JP3403447B2 - microscope - Google Patents

Description

Detailed Description of the Invention

The present invention relates to an automatic system using an image sensor.
The present invention relates to a microscope equipped with a focusing device .

[0002]

2. Description of the Related Art Conventionally, as an automatic focusing device for a microscope,
The optical image of the subject obtained through the optical system is input to the image sensor, the sum of the differences between the adjacent pixel outputs of the subject image is calculated from the electrical signal output from the image sensor, and the high-frequency component of the electrical signal is calculated. There is a method of determining a focus position by a so-called hill-climbing method from a signal obtained by passing a voltage through a bandpass filter, that is, a contrast signal.

Here, the hill-climbing method is to move the focus lens or the sample stage in an arbitrary direction first, compare the intensities of the contrast signals before and after the movement, and if the intensity of the contrast signals after the movement is increased, the same direction is used. If the intensity of the contrast signal decreases after the movement, the focus lens or the sample stage is moved to the position where the contrast is maximized by moving in the opposite direction so that the position of the focus lens or the sample stage coincides with the in-focus position. Is.

[0004]

However, when the difference between the adjacent pixel outputs of the image sensor is calculated while moving the focus lens or the sample stage to the in-focus state and the in-focus operation is performed using the difference as a contrast signal, the image sensor If the output is saturated, shorten the accumulation time of the image sensor to obtain an appropriate output, but if you take the difference between the electrical signals at the adjacent pixel outputs of the image sensor before the accumulation time is shortened, The difference becomes smaller than that.

The stronger the difference between the electric signals, that is, the stronger the contrast signal, the closer to the in-focus state. However, if the accumulation time of the image sensor is shortened as described above, the contrast signal becomes weak and the apparent in-focus state is obtained. It falls into the state of moving away from the direction toward. In such a state, the system determines that the state before changing the accumulation time is the point with the maximum contrast intensity, that is, the focus position, and moves the focus lens or the sample stage to a position different from the original focus position. It will malfunction.

When the focus lens or the sample stage is moved from the in-focus state and the electric signal of the image sensor is small, the accumulation time of the image sensor is lengthened so as to obtain an appropriate output. The contrast signal becomes stronger than before changing the accumulation time,
If the contrast signal does not become strong earlier than this, this position is determined to be in focus, and the focus lens or the sample stage is moved to that position, causing a malfunction.

The present invention has been made in view of the above problems, and even if the storage time of the image sensor is changed, the difference between the electric signals, that is, the contrast signal does not change.
Self it is possible to prevent malfunction due to the deviation of the focus position
An object of the present invention is to provide a microscope provided with a moving focusing device .

[0008]

In order to achieve the above object, the present invention inputs an optical image of a subject obtained through an optical system into an image sensor, and combines the optical image based on an electric signal output from the image sensor. Automatic focusing system that calculates the degree of focus and drives the objective lens or sample stage by the hill climbing servo system according to the calculation result to perform focusing.
In the microscope equipped with an apparatus , the automatic focusing device includes a calculating unit that digitally converts an electric signal from the image sensor to calculate a contrast, and an electric signal from the image sensor has an input voltage range of an A / D converter. And a level determining means for determining whether or not the electrical signal from the image sensor is inappropriate for the input voltage range of the A / D converter. a setting changing means for setting change to the correction level the charge accumulation time of the image sensor to be, the
The charge accumulation time changed by the setting change means
As a meter, the accumulation time of the image sensor
When the setting is changed to k times
1 / k times the calculation result of the contrast calculated from the sum
And correction means for correcting the contrast.
It

[0009]

According to the microscope having such a structure, even if the charge accumulation time of the image sensor is set in the automatic focusing device, the automatic focusing device has a function of correcting the contrast calculation result based on the accumulation time. Even if the storage time of the image sensor is increased by k during operation, the result of contrast calculation is multiplied by 1 / k, so accurate focusing operation can be performed without erroneously recognizing the peak of the contrast value. it can.

[0010]

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 system configuration example of an automatic focusing device for a microscope according to the present invention. As shown in FIG. 1, the optical system of the microscope of the present embodiment includes a specimen stage 2 capable of vertically moving an object 1 which is an observation specimen, and may be adjusted depending on whether the epi-illumination light source or the transmission light source (not shown) is displaced. The obtained light flux from the subject 1 passes through the objective lens 3, a part of the light flux is imaged on the eyepiece lens L, and the other light flux is imaged by the imaging objective lens 4 and projected on the solid-state image sensor (CCD sensor) 5. To be done.

