CN105737739B - Utilize the experimental provision and method of total reflection prism measurement filament tiny length change - Google Patents

Abstract

The invention discloses an experimental device and method for measuring tiny length changes of filaments by using a total reflection prism. The experimental device consists of a top plate, a bottom plate, a bottom plate prism, a top plate prism, a turning prism, a laser transmitter, a laser receiver, and a laser range finder. , filaments and connecting columns. It uses the bottom prism and the top prism to make the laser turn 180° multiple times, and turns the laser 90° through the turning prism to form a laser circuit of laser transmitter-top prism, bottom prism, turning prism-laser receiver. By analyzing the change of the overall optical path length before and after the action occurs, the length change of the filament is obtained, and the measurement of the millimeter-level tiny filament length change is converted into the measurement of the meter-level overall laser circuit distance, which improves the measurement accuracy and is less affected by the external environment. . The invention is simple and fast, has low requirements on experimental operation skills, and is suitable for teaching physics experiments.

Description

Experimental Apparatus and Method for Measuring Micro-length Changes of Filament Using Total Reflection Prism

technical field

The invention relates to a physical experiment device and method, in particular to an experimental device and method for measuring tiny length changes of filaments by using a total reflection prism.

Background technique

Measuring tiny length changes of filaments is a key issue in experiments such as the determination of the elastic modulus of metal wires and the linear expansion coefficient of metal wires. In reality, because the length change of the metal filament in the experiment is usually a small amount, generally between 0.1mm and 1mm, the conventional measurement method cannot meet the experimental accuracy requirements.

The optical lever method is widely used in the existing university physics experiments to measure the small linear deformation of the metal wire. The optical lever method uses the optical lever reflector to tilt as the metal wire elongates, and the inclination of the optical lever reflector is deduced according to the position change of the reflected light. Angle, and then the elongation of the wire. This method has simple equipment and is widely used, but the optical system composed of optical lever reflectors, telescopes and scales is difficult to adjust, and it is easily disturbed by the external environment after adjustment. The operation is complicated and the measurement is time-consuming. This requires the experimenter to be precise and skilled when using the optical lever method to measure small changes in the length of the filament. Therefore, the accuracy of the measurement results is greatly affected by human factors. Due to the limitation of students' hands-on ability and proficiency in practical teaching, it is generally difficult to obtain ideal experimental results.

The invention provides an experimental device and method for measuring tiny length changes of filaments by using a total reflection prism. The total reflection prism is a prism whose main section is an isosceles right triangle. It uses the principle of total reflection to change the direction of light path. , the light is reversed 180° without loss. The invention uses a total reflection prism to change the light path, combines with a laser range finder to measure the overall optical path distance, and then obtains the tiny length change of the filament according to the change of the overall optical path distance before and after loading.

Contents of the invention

The invention provides an experimental device and method for measuring tiny length changes of filaments by using a total reflection prism, and the device and method realize simple, fast and accurate measurement of tiny length changes of filaments.

In order to achieve the above object, the experimental device of the present invention includes: a top plate, a bottom plate, a bottom plate prism, a top plate prism, a turning prism, a laser emitter, a laser receiver, a laser rangefinder, a filament, and a connecting column.

Described base plate prism, top plate prism and turning prism are all total reflection prisms, and its cross section is an isosceles right triangle, and the longitudinal side where the right angle of cross section is called right angle side; The longitudinal surface where the hypotenuse of cross section is called hypotenuse ; The longitudinal surface where the straight edge of the cross section is located is called the straight edge surface;

The top plate and the bottom plate are rectangular rigid plane plates, the top plate and the bottom plate are arranged relatively parallel up and down, and the upper surface of the top plate is fixed;

The laser emitter, laser receiver, and laser range finder are arranged at the front left corner of the upper surface of the base plate, wherein the laser emitter can emit vertical laser light, the laser receiver can receive horizontal laser light, and the laser emitter and laser receiver A laser range finder is connected to the bottom of the device, which displays the overall optical path length by processing the characteristics of the laser signals received and received by the laser transmitter and laser receiver.

The base plate prisms are two rows of total reflection prisms arranged in parallel, and the number of base plate prisms in the two rows is equal, each being n, symmetrically arranged on the two long sides of the base plate along the transverse axis of the base plate, and the right-angled sides of the base plate prisms are fixed on the base plate, The right-angle side is perpendicular to the long side of the bottom plate, and the hypotenuse of the bottom plate prism is parallel to the bottom plate;

Turning prisms are arranged at the rear left corner of the upper surface of the base plate, the front right corner and the rear right corner of the lower surface of the top plate. The base plate (top plate) prism hypotenuse face is connected, and its right-angled side is parallel with the long side of base plate and top plate, and the hypotenuse face of steering prism is towards the device outside, and right-angled side is near the center of base plate and top plate.

