Focusing device including a differential interference prism

A focusing device that includes a differential interference prism used in differential interference observation in a focusing detection optical system includes: a light source that emits light with which a measurement surface of an observation sample is irradiated; a photo detection unit that detects light from the measurement surface; a focusing detection unit that detects an error signal near a focusing point of the measurement surface on the basis of an output signal from the photo detection unit; and a condition changing unit that changes an acquisition condition of the error signal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2013-125005, filed Jun. 13, 2013, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a focusing device that includes a differential interference prism used in differential interference observation in a focusing detection optical system.

2. Description of the Related Art

Conventionally, a microscope device has been used that includes a focusing detection mechanism (e.g., an active AF (Auto Focus) mechanism) and a differential interference observation mechanism. In such a microscope device, a portion of a focusing detection optical system is used in common with a portion of a differential interference observation optical system, and a differential interference prism is provided to the portion of the focusing detection optical system. Therefore, also in the focusing detection by the focusing detection mechanism in differential interference observation, light (in this case, light for focusing detection) passes through the differential interference prism.

As an example, in a focusing device described in Japanese Laid-Open Patent Publication No. 2000-199846, when it is determined that focusing is not performed, a differential interference prism is driven outside an optical path, and a focusing determination is performed. After focusing is performed, the differential interference prism is driven to return in the optical path with a focusing position maintained so as to enable focusing detection.

In recent years, not only enabling highly accurate focusing detection but also shortening the time needed for the focusing detection has been desired strongly.

SUMMARY OF THE INVENTION

One aspect of the present invention is related to a focusing device that includes a differential interference prism used in differential interference observation in a focusing detection optical system, and the focusing device includes a light source, a photo detection unit, a focusing detection unit, and a condition changing unit. The light source emits light with which a measurement surface of an observation sample is irradiated. The photo detection unit detects light from the measurement surface. The focusing detection unit detects an error signal near a focusing point of the measurement surface on the basis of an output signal from the photo detection unit. The condition changing unit changes an acquisition condition of the error signal.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Described below are embodiments of the present invention with reference to the drawings.

FIG. 1illustrates an example of a configuration of a microscope device that includes a focusing device and a differential interference observation mechanism in Embodiment 1 of the present invention.

As illustrated inFIG. 1, a microscope device100includes a microscope body200, a PC (Personal Computer)300, and a monitor400, and is configured to transmit/receive signals between the microscope body200and the PC300and between the PC300and the monitor400.

The microscope body200includes a focusing detection optical system and a differential interference observation optical system as an optical system, and a portion of the focusing detection optical system is used in common with a portion of the differential interference observation optical system.

The focusing detection optical system includes an AF (Auto Focus) light source201, a PBS (Polarization Beam Splitter)202, a λ/4 plate203, half mirrors204and205, a DIC (Differential Interference Contrast) prism (a differential interference prism)206, an objective lens207, and a PD (Photo Detector)208. The AF light source201emits a laser beam (e.g., a P-polarized laser beam) as light for focusing detection. The AF light source201is an example of a light source that emits light with which a measurement surface of an observation sample is irradiated. The PBS202transmits a P polarization component of incident light and reflects an S polarization component of the incident light. The λ/4 plate203converts light from the PBS202into circularly polarized light, and converts light from the half mirror204into linearly polarized light. The half mirror204as a focusing detection optical system reflects incident light. The half mirror205as a focusing detection optical system transmits incident light. The PD208is a bipartite photo detector, and the PD208detects light from the PBS202and outputs detection results to the AF control unit220. The PD208is an example of a photo detector that detects light from a measurement surface of an observation sample.

In the focusing detection optical system as described above, only a P polarization component of a laser beam (e.g., a P-polarized laser beam) emitted from the AF light source201passes through the PBS202and is converted into circularly polarized light by the λ/4 plate203. Then, the circularly polarized light is reflected by the half mirror204and passes through the half mirror205, and is applied to the observation sample209via the DIC prism206and the objective lens207. The reflected light from the observation sample209passes through the half mirror205via the objective lens207and the DIC prism206, and is reflected by the half mirror204. Further, the reflected light is converted into linearly polarized light by the λ/4 plate203, and only an S polarization component thereof is reflected by the PBS202and is received by the PD208.

On the other hand, the differential interference observation optical system includes an observation light source210, a PO (Polarizer)211, half mirrors204and205, a DIC prism206, an objective lens207, an AN (Analyzer)212, and an eyepiece213. The observation light source210emits light for observation. The PO211converts the light from the observation light source210into light having a specific polarization component. The half mirror205as a differential interference observation optical system reflects the light from the PO211, and transmits light from the DIC prism206. The half mirror204as a differential interference observation optical system transmits light from the half mirror205. The AN212transmits only a specific polarization component of the light from the half mirror204. A combination of the PO211and the AN212realizes a crossed nicol state needed for differential interference observation. The eyepiece213guides the light from the AN212to the naked eye of a user (an observer).

In the differential interference observation optical system as described above, the light emitted from the observation light source210is converted into light having a specific polarization component by the PO211, is reflected by the half mirror205, and is applied to the observation sample209via the DIC prism206and the objective lens207. Then, the reflected light from the observation sample209passes through the half mirrors205and204via the objective lens207and the DIC prism206, and then only a specific polarization component of the reflected light from the observation sample209is transmitted by the AN212and is guided to the naked eye of a user by the eyepiece213.

