Equal-thickness interference experiment device based on rotary encoder

Abstract

The utility model discloses an equal-thickness interference experiment device based on a rotary encoder, which mainly comprises a power supply circuit, a CCD (Charge Coupled Device) camera, an incremental rotary encoder, a data acquisition and video character superposition circuit, a display and the like, the one-dimensional movable objective table, the CCD camera, the lens cone, the objective lens, the 45-degree semi-transparent and semi-reflecting mirror, the microscope lifting mechanism and the like are installed on the H-shaped supporting frame through connecting pieces. The incremental rotary encoder and the rotary hand wheel are installed on the two sides of the one-dimensional movable objective table respectively. According to the technical scheme, the device is reasonable in structural design, simple and convenient to operate, high in measurement precision, good in stability, wide in application range and high in practicability, interference fringes can be visually displayed in a large picture mode, and experimental data can be directly read in a digital form.

Description

Technical Field

[0001] The utility model relates to an optical experimental device, in particular to an equal thickness interference experimental device. Background Art

[0002] The equal-thickness interference experiment (such as Newton's rings, wedge tip, etc.) is a classic experimental project in university physics experiments. Traditional equal-thickness interference experimental devices all use mechanical optical reading microscopes as measuring tools to perform microscopic magnification measurement of interference fringes. For example, in the Newton's ring experiment, the specific method is to first pre-adjust the instrument to observe clear concentric ring-shaped interference fringes in the microscope eyepiece, and then rotate the micrometer drum to move the lens barrel while observing the relative position relationship between the "vertical cross wires" and the interference fringes in the eyepiece. After reaching a specific position, read the data of the position from the microscope reading scale, and then obtain the diameter of each interference ring, thereby calculating the radius of curvature of the plano-convex lens to be measured. However, there are some defects in the use of existing instruments:

[0003] (1) The measurer must observe the image of the Newton interference ring through a small eyepiece aperture. Long-term observation can easily cause visual fatigue and is not convenient for teachers to guide students' experiments and conduct teaching demonstrations.

[0004] (2) If your eyes touch the eyepiece during observation, the vertical crosshairs may shift, resulting in inaccurate measurement data.

[0005] (3) The magnification of the microscope is only 30 times, and the adjacent interference fringes seen in the eyepiece are very thin and close to each other. It is difficult to accurately grasp the relative position relationship between the "vertical cross wires" and the interference fringes during measurement, resulting in inaccurate measurement data.

[0006] (4) The 45° semi-transparent and semi-reflective mirror located at the microscope objective is very close to the Newton ring instrument. During measurement, it may hit its fixing screws and cause it to move, resulting in incorrect measurement data.

[0007] (5) The lifting mechanism of the microscope tube is prone to sliding down due to gravity during use, causing the image to become blurred or lost during measurement, resulting in inaccurate experimental data or experimental failure.

[0008] (6) It is easy to make mistakes or inaccurate estimates when reading the position on the micrometer handwheel. Utility Model Content

[0009] In view of the defects or shortcomings of the prior art, the purpose of the utility model is to provide an experimental device with reasonable structural design, simple and convenient operation, high measurement accuracy and good stability, which can not only intuitively display interference fringes on a large screen but also directly read experimental data in digital form.

[0010] In order to achieve the above-mentioned purpose, the utility model provides the following technical solutions: an equal-thickness interference experimental device based on a rotary encoder, mainly comprising a mainframe, an H-shaped support frame, a movable stage mounted on the H-shaped support frame, an interference fringe generating device, and a liftable microscope mounted on the upper end of the H-shaped support frame, wherein the microscope is a video microscopic imaging acquisition system, comprising a CCD camera, a lens barrel, an objective lens, a 45° semi-transparent and semi-reflective mirror, a microscope lifting mechanism, and a display; the equal-thickness interference experimental device also comprises a digital mobile measurement system, comprising a movable stage, an incremental rotary encoder, a rotating handwheel, and a display.

