JP4433662B2 - Automatic focusing device and microscope equipped with the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automatic focusing device used for specimen observation or inspection, and a microscope equipped with the same.
[0002]
[Prior art]
Conventionally, an automatic focusing apparatus employing an active method is known. In the active method, the specimen is irradiated with detection light through the objective lens, and reflected light from the specimen irradiated with the detection light is received. Then, focusing is automatically performed based on the shift of the light receiving position of the reflected light. That is, the distance between the specimen and the objective lens is adjusted (for example, vertical movement of the specimen or the objective lens) so that the shift of the light receiving position becomes zero.
[0003]
In this normal AF control, a focus detection signal S1 (see FIG. 13) corresponding to the shift of the light receiving position of the reflected light is generated, and the interval is adjusted so that the focus detection signal S1 becomes zero. During the AF control, the distance between the sample and the objective lens is maintained at the distance A such that the focus detection signal S1 becomes zero.
In addition, when a focus offset is applied during AF control, the DC offset signal ΔV in FIG. 14 is added to the focus detection signal S1 corresponding to the shift in the light receiving position of the reflected light, and the obtained focus after addition is obtained. The interval is adjusted so that the detection signal S2 becomes 0 (DC offset method). As a result, the interval between the specimen and the objective lens is shifted to the interval B where the focus detection signal S2 = 0. The interval B is maintained during this AF control.
[0004]
[Problems to be solved by the invention]
However, in the conventional DC offset method, when the DC offset signal ΔV is outside the range of the maximum value + ΔVmax and the minimum value −ΔVmax shown in FIG. However, it is not possible to find an interval (for example, B) such that the added focus detection signal S2 becomes zero.
[0005]
For this reason, the focus offset range by the conventional DC offset method includes an interval C when the maximum DC offset signal + ΔVmax is added to the focus detection signal S1 and an interval D when the minimum DC offset signal −ΔVmax is added. It will be limited to a narrow range between.
Incidentally, the maximum value + ΔVmax and the minimum value −ΔVmax of the DC offset signal ΔV generally correspond to the amplitude of the waveform of the focus detection signal S2. Further, the amplitude of the waveform of the focus detection signal S2 depends on the type of specimen and the apparatus conditions (magnification of the objective lens, intensity of detection light, sensitivity of an element that receives reflected light, etc.).
[0006]
An object of the present invention is to provide an automatic focusing apparatus capable of setting a wide focus offset range, and a microscope including the same.
[0007]
[Means for Solving the Problems]
The automatic focusing device according to claim 1 is provided for illuminating means for irradiating the specimen with detection light via an objective lens, and for receiving reflected light from the specimen via the objective lens and outputting a light reception signal. A light receiving means for outputting a light receiving signal based on a relative positional relationship between the objective lens and the sample by sequentially scanning from one to the other between the scanning start timing and the scanning end timing, and the output light receiving A sampling timing of a received light signal that is set between an integrator that integrates a signal and a timing from the start of scanning to the end of scanning and that divides the signal integrated by the integrator and is output as a reference timing (Tk); A sample hold circuit that samples the output of the integrator at the reference timing (Tk), and a peak of the received light signal output from the light receiving means are output. Control means for generating a control signal corresponding to a deviation between the output timing (Tp) and the predetermined reference timing (Tk), and adjusting the relative positional relationship based on the control signal; When changing the observation position, input means for inputting an offset amount for a focus offset for changing the relative position between the objective lens and the specimen along the optical axis direction of the objective lens, and the offset amount being input The reference timing (Tk) at the scanning start timing to the scanning end timing for sequentially outputting the light reception signals from the light receiving means is changed, and when the offset amount is inputted, the light receiving means The offset is changed by changing the reference timing (Tk) at the timing from the start of scanning to the end of scanning, which sequentially outputs light reception signals “−ΔZa” is detected, and the offset amount “−ΔZa” is converted into a reference timing (Tk) change amount “+ ΔTa”, or the offset amount “+ ΔZa” is detected and the offset amount “+ ΔZa” is detected. Is converted into the change amount “−ΔTa” of the reference timing (Tk), The sample hold circuit for changing the sample timing of the light reception signal. Said And changing means for changing the reference timing (Tk).
[0008]
According to a second aspect of the present invention, in the automatic focusing apparatus according to the first aspect, the changing unit includes: Depending on the type of objective lens positioned on the optical axis The objective lens used for observation If the magnification of is lower than the objective lens used earlier, One change amount when changing the reference timing (Tk) Than the objective lens used earlier It is characterized by being enlarged.
The invention described in claim 3 has an objective lens and has an imaging optical system for forming an image of a specimen, and the autofocus according to claim 1 or 2 arranged on the optical axis of the objective lens. And an aligning device.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiments of the present invention correspond to claims 1 to 3.
As shown in FIG. 1, the microscope 10 according to this embodiment includes a stage 12 on which a specimen 11 (for example, a semiconductor wafer) to be observed is placed, an epi-illumination illumination optical system (13 to 15), and an observation optical system ( 16-19) and an active automatic focusing device (21-30, 40).
[0010]
Here, the configuration of the microscope 10 will be specifically described in the order of the observation optical system (16 to 19), the illumination optical system (13 to 15), the stage 12, and the automatic focusing device (21 to 30, 40).
