JP3423091B2 - Microscope and automatic focus detection method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microscope and its automatic focus detection method.

[0002]

2. Description of the Related Art Conventionally, as an automatic focus detection method used in a microscope, as disclosed in JP-A-63-176072, a predetermined high frequency component of a video signal obtained by photographing a subject is focused. Discretely extracted as voltage,
Focusing is performed by moving the focus lens in the optical axis direction by this focus voltage, and when the level of the above-mentioned focus voltage sharply drops to a predetermined level or more, thereafter, the focus voltage extracted several times. There is known a method in which the focus voltage is ignored and the focusing is continued, and a rapid change in the focus voltage is determined to be caused by a disturbance.

Further, as disclosed in Japanese Examined Patent Publication No. 3-21892, in automatic focus detection of a photographing lens by a hill climbing method, the contrast signal is measured while moving the photographing lens along its optical axis. When detecting the maximum value of the intensity of the contrast signal, when the change in the measured intensity of the contrast signal changes from the increasing direction to the decreasing direction, the peak value between the increase and the decrease is displayed. within a predetermined distance, obtains a contrast signal of the peak value greater than, when the contrast signal greater than the peak value is not required, set the photographing lens to a position indicating the peak value, whereas, the pin <br/> When a contrast signal with a value larger than the peak value is obtained, the photographic lens is moved from that position according to the hill climbing servo system. It is to ignore the sub-peak value of the contrast values in the focus detecting operation is to move the imaging lens to the true maximum contrast positions.

[0004]

However, Japanese Patent Laid-Open No. Sho 63-63
According to the technique disclosed in Japanese Patent No. 176072, when the focus voltage level suddenly drops to a predetermined level or higher during the movement of the focus lens in the focus direction, it is determined that it is a rapid change due to disturbance, and the number after that. Since the focus voltage that has been taken out over a period of time is ignored and focusing is continued, it is impossible to determine whether the sudden change in the focus voltage is due to disturbance or other factors, and stable focus detection is possible. could not.

Further, in the method disclosed in Japanese Patent Publication No. 3-21892, when a hill-climbing servo system is applied and one contrast position is found, the contrast characteristics before and after that are measured, and the position is a sub-peak. However, since the peak of the contrast does not occur at the true focus position, it may not be possible to confirm whether it is a sub-peak or a true peak, which may lead to false recognition of the in-focus point. .

The hill climbing servo system will be described in detail. For example, in the case of using a line image sensor, the relationship between the position of the stage and the contrast value under the condition that the image of the sample is always projected on the line sensor. As shown in FIG. 3, a contrast characteristic having a peak contrast value at the focus position with respect to the stage position can be obtained, and focus detection can be performed without any problem. However, as shown in FIG. 4A, when the observation object is scattered and there is nothing in the other area (for example, when the background is apt to become dark, such as fluorescence observation or dark field observation). If the positional relationship between the sample image a at the in-focus point and the line image sensor b is as shown in the figure, since the sample image a is not projected at the in-focus point on the line image sensor b, the contrast value is zero. Become. However, when the stage is moved in the optical axis direction while maintaining this positional relationship, the sample images a scattered as shown in FIG.
Is a defocusing characteristic that appears to spread greatly,
When moving the stage to a location, specimen image a is the line
When the image is projected on the image sensor b and the contrast comes to appear again, after that, when the stage is further moved in the direction away from the focus, after that, when the sample image a is normally projected on the line image sensor b. As with, the focus characteristics will be shown.

In this case, as for the relationship between the stage position and the contrast value, as shown in FIG. 5, when the stage is moved toward the focus position, the contrast value gradually increases, but the sample image a from the line image sensor b. At the position where the projection of disappears, the contrast value suddenly decreases, and then
The sample image a is defocused so that the line image sensor b
When projected on, the contrast value rises again,
Further, as the stage moves away from the focus, the contrast decreases.

