JPH07218840A - Microscope provided with video camera - Google Patents

Abstract

PURPOSE:To operate the automatic gain control function of a video camera to make a picture easy to see and to automatically position the sample stage to the focus even with the video signal taken in this state. CONSTITUTION:A video camera 2 has the automatic gain control function turned on to pick up an optical image. The difference between adjacent data in the same scanning line of data stored in a data storage part 8 is raised to fourth power, and results are added with respect to data of one frame to calculate an evaluation value, and a contrast function is obtained. The contrast function is smoothed and differentiated, and the Z position range between the Z position for a maximum value of the differential value and that for a minimum value is calculated as the effective range where the focus exists, and a maximum value of the contrast function within the focus effective range indicates the focus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical microscope, and more particularly to an optical microscope equipped with a video camera and having an autofocus function for automatically positioning a sample stage at a focal point based on a video signal captured by the video camera. It is about.

[0002]

2. Description of the Related Art In order to realize an autofocus function by using a video signal picked up by a video camera, the video signal is fetched as data at each Z position in the Z direction in the direction toward and away from the objective mirror, and the same scanning is performed. A plurality of differences between adjacent data in a line are raised to a power, a plurality of differences between adjacent data in a line are raised to a power, and a value obtained by adding the differences for one frame is used as an evaluation value. A method has been adopted in which a contrast function is created using the evaluation value as a function for the Z position of the sample stage, and the sample stage is positioned at a position where the contrast function has a maximum value.

Some video cameras are provided with an auto gain control function, but a video signal used when the auto gain control is off is used as a video signal for the auto focus function. The video signal is at a signal level between the black level and the white level, but with auto gain control, a signal whose level is lower than the lower limit of the threshold is amplified to an appropriate level,
On the contrary, the gain is automatically adjusted so that a signal having a level higher than the upper limit of the threshold value is lowered to an appropriate level. However, when a video signal that is captured with auto gain control turned on is used as the video signal that is the basis for calculating the evaluation value for creating the contrast function, the evaluation value that should be originally small and is far from the focus point. However, a large evaluation value is obtained as a result of the video signal being automatically amplified by the auto gain control, and it becomes difficult for the conventional auto focus function to find the in-focus point by using the contrast function.

[0004]

However, when observing the sample with the auto gain control turned off, the sample of extremely low reflectance and the sample of extremely low transmittance show that the gain of the video signal is too low. Even if it is not imaged or is displayed, it becomes difficult to see compared to the image with the auto gain control turned on. Similarly, in a sample having extremely high reflectance or a sample having extremely high transmittance, the video signal exceeds the upper limit of the threshold value, and it becomes impossible to visualize.

Therefore, according to the present invention, the automatic gain control function of the video camera is operated to make the image easy to see, and the sample stage can be automatically positioned at the in-focus point even if the video signal taken in that state is used. The purpose is to do.

[0006]

FIG. 1 shows the present invention. The video camera 2 has an auto gain control function,
An optical image incident from the objective mirror is captured. Sample stage 2
Reference numeral 2 denotes a moving mechanism that moves in the Z direction, which is a direction toward and away from the objective mirror direction, and the stage drive control unit 4 controls the movement of the sample stage 22 in the Z direction. Data acquisition unit 6
Captures the video signal from the video camera 2 captured in the auto gain control state as a digital signal. The video signal for one frame captured through the data capturing unit 6 at each Z position of the sample stage 22 is stored in the data storage unit 8 as data. Evaluation value calculation unit 10
For the data stored in the data storage unit 8, the difference between adjacent data in the same scan line is raised to the power of a plurality, and the difference is added to the data of one frame to obtain an evaluation value. The contrast function storage unit 12 stores the evaluation value for the Z position of the sample stage 22 calculated by the evaluation value calculation unit 10 as a contrast function. Focusing effective range calculation unit 1
4, after smoothing the contrast function, differentiating, calculating the Z position range between the Z position showing the maximum value and the Z position showing the minimum value of the differential value as the effective range in which the in-focus point exists,
The in-focus point calculation unit 16 sets the maximum value of the contrast function existing in the in-focus point effective range calculated by the in-focus point effective range calculation unit 14 as an in-focus point, and the stage drive control unit 4 sets the sample stage at the in-focus point. To move.

