent by 90 ° by the first mirror 46. . The light guide system 31 for reflected diffracted light is arranged on the main optical path and on the image side of the division position by the second beam splitter 45 (forward in the light traveling direction, hereinafter the same). As shown in FIG. 1, the light guide system 31 for reflected diffracted light includes a first beam expander 311, a second mirror 312, a first beam splitter 41, and the like. The second mirror 312 bends the light whose width is widened by the first beam expander 311 by 90 ° and reaches the first beam splitter 41.

In addition, the light guide system 32 for transmitted diffracted light is arranged on each optical path (hereinafter referred to as a branched optical path) Ps formed separately from the main optical path by the second beam splitter 45 being positioned on the main optical path. It is comprised by the optical element. Each optical element is the second beam expander 321, the third mirror 322, or the like.
The third mirror 322 bends the branched optical path Ps by 90 ° to reach the position of the object S. The light traveling on the branched optical path Ps divided by the second beam splitter 45 is reflected by the third mirror 322 via the second beam expander 321 and reaches the object S. This light passes through the object S and becomes transmitted diffracted light.
The drive unit 451 provided in the second beam splitter 45 includes a division position where the second beam splitter 45 is arranged on the main optical path to divide the light, and a retraction position where the light is retreated from the main optical path so as not to divide the light. Is a mechanism for moving the second beam splitter 45 between the two. Thereby, the second beam splitter 45 functions as a selection optical element. The drive unit 451 is configured with a linear motion stage such as a linear stage, for example.

The switching unit 411 provided in the first beam splitter 41 changes the state of the first beam splitter 41 so that the first beam splitter 41 functions as a selection optical element. Specifically, in the reflection mode, the switching unit 411 causes the first beam splitter 41 to be in the same state as in the first embodiment, that is, the light guided by the reflected diffracted light guide system 31. It is assumed that the posture is reflected toward the object S (hereinafter referred to as a first state). Then, in the transmission mode, the switching unit 411 rotates the first beam splitter 41 by 90 °, reflects the light guided by the reflected diffracted light guiding system 31, and directly enters the imaging element 2. It is a posture (hereinafter referred to as a second state). That is, the switching unit 411 prevents the light from the light source 1 from irradiating the object S from the opposite side in the transmission mode, and the reflected diffraction light guide system 31 functions as the reference light guide system 33. It plays two roles. Such a switching part 411 is comprised with a rotation stage, for example. The rotation axis is on a straight line that is perpendicular to the optical axis and passes through the center of the reflection surface of the first beam splitter 41 along the reflection surface.

As will be understood from the above description, the reference light guide system 33 guides the reference light to the imaging device 2, but guides the reference light through different paths in the transmission mode and the reflection mode. In the transmissive mode, the reference light guide system 33 guides the reference light to the image sensor 2 by using a part of the above-described reflected diffracted light guide system 31. That is, the reference light guide system 33 in the transmission mode includes the first mirror 46, the second beam splitter 45, the first beam expander 311, the second mirror 312, and the like.
In the reflection mode, the reference light guide system 33 is configured by a part of the shared reflection-diffracted light guide system 31 and the additional light guide system 34. In the reflection mode, the first beam splitter 41 advances one of the divided lights toward the object S. The additional light guide system 34 guides the other light split by the first beam splitter 41 to the image sensor 2. In the present embodiment, the additional light guide system 34 returns the other light to the first beam splitter 41 and guides the imaging element 2 through the first beam splitter 41 in order to guide it through the same path as much as possible. The light is incident on the imaging surface as reference light.

More specifically, in the reflection mode, the reference light guide system 33 includes the first mirror 46, the first beam expander 311, the second mirror 312, the first beam splitter 41, And an additional light guide system 34. The additional light guide system 34 includes a fourth mirror 341, a folding mirror 342, and the like. The fourth mirror 341 folds the light from the second beam splitter 45 by 90 °, and the folding mirror 342 folds the light by bending 180 °.
A beam stopper 343 and a stopper driving unit 344 that drives the beam stopper 343 are provided between the fourth mirror 341 and the folding mirror 342. The beam stopper 343 and the stopper driving unit 344 do not need the additional light guide system 34 in the transmission mode, and thus stop the light so that it does not return.

In the digital holography device of the present embodiment, a first spatial filter 316 and a second spatial filter 326 are arranged in order to obtain highly accurate hologram data. The first spatial filter 316 and the second spatial filter 326 are disposed in the reflected diffracted light guide system 31, the transmitted diffracted light guide system 32, and the reference light guide system 33, respectively.
More specifically, a first spatial filter 316 is disposed in the light guide system 31 for reflected diffracted light, and a second spatial filter 326 is disposed in the light guide system 32 for transmitted diffracted light. Since the reflected diffracted light guide system 31 is also used as the reference light guide system 33, all of the transmitted diffracted light, reflected diffracted light, and reference light all pass through the spatial filter. become. That is, all the light incident on the image pickup device 2 passes through the spatial filter. For this reason, it is extremely suitable in terms of obtaining accurate hologram data.

In the present embodiment, the first spatial filter 316 and the second spatial filter 326 are arranged as close as possible to the object S or the image sensor 2. Specifically, in the light guide system 31 for reflected diffracted light, the first spatial filter 316 is arranged on the image side from the branch point of the branch optical path Ps in the main optical path, and the first spatial filter Only one second mirror 312 is arranged between 316 and the first beam splitter 41. In the light guide system 32 for transmitted diffracted light, the second spatial filter 326 is disposed on the branch optical path Ps, and only one third filter is provided between the second spatial filter 326 and the object S. The mirror 322 is arranged.

In this way, by minimizing the number of mirrors arranged between the first spatial filter 316 and the second spatial filter 326 and the object S or the image pickup device 2, it is possible to prevent damage to the mirror and the mirror. It can suppress that the precision of hologram data falls by the influence of the dust which adhered.
In the light guide system 31 for reflected diffracted light, a spatial filter can be disposed between the second mirror 312 and the first beam splitter 41. In this way, the accuracy of hologram data can be further improved. In the light guide system 32 for transmitted diffracted light, a spatial filter can be disposed between the third mirror 322 and the object S, and the accuracy of hologram data can be further improved.

In the present embodiment, in order to simplify the configuration of the optical system, the beam expander and the spatial filter are configured to partially use the optical element. That is, the first spatial filter 316 is realized by the first beam expander 311, and the second spatial filter 326 is realized by the second beam expander 321. A specific structure will be described with reference to FIG. FIG. 4 is a schematic diagram showing the second beam expander 321 and the second spatial filter 326 as an example.
As shown in FIG. 4, the second beam expander 321 includes a condenser lens 323 and a collimator lens 324. By aligning the object side focal point f2 of the collimator lens 324 with the position of the image side focal point f1 of the condenser lens 323 and using a collimator lens 324 having a large aperture, as shown in FIG. The increased parallel light is emitted.

And in this embodiment, the pinhole board 325 is arrange | positioned in the condensing position by the condensing lens 323. FIG. The pinhole of the pinhole plate 325 coincides with the light collecting position. As can be seen from FIG. 4, the second spatial filter 326 is configured by the condenser lens 323 and the pinhole plate 325. That is, the condensing lens 323 is also used as the second beam expander 321 and the second spatial filter 326. With such a structure, the configuration of the optical system is simplified, and the cost is reduced by reducing the number of parts. The first spatial filter 316 realized in the first beam expander 311 has the same structure.

Next, the imaging optical system 5 will be described.
Also in the present embodiment, the reflected diffracted light guide system 31 irradiates light from the side opposite to the side where the transmitted diffracted light guide system 32 irradiates the object S with light, and the imaging optical system 5 Is provided on the imaging optical path Pi that extends on the light irradiation side of the light guide system 31 for reflected diffracted light. That is, the reflected diffracted light and the transmitted diffracted light are configured to reach the image pickup surface of the image pickup device 2 via a common image pickup optical path Pi, and the image pickup optical system 5 is disposed on this common optical path.
The imaging optical system 5 includes an objective lens 51 arranged on the side close to the object S and an imaging lens 52 arranged on the side close to the imaging element 2. Another major feature of the apparatus of this embodiment is that the imaging optical system 5 is a telecentric optical system. Hereinafter, this point will be described with reference to FIG.