The microscope body200further includes an AF light source control unit214, an observation light source control unit215, a shearing amount detection unit216, a DIC prism driving unit217, a stage218, a stage driving unit219, an AF control unit220, and a microscope main control unit221. The AF light source control unit214controls the AF light source201under the control of the microscope main control unit221. The AF light source control unit214controls, for example, an output, a duty ratio, and the like of a laser beam emitted from the AF light source201. The observation light source control unit215controls the observation light source210under the control of the microscope main control unit221. The shearing amount detection unit216detects a shearing amount of the DIC prism206and outputs detection results to the AF control unit220. The shearing amount refers to a displacement amount of a DIC prism position from an origin position within a movable range of the DIC prism. The shearing amount is defined as above because, when the DIC prism position is changed, an amount of shear is also changed. The DIC prism driving unit217drives (moves) the DIC prism206under the control of the microscope main control unit221. On the stage218, the observation sample209is mounted. The stage driving unit219drives (moves) the stage218in XYZ directions under the control of the microscope main control unit221. An XY direction is a direction parallel to a stage plane on which the observation sample209is mounted, and a Z direction is a direction vertical to the stage plane. The AF control unit220controls the AF operation or the like under the control of the microscope main control unit221. A configuration of the AF control unit220is described below in detail with reference toFIG. 2. The microscope main control unit221controls the whole operation of the microscope body200.

The PC300includes an operation unit, such as a keyboard or a mouse, and receives various instructions from a user. The PC300may also receive various instructions from a user via a touch panel provided on a display screen of the monitor400. When the PC300receives various instructions from a user, the PC300outputs, for example, corresponding instruction signals to the microscope main control unit221. The PC300also displays various kinds of information on the monitor400.

FIG. 2illustrates an example of a configuration of the AF control unit220in this embodiment.

As illustrated inFIG. 2, the AF control unit220includes an integrator231(an integrator A), an integrator232(an integrator B), a signal processing unit233, a storage unit234, and a condition changing unit235.

The integrator231integrates output signals from one side (PDA) of the PD208that is a bipartite photo detector during an integration time that is within a range of a set maximum integration time and at which an S/N ratio is the greatest. The integrator232integrates output signals from the other side (PDB) of the PD208that is the bipartite photo detector during an integration time that is within a range of a set maximum integration time and at which an S/N ratio is the greatest. The maximum integration time and the integration time that is within a range of the maximum integration time and at which an S/N ratio is the greatest in the integrator231are the same as those in the integrator232. The integrators231and232are examples of an integration unit that integrates output signals from a photo detection unit within a range of a maximum integration time.

The signal processing unit233includes a gain changing unit236(a gain changing unit A), a gain changing unit237(a gain changing unit B), and arithmetic units238,239, and240.

The gain changing unit236changes the signal intensity of an output signal from the integrator231according to a set gain. The gain changing unit237changes the signal intensity of an output signal from the integrator232according to a set gain. The gains in the gain changing unit236and237are the same values.

The arithmetic unit238calculates A-B using an output signal A from the gain changing unit236and an output signal B from the gain changing unit237. The arithmetic unit239calculates A+B using the output signal A from the gain changing unit236and the output signal B from the gain changing unit237. Hereinafter, an arithmetic result signal of the arithmetic unit239is also referred to as an AF signal or an AF signal intensity. The arithmetic unit240calculates (A−B)/(A+B) using an arithmetic result signal of the arithmetic unit238and an arithmetic result signal of the arithmetic unit239. An arithmetic result signal of the arithmetic unit240is also an error signal near a focusing point of a measurement surface of the observation sample209. In the AF control unit220, according to the error signal, a position (a Z-direction position) of the stage218where the error signal is 0 is detected as a focusing position, a driving signal for moving the stage218to the focusing position is output to the stage driving unit219via the microscope main control unit221, and as a result, the AF is performed.

The storage unit234stores a shearing amount management table241. The shearing amount management table241is generated on the basis of an output signal from the shearing amount detection unit216and the AF signal in accordance with the shearing amount management table generation procedure, as described below in detail. The shearing amount management table241is an example of a table that indicates a correspondence relation between a shearing amount of a differential interference prism and a signal intensity range of a signal based on an output signal from a photo detection unit.

The condition changing unit235changes a shearing amount of the DIC prism206as an acquisition condition of an error signal on the basis of the shearing amount management table241and an output signal from the shearing amount detection unit216, as described below in detail. The shearing amount is changed in response to the output of a driving signal for changing the shearing amount of the DIC prism206to the DIC prism driving unit217via the microscope main control unit221.

In the AF control unit220, a configuration including at least the integrators231and232and the signal processing unit233is an example of a focusing detection unit that detects an error signal near a focusing point of a measurement surface of an observation sample on the basis of an output signal from a photo detection unit.

Described next is the shearing amount management table generation procedure.

Once this procedure has been performed, the procedure does not need to be performed again even when an observation sample is changed afterwards, but the procedure may be performed every time the observation sample is changed.

The shearing amount management table generation procedure is performed in accordance with processes (1)-(6) described below.

