JP2009098437A - Focus adjustment device and microscope device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus adjustment device in which a time required for performing focus detection is shortened in a pattern projection system. <P>SOLUTION: The focus adjustment device includes: a projection means projecting a pattern on a measurement object via a part of a pupil of an objective lens; a light receiving means including a light receiving element row comprising a plurality of focus detection light receiving elements receiving pattern images reflected from the measurement object; a focus detection means detecting a position of the pattern image projected on the light receiving element row on the basis of a light receiving signal from the light receiving means and obtaining a lateral shift amount between the position of the pattern image and a predetermined position on the light receiving element row; and a focusing means setting an adjustment speed for adjusting a relative gap between the objective lens and the measurement object on the basis of the lateral shift amount obtained by the focus detection means and leading to the focused state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a focus adjustment apparatus applied to a microscope apparatus and the like, and a microscope apparatus including the same.

As a lens focus detection method, there is a slit projection method mainly mounted on an industrial microscope. In the focus detection of the slit projection method, a pattern is projected onto an object through a part of the pupil of the objective lens, and a defocus signal (difference signal) is generated based on the reflected light imaged on the line sensor to detect the focus. (For example, refer to Patent Document 1).
JP 2002-277729 A

  However, according to this method, the focus control curve becomes an S-curve when the horizontal axis indicates the defocus amount and the vertical axis indicates the output level of the defocus signal. Then, only the defocus direction is obtained from the defocus signal, and control is performed at a focus adjustment speed along the S-curve according to the defocus direction. For this reason, when the defocus amount increases, the output level of the defocus signal decreases, and as a result, the drive speed also decreases and the time required for focus adjustment tends to be prolonged.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a focus adjustment apparatus that requires a short time for pattern projection focus detection. It is another object of the present invention to provide a high-performance microscope apparatus.

  The focus adjustment apparatus of the present invention includes a projection unit that projects a pattern onto a measurement target object through a part of a pupil of an objective lens, and a plurality of focus detection light sources that receive the pattern image reflected from the measurement target object. A light receiving means including a light receiving element array composed of light receiving elements; and a position of the pattern image projected on the light receiving element array based on a light reception signal from the light receiving means; and the position of the pattern image; A focus detection means for obtaining a lateral deviation amount with respect to a predetermined position on the light receiving element array, and a relative distance between the objective lens and the object to be measured based on the lateral deviation amount obtained by the focus detection means. Focus adjustment means for setting an adjustment speed to be adjusted and for bringing the focus into a focused state.

  Preferably, the focus detection unit obtains a distribution by performing signal processing on the sensor signal of each pixel on the light receiving element array in order to detect the position of the pattern image, and the pixel position on the light receiving element array. You may ask for.

  Preferably, the focus detection unit detects whether a sensor signal of each pixel exceeds a threshold, obtains an edge of the pattern image, and based on a pixel position corresponding to the edge, A position may be detected, and the lateral shift amount may be obtained from the position of the pattern image and a predetermined position on the light receiving element array.

  Preferably, the focus detection unit stores a pixel position on the light receiving element array where a false signal (a signal generated by stray light caused by an optical system including the type of the object to be measured or the objective lens) is generated. The pixel position on the light receiving element array where the pattern image is distributed is compared with the pixel position of the false signal stored in the storage unit, and the two pixel positions do not match. The lateral deviation amount may be obtained by judging the above.

  Preferably, the focus adjusting unit may perform stepwise driving speed setting based on the lateral shift amount.

  A microscope apparatus according to the present invention includes a microscope optical system for observing an image captured by an objective lens, and any one of the focus adjustment apparatuses described above that adjusts the focus of the objective lens.

  According to the present invention, it is possible to realize a focus adjustment apparatus that requires a short time for pattern projection focus detection. In addition, a high-performance microscope apparatus is realized.

  Hereinafter, embodiments of the focus adjustment device of the present invention will be described.

  FIG. 1 is a configuration diagram of the focus adjustment apparatus of the present embodiment. The focus adjustment apparatus shown in FIG. 1 is a focus adjustment apparatus equipped with a slit projection type focus detection optical system.

  In FIG. 1, an LED 7 emits infrared light for slit projection. Hereinafter, this infrared light is referred to as “slit projection AF light”. The slit projection AF light emitted from the LED 7 is a slit plate 8, a collector lens 9, a pupil mask 10, a half mirror 16, a chromatic aberration correction lens 30, a dichroic mirror 4, a first objective lens 3, a specimen 2, and a first objective. The light passes through the lens 3, the dichroic mirror 4, the chromatic aberration correction lens 30, the half mirror 16, and the second objective lens 17 before entering the line sensor 22.