FIG. 5 is a schematic diagram schematically showing the telecentricity of the imaging optical system 5 in the apparatus of FIG. A telecentric optical system generally refers to an optical system in which the principal ray can be regarded as being parallel to the principal axis. FIG. 5A shows an optical system telecentric on the image side. In particular, an optical system in which the principal ray can be considered parallel to the optical axis on both the object side and the image side is called double-sided telecentric.

The telecentricity of the imaging optical system 5 in the present embodiment is such that, as shown in FIG. 5 (2), the principal ray is the optical axis on both the front side (object S side) and the rear side (imaging element 2 side) of the optical system. It can be regarded as parallel to. In the present embodiment, the light source 1 is a laser, and it is assumed that plane waves (parallel light) are incident. For this reason, a coupling optical system that is telecentric on both sides can be achieved by making the position of the rear focal point of the objective lens 51 coincide with the position of the front focal point of the imaging lens 52 (confocal).
The telecentricity of the imaging optical system 5 in this embodiment has another meaning. As shown in FIG. 5 (3), the objective lens 51 and the imaging lens 52 are an infinite correction optical system, and the diffracted light (object light) emitted from one point of the object S is the objective lens 51. Thus, the light beam becomes parallel light and enters the imaging lens 52.
The infinity correction system having telecentricity has a great advantage that the size of the image does not change even when the position of the object S is changed and the focus is adjusted. This is advantageous when it is desired to obtain hologram data with reflected or transmitted diffracted light from a position slightly deeper than the surface of the object S. For example, when the apparatus of the present embodiment is configured as a digital holographic microscope and a reproduced image is obtained while enlarging a biological sample that is transparent to some extent, there is a great advantage.

As such an imaging optical system 5, an object side telecentric lens is adopted as the objective lens 51, an image side telecentric lens is adopted as the imaging lens 52, and the focal position on the image side of the objective lens 51 and the imaging lens 52 are adopted. This can be achieved by arranging in a state where the object side focal position of the lens is matched (confocal state). As the object-side telecentric lens and the image-side telecentric lens, commercially available lenses can be used, and detailed description thereof is omitted. The imaging lens 52, which is an image-side telecentric lens, constitutes an infinity correction system. Therefore, it is preferable to use a lens having a large effective aperture in order to reduce light loss as much as possible.

The image sensor 2 is a CCD camera, for example. The CCD camera has an imaging surface of 1024 × 1024 pixels, for example. The imaging element 2 is arranged such that the center of the imaging surface is located on the optical axis and the imaging surface is perpendicular to the optical axis.
A polarizing filter 11 and a quarter wavelength plate 12 are provided on the optical path immediately after the light is emitted from the light source 1. The polarizing filter 11 and the quarter wavelength plate 12 prevent the light from returning to the light source 1 and entering.
The polarizing filter 11 transmits only linearly polarized light in a specific direction. The quarter-wave plate 12 is arranged by shifting the crystal axis by 45 ° from the transmission axis (direction of linearly polarized light) of the polarizing filter 11 and has a function of converting linearly polarized light into circularly polarized light. The circularly polarized light is irradiated onto the object S or incident on the image sensor 2 as reference light. May come back. The returned circularly polarized light is again converted to linearly polarized light by passing through the ¼λ wavelength plate 12 again. Since this linearly polarized light has a phase difference of ¼ wavelength, the polarization direction is shifted by 90 ° from the first linearly polarized light. For this reason, this light cannot pass through the polarizing filter 11 and is blocked at the polarizing filter 11. Since the return light does not enter the light source 1, damage to the light source 1 due to the return light is prevented.

Further, the holding of the object S will be described. The object S is held by an appropriate member in accordance with its properties and size. For example, as described above, the object S is held on a transparent container such as a petri dish or a transparent plate-like member, and in the case of a large object S, a clamp-like member that is sandwiched and held is used. Sometimes it is done. If the object S is a plate-like object such as a substrate, it may be held by a frame-shaped member. In any case, the object S is held at a predetermined position with respect to the light guide system and the imaging optical system 5 by such a holding member.

Next, the control system of the apparatus will be described with reference to FIG. FIG. 6 is a schematic diagram illustrating a control system of the digital holography device according to the second embodiment.
The control system 6 that controls the optical elements for selection and the like includes a control board 61 and a computer 63 in which a switching program 62 that sends a signal to the control board 61 to switch between the reflection mode and the transmission mode is installed. .
In the present embodiment, since the computer 63 is also provided with a calculation function of a reproduced image, a general computer that operates on a general-purpose OS such as a desktop personal computer is used as the computer 63. And in order to enable control of each part, the control board 61 is attached as the interface. The switching program 62 is a program for sending a control signal for switching between the reflection mode and the transmission mode from the computer 63 to the control board 61.

The control board 61 drives the switching unit 411 of the first beam splitter 41, the driving unit 451 of the second beam splitter 45, and the stopper driving unit 344 of the beam stopper 343 based on the transmitted control signal. Each operation signal is sent out. The control board 61 has a storage unit such as a RAM, and a sequence control program for outputting each operation signal in accordance with the control signal is written in the storage unit.
When the reflection mode is selected in the switching program 62 and a control signal for switching to the reflection mode is transmitted, the sequence control program reads the switching unit 411 of the first beam splitter 41 and the driving unit 451 of the second beam splitter 45. And an operation signal for the reflection mode is programmed to be sent to the stopper driving unit 344 of the beam stopper 343. Further, when the transmission mode is selected in the switching program 62 and a control signal indicating that the transmission mode is set is transmitted, the sequence control program sends the operation signal for the transmission mode to the switching unit 411 of the first beam splitter 41, It is programmed to send to the drive unit 451 of the second beam splitter 45 and the stopper drive unit 344 of the beam stopper 343.

When the first beam splitter 41, the second beam splitter 45, and the beam stopper 343 are provided with sensors for detecting their positions and postures, and signals from the sensors are input to the control board 61 and used for control. Is preferred. The signal from each sensor is used to monitor whether each unit is operating normally, or to check the position and orientation when performing the same mode as the previous operation, so that no operation signal is sent. Can be used.
The light source 1 is turned on and off by a switch provided in a power source (not shown). However, the light source 1 can be turned on / off by sending a signal from the computer 63 via the control board 61.

The computer 63 is also installed with a program (hereinafter referred to as a reproduction program) 64 that executes a predetermined calculation process for obtaining a reproduction image based on hologram data obtained on the imaging surface of the image sensor 2.
Various calculation formulas and techniques are known for calculation processing for obtaining a reproduced image from hologram data, and any one can be selected and applied. As an example, one using the Fourier transform is shown below.

The reproduction plane (plane on which a reproduction image can be generated) is parallel to the hologram plane (here, the imaging plane of the image sensor 2), and the distance is R, and r is a point on the reproduction plane to a point on the reproduction plane. Suppose that it is a distance. x and y are coordinates on the hologram surface, and X and Y are coordinates on the reproduction surface.
The complex amplitude distribution on the reproduction surface can be expressed as Equation 1 according to Kirchhoff's diffraction integral equation. g (x, y) is hologram data, and G (X, Y) is a complex amplitude distribution of the generated image.

In Equation 1, λ is the wavelength and k is the wave number. If the Fresnel approximation shown in Formula 2 is applied and substituted into Formula 1, Formula 3 is obtained.

In Equation 3, when the integral is regarded as Fourier transform and transformed, Equation 4 is obtained.

In Equation 4, the parentheses of F indicate Fourier transform. x and y are outputs from each pixel on the imaging surface, and a reproduced image G (X, Y) is obtained by performing a discrete Fourier transform.

The computer 63 is installed with a main program (not shown) for controlling the overall operation. The main program is automatically started when the apparatus is turned on. The main program displays a screen for selecting either the reflection mode or the transmission mode on the display, or displays buttons for instructing execution of main operations such as acquisition of hologram data and formation of a reproduced image. .

Next, the operation of the digital holography device according to the second embodiment will be described with reference to FIGS. 7 to 9 are schematic views showing the operation of the digital holography device of the second embodiment. Among these, FIG. 7 is a diagram showing a comparison of the progress of each light in the reflection mode and the transmission mode, FIG. 8 is a diagram showing an outline of the operation flow in the reflection mode, and FIG. 9 is an operation in the transmission mode. It is the figure which showed the outline of the flow.
First, the object S from which hologram data is acquired is placed and held at a predetermined position by a holding member. In this state, the apparatus is turned on to start the main program. On the display of the computer 63, a screen for selecting either the reflection mode or the transmission mode is displayed, and either is selected by the input unit.

