WO2013047709A4

WO2013047709A4 - Digital holography method and digital holography device

Info

Publication number: WO2013047709A4
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: 2013-08-29
Also published as: JPWO2013047709A1; JP5888334B2; JP2016027407A; JP6079839B2; WO2013047709A1

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 device

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

There is a need for a technology that can record and detect three-dimensional information required for detection of defects such as chipping, dents, bulges, and warps and measurement of mechanical vibration, which are difficult to detect with conventional two-dimensional image processing. . Furthermore, there is also a need to acquire three-dimensional information in real time for a moving body such as a living cell. Holography is a technique capable of recording and detecting such three-dimensional information. Conventionally, three-dimensional information is recorded on a high-resolution photographic plate, and a process of developing and reproducing it is necessary. It takes a long time from recording to reproduction, and it is difficult to obtain three-dimensional information of a moving body. The

In recent years, digital holography has been proposed that can be measured at high speed by introducing to the holography the evolution of electronics technology, such as speeding up of computers, increasing the capacity of storage devices, and increasing the resolution and pixels of imaging devices such as CCDs. ing. In this technology, interference fringes are imaged by an imaging device, and a computer performs numerical calculation processing based on the light diffraction phenomenon on the image data of the interference fringes to reproduce a three-dimensional image of an object on the computer. It is.
Digital holography 1) does not require development processing, and a reproduced image can be obtained at the shooting site, 2) a reproduced image on an arbitrary surface can be obtained with image data of one interference fringe, 3) hologram data (of interference fringes Image data) can be easily transmitted and copied. Taking advantage of these advantages, researches aiming at three-dimensional measurement of solid, fluid, living cell, mechanical vibration and the like using digital holography technology are actively conducted.

FIG. 16 is a schematic view of a conventional digital holography device. In the digital holography device, a half mirror 72 splits the light emitted from the light source 71 into a reference light and a light for object illumination. The light for object irradiation divided by the half mirror 72 is irradiated to the object 74 through the reflection mirror 73, and the object light 75 is emitted from the object 74. The object beam 75 is incident on the beam splitter 76. On the other hand, the reference light split by the half mirror 72 is reflected by the reflection mirror 77 and enters the beam splitter 76.
Then, when the object light transmitted through the beam splitter 76 and the reference light reflected by the beam splitter 76 simultaneously enter the imaging surface of the CCD camera 78, the interference fringes generated by overlapping the object light and the reference light are captured. And hologram data is obtained. A reproduced image of the object 74 is obtained by performing calculation processing such as Fresnel transformation with a computer (not shown) on the obtained hologram data.

Object light is light emitted from an object irradiated with light, and in holography, a diffraction phenomenon is used, and therefore, it means diffracted light emitted from an object. The device shown in FIG. 16 is a device in transmission mode, and the transmission diffraction light is object light. The transmission mode is a mode for capturing an interference fringe of reference light and diffracted light (transmission diffracted light) that is transmitted through the object when the object is irradiated with light.
In holography, a plane wave is generally used for the purpose of enhancing the coherency of the object light and the reference light. The same applies to digital holography, and as a light source, one emitting a plane wave such as a laser is used.

Many conventional digital holography devices are devices called in-line type, and hologram data is obtained by making the reference beam perpendicularly incident on the imaging plane as well as the object beam, in consideration of the resolution limit of the imaging device. There is. Therefore, the zero-order image and the conjugate image overlap with the reproduced image obtained by calculation processing of the hologram data, making it difficult to obtain a clear reproduced image.
Therefore, digital holography devices using phase shift interferometry have been proposed. Phase shift interferometry is an arrangement of a piezoelectric element such as a piezo element or an element such as a SLM (Spatial Light Modulator) that can change the optical path length in the optical path of a reference beam in a two-beam interferometer. This method is a method of obtaining hologram data while changing the phase of the reference light, for example, in three or more steps by this element. In the digital holography device using such phase shift interferometry, a clear image is obtained by removing the zero-order light and the conjugate image, and high-precision measurement is possible.
However, phase shift interferometry can not be applied to a moving object because it captures an interference fringe while sequentially changing the phase of the reference light by 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 reference light, and a Mach-Zehnder interferometer that forms an image in a transmission mode using the element. The configured digital holography device is shown. As in the document, by spatially dividing and recording the interference state of the object light and the reference light, it is possible to measure the dynamic shape even with the imaging of a single image.

Further, in Patent Document 2 (Japanese Patent Application Publication No. 2002-526815), there is a method of imaging a single interference fringe image and obtaining an amplitude image and a phase image of an object by applying the principle of off-axis digital holography. It is disclosed. In this method as well, since it is sufficient to capture a single image, it is possible to measure the shape even if the object is moving (to measure the dynamic shape).
The document shows a digital holography device consisting essentially of a Michelson interferometer 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 as object light on an imaging surface of an imaging device to interfere with reference light.

As shown in FIG. 2B of the document, light emitted from the light source is spread in the diametrical direction and enters the beam splitter. The light incident on the beam splitter is split into one light passing through the beam splitter and the other light reflected by the beam splitter. One of the lights is reflected by the inclined mirror, and then enters the beam splitter, is reflected by the beam splitter, and is imaged as the reference light. The other light is irradiated to the sample through the objective lens, and is reflected by the sample to become object light. The object light is incident on the beam splitter and transmitted through the beam splitter for imaging. An off-axis hologram can be recorded by causing the reference light to interfere with the object light at a predetermined angle using the inclined mirror.

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

Patent No. 4294526 Japanese Patent Publication No. 2002-526815 WO 2008/123408

As described above, digital holography is expected to be applied to observation and three-dimensional measurement of various objects, but there are various objects to be observed and measured. Thus, there are objects suitable for reflection mode digital holography and transmission mode digital holography. In addition, it may be better to perform both the reflection mode and the transmission mode for one object.
However, as seen in Patent Document 2, as a conventional digital holography device, there is only one device that can operate only in the reflection mode and another device that can operate only in the transmission mode, and both modes can be used. There was no digital holography device that could operate at. Therefore, when trying to perform both the reflection mode and the transmission mode for one object, it was necessary to prepare both the reflection mode device and the transmission mode device.

Patent Document 3 (WO2008 / 123408) is known as the only device that can perform both the reflection mode and the transmission mode. FIG. 17 is a view showing a digital holography device disclosed in Patent Document 3. As shown in FIG. As shown in FIG. 17, in Patent Document 3, a first optical system 110 for emitting light to an object 119, and a second optical system for guiding diffracted light emitted from the object 119 and reference light to an imaging device A digital holography device including an imaging device 165 for capturing an interference image of diffracted light and reference light, and a processing device 201 for generating a three-dimensional image of an object from the interference image for each irradiation direction acquired by the imaging device 165 Is disclosed. In the imaging device 165, an imaging device for transmission diffraction light and an imaging device for reflection diffraction light are separately provided, and hologram data is separately acquired by the imaging device for transmission diffraction light and the imaging device for reflection diffraction light.

However, the digital holography device disclosed in Patent Document 3 has the following problems.
FIG. 18 is a schematic view showing the problem of the digital holography device of Patent Document 3. As shown in FIG. As shown in FIG. 18 (1), in the digital holography device of Patent Document 3, the side of the object 119 to which light (plane wave) is irradiated to obtain diffracted light is limited to one side of the object 119. It is an apparatus capable of emitting light only from one side of the object 119, and the diffracted light (reflected diffracted light) emitted from one side and reflected to one side is one side of the first objective lens 117. And the diffracted light (transmission diffracted light) transmitted to the other side is allowed to reach the transmission diffracted light imaging device through the other 121 of the first objective lens. As described above, the reason for irradiating light only from one side of the object 119 is considered to be to simultaneously capture the interference fringes by the reflected diffraction light and the interference fringes by the transmission diffraction light.

As can be understood from FIG. 17, the object can not but be regarded as floating in the air. However, in reality, light is emitted while an object is placed on something like a container or pedestal, and hologram data is acquired. For example, as shown in FIG. 18 (2), the object S is placed on a transparent glass petri dish 81 and irradiated with light in consideration of light transmission.
In this case, although there is no problem with the transmitted diffracted light, the reflected diffracted light is captured through the petri dish 81 for the reflected diffracted light. Therefore, spherical aberration occurs under the influence of the thickness and refractive index of the petri dish 81. FIG. 18B shows how the transmission diffracted light propagates in a state different from the original state depending on the thickness and refractive index of the petri dish 81. Because of such spherical aberration, the apparatus of Patent Document 3 can not obtain hologram data with high accuracy. If the object can be kept floating in the air, it may be possible to avoid problems, but it is impossible when observing microscopic things such as bacteria, and it is soft. In the case of an object, since holding and holding it from both sides causes deformation and breakage, it is also 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, it is not possible to observe the object in reflection mode or in transmission mode from the same side of the viewpoint. The device of Patent Document 3 can not be used 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.
Thus, the device of Patent Document 3 can not be said to be a practical device for obtaining highly accurate hologram data.

Also, in order to obtain highly accurate hologram data, 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 view of a spatial filter.
The spatial filter is composed of a lens 82 and a pinhole plate 83, as shown in FIG. And the like to remove the noise generated. For example, if dust adheres to or is scratched on the surface of a mirror that reflects light, the wavefront may be disturbed by scratches or dust, or interference fringes may occur due to the effects of scratches or dust It becomes impossible to obtain high-precision hologram data of only interference fringes due to light. In order to prevent this problem, it is desirable to use a spatial filter.

It is desirable to place the spatial filter as close to the object as possible in the light path of the light emitted to the object. If the spatial filter is disposed on the optical path away from the object, and an optical element such as a lens or a mirror is further disposed between the spatial filter and the object, dust on the surface of these optical elements or The effects of scratches can not be removed.
Here, in FIG. 17 (patent document 3), it is conceivable to dispose a spatial filter on an optical path close to the object 119, for example, between the mirror 115 and the object 119. However, this location is also the optical path of the reflected diffraction light reflected from the object 119. If the spatial filter is disposed here, the reflected diffraction light can not pass through the pinhole of the spatial filter, so that a problem occurs in that the imaging reflection device 165 can not capture the reflected diffraction light.

In order to avoid the above problem in FIG. 17, the spatial filter must be separated to a position where the light path of the irradiation light and the light path of the reflected diffraction light are separated. Even if the position closest to the object 119 is selected, it means the position between the mirror 105 and the beam splitter 107. Even when the spatial filter is disposed at this position, 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 placing a spatial filter. That is, using the spatial filter to obtain high-precision hologram data is substantially impossible with the device of Patent Document 3.