(1) First, a user provides an instruction via the PC300so as to remove the DIC prism206from an optical path, perform the AF for the observation sample209that is mounted on the stage218in this state, and move the stage218to a focusing position. As a result, the position of the stage218is a position in which a greater AF signal intensity is acquired as an AF signal intensity acquired in the process (4) described below.
(2) Then, the user provides an instruction via the PC300so as to return the DIC prism206to the optical path. The position of the DIC prism206in this state is determined to be an initial position.
(3) Then, the user provides an instruction to generate a shearing amount management table via the PC300so as to start an AF signal intensity acquisition operation. When the AF signal intensity acquisition operation is started, a laser beam starts to be emitted from the AF light source201, and in the AF control unit220, a process of acquiring an AF signal intensity from an output signal from the PD208that receives a reflected light from the observation sample209is started.
(4) Then, the user provides an instruction via the PC300so as to change the shearing amount of the DIC prism206by a specified amount. Namely, the position of the DIC prism206is moved by the specified amount.
(5) Then, the user provides an instruction via the PC300so as to start the data registration in the shearing amount management table241. In this data registration, a shearing region can be registered manually or automatically. The shearing region is defined by a prescribed signal intensity range. For example, a shearing region in which an acquired AF signal intensity is a maximum signal intensity (Peak) is defined to be the shearing region 0. A shearing region in which the acquired AF signal intensity is below the Peak and 50% or more of the Peak is defined to be the shearing region 1. A shearing region in which the acquired AF signal intensity is less than 50% of the Peak is defined to be the shearing region 2. Here, the maximum signal intensity (Peak) represents an available maximum AF signal intensity. As described above, the shearing region is defined by the signal intensity range, and therefore the shearing region may also be referred to as a signal intensity range. The number of shearing regions and a signal intensity range that defines each of the shearing regions may be changed arbitrarily.

In a data registration in which the shearing region is manually registered, a current shearing amount (a shearing amount detected by the shearing amount detection unit216) is automatically registered, and the user registers a shearing region via the PC300. An AF signal intensity acquired at this point is displayed on the monitor400, for example, and the user can register the shearing region on the basis of the AF signal intensity.

In a data registration in which the shearing region is automatically registered, when the shearing amount of the DIC prism206is changed by a specified amount, a current shearing amount, an AF signal intensity acquired currently, and a shearing region that the AF signal intensity belongs to are automatically registered.

This automatic registration is performed, for example, by the AF control unit220.

(6) The above processes (4) and (5) are repeated. When the shearing amount reaches the limit (a maximum), the generation of the shearing amount management table241is finished automatically. Alternatively, the user provides an instruction via the PC300so as to finish the generation of the shearing amount management table241.

As a result, a shearing amount management table241that has been generated by the manual registration of the shearing region is a table that indicates a correspondence relation between a shearing amount and a shearing region. A shearing amount management table241that has been generated by the automatic registration of the shearing region is a table that indicates a correspondence relation between a shearing amount, an AF signal intensity, and a shearing region.

In this shearing amount management table generation procedure, for example, when a user provides an instruction to generate the shearing amount management table via the PC300, the above processes (2) to (6) may be performed automatically.

FIG. 3,FIG. 4,FIG. 5, andFIG. 6are diagrams that illustrate examples of the shearing amount management table241that has been generated in accordance with the shearing amount management table generation procedure.

A shearing amount management table241illustrated inFIG. 3is an example in which, in the shearing amount management table generation procedure, shearing regions have been classified into three categories and the shearing regions have been registered automatically. In this example, a shearing region in which an acquired AF signal intensity is a maximum signal intensity (Peak) is defined to be the shearing region 0. A shearing region in which the acquired AF signal intensity is below the Peak and is 50% or more of the Peak is defined to be the shearing region 1. A shearing region in which the acquired AF signal intensity is less than 50% of the Peak is defined to be the shearing region 2. In this case, in the shearing region 0, a shearing amount=200. In the shearing region 1, 100≦ shearing amount<200, 200<shearing amount<400, and 900≦ shearing amount≦1000. In the shearing region 2, 0≦shearing amount<100, and 400≦shearing amount<900.

A shearing amount management table241illustrated inFIG. 4is an example in which, in the shearing amount management table generation procedure, shearing regions have been classified into two categories and the shearing regions have been registered manually. In this example, a shearing region in which an acquired AF signal intensity is 50% or more of the maximum signal intensity (Peak) is defined to be the shearing region 1. A shearing region in which the acquired AF signal intensity is less than 50% of the Peak is defined to be the shearing region 2. In this case, in the shearing region 1, 100≦shearing amount<400, and 900 shearing amount≦1000, and in the shearing region 2, 0≦shearing amount<100, and 400≦shearing amount<900.

A shearing amount management table241illustrated inFIG. 5is an example in which, in the shearing amount management generation procedure, shearing regions have been classified into two categories and the shearing regions have been registered automatically. Similarly to the table inFIG. 4, in this example, a shearing region in which an acquired AF signal intensity is 50% or more of the maximum signal intensity (Peak) is defined to be the shearing region 1, and a shearing region in which the acquired AF signal intensity is less than 50% of the Peak is defined to be the shearing region 2. Also in this case, in the shearing region 1, 100≦shearing amount<400, and 900≦shearing amount≦1000. In the shearing region 2, 0≦shearing amount<100, and 400≦shearing amount<900.

A shearing amount management table241illustrated inFIG. 6is an example in which, in the shearing amount management table generation procedure, shearing regions have been classified into four categories and the shearing regions have been registered automatically. In this example, a shearing region in which an acquired AF signal intensity is 50% or more of the maximum signal intensity (Peak) is defined to be the shearing region 1, a shearing region in which the acquired AF signal intensity is less than 50% of the Peak and is 30% or more of the Peak is defined to be the shearing region 2, a shearing region in which the acquired AF signal intensity is less than 30% of the Peak and is 10% or more of the Peak is defined to be the shearing region 3, and a shearing region in which the acquired AF signal intensity is less than 10% of the Peak is defined to be the shearing region 4. In this case, in the shearing region 1, 100≦shearing amount<400, and 900≦shearing amount≦1000. In the shearing region 2, 0≦shearing mount<100, 400≦shearing amount<500, and 800≦shearing amount<900. In the shearing region 3, 500≦shearing amount<600, and 700≦shearing amount<800. In the shearing region 4, 600≦shearing amount<700.