The observation optical system (16 to 19) is an optical system for observing a magnified image of the specimen 11, and infinitely, in order from the specimen 11 side along the optical axis 10a, a second objective lens. The imaging lens 17 functioning as a prism, a prism 18 and an eyepiece lens 19 are arranged. This observation optical system (16 to 19) corresponds to the “imaging optical system” in the claims.
[0011]
Although only one objective lens 16 is shown in FIG. 1, the microscope 10 of this embodiment can be observed by a plurality of objective lenses 16 having different magnifications. The plurality of objective lenses 16 are attached to an electric revolver (not shown), and are sequentially positioned on the optical axis 10a by rotating the electric revolver.
The afocal system between the objective lens 16 and the imaging lens 17 on the optical axis 10a of the observation optical system (16 to 19) includes a half mirror 15 of the illumination optical system (13 to 15) and an automatic focus. The dichroic mirror 25 of the aligning device (21-30, 40) is arranged. The dichroic mirror 25 transmits visible light and reflects AF light such as infrared light.
[0012]
The illumination optical system (13-15) is an optical system for epi-illuminating the specimen 11 from above using the objective lens 16, and is for observation arranged along the optical axis 10b perpendicular to the optical axis 10a. The light source 13, the condenser lens 14, and the half mirror 15 are configured. The light source 13 is a visible light source.
When observing the specimen 11, the visible light from the light source 13 is guided onto the optical axis 10 a of the observation optical system (16 to 19) via the condenser lens 14 and the half mirror 15. Then, after passing through the objective lens 16, the specimen 11 is irradiated.
[0013]
Further, the visible light reflected by the specimen 11 is condensed on the imaging surface 19 a via the objective lens 16, the half mirror 15, the dichroic mirror 25, the imaging lens 17, the prism 18, and the eyepiece lens 19. At this time, an enlarged image of the specimen 11 is formed on the imaging surface 19a.
The stage 12 on which the specimen 11 is placed is movable together with the specimen 11 along the optical axis 10a of the observation optical system (16-19) and along a direction perpendicular to the optical axis 10a. A motor 12a (not shown in FIG. 1, refer to FIG. 3) for driving the stage 12 in the direction of the optical axis 10a is connected to the control device 30 of the automatic focusing device (21-30, 40).
[0014]
The microscope 10 according to the present embodiment moves the stage 12 in the direction of the optical axis 10 a, so that the distance from the fixed objective lens 16 to the specimen 11, that is, the relative positional relationship between the objective lens 16 and the specimen 11. To adjust the focus automatically. In the following description, the positions of the stage 12 and the specimen 11 in the optical axis 10a direction are referred to as “Z positions”.
[0015]
Now, the automatic focusing devices (21 to 30, 40) are devices for automatically aligning, for example, the surface of the specimen 11 with the focal point of the objective lens 16. The “focal point of the objective lens 16” here is a focal point by visible light for specimen observation. For this reason, the magnified image of the specimen 11 can be satisfactorily observed through the eyepiece 19 after focusing by the automatic focusing device (21 to 30, 40). In the automatic focusing device (21 to 30, 40), it is possible to apply a focus offset during AF control.
[0016]
This automatic focusing device (21-30, 40) includes an AF light source 21, a slit plate 22, a condensing lens 23, a light shielding plate 24, a dichroic mirror arranged along an optical axis 10c perpendicular to the optical axis 10a. 25, a half mirror 26, a condensing lens 27, a cylindrical lens 28, a light receiving element (CCD) 29, a control device 30 and an input device 40 arranged along an optical axis 10d perpendicular to the optical axis 10c. Is done.
[0017]
The illumination systems (21 to 25) of the automatic focusing devices (21 to 30, 40) use the objective lens 16 to illuminate the specimen 11 by epi-illumination. The light source 21 emits autofocus light (AF light such as infrared light) having a wavelength different from that of the observation light source 13. The half mirror 26 is also disposed between the light shielding plate 24 and the dichroic mirror 25 on the optical axis 10c.
[0018]
In this automatic focusing device (21-30, 40), AF light from the light source 21 passes through the slit plate 22 and the condenser lens 23, and then is half of the pupil (in FIG. The lower half of the border is shielded from light. The AF light that has become the upper half is guided onto the optical axis 10 a via the half mirror 26 and the dichroic mirror 25.
[0019]
The AF light guided onto the optical axis 10a travels in the right half region with the optical axis 10a as a boundary, passes through the half mirror 15 and the objective lens 16, and is then irradiated onto the specimen 11 (AF light L1). At this time, a slit image by the AF light L <b> 1 is projected on the surface of the specimen 11. The AF light L1 corresponds to “detection light” in the claims. The illumination system (21 to 25) corresponds to “illuminating means” in the claims.
[0020]
The slit-shaped AF light L2 reflected from the surface of the specimen 11 travels in the left half region with the optical axis 10a as a boundary, and enters the half mirror 26 via the objective lens 16, the half mirror 15, and the dichroic mirror 25. To do. Further, the slit-shaped AF light reflected by the half mirror 26 forms an image on the light receiving surface of the light receiving element 29 via the condenser lens 27 and the cylindrical lens 28. At this time, a slit image is projected on the light receiving surface of the light receiving element 29.
