JPH049810A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To position an object body at the optimum focusing position that a photographer intends stably with good reproducibility and high accuracy at all times by selecting a focusing position arithmetic method for calculating the optimum focusing position at the time of automatic focusing among plural focusing position arithmetic methods according to evaluation characteristics. CONSTITUTION:The device is provided with focusing extent evaluating means 1-1 to 1-n which use mutually different focusing position arithmetic methods and a user puts a stage in Z-directional scanning operation within a necessary range including the optimum focusing position adjusted manually to find respectively evaluated values at respective positions. Then the focusing position arithmetic method which provides the optimum focusing position is selected among the focusing extent evaluating methods 1-1 to 1-n according to those evaluated values. Consequently, the object body can be positioned at the optimum focusing position where the intention of the photographer is reflected stably with good reproducibility and high accuracy at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic focusing device for optical instruments such as microscopes.

[Conventional technology]

As a conventional automatic focusing device for a microscope or the like, there is one disclosed, for example, in Japanese Patent Laid-Open No. 143710/1983. In this automatic focusing device, the optimal focusing position calculation method that is considered to be optimal for the entire target object that is scheduled to be used is fixed in advance, and the focusing operation is performed using this method as shown in Fig. 12. , the distance between the objective optical system and the target object is determined by the automatic focusing function, and if the determined focal position of the target object is not the optimal focusing position for the user, the automatic focusing function is used to determine the distance between the objective optical system and the target object. By giving an offset to the position, the focus position by the automatic focus function is made optimal for the user.

In addition, as another automatic focusing device,
Publication No. 1 states that a high frequency component is extracted from among the spatial frequency components of an image of a target object by a phase difference optical system, and the high frequency component is extracted within a certain distance range from the relative distance between the phase difference optical system and the target object at which the high frequency component is maximum. discloses that when the high frequency component of the spatial frequency component has a second peak, the focusing position is determined based on the relative distance at which the high frequency component of the spatial frequency component becomes maximum.

[Problem to be solved by the invention]

However, in the automatic focusing device disclosed in Japanese Patent Application Laid-Open No. 61-143710, the optimum focusing position calculation method that is considered to be optimal for the entire target object that is planned to be used is fixed in advance. Therefore, when focusing, for example, on a special specimen, there is a problem that the focusing position itself is not stable (and a focusing operation with good reproducibility cannot be expected).

Furthermore, in the automatic focusing device disclosed in Japanese Patent Publication No. 62-32761, the focusing position is uniquely determined based on the relative distance at which the high frequency component of the spatial frequency component is maximum. There is a problem in that it is not possible to reflect different optimal focusing positions.

This invention was made by focusing on these conventional problems, and it is an automatic focusing system that is appropriately configured to always stably and accurately position the optimal focusing position intended by the user with good reproducibility. The purpose is to provide a focusing device.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a driving means for relatively driving the optical system and the target object in the optical axis direction of the optical system, and a distance detecting means for detecting the relative distance between the optical system and the target object. , a focus position detection means for detecting evaluation characteristics representing a focus state using a plurality of different focus position calculation methods based on information tS of the target object obtained by the optical system; determining means for determining a focusing position calculation method suitable for focusing on a target object from the method, and determining means for determining a focusing position calculation method suitable for focusing on a target object from the method, and said optical system within a required relative distance range including said relative distance adjusted to a focusing position intended by a user. and relatively drive the target object to detect evaluation characteristics respectively using the plurality of focus position calculation methods, and determine the optimum when performing automatic focusing from the plurality of focus position calculation methods based on these evaluation characteristics. The system is configured to select a focus position calculation method that provides a suitable focus position.

[Effect]

FIG. 1 shows a conceptual diagram of the present invention, which is applied to an ordinary optical microscope in which a stage is moved in the direction of the optical axis (Z direction) of an objective optical system to perform a mode operation. This automatic focusing device includes a plurality of focus degree evaluation means 11 to 1- which calculate the degree of focus using different focus position calculation methods.
n, and a control means (C) for controlling the operation of the entire automatic focusing device.
P[J) 2, a memory 3 that stores the operating program of the CPU 2 and various necessary data, and a stage driving means 4 that drives the stage on which the sample specimen is placed in the Z direction.
and stage position detection means 5 for detecting the position of the stage in the Z direction.