Described next is an AF operation that is performed in differential interference observation.

FIG. 7is an example of a flowchart illustrating the AF operation.

This operation is started in response to an AF starting instruction by a user via the PC300after the user adjusts a shearing amount of the DIC prism206so as to be an interference color that is suitable for the differential interference observation. The shearing amount is adjusted while the user repeatedly provides an instruction to drive the DIC prism206via the PC300. Assume that a shearing amount management table241used in this operation is a table illustrated inFIG. 3as an example.

As illustrated inFIG. 7, when this operation is started, the AF control unit220acquires a current shearing amount of the DIC prism206on the basis of an output signal from the shearing amount detection unit216(S110), and stores the current shearing amount, for example, in the storage unit234(S120).

Then, the condition changing unit235acquires a shearing region corresponding to the shearing amount acquired in S110from the shearing amount management table241(S130), and determines whether the shearing region is the shearing region 2 (S140). This determination is for determining whether an AF signal intensity corresponding to the shearing amount acquired in S110is less than 50% of the maximum signal intensity (Peak).

In the determination of S140, when a determination result is Yes, the condition changing unit235acquires a shearing amount corresponding to the shearing region 0 from the shearing amount management table241, and changes the shearing amount of the DIC prism206to the acquired shearing amount (S150). This is performed, specifically, when a driving signal for changing the shearing amount of the DIC prism206to the acquired shearing amount is output to the DIC prism driving unit217via the microscope main control unit221.

After the process of S150is performed or when the determination result in S140is No, the AF control unit220starts the AF (S160). In the AF, the integration times in the integrators231and232are set to be a time that is within a range of a set maximum integration time and at which an S/N ratio is the greatest. Then, the AF control unit220determines whether the AF has been completed (S170), and repeats this determination when the determination result is No.

On the other hand, in a case in which the determination result in S170is Yes, only when the determination result in S140is Yes, the condition changing unit235reads the shearing amount stored in S120, and returns the shearing amount of the DIC prism206to the read shearing amount (S180). This is performed, specifically, when a driving signal for returning the shearing amount of the DIC prism206to the read shearing amount is output to the DIC prism driving unit217via the microscope main control unit221.

Then, this operation is finished.

As described above, in the focusing device in this embodiment, when an AF signal intensity is low due to an influence of the DIC prism206in the AF operation in the differential interference observation, the AF is performed after the shearing amount of the DIC prism206is changed so that an error signal that enables a focusing detection with a high accuracy is acquired, and therefore a focusing detection with a high accuracy is attained. In addition, in the AF operation described above, the DIC prism206is not moved to a position out of an optical path, and therefore the time needed for a focusing detection can be shortened, compared with an AF operation of a conventional focusing device that requires removing a DIC prism from an optical path.

In this embodiment, in S150ofFIG. 7, for example, a shearing amount corresponding to a maximum AF signal intensity may be acquired from the shearing amount management table241, and the shearing amount of the DIC prism206may be changed to the acquired shearing amount. Also when the shearing amount management table241illustrated inFIG. 5orFIG. 6is used for example, instead of the shearing amount management table241illustrated inFIG. 3, a similar acquisition and changing may be performed.

In addition, in this embodiment, when the AF operation illustrated inFIG. 7is performed using the shearing amount management table241illustrated inFIG. 4orFIG. 5, in S150ofFIG. 7, for example, the condition changing unit235may acquire a shearing amount corresponding to the shearing region 1 from the shearing amount management table241, and change the shearing amount of the DIC prism206to the acquired shearing amount. Here, when the shearing amount management table241has a plurality of shearing amounts that correspond to the shearing region 1, any of the shearing amounts may be acquired. Alternatively, a shearing amount that is closest to the current shearing amount may be acquired from among the plurality of shearing amounts.

In addition, in this embodiment, when the AF operation illustrated inFIG. 7is performed using the shearing amount management table241illustrated inFIG. 6, in S140ofFIG. 7, it may be determined for example whether the current shearing amount corresponds to any of the shearing regions 2, 3, and 4. In this case, in S150ofFIG. 7, for example, the condition changing unit235may acquire a shearing amount that corresponds to the shearing region 1 from the shearing amount management table241and change the shearing amount of the DIC prism206to the acquired shearing amount, similarly to the above. Here, when the shearing amount management table241has a plurality of shearing amounts that correspond to the shearing region 1, any of the shearing amounts may be acquired. Alternatively, a shearing amount that is closest to the current shearing amount may be acquired from among the plurality of shearing amounts.

In addition, in this embodiment, for example, the processes of S130and S140may be omitted from the AF operation illustrated inFIG. 7. In this case, the process of S150may be changed, for example, similarly to the above.

Further, in this embodiment, a shearing amount management table241may be generated for each type (e.g., magnification) of an objective lens. In this case, for example, in S110ofFIG. 7, a detection result of an objective lens detection unit not illustrated that detects the type (e.g., magnification) of an objective lens in an optical path may be acquired, and a shearing amount management table241that is used in S130ofFIG. 7may be selected according to the detection result.

In Embodiment 2, the same components as those described in Embodiment 1 are described with the same reference numerals denoted.

FIG. 8illustrates an example of a configuration of a microscope device that includes a focusing device and a differential interference observation mechanism in Embodiment 2 of the present invention.