[0021]
The light receiving element 29 has a plurality of pixels (not shown) arranged in a one-dimensional direction, and accumulates electric charge in each pixel according to a slit image on the light receiving surface. Then, the charge of each pixel is output to the control device 30 as a light reception signal. The light receiving system (26-29) of the automatic focusing device (21-30, 40) is configured to receive the AF light L2 from the specimen 11 using the objective lens 16, and the "light receiving means" in the claims. Corresponding to The AF light L2 corresponds to “reflected light” in the claims.
[0022]
In the illumination system (21 to 25) and the light receiving system (26 to 29) having the above-described configuration, the half of the pupil is shielded by the light shielding plate 24. Therefore, depending on the Z position of the surface of the specimen 11 (the surface on which the AF light L1 reflects). The position of the slit image formed on the light receiving surface of the light receiving element 29 changes in the W direction. The W direction is a direction perpendicular to the optical axis 10 d and corresponds to the arrangement direction of each pixel on the light receiving surface of the light receiving element 29. In the following description, the position of the slit image in the W direction is referred to as “W position”.
[0023]
For example, when the Z position of the specimen 11 moves upward (front pin side), the W position of the slit image on the light receiving surface of the light receiving element 29 moves to the left. Conversely, when the Z position of the specimen 11 moves downward (rear pin side), the W position of the slit image moves to the right.
In the light receiving element 29 according to the present embodiment, a plurality of pixels are scanned sequentially from left to right along the W direction. For this reason, when the Z position of the specimen 11 moves upward (front pin side) and the W position of the slit image moves to the left, the timing Tp at which the light receiving signal is output from the light receiving element 29 is advanced. “Become faster” means that the timing Tp approaches the scanning start timing of the light receiving element 29.
[0024]
Conversely, when the Z position of the specimen 11 moves downward (rear pin side) and the W position of the slit image moves to the right, the light reception signal output timing Tp is delayed. “Delay” means that the timing Tp approaches the scanning end timing of the light receiving element 29.
As described above, the output timing Tp of the light receiving signal from the light receiving element 29 becomes faster or slower according to the W position of the slit image on the light receiving surface of the light receiving element 29, that is, according to the Z position of the sample 11. To do. In other words, the light reception signal is a signal output from the light receiving element 29 to the control device 30 at the timing Tp corresponding to the Z position of the sample 11.
[0025]
The waveform of the light reception signal has a shape having one peak as shown in FIGS. 2A to 2E, the horizontal axis represents the time T from the start of scanning of the light receiving element 29 to the end of scanning, and the vertical axis represents the voltage value V of the light receiving signal (light intensity of the slit image). . The time T on the horizontal axis corresponds to the pixel number of the light receiving element 29.
Each of FIGS. 2A to 2E is a waveform example of a received light signal when the Z position of the specimen 11 is different (Z1 to Z5). As described above, a state in which the output timing Tp of the light reception signal changes according to the Z position of the sample 11 is shown. The description of “division boundary line (reference timing Tk)” in FIGS. 2A to 2E will be described later.
[0026]
Next, the control device 30 that is the output destination of the received light signal will be described. As shown in FIG. 3, the control device 30 includes an amplifier 31, an integrator 32, sample and hold circuits 33 and 34, subtractors 35 and 36, a CPU 37, a memory 38, and a driver 39. Yes. Among these, the amplifier 31 is connected to a light receiving element (CCD) 29, and the driver 39 is connected to the motor 12 a for the stage 12.
[0027]
A light reception signal (for example, any one of FIGS. 2A to 2E) from the light receiving element 29 is sequentially amplified by the amplifier 31 and integrated by the integrator 32 after the scanning start timing. The integration process in the integrator 32 corresponds to the addition process of the voltage value V of the received light signal. For this reason, the output of the integrator 32 (integrated voltage value Vs) gradually increases between the start of scanning of the light receiving element 29 and the end of scanning, as shown in FIG. The horizontal axis of FIG. 4 represents time T, and the vertical axis represents the integrated voltage value Vs.
[0028]
Then, in the sample hold circuit 33 arranged at the subsequent stage of the integrator 32, the output of the integrator 32 (integrated voltage of FIG. 4) is set at a predetermined dividing boundary line (referred to as “reference timing Tk” in this specification as appropriate). Sample the value Vs = L).
The integrated voltage value L at the reference timing Tk corresponds to the area of the hatched portion in FIGS. 2A to 2E, that is, the area of the left region from the start of scanning of the light receiving element 29 to the dividing boundary line (Tk). When the output timing Tp of the received light signal changes according to the Z position (Z1 to Z5) of the specimen 11, the magnitude thereof changes.
[0029]
When the sample hold circuit 33 samples the output of the integrator 32 (integrated voltage value Vs = L) at the reference timing Tk, the sample hold circuit 33 outputs this to the subtractors 35 and 36 as an integration signal (L).
Further, the sample hold circuit 34 samples the output of the integrator 32 (integrated voltage value Vs = L + R in FIG. 4) at the scanning end timing of the received light signal 29, and uses this as an integrated signal (L + R) as one subtractor 35. Output to. Since the integrated voltage value L + R corresponds to the entire area of each received light signal shown in FIGS. 2A to 2E, the magnitude thereof is substantially constant regardless of the Z position (Z1 to Z5) of the sample 11. is there.