[0011] It includes a power supply circuit and a data acquisition and video character overlay circuit for providing working voltage to the camera, rotary encoder, signal processing circuit and display, as well as a power switch, a power input socket, a reset button and a peripheral interface arranged on the front and rear panels of the host casing.

[0012] The CCD camera adopts a high-definition color camera and is equipped with a cross-line generator.

[0013] The movable stage is composed of a frame guide rail, a precision lead screw, a slider and a stage module, a bearing, and a rotating handwheel; the precision lead screw runs through both sides of the frame guide rail, one end is connected to the rotating shaft of the rotary encoder, and the other end is connected to the rotating handwheel, and the middle part is connected to the slider and the stage module through a linkage mechanism. When the rotating handwheel is rotated, the slider and the stage module are driven to translate left and right on the guide rail through the precision lead screw, and at the same time, the encoder rotor is driven to rotate synchronously to realize the displacement counting function of the stage.

[0014] After adopting the above scheme, the utility model has reasonable structural design, simple and convenient operation, high measurement accuracy and good stability, can intuitively display interference fringes on a large screen and can directly read experimental data in digital form, has a wide range of applications and high practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a rear view of the structure of the utility model;

[0016] Figure 2 This is a front view of the structure of the utility model;

[0017] Figure 3 This is a schematic diagram of the structure of the one-dimensional movable platform of the utility model;

[0018] Figure 4 This is a block diagram of the working principle of the utility model. DETAILED DESCRIPTION

[0019] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the implementation modes and the accompanying drawings.

[0020] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the implementation methods and the accompanying drawings.

[0021] See also Figure 1 and Figure 2 The utility model relates to an equal thickness interference experimental device based on a rotary encoder, comprising a main machine (1), an H-shaped support frame (2), a one-dimensional movable stage (3), an incremental rotary encoder (4), a CCD camera (5), a lens barrel (6), an objective lens (7), a 45° semi-transparent and semi-reflective mirror (8), a Newton ring instrument (or a wedge tip) (9), a microscope lifting mechanism (10), and a display (11), wherein the CCD camera (5) is also characterized by having a built-in crosshair generator.

[0022] See also Figure 1 , Figure 2 and Figure 4 The host (1) is internally provided with a power supply circuit (1-1), a data acquisition and video character overlay circuit (1-2), and the front and rear panels of the chassis are respectively provided with: a main power switch (1-3), a 220V AC power input socket (1-4), a video output interface (1-5), a 12V display power output interface (1-6), an encoder signal input interface (1-7), a video input interface (1-8), a 12V camera power output interface (1-9), a reset button (1-10), and a power indicator light (1-11).

[0023] See also Figure 4 The power supply circuit (1-1) is a switching power supply, which can convert the 220V AC power input from the 220V AC power input socket (1-4) into 5V and 12V DC power, and is used to provide working voltage for the rotary encoder (4), data acquisition and video character overlay circuit 1-2, camera (5), display (11), etc.

[0024] See also Figure 1 and Figure 2 The data acquisition and video character overlay circuit 1-2 acquires and processes the displacement measurement data signal from the encoder signal input interface 1-6, and overlays the data in real time in the form of characters on the camera video screen from the video input interface 1-8, and displays it on the same screen on the display 11 through the video output interface 1-5. The 12V camera power supply output interface 1-9 and the 12V display power supply output interface 1-6 are used to provide working power to the camera and the display respectively.

[0025] The H-shaped support frame (2) is fixed to the upper surface of the chassis of the host (1).

[0026] The one-dimensional movable stage (3) and the microscope lifting mechanism (10) are fixed on the H-shaped support frame through a connecting piece.