The present invention has been made to solve such problems, and it is an object of the present invention to first provide a practical digital holography method that performs both reflection mode and 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.
The third object of the present invention is to make it possible to acquire highly accurate hologram data without leaving the object in the air.
The 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 problems, the invention according to claim 1 of the present application is to transmit diffracted light from an object obtained by irradiating the object with light emitted from a light source and light emitted from a light source through the object. A digital holography method for acquiring hologram data by causing interference with a reference light obtained by guiding the light without using the light from the reference light and obtaining the hologram data.
When the light from the light source is irradiated to the object from the first side, the refracted diffracted light reflected from the object and emitted from the object to the first side interferes with the reference light at the imaging surface of the imaging element to acquire hologram data Performing a reflection mode to
When the object is irradiated with light from the light source from the second side opposite to the first side, the transmission diffracted light transmitted and emitted to the first side and the reference light are taken on the imaging surface of the imaging device Performing a transmission mode of causing interference to acquire hologram data;
The step of performing the reflection mode and the step of performing the transmission mode may be alternatively selected and performed in different time zones.
Further, in order to solve the above problems, the invention according to claim 2 does not include object information from diffracted light from an object obtained by irradiating the object with light emitted from a light source and diffracted light from an object A digital holography method of acquiring hologram data by causing interference with a reference light extracted in a state on an imaging surface of an imaging device,
When the light from the light source is irradiated to the object from the first side, the refracted diffracted light reflected from the object and emitted from the object to the first side interferes with the reference light at the imaging surface of the imaging element to acquire hologram data Performing a reflection mode to
When the object is irradiated with light from the light source from the second side opposite to the first side, the transmission diffracted light transmitted and emitted to the first side and the reference light are taken on the imaging surface of the imaging device Performing a transmission mode of causing interference to acquire hologram data;
The step of performing the reflection mode and the step of performing the transmission mode may be alternatively selected and performed in different time zones.
Further, in order to solve the above-mentioned problems, the invention according to claim 3 is to transmit diffracted light from an object obtained by irradiating the object with light emitted from the light source and light emitted from the light source through the object. A digital holography apparatus for acquiring hologram data by causing interference with a reference light obtained by guiding a light beam at the imaging surface of an imaging device,
A light guide system for reflected diffracted light, which guides light from a light source to an object to obtain reflected diffracted light which is diffracted light emitted by reflecting light to the object;
A light guiding system for transmitting diffracted light that guides light from a light source to the object to obtain transmitted diffracted light that is diffracted light that is emitted by transmitting light through the object;
An image pickup element whose position where the reflected diffracted light can be incident and whose imaging surface is located at the position where the transmitted diffracted light can be incident;
And a reference light guide system for guiding the light from the light source to the imaging surface of the imaging device without passing through the object,
A selection optical element is provided to select alternatively whether the reflection diffracted light is made incident on the imaging surface of the imaging device to make the reflection mode or the transmission diffraction light made to make the transmission mode,
The light guide system for reflected diffraction light irradiates light from the light source to the object from a first side,
The light guide system for transmission diffraction light irradiates the light from the light source to the object from the second side opposite to the first side,
The imaging optical path, which is an optical path from the object to the imaging surface of the imaging device, is configured to be set on the first side of the object.
Further, in order to solve the above problems, the invention according to claim 4 does not include object information from diffracted light from an object obtained by irradiating the object with light emitted from a light source and diffracted light from an object A digital holography apparatus for acquiring hologram data by causing interference with a reference light extracted in a state on an imaging surface of an imaging device,
A light guide system for reflected diffracted light, which guides light from a light source to an object to obtain reflected diffracted light which is diffracted light emitted by reflecting light to the object;
A light guiding system for transmitting diffracted light that guides light from a light source to the object to obtain transmitted diffracted light that is diffracted light that is emitted by transmitting light through the object;
An image pickup element whose position where the reflected diffracted light can be incident and whose imaging surface is located at the position where the transmitted diffracted light can be incident;
And a reference light guiding system for extracting the reference light from the reflection diffraction light or the transmission diffraction light without including the object information and guiding the reference light to the imaging surface of the imaging device,
A selection optical element is provided to select alternatively whether the reflection diffracted light is made incident on the imaging surface of the imaging device to make the reflection mode or the transmission diffraction light made to make the transmission mode,
The light guide system for reflected diffraction light irradiates light from the light source to the object from a first side,
The light guide system for transmission diffraction light irradiates the light from the light source to the object from the second side opposite to the first side,
The imaging optical path, which is an optical path from the object to the imaging surface of the imaging device, is configured to be set on the first side of the object.
Furthermore, in order to solve the above-mentioned problems, the invention according to claim 5 has a configuration in which an imaging optical system including a lens is provided on the imaging light path in the configuration according to claim 3 or 4.
In order to solve the above problems, the invention according to claim 6 is the configuration according to

claim

3, 4 or 5, wherein the imaging optical system is at least a part of optical elements in the reflection mode and the transmission mode. Are shared.
Further, in order to solve the above-mentioned problems, the invention according to claim 7 has a construction in which the imaging optical system is a telecentric optical system in the construction according to

claim

3, 4, 5 or 6.
In order to solve the above problems, the invention according to claim 8 is the constitution according to any one of claims 3 to 7, wherein the imaging light path extends in a straight line from the object to the imaging surface. Have.
Further, in order to solve the above-mentioned problems, the invention according to claim 9 relates to the configuration according to any one of claims 3 to 8, wherein the light guiding system for reflected diffraction light guides light to the object through the imaging light path. A first spatial filter provided on the optical path to the imaging optical path and only zero or one optical path on the optical path from the first spatial filter to the imaging optical path Has a mirror,
The light guiding system for transmitted diffracted light comprises a second spatial filter and also has zero or only one mirror on a light path from the second spatial filter to the object. It has composition.
Further, in order to solve the above-mentioned problems, the invention according to claim 10 is characterized in that, in the configuration according to any one of claims 3 to 9, as the selection optical element, a first optical path disposed on a main optical path extending from the light source. An optical element for selection is provided, the main optical path is branched into an optical path of the light guide system for reflected diffraction light and an optical path of the light guide system for transmission diffraction light, and the first optical element for selection is It is alternatively selected whether the light from the light source is made to travel along the light path of the light guide system for reflection diffraction light or along the light path of the light guide system for transmission diffraction light. Have.
In order to solve the above-mentioned subject, in the invention according to claim 11, in the configuration according to any one of claims 3 to 10, a first beam splitter is provided on the imaging light path, and the reflected diffracted light The light guiding system for guiding light from the light source to the first beam splitter, and the first beam splitter divides the light guided by the light guiding system for reflected diffraction light in the reflection mode. It has a configuration that it takes a first state in which one of them is directed to the object.
Further, in order to solve the above-mentioned problems, the invention according to claim 12 is characterized in that, in the configuration according to

claim

3, 5, 6, 7, 8, or 9, on the main optical path extending from the light source as the selection optical element. A first selection optical element is disposed, and the main optical path is branched into an optical path of the light guiding system for the reflected diffracted light and an optical path of the light guiding system for the transmitted diffracted light, The selection optical element alternatively selects whether the light from the light source is allowed to travel along the light path of the light guide system for reflected diffraction light or along the light path of the light guide system for transmission diffracted light To be
A first beam splitter is provided on the imaging optical path, the light guide system for reflected diffraction light is for guiding light from a light source to the first beam splitter, and the first beam splitter is It takes a first state in which light guided by the light guide system for reflected diffraction light is divided in the reflection mode and one of the lights is directed to the object,
The reference light guiding system is for guiding the other light split by the first beam splitter to the imaging surface of the imaging device without passing through the object in the reflection mode.
The first selection optical element is a second beam splitter, and a drive unit for changing the arrangement position of the second beam splitter is provided, and the drive unit performs the second operation in the reflection mode. The second beam splitter is disposed on the main optical path in the transmission mode while the light is prevented from advancing to the optical path of the light guiding system for transmission diffraction light by setting the beam splitter at a position deviated from the main optical path. A part of the light is made to travel along the light path of the light guide system for transmission diffraction light,
The first beam splitter is disposed as a second selection optical element, and the first beam splitter is provided with a switching unit that changes 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. And the second state is guided by the light guiding system for reflected light and reaches the first beam splitter so that the light guiding system for reflected light is also used as the light guiding system for reference light. Light is incident on the imaging surface of the imaging device without passing through the object.
In order to solve the above problems, the invention according to claim 13 is the structure according to claim 12, wherein the reference light guiding system transmits the first beam splitter in the reflection mode. Is for returning the other light to the first beam splitter so as to be incident on the imaging surface of the imaging element through the first beam splitter,
A beam stopper capable of being disposed on the optical path for returning the other light to the first beam splitter, and a stopper driving unit for driving the beam stopper are provided, and the stopper driving unit is in the reflection mode. In this case, the beam stopper is not disposed on the optical path, and in the transmission mode, the beam stopper is disposed on the optical path.
Further, in order to solve the above problems, the invention according to claim 14 is the configuration according to claims 3 to 12, wherein the reference light guiding system is the reflected diffracted light or the reflected diffracted light when entering the imaging surface of the imaging device. An off-axis optical element for causing reference light to be incident on the imaging surface of the imaging device in a state in which a predetermined angle is given to the direction of the transmission diffracted light is provided.
In order to solve the above problems, the invention according to claim 15 is the structure according to claim 13 with respect to the direction of the reflected diffraction light or the transmission diffraction light when entering the imaging surface of the imaging device. An off-axis optical element is provided for causing reference light to be incident on the imaging surface of the imaging device in a state where a predetermined angle is given,
The off-axis optical element includes a first off-axis mirror provided with the light guide system for reflected diffraction light on the light path in front of the first beam splitter, and the reference light guide system uses the other light as the first light A second off-axis mirror provided on the light path when returning to the 1 beam splitter,
The first off-axis mirror is provided with a drive unit, and in the reflection mode, the drive unit sets the first off-axis mirror in the first posture, and in the transmission mode, the first off-axis mirror. 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 There is a configuration that there is.
Further, in order to solve the above problems, the invention according to claim 16 follows the optical path from the first beam splitter toward the light source in the configuration according to claim 15 in the direction opposite to the traveling direction of light. Said first off axis mirror is the first mirror,
When the reference light guiding system traces the other light back to the first beam splitter from the first beam splitter in the direction opposite to the light traveling direction, the second off-axis mirror It has a configuration of being the first mirror.