[0030]
Note that the sample timing (reference timing Tk) of the sample hold circuit 33 described above is set by the CPU 37. The CPU 37 refers to the stored information in the memory 38 when setting the reference timing Tk. During normal AF control, the reference timing Tk is set according to the stored information in the memory 38. At the time of focus offset during AF control (described later), the reference timing Tk is set and changed at a timing different from the information stored in the memory 38.
[0031]
Then, the integration signals (L) and (L + R) respectively output from the sample hold circuits 33 and 34 are subjected to a subtraction process of “integrated voltage value L + R” − “integrated voltage value L” in the next subtractor 35. Is done. The subtractor 35 generates a new integrated signal (R) based on the integrated voltage value R obtained by the subtraction process, and outputs this to the subsequent subtractor 36.
[0032]
The integrated voltage value R corresponds to the area of the right region from the dividing boundary line (Tk) to the end of scanning in each of the received light signals shown in FIGS. When the output timing Tp of the received light signal changes according to Z1 to Z5), the magnitude thereof changes.
The subtracter 36 at the subsequent stage inputs the integration signal (R) from the subtractor 35 and the integration signal (L) from the sample hold circuit 33, and subtracts “integrated voltage value R” − “integrated voltage value L”. Processing is performed to calculate the difference R−L of the integrated voltage value. This difference RL corresponds to the area difference between the region on the left side (hatched portion) and the region on the right side of the division boundary line (Tk) in each of the received light signals shown in FIGS.
[0033]
The subtractor 36 generates a focus detection signal (R−L) based on the difference R−L of the integrated voltage value, and outputs it to the CPU 37. The focus detection signal (RL) corresponds to a “control signal” in the claims.
Here, when the output timing Tp of the received light signal changes according to the Z position (Z1 to Z5 in FIG. 2) of the specimen 11, the focus detection signal (RL) is output from the output timing Tp and the reference timing Tk (divided boundary line). ) And the sign change in accordance with the deviation from (). The state of change of the focus detection signal (RL) is as shown in FIG. The horizontal axis in FIG. 5 represents the Z position of the sample 11.
[0034]
For example, as shown in FIGS. 2A and 2B, when the output timing Tp of the received light signal is earlier than the reference timing Tk, the sign of the focus detection signal (RL) becomes “negative”. On the other hand, when the output timing Tp is later than the reference timing Tk (FIGS. 2D and 2E), the sign of the focus detection signal (RL) becomes “positive”. When the output timing Tp coincides with the reference timing Tk (FIG. 2C), the focus detection signal (RL) becomes “0”.
[0035]
As will be described in detail later, the CPU 37, which is the output destination of the focus detection signal (RL), controls the driver 39 based on the magnitude and sign of the focus detection signal (RL) and turns on the motor 12a for the stage 12. By rotating, the Z position of the specimen 11 is automatically adjusted (AF control). As a result, the Z position of the sample 11 is maintained at a position (Z3 in FIG. 5) at which the focus detection signal (RL) is “0”.
[0036]
Next, the input device 40 will be described. As shown in FIG. 3, the input device 40 includes an offset input unit 41, an address sensor 42, and a switch 43, and each is connected to the CPU 37 of the control device 30.
[0037]
The offset input unit 41 is a volume knob for inputting an offset amount of the Z position of the sample 11 in accordance with a manual operation from the outside at the time of focus offset during AF control. A plurality of button switches and a jog dial can be used instead of the volume knob. The offset input unit 41 corresponds to “input means” in the claims.
[0038]
When the offset input unit 41 is a volume knob, the CPU 37 detects the offset amount by A / D converting the voltage value input by the volume knob. In the case of a button switch, the offset amount is detected based on the number of times the button switch is pressed.
Then, based on the offset amount from the offset input unit 41, the CPU 37 changes the sample timing (reference timing Tk, division boundary line) of the sample hold circuit 33 at a timing different from the information stored in the memory 38. This change is performed with the scanning cycle (clock cycle) of the light receiving element 29 as a minimum unit. The CPU 37 corresponds to “change means” in the claims.
[0039]
Further, the address sensor 42 of the input device 40 includes an objective lens 16 positioned on the optical axis 10a of the observation optical system (16 to 19) among the plurality of objective lenses 16 mounted on the electric revolver of the microscope 10. It is a sensor that detects the type. The type of the objective lens 16 is a magnification or a depth of focus.
The switch 43 is a switch for setting the microscope 10 to the AF control mode, and outputs a command signal according to a manual operation. When receiving a command signal from the switch 43, the CPU 37 sets the microscope 10 to the AF control mode. That is, AF control is executed according to a flowchart (FIG. 6) described below.
[0040]
Finally, the focusing operation in the microscope 10 having the above configuration will be described with reference to the flowchart of FIG.
When the CPU 37 receives the command signal from the switch 43, the CPU 37 refers to the stored information in the memory 38, and sets the sample timing (reference timing Tk, division boundary line) of the sample hold circuit 33 according to the stored information (step). S1). Thereby, the focus detection signal (RL) shown in FIG. 5 corresponding to the reference timing Tk is output from the subtractor 36.
