Angle sensor and method based on light polarization characteristics

Abstract

The present invention discloses an angle sensor and method based on light polarization characteristics, comprising an LED light source, a polarizing plate, an analyzer polarizing plate, a non-polarized light-transmitting plate, a first photocell, and a second photocell, wherein: the analyzer polarizing plate and the first photocell constitute a first detection unit, the non-polarized light-transmitting plate and the second photocell constitute a second detection unit, the two groups of detection units are arranged in an axisymmetric manner, the LED light source is located on the extension line of the symmetry axis of the two groups of detection units, and the first photocell and the second photocell are respectively located on the side of the analyzer polarizing plate and the non-polarized light-transmitting plate facing away from the LED light source (1); the polarizing polarizing plate is installed on a rotating shaft and is located between the LED light source and the two groups of detection units, and the polarizing polarizing plate can rotate under the drive of the rotating shaft. The present invention utilizes the principle of light polarization for angle detection.

Description

Technical Field

[0001] The present invention belongs to the field of optical technology, and in particular relates to an angle sensor and method based on light polarization characteristics. Background Art

[0002] The existing deflection angle detection methods are mainly:

[0003] (1) Circular grating can detect angles in a 360-degree range with high accuracy. Disadvantages: a) High cost; b) Complex circuit; c) Some application scenarios only require a detection range of about 40 to 50 degrees. No 360-degree detection range is required. Figure 1 shown.

[0004] (2) Capacitance method based on butterfly sheet occlusion

[0005] The principle of a typical capacitance sensor is to insert a butterfly-shaped insulating sheet that rotates synchronously with the shaft between the RF source and the capacitor disk, and use an analytical circuit to measure the change in capacitance. Due to the shielding and rotation of the butterfly-shaped insulating sheet, the capacitance will change with the rotation angle. The change in capacitance indicates the current position value. Figure 2 shown.

[0006] Capacitive detectors emit radio frequency electrical noise that can interfere with nearby electronic equipment.

[0007] (3) Photoelectric method based on butterfly sheet occlusion

[0008] The principle of a general optical position sensor is to insert a butterfly-shaped piece that rotates synchronously with the shaft between the light source and the receiver, and use a photocell to measure the change in the amount of transmitted light. Due to the shading and rotation of the butterfly-shaped piece, the light power received by the photocell will change with the rotation angle. The change in the amount of transmitted light indicates the current position value.

[0009] like Figure 3 As shown, the photoelectric position sensor example uses an LED light source to illuminate a portion of four photocells. A butterfly piece that rotates synchronously with the shaft is inserted between the light source and the receiver. The projection of the butterfly piece is onto a pair of receiving cells. The transmitted light is detected by the photocell, and the change in the photocell current represents the position information of the rotor.

[0010] Optical position detectors are compact, low noise, low inertia, high speed, small size, and cheaper than capacitive sensors without sacrificing accuracy and stability. Summary of the invention

[0011] The purpose of the present invention is to provide an angle sensor and method based on light polarization characteristics to solve the problems existing in the above-mentioned prior art.

[0012] To achieve the above object, the present invention adopts the following technical solution:

[0013] An angle sensor based on light polarization characteristics comprises an LED light source, a polarizing plate, an analyzer polarizing plate, a non-polarized light-transmitting plate, a first photocell and a second photocell, wherein: the analyzer polarizing plate and the first photocell constitute a first detection unit, the non-polarized light-transmitting plate and the second photocell constitute a second detection unit, the two groups of detection units are arranged in an axisymmetric manner, the LED light source is located on the extension lines of the symmetry axes of the two groups of detection units, and the first photocell and the second photocell are respectively located on the side of the analyzer polarizing plate and the non-polarized light-transmitting plate facing away from the LED light source; the polarizing plate is installed on a rotating shaft and is located between the LED light source and the two groups of detection units, and the polarizing plate can rotate driven by the rotating shaft.

[0014] The non-polarized light-transmitting sheet is made of glass.

[0015] The area of ​​the polarizing plate is larger than that of the first photocell, and the area of ​​the non-polarizing light-transmitting plate is larger than that of the second photocell.

[0016] The polarizing plate is closely attached to the first photocell, and the non-polarizing light-transmitting plate is closely attached to the second photocell.