As described below, according to the invention of

claim

1 or 2 of the present application, hologram data can be obtained for each object from reflected and transmitted diffracted light, so the state, shape, etc. of the object are examined in detail. Would be suitable for At this time, since the reflection mode and the transmission mode are separated in time, the configuration of the optical system is simplified. Further, according to the first aspect of the present invention, since the reference light is guided to the imaging device without passing through the object, the reference light which is always stable can be obtained regardless of the condition of the object. Therefore, highly accurate hologram data can be acquired.
Further, according to the invention of claim 3 or 4, since hologram data can be obtained for each object by reflected and transmitted diffracted light respectively, it is suitable for examining in detail the state, shape, etc. of the object. It becomes a thing. At this time, since the reflection mode and the transmission mode are separated in time, the configuration of the optical system is simplified. Further, since the reflection mode and the transmission mode can be performed by one device, it is preferable in terms of workability as well as cost merits. Furthermore, even when an object is placed in a transparent container, highly accurate hologram data can be obtained, and observation in the reflection mode and observation in the transmission mode can be performed from the same viewpoint. Further, according to the third aspect of the invention, the reference light is guided to the imaging device without passing through the object, so that the stable reference light can be obtained regardless of the condition of the object. Therefore, highly accurate hologram data can be acquired.
Further, according to the sixth aspect of the invention, in addition to the above effects, the imaging optical system shares at least a part of the optical elements, so 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 effects, the imaging optical system is a telecentric optical system, so it is possible to irradiate an object with a plane wave both in the reflection mode and in the transmission mode. For this reason, the object light is not distorted, and the correction calculation becomes unnecessary.
Further, according to the invention of claim 8, in addition to the above effect, the imaging optical path extends in a straight line from the object to the imaging surface, so the configuration of the optical system becomes simple, and the disturbance of the wavefront is Less. For this reason, it can contribute to acquisition of hologram data with higher accuracy, and the cost also becomes cheaper.
According to the invention of claim 9, in addition to the above effect, since the spatial filter is used, more accurate hologram data can be obtained. And since the spatial filter is located on the light path closer to the object, the effect of the accuracy improvement is higher.
Further, according to the invention of claim 12, in addition to the above effects, the light guide system for reflected diffracted light is also used as the reference light light guide system, so that the coherence of light is improved, and in this respect it is more accurate High hologram data can be acquired.
Further, according to the invention of claim 13, in addition to the above effect, in the reflection mode, the reference light guiding system returns the light to the first beam splitter and passes the first beam splitter to the light into the imaging device Since the light is guided, the coherence of light is further improved at this point, and more accurate hologram data can be obtained.
Further, according to the invention of claim 14 or 15, in addition to the above-mentioned effect, since the optical element for off-axis is provided, the off-axis type operation becomes possible. Therefore, image reproduction can be performed in a state where the true image is separated from the zero-order image and the conjugate image.
Further, according to the invention of claim 16, since the off-axis mirror is provided at a position close to the imaging device, the incident position of the reference light with respect to the imaging surface of the imaging device will not be largely deviated.

It is the figure which showed the digital holography method concerning the embodiment of the present invention notionally. FIG. 1 is a front schematic view of a digital holography device of a first embodiment of the present invention. FIG. 5 is a front schematic view of a digital holography device of a second embodiment of the present invention. FIG. 7 is a schematic view showing a second beam expander 321 and a second spatial filter 326. It is the schematic which showed typically 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 the operation | movement of the apparatus of 2nd Embodiment, and is the figure shown contrasting about the advancing condition of each light in reflective mode and transmissive mode. It is the figure which showed the outline of the operation flow in reflective mode. It is the figure which showed the outline of the operation 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 5. FIG. FIG. 5 is a front schematic view 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 | positioning 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 contrasting about the advancing condition of each light in reflective mode and transmissive mode. It is a front schematic diagram of the digital holography apparatus 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 spatial filter.

Next, modes (hereinafter, embodiments) for carrying out the present invention will be described.
FIG. 1 is a conceptual view of 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 as the object S This is a method of acquiring hologram data by causing interference with the reference light obtained without guidance through the imaging surface of the imaging device 2.

One of the major feature points of this method is that, among the light irradiated to the object S, the object light (reflected diffracted light) which is reflected on the object S and proceeds to become diffracted and interferes with the reference light on the imaging surface Among the light emitted to the object S, the object light (transmission diffracted light) that travels through the object S and travels as diffracted light and the reference light interfere with each other on the imaging surface to obtain hologram data The point is that it is a method of performing the transmission mode, and the point that 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 step of the reflection mode or the step of the transmission mode may come first. The point is to obtain hologram data using reflected diffraction light without using transmitted diffraction light, and obtaining hologram data using transmission diffraction light without using reflected diffraction light. Is done at different time zones, not simultaneously.

Another major feature of the digital holography method of the embodiment is that the manner of the light irradiation to the object S is different between the reflection mode and the transmission mode. That is, as shown in FIG. 1 (1), in the reflection mode, the object S is irradiated with the light from the light source 1 from the first side. On the other hand, as shown in FIG. 1 (2), in the transmission mode, the object S is irradiated with light from the second side opposite to the first side. Then, in the reflection mode, the diffracted light reflected to the first side is made incident on the imaging device 2, and in the transmission mode, the diffracted light transmitted to the first side is made incident to the imaging device 2. That is, the side of imaging by the imaging device 2 is the same in the reflection mode and the transmission mode.

Next, the digital holography apparatus of each embodiment used to implement the digital holography method of the above embodiment will be described. First, the digital holography device of the first embodiment will be described. FIG. 2 is a front schematic view of the digital holography device of the first embodiment.
As shown in FIG. 2, in the digital holography device of the first embodiment, a light guide system 31 for reflected diffracted light that guides light from a light source 1 to an object S to obtain reflected diffracted light, and transmitted diffracted light And a reference light guiding system 33 for guiding the light from the light source 1 to the imaging surface of the image sensor 2 without passing through the object S, and a reflection The imaging device 2 is provided with an imaging surface at a position where the diffracted light and the reference light interfere with each other and the transmission diffracted light and the reference light interfere with each other. Then, in this device, there is a selection optical element which selects alternatively whether the reflection diffracted light is made incident on the imaging surface of the imaging device 2 to make the reflection mode or the transmission diffraction light made to make the transmission mode. It is provided.

As described above, in the reflection mode or the transmission mode, the object light is emitted to the same first side. Therefore, the imaging element 2 is provided on the imaging light path Pi set on the first side. A first beam splitter 41 is provided on the imaging light path Pi. In order to irradiate the object S with light for reflected diffraction light through the imaging light path Pi, the first beam splitter 41 is disposed in the middle of the imaging light path Pi, and light for reflected diffraction light is introduced therefrom. There is.
Further, in this embodiment, an imaging optical system 5 including a lens is provided on the imaging light path Pi. The imaging optical system 5 is not necessary when the imaging element 2 is relatively close to the object S and Fresnel diffraction is used (in the case of Fresnel hologram). Further, also 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 unnecessary. When the imaging optical system 5 is required, it is a Fraunhofer hologram (Fourier transform hologram) using a lens, or an interference image by diffracted light from the object S as an enlarged image or a reduced image. .

In order to obtain a clear hologram reproduction image, it is necessary that the object light and the reference light sufficiently interfere with each other to form interference fringes. For this purpose, the light source 1 needs to be in phase (coherent) at a single wavelength. 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 separate light sources for the object light and the reference light, it is very difficult to sufficiently align the wavelength and phase when using separate 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 of the lights is used as a reference light.

The selection optical element 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 light extraction beam splitter 42 to the light guide system 31 for reflection diffraction light or the light guide system 32 for transmission diffraction light. It has become like.
Note that this embodiment is an in-line type apparatus, and the reference light is also vertically incident on the imaging surface of the imaging device 2 like the object light. As shown in FIG. 1, the integration beam splitter 44 is disposed on the imaging light path Pi, and the reference light is reflected by the integration beam splitter 44 and vertically incident on the imaging surface of the imaging device 2. ing. The reference light guiding system 33 includes a first mirror for reference light 331 and a second mirror for reference light 332, and the beam splitter 44 for integrating the light extracted by the beam splitter for extracting reference light 42 is provided. It leads to

In the method and apparatus of the embodiment, the object S is placed in a container such as a petri dish to obtain its hologram data. The light source 1 is operated to first obtain hologram data in, for example, the reflection mode, and then move the movable mirror 43 to obtain the hologram data in the transmission mode. Each hologram data is processed by a computer (not shown in FIG. 1) to which the imaging element 2 is connected. A predetermined program (hereinafter referred to as an image reproduction program) for obtaining a reproduced image from hologram data is installed in the computer, and the reproduced image is displayed on the display by executing the image reproduction program, or the object S is displayed. It is possible to measure the distance of a specific part of or to display the reflectance distribution or transmittance distribution of the object S.
According to the method and apparatus of such an embodiment, since hologram data can be obtained for each object S by reflected and transmitted diffracted light respectively, it is suitable for examining the state and shape of the object S in detail. 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 separated in time, the configuration of the optical system is simplified. Even with the configuration as shown in FIG. 15, the hologram data by the reflection diffraction light and the hologram data by the transmission diffraction light can be obtained. However, in the configuration of FIG. 15, the reflection diffraction light and the transmission diffraction light simultaneously come out of the object. Therefore, it is necessary to separate them and make them incident on the respective imaging elements. For this reason, a complex imaging optical system 5 is required. In fact, FIG. 15 shows a complex imaging optical system using a polarization beam splitter 143 or 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 separated temporally, optical separation is unnecessary. Therefore, the imaging optical system 5 is simplified. The fact that the imaging optical system 5 is simplified has the advantage of cost and the possibility of disturbance of the wavefront due to the use of more optical elements is reduced, so that more accurate hologram data can be obtained. It has the advantage of

Further, as shown in FIG. 15, to simultaneously perform the reflection mode and the transmission mode means that light is irradiated to the object S from one side, and the reflection diffracted light that is reflected and emerges to one side is to the other side It means that the transmitted diffracted light that has been transmitted and captured is captured by the imaging device. In this case, as described above, unless the object S is configured to be floated and held in the air, it is not possible to obtain highly accurate hologram data. However, when the reflection mode and the transmission mode are performed separately in time, light can be emitted from the opposite side in the transmission mode, and the side to be imaged may be the same side of the object S. it can. Therefore, even when the object S is placed in a container such as a petri dish, high-precision hologram data can be obtained, and observation in the reflection mode and observation in the transmission mode can be performed from the same viewpoint. The device of the embodiment is such a device.

Performing the reflection mode and the transmission mode is suitable for examining in detail the state, shape, etc. of the object S as described above, but it is possible to perform this in one device, in addition to cost merits, workability Is also preferable. The same thing can be done by preparing a digital holography device that performs measurement in the reflection mode and a digital holography device that performs measurement in the transmission mode. In this case, the object S is taken out after the measurement is performed by the device in the reflection mode. , It has to be set in the transmission mode device to perform measurement, which is complicated. According to the apparatus of this embodiment, there is no such problem.
Generally speaking, when the object S is an opaque body, it is impossible to acquire hologram data in the transmission mode in the first place. In the case of a transparent body, data acquisition can be performed in transmission mode or in reflection mode, but when reflection mode is performed on a transparent body, reflection diffraction light from the surface of the object interferes with reflection diffraction light from the back surface of the object. Interference fringes may occur, and accurate hologram data may not be obtained due to this effect. If these are considered, the merit that the mode can be arbitrarily selected with one device according to the property of the object S which is a target object is very large.