[0041]
Next, the CPU 37 determines whether or not the “offset amount at the Z position of the specimen 11” is input from the offset input unit 41 (step S2). If there is no offset input (S2 is N), the subtractor Based on the focus detection signal (RL) of FIG. 5 output from 36, the processing of steps S3 to S7 is executed.
That is, first, it is determined whether or not the focus detection signal (RL) is “0” (step S3). If it is not “0” (S3 is N), the focus detection signal (R−) is determined. It is determined whether or not the sign of L) is “positive” (step S4).
[0042]
When the sign of the focus detection signal (RL) is “positive” (S4 is Y), the output timing Tp of the received light signal is the reference timing Tk as shown in FIGS. Slower, the W position of the slit image on the light receiving surface of the light receiving element 29 is shifted to the right, and the Z position of the sample 11 is shifted downward (rear pin side), so the CPU 37 uses the driver 39 and the motor 12a. Then, the Z position of the stage 12 and the specimen 11 is moved upward (front pin side) (step S5).
[0043]
Thereafter, the process returns to step S3, and the processes of steps S3 to S5 are repeated until the focus detection signal (RL) becomes “0”. During this time, as the Z position of the specimen 11 moves upward, the magnitude of the focus detection signal (RL) becomes smaller (AF 1 in FIG. 5). When the focus detection signal (RL) becomes “0” (Y in S3), the output timing Tp of the received light signal coincides with the reference timing Tk as shown in FIG. 11 is stopped (step S7). At this time, the Z position of the sample 11 is stopped at a position (Z3 in FIG. 5) at which the focus detection signal (RL) becomes “0”.
[0044]
On the other hand, when the sign of the focus detection signal (R−L) is “negative” (S4 is N) in step S4, the light reception signal is output as shown in FIGS. Since the timing Tp is earlier than the reference timing Tk, the W position of the slit image on the light receiving surface of the light receiving element 29 is shifted leftward, and the Z position of the sample 11 is shifted upward (front pin side). The Z position of the specimen 11 is moved downward (rear pin side) (step S6).
[0045]
Thereafter, the process returns to step S3, and the processes of steps S3, S4, and S6 are repeated until the focus detection signal (RL) becomes “0”. During this time, as the Z position of the sample 11 moves downward, the magnitude of the focus detection signal (RL) becomes smaller (AF 2 in FIG. 5). When the focus detection signal (RL) becomes “0” (S3 is Y), the output timing Tp of the received light signal coincides with the reference timing Tk (FIG. 2 (c)). Stop (step S7). Also at this time, the Z position of the sample 11 is stopped at a position (Z3 in FIG. 5) at which the focus detection signal (RL) becomes “0”.
[0046]
Thus, the Z position of the specimen 11 is determined as the focus detection signal (AF (1) in FIG. 5) or by repeating steps S3, S4, and S6 (AF (2)). When stopping at the position Z3 of (RL) = 0 (FIG. 2 (c)), the CPU 37 returns to the process of step S2.
Therefore, as long as there is no input of the offset amount from the offset input unit 41 (N in S2), the processing of steps S3 to S7 (normal AF control) is repeated, and the Z position of the specimen 11 is detected by the focus detection shown in FIG. The signal (RL) = 0 is kept stopped at the position Z3. In this stable state, an enlarged image of, for example, an arbitrary surface 11 a (see FIG. 7A) of the specimen 11 can be favorably observed through the eyepiece lens 19.
[0047]
Incidentally, while the Z position of the specimen 11 continues to be stopped at the position (Z3) where the focus detection signal (RL) = 0 shown in FIG. 5, the light reception signal from the light receiving element 29 is stored information in the memory 38. As described above, output is continued at the same timing as the reference timing Tk set in step S1 (Tp = Tk, FIG. 2C). In the following description, the stop position (Z3) of the specimen 11 by the normal AF control (S3 to S7) is referred to as “focus position”.
[0048]
Next, a case where the focus offset is applied while the sample 11 is stopped at the in-focus position (Z3) will be described. This corresponds to the case where the offset amount at the Z position of the sample 11 is input from the offset input unit 41 (S2 is Y), and the CPU 37 executes the processes in steps S8 and S9, and then the processes in and after step S3. Execute the process.
[0049]
That is, in step S8, the offset amount at the Z position of the sample 11 is detected based on the input signal (the voltage value and the number of times described above) from the offset input unit 41. In the next step S9, the sample timing (reference timing Tk) of the sample hold circuit 33 is set and changed based on the detected offset amount. As a result, the reference timing Tk is set to a timing different from the stored information in the memory 38.
[0050]
For example, when the Z position of the sample 11 is offset by ΔZa below the current in-focus position (Z3) (FIG. 7A), the CPU 37 sets the offset amount “− based on the input signal from the offset input unit 41. ΔZa ”is detected (S8), and this is converted into a change amount“ + ΔTa ”of the reference timing Tk.
Based on the conversion result, the setting of the reference timing Tk is changed (S9). As a result, the sample timing of the sample hold circuit 33 is changed from the reference timing Tk in FIG. 8A to the reference timing Tk + ΔTa in FIG. 8B, and is output from the subtractor 36 according to the new reference timing Tk + ΔTa. The focus detection signal (RL) is not “0”. Therefore, when the process proceeds to step S3 after the process in step S9, the determination result is “N”.