For example, when the reflection mode is selected, the switching program 62 is executed, and a control signal for setting the reflection mode is sent to the control board 61. Upon receiving this control signal, the control board 61 sends the operation signals for the reflection mode to the switching unit 411 of the first beam splitter 41, the driving unit 451 of the second beam splitter 45, and the stopper driving unit of the beam stopper 343. 344.
Specifically, as shown in S1 of FIG. 8, the control board 61 first sends an operation signal to the switching unit 411 so that the first beam splitter 41 is in the first state. In the first state, as shown in FIG. 7A, light incident on the first beam splitter 41 via the light guide system 31 for reflected diffracted light is reflected by the reflecting surface and is reflected on the object S. It is in a state of taking an attitude of moving forward.

Next, as shown in S2 of FIG. 8 and FIG. 7A, the control board 61 sends an operation signal to the drive unit 451 to retract the second beam splitter 45 from the branch position on the main optical path. That is, in the reflection mode, the light guide system 32 for transmitted diffracted light is not used.
Next, as shown in S3 of FIG. 8 and FIG. 7A, the control board 61 sends an operation signal to the stopper driving unit 344 to retract the beam stopper 343 from the optical path.
This completes the operation of the sequence control program on the control board 61.

Next, as shown in S4 of FIG. 8, the light source 1 is turned on to emit light. The light L1 emitted from the light source 1 enters the first beam splitter 41 through the light guide system 31 for reflected diffracted light. The light L1 is divided into one light L2 reflected toward the object S by the reflecting surface of the first beam splitter 41 and the other light L3 that passes through the first beam splitter 41 and reaches the additional light guide system 34. Is done.
One light L2 is applied to the object S via the imaging optical system 5, and reflected diffracted light L4 is emitted from the object S. The reflected diffracted light L4 enters the first beam splitter 41 again through the imaging optical system 5, passes through the first beam splitter 41, and enters the imaging device 2.
The other light L3 is reflected by the folding mirror 342 of the additional light guide system 34 and returns to the first beam splitter 41. The light L3 is reflected by the reflection surface of the first beam splitter 41 and enters the imaging surface of the imaging device 2 as reference light.
Then, as shown in S5 and S6 of FIG. 8, the reflected diffracted light L4 and the reference light L3 interfere with each other on the image pickup surface of the image pickup device 2, and the interference fringes are picked up on the image pickup surface and the hologram data is output to the computer 63. Is done. When the hologram data is output, a reproduction program 64 is executed on the computer 63, and a reproduction image of the object S is formed by performing the calculation process as described above.

When the transmission mode is selected on the computer 63, the switching program 62 sends a control signal for setting the transmission mode to the control board 61. Upon receiving this control signal, the control board 61 executes a sequence control program, and sends each operation signal for the reflection mode to the switching unit 411 of the first beam splitter 41, the drive unit 451 of the second beam splitter 45, The beam is sent to the stopper driving unit 344 of the beam stopper 343.
Specifically, as shown in S1 of FIG. 9, the control board 61 drives the first beam splitter 41 by the switching unit 411 to place the first beam splitter 41 in the second state. In the second state, as shown in FIG. 7B, the light incident on the first beam splitter 41 via the light guide system 31 for reflected diffracted light is reflected by the reflecting surface and directed toward the image sensor 2. This is a state of taking a forward posture. In the second state, the direction of the reflecting surface of the first beam splitter 41 is 90 ° different from that in the first state.
Next, as shown in S2 of FIG. 9 and FIG. 7B, the control board 61 sends an operation signal to the drive unit 451 and arranges the second beam splitter 45 on the main optical path. That is, in the transmission mode, the light guide system 32 for transmitted diffracted light and the light guide system 31 for reflected diffracted light are used.
Next, as shown in S3 of FIG. 9 and FIG. 7B, the control board 61 sends an operation signal to the stopper driving unit 344, and places the beam stopper 343 on the optical path of the additional light guide system 34. , Block the light path.
This completes the operation of the sequence control program on the control board 61.

Next, as shown in S4 of FIG. 9, the light source 1 is operated to emit light. The light emitted from the light source 1 enters the second beam splitter 45. This light is branched into one light L5 that is transmitted through the second beam splitter 45 and the other light L6 that is reflected by the reflecting surface of the second beam splitter 45 and is directed toward the object S. One light L <b> 5 is guided by the reflected diffracted light guiding system 31 that is also used as the reference light guiding system 33, and enters the first beam splitter 41. The light L5 incident on the first beam splitter 41 is reflected by the reflection surface of the first beam splitter 41, travels toward the image sensor 2, and enters the image surface of the image sensor 2 as reference light. The light transmitted through the first beam splitter 41 is shielded by the beam stopper 343 and does not return to the first beam splitter 41.
The other light L6 divided by the second beam splitter 45 is irradiated onto the object S through the light guide system 32 for transmitted diffracted light. The light passes through the object S and is emitted from the object S as transmitted diffracted light L7. The transmitted diffracted light L7 enters the first beam splitter 41 via the imaging optical system 5, passes through the first beam splitter 41, and enters the imaging surface of the imaging device 2.
As shown in S5 and S6 in FIG. 9, on the imaging surface of the imaging device 2, an interference fringe between the reference light L5 and the transmitted diffracted light L7 is formed, and this interference fringe is imaged to obtain hologram data. Similarly, the hologram data is sent to the computer 63, and the reproduction program 64 is executed to form a reproduction image of the object S.

As described above, the image is reproduced by sequentially performing the reflection mode and the transmission mode, but the information of the reproduction image includes amplitude information and phase information. Generally speaking, the amplitude information is suitable for observing the two-dimensional shape and contrast of the surface of the object, and the phase information is suitable for observing the shape at the depth of the object. Therefore, when obtaining a reproduced image, there are cases where only the amplitude information is extracted and the two-dimensional shape is mainly observed, or only the phase information is extracted and the depth state is observed.

In the operation of the apparatus of the present embodiment, the fact that the imaging optical system 5 is telecentric has a remarkable effect in terms of obtaining highly accurate hologram data. Hereinafter, this point will be described with reference to FIG.
FIG. 10 is a schematic diagram showing the effect of the device of the second embodiment including the telecentric imaging optical system 5. FIG. 10A is shown for comparison, and is a wavefront diagram when an imaging optical system that is not telecentric is used. FIG. 10B is a wavefront diagram when the telecentric imaging optical system 5 is used in the present embodiment.

The telecentricity in the apparatus of this embodiment is achieved by arranging the objective lens 51 and the imaging lens 52 constituting the infinite correction optical system confocally. As shown in FIG. 10A1, when a general finite correction optical system is used, the plane wave Lp can be applied to the object S in the transmission mode. However, in the finite correction optical system, when the transmission mode is switched to the reflection mode, the object S is irradiated with the plane wave Lp as shown in FIG. The object S is irradiated with light (spherical wave) Ls collected by the objective lens. In this case, a reproduced image cannot be formed with high accuracy because the object light imaged by the image sensor 2 is distorted.

Further, as shown in FIG. 10A2, when the spherical wave Ls is irradiated to the object S, the field of view changes as compared with the transmission mode. In addition, digital holography has the feature that the working distance can be changed in principle because it can calculate a reconstructed image at an arbitrary position on the optical axis, but the object light is distorted in the optical system of the comparative example. The field of view also changes with changes in working distance. In order to suppress this change in the visual field, a separate correction calculation is required.
On the other hand, if an infinite correction optical system is used and the imaging lens 52 and the objective lens 51 have a confocal optical arrangement as in this embodiment shown in FIG. 10B, a telecentric optical system is used. Therefore, regardless of whether the reflection mode or the transmission mode is selected, the plane wave Lp is irradiated to the object S (FIGS. 10B1 and 10B2). Note that “confocal” means that the focal point on the image side of the objective lens 51 is coincident with the focal point on the object side of the imaging lens 52 as described above.