[0017] A deflection angle detection method comprises the following steps:

[0018] Step 1: The polarization direction of the polarizing polarizer rotates along the rotation axis, and the polarization direction of the analyzing polarizer forms an angle α with the initial position of the polarizing polarizer;

[0019] Step 2: The light emitted by the LED light source is converted into linear polarized light I0 through the polarizing plate. When the rotation axis deflection angle is θ, the light intensity passing through the polarizing plate and the non-polarized light-transmitting plate is respectively:

[0020] I1=I0*cos 2 (α-θ)

[0021] I2=I0

[0022] Step 3: Let the light intensity ratio f = I1 / I2, and eliminate I0 to obtain the relationship between the light intensity ratio and the rotation angle θ: f = cos 2 (α-θ), find θ.

[0023] Beneficial effects: The angle sensor and method based on the light polarization characteristics of the present invention can reasonably select the deflection angle α. Within a small angle range, the galvanometer deflection angle θ and the light intensity ratio f are approximately linearly related. The subsequent signal processing is simple and can be applied to small-angle deflection scenes such as galvanometers for angle detection; the device of the present invention has a simple structure and low cost; in the device of the present invention, the polarizer is very thin, has a small mass, a small moment of inertia, and has little effect on the dynamic balance of the rotating shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of a circular grating, where (a) is absolute encoding and (b) is incremental encoding;

[0025] Figure 2 is a schematic diagram of a dynamic insulated butterfly capacitive position sensor;

[0026] Figure 3 Schematic diagram of the optoelectronic method based on butterfly sheet occlusion;

[0027] Figure 4 It is a schematic diagram of the three-dimensional structure of the present invention;

[0028] Figure 5 It is a positional relationship diagram between the various components of the present invention;

[0029] Figure 6 for Figure 5 Left view of

[0030] Figure 7 It is the principle diagram of the optical path of the present invention;

[0031] Figure 8 is the f-θ relationship for different values ​​of the deflection angle α;

[0032] Fig. 9 f-θ relationship when α = 45°;

[0033] Fig.10 This is the f-θ diagram of the double-analyzer polarizer. DETAILED DESCRIPTION

[0034] The present invention will be further explained below in conjunction with the accompanying drawings.

[0035] like Figures 4 to 6 As shown, an angle sensor based on light polarization characteristics of the present invention comprises an LED light source 1, a polarizing plate 2, an analyzer polarizer 3, a non-polarized light-transmitting plate 4, a first photocell 5, and a second photocell 6, wherein: the analyzer polarizer 3 and the first photocell 5 constitute a first detection unit, the non-polarized light-transmitting plate 4 and the second photocell 6 constitute a second detection unit, the two groups of detection units are arranged axially symmetrically, the LED light source 1 is located on the extension lines of the symmetry axes of the two groups of detection units, ensuring that the initial LED light intensity after passing through the polarizer and shining on the two groups of detection units is the same, and the first photocell 5 and the second photocell 6 are respectively located on the side of the analyzer polarizer 3 and the non-polarized light-transmitting plate 4 facing away from the LED light source 1; the polarizing polarizer 2 is installed on the rotating shaft 7 and is located between the LED light source 1 and the two groups of detection units, and the polarizing polarizer 2 can rotate driven by the rotating shaft 7.

[0036] The light transmittance of the non-polarized light-transmitting sheet 4 is close to the light transmission axis of the polarizing sheet, and the material is glass.

[0037] The area of ​​the polarizing analyzer 3 is larger than that of the first photocell 5, and the area of ​​the non-polarized light-transmitting sheet 4 is larger than that of the second photocell 6; the polarizing analyzer 3 is closely attached to the first photocell 5, and the non-polarized light-transmitting sheet 4 is closely attached to the second photocell 6, so as to ensure that there is no interference from external stray light.

[0038] Based on the angle sensor based on light polarization characteristics provided by the present invention, the present invention provides a deflection angle detection method, comprising the following steps:

[0039] The following steps are involved:

[0040] Step 1: The polarization direction of the polarizing polarizer 2 rotates along the rotating shaft 7, and the polarization direction of the analyzing polarizer 2 forms an angle α with the initial position of the polarizing polarizer 2;

[0041] Step 2: The light emitted by the LED light source 1 is converted into linear polarized light I0 through the polarizing plate 2. When the rotation axis deflection angle is θ, the light intensities passing through the polarizing plate 3 and the non-polarized light-transmitting plate 4 are respectively:

[0042] I1=I0*cos 2 (α-θ)

[0043] I2=I0

[0044] Step 3: Let the light intensity ratio f = I1 / I2, and remove I0. Theoretically, the influence of the LED light intensity on the angle measurement error is avoided, and the relationship between the light intensity ratio and the rotation angle θ is obtained: f = cos 2 (α-θ), find θ.

