JP2007271978A - microscope - Google Patents

Abstract

A microscope capable of always obtaining appropriate focus error detection characteristics even when an objective lens is switched is provided.
The focus error detection optical systems 20, 20A, 20B are configured by optical units 2, 2A, 2B having optical parameters corresponding to the numerical apertures of the individual objective lenses 11, 11A, 11B, respectively. The control unit 3 selects the optical units 2, 2A, 2B constituting the focus error detection optical systems 20, 20A, 20B corresponding to the objective lenses 11, 11A, 11B being used. Further, the control unit 3 positions the focus of the observation optical system 10 at the in-focus position using the focus error signal obtained by the selected focus error detection optical systems 20, 20A, 20B.
[Selection] Figure 1

Description

  The present invention relates to a microscope having an automatic focusing function of an observation optical system using a focus error signal.

2. Description of the Related Art An automatic focusing device that performs automatic focusing control by driving an objective lens of a microscope with an actuator is known. In this apparatus, a focus error from the focal position of the objective lens of the microscope is detected, and the objective lens is moved and focused by an actuator such as a piezoelectric element in accordance with the detection signal of the deviation (see Patent Document 1). .
JP-A-5-88072

  In such an autofocus device, a detection optical system for obtaining the detection signal includes an objective lens. For this reason, in a microscope using a plurality of objective lenses, when the objective lens is switched, its numerical aperture changes, and an appropriate detection signal cannot be obtained. Further, it cannot cope with a deviation of the optical axis caused by switching of the objective lens. Furthermore, the biological microscope has the special feature of observing the observation object through the cover glass, and a high-precision focus is provided for automatic focusing on the observation object such as cells placed inside the cover glass. An error detection optical system is required. For this reason, there is a situation in which an appropriate focus error detection characteristic must always be maintained regardless of the selected objective lens.

  An object of the present invention is to provide a microscope that can always acquire an appropriate focus error detection characteristic even when the objective lens is switched.

The microscope of the present invention is a microscope that automatically focuses an observation optical system using a focus error signal obtained by a focus error detection optical system, and includes a plurality of objective lenses and an optical system corresponding to the numerical aperture of each of the objective lenses. A plurality of focus error detection optical systems each having a parameter, selection means for selecting the focus error detection optical system corresponding to the objective lens being used, and the focus error detection optical system selected by the selection means Focusing means for positioning the focal point of the observation optical system at the in-focus position using the focus error signal obtained by the above.
According to this microscope, since the focus error detection optical system corresponding to the objective lens being used is selected, the optical parameters of the focus error detection optical system can always be optimized even when the objective lens is switched, and an appropriate focus error can be obtained. Detection characteristics are not lost.

  The focus error detection optical system may have optical parameters such that a focus pull-in width based on the focus error signal when using the corresponding objective lens is a substantially constant value.

  The focus error detection optical system is an optical in which a focus pull-in width by the focus error signal when using the corresponding objective lens becomes a value that can be detected by separating the focus on the front surface and the back surface of the cover glass. Each may have a parameter.

  The focusing means may position the focus of the observation optical system at a focusing position with reference to the back surface of the cover glass.

  According to the microscope of the present invention, since the focus error detection optical system corresponding to the objective lens being used is selected, even if the objective lens is switched, the optical parameters of the focus error detection optical system can always be optimized, Focus error detection characteristics are not lost.

  Hereinafter, an embodiment in which a microscope according to the present invention is applied to a biological microscope will be described with reference to FIGS.

  FIG. 1 is a block diagram showing the configuration of the microscope of the present embodiment.

  As shown in FIG. 1, the microscope of this embodiment includes an optical system 1 including an observation optical system 10 and focus error detection optical systems 20, 20A, 20B, and a control unit 3 for controlling each part of the microscope. And comprising.

  The optical system 1 includes an objective lens 11, an objective lens 11A, and an objective lens 11B disposed in the vicinity of the sample 5, a dichroic mirror 12 that separates light from the sample 5 side into observation light and focus error detection light, and a dichroic mirror. An observation unit 13 that receives observation light transmitted through 12, a laser diode 21 as a light source for focus error detection, a lens group 22 that passes the focus error detection light emitted from the laser diode 21 toward the sample 5, and a focus The half mirror 23 that bends part of the error detection light, the optical unit 2 optimized for the objective lens 11, the optical unit 2A optimized for the objective lens 11A, and the optical unit 2B optimized for the objective lens 11B And comprising.

  The optical unit 2 includes a half mirror 24 that reflects the focus error detection light reflected by the sample 5 and bent by the half mirror 23, a quadrant photodiode 25 that receives the focus error detection light and generates a focus error signal, A collimator lens 26 and a cylindrical lens 27 are provided to shape the beam shape of the focus error detection light incident on the quadrant photodiode 25 into a predetermined shape.

  The optical unit 2A receives the focus error detection light and the half mirror 24A that reflects the focus error detection light reflected by the sample 5 and bent by the half mirror 23 and passes through the half mirror 24, and generates a focus error signal 4 A split photodiode 25A, and a collimator lens 26A and a cylindrical lens 27A that shape the beam shape of the focus error detection light incident on the quadrant photodiode 25 into a predetermined shape are provided.