Thus, according to the present embodiment, the plane wave Lp is irradiated to the object S regardless of whether the reflection mode or the transmission mode is selected. Therefore, in both the transmission mode and the reflection mode, a region having the same size can be set as an observation target, and an image can be reproduced by the same reproduction calculation means. Further, since the object light is not distorted, correction calculation is not required, and image reproduction with a variable working distance, which is a principle feature of digital holography, can be performed freely. Furthermore, since it is a telecentric optical system, there is also an advantage that the imaging magnification does not change during image reproduction with a variable working distance. Note that image reproduction with variable working distance means that image reproduction can be performed by focusing on an arbitrary position in the depth direction of the object.

Also in the digital holography device of this embodiment, since both the reflection mode and the transmission mode can be performed by one unit, various observations and measurements on the object S can be performed at low cost. In addition, since the reflected diffracted light and the transmitted diffracted light are temporally separated and enter the image sensor 2, the configuration of the optical system is simplified and only one image sensor 2 is required. For this reason, the cost of one apparatus is also reduced.
Moreover, since the light for reflected diffracted light is irradiated from the first side of the object S and the light for transmitted diffracted light is irradiated from the opposite second side, the object light is exclusively captured on the first side. Can do. Therefore, highly accurate hologram data can be obtained without forcing the object S to float in the air.
In addition, the imaging optical system 5 makes object light incident on the imaging device 2 in both the reflection mode and the transmission mode. However, since the imaging light system 5 is shared by both modes, the configuration of the optical system is also simple in this respect. And contributes to reducing the cost of the apparatus.

In practicing the present invention, separate imaging optical systems may be provided for the reflection mode and the transmission mode, and a revolver type mechanism or the like may be adopted and used alternatively. In the reflection mode, the imaging optical system for the reflection mode is arranged on the imaging optical path Pi, and in the transmission mode, the imaging optical system for the transmission mode is switched and arranged on the imaging optical path Pi.
Further, even when the imaging optical system is shared in both modes, a part of the imaging optical system may be shared in addition to the case of sharing the whole. For example, the imaging lens may be shared, and the objective lens may be prepared for the reflection mode and the transmission mode and used by switching.

Further, as compared with the apparatus of FIG. 15, the imaging optical path Pi of the apparatus of the present embodiment is a straight line. That is, the object light emitted from the object S travels on a straight optical path and enters the image sensor 2. This point has the following effects.
First, since the optical path is straight, it is easy to adjust the optical axis. That is, in order to obtain hologram data with high accuracy, the object S, the imaging optical system 5 and the imaging element 2 need to be aligned on the optical axis with high accuracy, but this adjustment is easy because the optical axis is straight. .
Further, as shown in FIG. 15, if the optical path from the object S to the image sensor 2 is bent in a complicated manner, a large number of optical elements such as mirrors are required, which increases the cost. According to this embodiment, there is no such cost increase.
Furthermore, if the optical path is bent in a complicated manner, the wavefront is easily disturbed by an optical element such as a mirror, but this embodiment does not have such a problem. Also in this respect, it is possible to acquire hologram data with high accuracy.

Further, the apparatus according to the present embodiment uses the first spatial filter 316 and the second spatial filter 326, and both the object light and the reference light are light that has passed through the spatial filter. . For this reason, the wavefront enters the image sensor 2 with the noise removed. This also contributes greatly to improving the accuracy of the hologram data, and the spatial filter is located on the optical path closer to the object S. For this reason, the possibility that noise is mixed into the wavefront due to factors after passing through the spatial filter is reduced. This point also contributes greatly to improving the accuracy of hologram data.

In addition, compared with the first embodiment, the apparatus of the present embodiment further simplifies the optical system and enhances coherence by sharing the reference light guide system 33 with the object light guide system. It is a more practical device. Hereinafter, this effect will be described.
First, in the reflection mode, the light for reflected diffracted light and the reference light are guided from the light source 1 to the first beam splitter 41 by the same light guide system. The light for reflected diffracted light reaches the object S by being divided into the first beam splitter 41, and the reference light reaches the image sensor 2 without passing through the object S by the additional light guide system 34.
As described above, when the object light and the reference light are incident on the image sensor 2 while sharing the light guide system as much as possible, the difference in optical conditions is reduced or the difference in optical path length is reduced. It is easy to do. For this reason, the coherence between the reference beam and the object beam can be enhanced, which helps to obtain hologram data with higher accuracy, and a reduction in the apparatus cost due to the reduction in the number of optical elements used. The additional light guide system 34 has the same meaning in that the light is folded back and returned to the first beam splitter 41 so as to enter the imaging device 2 as reference light therefrom.
In the transmission mode, the light guided by the reflected diffracted light guiding system 31 is incident on the image sensor 2 through the first beam splitter 41, and almost all the light for guiding the reference light is reflected. The light guide system 31 for diffracted light is also used. For this reason, the coherence is further enhanced, the configuration of the optical system is further simplified, and cost reduction is further realized by reducing the number of optical elements used.

Next, a digital holography device according to a third embodiment of the present invention will be described.
FIG. 11 is a schematic front view of a digital holography device according to a third embodiment of the present invention. The apparatus according to the third embodiment enables an off-axis operation in the apparatus according to the second embodiment. In the off-axis method, since the object light and the reference light are incident at an angle, a desired image (true image) is formed separately from the conjugate image and the zero-order image (image by the reference light) during image reproduction. There is an advantage that can be prevented from overlapping.
The apparatus shown in FIG. 11 differs from the second embodiment in the configuration of the reference light guide system 33 in order to enable an off-axis type. That is, one of the mirrors constituting the reference light guide system 33 is arranged in a state where the angle with respect to the optical axis can be changed.
Specifically, out of the reflected diffracted light guiding system 31 that is also used as the reference light guiding system 33 in the transmission mode, the second mirror 312 in the second embodiment is an off-axis mirror (hereinafter, referred to as “off-axis mirror”). The first off-axis mirror) 317 is changed. The first off-axis mirror 317 is provided with a first off-axis driving unit 318, and the arrangement angle of the first off-axis mirror 317 with respect to the optical axis can be changed.

Further, regarding the reference light guide system 33 in the reflection mode, the configuration of the additional light guide system 34 is greatly changed. The additional light guide system 34 in the third embodiment is also configured to return the light transmitted through the first beam splitter 41 and return it to the first beam splitter 41 in the reflection mode. In the third embodiment, the additional light guide system 34 is a loop in order to dispose the off-axis mirror at a position close to the image sensor 2 and reduce (or eliminate) the difference between the object light and the optical path length. The optical path is formed.
More specifically, the additional light guide system 34 has a polarization beam splitter 345 on the optical path extending from the first beam splitter 41. The polarization beam splitter 345 is a beam splitter that transmits only a linearly polarized light component in a specific polarization direction and reflects other components. A quarter wavelength plate 346 is provided between the first beam splitter 41 and the polarization beam splitter 345.

As described above, the light from the light source 1 is converted into circularly polarized light by the polarizing filter 11 and the quarter wavelength plate 12 immediately after that. For this reason, when the light passes through the quarter-wave plate 346, the light becomes linearly polarized light in a direction further shifted by 45 °. The polarization beam splitter 345 reflects linearly polarized light in this direction and transmits other light.
A fifth mirror 347, a sixth mirror 348, and a second off-axis mirror 349 are provided along the optical path of linearly polarized light reflected by the polarization beam splitter 345. The light returns to the polarization beam splitter 345 by being reflected by these mirrors. The second off-axis mirror 349 is provided with a second off-axis driving unit 350.
A half-wave plate 351 is provided between the polarization beam splitter 345 and the fifth mirror. Therefore, the light returning to the polarization beam splitter 345 has a polarization direction shifted by 90 ° and is transmitted without being reflected by the polarization beam splitter 345. This light is again converted into circularly polarized light by passing through the quarter-wave plate 346 again, and reaches the image sensor 2 via the first beam splitter 41.

Also in this embodiment, since the additional light guide system 34 is not used in the transmission mode, a beam stopper and a stopper driving unit for blocking light are provided. Although the illustration of the beam stopper and the stopper driving unit is omitted, for example, a beam stopper can be disposed between the quarter-wave plate 346 and the polarization beam splitter 345.
In addition, a beam expander 352 is disposed in the additional light guide system 34. The beam expander 352 is, for example, an equal magnification beam expander, and has a pinhole inside as in the case shown in FIG. 4 to form a spatial filter configuration. Thereby, the fluctuation of the wavefront originating from optical components such as a mirror and a wave plate up to just before the spatial filter can be removed.