However, according to such a contrast characteristic, the actual focal point is located in the section c where no contrast appears. Therefore, if the hill-climbing servo method is applied to such a contrast characteristic, it is true. Since the peak of the contrast value does not occur at the focus position, it is not possible to confirm whether it is a sub-peak or a true peak, which easily leads to erroneous recognition of the in-focus point, and stable focus detection cannot be performed.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a microscope capable of always realizing stable focus adjustment without erroneously recognizing the in-focus position and an automatic focus detection method thereof. .

[0010]

Means for Solving the Problems The microscope of the present invention, stearyl
Objective optical system for observing a sample on a screen, and the objective optical system
Image sensor that photoelectrically converts the optical image formed by
And a photoelectric conversion of the optical image by the image sensor.
The contrast value is generated while the contrast value is generated.
And a CPU that detects the in-focus point by evaluating
In the microscope described above, the CPU controls the light of the objective optical system.
The contrast value increases along the axis in the direction of increasing the contrast.
While moving the stage or objective optical system
The point where the strike value drops sharply is detected, and the contrast value
When a point that drops sharply is detected, the range within the specified distance
Detects the point where the contrast value suddenly recovers due to the movement of
Based on the detected change points of the contrast value
It is characterized by detecting the focal point. Further, the manifestation of the present invention
The CPU of the microscope has the stage at the center position of the change point.
Alternatively, the objective optical system is moved. Well
Further, the image sensor of the microscope of the present invention has a line image.
It is characterized by being a di-sensor. In addition, according to the present invention
The microscope's automatic focus detection method observes the sample on the stage
The optical image formed by the objective optical system
When photoelectric conversion is performed to generate the contrast value of the optical image,
In both cases, the focus is evaluated by evaluating the contrast value.
In the automatic focus detection method of a microscope for detecting
The objective optical system along the optical axis of the objective optical system.
While moving in the direction in which the contrast value increases
The point where the contrast value drops sharply is detected and
If a point where the last value drops sharply is detected, the
Contrast value recovers sharply by moving the range of distance
Change the detected contrast value.
The feature is that the focus is detected based on the points.

[0011]

As a result, according to the present invention, the optical image formed by the objective optical system for observing the sample on the stage is photoelectrically converted by an image sensor such as a line image sensor to generate a contrast value of the optical image. been made to detect the focusing point by evaluating the contrast value, firstly, it is moved in the direction in which the contrast value is increased along the stage or the objective optical system to the optical axis of the objective optical system, the stage or When the position where the contrast value sharply decreases due to the movement of the objective optical system means is detected, and when the position where the contrast value sharply decreases is detected, the range of a predetermined distance is further moved to find the position where the contrast value sharply recovers. detecting, when detecting a change in the contrast value in these two points, a change in these detected contrast value
The focus can be detected based on the points. Furthermore, by moving the stage or the objective optical system to the center position of the change point, in the detection of the in-focus point, the observation object is temporarily scattered and the optical image of the observation object is not projected on the image sensor. Even in such a case, the focus position is not erroneously recognized, and the stage or the objective optical system can be moved and controlled to this focus position.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a focus detection device to which the automatic focus detection method of the present invention is applied.

In the figure, reference numeral 1 designates a stage on which a specimen 2 as a sample is placed. And
An objective lens 3 is arranged corresponding to the sample 2 on the stage 1. In this case, the stage 1 is the specimen 2 to be observed.
In order to adjust the focus state of the objective lens 3, the objective lens 3 can be moved up and down in the optical axis direction.

Then, along the optical axis of the objective lens 3,
The prism 4 and the mirror 5 are arranged, the eyepiece lens 6 is arranged via the prism 4, and the imaging lens 7 and the line image sensor 8 are arranged via the mirror 5 to be caught by the objective lens 3. The optical image of the sample 2 is transferred to the line image sensor 8 via the mirror 5 and the imaging lens 7.
And the eyepiece 6 through the prism 4
I am trying to observe more. Here, the line image sensor 8 converts the projected optical image of the sample 2 into an electric signal.