[0027] The CCD camera (5) and the objective lens (7) are respectively fixed to the upper and lower ends of the objective lens barrel (6) by screw threads, and the 45° semi-transparent and semi-reflective mirror (8) is sleeved on the objective lens to form a whole. The microscope can be moved up and down by adjusting the microscope lifting mechanism (10), thereby realizing the focusing function of the microscope.

[0028] See also Figure 3 , a one-dimensional movable stage (3), which is composed of a frame rail (3-1), a precision lead screw (3-2), a slider and a stage module (3-3), a bearing (3-4), a rotating hand wheel (3-5), etc. The precision lead screw (3-2) is fixed to both sides of the frame rail (3-1) through bearings, one end of which is connected to the rotating hand wheel (3-5), and the other end is connected to the rotating shaft of the rotary encoder (4). The slider and the stage module (3-3) are located in the middle of the precision lead screw through a thread. When the rotating hand wheel (3-5) is rotated to cause the lead screw to rotate, the slider and the stage module (3-3) can be translated left and right along the frame rail (3-1), and at the same time, the rotor of the rotary encoder (4) is driven to rotate synchronously, thereby realizing encoding counting.

[0029] Specifically: the pitch of the precision lead screw (3-2) is a standard 1mm, the rotary encoder (4) is an incremental rotary encoder, and the output pulse number is 1000P / R. When the rotary hand wheel (3-5) is turned to cause the lead screw to rotate one circle, the slider and the stage module (3-3) can be translated 1mm left and right along the frame guide rail (3-1), and at the same time, the rotor of the rotary encoder (4) is driven to rotate synchronously one circle. The rotary encoder converts the translation displacement of the stage into a periodic electrical signal, and then converts the electrical signal into a counting pulse. This 1mm displacement will output 1000 pulses, and the size of the displacement represented by 1 pulse is 1 / 1000mm, that is, the displacement measurement accuracy of the utility model is ±0.001mm.

[0030] The utility model needs to be used with a monochromatic light source (helium-neon laser, semiconductor laser, sodium lamp or monochromatic LED lamp equipped with a color filter, etc.) to conduct experiments. This example uses the measurement of the curvature radius of a plano-convex lens using Newton's rings as an example to describe a specific method of using the utility model:

[0031] See 1. Figure 2 and Figure 4 , correctly connect the signal cables and power cables, turn on the power switch (1-3), the power indicator light (1-11) lights up, then turn on the switch button on the monitor, and the display lights up.

[0032] See also Figure 1, turn the rotating hand wheel (3-5) so that the slider and the stage module (3-3) are approximately located in the middle of the guide rail, place the Newton ring instrument (9) directly below the 45° semi-transparent and semi-reflective mirror (8), and pre-adjust the microscope lifting mechanism (10) so that the lower edge of the 45° semi-transparent and semi-reflective mirror is approximately 4-5 cm away from the Newton ring instrument.

[0033] Light up the monochromatic light source and adjust the light outlet height so that the light emitted by it will horizontally illuminate the 45° semi-transparent and semi-reflective mirror (8). At this time, the light beam reflected by the semi-transparent and semi-reflective mirror will vertically illuminate the Newton ring instrument (9), and generate reflected light on the upper and lower surfaces of the air layer of the Newton ring instrument respectively. Because the two reflected light beams are coherent light, interference is generated in the area where they meet, thereby forming interference fringes.

[0034] The interference fringe image is imaged on the CCD target surface of the camera (5) through the objective lens (7) and the lens barrel (6), thereby obtaining a real-time interference fringe image signal, and then the microscope lifting mechanism (10) is carefully adjusted to make the interference fringe image seen on the display screen the clearest.

[0035] Without blocking the light, move the Newton's ring instrument on the stage back and forth, left and right, so that the center of the dark spot in the center of the interference ring seen on the display coincides with the intersection of the crosshairs, and press the reset button (1-10) to return the position reading displayed in the upper right corner of the screen to zero.

