Patent Description:
Conventionally, a phase contrast microscope capable of observing a biological cell without dyeing has been used to observe the biological cell while culturing the cell. The biological cell as an observation target is cultured in an incubator capable of keeping the temperature constant. In order to observe the biological cell, the phase contrast microscope needs to be arranged in the incubator. Patent Literature <NUM> describes an example of a phase contrast microscope configured to be incorporable in the incubator. The phase contrast microscope is an epi-illumination phase contrast microscope, in which both an illumination optical system and an observation optical system are arranged on the same side with respect to the observation target.

Illumination light beams emitted from the illumination optical system are reflected on a reflection surface to be reflected light beams. The reflected light beams include a directly reflected light beam which is reflected on the surface of the reflection surface without being diffracted inside the observation target when passing through the observation target and a diffracted and reflected light beam which is diffracted inside the observation target when passing through the observation target to be delayed in phase by <NUM>/<NUM> wavelength and reflected on the surface of the reflection surface. In the observation by the phase contrast microscope, the phase of the directly reflected light beam reflected on the surface of the reflection surface is advanced or delayed by <NUM>/<NUM> wavelength. By an operation the phase of the directly reflected light beam, a phase contrast between the directly reflected light beam and the diffracted and reflected light beam is <NUM> or <NUM>/<NUM> wavelength and the directly reflected light beam and the diffracted and reflected light beam are intensified or weakened with each other. Since the phase contrast between the directly reflected light beam and the diffracted and reflected light beam is converted into the contrast between brightness and darkness, an optical image perceptible to human eyes is obtained.

<CIT> discloses an epi-illumination phase contrast microscope.

It is not realistic from the viewpoint of cost that, when a plurality of observation targets is observed, the phase contrast microscope is provided for each observation target. Therefore, the observation target or the phase contrast microscope needs to be moved. However, when the observation target or the phase contrast microscope is moved, the distance from a phase plate to a reflection surface varies due to the limitation of the accuracy of the stop position of the observation target or the phase contrast microscope.

Herein, the phase contrast microscope has the phase plate having a phase film region in which the phase is changed by <NUM>/<NUM> wavelength and a transmission region in which the phase is not changed. By the passage of the directly reflected light beam through the phase film region and the passage of the diffracted and reflected light beam through the transmission region, the phase of the directly reflected light beam is changed by <NUM>/<NUM> wavelength.

In the phase contrast microscope described in Patent Literature <NUM>, the illumination light beam emitted from the illumination optical system toward the observation target is tilted with respect to the optical axis. Therefore, when the distance from the phase plate to the reflection surface varies, a position (convergence point) where the directly reflected light beams are converged on the phase plate is changed. When the directly reflected light beam does not pass through the phase film region due to variations in the convergence point, the contrast varies, so that a good optical image obtained by the previous adjustment is not obtained. Therefore, work is required which adjusts the distance from the phase contrast microscope to the observation target, i.e., the distance from the phase plate to the reflection surface, such that the directly reflected light beam passes through the phase film region whenever the phase contrast microscope is moved, which causes a workability reduction.

The present invention has been made in view of the above-descried circumstances. It is an object of the present invention to provide an observation device capable of obtaining a good optical image by keeping contrast constant while eliminating the necessity of work for adjusting the distance from a phase plate to a reflection surface.

The observation device of the present invention can keep contrast constant while eliminating the necessity of work for adjusting the distance from a phase contrast microscope to an observation target and can obtain a good optical image.

Hereinafter, preferable embodiments of the present invention are described. It is a matter of fact that this embodiment is merely one embodiment of the present invention and can be changed without changing the gist of the present invention.

