JP2014021254A - Method and device for focus adjustment in digital microscope provided with zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve high accuracy in focus adjustment by a stepping motor in a digital microscope provided with a zoom lens.SOLUTION: In a digital microscope for zooming by use of a stepping motor 4, a Linnik-type interference band generator is positioned on the incident side of the zoom lens system 11. A focus adjustment during a zooming operation is made based on light-dark contrast information of an interference band generated by the Linnik-type interference band generator, thereby enabling the control of the stepping motor 4 with resolution in which one pulse is 0.36° or less. Thus, the focus adjustment can be made with high accuracy.

Description

  The present invention relates to a focus adjustment method and apparatus for a CCD camera or a CMOS camera having a zoom lens.

A digital microscope is known as an image processing apparatus for photographing a subject and processing the photographed image.
This digital microscope is an apparatus in which a zoom lens, a camera, an illumination system, an image processing controller, and an image display unit are integrated, and a series of operations such as photographing a subject and image processing thereof can be performed with this single apparatus. it can.

  In this device, the lens is moved up and down with a stepping motor to focus on the subject (Patent Document 1: Japanese Patent Laid-Open No. 2005-338255), or the lens is moved upward or downward by a predetermined amount of movement. Multi-focus processing that moves stepwise and synthesizes the images captured in each step to create an image that is in focus throughout the image regardless of the unevenness of the subject (Patent Document 2: JP 2004-194075 A) It can be performed.

  However, since the stepping motor is used for the vertical movement of the zoom lens, the minimum resolution of the moving amount is determined by the specification of the stepping motor, and at present, the zoom lens can only operate with a resolution of a rotation angle of 0.36 ° per pulse. For this reason, autofocus operations and multifocus processing at resolutions below this cannot be performed electrically, and must be performed manually. However, in the case of manual operation, there is a problem that it takes time to work and there are variations in work by the worker, so that the efficiency is very low and the accuracy is not good.

  Another means of operating at a resolution with a rotation angle of less than 0.36 ° per pulse is a technique for micro-stepping the stepping motor, but this adjusts the value of the current flowing through the stepping motor to reduce the minimum resolution to 0.36 °. It is a technology that divides / 20 to 1/250 and operates.

  However, this is a technology that holds the motor rotor by adjusting the current value at an arbitrary position between the fixed points of the motor rotor arranged at a pitch of 0.36 °. Since the current value does not become constant and is held in the middle of the fixed point, the motor rotor may move due to the influence of vibration at the time of stopping, etc., and accurate position fixing cannot be performed, and the number of input pulses and stepping Deviation occurred in the actual rotation angle of the motor, and it was difficult to control with high accuracy.

There is also a technology that uses a linear encoder to read the moving position, but it requires a circuit that feedback-controls the stepping motor by reading the signal of the linear encoder. Since a control circuit and software are required, the system becomes complicated.

  Therefore, there is a limit for improving the accuracy of the autofocus operation and multifocus processing in this apparatus for the reasons described above.

JP 2005-338255 A JP 2004-194075 A Japanese Patent Laid-Open No. 9-268637 Japanese Utility Model Publication No. 5-43006

  The object of the present invention is to control the stepping motor with a resolution less than the minimum resolution (1 pulse 0.36 °) in the specification of the zoom adjustment stepping motor by utilizing the change in contrast due to the contrast of light interference fringes. This is to improve the accuracy of autofocus operation and multifocus processing.

  In order to achieve the above object, according to the first aspect of the present invention, in a focus adjustment method in a digital microscope using a zoom lens, a linique interference fringe generator on the light incident side of the zoom lens system on the light incident side. And adjusting the focus during zooming operation based on the contrast information of the bright and dark interference fringes generated by this linique interference fringe generator, so that the stepping data can be obtained with a resolution of 0.36 ° or less per pulse. It is something to control.