[0051]
In this example, the setting is changed to the reference timing Tk + ΔTa that is later than the reference timing Tk (FIG. 8B), and the sign of the focus detection signal (RL) becomes “negative” (S4 is N). The CPU 37 moves the Z position of the specimen 11 downward (S6). The processes in steps S3, S4, and S6 are repeated until the focus detection signal (RL) becomes “0”.
[0052]
The state of change of the focus detection signal (RL) during this period is as shown by AF (3) in FIG. The horizontal axis of FIG. 7B represents the Z position of the sample 11. As described above, the magnitude of the focus detection signal (RL) decreases as the Z position of the sample 11 moves downward (AF 3). The broken line in FIG. 7B corresponds to the focus detection signal (RL) in FIG.
[0053]
When the focus detection signal (RL) corresponding to the reference timing Tk + ΔTa becomes “0” (S3 is Y), the light reception signal output timing Tp coincides with the reference timing Tk + ΔTa as shown in FIG. 8C. Therefore, the CPU 37 stops the stage 12 and the specimen 11 (S7). At this time, the Z position of the sample 11 is stopped at a position where the focus detection signal (RL) corresponding to the reference timing Tk + ΔTa is “0” (Z3−ΔZa in FIG. 7A).
[0054]
Therefore, unless a new offset amount is input from the offset input unit 41 (N in S2), the processing of steps S3 to S7 is repeated by the CPU 37, and the Z position of the specimen 11 is set to the focus detection signal (RL) = 0. The position (Z3-ΔZa in FIG. 7A) continues to be stopped. In this stable state, an enlarged image of an arbitrary surface 11b of the specimen 11 can be observed favorably through the eyepiece lens 19.
[0055]
Incidentally, while the Z position of the specimen 11 continues to be stopped at the position (Z3−ΔZa) of the focus detection signal (RL) = 0 shown in FIG. 7B, the light reception signal from the light receiving element 29 is stepped. The output continues at the same timing as the reference timing Tk + ΔTa changed in setting in S9 (Tp = Tk + ΔTa, FIG. 8C).
Contrary to the above example, when the Z position of the specimen 11 is offset by ΔZb above the in-focus position (Z3) (FIG. 9A), the CPU 37 is based on the input signal from the offset input unit 41. Then, the offset amount “+ ΔZb” is detected (S8) and converted into the change amount “−ΔTb” of the reference timing Tk.
[0056]
Based on the conversion result, the setting of the reference timing Tk is changed (S9). As a result, the sample timing of the sample hold circuit 33 is changed from the reference timing Tk in FIG. 10A to the reference timing Tk−ΔTb in FIG. 10B, and the subtractor is changed according to the new reference timing Tk−ΔTb. The focus detection signal (RL) output from 36 is not “0”. Therefore, when the process proceeds to step S3 after the process in step S9, the determination result is “N”.
[0057]
In this example, the setting is changed to the reference timing Tk−ΔTb that is earlier than the reference timing Tk (FIG. 10A), and the sign of the focus detection signal (RL) becomes “positive” (S4 is N Therefore, the CPU 37 moves the Z position of the specimen 11 upward (S5). The processes in steps S3 to S5 are repeated until the focus detection signal (RL) becomes “0”.
[0058]
The state of change of the focus detection signal (RL) during this period is as shown by AF (4) in FIG. 9B. The horizontal axis of FIG. 9B represents the Z position of the sample 11. Similarly to the above, as the Z position of the specimen 11 moves upward, the magnitude of the focus detection signal (RL) becomes smaller (AF (4)). The dashed line in FIG. 9B corresponds to the focus detection signal (RL) in FIG.
[0059]
When the focus detection signal (RL) corresponding to the reference timing Tk−ΔTb becomes “0” (Y in S3), the output timing Tp of the received light signal becomes the reference timing Tk− as shown in FIG. Since it coincides with ΔTa, the CPU 37 stops the stage 12 and the specimen 11 (S7). At this time, the Z position of the sample 11 is stopped at a position where the focus detection signal (RL) corresponding to the reference timing Tk−ΔTb becomes “0” (Z3 + ΔZb in FIG. 9A).
[0060]
Therefore, unless a new offset amount is input from the offset input unit 41 (N in S2), the processing of steps S3 to S7 is repeated by the CPU 37, and the Z position of the specimen 11 is set to the focus detection signal (RL) = 0. The position (Z3 + ΔZb in FIG. 9A) continues to be stopped. In this stable state, an enlarged image of an arbitrary surface 11 c of the specimen 11 can be observed favorably through the eyepiece lens 19.
[0061]
Incidentally, while the Z position of the sample 11 continues to be stopped at the focus detection signal (RL) = 0 position (Z3 + ΔZb) shown in FIG. 9B, the light reception signal from the light receiving element 29 is received in step S9. It continues to be output at the same timing as the changed reference timing Tk-ΔTb (Tp = Tk−ΔTb, FIG. 10C).
As described above, in the microscope 10 of the present embodiment, when the focus offset is applied during the AF control mode, the sample according to the offset amount of the specimen 11 at the Z position (for example, −ΔZa in FIG. 7 or + ΔZb in FIG. 9). The setting of the reference timing Tk (divided boundary line of the received light signal) in the hold circuit 33 is changed.