  Here, a slit opening is formed in the center of the slit plate 8 as shown in FIG. Therefore, the slit projection AF light forms a slit-like infrared image in the vicinity of the object plane (here, the sample plane 2a). At this time, the slit projection AF light reflected by the sample surface 2 a forms a slit-like infrared image on the line sensor 22. Hereinafter, this infrared image is referred to as a “slit image”. The slit width direction of the slit image and the line direction of the line sensor 22 intersect each other.

  The pupil mask 10 transmits one of two lights obtained by dividing the slit projection AF light on a plane including the optical axis and shields the other. Therefore, when the slit projection type AF light reciprocates through the first objective lens 3, it passes through different positions on the pupil of the first objective lens 3 in the forward path and the backward path. Therefore, the slit image formed on the line sensor 22 is laterally shifted according to the defocus amount of the first objective lens 3 (shift in the optical axis direction between the focal point of the first objective lens 3 and the sample surface 2a). It is assumed that the center of gravity position of the slit image formed on the line sensor 22 when the defocus amount of the first objective lens 3 is zero is measured in advance.

  In the focus adjusting apparatus described above, the CPU 24 controls the LED 7 that is a slit projection type light source. Since the slit projection type slit image is formed during the period in which the LED 7 is lit, an output signal corresponding to the slit image can be obtained from the line sensor 22.

  The output signal of the line sensor 22 is taken into the signal processing unit 23. When the signal processing unit 23 generates some signals based on the captured signals, the signal processing unit 23 gives them to the CPU 24. When the CPU 24 generates a slit projection type signal based on the given signal, the CPU 24 designates a driving direction and a driving speed in accordance with the signal to the vertical movement driving unit (such as a pulse motor) 25. The vertical movement drive unit 25 adjusts the focus of the first objective lens 3 by driving the first objective lens 3 in the optical axis direction at a designated drive direction and drive speed. Although the vertical movement drive unit 25 may be driven by the stage 1 instead of the first objective lens 3, the following description is based on the assumption that the first objective lens 3 is used.

  The CPU 24 can also control the light amount of the LED 7 and can switch the charge accumulation time (scanning time) of the line sensor 22 as necessary.

  Next, signal generation operations of the signal processing unit 23 and the CPU 24 will be described.

  2, 3 and 4 are diagrams for explaining the signal generation operation. 2, 3, and 4 show the relationship between the defocus amount of the first objective lens 3 and the sensor signal of the line sensor 22. (A) is a defocus amount, (b) is a behavior of light incident on the line sensor 22, and (c) is a sensor signal of the line sensor 22.

The signal processing unit 23 acquires a peak voltage signal V ₁₀₂ obtained by peak-holding the sensor signal and a representative position PX _C obtained by a method described later, and provides the CPU 24 with it.

The CPU 24 uses the peak voltage signal V ₁₀₂ given from the signal processing unit 23 as an evaluation value for evaluating the generation state of the slit projection type defocus signal. Further, the CPU 24 uses the representative position PX _C given from the signal processing unit 23 for speed setting to be described later.

As shown in FIG. 2A, when the focal position of the first objective lens 3 is on the back side (rear pin position) from the sample surface 2a, the sensor signal of the line sensor 22 is as shown in FIG. Are distributed on the R side of the in-focus position 100. Further, the representative position PX _C is distributed on the R side from the in-focus position 100.

As shown in FIG. 3A, when the focal position of the first objective lens 3 is at the sample surface 2a (in-focus position), the sensor signal of the line sensor 22 is in-focus as shown in FIG. 3C. Distributed at position 100. The representative position PX _C is at a position that substantially overlaps the in-focus position 100.

As shown in FIG. 4A, when the focal position of the first objective lens 3 is in front of the sample surface 2a (front pin position), the sensor signal of the line sensor 22 is as shown in FIG. 4C. Are distributed on the F side from the in-focus position 100. The representative position PX _C is distributed on the F side with respect to the in-focus position 100.

According to the tendency described above, when the representative position PX _C is distributed on the F side, the driving direction of the first objective lens 3 is set to the upward direction (direction away from the sample 2), and the representative position PX _C is distributed on the F side. In some cases, the driving direction of the first objective lens 3 may be a downward direction (a direction approaching the sample 2).