A microscope100inFIG. 8is different from the microscope device100inFIG. 1in that a DIC prism206is driven manually, not electrically. Specifically, the microscope device100inFIG. 8is different from the microscope device100inFIG. 1in that the microscope device100inFIG. 8includes a DIC prism rotary knob (hereinafter simply referred to as a “rotary knob”)251instead of the DIC prism driving unit217. The rotary knob251is for manually driving (moving) the DIC prism206, and the DIC prism206moves when a user rotates the rotary knob251. InFIG. 8, the other components are similar to those in Embodiment 1, and therefore the descriptions are omitted.

FIG. 9illustrates an example of a configuration of an AF control unit220in this embodiment.

The AF control unit220inFIG. 9is different from the AF control unit220inFIG. 2in that a storage unit234further stores an error signal acquisition condition table252and in the operation of a condition changing unit235. The error signal acquisition condition table252includes information on an error signal acquisition condition that enables a focusing detection with a high accuracy even when an AF signal intensity is low due to an influence of the DIC prism206, and is a table that has been generated on the basis of relevant experimental results or the like. Specifically, the error signal acquisition condition table252is a table that indicates a correspondence relation between a shearing region, change information of maximum integration times in integrators231and232, change information of gains in gain changing units236and237, and change information of an output condition of a laser beam emitted from an AF light source201. The error signal acquisition condition table252is an example of a table that indicates a correspondence relation between a signal intensity range of a signal based on an output signal from a photo detection unit and error signal acquisition condition change information. The condition changing unit235in this embodiment changes any one or more of the maximum integration times in the integrators231and232, the gains in the gain changing units236and237, and the output condition of the laser beam emitted from the AF light source201as an acquisition condition of an error signal on the basis of the shearing amount management table241, the error signal acquisition condition table252, and an output signal from a shearing amount detection unit216, as described below in detail. The output condition of the laser beam is changed, specifically, when a control signal for changing the output condition of the laser beam is output to an AF light source control unit214via the microscope main control unit221. InFIG. 9, the other components are the same as those in Embodiment 1, and the descriptions are omitted.

FIG. 10andFIG. 11illustrate examples of the error signal acquisition condition table252.

The error signal acquisition condition table252inFIG. 10is an example in which shearing regions have been classified into two categories. In this example, the shearing regions 1 and 2 correspond to the shearing regions 1 and 2 of the shearing amount management tables241illustrated inFIG. 4andFIG. 5.

The error signal acquisition condition table252inFIG. 11is an example in which shearing regions have been classified into four categories. In this example, the shearing regions 1, 2, 3, and 4 correspond to the shearing regions 1, 2, 3, and 4 of the shearing amount management table241illustrated inFIG. 6.

In the error signal acquisition condition tables252inFIG. 10andFIG. 11, an “addition value (to maximum integration time)” and a “coefficient (to maximum integration time)” represent change information of maximum integration times in the integrators231and232. A “duty ratio (of laser pulse)” and a “coefficient (to laser output)” represent change information of the output condition of the laser beam emitted from the AF light source201. A “coefficient (to AF signal intensity)” represents change information of gains in the gain changing units236and237. From among these, the “addition value (to maximum integration time)”, the “coefficient (to maximum integration time)”, the “duty ratio (of laser pulse)”, and the “coefficient (to laser output)” contribute to a change in an S/N ratio (an increase in an S/N ratio) of an error signal. In addition, the “coefficient (to AF signal intensity)” contributes to a change in a gain (an increase in a gain) of the error signal.

As illustrated inFIG. 10andFIG. 11, in the error signal acquisition condition table252, change information is set so that the maximum integration times in the integrators231and232become longer, the output of the laser beam emitted from the AF light source201is increased, and the gains in the gain changing units236and237are increased as the signal intensity range of the shearing region becomes lower.

The shearing amount management table241in this embodiment is as described in Embodiment 1, and in this embodiment, the shearing amount management table241is generated essentially in accordance with the shearing amount management table generation procedure described in Embodiment 1. However, in this embodiment, the DIC prism206is driven manually, not electrically, and therefore the DIC prism206is driven manually while the DIC prism206is driven electrically in the shearing amount management table generation procedure described in Embodiment 1. Specifically, with respect to the process (2) in the shearing amount management table generation procedure described in Embodiment 1, in this embodiment, a user rotates the rotary knob251so as to move the DIC prism206to an initial position. With respect to the process (4), in this embodiment, a user rotates the rotary knob251by a specified amount so as to change a shearing mount of the DIC prism206by a specified amount. The other processes are similar to those in Embodiment 1.

Described next is an AF operation in this embodiment that is performed in the differential interference observation.

FIG. 12is an example of a flowchart illustrating the AF operation.

Similarly to Embodiment 1, this operation is started in response to an AF start instruction by a user via the PC300after the user adjusts the shearing amount of the DIC prism206to be an interference color suitable for the differential interference observation. However, the shearing amount is adjusted when the user rotates the rotary knob251. In addition, a shearing amount management table241and an error signal acquisition condition table252used in this operation are, for example, the shearing amount management table241illustrated inFIG. 5and the error signal acquisition condition table252illustrated inFIG. 10, or the shearing amount management table241illustrated inFIG. 6and the error signal acquisition condition table252illustrated inFIG. 11.

As illustrated inFIG. 12, when this operation is started, the AF control unit220acquires the current shearing amount of the DIC prism206on the basis of an output signal from the shearing amount detection unit216(S210).

Then, the condition changing unit235acquires a shearing region corresponding to the shearing amount acquired in S210from the shearing amount management table241(S220), and acquires change information corresponding to the shearing region from the error signal acquisition condition table252(S230).