In this invention, as shown in the flowchart in FIG.
After the user places the sample specimen on the stage and manually adjusts the stage to the user's optimal focusing position, the initial setting operation of the automatic focusing device is started. In this initial setting operation, the stage is first scanned in the Z direction by the stage driving means 4 in a required range in the Z direction including the optimum focus position adjusted by the user, and the stage position is detected in the scanning range. Corresponding to the position data from the means 5, evaluation values are determined by the focusing degree evaluation means 1-1 to 1-n based on the focusing position calculation method stored in the memory 3, and these evaluation values are stored in the memory. Store in 3. Next, when the scanning of the stage in the Z direction is completed, the focusing degree evaluation means 1-1 to 1 stored in the memory 3
Based on the evaluation value from -n, select the focus position calculation method that gives the optimum focus position from the focus degree evaluation means l-1 to 1-n according to the program in the memory 3, and select it. Store in memory 3. Thereafter, for the same type of sample specimen, while moving the stage in the Z direction, the stage is automatically positioned at the optimal focusing position with respect to the objective optical system based on the evaluation value from the selected focusing degree evaluation means. .

Note that the evaluation value at each position in the Z-direction scan range of the stage by each of the focusing degree evaluation means 1-1 to l-n is based on information at each position while scanning the stage in the Z-direction, such as image information, etc. The calculation may be performed based on the information, or the information may be stored at each position in the scan range and the calculation may be performed based on the stored information after the scan is completed.

As described above, a plurality of focus degree evaluation means 1-1 to 1-n each using different focus position calculation methods are provided, and the stage is set within a required range including the optimum focus position manually adjusted by the user. A focus position calculation method that scans in the Z direction and obtains evaluation values at each position, and then uses the focus degree evaluation means l-1-1-n to determine the optimum focus position based on those evaluation values. By selecting the target object, the optimum focus position that reflects the user's intention can be consistently and accurately positioned with good reproducibility, and the optimum focus position calculation method can also be used for unknown specimens. Automatic focusing is possible with

Note that here, a focus degree evaluation means is provided separately for ease of understanding, but the C
It can also be processed in the PU.

〔Example〕

FIG. 3 is a block diagram showing a first embodiment of the invention. This example is applied to a marine optical microscope, where a microscope image is captured and the focus state is determined by a well-known contrast method that evaluates the sharpness of the image to indicate how close or far it is in focus. It is designed to detect.

The microscope image is input to the image input section 11 and converted into an image signal. The image input unit 11 is configured with a solid-state image sensor such as a CCD, and is connected to a calculation and control unit (CPU).
) 12 via a timing generator 13 and a clock driver 14, and the image signal is sent to a CPL 11 via a head amplifier 5, a sample hold circuit 16, and an analog-to-digital (A/D) conversion circuit 17.
2. The storage time of the microscope images in the image input section 11 is configured to be controllable by the CPU 12 via the timing generator 13 and the clock driver 14, and the gain of the head amplifier 15 is also configured to be controllable by the CPU 12.

In this embodiment, focus adjustment is performed by moving the stage on which the specimen is placed in the optical axis direction (Z direction) of the objective optical system. For this reason, a stage drive device 21 that drives the stage in the Z direction is provided, and this stage drive device 21 is
The controller 22 and the driver 23 are used to drive the controller 22 and the driver 23. Note that the stage drive device 21 includes, for example, a DC motor or a stepping motor.

Further, in order to detect the position in two directions of the stage driven by the stage drive device 21, a stage position detection device 25 is provided, and its output is supplied to the CPU 12. This stage position detection device 25 is configured with, for example, an encoder.

Furthermore, the CPU 12 includes a RAM 31 for data storage,
A ROM 32 for storing programs, an input/display controller 35 for controlling the key input section 33 and the display device 34, and an input/display controller 35 for controlling the microscope's optical system information such as the type of objective lens and magnification, and for other functions. An interface 36 for transmitting and receiving information is connected and provided.

The operation of this embodiment will be explained below.

There are various types of specimens that can be observed under a microscope, but in actual use, specimens of the same type are very often observed.