Next, how to obtain the above-described representative position PX _C will be described. FIG. 5A is a diagram illustrating a sensor signal of the line sensor 22. The horizontal axis indicates the pixel position on the line sensor 22, and the vertical axis indicates the magnitude of the sensor signal. The signal processing unit 23 sequentially compares the sensor signal from the line sensor 22 with the threshold value T. The threshold value T is a threshold value for recognizing the focal position of the first objective lens 3 and is determined in advance by an experiment or the like. The signal processing unit 23 obtains the pixel position PX _S on the most front pin side where the sensor signal intersects with the threshold value T and the pixel position PX _L on the most rear pin side where the sensor signal intersects with the threshold value T, and the representative position PX is obtained by the following equation. _C is calculated.

Representative position PX _C = (PX _S + PX _L ) / 2 (Expression 1)
The representative position PX _C obtained in this way indicates the current focal position of the objective lens, and is used for setting the speed described later.

Incidentally, as the representative position may be used pixel position PX _P corresponding to the peak voltage signal V ₁₀₂ described above. May also be used those obtained by adding to an appropriate weighting the pixel position PX _P corresponding to the representative position PX _C and a peak voltage signal V ₁₀₂ described above as the representative value.

Further, when the sensor signal does not have a smooth convex shape as shown in FIG. 5B, the representative position PX _C and the pixel position PX _P can be calculated in the same manner. That is, as shown in FIG. 5B, the pixel position PX _S on the most front pin side where the sensor signal intersects with the threshold value T and the pixel position PX _L on the most rear pin side where the sensor signal intersects with the threshold value T are obtained. 1, the representative position PX _C can be calculated.

  Next, a change pattern of the driving speed of the first objective lens 3 at the time of focus adjustment according to the present embodiment will be described in detail.

  The horizontal axis in FIG. 6 indicates the pixel position on the line sensor 22, and the vertical axis in FIG. 6A indicates a sensor signal generated by the line sensor 22. FIG. 6B shows a change pattern of the driving speed, and the vertical axis of FIG. 6B shows the driving speed.

In FIG. 6A, T represents the above-described threshold value T. In FIG. 6A, PX _S (X = 1 to 7) indicates a point on the most front pin side where the sensor signal intersects with the threshold T, and PX _L (X = 1 to 7) indicates that the sensor signal has the threshold T. The point on the back pin side that intersects is shown.

The signal processing unit 23, as described above, to calculate a representative position PX _C (X = 1~7) using Equation 1, and outputs the representative position PX _C a (X = 1 to 7) in CPU 24. The CPU 24 sets the drive speed based on the representative position PX _C (X = 1 to 7).

In FIG. 6A, the representative position PX _C (X = 1 to 3) is when the focal position of the first objective lens 3 is on the near side (front pin position) from the sample surface 2a as shown in FIG. This is the representative position. The representative position P4X _C is a representative position when the focal position of the first objective lens 3 is on the sample surface 2a as shown in FIG. Further, the representative position PX _C (X = 5 to 7) is a representative position when the focal position of the first objective lens 3 is on the back side (rear pin position) from the sample surface 2a as shown in FIG. .

CPU24, as shown in FIG. 6 (b), set in the region A7 of defocus side of the region A1 and P7 _C defocus side than P1 _C, the absolute value of the driving speed V1. Further, as shown in FIG. 6B, the CPU 24 sets the absolute value of the driving speed to V2 in the region A2 of P1 _{C to} P2 _C and the region A6 of P6 _{C to} P7 _C. Further, as shown in FIG. 6B, the CPU 24 sets the absolute value of the driving speed to V3 in the region A3 of P2 _{C to} P3 _C and the region A5 of P5 _{C to} P6 _C. Further, as shown in FIG. 6B, the CPU 24 determines that the in-focus state is set in the region A4 of P3 _{C to} P5 _C and sets the drive speed to V4 = 0. Note that V3 <V2 <V1.

  As a result, the absolute value of the driving speed of the first objective lens 3 is faster as it is farther from the focused state, and is smaller and slower as it is closer to the focused state.

  Therefore, the focus adjustment of this embodiment is efficient. By the way, in the conventional slit projection type focus adjustment device, the drive speed is set faster as the defocus signal is larger, and the drive speed is set slower as the defocus signal is smaller. The speed could be set low and was inefficient.

  In addition, as shown in FIG. 6B, the CPU 24 of the present embodiment sets the number of steps of the driving speed to 4 per direction, but may be a number other than 4. Further, the number of steps may be changed according to the type of the first objective lens 3.

  Further, as shown in FIG. 6B, the CPU 24 of the present embodiment changes the driving speed in a step shape, but a part thereof may be a polygonal line or a curved line.