As illustrated in <FIG>, an observation device <NUM> according to this embodiment is a device observing observation targets <NUM> which are biological cells. The observation device <NUM> includes an incubator <NUM>, an epi-illumination phase contrast microscope (hereinafter referred to as a microscope) <NUM>, a moving device <NUM>, a computer for observation <NUM>, a display device <NUM>, and an operation device <NUM>. The incubator <NUM> includes an atmosphere control mechanism <NUM>. The microscope <NUM> includes an illumination light beam source <NUM>. In the microscope <NUM>, an image pickup device <NUM> is provided. The computer for observation <NUM> includes a light beam source control portion <NUM>, an image processing portion <NUM>, and a movement control portion <NUM>.

Elements configuring the observation device <NUM> roughly function as follows. The illumination light beam source <NUM> illuminates the observation targets <NUM>. The microscope <NUM> acquires an optical image of the illuminated observation target <NUM>. The moving device <NUM> moves the microscope <NUM> such that the microscope <NUM> can acquire the optical image of the observation target <NUM>. The image pickup device <NUM> photoelectrically converts the optical image acquired by the microscope <NUM> to create image data. The image processing portion <NUM> corrects the image data obtained by the image pickup device <NUM>. The display device <NUM> displays the image data before the correction and after the correction. The movement control portion <NUM> controls the driving of the moving device <NUM>. The light beam source control portion <NUM> controls the driving of the illumination light beam source <NUM>. The operation device <NUM> can be input commands for the image processing portion <NUM> and can be input commands for the movement control portion <NUM>. The operation device <NUM> is a keyboard and a mouse, for example. A user can operate the operation device <NUM> to set processing contents to the image processing portion <NUM> and control the movement of the microscope <NUM> through the driving of the moving device <NUM>. Thus, the observation target <NUM> is observed by the observation device <NUM>.

The incubator <NUM> includes a chassis <NUM> having an opening <NUM>, a lid body <NUM> capable of opening/closing the opening <NUM>, and a partition wall <NUM> arranged in the chassis <NUM> as illustrated in <FIG>. Hereinafter, a vertical direction <NUM>, a forward and backward direction <NUM>, and a right and left direction <NUM> are defined based on the attitude of the incubator <NUM> illustrated in <FIG>. The opening <NUM> is opened in the forward and backward direction <NUM>. An internal space <NUM> of the incubator <NUM> is defined by the chassis <NUM> and the lid body <NUM>. The outer shape of the chassis <NUM> and the lid body <NUM> is a rectangular parallelepiped shape. The shape of the internal space <NUM> is also a rectangular parallelepiped shape. In the internal space <NUM>, airtightness and watertightness are maintained against the open air of the incubator <NUM> in a state where the lid body <NUM> is closed.

As illustrated in <FIG>, the partition wall <NUM> partitions the internal space <NUM> into a culture chamber <NUM> in the upward and a machine chamber <NUM> in the downward. In the culture chamber <NUM>, four petri dishes <NUM> are arranged. In each petri dish <NUM>, the observation target <NUM> (<FIG>, <FIG>) which is a biological cell is housed. In the machine chamber <NUM>, the microscope <NUM> mounted with the image pickup device <NUM> and the moving device <NUM> are housed.

The partition wall <NUM> is a flat plate shape having a square shape as viewed from the vertical direction <NUM>. The partition wall <NUM> has a frame plate <NUM> having four openings <NUM> and a transparent plate <NUM> fitted into each of the four openings <NUM>. The transparent plates <NUM> are formed of a material transmitting a light beam, and thus can transmit a light beam in the vertical direction <NUM>. The material of the transparent plates <NUM> is glass or acryl, for example. The four transparent plates <NUM> are located at the vertex positions of the square as viewed from the vertical direction <NUM>.

As illustrated in <FIG>, the petri dish <NUM> has a lower dish <NUM> and an upper dish <NUM> so as to be nested. Both the lower dish <NUM> and the upper dish <NUM> are shallow cylindrical containers having a bottom surface. The upper dish <NUM> is larger than the lower dish <NUM>. By placing the lower dish <NUM> on the upper dish <NUM>, the inside of the petri dish <NUM> is closed. Both the lower dish <NUM> and the upper dish <NUM> are formed of a material transmitting a light beam, for example, polystyrene resin.