Therefore, in this embodiment, a standard focusing position calculation method is used when observing various specimens, and a plurality of different focusing position calculation methods are used when observing the same type of specimen, including this standard focusing position calculation method. is stored in the ROM 32, and in the observation mode of various specimens, automatic focusing is performed using the standard focusing position calculation method, and in the observation mode of the same kind of specimen, multiple From among the focus position calculation methods, the optimum focus position calculation method for the specimen is selected and automatic focusing is performed.

In this homogeneous specimen observation mode, the user selects a representative specimen from among the specimens to be observed, places it on the stage, adjusts the stage to his or her preferred focusing position, and then The initial setting operation is started by key operation.

When the initial setting operation starts, the CPtJ12 first imports the stage position data of the focus position adjusted by the user from the stage position detection device 25, and also accesses the microscope to obtain objective data such as the type of the current objective lens. The scanning range of the stage in the Z direction including the focus position adjusted by the user is determined based on the data acquired through the interface 36. Next, the gain of the head amplifier 15 and the accumulation time of the microscope image for the image input section are set by the CPU 12 based on the image information currently being input to the image input section 11 in the focused state adjusted by the user. Then, the stage is roughly scanned in the above scanning range, and the CPL 112 determines whether the set gain of the head amplifier 15 and the storage time of the image input section II are appropriate based on the level of the input image information, If the settings are inappropriate, correct them.

After completing the above operations, determine the step width during scanning based on the objective data from the microscope, and then move the stage within the above scan range and acquire image information for each step width within that scan range. take in. After that, when the image information at each step position is completed, the ROM 3 is loaded based on the image information at each step position.
Contrast evaluation values are obtained using a plurality of different focusing position calculation methods stored in 2, and the contrast evaluation values obtained by each of these focusing position calculation methods are stored in the RAM 31.

Here, the contrast evaluation value is calculated by calculating the moving average using the formula shown below based on the information of the obtained image 1.For simplicity, the above formula is shown for the -dimensional one, or actually Find the moving average y1 of L pieces of input pixel information X1,
The difference is calculated using the second equation using yl as X2, and finally Vt is calculated.

In this example, as a plurality of different focusing position calculation methods, the above equation (7) L is L=1.5.8.10 (7)
Four types of focusing position calculation methods are stored in the ROM 32.

When contrast evaluation values are obtained using each focus position calculation method in this manner, evaluation value characteristics as shown in FIG. 4, for example, are obtained.

Next, based on the program stored in the ROM 32, from the evaluation value characteristics obtained by each focus position calculation method, a focus position calculation method having a peak value higher than a predetermined value y th,
In the case of FIG. 4, the focusing position calculation method of L=1.5.8 is selected. Then, from these selected focusing position calculation methods,
For example, as shown in Figure 5, the change in vL within the depth of focus of the objective lens △VL is the maximum, and in the case of Figure 4, L
The focusing position calculation method of =8 is selected as the optimum focusing position calculation method by calculation and stored in RAM3], and from now on, this f? A
Automatic focusing is performed using the optimum focusing position calculation method stored in M31.

As described above, according to this embodiment, the stage is scanned in the Z direction in the required scan range including the focus position manually adjusted by the user, and a different focus position calculation method is used at each position. Since evaluation values are determined and a focusing position calculation method is selected based on those evaluation values, the optimum focusing position that reflects the user's intention is always maintained. positioning with high precision.

Note that in the automatic focusing operation after selecting the optimum focusing position calculation method, the evaluation value V+ or the predetermined value V1. If the Z-direction scan range of the stage is determined by taking into account the range higher than that (Za-Zb in Fig. 4), the error in the thickness of the sample, and the error in the stage height, automatic focusing can be achieved at high speed. can be done.

FIG. 6 shows a second embodiment of the invention. In this embodiment, a digital signal processor (DSP) 41 as a high-speed arithmetic unit and a memory 42 for this DSP 41 are added to the configuration shown in FIG. This system enables high-speed operation and detects the focused state based on the spatial frequency distribution of the image as a method of calculating the focused position.The other configuration is the same as that shown in FIG.

The operation of this embodiment will be explained below.