However, when the representative position PX _C shifts from the region A3 or A5 to the region A4, it is desirable to make it stepped (that is, rapidly shift to zero) in order to prevent overrun of the first objective lens 3. . In addition, the driving speed V4 in the regions A3 and A5 is desirably set to a sufficiently low speed (corresponding to the self-starting frequency of the motor) determined by the characteristics of the motor in order to prevent the motor from stepping out during a sudden stop.

  Next, the focus adjustment operation by the CPU 24 will be described. First, a false signal related to the focus adjustment operation will be described with reference to FIG. The sensor signal may generate a false signal as shown in FIG. The false signal includes ghost, flare, diffracted light, and the like, and is caused by stray light generated due to the type of specimen (reflectance of the specimen surface, etc.) and the optical system including the objective lens. When these false signals are generated, there is a case where the focus adjustment is performed based on the false signals without being based on the signal that should be focused. Further, it is known that this false signal is generated at a certain pixel position on the line sensor 22 regardless of the type of specimen and the optical system.

  Therefore, in the present embodiment, the memory unit of the CPU 24 analyzes a false signal in advance and stores a pixel position where the false signal is generated.

  FIG. 8 is a flow of the focus adjustment operation by the CPU 24.

  Step S1: At the start of the flow, the distance between the first objective lens 3 and the sample 2 is secured to some extent.

Step S2: CPU 24, the charge accumulation time of the line sensor 22 (scanning time) is set to the standard value 2.7 ms, refer to peak voltage signal V ₁₀₂ supplied from the signal processing unit 23 at this time. Further CPU24 adjusts the amount of LED7 order to the peak voltage signal V ₁₀₂ to or higher than the threshold V _200.

Step S3: CPU 24 refers to the peak voltage signal V ₁₀₂ supplied from the signal processing unit 23 after adjusting, if the peak voltage signal V ₁₀₂ has been a threshold V ₂₀₀ or more, a defocus signal of the slit projection system proceeds is determined that can be satisfactorily produced (possible focus detection by the slit projection system) to step S4, if less than the threshold value V _200, it can not be satisfactorily generate the defocus signals slit projection system by (a slit projection type It is determined that focus detection is impossible), and the process proceeds to step S6.

Step S4: The CPU 24 confirms the focal position by calculating the above-described representative position PX _C based on the sensor signal given from the signal processing unit 23, and proceeds to step S5.

  Step S5: The CPU 24 compares the focal position confirmed in step S4 with the pixel position where the false signal stored in advance is stored, and determines whether or not the focal position confirmed in step S4 corresponds to the position of the false signal. judge. When the CPU 24 determines that the position corresponds to the position of the false signal (focus adjustment is performed based on the false signal), the CPU 24 proceeds to step S10. On the other hand, if the CPU 24 determines that the position does not correspond to the position of the false signal (the focus adjustment is not performed based on the false signal), the CPU 24 proceeds to step S8.

Step S6: CPU 24, if the charge accumulation time is changed (scanning time) to 7 ms, the peak voltage signal V ₁₀₂ supplied from the signal processing unit 23 after the change of the line sensor 22 to the threshold V ₂₀₀ or more, slits projection and determined to be the focus detection method proceeds to step S4, if less than the threshold value V _200, the process proceeds to decision impossible to focus detection of the slit projection system to step S7.

  Step S7: The CPU 24 determines that the focal position of the first objective lens 3 is out of the adjustable range, and ends the flow.

Step S8: If the representative position PX _C calculated in step S4 is within the area A4 in FIG. Proceed to On the other hand, if the representative position PX _C is an area other than the area A4 in FIG. 6, the CPU 24 determines that the sample surface 2a is not within the depth of focus of the first objective lens 3, and proceeds to step 10. .

  Step S9: The CPU 24 sets the driving speed of the first objective lens 3 to zero and ends the flow.

  Step S10: The CPU 24 refers to the focal position confirmed in step S4, and sets the drive speed as described with reference to FIG. Then, the CPU 24 returns to step S2.

  As described above, according to the present embodiment, focus adjustment can be performed without using a defocus signal corresponding to a so-called S-shaped curve. Therefore, a focus adjustment device with a short required time is realized in the focus detection by the slit projection method.

  In addition, according to the present embodiment, by appropriately avoiding false signals in focus adjustment, it is possible to prevent an increase in time required for focus adjustment due to erroneous detection and erroneous detection.