Further, the point in which the reference light is guided to the imaging device 2 without passing through the object S is excellent in that a stable reference light is always obtained regardless of the condition of the object S. In FIG. 15, light transmitted through the object S is taken out as reference light. As described above, it is not impossible to make the reference light incident on the imaging element 2 along the same route as that of the object light such as light irradiation on the object S → object light → imaging element 2. However, in such a case, the reference light is changed depending on the optical physical properties of the object S, so that it is not always possible to use stable light as the reference light. On the other hand, if the reference light is guided to the imaging device 2 without passing through the object S as in the present embodiment, the reference light does not change depending on the conditions of the object S, and the reference light is always stabilized. it can. For example, when measuring the light transmittance from the object S, according to the method or apparatus of the present embodiment, there is a merit that quantitative data can be obtained.

Next, the digital holography device of the second embodiment with further enhanced practicality will be described below. FIG. 3 is a front schematic view of a digital holography device of a second embodiment of the present invention.
The digital holography device of the second embodiment includes a light guiding 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 light guide system 32 for transmitted diffracted light that guides light to the object S, a reference light 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, reflected diffracted light and reference light Whether the reflected diffraction light is incident on the imaging surface of the imaging element 2 and the imaging surface of the imaging element 2 where the imaging surface is located at the interference position and the interference position of the transmission diffraction light and the reference light And a control system (not shown in FIG. 3) for controlling the operation of the selection optical element.

In the second embodiment, in order to enhance the practicability of the apparatus, the light guide system 31 for reflected diffraction light is used in part as a reference light guide system. Specifically, in the second embodiment, the second beam splitter 45 is provided instead of the movable mirror 43 in the first embodiment. A drive unit 451 is attached to the second beam splitter 45. The first beam splitter 41 is provided as in the first embodiment, but the switching unit 411 is attached to the first beam splitter 41 as a drive mechanism. The first beam splitter 41 and the second beam splitter 45 function as selection optical elements.

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

Further, each of the light guide systems 32 for transmission diffraction light is disposed on an optical path (hereinafter referred to as a branched optical path) Ps which is formed separately from the main optical path by positioning the second beam splitter 45 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, and the like.
The third mirror 322 bends the branched light 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 passes through the second beam expander 321, is reflected by the third mirror 322, and reaches the object S. This light passes through the object S and becomes transmission diffracted light.
The drive unit 451 provided in the second beam splitter 45 arranges the second beam splitter 45 on the main optical path to split the light, and a retraction position where the light is retracted from the main optical path so as not to split the light. And a mechanism for moving the second beam splitter 45 between them. Thus, the second beam splitter 45 functions as a selection optical element. The drive unit 451 is configured of, for example, a linear motion type stage such as a linear stage.

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 is in the same state as the first beam splitter 41 in the first embodiment, that is, the light guided by the light guide system 31 for reflected diffraction light is The attitude toward the object S by reflection (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 light guide system 31 for reflected diffraction light, and causes the light to enter the imaging element 2 as it is. The posture (hereinafter, referred to as a second state). That is, in the transmission mode, the switching unit 411 prevents the light from the light source 1 from being irradiated to the object S from the opposite side, and the light guiding system 31 for reflected diffraction light functions as the reference light guiding system 33 It plays two roles. Such a switching unit 411 is configured of, for example, a rotation stage. The rotation axis is on a straight line perpendicular to the optical axis and passing through the center of the reflective surface of the first beam splitter 41 and along the reflective surface.

As can be understood from the above description, the reference light guiding 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 transmission mode, the reference light guiding system 33 guides the reference light to the imaging element 2 using a part of the above-described light guide system 31 for reflected diffracted light. That is, the reference light guiding system 33 in the transmission mode is configured by 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 light guide system 31 for reflection diffracted light, which is shared in the same manner, and the additional light guide system 34. In the reflection mode, the first beam splitter 41 advances one of the split lights towards the object S. The additional light guiding system 34 guides the other light split by the first beam splitter 41 to the imaging element 2. In the present embodiment, the additional light guiding system 34 returns the other light to the first beam splitter 41 so as to lead through the same path as much as possible. It is made to inject into an imaging surface as a reference light.

More specifically, in the reflection mode, the reference light guiding system 33 includes the first mirror 46, the first beam expander 311, the second mirror 312, and the first beam splitter 41; It is comprised by the additional light guide system 34. The additional light guiding system 34 is configured of a fourth mirror 341, a folding mirror 342, and the like. The fourth mirror 341 bends the light from the second beam splitter 45 by 90 °, and the folding mirror 342 bends the light by 180 ° and folds it back.
A beam stopper 343 and a stopper driving unit 344 for driving 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 stop the light so as not to turn back because the additional light guiding system 34 is unnecessary in the transmission mode.

In the digital holography device of this embodiment, the first spatial filter 316 and the second spatial filter 326 are arranged in order to obtain accurate hologram data. The first spatial filter 316 and the second spatial filter 326 are respectively disposed in the light guide system 31 for reflected diffraction light, the light guide system 32 for transmission diffraction light, and the reference light light guide system 33.
Specifically, the first spatial filter 316 is disposed in the light guide system 31 for reflection diffracted light, and the second spatial filter 326 is disposed in the light guide system 32 for transmission diffraction light. Since the light guide system 31 for reflection diffracted light is also used as the reference light light guide system 33, eventually all of the light for transmission diffraction light, the light for reflection diffraction light, and the reference light pass through the spatial filter. become. That is, all the light incident on the imaging element 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 disposed as close as possible to the object S or the imaging device 2. Specifically, in the light guide system 31 for reflection diffracted light, the first spatial filter 316 is disposed on the image side from the branch point of the branched light path Ps in the main light path, and the first spatial filter Only one second mirror 312 is disposed between 316 and the first beam splitter 41. In the light guide system 32 for transmission diffraction light, the second spatial filter 326 is disposed on the branched optical path Ps, and only one third spatial filter 326 from the second spatial filter 326 to the object S is disposed. Mirror 322 is placed.

As described above, by minimizing the number of mirrors disposed between the first spatial filter 316 and the second spatial filter 326 to the object S or the imaging device 2, it is possible to reduce the number of scratches and mirrors of the mirror. It is possible to suppress the decrease in the accuracy of the hologram data due to the influence of attached dust.
In the light guide system 31 for reflected diffraction light, a spatial filter can be disposed between the second mirror 312 and the first beam splitter 41. This can further improve the accuracy of the hologram data. In the light guide system 32 for transmission diffraction light, a spatial filter can be disposed between the third mirror 322 and the object S, and in the same manner, it is possible to further improve the accuracy of the hologram data.

Further, in the present embodiment, in order to simplify the configuration of the optical system, the beam expander and the spatial filter share a part of the optical element. That is, the first spatial filter 316 is realized in the first beam expander 311, and the second spatial filter 326 is realized in the second beam expander 321. A specific structure will be described using 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 is configured of a condensing lens 323 and a collimator lens 324. By setting the focal point f2 on the object side of the collimator lens 324 to the position of the focal point f1 on the image side of the condenser lens 323 and using a large aperture as the collimator lens 324, as shown in FIG. The enlarged parallel light is emitted.

Then, in the present embodiment, the pinhole plate 325 is disposed at a condensing position by the condensing lens 323. The pinholes of the pinhole plate 325 coincide with the light collecting position. As can be understood from FIG. 4, the second spatial filter 326 is configured by the condenser lens 323 and the pinhole plate 325. That is, the condenser lens 323 is shared by the second beam expander 321 and the second spatial filter 326. Such a structure simplifies the configuration of the optical system and reduces the cost by reducing the number of parts. The same is true for the first spatial filter 316 implemented in the first beam expander 311.

Next, the imaging optical system 5 will be described.
Also in the present embodiment, the light guide system 31 for reflection diffracted light irradiates light from the side opposite to the side where the light guide system 32 for transmission diffraction light irradiates light to the object S, and the imaging optical system 5 Is provided on an imaging light path Pi that extends on the side where the light guide system 31 for reflected diffraction light emits light. That is, the reflected diffraction light and the transmission diffraction light are configured to reach the imaging surface of the imaging device 2 through the common imaging light path Pi, and the imaging optical system 5 is disposed on the common optical path.
The imaging optical system 5 includes an objective lens 51 disposed on the side closer to the object S, and an imaging lens 52 disposed on the side closer to the imaging device 2. Another major feature of the apparatus of the present 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 view 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 a chief ray is considered to be parallel to the principal axis. FIG. 5 (1) shows a telecentric optical system on the image side. In particular, an optical system in which the chief ray is considered to be parallel to the optical axis on both the object side and the image side is called two-side telecentric.

The telecentricity of the imaging optical system 5 in the present embodiment is also as shown in FIG. 5 (2), the chief ray is the optical axis both on the front side (object S side) and the rear side (image element 2 side) of the optical system It can be considered parallel to In the present embodiment, the light source 1 is a laser and it is premised that a plane wave (parallel light) is incident. For this reason, combining optics that are both-side telecentric can be achieved by matching the position of the back focal point of the objective lens 51 with the position of the front focal point of the imaging lens 52 (confocal).
The telecentricity of the imaging optical system 5 in the present embodiment has another meaning. As shown in FIG. 5 (3), the objective lens 51 and the imaging lens 52 form an infinity correction optical system, and diffracted light (object light) emitted from one point of the object S is an objective lens 51. At this point, it becomes a parallel light and is incident on the imaging lens 52.
The telecentric infinity correction system has a great merit that the size of the image does not change even if the position of the object S is changed to adjust the focus. This is advantageous when it is desired to obtain hologram data by reflection diffraction light or transmission diffraction light from a position slightly deep from 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 transparent biological sample to a certain extent, there are great merits.

As such an imaging optical system 5, an object-side telecentric lens is adopted as the objective lens 51, and an image-side telecentric lens is adopted as the imaging lens 52, and the focal position of the objective lens 51 on the image side and the imaging lens 52. This can be achieved by arranging the object-side focal position of the object in a state of being in agreement (confocal state). As for the object side telecentric lens and the image side telecentric lens, commercially available ones can be used, so detailed description will be omitted. Since the imaging lens 52, which is an image-side telecentric lens, constitutes an infinity correction system, it is preferable to use a lens with a large effective aperture in order to reduce light loss as much as possible.

The imaging device 2 is, for example, a CCD camera. The CCD camera has an imaging surface of 1024 × 1024 pixels, for example. The imaging element 2 is disposed 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 polarization filter 11 and a 1⁄4 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 1⁄4 wavelength plate 12 prevent return light from entering the light source 1.
The polarization filter 11 transmits only linearly polarized light in a specific direction. The 1⁄4 wavelength plate 12 is disposed with the crystal axis shifted by 45 ° from the transmission axis (direction of linear polarization) of the polarizing filter 11, and has a function of converting linear polarization into circular polarization. The light that has become circularly polarized light is irradiated to the object S or enters the imaging element 2 as a reference light, but this light is used because the first beam splitter 41 and the second beam splitter 45 are used. May come back. The returned circularly polarized light is converted again into linearly polarized light by transmitting through the 1⁄4 λ wavelength plate 12 again. This linearly polarized light further has a phase difference of 1⁄4 wavelength, so that the polarization direction deviates by 90 ° from the light of the first linearly polarized light. Therefore, this light can not 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 or the like of the light source 1 due to the return light is prevented.