Once the scan range of the stage is determined in the same manner as in the first embodiment, while the stage is moved within the scan range, image information at each position is captured and FFT processing is performed by the DSP 41. Here, if the number of pixels of the image information 11 is one-dimensionally 512 pixels, one side of the real part of the Fourier transformed result will be as shown in FIG. 7, for example.

Therefore, in this embodiment, the size of the power spectrum of the real part obtained by Fourier transform or the spatial frequency that changes greatly depending on the scan range, for example, fl, f, etc.
and fc, they are stored in advance in the DSP meme memory 4.
2, and the change characteristics of fl, f, and f of the captured image information are determined as shown in FIG.

As described above, image information fl in the scan range,
After finding the change characteristics of f and fe, from the change characteristics, the power spectrum becomes the maximum near the focusing position that has been manually adjusted in advance, and the spatial frequency that gives the change characteristics with a large level, in the case of Fig. 8, is the spatial frequency. The frequency f is selected as the optimal focusing position calculation method and stored in the DSP meme memory 42. Thereafter, in accordance with the optimal focus position calculation method stored in this DSP meme memory 42, the DSP 41 configures a digital bandpass filter centered around that frequency, and the input image information is filtered and focused using this. Autofocus is performed while evaluating the focus level.

As described above, according to this embodiment, the stage is scanned in the Z direction in the required scanning range including the focusing position manually adjusted by the user, and different spatial frequencies (focusing The power spectrum of the focus position calculation method) is determined, and the spatial frequency that gives the optimal focus position (optimum focus position calculation method) is selected based on the change in the power spectrum, so it is possible to find the optimal filter for the sample. Based on the processed image information, it is possible to evaluate the degree of focus with high precision, and thus the sample specimen can be always stably and precisely positioned at the optimal focus position that reflects the user's intentions. I can do something.

Furthermore, by selecting the optimal spatial frequency through initial settings as described above, it is possible to perform filter optimization, which is difficult to do in real time even when using the DSP 41.

FIG. 9 shows a third embodiment of the invention. This embodiment uses an automatic focusing device 4 having the configuration shown in FIG.
5 with an image processing device 46 and a computer 47 added thereto. In this way, by adding the image processing device 46 and the computer 47, the optimal focusing position calculation method can be selected using their memory and calculation functions, so that the calculation capacity and memory size of the automatic focusing device 45 can be reduced. Therefore, it is possible to reduce the cost and size. In addition, a complex focus position calculation method that is not possible in the first and second embodiments, or a focus position calculation method that provides the optimal focus position from more of the same type or multiple types of focus position calculation methods may be selected. It also becomes possible.

Note that the present invention is not limited only to the embodiments described above, and numerous modifications and changes are possible. For example, in the above-described embodiment, the image input section 11 is configured with a solid-state imaging device such as a COD, or may be configured with a general-purpose TV left camera.

In addition, in the above-described embodiment, the stage position detection device 25 such as an encoder is provided to detect the position of the stage in the Z direction, or if a stepping motor is used as the stage drive device 21, its drive pulse is C.P.
It is also possible to obtain stage position data by counting by U12.

Furthermore, the adjustment of the relative distance between the sample specimen and the objective optical system is not limited to moving the stage in the Z direction as described above, but may be performed by moving the objective optical system in the Z direction.

In addition, in the first embodiment, the contrast evaluation function of the above formula is used as the focus position calculation method.
Although the number of types is used, it is not limited to four types, or if the capacity of the ROM 32 is large, more calculation methods may be stored and the optimal one may be selected. In this way, If more calculation methods are selected, further optimization can be expected.Furthermore, the optimal focus position calculation method may be selected by combining the contrast evaluation value and its vL characteristic. In this way, the optimal focusing position calculation method can be determined while balancing high speed and accuracy.

In addition to selecting the focus position calculation method that provides the optimal focus position, it is also possible to appropriately combine focus position calculation methods obtained from multiple information processing methods and use them as the optimal focus position calculation method. Become.

For example, in addition to the above-mentioned contrast method, is there a method to obtain a luminance histogram, find its dispersion, and calculate the focus position from the obtained dispersion? By combining one and one of the evaluation value characteristics obtained from the brightness histogram and adding them, it is also possible to perform focus control using an optimal focusing position calculation method that utilizes both characteristics.

Furthermore, when observing a relatively thick sample specimen for which stable operation is difficult using normal focusing methods, the VL characteristic may become as shown in FIG. 1O.