  Furthermore, in the invention described in claim 2, a CCD camera or a CMOS camera is connected to an interference zoom lens system in which the imaging system of the linique type interference fringe generator is a zoom lens in the focus adjustment device in the digital microscope. And an illumination system that illuminates the subject, performs autofocus operation when photographing the subject, performs multifocus processing using the photographed image, and records the processed image and each of them An image processing apparatus including a display unit for displaying an image, wherein the interference zoom lens system is fixed to a stage unit movable in a vertical direction, and the interference zoom lens system is moved in a vertical direction to focus. The linique type interference fringe generator generates the focus adjustment during the zooming operation. In addition, the present invention is characterized in that a focus control means is provided which is based on contrast information on the brightness and darkness of the interference fringes.

  Furthermore, in the invention described in claim 3, in the focus adjustment device in the digital microscope described in claim 2, the optical path is opened and closed on the optical path of the reference light causing the interference in the interference zoom lens system. An optical path blocking means is provided so that an image without interference fringes can be generated by closing the optical path of the reference light, and the CCD camera or the CMOS camera can be used to capture the image.

  Further, in the invention described in claim 4, in the focus adjustment device in the digital microscope described in claim 2, the stage unit movable in the vertical direction uses a structure that can be manually moved up and down, and a stepping motor is used. The stepping motor can be controlled by a stepping motor control unit, and if necessary, the electric vertical movement structure can be removed and manual zooming can be performed. It is configured so that it can be operated.

  According to a fifth aspect of the present invention, in the focus adjustment apparatus in the digital microscope according to the second aspect, the stepping motor drive control uses a change in contrast of light and darkness of interference fringes in addition to the pulse drive control. It is configured to be controllable.

  According to the present invention, an inexpensive interference zoom lens can be configured by modifying an existing zoom lens, and the actual movement amount of microstepping is set to λ / It became possible to control with a value of 2, and the accuracy of the electric autofocus operation and multifocus processing could be improved dramatically.

Basic configuration diagram of digital microscope Structure diagram of existing zoom lens system Basic configuration of linique interferometer Structure diagram of interference zoom lens system of the present invention Structure diagram of vertical movement stage Explanation of control flow using interference fringes Illustration of the contrast of the interference fringes used in the present invention and this contrast

BEST MODE FOR CARRYING OUT THE INVENTION

  An embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a block diagram showing the basic configuration of a digital microscope. The image processing apparatus 1 is composed of a display unit 2, a light source 3, a stepping motor control unit 4, a camera control unit 5, and an image processing unit 6, and is connected to a CCD camera 10 and a vertically moving stage 12 from each cable (7.8.). The light source 3 and the illuminating unit 13 are connected by the light guide 9, and can perform a series of operations such as photographing, image processing, image storage, and image display.

  FIG. 2 is a diagram showing the structure of an existing zoom lens system. An objective lens 14 is connected to the zoom unit 11, and light 16 from the light source is collected by the illumination unit 13 and guided to the beam splitter 15, and further reflected by the beam splitter 15 to illuminate the subject 18 through the objective lens 14. . The reflected light from the subject 18 can be imaged at an arbitrary optical magnification by the zoom unit, and the image can be taken with a camera.

FIG. 3 is a basic configuration diagram of a linique type interference fringe generator, and this configuration has the same basic structure as that described in Japanese Utility Model Laid-Open No. 5-43006 (Patent Document 4).
In this apparatus, light 16 from a light source is collected by an illumination unit 17 and branched by a beam splitter 22 in two directions, ie, a reference surface 20 side and a subject 18 side, and reflected light from the reference surface 20 and the subject surface 18 are separated. The interference fringes generated by the reflected light can be observed by the imaging detection unit 23.

  FIG. 4 is a structural diagram of an interference zoom lens in which the image forming unit of the linique type interference fringe generator is replaced with a zoom lens. The shutter 24 can be opened and closed by sliding it up and down by a stepping motor 24a. This controls the generation and disappearance of interference fringes, but the optical path opening / closing means on the reference surface 20 side drops the non-reflective film on the front surface of the reference surface 20 in addition to the shutter, reverses the reference surface 20 or It is also possible to prevent the generation of interference fringes by a method of escaping and preventing the generation of reflected light.