[0062]
Then, based on the new reference timing after the change (for example, Tk + ΔTa in FIG. 8 or Tk−ΔTb in FIG. 10), the focus detection signal (R−L) output from the subtractor 36 becomes “0”. Then, the Z position of the stage 12 and the specimen 11 is adjusted (for example, AF (3) in FIG. 7B or AF (4) in FIG. 9B), and a new focus detection signal (RL) = 0. It is stopped at a position (for example, Z3−ΔZa in FIG. 7 or Z3 + ΔZb in FIG. 9).
[0063]
For this reason, not only the surface 11a (FIGS. 7A and 9A) of the specimen 11 stopped at the in-focus position (Z3) by the normal AF control (S3 to S7), but also the movement by the focus offset (FIG. Similarly, the magnified images of the different surfaces 11b and 11c of the specimen 11 stopped after AF (3) in FIG. 7 (b) and AF (4) in FIG. 9 (b) can be observed well.
Furthermore, in the microscope 10 of the present embodiment, the reference timing (Tk + ΔTa, Tk−ΔTb) after the change according to the offset amount (−ΔZa, + ΔZb) of the specimen 11 is equal to or higher than the timing Tmin shown in FIG. The focus offset during the AF control mode can be freely applied within a wide range that is equal to or less than the timing Tmax shown in FIG. This range (Tmin or more and Tmax or less) corresponds to a range in which a light reception signal from the light receiving element 29 is output without being lost.
[0064]
When the changed reference timing (Tk + ΔTa, Tk−ΔTb) is set to the earliest timing Tmin (FIG. 11A), the focus detection signal (RL) corresponding to the reference timing Tmin is “0”. The Z position of the sample 11 is adjusted upward so as to be “”, and the state of the focus detection signal (RL) during this time is as shown in AF (5) in FIG.
[0065]
When the focus detection signal (RL) corresponding to the reference timing Tmin becomes “0” (Tmin = Tp), the sample 11 stops at a position Z3 + ΔZmax corresponding to the reference timing Tmin. This position Z3 + ΔZmax corresponds to the upper limit of the focus offset range by the microscope 10 of the present embodiment.
Conversely, when the changed reference timing (Tk + ΔTa, Tk−ΔTb) is set to the latest timing Tmax (FIG. 11B), the focus detection signal (RL) corresponding to the reference timing Tmax is “ The Z position of the sample 11 is adjusted downward so that it becomes 0 ", and the state of the focus detection signal (RL) during this time is as shown in AF (6) in FIG.
[0066]
When the focus detection signal (RL) corresponding to the reference timing Tmax becomes “0” (Tmax = Tp), the sample 11 stops at a position Z3−ΔZmin corresponding to the reference timing Tmax. This position Z3-ΔZmin corresponds to the lower limit of the focus offset range by the microscope 10 of this embodiment.
As described above, according to the microscope 10 of the present embodiment, the light receiving signal from the light receiving element 29 is output without loss (Tmin ≦ reference timing ≦ Tmax in FIG. 11), that is, the Z position of the sample 11. Is included between “the lower limit position Z3−ΔZmin corresponding to the reference timing Tmax” and “the upper limit position Z3 + ΔZmax corresponding to the reference timing Tmin”, the focus offset during the AF control mode can be freely applied.
[0067]
The focus offset range at the Z position of the specimen 11 by the microscope 10 of the present embodiment corresponds to the range between the lower limit position Z3−ΔZmin and the upper limit position Z3 + ΔZmax, and is compared with the conventional focus offset range as shown in FIG. And you can see that it is wide.
Therefore, as in the case where the sample 11 is a semiconductor wafer, for example, the height difference of the plurality of step portions formed on the sample 11 is larger than the focal depth of the objective lens, and the height difference of the step portion itself is the conventional DC. Even when it is larger than the focus offset range by the offset method, the microscope 10 of this embodiment can be observed well.
[0068]
Furthermore, in the microscope 10 of the present embodiment, the setting of the reference timing Tk (division boundary line) is changed with the scanning cycle (clock cycle) of the light receiving element 29 as the minimum unit, that is, for each pixel unit of the light receiving element 29. Therefore, the offset can be applied with a constant resolution regardless of the level difference of the received light signal due to the difference in magnification of the objective lens 16.
[0069]
In the above-described embodiment, on the assumption that the offset amount of the sample 11 (for example, −ΔZa in FIG. 7 or + ΔZb in FIG. 9) is known, the reference timing Tk (the division boundary of the received light signal) is determined according to the offset amount. Line) is changed at once, but the offset amount of the specimen 11 is often unknown in an actual observation situation.
For this reason, every time when the observer of the microscope 10 manually operates the offset input unit 41, the reference timing Tk may be set and changed by a predetermined amount, and the Z position of the specimen 11 may be moved by a predetermined amount. In this case, the specimen 11 can be offset by a desired amount according to the number of manual operations of the offset input unit 41.
[0070]
Furthermore, it is preferable to set the amount of one change of the reference timing Tk to a different value depending on the type (magnification and depth of focus) of the objective lens 16 positioned on the optical axis 10a. For example, since the depth of focus becomes deeper as the objective lens 16 has a lower magnification, it is conceivable that the amount of one change of the Z position of the sample 11 is increased by setting the amount of change of the reference timing Tk once. In this case, an efficient focus offset can be applied regardless of the magnification change of the objective lens 16. The type of the objective lens 16 may be recognized based on the detection result of the address sensor 42.