The off-axis mirror will be further described in detail with reference to FIG. FIG. 12 is a diagram showing a change in the arrangement angle of the off-axis mirror used in the third embodiment. FIG. 12 (1) is a schematic plan view, and FIG. 12 (2) is a schematic perspective view. is there. FIG. 12 shows a second off-axis mirror 349 arranged in the additional light guide system 34 as an example.
As shown in FIG. 9, the second off-axis mirror 349 can take a slightly inclined posture with respect to the optical axis instead of 45 °. As a result, the incident angle of the reference light when entering the imaging device 2 is not the same angle as the incident angle of the object light, but a predetermined angle (hereinafter referred to as an off-axis angle) with respect to the incident angle of the object light. 12 (1) is indicated by θ).

In the present embodiment, the posture of the second off-axis mirror 349 can be changed in two directions. That is, as shown in FIG. 12 (2), the rotation around the rotation axis A1 along the line formed by the plane formed by the optical axis before refracting and the optical axis after refracting intersecting the reflecting surface, The rotation about the rotation axis A2 in the direction perpendicular to the axis A1 and along the reflecting surface. By making such two rotations possible, the reference light can be incident on the imaging surface of the imaging device 2 with an off-axis angle θ in two orthogonal directions (XY directions). The direction in which the off-axis angle θ is given depends on which direction the true image is desired to be separated from the zero-order image and the conjugate image, and is arbitrary by the operator. The second off-axis mirror 349 may be tilted in a direction other than the direction shown in FIG. 12 to separate the image in that direction.
As such a drive unit for each off-axis mirror, a kinematic mirror holder that can be adjusted in two directions can be used, and an actuator can be attached to each adjustment shaft to enable control by an external signal. Can be adopted. Similarly, each drive unit is controlled by an operation signal sent from the control board 61.

The first off-axis mirror 317 in the light guide system 31 for reflected diffracted light is used for off-axis in the transmission mode, and is used as a normal mirror in the reflection mode. Therefore, the control board 61 sends an operation signal that is tilted at a predetermined angle from 45 ° so that the off-axis angle θ is obtained in the transmission mode. In the reflection mode, an operation signal is sent to return to a normal attitude, that is, an attitude of 45 ° with respect to the optical axis. Note that “normal mirror” means a mirror in a state where an off-axis angle does not occur depending on the mirror.
Since the second off-axis mirror 349 in the additional light guide system 34 is not used in the transmission mode, the second off-axis mirror 349 can be configured to maintain an inclination angle that achieves the off-axis angle θ. In this case, no operation signal is sent from the control board 61. Although a mechanism for changing the angle is not necessary, it is preferable that the angle can be changed for adjustment or the like.

As described above, the configuration of the additional light guide system 34 used in the reflection mode is greatly changed in this embodiment. The reason for this is to place the second off-axis mirror 349 as close as possible to the image sensor 2 and to reduce the optical path length difference between the reference light and the object light.
In the off-axis method, the true image is separated from the zero-order image and the conjugate image by causing the reference light to enter the object light obliquely. However, when the oblique angle (off-axis angle) increases, the spatial frequency on the imaging surface of the image sensor 2 increases (that is, the interference fringes become finer), and a clear image reproduction is affected by the resolution of the image sensor 2. Will not be able to. For this reason, the off-axis angle θ is preferably as small as about 2 to 3 °.
Because of such an off-axis angle θ, the first off-axis mirror 317 and the second off-axis mirror 349 are not inclined at 45 ° with respect to the optical axis as shown in FIG. However, if it is located on the optical path away from the image sensor 2, the incident position is greatly shifted on the imaging surface of the image sensor 2 even if the angle is slightly changed. The reference light needs to cover the entire image pickup surface of the image pickup device, and if a region where the reference light does not enter is formed due to a shift in the incident position, it becomes impossible to pick up the interference fringes at that portion. Therefore, the first off-axis mirror 317 and the second off-axis mirror 349 are provided so that the reference light is incident on the entire imaging surface of the imaging device 2 even at a small angle of about 2 to 3 °. The mirror should be close to 2.

In the configuration of the second embodiment shown in FIG. 3, the folding mirror 342 of the additional light guide system 34 may be an off-axis mirror, but is located away from the image sensor 2, so that the image of the image sensor 2 is captured. The deviation of the incident position of the reference light with respect to the surface becomes large. Although it is conceivable that the fourth mirror 341 on the optical path in front of the folding mirror 342 is an off-axis mirror, the fourth mirror 341 reflects twice before reaching the folding mirror 342 and after reaching it. For this reason, the deviation of the reference light is doubled.
Furthermore, it is conceivable that a folding mirror 342 is provided at the position of the fourth mirror 341, and this is used as an off-axis mirror. The difference in the optical path length between the diffracted light and the light becomes large. For this reason, a problem may arise in terms of coherence. That is, when the difference in the optical path length increases, the reference light and the object light are less likely to interfere due to the problem of temporal stability of the output of the light source 1.

Considering these points, from the viewpoint of securing the optical path length by arranging a mirror that reflects only once at a position close to the image sensor 2, a polarization beam splitter 345 forms a loop-shaped optical path, and off-axis is formed at one corner thereof. It is preferable to arrange a mirror for use. The additional light guide system 34 of the third embodiment is based on such an idea.
In addition, a supplementary explanation will be given of the fact that the first off-axis mirror 317 and the second off-axis mirror 349 are “close” at the position where the first off-axis mirror 317 and the second off-axis mirror 349 are arranged. They are integrated by the beam splitter 41. Therefore, it is “near” that the first mirror viewed from the first beam splitter 41 is an off-axis mirror when traced in the direction opposite to the light traveling direction.

The operation of the third digital holography device shown in FIG. 11 will be described with reference to FIG. FIG. 13 is a schematic diagram illustrating the operation of the third embodiment, and is a diagram comparing the progress of each light in the reflection mode and the transmission mode.
First, when the reflection mode is selected, an operation signal for the reflection mode is sent from the control board 61 to each unit and controlled. That is, as shown in FIG. 13A, the second beam splitter 45 is retracted from the main optical path, and the first beam splitter 41 is set to the first state. Further, a beam stopper (not shown) in the additional light guide system 34 is retracted from the optical path, and the additional light guide system 34 is opened. Note that the first off-axis mirror 317 is used as a normal mirror, and therefore maintains a 45 ° attitude with respect to the optical axis.

The light L1 emitted from the light source 1 passes through the polarizing filter 11 and the quarter-wave plate 12 to become circularly polarized light, and enters the first beam splitter 41 via the light guide system 31 for reflected diffracted light. To do. As shown in FIG. 13A, the light L1 is split into light L2 reflected by the first beam splitter 41 and light L3 transmitted. The light L <b> 2 reflected by the first beam splitter 41 is applied to the object S through the imaging optical system 5. The irradiated light L2 is reflected by the object S to become object light (reflected diffracted light) L4. The object light (reflected diffracted light) L4 enters the first beam splitter 41 via the imaging optical system 5, passes through the first beam splitter 41, and enters the imaging surface of the imaging device 2.
On the other hand, the light L3 that has passed through the first beam splitter 41 is incident on the additional light guide system 34. Since the light L3 is circularly polarized light, it is converted into linearly polarized light having a specific polarization component by the quarter wavelength plate 346, and the linearly polarized light L3 enters the polarization beam splitter 345.

The polarization beam splitter 345 reflects only the polarized light of the specific component converted by the quarter wavelength plate 346. Therefore, as shown in FIG. 13A, the light L3 is reflected by the polarization beam splitter 345, enters the half-wave plate 351, and is linearly polarized light whose polarization direction is 90 ° different from that of the linearly polarized light. Converted to light. The light L3 having a linearly polarized light different by 90 ° passes through the fifth mirror 347, the sixth mirror 348, and the beam expander 352, and then is reflected by the second off-axis mirror 349 and returns to the polarization beam splitter 345. At this time, since the second off-axis mirror 349 is slightly inclined with respect to the optical axis instead of 45 °, the light L3 reflected by the off-axis mirror is not parallel to the optical axis but slightly at an angle. Proceed with the.