Then, the condition changing unit235changes an acquisition condition of the error signal using the change information acquired in S230(S240). Specifically, the condition changing unit235changes the acquisition condition of the error signal by any one of the following five changing methods or a combination of two or more of the changing methods.

In the changing method 1, in the integrators231and232, the set maximum integration times are changed to new maximum integration times that are obtained by adding an addition value (to a maximum integration time) acquired from the error signal acquisition condition table252to the maximum integration times.

In the changing method 2, in the integrators231and232, the set maximum integration times are changed to new maximum integration times that are obtained by multiplexing the maximum integration times by a coefficient (to a maximum integration time) acquired from the error signal acquisition condition table252.

In the changing method 3, a duty ratio of a laser beam emitted from the AF light source201is changed to a duty ratio (of a laser pulse) acquired from the error signal acquisition condition table252.

In the changing method 4, an output of the laser beam emitted from the AF light source201is changed in accordance with a coefficient (to a laser output) acquired from the error signal acquisition condition table252.

In the changing method 5, in the gain changing units236and237, the set gains are changed in accordance with a coefficient (to an AF signal intensity) acquired from the error signal acquisition condition table252.

In the changing methods 1 and 2, the maximum integration times in the integrators231and232become longer. In the changing methods 3 and 4, the output of the laser beam emitted from the AF light source201is increased. In the changing method 5, the gains in the gain changing units236and237are increased.

The changing in the changing methods 3 and 4 is performed in response to the output of a control signal for the changing to the AF light source control unit214via the microscope main control unit221.

When the process of S240is finished, the AF control unit220starts the AF (S250). In this AF, the integration times in the integrators231and232are set to a time that is within a range of the set maximum integration time and at which an S/N ratio is the greatest. Then, the AF control unit220determines whether the AF has been completed (S260), and repeats this determination when the determination result is No.

On the other hand, when the determination result in S260is Yes, this operation is finished.

As described above, in the focusing device in this embodiment, in the AF operation in the differential interference observation, the AF is performed after any one or more of the maximum integration times in the integrators231and232, the gains in the gain changing units236and237, and the output condition of the laser beam emitted from the AF light source201are changed on the basis of the shearing amount of the DIC prism206so that an error signal that enables a focusing detection with a high accuracy even when an AF signal intensity is low due to an influence of the DIC prism206is acquired, and therefore a focusing detection with a high accuracy is attained. In the AF operation described above, any one or more of the maximum integration times, the gains, and the output condition of the laser beam may be changed, but the shearing amount of the DIC prism206is not changed. Therefore, the time needed for the focusing detection can be further shortened. Further, the AF operation described above does not require a mechanism that electrically drives the DIC prism206(the DIC prism driving unit217in Embodiment 1), and therefore the AF operation described above can be realized inexpensively.

In this embodiment, the shearing amount management table241may be generated for each type (e.g., magnification) of an objective lens.

In addition, the error signal acquisition condition table252may be a table that includes a correspondence relation with the type of objective lens. Namely, the error signal acquisition condition table252may be a table that indicates a correspondence relation between a shearing region, the type of objective lens, change information of maximum integration times in the integrators231and232, change information of the gains in the gain changing units236and237, and change information of the output condition of the laser beam emitted from the AF light source201.

FIG. 13andFIG. 14illustrate examples of the error signal acquisition condition table252that includes the correspondence relation with the type of objective lens as described above.

The error signal acquisition condition table252illustrated inFIG. 13is an example in which shearing regions have been classified into two categories. In this example, the shearing regions 1 and 2 correspond to the shearing regions 1 and 2 of the shearing amount management tables241illustrated inFIG. 4anFIG. 5. In this example, in the shearing region 1, the change information of the maximum integration times, the change information of the gains, and the change information of the output condition of the laser beam are fixed even when the type (magnification) of an objective lens is changed.

The error signal acquisition condition table252illustrated inFIG. 14is an example in which shearing regions have been classified into four categories. In this example, the shearing regions 1, 2, 3, and 4 correspond to the shearing regions 1, 2, 3, and 4 of the shearing amount management table241illustrated inFIG. 6. Also in this example, in the shearing region 1, the change information of the maximum integration times, the change information of the gains, and the change information of the output condition of the laser beam are fixed even when the type (magnification) of an objective lens is changed.

As described above, when a shearing amount management table241is generated for each type of an objective lens and the error signal acquisition condition table252is a table that further includes a correspondence relation with the type of the objective lens, in S210ofFIG. 12, for example, a detection result of an objective lens detection unit not illustrated that detects the type (e.g., magnification) of the objective lens in an optical path may be acquired, and a shearing amount management table241used in S220ofFIG. 12and an error signal acquisition condition table252used in S230ofFIG. 12may be selected in accordance with the detection result.

In addition, in this embodiment, the DIC prism206may be driven electrically, similarly to Embodiment 1. In this case, also in this embodiment, a shearing amount management table241can be generated in accordance with the shearing amount management table generation procedure described in Embodiment 1.

In Embodiment 3, the same components as those described in Embodiment 2 are described with the same reference numerals denoted.

FIG. 15illustrates an example of a configuration of a microscope device that includes a focusing device and a differential interference observation mechanism in Embodiment 3 of the present invention.

A microscope100inFIG. 15is different from the microscope device100inFIG. 8in that the microscope100inFIG. 15includes a camera261instead of an eyepiece213and does not include a shearing amount detection unit216. The camera261captures a differential interference observation image of an observation sample209, and outputs image information of the differential interference observation image to an AF control unit220and a PC300. The camera261is an example of an imaging unit that captures a differential interference observation image of an observation sample. InFIG. 15, the other components are similar to those in Embodiment 2, and the descriptions are omitted.