  2 to 4, the zoom lens system of FIG. 2 and the linique type interference fringe generator of FIG. 3 include an illumination unit (13, 16), an objective lens (14, 19), and a beam splitter (15, 22). The zoom lens system having both the functions of a normal zoom lens and a linique interference fringe generator can be easily configured by making a minor change to the existing zoom lens system.

  In general, a light wave interference device such as a linique type interference fringe generator has a complicated structure and is expensive, and an improvement plan for simplifying the structure is proposed in Japanese Patent Application Laid-Open No. 9-268637 (Patent Document 3). Then, since it is only necessary to modify the existing device without introducing a new expensive linique interference fringe generator, a zoom lens system having an interference fringe generating function can be configured at low cost. .

  In addition, CCD or CMOS camera sensitivity is also improved due to technological advances for problems such as objective lens aberrations and variations in optical axis adjustment that may cause a decrease in contrast between bright and dark interference fringes. Nowadays, which is improving every day, there is no longer any obstacle to observation when using these imaging devices.

  Even in the apparatus of the present invention, sufficient contrast of bright and dark interference fringes is obtained even with the above-described simple components.

  FIG. 5 is a structural diagram of the stage portion that moves up and down. This stage part is composed of a manual block part 30 that can be manually moved up and down by turning a manual dial 28, and an electric block part 25 that is electrically moved up and down by a combination of a stepping motor 27 and a ball screw 26. It is fixed to 31.

  The manual block unit 30 and the electric block unit 25 are structured to be separable (not shown), and when the electric control is unnecessary, the electric block unit 25 is removed and the zoom lens system 35 is directly connected to the manual block 30. By attaching, it has a structure that allows observation only by manual operation.

  In FIG. 5, a zoom lens system 35 with an interference fringe generator is fixed to the electric block 25 via a lens fixing block 34, and this zoom lens system 35 can be moved up and down by electric control, thereby focusing on the subject 32. Adjustments can be made.

  Here, in this apparatus, since the minimum rotation angle of the stepping motor 27 is 0.36 ° per pulse and the lead of the ball screw 26 is 1 mm, the minimum vertical movement amount per pulse is 0.001 mm (1 μm). When moving smaller than this, if microstep control is used, and if the microstep control is divided into 1/100, the minimum moving amount d in the vertical direction is d = 1 μm / 100 = 0.01 μm. Theoretically, movement can be controlled with a minimum resolution of 0.01 μm. However, as described above, it is difficult to perform accurate control with microstep control.

  FIG. 6 is a diagram showing a flow for controlling the stepping motor by utilizing the change in contrast between light and dark of the light interference fringes. The generation mechanism of interference fringes will be described with reference to FIG.

  If the subject has a Z1 and Z2 portion with a step of λ / 2, and the lens is moved, the step of λ / 2 is present when Z1 is at a position where the optical path difference from the reference light is 0 or shifted by the wavelength. Dark stripes appear in Z1. Since this is within the depth of field of the lens, it can be observed. Further, when the lens is moved, it can be determined that the λ / 2 lens has moved at a position where the dark stripe disappears.

  As the light / dark judgment, the R, G, and B values of the dark-striped image are examined, and when the maximum value is 100 or less, it is determined that the image is dark. R, G, and B usually have values of 0 to 255, and the smaller the numerical value, the darker. Conversely, a bright stripe is determined as a bright stripe when the maximum value of R, G, B is 200 or more.

The autofocus operation is performed using a contrast determination method.
In this method, there is little change in contrast in the out-of-focus state, and when the focus starts to be adjusted, the change in contrast becomes large. Therefore, the portion where the change in contrast is large is searched and focused.

  First, set the upper and lower limits for vertical movement. The lower limit sets the starting position of the process, but also has a meaning of preventing the lens from being lowered too much and coming into contact with the subject. The upper limit is for setting the end position of the process.