As illustrated in <FIG>, the observation device <NUM> includes reflectors <NUM> reflecting illumination light beams <NUM> from the microscope <NUM>. The reflector <NUM> is fixed to the upper surface of the upper dish <NUM>. The reflector <NUM> has a disk shape. The reflector <NUM> is formed of stainless steel in this embodiment. A reflection surface 49a (undersurface 49a) provided on the undersurface of the reflector <NUM> is mirror finished so as to be able to reflect a light beam.

The atmosphere control mechanism <NUM> of the incubator <NUM> is described referring to <FIG> again. The atmosphere control mechanism <NUM> is a mechanism of controlling the atmosphere (temperature and humidity) of the culture chamber <NUM> and can control the atmosphere independently of the atmosphere of the machine chamber <NUM>. Specifically, the atmosphere control mechanism <NUM> includes a heating device <NUM>, a temperature sensor <NUM>, a humidifying device <NUM>, a humidity sensor <NUM>, a computer for culture <NUM>, an operation device <NUM>, and a display device <NUM>. The heating device <NUM> can increase the temperature of the culture chamber <NUM>. The temperature sensor <NUM> can detect the temperature of the culture chamber <NUM>. The humidifying device <NUM> can increase the humidity of the culture chamber <NUM>. The humidity sensor <NUM> can detect the humidity of the culture chamber <NUM>. The computer for culture <NUM> can control an operation of the heating device <NUM> and an operation of the humidifying device <NUM>. The operation device <NUM> is a device capable of specifying target values of the temperature and the humidity of the culture chamber <NUM>. The display device <NUM> can display the temperature detected by the temperature sensor <NUM>, the humidity detected by the humidity sensor <NUM>, and the target values specified by the operation device <NUM>. The computer for culture <NUM> controls the operation of the heating device <NUM> and the operation of the humidifying device <NUM> such that detection values of the temperature and the humidity obtained by the temperature sensor <NUM> and the humidity sensor <NUM> are in agreement with the specified target values of the temperature and the humidity. Thus, the atmosphere of the culture chamber <NUM> is controlled.

As illustrated in <FIG> and <FIG>, the moving device <NUM> is a device moving the microscope <NUM> such that the microscope <NUM> is located immediately under the petri dish <NUM> housing the observation target <NUM>. The moving device <NUM> includes a bottom portion <NUM>, a body <NUM>, a first arm <NUM>, and a second arm <NUM>. The bottom portion <NUM> is fixed to the chassis <NUM> of the incubator <NUM>. The body <NUM> is fixed to the bottom portion <NUM> and houses a driving mechanism of driving the first arm <NUM> and the second arm <NUM> and a control mechanism. The first arm <NUM> and the second arm <NUM> are configured into articulated arms. A base end portion of the first arm <NUM> is coupled to the body <NUM> to be rotatable around the axis in the vertical direction <NUM>. A base end portion of the second arm <NUM> is coupled to a tip portion of the first arm <NUM> to be rotatable around the axis in the vertical direction <NUM>. To a tip portion of the second arm <NUM>, the microscope <NUM> is fixed. The microscope <NUM> is movable by the driving of the moving device <NUM> in the horizontal direction, i.e., both the forward and backward direction <NUM> and the right and left direction <NUM>. Therefore, the moving device <NUM> can move immediately under any of the four petri dishes <NUM> located on the upper side of the partition wall <NUM>.

The microscope <NUM> is described with reference to <FIG>. The microscope <NUM> includes an illumination light beam source <NUM>, an illumination optical system <NUM>, an observation optical system <NUM>, and an image pickup device <NUM>. The illumination optical system <NUM> emits the illumination light beams <NUM> from the illumination light beam source <NUM> to the observation target <NUM>. The observation optical system <NUM> forms an optical image of the observation target <NUM> from reflected light beams <NUM> generated by the reflection of the illumination light beams <NUM> by the reflection surface after passing through the observation target <NUM>. The image pickup device <NUM> photoelectrically converts the optical image of the observation target <NUM> to create image data of the observation target <NUM>.