Further, to describe holding of the object S, the object S is held by an appropriate member in accordance with the property, size, and the like. For example, as described above, it is placed on a transparent container such as a petri dish or a transparent plate-like member to hold the object S, and in the case of a large object S, a clamp-like member used to hold it is used It is also possible. If the object S is a plate-like one like a substrate, it may be held by a frame-like 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, a control system of the apparatus will be described using FIG. FIG. 6 is a schematic view showing a control system of the digital holography device of the second embodiment.
The control system 6 for controlling the optical element for selection and the like comprises a control board 61 and a computer 63 etc. in which a switching program 62 for sending a signal to the control board 61 to switch between the reflection mode and the transmission mode is installed. .
In this embodiment, a general computer operating on a general-purpose OS such as a desktop personal computer is used as the computer 63 in order to provide the computer 63 also with the function of calculating the reproduction image. And in order to enable control of each part, a control board 61 is attached as its 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 control signal sent out. Each operation signal of is transmitted. The control board 61 has a storage unit such as a RAM, and a sequence control program for outputting each operation signal according to the control signal is written in the storage unit.
When the reflection mode is selected in the switching program 62 and a control signal indicating that the reflection mode is to be set is transmitted, the sequence control program is executed by the switching unit 411 of the first beam splitter 41 and the driving unit 451 of the second beam splitter 45. And the stopper drive 344 of the beam stopper 343 is programmed to send an operation signal for the reflection mode. Further, when the transmission mode is selected in the switching program 62 and a control signal indicating that the transmission mode is to be set is transmitted, the sequence control program transmits the operation signal for the transmission mode to the switching unit 411 of the first beam splitter 41, It is programmed to be delivered to the drive 451 of the second beam splitter 45 and to the stopper drive 344 of the beam stopper 343.

When sensors for detecting the position and posture of the first beam splitter 41, the second beam splitter 45, and the beam stopper 343 are provided, and signals from the respective sensors are input to the control board 61 and used for control. It is suitable. The signal from each sensor is used to monitor whether each part is driven normally or to not send an operation signal but only check the position and attitude when performing the same mode as the previous operation. It can be used.
The light source 1 is turned on and off by a switch provided to a power supply (not shown). However, the light source 1 can be turned on and off by sending a signal from the computer 63 via the control board 61 as a matter of course.

In the computer 63, a program (hereinafter referred to as a reproduction program) 64 for executing a predetermined calculation process for obtaining a reproduced image based on the hologram data obtained on the imaging surface of the imaging device 2 is also installed.
With regard to calculation processing for obtaining a reproduced image from hologram data, various calculation formulas and techniques are well known, and arbitrary ones can be selected and applied. As an example, one using Fourier transform is shown below.

The reproduction plane (the plane on which the reproduced image can be formed) is parallel to the hologram plane (here, the imaging plane of the imaging device 2) and the distance is R. r is from one point on the hologram plane to one 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 equation of diffraction integral. g (x, y) is hologram data, and G (X, Y) is a complex amplitude distribution of a generated image.

In Equation 1, λ is the wavelength and k is the wave number. Equation 3 is obtained by substituting the Fresnel approximation shown in equation 2 for equation 1 and substituting it.

In Equation 3, if the integral is considered to be a Fourier transform and is transformed, Equation 4 is obtained.

The parenthesis of F in Equation 4 indicates that it is a Fourier transform. x and y are outputs from each pixel of the imaging plane, and a discrete Fourier transform is performed to obtain a reproduced image G (X, Y).

In addition, a main program (not shown) for controlling the entire operation is installed in the computer 63. The main program is started automatically when the device is turned on. The main program displays a screen for selecting one of the reflection mode and the transmission mode on the display, and displays a button 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 of the second embodiment will be described below based on FIGS. 3 to 9. 7 to 9 are schematic diagrams showing the operation of the digital holography device of the second embodiment. Among them, FIG. 7 is a diagram showing the progress of each light in the reflection mode and the transmission mode, FIG. 8 is a diagram schematically showing an 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, an object S for which hologram data is to be acquired is disposed and held at a predetermined position by the holding member. In this state, the power of the device is turned on to start the main program. A screen for selecting either the reflection mode or the transmission mode is displayed on the display of the computer 63, so 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. The control board 61 having received this control signal controls 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, and the stopper drive unit of the beam stopper 343. Send to 344.
Specifically, as shown in S1 of FIG. 8, the control board 61 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, the light incident on the first beam splitter 41 via the light guide system 31 for reflected diffraction light is reflected by the reflection surface thereof to form the object S. It is in the state of taking a posture to advance.

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 transmission diffraction 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 drive unit 344 to retract the beam stopper 343 from the light path.
The operation of the sequence control program on the control board 61 is now complete.

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 is incident on the first beam splitter 41 via the light guide system 31 for reflection diffraction light. The light L1 is split into one light L2 that is reflected toward the object S by the reflection 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 guiding system 34. Be done.
One light L2 is irradiated to the object S through the imaging optical system 5, and the reflected diffracted light L4 is emitted from the object S. The reflected diffracted light L 4 passes through the imaging optical system 5 again and enters the first beam splitter 41, passes through the first beam splitter 41, and enters the imaging element 2.
The other light L 3 is reflected back to the folding mirror 342 of the additional light guiding system 34, and reenters the first beam splitter 41. Then, the light L3 is reflected by the reflection surface of the first beam splitter 41, and is incident on the imaging surface of the imaging element 2 as reference light.
Then, as shown by S5 and S6 in FIG. 8, the reflected diffracted light L4 and the reference light L3 interfere with each other on the imaging surface of the imaging device 2, and the interference fringes are imaged on the imaging surface and the hologram data is output to the computer 63. Be done. When the hologram data is output, the reproduction program 64 is executed on the computer 63, and the reproduction image of the object S is formed by performing the calculation processing 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. The control board 61 that has received this control signal executes a sequence control program, and switches each operation signal for the reflection mode to the switching unit 411 of the first beam splitter 41, and the driving unit 451 of the second beam splitter 45, The beam is sent to the stopper drive unit 344 of the beam stopper 343.
Specifically, as shown in S1 of FIG. 9, the control board 61 causes the switching unit 411 to drive the first beam splitter 41 to bring the first beam splitter 41 into the second state. In the second state, as shown in FIG. 7B, the light incident on the first beam splitter 41 through the light guide system 31 for reflected diffraction light is reflected by the reflection surface and directed to the imaging device 2 It is in a state of taking a forward posture. In the second state, the orientation of the reflective surface of the first beam splitter 41 differs by 90 ° from 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 transmission diffraction light and the light guide system 31 for reflection diffraction 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 drive unit 344 and arranges the beam stopper 343 on the optical path of the additional light guiding system 34. , Block the light path.
At this point, the operation of the sequence control program on the control board 61 is completed.

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 split into one light L5 passing through the second beam splitter 45 and the other light L6 reflected by the reflection surface of the second beam splitter 45 and directed to the object S. One light L <b> 5 is guided by the light guide system 31 for reflected diffraction light which is also used as the reference light light guiding system 33 and is incident on 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 imaging device 2, and is incident on the imaging surface of the imaging device 2 as reference light. The light transmitted through the first beam splitter 41 is blocked by the beam stopper 343 and does not return to the first beam splitter 41.
The other light L6 split by the second beam splitter 45 is irradiated to the object S through the light guide system 32 for transmission diffraction light. The light passes through the object S and is emitted from the object S as transmission diffracted light L7. The transmission diffracted light L 7 enters the first beam splitter 41 through 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 of FIG. 9, on the imaging surface of the imaging device 2, interference fringes of the reference light L5 and the transmission diffraction light L7 are formed, and the interference fringes are imaged to obtain hologram data. The hologram data is similarly sent to the computer 63, and the reproduction program 64 is executed to form a reproduced image of the object S.

As described above, although the reflection mode and the transmission mode are sequentially performed to reproduce the image, the information on the reproduced 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, sometimes only amplitude information is extracted and a two-dimensional shape or the like is mainly observed, or only phase information is extracted and a 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 from the viewpoint of obtaining high-precision hologram data. Hereinafter, this point will be described with reference to FIG.
FIG. 10 is a schematic view showing the effect of the apparatus of the second embodiment including the telecentric imaging optical system 5. FIG. 10A is shown for comparison, and is a wavefront diagram in the case of using an imaging optical system that is not telecentric. FIG. 10B is a wavefront diagram in the case of using the telecentric imaging optical system 5 according to the present embodiment.

The telecentricity in the apparatus of the present embodiment is achieved by arranging the objective lens 51 and the imaging lens 52 constituting the infinite correction optical system in a confocal manner. As shown in FIG. 10 (A1), when a general finite correction optical system is used, the plane wave Lp can be irradiated to the object S in the transmission mode. However, in the finite correction optical system, when the plane mode Lp is applied to the object S as shown in FIG. 10 (A2) when passing from the transmission mode to the reflection mode, it passes through the imaging optical system 5. The object S is irradiated with the light (spherical wave) Ls collected by the objective lens. In this case, due to distortion of the object light imaged by the imaging device 2, it is not possible to form a reproduced image with high accuracy.

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

Thus, according to the present embodiment, the plane wave Lp is irradiated to the object S regardless of which of the reflection mode and the transmission mode is selected. Therefore, in both the transmission mode and the reflection mode, regions of the same size can be observed, and image reproduction can be performed by the same reproduction calculation means. Furthermore, since the object light is not distorted, correction calculation is not necessary, and image reproduction with variable working distance, which is a fundamental feature of digital holography, can be freely performed. Furthermore, since the optical system is a telecentric optical system, there is also an advantage that the imaging magnification does not change in image reproduction in which the working distance is variable. Note that image reproduction in which the working distance is variable 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 can be performed on the object S at low cost. In addition, since the reflection diffraction light and the transmission diffraction light are temporally separated and enter the imaging device 2, the configuration of the optical system is simplified and only one imaging device 2 is sufficient. For this reason, the cost of one device is also reduced.
In addition, since light for reflected diffraction light is irradiated from the first side of the object S and light for transmission diffraction light is irradiated from the opposite second side, the object light is captured exclusively on the first side. Can. For this reason, it is possible to obtain highly accurate hologram data without forcing the object S to float in the air.
Further, although the imaging optical system 5 causes object light to be incident on the imaging element 2 in both the reflection mode and the transmission mode, the optical system is simplified in this point as it is shared by both modes. Contribute to reducing the cost of the device.