On the other hand, the CCD sensor 5 converts the projected light image into an image signal having a voltage corresponding to the amount of incident light and the charge storage time, and this image signal is input to the analog processing section 6. The analog processing unit 6 amplifies the analog signal, performs analog processing such as filter processing, and inputs the analog signal to the A / D converter 7. The A / D converter 7 converts an analog signal into a digital signal, and the digital signal is sent to the arithmetic circuit 8.

The arithmetic circuit 8 executes an arithmetic operation according to a predetermined evaluation function indicating the degree of focus such as contrast, and C
The peak value of the output of the CD sensor 5 is obtained, and the result is CP
It is sent to U9.

The CPU 9 confirms the focus state based on the focus level calculated by the arithmetic circuit 8, and outputs a stage drive signal to the stage drive circuit 10 when the focus state is out of focus, and the sample stage 2 The focus is adjusted by moving up and down.

As shown in FIG. 2, the CPU 9 also takes in the output peak value of the CCD sensor 5 obtained by the arithmetic circuit 8 so that the electric signal from the CCD sensor 5 is in the input voltage range of the A / D converter 7. With respect to the timing generator 11 and a timing generator 11 that calculates an appropriate charge accumulation time when the determination means 9-1 determines that the level is an inappropriate level. Against C
Storage time setting changing means 9-2 for changing the setting of the charge storage time of the CD sensor 5, and this storage time setting changing means 9-2.
When the charge storage time of the CCD sensor 5 is changed to k times the previous time, the correction result 9-3 is provided to correct the calculation result of the arithmetic circuit 8 to the focus level which is 1 / k times. In this case, the timing generator 11 outputs a drive pulse to the CCD sensor 5 according to the set conditions.

Next, the operation of the automatic focusing device for a microscope constructed as described above will be described. Now, assuming that the CPU 9 confirms the focus state based on the focus level calculated by the arithmetic circuit 8, and the stage drive signal is being output to the stage drive circuit 10 by the hill climbing method, the sample stage 2 is moved up and down by the stage drive circuit 10 to adjust the focus. At this time, as the subject image projected on the CCD sensor 5 approaches the in-focus state, the contrast of the subject image becomes higher and the difference in lightness and darkness becomes larger, so the output peak level of the CCD sensor 5 also becomes larger.

Such an electric signal is input from the CCD sensor 5 to the analog processing circuit 6 and subjected to predetermined processing to obtain A
After being converted into a digital signal by the / D converter 7, when it is sent to the arithmetic circuit 8, the arithmetic circuit 8 performs arithmetic according to a predetermined evaluation function indicating the degree of focus such as contrast and the CCD sensor 5 Is calculated and the result is sent to the CPU 9.

When the output peak value of the CCD sensor 5 is fetched by the CPU 9, first, the judgment means 9-1 causes the CCD to operate.
It is determined whether or not the electric signal from the sensor 5 is at an appropriate level for the input voltage range of the A / D converter 7, and if it is determined to be an inappropriate level, the accumulation time setting changing means 9-2. Then, an appropriate charge storage time is calculated, and the charge storage time of the CCD sensor 5 is changed for the timing generator 11.

In this case, since the arithmetic circuit 8 calculates the sum of the differences between the outputs of the adjacent pixels as the focus degree (contrast), the accumulation time becomes 1 due to the increase of the contrast, for example.
When the setting is changed to / 2, the result calculated by the arithmetic circuit 8 decreases even though the contrast increases.

The phenomenon at this time will be described with reference to FIG. FIG. 3A shows the output of the CCD sensor 5 when a certain storage time is T (sec), and FIG. 3B shows the output when T / 2 (sec).

In this way, the same subject image is captured by the CCD sensor 5
Even if it is captured by the CCD sensor 5
Since the level of the output image signal will change, the result of the sum of the differences between the outputs of adjacent pixels is also shown in FIG.
(A) is larger than FIG. 3 (b) and becomes twice as large.

However, when the charge accumulation time of the CCD sensor 5 is changed to 1 / k times (k> 1) which is shorter than the previous time by the accumulation time setting changing means 9-2 of the CPU 9, the set accumulation time is set. When the total sum of the differences between the adjacent pixel outputs of the image signals obtained by
When the calculation result obtained by the correction means 9-3 is multiplied by k, the focus level is set, and conversely, when the setting is changed to k times (k> 1) longer than the previous time, it is obtained by the set accumulation time. When the arithmetic circuit 8 obtains the sum of the differences between the output of adjacent pixels of the obtained image signal, the correction means 9-3 corrects the calculation result multiplied by 1 / k as the focus level.