The illumination light beam source <NUM> is a light beam source emitting the illumination light beams <NUM>. The illumination light beam source <NUM> is a wavelength variable light beam source, and thus can change the wavelength of the illumination light beams <NUM>. The switching of the wavelengths is performed by an operation of the operation device <NUM> by a user (<FIG>). When a target value of the wavelength is specified by the operation of the operation device <NUM>, the light beam source control portion <NUM> (<FIG>) controls the illumination light beams <NUM> such that the illumination light beams <NUM> of the wavelength of the target value are emitted.

The microscope <NUM> is an epi-illumination microscope. The illumination optical system <NUM> and the observation optical system <NUM> are arranged on the same side with respect to the observation target <NUM>, lower side in this embodiment. In connection therewith, the illumination light beam source <NUM> is also arranged on the same side (lower side) of the illumination optical system <NUM> and the observation optical system <NUM>. Since the illumination optical system <NUM> and the observation optical system <NUM> are not individually arranged on each of both sides of the observation target <NUM>, and therefore the microscope <NUM> is compactly configured.

The illumination optical system <NUM> includes a half mirror <NUM>, a first objective lens <NUM>, and a second objective lens <NUM>. The half mirror <NUM> reflects the illumination light beams <NUM> from the illumination light beam source <NUM> and emits the illumination light beams <NUM> upward toward the observation position where the observation target <NUM> is arranged. Between the half mirror <NUM> and the observation target <NUM>, the first objective lens <NUM> and the second objective lens <NUM> are arranged. The first objective lens <NUM> is arranged on a side close to the half mirror <NUM> and the second objective lens <NUM> is arranged on a side close to the observation target <NUM>. The illumination light beams <NUM> from the half mirror <NUM> are refracted on the first objective lens <NUM> and the second objective lens <NUM>, transmit through the transparent plate <NUM> and the lower dish <NUM> (<FIG>), pass through the observation target <NUM>, and then reach the reflection surface 49a. An optical axis <NUM> is a center axis of a luminous flux of the illumination light beams <NUM> emitted from the half mirror <NUM> and is also a center axis of the first objective lens <NUM> and the second objective lens <NUM>. The optical axis <NUM> is along the vertical direction <NUM>.

The illumination light beams <NUM> emitted from the second objective lens <NUM> are collimated light beams parallel to the optical axis <NUM>. The refractive index and the arrangement of the first objective lens <NUM> and the second objective lens <NUM> are set such that such collimated light beams are emitted.

The illumination light beams <NUM> pass through the observation target <NUM>, and then reflected on the reflection surface 49a to be the reflected light beams <NUM>. The reflected light beams <NUM> include directly reflected light beams 62A which are not diffracted inside the observation target <NUM> when passing through the observation target <NUM> after reflected on the reflection surface 49a of the reflector <NUM> and diffracted and reflected light beams 62B which are reflected on the reflection surface 49a of the reflector <NUM>, and then diffracted inside the observation target <NUM> when passing through the observation target <NUM> to be delayed in phase by <NUM>/<NUM> wavelength. In <FIG>, the illumination light beams <NUM> are illustrated by the solid lines, the directly reflected light beams 62A are illustrated by the solid lines, and the diffracted and reflected light beams 62B are illustrated by the dashed lines. The reflected light beams <NUM> collectively refer to the directly reflected light beam 62A and the diffracted and reflected light beam 62B.

In this embodiment, the reflector <NUM> is arranged above the observation target <NUM>, and therefore the light beam amount of the reflected light beams <NUM> increases due to the reflection of a larger number of light beams on the reflection surface 49a of the reflector <NUM>. The directly reflected light beams 62A are light beams passing through the observation target <NUM> twice before and after the reflection and not diffracted in the observation target <NUM> among light beams reflected on the reflection surface 49a of the reflector <NUM>. The diffracted and reflected light beams 62B are light beams passing through the observation target <NUM> twice before and after the reflection and diffracted in the observation target <NUM> among light beams reflected on the reflection surface 49a of the reflector <NUM>.