FIG. 16illustrates an example of a configuration of an AF control unit220in this embodiment.

The AF control unit220inFIG. 16is different from the AF control unit220inFIG. 9in that image information that is an output signal of the camera261is input instead of an output signal of a shearing amount detection unit216, in that a storage unit234stores a color information management table262instead of a shearing amount management table241, and in an operation of a condition changing unit235. The color information management table262is generated on the basis of an output signal of an arithmetic unit239and an output signal (image information) of the camera261in accordance with a color information management table generation procedure as described below in detail. The color information management table262is an example of a table that indicates a correspondence relation between color information of a differential interference observation image of an observation sample and a signal intensity range of a signal based on an output signal of a photo detection unit. A condition changing unit235in this embodiment changes any one or more of maximum integration times in integrators231and232, gains in gain changing units236and237, an output condition of a laser beam emitted from an AF light source201as an acquisition condition of an error signal on the basis of the color information management table262, the error signal acquisition condition table252, and an output signal (image information) of the camera261, as described below in detail. The output condition of the laser beam is changed, specifically, in response to the output of a control signal for changing the output condition to an AF light source control unit214via a microscope main control unit221. InFIG. 16, the other components are similar to those in Embodiment 2, and the descriptions are omitted.

Described next is the color information management table generation procedure.

Once this procedure has been performed, the procedure does not need to be performed again even when an observation sample is changed later. However, the procedure may be performed every time the observation sample is changed.

The color information management table generation procedure is performed in accordance with the following processes (1)-(6).

(1) A user removes the DIC prism206from an optical path and provides an instruction via the PC300so as to perform the AF to an observation sample209mounted on a stage218and move the stage218to a focusing position. As a result, the position of the stage218is a position at which a greater AF signal intensity can be acquired as an AF signal intensity acquired in the process (4) described below.
(2) Then, after the user returns the DIC prism206to the optical path, the user rotates a rotary knob251and changes the position of the DIC prism206to an initial position. The user performs this, for example, by rotating the rotary knob251in a counterclockwise direction until the rotary knob251stops.
(3) Then, the user provides a color information management table generation instruction via the PC300so as to start an AF signal intensity acquisition operation. When the AF signal intensity acquisition operation is started, a laser beam starts to be emitted from the AF light source201, and in the AF control unit220, a process of acquiring an AF signal intensity from an output signal from the PD208that receives a reflection light from the observation sample209is started.
(4) Then, the user rotates the rotary knob251by a specified amount so as to change the shearing amount of the DIC prism206by a specified amount.
(5) Then, the user provides an instruction via the PC300so as to start the data registration in the color information management table262. In this data registration, a shearing region can be registered manually or automatically. The shearing region is defined by a prescribed signal intensity range similarly to Embodiment 1 and Embodiment 2. For example, a shearing region in which an acquired AF signal intensity is 1000 or more is defined to be the shearing region 1, and a shearing region in which the acquired AF signal intensity is less than 1000 is defined to be the shearing region 2.

In the data registration in which the shearing region is manually registered, color information of a current differential interference observation image (color information of image information that is an output signal from the camera261) is automatically registered, and the user registers the shearing region via the PC300. An AF signal intensity acquired at this point is displayed for example on a monitor400, and the user can register the shearing region on the basis of the AF signal intensity.

In the data registration in which the shearing region is automatically registered, when a specified time (e.g., a specified time after the above process (4) has been performed) has passed, color information of a differential interference observation image acquired at that point (color information of image information that is an output signal of the camera261), an AF signal intensity acquired at that point, and a shearing region to which the AF signal intensity belongs are automatically registered. This data registration is performed when a specified time has passed; however, this data registration may be performed when specified pieces of image information have been acquired from the camera261that captures images at a prescribed frame rate.

The automatic registration described above is performed for example by the AF control unit220.

(6) When the above processes (4) and (5) are repeated and the user rotates the rotary knob251until the rotary knob stops, the generation of the color information management table262is finished automatically. Alternatively, the user provides an instruction via the PC300so as to finish the generation of the color information management table262.

As a result, a color information management table262that has been generated by manually registering shearing regions is a table that indicates a correspondence relation between color information and a shearing region. In addition, a color information management table262that has been generated by automatically registering shearing regions is a table that indicates a correspondence relation between color information, an AF signal intensity, and a shearing region.

FIG. 17illustrates an example of a color information management table262that has been generated in accordance with the color information management table generation procedure.

A color information management table262illustrated inFIG. 17is an example in which, in the shearing amount management table generation procedure, shearing regions have been classified into two categories and the shearing regions have been registered automatically. In this example, color information of an acquired differential interference observation image is represented by each RGB value, and a shearing region in which an acquired AF signal intensity is 1000 or more is the shearing region 1 and a shearing region in which the acquired AF signal intensity is less than 1000 is the shearing region 2.

FIG. 18illustrates an example of an error signal acquisition condition table252.

An error signal acquisition condition table252illustrated inFIG. 18is an example in which shearing regions have been classified into two categories. In this example, the shearing regions 1 and 2 correspond to the shearing regions 1 and 2 of the color information management table262inFIG. 17. Details of the error signal acquisition condition table252are as described in Embodiment 2, and the descriptions are omitted.

Described next is an AF operation in this embodiment that is performed in the differential interference observation.

FIG. 19is an example of a flowchart illustrating the AF operation.