  Further, in the present embodiment, the focus adjustment apparatus having only the slit projection method is described as an example, but a so-called focus detection optical system having a slit projection method and a focus detection optical system having a contrast detection method are both mounted. The present invention can be similarly applied to a hybrid focus adjustment apparatus.

  Further, the focus adjustment apparatus of the present embodiment can be applied to an industrial or biological microscope apparatus. The configuration of the microscope apparatus is, for example, as shown in FIG. In FIG. 9, most of the focus adjusting device (the tip of the half mirror 16 shown in FIG. 1) is omitted.

  As shown in FIG. 9, the microscope apparatus includes a light source 31 that emits visible light for observation, an illumination optical system 32 that projects an image of the light source 31 onto the pupil of the first objective lens 3, and the illumination optical system 3. A half mirror 33 that guides visible light to the first objective lens 3, an observation optical system 34 that forms an image of visible light (observation light) from the specimen 2 captured by the first objective lens 3, and the observation optical system 34 are formed. An image sensor 35 that captures a visible image is provided. If the focus adjustment apparatus of the present embodiment is applied to this microscope apparatus, it is possible to perform focus adjustment with a short required time, and the performance of the microscope apparatus is also improved.

  In addition, the focus adjustment apparatus of the present embodiment employs a slit projection type focus detection optical system (the shape of the pattern projected onto the sample 2 is slit) as the pattern projection type focus detection optical system. The shape of the pattern to be projected may be replaced with another shape such as a dot shape. However, the slit shape has an advantage that the optical elements such as the line sensor 22 can be easily aligned.

It is a block diagram of a focus adjustment apparatus. It is a figure explaining the back pin state of a slit projection system. It is a figure explaining the focusing state of a slit projection system. It is a figure explaining the front pin state of a slit projection system. It is a diagram illustrating a method of determining the representative position PX _C. It is a figure explaining the drive speed of the 1st objective lens. It is a figure explaining a false signal. It is a flowchart of focus adjustment. It is a block diagram of the microscope apparatus which can apply a focus adjustment apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Stage, 2 ... Specimen, 3 ... 1st objective lens, 4 ... Dichroic mirror, 7 ... LED, 8 ... Slit plate, 9 ... Collector lens, 10 ... Pupil mask, 16 ... Half mirror, 17 ... 2nd objective lens , 22 ... line sensor, 23 ... signal processing unit, 24 ... CPU, 25 ... vertical movement drive unit, 26 ... LED switching unit, 30 ... chromatic aberration correction lens

Claims (6)

A projection means for projecting a pattern onto the object to be measured through a part of the pupil of the objective lens;
A light receiving means comprising a light receiving element array comprising a plurality of focus detection light receiving elements for receiving the pattern image reflected from the measurement object;
A position of the pattern image projected on the light receiving element array is detected based on a light receiving signal from the light receiving means, and a lateral shift between the position of the pattern image and a predetermined position on the light receiving element array Focus detection means for determining the quantity;
A focus adjusting means for setting an adjustment speed for adjusting a relative distance between the objective lens and the object to be measured based on the lateral deviation amount obtained by the focus detecting means, and for leading to a focused state. Focus adjustment device characterized by. The focus adjustment apparatus according to claim 1,
In order to detect the position of the pattern image, the focus detection unit obtains a distribution by performing signal processing on a sensor signal of each pixel on the light receiving element array to obtain a pixel position on the light receiving element array. Focus adjustment device. The focusing apparatus according to claim 2, wherein
The focus detection means detects whether or not the sensor signal of each pixel exceeds a threshold, obtains an edge of the pattern image, detects the position of the pattern image based on the pixel position corresponding to the edge, The focus adjustment apparatus, wherein the lateral shift amount is obtained from a position of the pattern image and a predetermined position on the light receiving element array. The focusing apparatus according to claim 2, wherein
The focus detection unit includes a storage unit that stores a pixel position on the light receiving element array where a false signal (a signal generated by stray light caused by the type of the measurement target object or the optical system including the objective lens) is generated. The pixel position on the light receiving element array in which the pattern image is distributed is compared with the pixel position of the false signal stored in the storage unit, and it is determined that the two pixel positions do not match. A focus adjustment device characterized by obtaining a lateral shift amount. The focus adjustment apparatus according to claim 1,
The focus adjustment device, wherein the focus adjustment unit performs stepwise drive speed setting based on the lateral shift amount. A microscope optical system for observing an image captured by the objective lens;
A microscope apparatus comprising: the focus adjustment apparatus according to claim 1, which performs focus adjustment of the objective lens.

Images