The bottom plate prism and the top plate prism have the same size, and the number is 2n. The length of the right-angled side is h, and the length of the hypotenuse of the cross-section is 2h; the length of the right-angled side of the turning prism is h, and the length of the straight side of the cross-section is h.

The top plate prisms are two rows of parallel total reflection prisms arranged along the two long sides of the bottom surface of the top plate in the same arrangement as the bottom plate prisms; The right-angled sides of the base plate prism are in the same vertical plane.

A connecting column is arranged at the center of the lower surface of the top plate and the upper surface of the bottom plate, and the height of the connecting column is equal to half of the height of the bottom prism and the top prism, ie h/2.

The filament is connected between two connecting posts.

During the experiment of the experimental device of the present invention, the laser beam emitted by the laser emitter is turned 180° by the bottom plate prism and the top plate prism, and the laser light is turned by 90° by the turning prism to form the laser emitter-top plate prism, bottom plate prism, turning prism- Laser circuit of the laser receiver.

According to the size of each prism and the size of the top and bottom plates, it can be known that the horizontal propagation distance of the laser in the laser circuit of this experimental device is constant, and the total length is a fixed value S ₁ .

Based on the above-mentioned experimental device and principle analysis, the main steps of a kind of experimental method utilizing total reflection prism to measure the tiny length change of filament provided by the present invention are as follows:

(1) It is known that there are 2n prisms on the top plate of the experimental device, 2n prisms on the bottom plate, and 3 turning prisms, and the two ends of a section of filament are respectively connected between the two connecting columns of the top plate and the bottom plate, and the position of the bottom plate is adjusted. , so that the bottom plate is horizontal and opposite to the top plate;

(2) Turn on the power supply of the laser transmitter, laser receiver and laser range finder, measure the length S of the laser circuit, according to the total length of the horizontal propagation process in the laser circuit formed by the known experimental device is a fixed value S ₁ , all laser The propagation process includes 4n+2 vertical propagation optical paths, and the vertical propagation distance S ₂ =(4n+2)H=SS ₁ of the laser circuit is obtained, where H is the length of a single vertical optical path, and the length of the filament in the initial state is obtained is L=H=(SS ₁ )/(4n+2);

(3) After the length of the filament changes due to external effects, re-measure the length S` of the laser circuit. According to the known device, the distance of all horizontal propagation processes of the laser circuit is still a fixed value S <sub>1</sub> , and the vertical propagation distance S` ₂ of the laser circuit is obtained. =(4n+2)H`=S`-S ₁ , then the length of the changed filament is L`=H`=(S`-S ₁ )/(4n+2);

(4) Calculate the length change ΔL of the filament caused by the external action ΔL=L`-L=(S`-S)/(4n+2).

The present invention forms a closed laser light path through the total reflection prisms and the steering total reflection prisms arranged in a staggered up and down direction, and obtains the length of the filament connected between the center of the upper plate and the lower plate according to the change of the overall optical path length before and after the action measured by the laser range finder. Variety. Compared with existing experimental devices and methods, the present invention has the following advantages:

1. Rely on the total reflection prism to change the laser propagation path, read the overall optical path length through the laser rangefinder, reduce external interference, simple operation, low requirements for instrument operation ability and proficiency, suitable for beginners;

2. The vertical reciprocating propagation of laser light is formed by multiple total reflection prisms, and the measurement of the length change of tiny filaments at the millimeter level is converted into the measurement of the overall laser circuit distance at the meter level, which improves the measurement accuracy.

The invention has simple operation and high precision, and is suitable for teaching physics experiments. Taking a phase type laser range finder with a measurement accuracy of 1mm as an example, when the number of the bottom plate prism and the top plate prism in the experimental device of the present invention are both 4, the measurement accuracy can reach 0.1mm in theory, which fully satisfies the requirements of the tiny filaments. Accurate measurement of length changes is required.

Description of drawings

Fig. 1 is a three-dimensional schematic diagram of the experimental device of the present invention;

Fig. 2 is the schematic diagram of turning prism and adjacent base plate (top plate) prism of the present invention;

Fig. 3 is a front view of the experimental device of the present invention;

Fig. 4 is a rear view of the experimental device of the present invention;

Fig. 5 is a left side view of the experimental device of the present invention;

Fig. 6 is a right view of the experimental device of the present invention;

In the figure: 1. top plate; 2. bottom plate; 3. bottom plate prism; 4. top plate prism; 5. steering prism; 6. laser transmitter; 7. laser receiver; 8. laser range finder; 10. Weight; 11. Connecting column.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and a specific embodiment.