Therefore, when the setting of the accumulation time is changed, the sum of the differences between the adjacent pixel outputs calculated by the arithmetic circuit 8 is corrected by the change of the accumulation time. The contrast calculated in the search process does not change abruptly, a smooth contrast curve can be obtained, and stable focus adjustment becomes possible.

In the above embodiment, the focus adjustment is performed by moving the sample stage 2 up and down, but when the objective lens is moved up and down using the infinity objective optical system, the focus adjustment is performed. However, by adopting the same correction as described above, the same effect as that of the above-described embodiment can be obtained.

Further, in the above embodiment, the difference sum of adjacent pixel outputs is calculated as the contrast calculation method. However, when the Nth sum of the difference between the adjacent pixel outputs is used as the contrast calculation method. Accumulation time is k times the previous time (k
By correcting the contrast obtained by changing to> 0) by 1 / k ^N times, it is possible to obtain the same function and effect as in the above-described embodiment and to enhance the contrast.
However, it is possible to obtain effects such as correction.
Wear.

Further, in the above-mentioned embodiment, as the contrast calculation method, the correction is made by using the accumulation time whose setting is changed with respect to the sum of the differences of the adjacent pixel outputs as a parameter, but the correction other than the accumulation time may be repeated. In such a case, first, a correction is performed according to the accumulation time of which the setting is changed for each of the differences between the adjacent pixel outputs, and then a plurality of corrections are performed by performing other corrections. it can.

[0026]

As described above, according to the present invention, in the case of searching the in-focus point by the hill climbing search method, the contrast calculation result is not affected even if the accumulation time of the image sensor is changed midway. Since it can be changed smoothly, it is possible to provide a microscope equipped with an automatic focusing device capable of performing stable focus adjustment.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of an automatic focusing device for a microscope according to the present invention.

FIG. 2 is a functional block diagram of the CPU according to the embodiment.

FIG. 3 is a diagram showing an image signal showing a relationship between an accumulation time and an output of a CCD sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Subject, 2 ... Sample stage 3 ... Objective lens, 4 ... Imaging lens, 5 ... CCD sensor, 6 ... Analog processing circuit,
7 ... A / D converter, 8 ... Arithmetic circuit, 9 ... CPU, 9-1
... determination means, 9-2 ... accumulation time setting change means, 9-3 ...
Correction means, 10 ... Stage drive circuit, 11 ... Timing generator.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-27154 (JP, A) JP-A-3-20707 (JP, A) JP-A-2-36681 (JP, A) JP-A-5- 34590 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 7/11

Claims (2)

(57) [Claims] 1. An optical image of a subject obtained through an optical system is input to an image sensor, a focusing degree is calculated based on an electric signal output from the image sensor, and a hill-climbing servo system is calculated according to the calculation result. by driving the objective lens or specimen stage by automatic focusing focusing is performed
In a microscope including a device, the automatic focusing device includes a calculating unit that digitally converts an electric signal from the image sensor to calculate a contrast, and an electric signal from the image sensor is an input voltage of an A / D converter. Level determining means for determining whether or not the level is appropriate for the range, and the level determining means determines that the electric signal from the image sensor is not appropriate for the input voltage range of the A / D converter. When it is judged, the setting change means for setting the charge accumulation time of the image sensor to the correction level and the charge accumulation time changed by the setting change means are set.
As a parameter, the storage time of the image sensor is
When the setting is changed to k times, the adjacent pixels are output by the calculation means.
Contrast calculation result obtained from total force is 1 /
Compensation means for compensating the contrast by multiplying by k
A microscope equipped with an automatic focusing device. 2. An optical image of a subject obtained through an optical system.
To the image sensor and output from this image sensor.
The degree of focus is calculated based on the applied electric signal, and the calculation is performed.
Depending on the result, the objective lens or the
Automatic focusing to drive the specimen stage for focusing
In a microscope equipped with a device, the automatic focusing device digitally converts an electric signal from the image sensor.
The difference sum of the Nth power of the difference between adjacent pixels.
The calculation means for calculating the last and the electric signal from the image sensor are input to the A / D converter.
Determine whether the level is appropriate for the output voltage range
Level determining means for determining the level of the electric power from the image sensor by the level determining means.
The air signal is not appropriate for the input voltage range of the A / D converter.
If it is determined that there is a charge accumulation time of the image sensor
Correction level by multiplying the standard accumulation time by k
To the setting means for changing the setting, and the setting means to change the setting
Contra calculated from the sum of the Nth powers of adjacent pixel outputs
Stroke calculation result is multiplied by 1 / k ^N to correct contrast
Automatic focusing, characterized by comprising a correction means
A microscope equipped with a device.