[0036] If you need to measure the diameter of the interference fringes from the 11th to the 20th ring, turn the rotating hand wheel (3-5) while silently counting the number of dark rings that the vertical crosshairs pass (start counting with the center dark spot as 0), count to 23 and 4 rings and then reverse back. When the vertical crosshairs are tangent to the 20th ring, read a position reading on one side of the ring, continue to reverse the rotating hand wheel (3-5), and measure the position readings on the same side of the 20th, 19th, 18th, ... 11th rings respectively.

[0037] Continue to rotate the hand wheel (3-5) in the same direction, so that the vertical cross line passes the center dark spot and continues to move to the other side. At the same time, restart the counting with the center dark spot as 0. When the vertical cross line is tangent to the 11th ring, read a position reading on the other side of the ring. Continue to rotate the hand wheel (3-5) in the same direction, and measure the position readings on the other side of the 11th, 12th, 13th, ... 20th rings respectively. It should be noted that the values ​​have positive and negative values. Positive values ​​are read as positive, and negative values ​​are read as negative.

[0038] Once the reading begins, the handwheel must be rotated in one direction all the time and cannot be rotated in the opposite direction at any position in the middle. Otherwise, a return difference will be generated due to the gap in the screw drive mechanism, resulting in incorrect measurement data.

[0039] The diameter of the corresponding interference ring can be obtained by calculating the difference between the position readings of the measured data according to the corresponding number of rings and taking the absolute value.

[0040] According to the experimental principle of "Measuring the curvature radius of a plano-convex lens using Newton's rings" [1], the curvature radius of a plano-convex lens is

[0041]

[0042] Among them, Dm and Dn are the diameters of the mth ring and the nth ring respectively, and λ is the wavelength of monochromatic light. It can be seen that as long as these physical quantities are known, the curvature radius R of the plano-convex lens can be obtained.

[0043] The specific data processing method is not the focus of the utility model description and will not be elaborated here. If necessary, please refer to reference [1].

[0044] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent shape or structural transformation made by using the contents of the present invention specification and drawings, or directly or indirectly applied to other technical fields related to the specification, are also included in the patent protection scope of the present invention.

Claims

1. An equal thickness interference experimental device based on a rotary encoder, mainly comprising a mainframe, an H-shaped support frame, a movable stage mounted on the H-shaped support frame, an interference fringe generating device, and a liftable microscope mounted on the upper end of the H-shaped support frame, characterized in that: The microscope is a video microscopic imaging acquisition system, including a CCD camera, a lens barrel, an objective lens, a 45° semi-transparent and semi-reflective mirror, a microscope lifting mechanism, and a display; the equal-thickness interference experimental device also includes a digital mobile measurement system, including a movable stage, an incremental rotary encoder, a rotating handwheel, and a display.

2. The equal thickness interference experimental device based on a rotary encoder as claimed in claim 1, characterized in that: It includes a power supply circuit and a data acquisition and video character overlay circuit for providing working voltage to the camera, rotary encoder, signal processing circuit and display, as well as a power switch, a power input socket, a reset button and a peripheral interface arranged on the front and rear panels of the host casing.

3. The equal thickness interference experimental device based on a rotary encoder as claimed in claim 1, characterized in that: The CCD camera adopts a high-definition color camera and is equipped with a cross-line generator.

4. The equal thickness interference experimental device based on a rotary encoder as claimed in claim 1, characterized in that: The movable stage is composed of a frame guide rail, a precision lead screw, a slider and a stage module, a bearing, and a rotating handwheel; the precision lead screw runs through both sides of the frame guide rail, one end is connected to the rotating shaft of the rotary encoder, and the other end is connected to the rotating handwheel, and the middle part is connected to the slider and the stage module through a linkage mechanism. When the rotating handwheel is rotated, the slider and the stage module are driven to translate left and right on the guide rail through the precision lead screw, and at the same time, the encoder rotor is driven to rotate synchronously to realize the displacement counting function of the stage.

Images