  The optical unit 2B receives the focus error detection light and the mirror 24B that reflects the focus error detection light reflected by the sample 5 and bent by the half mirror 23 and passed through the half mirrors 24 and 24A, and generates a focus error signal. A quadrant photodiode 25B and a collimator lens 26B and a cylindrical lens 27B that shape the beam shape of the focus error detection light incident on the quadrant photodiode 25 into a predetermined shape are provided.

  As shown in FIG. 1, the objective lens 11, the objective lens 11 </ b> A, and the objective lens 11 </ b> B are selectively used, and the objective lens to be used is selected by the control unit 3. The selected objective lens can be moved in the Z direction (optical axis direction) by the actuator 16. The actuator 16 is controlled by the control unit 3.

  The optical unit 2 is provided in association with the objective lens 11, the optical unit 2A is provided in association with the objective lens 11A, and the optical unit 2B is provided in association with the objective lens 11B. The optical unit 2, the optical unit 2A, and the optical unit 2B are selectively used according to the objective lens used. That is, the optical unit 2 is used when the objective lens 11 is used, the optical unit 2A is used when the objective lens 11A is used, and the optical unit 2B is used when the objective lens 11B is used.

  Next, the operation of the microscope of this embodiment will be described. Here, the objective lens 11 and the optical unit 2 are used.

  Observation light from the sample 5 enters the observation unit 13 via the objective lens 11 and the dichroic mirror 12, and an observation image of the sample 5 is obtained in the observation unit 13. These objective lens 11, dichroic mirror 12 and observation unit 13 constitute an observation optical system 10.

  On the other hand, the focus error detection light emitted from the laser diode 21 passes through the lens group 22 and the half mirror 23, is bent by the dichroic mirror 12, and is irradiated onto the sample 5 through the objective lens 11. The focus error detection light reflected by the sample 5 returns to the dichroic mirror 12 via the objective lens 11 and is bent. Further, the focus error detection light is folded back by the half mirror 23 and the half mirror 24 and passes through the collimator lens 26 and the cylindrical lens 27. The focus error detection light that has passed through the collimator lens 26 and the cylindrical lens 27 is received by the quadrant photodiode 25.

  The lens group 22, the half mirror 23, the dichroic mirror 12, the objective lens 11, the half mirror 24, the four-division photodiode 25, the collimator lens 26, and the cylindrical lens 27 constitute a focus error detection optical system 20.

  The collimator lens 26 and the cylindrical lens 27 have different focal lengths in two directions (x direction and y direction) orthogonal to the optical axis (z axis) and orthogonal to each other, and are based on the amount of light received by the quadrant photodiode 25. It is possible to detect a focus error using the astigmatism method. As will be described later, the focus error detection optical system 20, the control unit 3, and the like function as focusing means.

  FIG. 2 shows the projected shape of the focus error detection light irradiated to the four-divided photodiode 25, FIG. 2 (a) is the shape when focused, FIG. 2 (b) is the shape when the focus is far, FIG. 2C shows the shapes when the focal points are close to each other. When the output level of the region 25a of the photodiode 25 is “A”, the output level of the region 25b is “B”, the output level of the region 25c is “C”, and the output level of the region 25d is “D”, “(A + C)” By calculating “− (B + D)”, a focus error detection signal can be obtained. In the so-called S-curve of the so-called focus error detection signal, a focused state is obtained at a point where the signal intensity is “0”. The focus error detection signal output from the quadrant photodiode 25 is supplied to the control unit 3, and the control unit 3 controls the actuator 16 by feedback control based on the focus error detection signal to drive the objective lens 11. Since focus error detection by the astigmatism method is a well-known technique, detailed description thereof is omitted.

  The focus error detection optical system 20A and the focus error detection optical system 20B are similarly configured by the optical unit 2A when the objective lens 11A is used, and by the optical unit 2B when the objective lens 11B is used, respectively. A similar focus error detection signal is obtained.

  FIG. 3A is a diagram illustrating a focus error detection signal obtained by the focus error detection optical systems 20, 20A, 20B. In the graph shown in FIG. 3A, the vertical axis represents the signal intensity E of the focus error detection signal, and the horizontal axis represents the focus position Z.

  In the example shown in FIG. 3A, the in-focus state is shown at the position indicated by the arrow P and at the position indicated by the arrow Q, respectively. In the figure, the interval (PQ) between the arrow P and the arrow Q corresponds to the thickness of the cover glass 52, and a and b are the pull-in range (focus pull-in width) in the focusing operation, respectively.

  FIG. 4 is a diagram illustrating a state when the observation optical system 10 is in focus.

  FIG. 4A shows a focused state at the arrow P in FIG. In FIG. 4A, the focal point fc of the observation optical system 10 is positioned on the surface 52a of the cover glass 52 placed on the front side of the observation target object 51 such as cells (object lens 11, 11A, 11B side). ing.