In the present invention, different 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 disposed on the imaging optical path Pi, and in the transmission mode, the imaging optical system for the transmission mode is switched and disposed on the imaging optical path Pi.
Further, even in the case where the imaging optical system is shared in both modes, in addition to the case where all the imaging optical systems are shared, a part may be shared. For example, the imaging lens may be shared, and the objective lens may be prepared for the reflection mode and the transmission mode and switched for use.

Further, as compared with the apparatus of FIG. 15, the apparatus of the present embodiment has a straight imaging light path Pi. That is, object light emitted from the object S travels along a straight optical path and enters the imaging device 2. This point has the following effects.
First, since the optical path is a straight line, adjustment of the optical axis is easy. That is, in order to obtain highly accurate hologram data, the object S, the imaging optical system 5 and the imaging device 2 need to be precisely aligned on the optical axis, but this adjustment is easy because the optical axis is a straight line. .
Further, as shown in FIG. 15, when the optical path from the object S to the imaging device 2 is complicatedly bent, many optical elements such as mirrors are required, and the cost is increased accordingly. According to the present embodiment, there is no such cost increase.
Furthermore, when the optical path is bent in a complicated manner, the disturbance of the wavefront due to an optical element such as a mirror is likely to occur, but such a problem does not occur in this embodiment. This point also makes it possible to obtain hologram data with high accuracy.

Further, the apparatus of this embodiment uses the first spatial filter 316 and the second spatial filter 326, and both the object light and the reference light are light passing through the spatial filter. . For this reason, the wavefront is incident on the imaging element 2 in a state where the noise is removed. This point also greatly contributes to the improvement of the accuracy of the hologram data, and the spatial filter is located on the optical path closer to the object S. For this reason, it is less likely that noise will be introduced into the wavefront due to factors after passing through the spatial filter. This point also greatly contributes to the improvement of the accuracy of the hologram data.

Further, the device of the present embodiment further simplifies the optical system and enhances the coherence by making the reference light guiding system 33 common to the light guiding system for object light, as compared with the first embodiment. It is a more practical device. Hereinafter, this effect will be described.
First, in the reflection mode, the light for reflected diffraction light and the reference light are guided from the light source 1 to the first beam splitter 41 by one and the same light guiding system. Then, the light is split into the first beam splitter 41, and the light for reflected diffraction light reaches the object S, and the reference light reaches the imaging element 2 without passing through the object S by the additional light guiding system.
As described above, in the configuration in which the object light and the reference light are made incident on the imaging element 2 while sharing the light guide system as much as possible, the difference in optical conditions is reduced or the difference in optical path lengths is reduced. It is easy to As a result, the coherency between the reference light and the object light can be enhanced, which helps to obtain more accurate hologram data, and a reduction in the device cost due to the reduction in the number of optical elements used is realized. The additional light guiding system 34 has a similar meaning in that light is returned to the first beam splitter 41 and then incident on the imaging element 2 as reference light.
Further, in the transmission mode, the light guided by the light guide system 31 for reflection diffracted light passes through the first beam splitter 41 and is incident on the image pickup element 2, and almost all the portions for guiding the reference light are reflected. The light guide system 31 for diffracted light is also used. Therefore, the coherency is further enhanced, the configuration of the optical system is further simplified, and the cost reduction due to the reduction in the number of used optical elements is further realized.

Next, a digital holography device of 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 of the third embodiment enables off-axis operation in the apparatus of the second embodiment. In the off-axis type, 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 or the zero-order image (image by the reference light) at the time of image reproduction. Has the advantage of being able to prevent overlapping.
The device shown in FIG. 11 differs from that of the second embodiment in the configuration of the reference light guiding system 33 in order to enable the off-axis system. That is, one of the mirrors constituting the reference light guiding system 33 is arranged in a state where the angle with respect to the optical axis can be changed.
Specifically, the second mirror 312 in the second embodiment is an off-axis mirror in the light guide system 31 for reflected diffraction light that is also used as the reference light light guide system 33 in the transmission mode. First off axis mirror) 317 has been changed. The first off-axis mirror 317 is provided with a first off-axis drive unit 318, and the arrangement angle of the first off-axis mirror 317 with respect to the optical axis can be changed.

Further, the configuration of the additional light guiding system 34 is largely changed regarding the reference light guiding system 33 in the reflection mode. The additional light guiding system 34 in the third embodiment is also for returning the light transmitted through the first beam splitter 41 in the reflection mode back to the first beam splitter 41. In the third embodiment, the additional light guiding system 34 is a loop in order to arrange the off-axis mirror close to the image pickup element 2 and reduce (or eliminate) the difference between the object light and the optical path length. Form an optical path of
Specifically, the additional light guiding system 34 has a polarization beam splitter 345 on the light path extending from the first beam splitter 41. The polarization beam splitter 345 is a beam splitter that transmits only a linear polarization component in a specific polarization direction, and reflects the other component. A quarter-wave 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 to circularly polarized light by the polarization filter 11 and the 1⁄4 wavelength plate 12 immediately after. Therefore, when the light is transmitted through the 1⁄4 wavelength plate 346, the light is further linearly polarized in the direction 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 the linearly polarized light reflected by the polarization beam splitter 345. The light is reflected back to the polarizing beam splitter 345 by being reflected by these mirrors. The second off-axis mirror 349 is provided with a second off-axis drive 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 transmits without being reflected by the polarization beam splitter 345. This light is converted into circularly polarized light again by transmitting through the 1⁄4 wavelength plate 346 again, and reaches the imaging element 2 through the first beam splitter 41.

Also in this embodiment, since the additional light guiding system 34 is not used in the transmission mode, a beam stopper and a stopper driving unit for blocking light are provided. Although illustration of the beam stopper and the stopper driving unit is omitted, for example, the beam stopper can be disposed between the 1⁄4 wavelength plate 346 and the polarization beam splitter 345.
Further, 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, has a pinhole inside as in the case shown in FIG. 4, and forms a spatial filter configuration. Thereby, it is possible to remove the fluctuation of the wavefront derived from the optical components such as the mirror and the wave plate immediately before the spatial filter.

The off-axis mirror will be further described in detail with reference to FIG. FIG. 12 is a view showing a change in the arrangement angle of the off-axis mirror used in the third embodiment, and FIG. 12 (1) is a schematic plan view, and FIG. 12 (2) is a schematic perspective view. is there. FIG. 12 shows, as an example, the second off-axis mirror 349 disposed in the additional light guiding system 34.
As shown in FIG. 9, the second off-axis mirror 349 can be in a posture in which the angle with respect to the optical axis is not 45 ° but slightly inclined. 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) can be given a state given by θ).

In the present embodiment, the posture change of the second off-axis mirror 349 is possible in two directions. That is, as shown in FIG. 12 (2), rotation about the rotation axis A1 along a line formed by the plane formed by the optical axis before refracting and the optical axis after refracting intersects the reflecting surface, and rotation Rotation about a rotation axis A2 in a direction perpendicular to the axis A1 and along the reflecting surface. By enabling such two rotations, it is possible to make the reference light incident with an off-axis angle θ in two orthogonal directions (X and Y directions) with respect to the imaging surface of the imaging device 2. It is up to the operator to decide in which direction the true image is to be separated from the zero-order image or the conjugate image in which direction the off-axis angle θ is to be applied. 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.
A kinematic mirror holder that can be adjusted in two directions can be used as the drive unit for each of these off-axis mirrors, and an actuator can be attached to each adjustment axis to enable control with an external signal. It can be adopted. Each drive unit similarly sends an operation signal from the control board 61 to be controlled.

The first off-axis mirror 317 in the light guide system 31 for reflected diffraction 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 in a posture inclined at a predetermined angle from 45 ° so that the off-axis angle θ can be obtained in the transmission mode. Also, in the reflection mode, an operation signal is sent to return to the normal posture, that is, the posture of 45 ° with respect to the optical axis. The term "ordinary mirror" means a mirror in which no off-axis angle is generated 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, it may be configured to be maintained at 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 also unnecessary, it is preferable to be able to change the angle for adjustment or the like.

As described above, the configuration of the additional light guide system 34 used in the reflection mode is largely changed in the present embodiment. The reason for this is to place the second off-axis mirror 349 as close to the imaging element 2 as possible and to reduce the difference in optical path length 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 obliquely enter the object light. However, as the oblique angle (off-axis angle) increases, the spatial frequency on the imaging surface of the imaging device 2 increases (that is, the interference fringes become smaller), and the image resolution of the imaging device 2 causes a clear image reproduction. Will not be able to Therefore, it is preferable that the off-axis angle θ be as small as, for example, about 2 to 3 degrees.
Because of such an off-axis angle θ, the first off-axis mirror 317 and the second off-axis mirror 349 are inclined not at 45 ° with respect to the optical axis as shown in FIG. However, if it is located on the optical path away from the imaging device 2, the incident position is largely shifted on the imaging surface of the imaging device 2 even if the angle is slightly changed. The reference light needs to cover the entire area of the imaging surface of the imaging device, and if a region where the reference light does not enter is formed due to the deviation of the incident position, imaging of interference fringes can not be performed in that region. Therefore, the first off-axis mirror 317 and the second off-axis mirror 349 function as an imaging element in order to make the reference light incident on the entire imaging surface of the imaging element 2 even at a small angle of about 2 to 3 °. It should be a mirror close to 2.

In the configuration of the second embodiment shown in FIG. 3, the folding mirror 342 of the additional light guiding system 34 may be used as an off-axis mirror, but since the folding mirror 342 is located at a distance from the imaging element 2, imaging of the imaging element 2 is performed. The deviation of the incident position of the reference light with respect to the surface increases. Although it is conceivable to use the fourth mirror 341 on the light path in front of the folding mirror 342 as an off-axis mirror, the fourth mirror 341 reflects twice before reaching the folding mirror 342 and after reaching it. Therefore, the deviation of the reference light is doubled.
Furthermore, it is conceivable to provide a folding mirror 342 at the position of the fourth mirror 341 and use it as an off-axis mirror, but this shortens the optical path length and causes reference light and object light (in this case, reflection) The difference in optical path length becomes large with diffracted light. This can cause problems in terms of coherency. That is, when the difference in optical path length becomes large, it becomes difficult for the reference light and the object light to interfere due to the problem of temporal stability of the output of the light source 1.

Taking these points into consideration, a looped optical path is formed by the polarizing beam splitter 345 from the viewpoint of arranging the mirror that reflects only once at a position close to the imaging element 2 and securing the optical path length. It is preferable to arrange a mirror for this purpose. The additional light guiding system 34 of the third embodiment is based on such an idea.
In addition, to supplementarily explain “close” at the arrangement position of the first off-axis mirror 317 and the second off-axis mirror 349, in the configuration of this embodiment, the object light and the reference light are the first. The beam splitter 41 integrates. Therefore, it is "close" that the first mirror is an off-axis mirror as viewed from the first beam splitter 41 when it travels in the direction opposite to the traveling direction of light.