The observation optical system <NUM> includes the first objective lens <NUM>, the second objective lens <NUM>, the half mirror <NUM>, a phase plate <NUM>, and an imaging surface <NUM>. The imaging surface <NUM> is a light beam receiving surface formed on the surface of the image pickup device <NUM> in this embodiment. Herein, the first objective lens <NUM> and the second objective lens <NUM> and the half mirror <NUM> are shared between the illumination optical system <NUM> and the observation optical system <NUM>. The reflected light beams <NUM> reflected on the reflection surface 49a are refracted on the first objective lens <NUM> and the second objective lens <NUM> via the transparent plate <NUM> and the lower dish <NUM> (<FIG>), transmit through the half mirror <NUM> and the phase plate <NUM>, and then reach the imaging surface <NUM>.

The phase plate <NUM> has a phase film region 57A where a phase is shifted and a transmission region 57B where a phase is not changed. The phase film region 57A is a circular region around the optical axis <NUM> in the phase plate <NUM>. The transmission region 57B is an annular region around the optical axis <NUM> in the phase plate <NUM> and is located on the outside of the phase film region 57A. The phase film region 57A and the transmission region 57B are formed of a material transmitting a light beam. When a light beam passes through the phase film region 57A, the phase of the light beam is shifted by <NUM>/<NUM> wavelength. In this embodiment, the phase is delayed by <NUM>/<NUM> wavelength but conversely the phase may be advanced by <NUM>/<NUM> wavelength. On the other hand, the transmission region 57B does not change the phase of a light beam passing through the transmission region 57B.

The refractive index and the arrangement of the first objective lens <NUM> and the second objective lens <NUM> and the size (radius) of the phase film region 57A are set such that the directly reflected light beams 62A pass through the phase film region 57A among the reflected light beams <NUM>. Therefore, the phase of the directly reflected light beams 62A are shifted in the phase film region 57A. On the other hand, the diffracted and reflected light beams 62B pass through the transmission region 57B, and therefore the phase of the diffracted and reflected light beams 62B is not changed. Since the phase of the directly reflected light beams 62A is delayed by <NUM>/<NUM> wavelength, the phase contrast between the directly reflected light beams 62A and the diffracted and reflected light beams 62B becomes <NUM> after passing through the phase plate <NUM>. When the phase of the directly reflected light beams 62A is advanced by <NUM>/<NUM> wavelength, the phase contrast between the directly reflected light beams 62A and the diffracted and reflected light beams 62B becomes <NUM>/<NUM> wavelength after passing through the phase plate <NUM>.

A luminous flux of the reflected light beams <NUM> reflected after passing through each position of the observation target <NUM> is converged on the imaging surface <NUM>. When the phase of the directly reflected light beams 62A is delayed by <NUM>/<NUM> wavelength, the directly reflected light beams 62A and the diffracted and reflected light beams 62B are intensified with each other on the imaging surface <NUM>. Therefore, an optical image with bright contrast is obtained in which the observation target <NUM> is bright and the background is dark. When the phase of the directly reflected light beams 62A is advanced by <NUM>/<NUM> wavelength, an optical image with dark contrast is conversely obtained in which the observation target <NUM> is dark and the background is bright.

The optical image formed on the imaging surface <NUM> is photoelectrically converted by the image pickup device <NUM>, and then image data is created. The image data is corrected in the image processing portion <NUM> (<FIG>), and then displayed on the display device <NUM>.

The image processing portion <NUM> is described referring to <FIG> again. The image processing portion <NUM> has a filter function of removing noise information with respect to the image data obtained by the image pickup device <NUM>. This filter function is a function of removing noise information due to dust adhering to the second objective lens <NUM> or the like from the image data based on two image data obtained by the illumination light beams <NUM> of two different wavelengths.