[0007]

FIG. 2 is a side view showing the appearance of a microscope to which the present invention is applied. A sample stage 22 is provided on the body 20 of the microscope, and the sample stage 22 is moved in the Z-axis direction by a Z-direction moving mechanism 24 provided on the body 20. The Z direction is a direction toward and away from the objective mirror 28 along the optical axis incident on the objective mirror 28. A light source is provided in the body portion 20, and in the case of a transmission microscope, a measurement light beam 26 from the light source passes through the sample mounted on the sample stage 22 from below the sample stage 22 and enters the objective mirror 28. However, in the case of a reflection type microscope, the measurement light beam is irradiated onto the sample from the objective mirror 28, and the reflected light enters the objective mirror 28. A trinocular tube 30 is arranged above the body portion 20, and the light incident on the objective mirror 28 is reflected by the video camera 2 and the eyepiece 34.
Incident on.

In FIG. 3, it is provided in the body portion 20 of FIG.
3 shows a control system that realizes the autofocus function of the present invention. The video camera operates with the auto gain control function turned on. A video buffer 42 is provided for amplifying the video signal 40 from the video camera, and the amplified video signal is converted into a digital signal and C
An A / D converter 44 is provided to take in the internal bus 46 of the PU. A sync signal separation circuit 48 is provided to separate the sync signal from the video signal 40.
The internal bus 46 is further provided with a DMA (direct memory
The access) controller 50 is connected to a static RAM 52 for temporary storage, and the DMA controller 50 uses the sync signal separated by the sync signal separation circuit 48 to perform A / D conversion in the A / D converter 44. In addition to the control, the video signal converted into a digital signal by the A / D converter 44 is transferred to the RAM 52 as data and stored therein. The internal bus 46 is further connected with a CPU 54 for controlling the overall operation, a ROM 56 for storing an operation program, and a driver 60 for operating a sample stage motor 58 for driving the sample stage moving mechanism 24. .

1 and 3, the stage drive control unit 4 in FIG. 1 corresponds to the CPU 54, the ROM 56 and the driver 60, and the data acquisition unit 6 is the video buffer 42, the A / D converter 44, and the synchronization. The data storage unit 8 is realized by the RAM 50 corresponding to the signal separation circuit 48 and the DMA controller 50. Evaluation value calculation unit 1
0, in-focus effective range calculator 14, and in-focus calculator 16
Are realized by the CPU 54, the ROM 56, and the RAM 52, and the contrast function storage unit 12 is realized by the RAM 52.

Next, the operation of this embodiment will be described.
First, a procedure from A / D conversion of a video signal to storage in the data storage unit 8 and calculation of an evaluation value from the stored one-frame data will be described with reference to FIG. First, the video signal of one frame is shown in (B). From the video signal of this one frame, the DMA controller 50
Recognizes the sync signal using, and captures the video signal as a digital signal via the A / D converter 44,
It is stored on the AM 52 as shown in (C). Then, the difference between adjacent data in the same scan line is raised to the power of 1 and
Add the data for the entire frame. That is the evaluation value at the Z position of the sample stage. Assuming that the data difference is raised to the fourth power as an example of the multiple power of the difference between adjacent data, the evaluation value is expressed by the following expression (1).