The operation of the third digital holography device shown in FIG. 11 will be described with reference to FIG. FIG. 13 is a schematic view showing the operation of the third embodiment, and a view 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 part to be 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 brought into the first state. Further, the beam stopper (not shown) in the additional light guiding system 34 retracts from the light path, and the additional light guiding system 34 is opened. Since the first off-axis mirror 317 is used as a normal mirror, the attitude of 45 ° with respect to the optical axis is maintained.

The light L 1 emitted from the light source 1 is converted to circularly polarized light by passing through the polarizing filter 11 and the 1⁄4 wavelength plate 12, and is incident on the first beam splitter 41 through the light guide system 31 for reflection diffraction light. Do. This light L1 is split into the light L2 reflected by the first beam splitter 41 and the light L3 transmitted as shown in FIG. 13 (A). The light L 2 reflected by the first beam splitter 41 is irradiated to the object S via the imaging optical system 5. The irradiated light L2 is reflected by the object S and becomes object light (reflected diffracted light) L4. The object light (reflected diffracted light) L4 is incident on the first beam splitter 41 through the imaging optical system 5, transmitted through the first beam splitter 41, and incident on the imaging surface of the imaging device 2.
On the other hand, the light L 3 transmitted through the first beam splitter 41 is incident on the additional light guiding system 34. Since this light L 3 is circularly polarized light, it is converted into linearly polarized light having a specific polarization component by the 1⁄4 wavelength plate 346, and the linearly polarized light L 3 enters the polarization beam splitter 345.

The polarization beam splitter 345 reflects only the light of the polarization of the specific component converted by the quarter-wave plate 346. Therefore, as shown in FIG. 13A, the light beam L3 is reflected by the polarization beam splitter 345 and is incident on the half-wave plate 351, and the linearly polarized light is 90 ° different in polarization direction from the linearly polarized light. It is converted to light. The light L3 which is linearly polarized light which is 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 to return to the polarizing beam splitter 345. At this time, since the second off-axis mirror 349 is slightly inclined not at 45 ° with respect to the optical axis, the light L3 reflected by the off-axis mirror is not parallel to the optical axis but at a slight angle. Proceed with holding

The light L 3 reaching the polarization beam splitter 345 in such an angle state is transmitted through the polarization beam splitter 345 because the direction of the linear polarization is converted by 90 ° by the half-wave plate 351. Then, the light L 3 is converted into circularly polarized light by the 1⁄4 wavelength plate 346, is reflected by the first beam splitter 41, and then enters the imaging surface of the imaging device 2 as reference light. At this time, since the light beam passes through the second off-axis mirror 349, as shown in FIG. 12, the reference light L3 is incident on the object light (reflected diffracted light) L4 with the off-axis angle θ. On the imaging surface of the imaging element 2, the object light (reflected diffracted light) L4 and the reference light L3 interfere with each other to form interference fringes, and the interference fringes are imaged on the imaging surface. Thereby, hologram data in the reflection mode can be obtained.
The light reflected by the second off-axis mirror 349 travels in a state of being at an angle to the optical axis as described above, and passes through the polarization beam splitter 345 and the quarter wavelength plate 346. However, since the angle with respect to the optical axis is very small, there is no problem in light control in the polarization beam splitter 345 or the quarter-wave plate 346.

When the transmission mode is selected, an operation signal for the reflection mode is sent from the control board 61 to each part to be controlled. That is, as shown in FIG. 13B, the first beam splitter 41 is rotated by 90 ° to be in the second state. In addition, the second beam splitter 45 moves on the main optical path, and a beam stopper (not shown) in the additional light guiding system 34 is disposed on the optical path. In addition, 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 at a predetermined angle from the attitude of 45 ° with respect to the optical axis.
The light emitted from the light source 1 is similarly converted to circularly polarized light and then enters the second beam splitter 45. As shown in FIG. 13B, a part of the light beam is reflected by the second beam splitter 45, and the light L5 for transmission diffraction light travels to the branched light path Ps, and the light transmission system 32 for transmission diffraction light makes the object S It is irradiated. This light L5 passes through the object S to become object light (transmission diffracted light) L6, passes through the imaging optical system 5, enters the first beam splitter 41, passes through the first beam splitter 41, and passes through the imaging element 2 To the imaging surface of the

On the other hand, the light L7 transmitted through the second beam splitter 45 without being reflected by the second beam splitter 45 is guided by the light guiding system 31 for reflected and diffracted light, which is also used as the reference light guiding system 33, The light reaches the beam splitter 41, is reflected by the first beam splitter 41, and is incident on the imaging surface of the imaging device 2 as reference light. At this time, since the first off-axis mirror 317 is tilted at a predetermined angle, the reference light L7 is incident on the object light L6 with the off-axis angle θ.
In the imaging surface of the imaging element 2, the reference light L7 and the object light L6 interfere with each other to form interference fringes, and the interference fringes are imaged on the imaging surface to obtain hologram data. Then, the 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, so that the clearer true image is obtained. You can get Therefore, it is more preferable to calculate the distance between a certain point on the object S and a certain point or to observe 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 imaging device 2, the incident position of the reference light with respect to the imaging surface of the imaging device 2 is largely shifted. Absent. On the other hand, since the optical path length of the reference light and the optical path length of the object light are sufficiently matched, highly accurate hologram data can be obtained regardless of the temporal fluctuation of the output of the light source 1. "Sufficiently matched" means that even if there is a difference in optical path length, there is no problem in terms of coherence.
The use of an off-axis mirror as an off-axis device is also possible in the device of the first embodiment. 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, it is sufficient if there is one off-axis mirror on the optical path of the reference light reaching the imaging device 2.
Also, it is possible in principle to use an optical element other than a 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 to achieve off-axis.

Further, as a configuration other than off-axis, in the device of the first embodiment or the device of the second embodiment, it is also possible to separate the true image from the zero-order image and the conjugate image by the phase shift method. . In this case, a phase shift element is provided in the reference light guide system 33. The phase shift element is an element capable of changing the optical path length of a piezoelectric element such as a piezoelectric element or an SLM as described above. In the second embodiment, for example, the phase shift element for reflection mode is disposed in the additional light guiding system 34, and the phase shift element for transmission mode is guided to the reflection diffracted light in the second embodiment. It is arranged in the optical system 31 (however, except for 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 diffraction light is retracted from the light path in the reflection mode.
When the phase shift method is adopted, as described above, when the object S moves, hologram data can not be substantially obtained. 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, the reproduced image can be obtained as a moving image. This point is also a merit of the device 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 front schematic view of the digital holography device of the fourth embodiment of the present invention.
As shown in FIG. 14, also in the digital holography device of the fourth embodiment, a light guide system 31 for reflected diffracted light and a light guide system 32 for transmitted diffracted light are provided. These

light guide systems

31 and 32 are substantially the same as the second embodiment shown in FIG. The fourth embodiment is largely different from the second embodiment in that the reference light guiding system 33 extracts the reference light from the object light and guides the reference light to the imaging device 2.

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

As a method of extracting the reference light from the object light, a spatial frequency filtering method is adopted. In the object light, a portion where the wave front (amplitude or phase) changes according to the shape, surface condition, etc. of the object is a portion where the spatial frequency is high. The part where the wave front is changing according to the shape, surface condition, etc. of the object is a part that can represent the shape, surface condition of the object by reproducing the image as described above. It can be said that it is a part that contains On the other hand, in the object light, diffracted light emitted from a region where the refractive index is sufficiently uniform can be treated as similar to light not passing through the object because the spatial frequency is low. That is, among object light, light that can express object information is light having a high spatial frequency, and if it is removed from the object light, light (that is, reference light) that does not include object information can be extracted. This is the same principle as the spatial filter. The reference light extraction unit 9 shown in FIG. 14 is a unit that performs such extraction.

Several different optical systems are conceivable for such a reference light extraction unit 9. Among these, two different examples are shown in FIG. 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. 15 (1) comprises a separation element 91 for separating object light to advance along two different optical axes, and an extraction lens for collecting light for extraction of reference light. A spatial frequency filter 93 disposed at a condensing position by the extraction lens 92, and a collimator lens 94 for converting each light into parallel light and integrating them are provided.
As the separating element 91, for example, a diffraction grating can be used as disclosed in JP-A-10-141912, or a polarization beam splitter can be used as disclosed in JP-A-2006-292939. .

In the case where a diffraction grating is used as the separation element 91, for 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 zeroth-order diffracted light and the first-order diffracted light, but the spatial frequency filter 93 includes an aperture 931 provided at a position on the optical axis where the zero-order diffracted light is condensed; And a pinhole 932 provided at a position on the optical axis where the next diffracted light is collected. The aperture 931 allows the object light (0th-order diffracted light) to pass therethrough without selecting the spatial frequency because it is sufficiently large. On the other hand, since the pinhole 932 is sufficiently small, only low frequencies are allowed to pass. Therefore, the first-order diffracted light does not include object information. These lights are integrated while being converted back to parallel light by the collimator lens 94 as shown in FIG. 15 (1), and are superimposed on the imaging surface of the imaging device 2.

When a polarization beam splitter is used as the separation element 91, the object light is split into two polarized lights whose polarization directions differ by 90 °. For convenience, when the two polarized lights are referred to as a first polarized light and a second polarized light, the first and second two polarized lights are similarly collected by the extraction lens 92 and reach the spatial frequency filter 93. The structure of the spatial frequency filter 93 is the same as the above, and a sufficiently large aperture 931 is formed on the optical axis of the first polarized light, and a sufficiently small pinhole 932 is formed on the optical axis of the second polarized light. Be done. The first polarized light passes through the aperture 931 as it is without filtering by spatial frequency, and enters the imaging element 2 as object light. On the other hand, the second polarized light passes through the pinhole 932 in a state where the high spatial frequency component 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. When a polarization beam splitter is used as the separation element 91 as indicated by a dotted line in FIG. 15A, a half wave plate 95 is provided on the emission side of the pinhole 932 of the spatial frequency filter 93. This is to match the polarization state of the reference light to the object light and to improve the coherence.

As the dispersive element 91, as long as it can separate object light along two optical axes, it may be other than the two examples described above. The example shown in FIG. 15 (2) is one of these, and is an example using a normal beam splitter. The object light is split 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 largely deviated from the other optical axis, an opening for object light is not necessary, and one light separated by the separation element 91 having only the pinhole 932 is When passing through the spatial frequency filter 93, high spatial frequency components are removed to become reference light, and collimated light is returned to parallel light by the collimator lens 94. Then, the beam is integrated with the other light (object light) by the integration beam splitter 96 and is incident on the imaging device 2.