  On the other hand, FIG. 4B shows a focused state at the arrow Q in FIG. In FIG. 4B, the focal point fc of the observation optical system 10 is positioned on the back surface 52 b of the cover glass 52. When observing the observation object 51, the focal point fc can be positioned on the observation object 51 by further pushing the objective lenses 11, 11A, and 11B along the Z axis by ΔZ (for example, about 1 to 10 μm).

  As shown in FIG. 3A, according to the microscope of the present embodiment, the focus error is detected so that the curves of the focus error detection signal indicating the focused state on the front surface 52a and the back surface 52b of the cover glass 52 are separated from each other. Optical parameters of the detection optical systems 20, 20A, 20B are determined. Therefore, the observation optical system 10 can be accurately focused on the observation object 51.

  Further, in the microscope of the present embodiment, optical units 2, 2A, 2B having optical parameters corresponding to the objective lenses 11, 11A, 11B are provided, and opticals corresponding to the objective lenses 11, 11A, 11B to be used are provided. Units 2, 2A, 2B (focus error detection optical systems 20, 20A, 20B) are used. For this reason, regardless of which objective lens 11, 11A, 11B is used, a curve of the focus error detection signal as shown in FIG. 3A can always be obtained, and the focusing accuracy is not lowered.

  On the other hand, FIG. 3B illustrates a focus error detection signal when switching to an objective lens with a low numerical aperture when an optical system other than the objective lens is used in common. In the example of FIG. 3B, since the S-shaped curve of the focus error detection signal is broad, the curve indicating the focus on the back surface 52b of the cover glass 52 is a large value indicating the focus on the front surface 52a of the cover glass 52. It is absorbed by the curve of the amplitude, and the focused state on the back surface 52b cannot be detected.

  FIG. 3C illustrates a focus error detection signal when switching to an objective lens having a high numerical aperture when an optical system other than the objective lens is used in common. In the example of FIG. 3C, the focus pull-in width for focus error detection is too narrow to obtain a normal automatic focusing operation.

  In the microscope according to the present embodiment, the optical axes can be independently adjusted in the optical units 2, 2A, and 2B according to the objective lenses 11, 11A, and 11B, respectively. For this reason, the optical axis shift of the focus error detection optical system accompanying the switching of the objective lens can be eliminated, and the work for adjusting the optical axis can be facilitated. Also, by optimizing the lenses of the optical units 2, 2A, 2B according to the objective lens, or by optimizing the gain of the four-division photodiode, it is possible to always obtain an optimum focus error detection signal curve.

  As described above, according to the microscope of the present invention, since the focus error detection optical system corresponding to the objective lens being used is selected, the optical parameters of the focus error detection optical system are always changed even when the objective lens is switched. It is possible to optimize and always obtain an appropriate focus error detection characteristic. In addition, it is possible to adjust an optical axis shift accompanying switching of the objective lens. In addition, according to the microscope of the present invention, it is possible to obtain a biological microscope with high focusing performance.

  The scope of application of the present invention is not limited to the above embodiment. The present invention can be widely applied to a microscope having an automatic focusing function of an observation optical system using a focus error signal.

The block diagram which shows the structure of the microscope of this embodiment. It is a figure which shows the projection shape of the focus error detection light irradiated to a 4-part dividing photodiode, (a) is a shape at the time of focusing, (b) is a shape when a focus is far, (c) is a case where a focus is near The figure which shows the shape of each. It is a figure which illustrates a focus error detection signal, (a) is an example in the microscope of this embodiment, (b) And (c) is a figure which shows the example in the case of using a common optical system, respectively. It is a figure which shows the state at the time of focusing of an observation optical system, (a) is a figure which shows the focusing state to the surface of a cover glass, (b) is a figure which shows the focusing state to the back surface of a cover glass, respectively.

Explanation of symbols

2,2A, 2B optical unit (focus error detection optical system)
3 Control unit (focusing means, selection means)
DESCRIPTION OF SYMBOLS 10 Observation optical system 11, 11A, 11B Objective lens 20, 20A, 20B Focus error detection optical system (focusing means)

Claims (4)

In a microscope that automatically focuses the observation optical system using the focus error signal obtained by the focus error detection optical system,
A plurality of objective lenses;
A plurality of focus error detection optical systems each having an optical parameter corresponding to the numerical aperture of each objective lens;
Selection means for selecting the focus error detection optical system corresponding to the objective lens being used;
Focusing means for positioning the focus of the observation optical system at a focus position using a focus error signal obtained by the focus error detection optical system selected by the selection means;
A microscope comprising: 2. The microscope according to claim 1, wherein each of the focus error detection optical systems has an optical parameter such that a focus pull-in width based on the focus error signal is substantially constant when the corresponding objective lens is used. 3. . The focus error detection optical system is an optical in which a focus pull-in width by the focus error signal when using the corresponding objective lens becomes a value that can be detected by separating the focus on the front surface and the back surface of the cover glass. The microscope according to claim 2, wherein the microscope has parameters. The microscope according to claim 3, wherein the focusing unit positions the focal point of the observation optical system at a focusing position with reference to the back surface of the cover glass.

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