[0071]
Further, the storage information in the memory 38 for initially setting the reference timing Tk (division boundary line) in step S1 of FIG. 6 may be prepared for each type of the objective lens 16. In this case, in step S1, based on the detection result (address information) of the address sensor 42, the “storage area corresponding to the type of the objective lens 16 on the optical axis 10a” in the memory 38 is referred to, and the reference timing Tk is set. It will be initialized. As a result, good observation can be performed even if the type of the objective lens 16 positioned on the optical axis 10a changes.
[0072]
Further, in the above-described embodiment, an example of the industrial microscope 10 that observes, for example, a semiconductor wafer by epi-illumination is described. However, the present invention is a microscope that observes a biological specimen by epi-illumination or transmission illumination. It can also be applied to. When the specimen 11 is a biological specimen (for example, a cell), the inside of the specimen 11 has a three-dimensional structure. Therefore, by applying a focus offset by the above-described method, the specimen 11 is focused on an arbitrary surface to be observed in the thickness direction. be able to.
[0073]
In the above-described embodiment, an example in which the stage 12 is moved up and down to adjust the positional relationship between the sample 11 and the objective lens 16 has been described. However, the objective lens 16 may be moved up and down, or the objective lens 16 may be moved up and down. And the specimen 11 may be moved up and down.
[0074]
【The invention's effect】
As described above, according to the present invention, the focus offset range can be set wide.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an overall configuration of a microscope according to an embodiment.
FIG. 2 is a diagram for explaining an output timing of a light reception signal.
FIG. 3 is a diagram showing a block configuration of the microscope 10;
FIG. 4 is a diagram for explaining a change over time in the output of an integrator 32;
FIG. 5 is a diagram for explaining a relationship between an output of a subtracter and a Z position of a sample.
FIG. 6 is a flowchart showing an overall procedure of AF control in the microscope 10;
FIG. 7 is a diagram for explaining a downward focus offset.
FIG. 8 is a diagram for explaining a downward focus offset;
FIG. 9 is a diagram illustrating an upward focus offset.
FIG. 10 is a diagram illustrating an upward focus offset.
FIG. 11 is a diagram for explaining a reference timing setting range in the microscope.
12 is a diagram illustrating a focus offset range in the microscope 10. FIG.
FIG. 13 is a diagram illustrating a conventional focus detection signal.
FIG. 14 is a diagram illustrating a conventional DC offset method.
FIG. 15 is a diagram illustrating a focus offset range in a DC offset method.
[Explanation of symbols]
10 Microscope
11 specimens
12 stages
13 Light source
14 Condensing lens
15, 26 half mirror
16 Objective lens
17 Imaging lens
18 Prism
19 Eyepiece
21 Light source
22 Slit plate
23, 27 condenser lens
24 Shading plate
25 Dichroic mirror
28 Cylindrical lens
29 Light receiving element
30 Control device
32 integrator
33, 34 Sample hold circuit
35, 36 subtractor
37 CPU
38 memory
40 input devices
41 Offset input section

Claims (3)

Illumination means for irradiating the specimen with detection light via an objective lens;
The reflected light from the specimen is received through the objective lens, and the objective lens and the specimen are scanned sequentially from one to the other between the scanning start timing and the scanning end timing for outputting a light reception signal. A light receiving means for outputting a light reception signal based on the relative positional relationship of
An integrator for integrating the output received light signal;
The sample timing of the received light signal that is set between the start of scanning and the end of scanning and divides and outputs the signal integrated by the integrator is determined in advance as a reference timing (Tk). A sample-and-hold circuit that samples the output of the integrator;
A control signal corresponding to a deviation between an output timing (Tp) at which the peak of the light reception signal output from the light receiving means is output and a predetermined reference timing (Tk) is generated, and based on the control signal Control means for adjusting the relative positional relationship;
An input means for inputting an offset amount for a focus offset for changing a relative position between the objective lens and the specimen along an optical axis direction of the objective lens when changing the observation position of the specimen;
When the offset amount is input, the reference timing (Tk) at the scanning start timing to the scanning end timing for sequentially outputting the light receiving signal from the light receiving means is changed, and the offset amount “−ΔZa” is detected, The offset amount “−ΔZa” is converted into the change amount “+ ΔTa” of the reference timing (Tk), or the offset amount “+ ΔZa” is detected, and the offset amount “+ ΔZa” is changed to the change amount of the reference timing (Tk). An automatic focusing apparatus comprising: changing means for changing the reference timing (Tk) of the sample-and-hold circuit for changing the sample timing of the received light signal by converting to “−ΔTa” . The automatic focusing apparatus according to claim 1,
When the magnification of the objective lens used for observation is lower than that of the objective lens previously used , depending on the type of the objective lens positioned on the optical axis , the changing unit is configured to perform the reference timing ( An automatic focusing apparatus characterized in that the amount of change at one time when changing (Tk) is made larger than that of the objective lens previously used . An imaging optical system having an objective lens and forming an image of the specimen;
A microscope comprising the automatic focusing device according to claim 1 or 2 disposed on an optical axis of the objective lens.

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