[0011]

[Equation 1]

Next, the operation of creating the contrast function while moving the sample stage in the Z direction and positioning the sample stage at the focal point will be described with reference to FIGS. 5 and 6. Figure 5
As shown in FIG.
Sampling of data and calculation of the evaluation value described above are performed. This operation is performed at each Z position while moving the sample stage upward in the Z direction, and is repeated up to the highest position of the sample stage. When this operation is completed, the contrast function shown in FIG. 6A with the evaluation value on the vertical axis is obtained for the Z position on the horizontal axis. The Z position of the peak M at the bottom of FIG. 6 (A) is the in-focus point, but at the upper and lower Z positions away from the in-focus point, the gain of the video signal is automatically amplified by the automatic gain control, resulting in the in-focus point. The contrast function has a large evaluation value above and below the focus. From such a contrast function, the in-focus point cannot be obtained by the conventional process of setting the position of the maximum evaluation value as the in-focus point.

In the embodiment, the following data processing is performed in order to obtain the Z position of the peak M of this in-focus point. First, the evaluation value group of the contrast function is duplicated on the RAM 52,
Integrate one evaluation value group. The integration results in a smoothed contrast function as shown in FIG. 6 (B).
Next, when the smoothed contrast function is differentiated, a function as shown in FIG. 6C is obtained. The Z position range Zmax to Zmin between the Z position Zmax showing the maximum value of this differential function (C) and the Z position Zmin showing the minimum value is obtained as the effective range in which the in-focus point exists.

Next, the other contrast function before smoothing remaining in the RAM 52 is compared with the effective focus range Zmax to Zmin obtained in FIG. 6C, and the effective focus range Zmax to Zmin is within the range. The maximum value of the contrast function existing in is the evaluation value at the in-focus point. The autofocus operation is completed by moving the sample stage to the Z position that shows the evaluation value at this in-focus point.

[0015]

According to the present invention, a contrast function is created by calculating an evaluation value at each Z position from a video signal picked up with the automatic gain control of the video camera turned on, and the focusing point is directly determined from the contrast function. Instead of obtaining it, it is first smoothed and then differentiated to determine the focus effective range of the Z position where the focus exists, and then the maximum value of the contrast function within that effective range is made the focus. Therefore, it is possible to make the image of the video signal easy to see by the auto gain control and realize the auto focus function.

[Brief description of drawings]

FIG. 1 is a block diagram showing the present invention.

FIG. 2 is an external side view of an embodiment.

FIG. 3 is a block diagram showing a control system of an embodiment.

4A and 4B are diagrams showing a processing procedure from data acquisition to calculation of an evaluation value, in which FIG. 4A is a flow chart and FIG.
FIG. 3C is a diagram showing a frame video signal, and FIG. 3C is a diagram showing a 1-frame video signal digitized and stored in the RAM.

FIG. 5 is a flowchart showing an autofocus function in the same embodiment.

6A and 6B are diagrams showing a process of finding a focal point in the embodiment, where FIG. 6A is a diagram showing a contrast function, FIG. 6B is a diagram showing a contrast function after smoothing, and FIG. It is a figure which shows a contrast function.

[Explanation of symbols]

 2 video camera 4 stage drive control unit 6 data acquisition unit 8 data storage unit 10 evaluation value calculation unit 12 contrast function storage unit 14 focused focus effective range calculation unit 16 focused focus calculation unit

Claims (1)

[Claims] 1. A video camera having an automatic gain control function for picking up an optical image incident from an objective mirror, a sample stage provided with a moving mechanism for moving in the Z direction that approaches and moves away from the objective mirror, and a sample stage. Via the stage drive control unit that controls the movement in the Z direction, the data capture unit that captures the video signal from the video camera captured in the auto gain control state as a digital signal, and the data capture unit at each Z position of the sample stage. For a data storage unit that stores the captured video signal for one frame as data, and for the data stored in the data storage unit, multiply the difference between adjacent data in the same scan line, The evaluation value calculation unit that adds up the evaluation value and the sample value calculated by the evaluation value calculation unit Between the Z position showing the maximum value and the Z position showing the minimum value of the contrast function, after the contrast function is smoothed and differentiated after the contrast function is smoothed. Of the Z position range as the effective range in which the in-focus point exists, and the maximum value of the contrast function existing in the effective range of the in-focus point is set as the in-focus point, and the focus is set to the stage drive control section. And a focusing point calculation unit that moves the sample stage.