  The interference zoom lens system 35 moves upward from the lower limit position in steps of 0.01 μm by microstep control. The image processing unit 6 monitors the change in contrast of the captured image at each step. Interference fringes occur where the observation surface of the subject 18 is displaced by (1 + n) * λ / 2 with respect to the reference surface 20 (where n is an integer greater than or equal to 0 and λ is the wavelength of the observation light). In particular, the contrast of the zeroth-order interference fringe generated at the location displaced by λ / 2 is the largest.

Therefore, if the change in the contrast of the captured image is large, it is assumed that interference fringes with a displacement of λ / 2 are generated, so whether the bright and dark parts of the contrast are periodic in the interference fringe determination routine. If there is periodicity, it is determined that interference fringes are generated.
That is, if the change in contrast is monitored in this way, the actual movement amount of the stepping motor can be controlled with a resolution of λ / 2.

  If shooting is performed at a position where the interference fringes are generated, a captured image can be acquired with an actual movement amount of λ / 2 steps, and multi-focus image synthesis can be performed at λ / 2 steps. Usually, since an interference fringe image is unnecessary, the interference fringes disappear when the shutter 24 described above is closed.

  In addition, if the number of output pulses of microstep control at the time of occurrence of interference fringes is memorized, even if it is necessary to focus again, positioning is performed by microstep control with the stored number of pulses. For example, since it is possible to instantly position every λ / 2 without monitoring the contrast because of whether or not interference fringes are always generated, it is possible to realize a high speed autofocus operation and an improved accuracy.

1 Image processing device
2 Display section
3 Light source
4 Stepping motor controller
5 Camera control unit
6 Image processing section
7 Camera cable
8 Motor cable
9 Light guide
10 CCD camera
11 Zoom lens system
12, 25 Electric block
13, 17 Lighting section
14,19,21 Objective lens
15, 22 Beam splitter
16 Light from light source
18, 32 subjects
20 Reference plane
23 Imaging detector
24 Shutter
26 Ball screw
27 Stepping motor
28 Manual dial
29 Fixing lever
30 Manual block
31 Paul
33 Stand
34 Lens fixing block
35 Interference zoom lens system

Claims (5)

  In a digital microscope that performs a zooming operation using a stepping motor, a linique interference fringe generator is attached to the light incident side of the zoom lens system, and the focus adjustment during the zooming operation is generated by this linique interference fringe generator. A focus adjustment method in a digital microscope using a zoom lens that controls the stepping motor with a resolution of 0.36 ° or less per pulse by performing based on contrast information of light and dark of the interference fringes.   A CCD camera or CMOS camera is connected to the interference zoom lens system, which is a zoom lens, and the imaging system of the linique interference fringe generator has an illumination system that illuminates the subject. An interference processing zoom lens system comprising: an image processing unit that performs multi-focus processing using the captured image and records the processed image; and a display unit that displays each image. Is fixed to a stage that is movable in the vertical direction, and is configured to be able to adjust the focus by moving the interference zoom lens system in the vertical direction and to adjust the focus during zooming operation. A digital microscope equipped with a focus control means based on contrast information of light and darkness of interference fringes generated by a type of interference fringe generator Focus adjustment device.   In the interference type zoom lens system, an optical path blocking means for opening and closing the optical path of the reference light causing interference is provided, thereby generating an image without interference fringes by closing the optical path of the reference light, and the CCD The focus adjustment device for a digital microscope according to claim 2, wherein the focus adjustment device is configured to be capable of photographing with a camera or a CMOS camera.   The vertically movable stage part has a structure that can be manually moved up and down, and a structure that can be moved up and down electrically using a stepping motor, and the stepping motor can be controlled by a stepping motor control part. 3. The focus adjustment device for a digital microscope according to claim 2, wherein if necessary, the electronically moving structure is removed so that a manual zooming operation can be performed. . 3. The focus adjustment in the digital microscope according to claim 2, wherein the stepping motor drive control can be controlled by using a change in contrast between light and dark interference fringes in conjunction with pulse drive control. apparatus.

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