The light L3 that has reached the polarization beam splitter 345 with an angle in this manner is transmitted through the polarization beam splitter 345 because the direction of linearly polarized light is converted by 90 ° by the half-wave plate 351. The light L3 is converted into circularly polarized light by the quarter-wave plate 346, reflected by the first beam splitter 41, and then incident on the imaging surface of the imaging device 2 as reference light. At this time, since the light passes through the second off-axis mirror 349, the reference light L3 is incident on the object light (reflected diffracted light) L4 with an off-axis angle θ as shown in FIG. On the imaging surface of the imaging device 2, the object light (reflected diffracted light) L4 and the reference light L3 interfere to form an interference fringe, and the interference fringe is imaged on the imaging surface. Thereby, hologram data in the reflection mode is obtained.
The light reflected by the second off-axis mirror 349 travels with an angle with respect to the optical axis as described above and passes through the polarization beam splitter 345 and the quarter-wave plate 346. However, since the angle with respect to the optical axis is very small, there is no problem in terms of light control in the polarizing beam splitter 345 and the quarter wavelength plate 346.

When the transmission mode is selected, an operation signal for the reflection mode is sent from the control board 61 to each unit and controlled. That is, as shown in FIG. 13B, the first beam splitter 41 is rotated by 90 ° to be in the second state. Further, the second beam splitter 45 moves on the main optical path, and a beam stopper (not shown) in the additional light guide system 34 is arranged on the optical path. Further, an operation signal is sent to the drive unit of the first off-axis mirror 317, and the first off-axis mirror 317 is tilted by a predetermined angle with respect to the optical axis from an attitude of 45 °.
Similarly, the light emitted from the light source 1 is converted into circularly polarized light and then enters the second beam splitter 45. As shown in FIG. 13B, a part of the light is reflected by the second beam splitter 45 and proceeds to the branch optical path Ps as the light L5 for transmitted diffracted light, and is transmitted to the object S by the light guide system 32 for transmitted diffracted light. Irradiated. The light L5 passes through the object S to become object light (transmission diffracted light) L6, enters the first beam splitter 41 through the imaging optical system 5, passes through the first beam splitter 41, and passes through the imaging element 2. Is incident on the imaging surface.

On the other hand, the light L7 that has passed through the second beam splitter 45 without being reflected by the second beam splitter 45 is guided by the reflected diffracted light guiding system 31 that also serves as the reference light guiding system 33, and the first L It reaches the beam splitter 41, is reflected by the first beam splitter 41, and enters the imaging surface of the imaging device 2 as reference light. At this time, since the first off-axis mirror 317 is tilted by a predetermined angle, the reference light L7 is incident on the object light L6 with an off-axis angle θ.
On the imaging surface of the imaging device 2, the reference light L7 and the object light L6 interfere with each other to form an interference fringe, and the interference fringe is imaged on the imaging surface to obtain hologram data. Then, a reproduced image of the object S is formed by similarly calculating the hologram data.

According to the digital holography device of the third embodiment, when the hologram data is calculated and the image is reproduced, the true image is formed separately from the zero-order image and the conjugate image. Can be obtained. For this reason, it is more suitable when calculating the distance between a certain point on the object S or observing the state of the object S.
In addition, since the first off-axis mirror 317 and the second off-axis mirror 349 are provided in the vicinity of the image sensor 2, there is a problem that the incident position of the reference light with respect to the imaging surface of the image sensor 2 is greatly shifted. Absent. On the other hand, since it is devised so that the optical path length of the reference light and the optical path length of the object light sufficiently coincide with each other, highly accurate hologram data can be obtained regardless of the temporal variation of the output of the light source 1. “Fully match” means that there is no problem in terms of coherence even if there is a difference in optical path length.
It is also possible for the apparatus of the first embodiment to use an off-axis mirror to form an off-axis type apparatus. In the case of the first embodiment, the reference light second mirror 332 is changed to an off-axis mirror. Thus, as the off-axis means, one off-axis mirror is sufficient on the optical path of the reference light reaching the image sensor 2.
In principle, it is possible to use an optical element other than the mirror as the off-axis means. For example, an optical element having a function of bending an optical path such as a prism can be placed on the optical path of the reference light so as to be off-axis.

Further, as a configuration other than off-axis, the true image can be separated from the zero-order image and the conjugate image by the phase shift method in the device of the first embodiment and the device of the second embodiment. . In this case, a phase shift element is provided in the reference light guide system 33. As described above, the phase shift element is a piezoelectric element such as a piezoelectric element or an element that can change the optical path length such as an SLM. In the second embodiment, for example, in the second embodiment, the phase shift element is disposed in the additional light guide system 34, and the phase shift element for the transmission mode is guided for the reflected diffracted light. It is arranged in the optical system 31 (however, excluding on the optical path between the object S and the first beam splitter 41. For example, the position between the second mirror 312 and the first beam splitter 41). . The phase shift element in the light guide system 31 for reflected diffracted light is retracted from the optical path in the reflection mode.
When the phase shift method is employed, as described above, the hologram data cannot be obtained substantially in the case where the object S moves. On the other hand, in the apparatus of the first and second embodiments (in-line apparatus) and the apparatus of the third embodiment (off-axis apparatus), hologram data can be obtained even if the object S moves. That is, a reproduced image can be obtained as a moving image. This is also a merit of the apparatus of each embodiment.

Next, a fourth embodiment in which the configuration of the reference light guide system is different will be described. FIG. 14 is a schematic front view of a digital holography device according to a fourth embodiment of the present invention.
As shown in FIG. 14, also in the digital holography device of the fourth embodiment, a reflected diffracted light guide system 31 and a transmitted diffracted light guide system 32 are provided. These

light guide systems

31 and 32 are substantially the same as those of the second embodiment shown in FIG. The fourth embodiment is greatly different from the second embodiment in that the reference light guide system 33 extracts the reference light from the object light and guides it to the image sensor 2.

Specifically, as shown in FIG. 14, in this embodiment, the reference light guide system 33 is disposed on the optical path between the first beam splitter 41 and the imaging device 2. The reference light guide system 33 is provided as an element of one unit 9. This unit 9 is a unit that extracts the reference light from the object light and guides it to the image sensor 2 while guiding the object light to the image sensor 2 (hereinafter referred to as a reference light extraction unit).

As a method for extracting the reference light from the object light, a spatial frequency filtering method is adopted. Of the object light, a portion where the wavefront (amplitude or phase) changes according to the shape, surface state, etc. of the object is a portion having a high spatial frequency. The part where the wavefront changes according to the shape and surface state of the object is the part that can represent the shape and surface state of the object by reproducing the image as described above. It can be said that it is a part including. On the other hand, among the object light, diffracted light emitted from a region where the refractive index is sufficiently uniform can be treated as having the same spatial frequency as the light that does not pass through the object. In other words, light that can represent object information among object light is light having a high spatial frequency, and light that does not include object information (that is, reference light) can be extracted by removing it from the object light. This is the same principle as that of the spatial filter. The reference light extraction unit 9 shown in FIG. 14 is a unit that performs such extraction.

For such a reference light extraction unit 9, several different optical systems are conceivable. Of these, FIG. 15 shows two different examples. FIG. 15 is a schematic front view showing an example of the reference light extraction unit 9 in the embodiment shown in FIG.
The reference light extraction unit 9 shown in FIG. 15A includes a separation element 91 that separates object light and advances it along two different optical axes, and an extraction lens that condenses the light for extracting the reference light. 92, a spatial frequency filter 93 disposed at a condensing position by the extraction lens 92, and a collimator lens 94 for converting the respective lights back into parallel light and integrating them.
As the separating element 91, for example, a diffraction grating can be used as disclosed in JP-A-10-141912, or a polarizing beam splitter can be used as disclosed in JP-A-2006-292939. .

Taking the case where a diffraction grating is used as the separation element 91 as an example, the object light is separated into zero-order diffracted light and first-order diffracted light by the separation element 91. The extraction lens 92 condenses the 0th-order diffracted light and the 1st-order diffracted light, respectively, while the spatial frequency filter 93 has an opening 931 provided at a position on the optical axis where the 0th-order diffracted light is collected, and 1 And a pinhole 932 provided at a position on the optical axis where the next diffracted light is collected. Since the opening 931 is sufficiently large, the object light (0th-order diffracted light) is allowed to pass through as it is without selecting a spatial frequency. On the other hand, since the pinhole 932 is sufficiently small, only a low frequency is allowed to pass through. For this reason, the first-order diffracted light does not include object information. As shown in FIG. 15 (1), these lights are integrated while being returned to parallel light by a collimator lens 94, and are superimposed on the imaging surface of the imaging device 2.