The change in the wavelength of the illumination light beams <NUM> is equal to a change in the optical path length from the observation target <NUM> to the imaging surface <NUM>. By this change, the position where the reflected light beams <NUM> are converged varies. When the reflected light beams <NUM> are converged on the imaging surface <NUM>, the optical image is focused. However, when the reflected light beams <NUM> are not converged on the imaging surface <NUM>, the optical image is not focused. More specifically, focused image data and not-focused image data are created by the illumination light beams <NUM> of two different wavelengths. Herein, the optical image formed by dust adhering to the second objective lens <NUM> or the like is not affected by the variation in the optical path length, and therefore the luminance does not vary. Then, pixels of a portion where the variation in the luminance is relatively small are specified in the two image data obtained by the change in the wavelength, whereby the noise information contained in the image data can be specified. Further, information of the pixels containing the noise information is deleted, whereby the image data from which the noise information is deleted can be created.

Before the image processing portion <NUM> is caused to exhibit the filter function, the light beam source control portion <NUM> controls the illumination light beam source <NUM>, so that the wavelength of the illumination light beams <NUM> is changed. Thus, image data obtained by the illumination light beams <NUM> of a first wavelength and image data obtained by illumination light beams of a second wavelength are obtained. Herein, the image data is an aggregate of the pixels arranged in two-dimensional coordinates. Each pixel has information of a luminance value as color information.

The image processing portion <NUM> includes a calculation portion <NUM>, a recognition portion <NUM>, and a creation portion <NUM>. The calculation portion <NUM> calculates the difference between the luminance values for each pixel of the same coordinate with respect to the two image data obtained by the illumination light beams <NUM> of the two different wavelengths. The recognition portion <NUM> recognizes a pixel where the difference is smaller than a predetermined value as a noise pixel containing incorrect information. The creation portion <NUM> deletes the noise pixels from each of the two image data to create two corrected image data. Thus, the presence or absence of the noise information contained in the image data is recognized and further the image data from which the noise information is deleted is created.

According to the observation device <NUM> of this embodiment, the collimated illumination light beams <NUM> are emitted from the illumination optical system <NUM>, and therefore the collimated reflected light beams <NUM> enter the observation optical system <NUM>. The reflected light beams <NUM> are parallel to the optical axis <NUM>, and therefore, even when the distance from the microscope <NUM> to the observation target <NUM> varies, the convergence point in the phase plate <NUM> of the directly reflected light beams 62A does not vary. Therefore, even when the distance varies by moving the microscope <NUM>, the contrast can be kept constant and a good optical image is obtained.

Further, the observation device <NUM> includes the moving device <NUM>, and therefore there is no necessity of manually moving the observation targets <NUM> or the microscope <NUM>. Therefore, the workability is improved.

Further, the microscope <NUM> is arranged in the incubator <NUM>, and therefore there is no necessity of opening the incubator <NUM> and moving the microscope <NUM> to the incubator <NUM> from the outside in order to observe the observation targets <NUM>. Therefore, there is also no necessity of maintaining the external environment of the incubator <NUM> in an aseptic state so as not to cause problems even when the incubator <NUM> is opened in each observation of the observation targets <NUM>. Hence, man hours and cost required for the observation of the incubator <NUM> are reduced. Further, the airtightness and the watertightness of the culture chamber <NUM> are maintained against the machine chamber <NUM>, and therefore the atmosphere of the machine chamber <NUM> is separated from the atmosphere of the culture chamber <NUM>. Therefore, even when a temperature difference occurs between the culture chamber and the machine chamber, it is suppressed that dew condensation occurs in the epi-illumination phase contrast microscope in the machine chamber.