An analog signal processing circuit 9 is connected to the line image sensor 8, and a contrast calculating section 10 is connected to the analog signal processing circuit 9. The analog signal processing circuit 9 performs a predetermined process such as A / D conversion on the image signal converted into an electric signal by the line image sensor 8 and sends the image signal to the contrast calculation section 10. The contrast calculation section 10 processes the signal sent from the analog signal processing circuit 9 according to a predetermined contrast evaluation function, and gives the result to the CPU 11.

The CPU 11 fetches information such as the calculation result from the contrast calculation section 10 and the magnification from the objective lens 3, obtains the movement amount of the stage 1 from the information, and outputs the result to the stage drive circuit 12. ing. Then, this stage drive circuit 12 is
The stage 1 is driven based on the information sent from U11 to adjust the focus state.

The focus detection by the focus detecting device thus constructed will be briefly described. Now, when the sample 2 is placed on the stage 1, the optical image of the sample 2 is converted into the objective lens 3.
It is captured by the line image sensor 8 via the mirror 5 and the imaging lens 7.

Then, by the line image sensor 8,
The projected optical image of the sample 2 is converted into an electric signal and sent to the contrast calculation unit 10, where it is subjected to calculation processing according to a predetermined contrast evaluation function, and thereafter, information such as magnification from the objective lens 3 is given. Sent to the CPU 11 with
The movement amount of the stage 1 is obtained.

As a result, the stage driving circuit 12 drives the stage 1, and by repeating such an operation, the focus state is automatically adjusted. In this case as well, in the same manner as described above, when the image of the sample 2 is projected by the line image sensor 8 in both focusing and defocusing, the position of the stage 1 and the contrast value are compared. The relationship has a characteristic that it has a peak value only at the focal position as shown in FIG. 3, but in the case where the observation object is scattered, the positional relationship between the sample 2 and the line image sensor 8 at the in-focus point is In the case shown in FIG. 4A, since the sample image a is not projected on the line image sensor 8 at the in-focus point, the calculated contrast value becomes zero. However, when the stage 1 is moved upward or downward, the image of the sample 2 is greatly expanded due to defocusing as shown in FIG. 4B. Therefore, when the stage 1 moves to a certain position, The sample image not projected at the in-focus point is projected on the line image sensor 8, the contrast value rises again, and when the stage 1 is further moved, thereafter, the sample image is normally displayed on the line image sensor 8. As in the case where is projected, the focus characteristic appears, and as a result, the contrast characteristic shown in FIG. 5 is obtained.

Therefore, in the present invention, the flowchart shown in FIG. 2 is executed while repeatedly calculating the contrast value of the sample 2. In this case, in step 201, the stage 1 is moved in the direction in which the contrast value gradually increases,
While searching for the point where the contrast value reaches the peak value by the hill climbing servo system, it is judged in step 202 whether there is a point where the contrast value sharply decreases.

Here, when a point where the contrast value sharply decreases is found, it is confirmed in step 203 that the cause is that the projection of the sample 2 disappears from the light receiving surface of the line image sensor 8, and step In step 204, the position A of the stage 1 at this time is temporarily stored, and then step 2
In step 05, the stage 1 is continuously moved in the same direction as in step 201 within a predetermined distance, and a point where the contrast value reaches the peak value is searched for by the hill climbing servo method. Determine if there is a point to revive.

Here, when a point where the contrast value is rapidly restored is found, it is confirmed in step 207 that the sample 2 has been projected on the line image sensor 8 by defocusing, and in step 208, The position B of the stage 1 at this time is temporarily stored. Then, in step 209, it is predicted that the true focus is in the middle of the positions A and B of these two points, and in step 210, the stage 1 is moved to the intermediate position, and the focusing process ends.

Whether or not there is a sudden change in the contrast value is judged by judging whether or not the amount of change in the contrast value exceeds a certain fixed value. At this time, if it is also determined whether or not the contrast value is within a preset value range, the accuracy is further enhanced.