When a polarizing beam splitter is used as the separating element 91, the object light is separated into two polarized lights having polarization directions different by 90 °. For convenience, when the two polarized lights are called first polarized light and second polarized light, the first and second polarized lights are similarly condensed by the extraction lens 92 and reach the spatial frequency filter 93. The structure of the spatial frequency filter 93 is the same as described above. A sufficiently large opening 931 is formed on the optical axis of the first polarized light, and a sufficiently small pin hole 932 is formed on the optical axis of the second polarized light. Is done. The first polarized light passes through the opening 931 without being filtered by the spatial frequency, and enters the image sensor 2 as object light. On the other hand, the second polarized light passes through the pinhole 932 in a state where a component having a high spatial frequency is removed, and becomes the reference light. This light is returned to parallel light together with the first polarized light (object light) by the collimator lens 94 and integrated into the first polarized light. As shown by a dotted line in FIG. 15 (1), when a polarizing beam splitter is used as the separating element 91, a half-wave plate 95 is provided on the exit side of the pinhole 932 of the spatial frequency filter 93. This is to make the polarization state of the reference light coincide with the object light and to enhance the coherence.

The dispersion element 91 may be other than the two examples described above as long as the object light can be separated along the two optical axes. The example shown in FIG. 15 (2) is one of them, and is an example using a normal beam splitter. The object light is separated into two by a separation element 91 (beam splitter), and an extraction lens 92, a spatial frequency filter 93, and a collimator lens 94 are provided on one optical axis. Since the spatial frequency filter 93 is greatly deviated from the other optical axis, an opening for object light is unnecessary, and one light separated by the separation element 91 having a structure having only the pinhole 932 is When passing through the spatial frequency filter 93, a component having a high spatial frequency is removed to become reference light, which is returned to parallel light by the collimator lens 94. Then, it is integrated with the other light (object light) by the integrating beam splitter 96 and enters the image sensor 2.

In the fourth embodiment, unlike the second embodiment shown in FIG. 3, the reflected diffracted light guiding system 31 is not used as the reference light guiding system, so that the second beam splitter 45 is not driven. Instead, the transmission mode and the reflection mode are switched by switching between the two shutters. That is, as shown in FIG. 14, a first shutter 319 is provided on the main optical path P, and a second shutter 327 is provided on the branch optical path Ps. In the transmission mode, the first shutter 319 is closed and the second shutter 327 is opened. In the reflection mode, the first shutter 319 is opened and the second shutter 327 is closed.

In the example shown in FIG. 15 (1), the reference light is incident on the image sensor 2 in an off-axis state with respect to the object light. However, in the example shown in FIG. 15 (2), the reference light is incident in an in-line state. In the example shown in FIG. 15B, when it is desired to be in the off-axis state, a mirror 97 disposed between the collimator lens 94 and the integrating beam splitter 96 is attached with a drive mechanism to form an off-axis mirror. good.
The fourth embodiment is the same as the above-described embodiment except that the structure for obtaining the reference light is different. The reflection mode and the transmission mode can be performed separately, which is suitable for examining the state and shape of the object in detail, and the configuration of the optical system is simplified.
In the optical system shown in FIG. 15 (2), if the difference between the optical path lengths of the object beam and the reference beam becomes a problem in terms of coherence, a mirror is disposed instead of the integrating beam splitter 96. Then, the object light may be folded back, an integration beam splitter may be disposed in place of the mirror 97, and the image sensor 2 may be disposed at a position where the optical axis is linearly extended from the spatial frequency filter 93.

In each of the above-described embodiments, the configuration of the imaging optical system 5 is appropriately changed depending on the type of hologram as described above. In the case of a Fresnel hologram using Fresnel diffraction or a lensless Fourier transform hologram, the imaging optical system 5 may not be provided. In the case of a lensless Fourier transform hologram, the reference light guide system 33 includes a lens that makes the reference light a spherical wave and enters the imaging surface of the imaging device 2.
In each of the above embodiments, the imaging optical system 5 includes the objective lens 51 and the imaging lens 52. However, this is an example, and there may be one lens. Even when two or more lenses are used, an image may be formed on the imaging surface like an image hologram. However, since this is not essential, one lens may not be called the imaging lens 52. , Sometimes referred to as the first objective lens and the second objective lens.

In the apparatus of each of the embodiments described above, the direction in which the reflected diffracted light enters the object S and the direction in which the transmitted diffracted light enters the object S are different by 180 °. However, this is not an essential requirement in the present invention. Considering the optical axis of the linear imaging optical path Pi from the object S to the imaging device 2 as a reference, the reflected diffracted light may be incident obliquely with respect to the optical axis, or the transmitted diffracted light may be used. May be incident obliquely with respect to the optical axis. Accordingly, when the orthogonal coordinates with the position of the object S as the origin are considered and the “first side” is the first and second quadrants, the “second side” is the third and fourth quadrants. It turns out that.

In each of the above embodiments, the light reflected by the first beam splitter 41 reaches the object S in the reflection mode, and the light reflected by the first beam splitter 41 reaches the image sensor 2 as reference light in the transmission mode. . This configuration is not an essential condition in the present invention, and there may be other configurations. That is, the light transmitted through the first beam splitter 41 in the reflection mode may reach the object, and the light transmitted through the first beam splitter in the transmission mode may reach the image sensor as reference light. Specifically, in the reflection mode, the folding mirror is placed at the position where the object S is placed in the second embodiment shown in FIG. 3, and the object is placed at the position where the fourth mirror 341 is placed. In the transmission mode, the image sensor is placed at the position of the fourth mirror 341 without changing the position of the object in the case of FIG. 3, and the first beam splitter is similarly turned 90 °. Even in this way, the present invention can be implemented. However, since the imaging optical path from the object to the imaging device is bent by 90 ° at the first beam splitter 41, it is inferior to the above embodiments in terms of ease of optical axis adjustment and accuracy of the obtained hologram data. .

Although related to the above points, in the second embodiment and the third embodiment, the “first state” and “second state” of the first beam splitter 41 need to be understood in a broad sense. is there. For example, a configuration in which two beam splitters functioning as the first beam splitter are prepared and used separately for the reflection mode and the transmission mode can be considered. As shown in FIG. 7A, a beam splitter having a posture in which the reflecting surface extends obliquely from the upper left to the lower right and a beam splitter in which the reflecting surface extends obliquely from the lower left to the upper right are prepared as shown in FIG. However, a configuration in which the light source is switched on the optical path by an appropriate switching mechanism can be considered. Such a configuration is also within the concept of the “first state” and the “second state”.

DESCRIPTION OF SYMBOLS 1 Light source 2 Image pick-up element 31 Light guide system 32 for reflected diffracted light Light guide system 33 for transmitted diffracted light Reference light guide system 34 Additional light guide system 41 First beam splitter 45 Second beam splitter 5 Imaging optical system 6 Control system 61 control board 62 switching program 63 computer