Similarly to Embodiments 1 and 2, this operation is started when a user provides an instruction (an AF start instruction) via the PC300after adjusting a shearing amount of the DIC prism206to an interference color suitable for the differential interference observation. However, the shearing amount is adjusted when the user rotates the rotary knob251. In addition, a color information management table262and an error signal acquisition condition table252used in this operation are, for example, the color information management table262inFIG. 18and the error signal acquisition condition table252inFIG. 17.

As illustrated inFIG. 19, when this operation is started, the AF control unit220acquires color information of a current differential interference observation image on the basis of an output signal of the camera261that captures a differential interference observation image of an observation sample209(S310).

Then, the condition changing unit235acquires a shearing region that corresponds to the color information acquired in S310from the color information management table262(S320). For example, in a case in which the color information is determined to be represented by each RGB value, when each RGB value acquired in S310is included within a specified range centering around each RGB value registered in the color information management table262(e.g., within a range of ±10 of each of the RGB values), a corresponding shearing region is acquired. When there are a plurality of corresponding shearing regions different from each other, any one of the shearing regions may be acquired according to the prescribed priority. For example, when the shearing regions 1 and 2 are acquired from the color information management table262inFIG. 17, the shearing region 2 is acquired preferentially. Alternatively, the shearing region 1 may be acquired preferentially.

When the shearing region is acquired from the color information management table262as described above, the condition changing unit235acquires change information corresponding to the shearing region from the error signal acquisition condition table252(S330).

Then, the condition changing unit235changes an acquisition condition of an error signal using the change information acquired in S330(S340). Specifically, the acquisition condition of the error signal is changed by any one of five changing methods or a combination of two or more of the five changing methods. The five changing methods are as described in Embodiment 2, and the descriptions are omitted.

When the process of S340has been finished, the AF control unit220starts an AF (S350). In this AF, integration times in the integrators231and232are set to be a time that is within a range of a set maximum integration time and at which an S/N ratio is the greatest. Then, the AF control unit220determines whether the AF has been completed (S360), and repeats this determination when the determination result is No.

On the other hand, when the determination result in S360is Yes, this operation is finished.

As described above, in the focusing device in this embodiment, the AF is performed after any one or more of the maximum integration times in the integrators231and232, the gains in the gain changing units236and237, and the output condition of the laser beam emitted from the AF light source201are changed on the basis of color information of a differential interference observation image so as to acquire an error signal that enables a focusing detection with a high accuracy even when an AF signal intensity is low due to an influence of the DIC prism206in the AF operation on the differential interference observation, and therefore the focusing detection with a high accuracy can be attained. In addition, in the AF operation described above, similarly to Embodiment 2, any one or more of the maximum integration times, the gains, and the output condition of the laser beam may be changed, but the shearing amount of the DIC prism206is not changed, and therefore the time needed for the focusing detection can be further shortened. Further, in the AF operation described above, a mechanism that electrically drives the DIC prism206(e.g., the DIC prism driving unit217in Embodiment 1) or a mechanism that detects the shearing amount of the DIC prism.206(e.g., the shearing amount detection units216in Embodiments 1 and 2) is not required, and therefore the AF operation described above can be realized at a lower cost.

In this embodiment, the color information management table262may be generated for each type (e.g., a magnification) of an objective lens.

In addition, the error signal acquisition condition table252may be a table that further includes a correspondence relation with the type of objective lens. Namely, the error signal acquisition condition table252may be a table that indicates a correspondence relation between the shearing region, the type of objective lens, the change information of the maximum integration times in the integrators231and232, the change information of the gains in the gain changing units236and237, and the change information of the output condition of the laser beam emitted from the AF light source201.

FIG. 20illustrates an example of an error signal acquisition condition table252that includes the correspondence relation with the type of objective lens as described above.

An error signal acquisition condition table252inFIG. 20is an example in which shearing regions have been classified into two categories. In this example, the shearing regions 1 and 2 correspond to the shearing regions 1 and 2 of the color information management table262illustrated inFIG. 17. In this example, in the shearing region 1, even when the type (magnification) of an objective lens is changed, the change information of the maximum integration times, the change information of the gains, and the change information of the output condition of the laser beam are fixed.

When the color information management table262is generated for each type of an objective lens and the error signal acquisition condition table252is a table that further includes a correspondence relation with the type of objective lens as described above, for example, in S310ofFIG. 19, a detection result of an objective lens detection unit not illustrated that detects the type (e.g., magnification) of an objective lens in an optical path may be acquired, and a color information management table262that is used in S320ofFIG. 19and an error signal acquisition condition table252that is used in S330ofFIG. 19may be selected according to the detection result.

In addition, in this embodiment, the DIC prism206may be configured to be driven electrically similarly to Embodiment 1. In this case, the DIC prism206that is manually driven in the color information management table generation procedure can be driven electrically. Specifically, in each of the processes (2) and (4) in the color information management table generation procedure, a user may provide an instruction via the PC300so as to electrically drive the DIC prism206that has been driven manually. In addition, in this case, the user may provide a color information management table generation instruction so as to automatically perform the processes (2) to (6).

In addition, in this embodiment, the color information of the differential interference observation image of the observation sample209is not limited to color information in an RGB format, but color information in another format may be used.

Embodiments 1 to 3 have been described above. In each of the embodiments, an upright microscope is used as the microscope body200, but an inverted microscope may be used.

The embodiments described above give specific examples of the present invention in order to easily understand the invention, and the present invention is not limited to the embodiments described above. Various modifications or variations of the present invention can be made without departing from the spirit of the present invention specified in the claims.

As described above, the present invention enables providing a focusing device that enables performing a focusing detection with a high accuracy and shortening the time needed for the focusing detection.