Therefore, according to such an embodiment, the optical image formed by the objective lens 3 for observing the sample 2 on the stage 1 is projected on the line image sensor 3 and photoelectrically converted, and further, the analog signal processing circuit. 9. The focus value is detected by evaluating the contrast value while generating the contrast value of the optical image through the contrast calculation section 10. First, the stage 1 is contrasted along the optical axis of the objective lens 3. Move in the direction of increasing value,
The position where the contrast value sharply decreases by this movement is detected, and when the position where the contrast value sharply decreases is detected, the range of a predetermined distance is further moved to detect the position where the contrast value sharply recovers. When a change in the contrast value is detected at these two points, the stage 1 is moved to the center position of these change points. For example, since the observation object of the sample 2 is scattered, the sample is placed on the image sensor 3. Even when an image is not projected, the focus position is not erroneously recognized, the stage 1 can be moved and controlled to this focus position, and stable focus adjustment can always be realized.

The present invention is not limited to the above-mentioned embodiments, and can be carried out by appropriately modifying it within the scope of the invention.
For example, in the above-described embodiment, the stage 1 is moved to change the contrast value, but the objective lens 3 may be moved.

[0026]

As described above, according to the present invention, even if the observation object is scattered and the optical image of the observation object is not projected on the image sensor, the in-focus position is erroneously recognized. It is possible to always realize stable focus adjustment.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a focus detection apparatus to which an embodiment of the present invention is applied.

FIG. 2 is a flowchart for explaining an example.

FIG. 3 is a diagram showing a relationship between a stage position and a contrast value when a sample image is projected on a line sensor.

FIG. 4 is a diagram for explaining a state where a sample image is not projected on a line sensor when the sample is scattered.

FIG. 5 is a diagram showing a relationship between a stage position and a contrast value when the sample is scattered and the sample image is not projected on the line sensor.

[Explanation of symbols]

1 ... stage, 2 ... specimen, 3 ... Objective lens, 4 ... Prism, 5 ... Mirror, 6 ... eyepiece, 7 ... Imaging lens, 8 ... Line image sensor, 9 ... Analog signal processing circuit, 10 ... Contrast calculation unit, 11 ... CPU, 12 ... Stage drive circuit.

Claims (4)

(57) [Claims] 1. An objective optical system for observing a sample on a stage
When, An image that photoelectrically converts an optical image formed by the objective optical system.
Image sensor, The photoelectric conversion is performed by the image sensor to control the optical image.
Generates the last value and evaluates the contrast value
And a CPU that detects the in-focus point by
In the microscope, The CPU is The contrast value increases along the optical axis of the objective optical system.
Move the stage or objective optical system in the ascending direction
While detecting the point where the contrast value drops sharply
Then If it detects a point where the contrast value drops sharply,
The contrast value suddenly increases due to the movement of a predetermined distance
Detecting the point to revive, Focusing is performed based on these detected change points of the contrast value.
A microscope characterized by detecting points. 2. The CPU is At the center position of the change point, the stage or the objective optical system
The microscope according to claim 1, wherein the microscope is moved. 3. The image sensor is a line image
A microscope according to claim 1 or 2, which is a sensor.
Microscope. 4. An objective optical system for observing a sample on a stage
The optical image formed by the photoelectric conversion
The contrast value of the optical image is generated and
Microscope that detects the focal point by evaluating the trust value
In the automatic focus detection method of the mirror, The stage or the objective optical system on the optical axis of the objective optical system
Do not move in the direction of increasing the contrast value along
However, the point where the contrast value sharply decreases is detected, If it detects a point where the contrast value drops sharply,
The contrast value suddenly increases due to the movement of a predetermined distance
Detecting the point to revive, Focusing is performed based on these detected change points of the contrast value.
Automatic focus detection method of microscope characterized by detecting points
Law.