Claims

Interference between the diffracted light from the object obtained by irradiating the light emitted from the light source on the object and the reference light obtained by guiding the light emitted from the light source without passing through the object on the imaging surface of the image sensor A digital holography method for acquiring hologram data by
When the object from the first side is irradiated with the light from the light source, the reflected diffracted light reflected from the object to the first side and emitted is interfered with the reference light on the image pickup surface of the image pickup device to obtain hologram data. Performing a reflection mode to
When the light from the light source is irradiated on the object from the second side opposite to the first side, the transmitted diffracted light that is transmitted through and emitted from the first side and the reference light are reflected on the imaging surface of the image sensor. And performing a transmission mode of acquiring hologram data by causing interference,
The digital holography method, wherein the step of performing the reflection mode and the step of performing the transmission mode are alternatively selected and performed in different time zones.
The diffracted light from the object obtained by irradiating the object with light emitted from the light source and the reference light extracted from the diffracted light from the object without including object information are caused to interfere with each other on the imaging surface of the image sensor. A digital holography method for acquiring hologram data,
When the object from the first side is irradiated with the light from the light source, the reflected diffracted light reflected from the object to the first side and emitted is interfered with the reference light on the image pickup surface of the image pickup device to obtain hologram data. Performing a reflection mode to
When the light from the light source is irradiated on the object from the second side opposite to the first side, the transmitted diffracted light that is transmitted through and emitted from the first side and the reference light are reflected on the imaging surface of the image sensor. And performing a transmission mode of acquiring hologram data by causing interference,
The digital holography method, wherein the step of performing the reflection mode and the step of performing the transmission mode are alternatively selected and performed in different time zones.
Interference between the diffracted light from the object obtained by irradiating the light emitted from the light source on the object and the reference light obtained by guiding the light emitted from the light source without passing through the object on the imaging surface of the image sensor A digital holography device for acquiring hologram data by
A light guide system for reflected diffracted light that guides light from the light source to the object in order to obtain reflected diffracted light that is diffracted light that is reflected and emitted from the object;
A light guide system for transmitted diffracted light that guides light from the light source to the object in order to obtain transmitted diffracted light that is diffracted light that is transmitted through and emitted from the object;
An imaging device in which the imaging surface is located at a position where the reflected diffracted light can be incident and at which the transmitted diffracted light can be incident;
A reference light guide system that guides light from the light source to the imaging surface of the image sensor without passing through an object,
There is provided a selection optical element for selectively selecting whether to enter the reflection mode by entering the reflected diffracted light on the imaging surface of the image sensor or to enter the transmission mode by entering the transmitted diffracted light.
The light guide system for reflected diffracted light irradiates light from the light source to the object from the first side,
The light guide system for transmitted diffracted light irradiates the object with light from the light source from a second side opposite to the first side,
A digital holography apparatus, wherein an imaging optical path, which is an optical path from the object to an imaging surface of the imaging element, is set on the first side of the object.
The diffracted light from the object obtained by irradiating the object with light emitted from the light source and the reference light extracted from the diffracted light from the object without including object information are caused to interfere with each other on the imaging surface of the image sensor. A digital holography device for acquiring hologram data,
A light guide system for reflected diffracted light that guides light from the light source to the object in order to obtain reflected diffracted light that is diffracted light that is reflected and emitted from the object;
A light guide system for transmitted diffracted light that guides light from the light source to the object in order to obtain transmitted diffracted light that is diffracted light that is transmitted through and emitted from the object;
An imaging device in which the imaging surface is located at a position where the reflected diffracted light can be incident and at which the transmitted diffracted light can be incident;
A reference light guide system that extracts reference light from reflected diffracted light or transmitted diffracted light without including object information and guides it to the imaging surface of the image sensor,
There is provided a selection optical element for selectively selecting whether to enter the reflection mode by entering the reflected diffracted light on the imaging surface of the image sensor or to enter the transmission mode by entering the transmitted diffracted light.
The light guide system for reflected diffracted light irradiates light from the light source to the object from the first side,
The light guide system for transmitted diffracted light irradiates the object with light from the light source from a second side opposite to the first side,
A digital holography apparatus, wherein an imaging optical path, which is an optical path from the object to an imaging surface of the imaging element, is set on the first side of the object.
The digital holography device according to claim 3 or 4, wherein an imaging optical system including a lens is provided on the imaging optical path.
The digital holography device according to claim 5, wherein the imaging optical system shares at least a part of optical elements in the reflection mode and the transmission mode.
The digital holography device according to claim 3, 4, 5, or 6, wherein the imaging optical system is a telecentric optical system.
The digital holography device according to any one of claims 3 to 7, wherein the imaging optical path extends straight from the object to the imaging surface.
The light guide system for reflected diffracted light guides light to the object through the imaging optical path, and includes a first spatial filter on the optical path up to the imaging optical path and the first Comprising zero or only one mirror on the optical path from the spatial filter to the imaging optical path,
The light guide system for transmitted diffracted light includes a second spatial filter and includes zero or only one mirror on the optical path from the second spatial filter to the object. The digital holography device according to claim 3, wherein:
The selection optical element includes a first selection optical element disposed on a main optical path extending from the light source, and the main optical path includes an optical path of the light guide system for the reflected diffracted light and the transmitted diffracted light The first selection optical element branches the light from the light source along the optical path of the reflected diffracted light guide system or the transmitted diffracted light guide light. 10. The digital holography device according to claim 3, wherein the digital holography device selectively selects whether to advance along the optical path of the system.
A first beam splitter is provided on the imaging optical path, the light guide system for reflected diffracted light guides light from a light source to the first beam splitter, and the first beam splitter is 11. The method according to any one of claims 3 to 10, wherein a first state in which light guided by the light guide system for reflected diffracted light is divided in the reflection mode and one of the lights is directed to the object is taken. A digital holography device according to claim 1.
The selection optical element includes a first selection optical element disposed on a main optical path extending from the light source, and the main optical path includes an optical path of the light guide system for the reflected diffracted light and the transmitted diffracted light The first selection optical element branches the light from the light source along the optical path of the reflected diffracted light guide system or the transmitted diffracted light guide light. It is an option to select whether to advance along the optical path of the system,
A first beam splitter is provided on the imaging optical path, the light guide system for reflected diffracted light guides light from a light source to the first beam splitter, and the first beam splitter is Taking a first state in which the light guided by the light guide system for reflected diffracted light in the reflection mode is divided and one of the lights is directed to the object;
The reference light guide system guides the other light divided by the first beam splitter in the reflection mode to the imaging surface of the imaging element without passing through the object,
The first optical element for selection is a second beam splitter, and is provided with a drive unit for changing the arrangement position of the second beam splitter, and the drive unit is a second beam splitter in the reflection mode. In order to prevent light from traveling to the optical path of the transmission diffracted light guide system, the second beam splitter is arranged on the main optical path in the transmission mode. A part of the light is allowed to travel along an optical path of the light guide system for transmitted diffraction light,
The first beam splitter is arranged as a second optical element for selection, and the first beam splitter is provided with a switching unit for changing the state of the first beam splitter,
The switching unit sets the first beam splitter to the first state in the reflection mode, and sets the first beam splitter to the second state in the transmission mode. The second state is guided by the reflected diffracted light guiding system and reaches the first beam splitter so that the reflected diffracted light guiding system is also used as the reference light guiding system. The digital holography apparatus according to claim 3, 5, 6, 7, 8, or 9, wherein the light that has entered is incident on an imaging surface of the imaging device without passing through the object.
In the reflection mode, the reference light guide system transmits the other light that has passed through the first beam splitter and enters the imaging surface of the imaging element via the first beam splitter. Return to the first beam splitter,
There is provided a beam stopper capable of being arranged on the optical path for returning the other light to the first beam splitter, and a stopper driving unit for driving the beam stopper. 13. The digital holography device according to claim 12, wherein the beam stopper is not disposed on the optical path when the beam is stopped, and the beam stopper is disposed on the optical path when the transmission mode is selected.
The reference light guide system emits reference light in a state where a predetermined angle is given with respect to the direction of the reflected diffracted light or the transmitted diffracted light when entering the image pickup surface of the image pickup device. The digital holography device according to claim 3, further comprising an off-axis optical element that is incident on the optical axis.
Off-axis optics that allows reference light to enter the imaging surface of the imaging element in a state where a predetermined angle is given to the direction of the reflected or transmitted diffracted light when entering the imaging surface of the imaging element Elements are provided,
The off-axis optical element includes a first off-axis mirror provided on the optical path in front of the first beam splitter by the reflected diffracted light guiding system, and the reference light guiding system configured to transmit the other light. A second off-axis mirror provided on the optical path when returning to the first beam splitter;
The first off-axis mirror is provided with a drive unit. The drive unit sets the first off-axis mirror in the first posture in the reflection mode and the first off-axis mirror in the transmission mode. The off-axis mirror is in the second position,
The first posture is a posture in which the predetermined angle is not given by the first off-axis mirror, and the second posture is a posture in which the predetermined angle is given by the first off-axis mirror. 14. The digital holography device according to claim 13, wherein the digital holography device is provided.
When the optical path from the first beam splitter toward the light source is traced in the direction opposite to the traveling direction of the light, the first off-axis mirror is an initial mirror;
When the reference light guide system traces the light from the first beam splitter in the direction opposite to the traveling direction on the optical path for returning the other light to the first beam splitter, the second off-axis mirror is 16. The digital holography device according to claim 15, which is the first mirror.