As shown in Figure 1, the experimental device described in this embodiment consists of a top plate 1, a bottom plate 2, a bottom plate prism 3, a top plate prism 4, a turning prism 5, a laser transmitter 6, a laser receiver 7, a laser rangefinder 8, a filament 9. It is composed of weight 10 and connecting column 11.

As shown in Figure 1, the top plate 1 and the bottom plate 2 are rectangular rigid thin plates, and the inner corner on the left side of the upper surface of the bottom plate 2 is arranged with a laser emitter 6, a laser receiver 7, a laser range finder 8, a laser emitter 6 and a laser receiver 7 Connected to the laser range finder 8, the laser range finder 8 is a phase type laser range finder with a measurement accuracy of 1 mm.

As shown in Figure 1, four bottom prisms 3 are respectively arranged in the two long sides of the bottom plate 2, and four top prisms 4 are respectively arranged in the two length directions of the top plate 1;

As shown in Figure 2, the bottom plate prism 3 and the top plate prism 4 are total reflection prisms, and its cross section is an isosceles right triangle, and the longitudinal side where the right angle of the cross section is called a right angle side; the longitudinal plane where the hypotenuse of the cross section is called The hypotenuse; the longitudinal plane where the straight side of the cross section is called the straight side;

As shown in Fig. 1 and Fig. 2, the base plate prism 3 and the top plate prism 4 have the same size, the length of its right-angled side is h, and the length of the hypotenuse of the cross section is 2h; the length of the right-angled side of the turning prism 5 is h, and the length of the straight side of the cross section is also for h.

As shown in Figures 1 and 2, the base plate prisms 3 are total reflection prisms arranged in parallel in two rows. Symmetrically arranged, the right-angled side of the bottom plate prism 3 is fixed on the bottom plate 2, the right-angled side is perpendicular to the long side of the bottom plate 2, and the hypotenuse surface is parallel to the bottom plate 2; similarly, the top plate prism 4 is two parallel rows of total reflection prisms, 4 in each row , arranged along the two long sides of the lower surface of the top plate 1, the arrangement form is the same as that of the bottom plate prism 3; and the top plate prism 4 is opposite to the bottom plate prism 3 in a staggered manner, the top plate prism 4 is arranged near the left side of the top plate 1, and the bottom plate prism 3 is close to the bottom plate 2 The right side of the top plate prism 4 is arranged so that the right-angled side of each prism of the top plate prism 4 and the bottom plate prism 3 of its bottom are in the same vertical plane.

As shown in Fig. 1 and Fig. 2, the rear left corner of the upper surface of the bottom plate 2, the front right corner and the rear right corner of the top plate 1 lower surface are all provided with a turning prism 5, and a straight side surface of the turning prism 5 is connected to the bottom plate 2 And the plane of top plate 1 is vertical, and another straight side is connected with the hypotenuse of adjacent bottom plate prism 3 (top plate prism 4), and its right angle side is parallel with the long side of bottom plate 2 and top plate 1, and the hypotenuse of steering prism 5 faces Outer, right-angled sides are near the centers of the bottom plate 2 and the top plate 1 .

As shown in Figure 3, it is the front view of the device and the visible optical path diagram of the front view. The laser light emitted from the laser transmitter 6 is vertically upward reflected by the top plate prism 4 and the bottom plate prism 3, and there are 8 times of 180 ° turning without loss, and then The laser signal propagating horizontally inward is formed by the turning prism 5 at the right corner of the front side of the top plate 1 .

Figure 4 is the visible light path diagram of the device's rear view and rear view, and Figure 6 is the visible light path diagram of the device's right view and right view. The signal turns 90° through the turning prism 5 at the right corner on the rear side of the top plate 1, and then propagates vertically downward; then it is reflected by the prism 4 on the top plate and the prism 3 on the bottom plate, turns 180° without loss for 8 times, and then passes through the back side of the bottom plate 2 The turning prism 5 at the left corner forms a horizontally outward laser signal.

As shown in FIG. 5 , it is the left view of the device and the optical path diagram visible in the left view. The laser signal transmitted horizontally through the turning prism 5 at the left corner of the rear side of the base plate 2 is received by the laser receiver 7 .

As shown in Fig. 5 and Fig. 6, the center of base plate 2 and top plate 1 is provided with connecting post 11, and the height of connecting post 11 is equal to half of the height of base plate prism 3 and top plate prism 4, i.e. h/2; 9 is connected between two connecting posts 11.