[0045] By adjusting the value of α, different forms of f-θ curves can be obtained, such as Figure 8 .

[0046] By reasonably selecting the deflection angle α, within a small angle range, the galvanometer deflection angle θ and the light intensity ratio f are approximately linearly related. The subsequent signal processing is simple and can be applied to small-angle deflection scenes such as galvanometers for angle detection. In order to simplify subsequent processing, the α value when the f-θ curve is linearly related is selected.

[0047] like Fig. 9 The figure shows the f-θ relationship when α=45°. It can be seen that when α=45°, the light intensity ratio f and the rotation axis deflection angle θ are approximately linearly related.

[0048] The present invention also provides the following alternatives:

[0049] Replace the glass with an analyzer polarizer with an angle β with the polarization direction of the polarizer. When the motor deflection angle is θ, according to Malus's law, the light intensity passing through the two analyzers and the analyzer polarizer is:

[0050] I1=I0*cos 2 (α-θ)

[0051] I2=I0*cos 2 (β-θ)

[0052] Let f = I1 / I2, and negate I0. Theoretically, the influence of the LED light intensity on the angle measurement error is avoided, and the relationship between the light intensity ratio and the rotation angle θ is obtained: f = cos 2 (α-θ) / cos 2 (β-θ), and similarly select the α and β values ​​when the f-θ curve is linear, such as Fig.10 , α=45°, β=0°.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for detecting a deflection angle using an angle sensor based on light polarization characteristics, characterized in that: The angle sensor comprises an LED light source (1), a polarizing plate (2), an analyzing polarizing plate (3), a non-polarizing light-transmitting plate (4), a first photocell (5), and a second photocell (6), wherein the analyzing polarizing plate (3) and the first photocell (5) constitute a first detection unit, the non-polarizing light-transmitting plate (4) and the second photocell (6) constitute a second detection unit, the two groups of detection units are arranged in an axisymmetric manner, the LED light source (1) is located on the extension lines of the axes of symmetry of the two groups of detection units, and the first photocell (5) and the second photocell (6) are respectively located on the side of the analyzing polarizing plate (3) and the non-polarizing light-transmitting plate (4) facing away from the LED light source (1); the polarizing polarizing plate (2) is mounted on a rotating shaft (7) and is located between the LED light source (1) and the two groups of detection units, and the polarizing polarizing plate (2) can rotate under the drive of the rotating shaft (7); The deflection angle detection method comprises the following steps: Step 1: the polarization direction of the polarizing polarizer (2) rotates along the rotation axis (7), and the polarization direction of the analyzing polarizer (3) forms an angle α with the initial position of the polarizing polarizer (2); Step 2: The light emitted by the LED light source (1) is converted into linearly polarized light I0 through the polarizing plate (2). When the rotation axis is deflected at an angle of θ, the light intensities passing through the polarizing plate (3) and the non-polarized light-transmitting plate (4) are respectively: ; Step 3, let the light intensity ratio , minus I0, we get the relationship between the light intensity ratio and the rotation angle θ , and find θ.

2. The deflection angle detection method according to claim 1, characterized in that: By adjusting the value of α, different forms of f-θ curves are obtained, and α is selected when the f-θ curve is limited linear.

3. The deflection angle detection method according to claim 2, characterized in that: exist When , the light intensity ratio f and the rotation axis deflection angle θ are approximately linearly related.

4. The deflection angle detection method according to claim 1, characterized in that: The non-polarized light-transmitting plate (4) is replaced by an analyzer polarizer whose polarization angle with the polarizing polarizer is β. When the rotation axis deflection angle is θ, the light intensity passing through the two analyzers is respectively: ;make , make an appointment , we get the relationship between the light intensity ratio and the rotation axis deflection angle θ , and find θ.

5. The deflection angle detection method according to claim 1, characterized in that: The material of the non-polarized light-transmitting sheet (4) is glass.

6. The deflection angle detection method according to claim 1, characterized in that: The area of ​​the polarizing analyzer (3) is larger than the area of ​​the first photocell (5), and the area of ​​the non-polarizing light-transmitting sheet (4) is larger than the area of ​​the second photocell (6).

7. The deflection angle detection method according to claim 1, characterized in that: The polarizing analyzer (3) is in close contact with the first photocell (5), and the non-polarizing light-transmitting sheet (4) is in close contact with the second photocell (6).

Images