In the fourth embodiment, unlike the second embodiment shown in FIG. 3, since the light guide system 31 for reflected diffraction light is not used also as the reference light guide system, if the second beam splitter 45 is driven, Instead, the transmission mode and the reflection mode are switched by switching the two shutters. That is, as shown in FIG. 14, the first shutter 319 is provided on the main optical path P, and the second shutter 327 is provided on the branched optical path Ps. In the transmissive mode, the first shutter 319 is closed and the second shutter 327 is opened. In the reflective 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 imaging device 2 in the off-axis state with respect to the object light, but in the example shown in FIG. 15 (2), it is incident in the in-line state. In the example shown in FIG. 15 (2), when it is desired to set the off-axis state, a driving mechanism is attached to the mirror 97 disposed between the collie meter lens 94 and the integration beam splitter 96 to make an off-axis mirror. good.
The fourth embodiment is the same as the above-described embodiment except for the structure for obtaining the reference light. The reflection mode and the transmission mode can be performed separately, which is suitable for examining the state, shape, etc. of an object in detail, and the configuration of the optical system is simplified.
In the optical system shown in FIG. 15 (2), when it is a problem in terms of coherence, etc. that the optical path lengths of the object light and the reference light are different, a mirror is disposed instead of the integration beam splitter 96. The object light may be folded downward, the integration beam splitter may be disposed instead of the mirror 97, and the imaging element 2 may be disposed at a position where the optical axis is linearly extended from the spatial frequency filter 93.

In each of the embodiments described above, 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 utilizing Fresnel diffraction or in the case of 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 guiding system 33 includes a lens that makes the reference light a spherical wave and causes the light to be incident on 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, but this is not essential, so one lens may not be called the imaging lens 52. , And may be called like a first objective lens and a second objective lens.

In the apparatus of each of the above embodiments, the direction in which the light for reflected diffracted light enters the object S and the direction in which the light for transmitted diffracted light enters the object S differ by 180 °. However, this is not an essential requirement in the present invention. When considered on the basis of the optical axis of the linear imaging light path Pi from the object S to the imaging element 2, light for reflected diffraction light may be obliquely incident on the optical axis, or for transmission diffraction light Light may be incident obliquely to the optical axis. Therefore, if the first side is considered as the first quadrant and the second quadrant in consideration of orthogonal coordinates with the position of the object S as the origin, the "second side" means the third quadrant and the fourth quadrant. It turns out that.

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

Although related to the above points, in the second embodiment and the third embodiment, the “first state” and the “second state” of the first beam splitter 41 need to be understood in a broad sense. is there. For example, a configuration may be considered in which two beam splitters functioning as the first beam splitter are prepared, and are selectively used for the reflection mode and the transmission mode. As shown in FIG. 7A, a beam splitter 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 from the lower left to the upper right as shown in FIG. 7B. It is possible to consider a configuration in which switching is performed on the optical path by an appropriate switching mechanism. Such a configuration is also within the concept of "first state" and "second state".

DESCRIPTION OF SYMBOLS 1 light source 2 imaging element 31 light guiding system 32 for reflected diffraction light light guiding system 33 for transmission diffraction light reference light guiding system 34 additional light guiding 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 to 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 imaging device Digital holography method for acquiring hologram data by
When the light from the light source is irradiated to the object from the first side, the refracted diffracted light reflected from the object and emitted from the object to the first side interferes with the reference light at the imaging surface of the imaging element to acquire hologram data Performing a reflection mode to
When the object is irradiated with light from the light source from the second side opposite to the first side, the transmission diffracted light transmitted and emitted to the first side and the reference light are taken on the imaging surface of the imaging device Performing a transmission mode of causing interference to acquire hologram data;
A digital holography method characterized in that 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 of the diffracted light from the object obtained by irradiating the object with the light emitted from the light source and the reference light extracted without the object information from the diffracted light from the object on the imaging surface of the imaging device A digital holography method for acquiring hologram data, comprising:
When the light from the light source is irradiated to the object from the first side, the refracted diffracted light reflected from the object and emitted from the object to the first side interferes with the reference light at the imaging surface of the imaging element to acquire hologram data Performing a reflection mode to
When the object is irradiated with light from the light source from the second side opposite to the first side, the transmission diffracted light transmitted and emitted to the first side and the reference light are taken on the imaging surface of the imaging device Performing a transmission mode of causing interference to acquire hologram data;
A digital holography method characterized in that 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 to 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 imaging device A digital holography device for acquiring hologram data by
A light guide system for reflected diffracted light, which guides light from a light source to an object to obtain reflected diffracted light which is diffracted light emitted by reflecting light to the object;
A light guiding system for transmitting diffracted light that guides light from a light source to the object to obtain transmitted diffracted light that is diffracted light that is emitted by transmitting light through the object;
An image pickup element whose position where the reflected diffracted light can be incident and whose imaging surface is located at the position where the transmitted diffracted light can be incident;
And a reference light guide system for guiding the light from the light source to the imaging surface of the imaging device without passing through the object,
A selection optical element is provided to select alternatively whether the reflection diffracted light is made incident on the imaging surface of the imaging device to make the reflection mode or the transmission diffraction light made to make the transmission mode,
The light guide system for reflected diffraction light irradiates light from the light source to the object from a first side,
The light guide system for transmission diffraction light irradiates the light from the light source to the object from the second side opposite to the first side,
A digital holography device characterized in that an imaging optical path which is an optical path from the object to an imaging surface of the imaging element is set on a first side of the object.
Interference of the diffracted light from the object obtained by irradiating the object with the light emitted from the light source and the reference light extracted without the object information from the diffracted light from the object on the imaging surface of the imaging device A digital holography apparatus for acquiring hologram data, comprising:
A light guide system for reflected diffracted light, which guides light from a light source to an object to obtain reflected diffracted light which is diffracted light emitted by reflecting light to the object;
A light guiding system for transmitting diffracted light that guides light from a light source to the object to obtain transmitted diffracted light that is diffracted light that is emitted by transmitting light through the object;
An image pickup element whose position where the reflected diffracted light can be incident and whose imaging surface is located at the position where the transmitted diffracted light can be incident;
And a reference light guiding system for extracting the reference light from the reflection diffraction light or the transmission diffraction light without including the object information and guiding the reference light to the imaging surface of the imaging device,
A selection optical element is provided to select alternatively whether the reflection diffracted light is made incident on the imaging surface of the imaging device to make the reflection mode or the transmission diffraction light made to make the transmission mode,
The light guide system for reflected diffraction light irradiates light from the light source to the object from a first side,
The light guide system for transmission diffraction light irradiates the light from the light source to the object from the second side opposite to the first side,
A digital holography device characterized in that an imaging optical path which is an optical path from the object to an imaging surface of the imaging element is set on a first side of the object.
5. The digital holography device according to claim 3, wherein an imaging optical system including a lens is provided on the imaging light 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.
7. The digital holography device according to claim 3, 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 light path extends from the object to the imaging surface in a straight line.
The light guide system for reflected diffraction light is for guiding light to the object through the imaging light path, and is provided with a first spatial filter on the light path until reaching the imaging light path. And 0 or only one mirror on the optical path from the spatial filter to the imaging optical path,
The light guide system for transmission diffracted light comprises a second spatial filter and has zero or only one mirror on a light path from the second spatial filter to the object. The digital holography device according to any one of claims 3 to 8, wherein
As the selection optical element, a first selection optical element disposed on a main optical path extending from the light source is provided, and the main optical path is an optical path of the light guide system for reflected diffraction light and the transmission diffraction light The first selection optical element advances light along the light path of the light guide system for reflected diffraction light or the light guide for transmission diffraction light. 10. The digital holography device according to any one of claims 3 to 9, wherein selection is made as to whether to proceed along the optical path of the system.
A first beam splitter is provided on the imaging optical path, the light guide system for reflected diffraction light is for guiding light from a light source to the first beam splitter, and the first beam splitter is The light guide system according to any one of claims 3 to 10, wherein in the reflection mode, the light guided by the light guide system for reflected diffraction light is divided and one of the lights is directed to the object. Digital holography device described in.
As the selection optical element, a first selection optical element disposed on a main optical path extending from the light source is provided, and the main optical path is an optical path of the light guide system for reflected diffraction light and the transmission diffraction light The first selection optical element advances light along the light path of the light guide system for reflected diffraction light or the light guide for transmission diffraction light. It chooses 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 diffraction light is for guiding light from a light source to the first beam splitter, and the first beam splitter is It takes a first state in which light guided by the light guide system for reflected diffraction light is divided in the reflection mode and one of the lights is directed to the object,
The reference light guiding system is for guiding the other light split by the first beam splitter to the imaging surface of the imaging device without passing through the object in the reflection mode.
The first selection optical element is a second beam splitter, and a drive unit for changing the arrangement position of the second beam splitter is provided, and the drive unit performs the second operation in the reflection mode. The second beam splitter is disposed on the main optical path in the transmission mode while the light is prevented from advancing to the optical path of the light guiding system for transmission diffraction light by setting the beam splitter at a position deviated from the main optical path. A part of the light is made to travel along the light path of the light guide system for transmission diffraction light,
The first beam splitter is disposed as a second selection optical element, and the first beam splitter is provided with a switching unit that changes 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. And the second state is guided by the light guiding system for reflected light and reaches the first beam splitter so that the light guiding system for reflected light is also used as the light guiding system for reference light. 10. The digital holography device according to claim 3, wherein the incident light enters the imaging surface of the imaging device without passing through the object.
The reference light guiding system is configured such that, in the reflection mode, the other light transmitted through the first beam splitter passes through the first beam splitter and is incident on an imaging surface of the imaging device. Returning to the first beam splitter,
A beam stopper capable of being disposed on the optical path for returning the other light to the first beam splitter, and a stopper driving unit for driving the beam stopper are provided, and the stopper driving unit is in the reflection mode. 13. The digital holography apparatus according to claim 12, wherein the beam stopper is not disposed on the optical path in the case of the light source, and the beam stopper is disposed on the optical path in the transmission mode.
The reference light guiding system is an imaging surface of the imaging device with reference light in a state where a predetermined angle is given to the direction of the reflected diffraction light or the transmission diffraction light when entering the imaging surface of the imaging device. The digital holography device according to any one of claims 3 to 12, further comprising an off-axis optical element to be incident on the light source.
Off-axis optical system for causing reference light to be incident on the imaging surface of the imaging device in a state where a predetermined angle is given to the direction of the reflected diffraction light or transmission diffraction light when entering the imaging surface of the imaging device An element is provided,
The off-axis optical element includes a first off-axis mirror provided with the light guide system for reflected diffraction light on the light path in front of the first beam splitter, and the reference light guide system uses the other light as the first light A second off-axis mirror provided on the light path when returning to the 1 beam splitter,
The first off-axis mirror is provided with a drive unit, and in the reflection mode, the drive unit sets the first off-axis mirror in the first posture, and in the transmission mode, the first off-axis mirror. 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 The digital holography device according to claim 13, characterized in that
The first off-axis mirror is the first mirror when the light path is traced from the first beam splitter toward the light source in the direction opposite to the light traveling direction,
When the reference light guiding system traces the other light back to the first beam splitter from the first beam splitter in the direction opposite to the light traveling direction, the second off-axis mirror 16. A digital holography device according to claim 15, characterized in that it is the first mirror.