In this embodiment, taking the measurement of the vertical elongation of the filament as an example, the main experimental steps and methods are introduced.

(1) As shown in Figure 1 and Figure 5, connect the filament 9 between the two connecting columns 11, adjust the position of the bottom plate 2, make the bottom plate 2 horizontal and symmetrical with the top plate 1, and the length of a single vertical optical path is H, The length of the filament 9 in the initial state is L;

(2) Connect the laser transmitter 6, the laser receiver 7 and the laser range finder 8 power supplies, measure the laser circuit length S of the overall device under the initial state, according to the total horizontal propagation process in the laser circuit formed by the known experimental device The length is a fixed value S ₁ , the entire laser propagation process of this device includes 18 vertical propagation optical paths, and the vertical propagation distance of the laser circuit is obtained S ₂ =18H=SS ₁ , then the length of the filament in the initial state is L=H= (SS ₁ )/18;

(3) As shown in Figure 1, hang a weight 10 at the center of the lower surface of the bottom plate to make the thin 9 elongate, repeat the aforementioned steps (1) and (2), and re-measure the length S of the laser circuit, as shown in Figure 4 and As shown in Figure 6, the length of the filament 9 after stretching is L`, and the length of a single vertical optical path is H`. According to the known device, the distance of all horizontal propagation processes of the laser circuit is still a fixed value S ₁ , and the vertical length of the laser circuit is obtained. Propagation distance S` <sub>2</sub> =18H`=S`-S <sub>1</sub> , then the length of the filament in the initial state is L`=H`=(S`-S ₁ )/18;

(4) Calculate the elongation of the filament ΔL=L`-L=(S`-S)/18.

According to the accuracy of the laser rangefinder 8 used in this embodiment and the number of single vertical optical paths, it can be obtained that the measurement accuracy of this embodiment can theoretically reach 0.1 mm.

The above embodiment is only an application of the device and experimental method of the present invention, and is not a limitation thereto.

The present invention utilizes total reflection prisms arranged in different forms, combined with laser transceiver and distance measuring devices to form a closed laser circuit, and obtains the length change of the filament by analyzing the change of the overall optical path length before and after the filament length change. The experimental device and method are less affected by the external environment and the operation level of the experimenter, and have high measurement accuracy, which is suitable for university physics experiment teaching.

Claims (2)

1. An experimental device that utilizes a total reflection prism to measure the tiny length change of a filament, the experimental device consists of a top plate, a bottom plate, a bottom plate prism, a top plate prism, a turning prism, a laser transmitter, a laser receiver, a laser rangefinder, a filament , connecting columns, the top plate and the bottom plate are rectangular rigid plane plates, the top plate and the bottom plate are arranged relatively parallel up and down, and the top surface of the top plate is fixed; the bottom plate prism and the top plate prism are total reflection prisms, so that the vertically incident laser light can generate 180 ° reverse, the bottom plate prisms and the top plate prisms are arranged in parallel in two rows along the two long sides of the bottom plate and the top plate respectively, the number of bottom plate prisms and top plate prisms in each row is n, and the top plate prisms and the bottom plate prisms are staggered up and down, so that each top plate The connecting side between the prisms and the right-angle side of the bottom plate prism directly below are in the same vertical plane; the turning prisms are three total reflection prisms, which deflect the incident laser light by 90°, and the turning prisms are respectively arranged on the back side of the bottom plate The left corner, the right corner of the front side of the top board and the right corner of the rear side of the top board; the laser emitter, laser receiver, and laser rangefinder are arranged at the left corner of the front side of the upper surface of the bottom plate; the laser emitted by the laser emitter passes through the bottom plate prism and The top plate prism reflects vertically multiple times and changes the propagation direction through the turning prism to form a closed optical path, which is finally received by the laser receiver, and the length of the overall laser optical path is measured by the laser rangefinder. 2. a method that utilizes the experimental device described in claim 1 to carry out experiments, its main experimental steps are as follows: (1) Take a piece of filament and connect both ends between the two connecting columns of the top plate and the bottom plate respectively, adjust the position of the bottom plate so that the bottom plate is horizontal and opposite to the top plate up and down; (2) Connect the power supply of the laser transmitter, laser receiver and laser rangefinder, and measure the length S of the laser circuit; (3) After the filament length changes due to external action, re-measure the laser circuit length S`; (4) Calculate the filament length change ΔL=(S`-S)/(4n+2) caused by external effects, where n is the number of bottom prisms and top prisms in each row.