Further, the wavelength of the illumination light beams <NUM> is switchable between a plurality of different wavelengths. Therefore, the image data amount in the cell boundary of the observation targets <NUM> can be reduced by shading off the obtained image and the measurement of the number of cells can be facilitated. Further, a portion formed by foreign substances, such as dust, adhering to the second objective lens <NUM> among parts contained in the optical image on the imaging surface <NUM> is not affected by a change in the wavelength of the illumination light beams <NUM>. Therefore, it can be specified by the change in the wavelength of the illumination light beams <NUM> whether each part of the optical image is an image of the observation target <NUM> or an image formed by the foreign substances.

Further, the pixel having the difference between the luminance values smaller than a predetermined value is recognized as the noise pixel containing incorrect information and two corrected image data from which the noise pixels are deleted are created. Hence, influence of the incorrect information caused by dust can be eliminated in the image data of the observation target <NUM>.

Further, the reflected light beams <NUM> from the observation target <NUM> and the reflected light beams <NUM> from the reflector <NUM> enter the observation optical system <NUM>. Since the amount of the light beams entering the observation optical system <NUM> increases, the image data of the observation target <NUM> with higher identifiability can be obtained.

Further, the reflector <NUM> is fixed to the upper dish <NUM>, and therefore the reflector <NUM> can be easily arranged.

In this embodiment, the moving device <NUM> is a device moving the microscope <NUM> but is not limited to this configuration. The moving device <NUM> may be a device moving the observation target <NUM> and the microscope <NUM> relative to each other. The moving device <NUM> may be a device moving the observation targets <NUM> instead of moving the microscope <NUM>. Further, the moving device <NUM> is provided in order to automatically move the microscope <NUM> in this embodiment. When the moving device <NUM> is not an indispensable constituent component and the microscope <NUM> or the observation targets <NUM> are manually moved, the moving device <NUM> may not be provided.

In this embodiment, the reflector <NUM> provided with the reflection surface 49a on the undersurface is provided. The reflector <NUM> is not an indispensable constituent component and the reflector <NUM> may not be provided. In this case, an optical image of the observation target <NUM> is formed in the microscope <NUM> based on the reflected light beams <NUM> reflected on the surface of another reflection surface after passing through the observation target <NUM>. For example, the undersurface of the upper dish <NUM> or the undersurface of the lower dish <NUM> when the lower dish <NUM> is further placed on the upper side in the vertical direction <NUM> of the upper dish <NUM> in <FIG>, for example, can also be utilized as the reflection surface similarly to the reflection surface 49a.

In this embodiment, the reflector <NUM> is a plate material fixed to the upper dish <NUM> of the petri dish <NUM> but is not limited to this configuration. The reflector <NUM> may be arranged above the observation target <NUM> and be able to reflect the illumination light beams <NUM>. A position where the reflector <NUM> is arranged or a target to which the reflector <NUM> is fixed is not limited. The reflector <NUM> may be arranged in the culture chamber <NUM> and fixed to the chassis <NUM> of the incubator <NUM>.

Claim 1:
An observation device (<NUM>) comprising:
an epi-illumination phase contrast microscope (<NUM>) including an illumination light beam source (<NUM>), an illumination optical system (<NUM>) emitting an illumination light beam from the illumination light beam source (<NUM>) to an observation target (<NUM>) which is a biological cell, and an observation optical system (<NUM>) forming an optical image of the observation target from one or more reflected light beams obtained by reflection of the illumination light beam after passing through the observation target (<NUM>),
the observation optical system (<NUM>) including a phase plate (<NUM>) changing a phase of a directly reflected light beam reflected on a reflection surface among the reflected light beams, and
both the illumination optical system (<NUM>) and the observation optical system (<NUM>) being arranged under the observation target;
an image pickup device (<NUM>) photoelectrically converting the optical image obtained by the observation optical system (<NUM>) to create image data of the observation target; and
a display device (<NUM>) displaying the image data,
characterized in that
the illumination light beam emitted from the illumination optical system and passing through the observation target is a collimated light beam which is parallel to an optical axis (<NUM>) of the illumination optical system (<NUM>).