In such a case, it is also possible to calculate dVL/dZ to obtain a dvL/dZ characteristic as shown in FIG. 11, and select a method with one zero cross as the optimum focusing position calculation method. Further, in this case, if the peak of the selected V characteristic is deviated from the in-focus position, the offset value may be set in advance. In addition, zero cross is 1
If there is no peak and the VL has multiple peaks, select the peak.

Further, the optimal focusing position calculation method may be selected by using a plurality of samples and taking into consideration the average and variance of the data. In this way, it becomes possible to select a more reliable optimal focusing position calculation method.

Furthermore, if focusing on a specific pattern of the sample specimen is important, you can add conditions such as locating the area with the specific pattern at the center of the field of view during the initial settings to evaluate the degree of focus during the initial settings. It can be done efficiently.

Further, the present invention is not limited to automatic focusing in the above-mentioned microscope, but can be effectively applied to automatic focusing in various optical instruments.

〔Effect of the invention〕

As described above, according to the present invention, the optical system and the target object are relatively driven within a required relative distance range that includes the relative distance between the optical system and the target object that are adjusted to the focusing position intended by the user. Then, each of the evaluation characteristics is detected using multiple focus position calculation methods, and based on these evaluation characteristics, a focus position calculation method that provides the optimal focus position when performing automatic focusing is determined from the multiple focus position calculation methods. Since the selection is made, it is possible to always stably and accurately position the target object at the optimal focusing position intended by the user with good reproducibility.

Furthermore, when applied to a microscope, it is possible to evaluate the microscopy method to be used, characteristics of the mirror base to be used, sample preparation, etc. at the time of initial setup, so essentially the optimal focusing position calculation method can be determined. Therefore, it is possible to autofocus with high precision and high speed, and it is also possible to effectively deal with samples that have been difficult to deal with in the past.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of this invention, Fig. 2 is a flowchart for explaining its operation, Fig. 3 is a block diagram showing a first embodiment of this invention, and Figs. 4 and 5 illustrate its operation. Figure 6 is a block diagram showing a second embodiment of the invention; Figures 7 and 8 are diagrams explaining its operation; Figure 9 is a third embodiment of the invention. FIGS. 10 and 11 are diagrams for explaining the invention in detail, and FIG. 12 is a diagram for explaining the conventional technique. 1-1 to 1-n-Focus degree evaluation means 2...Contouring means (CPU) 3--Memory 4--Stage driving means 5--Stage position detection means 11--Image Input section 12 - Arithmetic control unit (CPU) 13 - Timing generator 14 - Clock driver 15 - Head amplifier 16
Sample hold circuit 17- Analog-digital (A/D) conversion circuit 21-
Stage drive device 22- Controller 23---
Driver 25- Stage position detection device 31
-RAM 32-ROM33・-Key human power section 34-Display device input/display controller

Claims (1)

[Scope of Claims] 1. Driving means for relatively driving the optical system and the target object in the direction of the optical axis of the optical system; distance detecting means for detecting the relative distance between the optical system and the target object; a focus position detection means for detecting evaluation characteristics representing a focus state using a plurality of different focus position calculation methods based on information about the target object obtained by the system; determining means for determining a focusing position calculation method suitable for focusing the optical system and the target object in a required relative distance range including the relative distance adjusted to the focusing position intended by the user. drive relatively, detect evaluation characteristics using each of the plurality of focus position calculation methods, and determine an optimal focus position for performing automatic focusing from the plurality of focus position calculation methods based on these evaluation characteristics. An automatic focusing device characterized in that it is configured to determine a focusing position calculation method to be applied. 2. Detect evaluation characteristics for a plurality of target objects using the plurality of focus position calculation methods, and determine optimal focus when performing automatic focusing from the plurality of focus position calculation methods based on these evaluation characteristics. 2. The automatic focusing device according to claim 1, wherein the automatic focusing device is configured to select a focusing position calculation method that provides a focusing position. 3. The present invention is characterized in that the focus position calculation method that provides the optimum focus position is determined in combination based on evaluation characteristics determined by a plurality of focus position calculation methods in accordance with a plurality of information processing methods. The automatic focusing device according to item 1.