CN107941154B - Displacement measurement system and measurement method - Google Patents
Displacement measurement system and measurement method Download PDFInfo
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- CN107941154B CN107941154B CN201710984847.1A CN201710984847A CN107941154B CN 107941154 B CN107941154 B CN 107941154B CN 201710984847 A CN201710984847 A CN 201710984847A CN 107941154 B CN107941154 B CN 107941154B
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- alvarez lens
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- pinhole
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
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Abstract
The invention discloses a displacement measurement system, which is characterized by comprising: a light source; the Alvarez lens group consists of a first Alvarez lens and a second Alvarez lens which are complementary in surface shape, the second Alvarez lens moves relative to the first Alvarez lens along the direction vertical to the optical axis, the focal length of the Alvarez lens group is adjusted by adjusting the moving distance, and then the light energy of the parallel light reaching the pinhole is controlled; a pinhole for emitting convergent light through the Alvarez lens group; and the light detector is used for detecting the light energy transmitted from the pinhole. The measuring system provided by the invention has a simple structure, and can realize high-precision measurement of displacement by combining a plurality of devices with optical knowledge, and the measurement precision can reach 1.33 nm. The method has important significance for the application in the field of high-precision displacement sensing.
Description
Technical Field
The invention belongs to the field of displacement measurement, and particularly relates to a displacement measurement system and a displacement measurement method.
Background
In the prior art, displacement measurement methods are various, and a displacement sensor is usually adopted for accurately measuring micro displacement. The displacement sensor is also applied to the measurement of geometric quantities such as displacement, thickness, vibration, distance, diameter and the like of an object, and has wide application prospect in the civil and military fields.
An Alvarez lens is a polynomial surface-shaped lens proposed by Alvarez, and the focal length variation can be produced by a relative movement of a set of two pieces of such a lens in a direction perpendicular to the optical axis.
In the prior art, displacement sensors are mainly classified into inductive displacement sensors, capacitive displacement sensors, photoelectric displacement sensors, ultrasonic displacement sensors, and hall displacement sensors.
Disclosure of Invention
In view of the above, the present invention provides a displacement measurement system and a measurement method capable of measuring displacement with high accuracy.
A first embodiment of the present invention provides a displacement measurement system including:
a light source;
the Alvarez lens group consists of a first Alvarez lens and a second Alvarez lens which are complementary in surface shape, the second Alvarez lens moves relative to the first Alvarez lens along the direction vertical to the optical axis, the focal length of the Alvarez lens group is adjusted by adjusting the moving distance, and then the light energy of the parallel light reaching the pinhole is controlled;
a pinhole for transmitting the convergent light emitted from the Alvarez lens group;
a detector for detecting light energy transmitted through the pinhole.
The working principle of the measuring system provided by the embodiment of the invention is as follows:
the polynomial equation for the surface of the Alvarez lens is:
the resulting focal length f is:
wherein f is the combined focal length of the two Alvarez lenses, A is a polynomial coefficient, 2 delta is the moving distance between the two Alvarez lenses, and n is the material refractive index of the Alvarez lenses;
when the two Alvarez lenses have a slight displacement in the direction perpendicular to the optical axis, a large change in the combined focal length is caused, as can be seen from equation (2):
when two Alvarez lenses produce a distance change of Δ δ, resulting in a change of Δ f of the combined focal length, the spot size originally focused at the pinhole position becomes:
wherein r is the size of the radius of a light spot on a needle hole plane under the condition of changing the focal length, and D is the aperture of a light beam irradiated on the Alvarez lens;
from equations (3) and (4), we can obtain:
let the radius of the pinhole be r0And the energy distribution of the light spot is uniform, due to the change of the focal length, the energy μ received by the pinhole becomes:
as can be seen from equation (6), the position of the Alvarez lens changes, resulting in a very sensitive change in the energy transmitted through the pinhole. The displacement of the Alvarez lens can be accurately measured by detecting the energy transmitted through the pinhole.
Preferably, a collimating lens is disposed between the light source and the Alvarez lens group, and is configured to change the emitted light emitted by the light source into parallel light and emit the parallel light.
Preferably, the light source is a laser, an LED, or the like.
Preferably, the light detector may be replaced with an optical power meter.
The second embodiment of the invention provides a method for measuring displacement by using the system provided by the first embodiment, which comprises the following steps:
after the second Alvarez lens is fixed on the object to be measured, the light source, the collimating lens, the first Alvarez lens, the second Alvarez lens, the pinhole and the light detector are sequentially arranged along the optical axis direction;
and calculating the relative displacement of the first Alvarez lens and the second Alvarez lens according to the light energy penetrating through the pinhole, wherein the displacement is the displacement of the measured object.
The measuring system provided by the invention has a simple structure, and can realize high-precision measurement of displacement by combining a plurality of devices with optical knowledge, and the measurement precision can reach 1.33 nm. The method has important significance for the application in the field of high-precision displacement sensing.
Drawings
FIG. 1 is a schematic structural diagram of a displacement measurement system provided by an embodiment;
FIG. 2 is a schematic structural diagram of a displacement measurement system with a collimating lens according to an embodiment;
fig. 3 and 4 are schematic diagrams of power change generated by the movement of the Alvarez lens in the embodiment.
Detailed Description
In order to more specifically describe the present invention, the following detailed description is provided for the technical solution of the present invention with reference to the accompanying drawings and the specific embodiments.
Examples
Fig. 1 is a schematic structural diagram of a displacement measurement system according to an embodiment. Referring to fig. 1, the displacement measurement system provided in the present embodiment includes a light source 101; the Alvarez lens group is arranged on a light path of emergent light of the light source and consists of a first Alvarez lens 102 and a second Alvarez lens 103, the surface shapes of which are complementary, the second Alvarez lens 103 moves relative to the first Alvarez lens 102 along the direction vertical to the optical axis, the focal length of the Alvarez lens group is adjusted by adjusting the moving distance, and then the light energy of emergent light 101 of the light source reaching a pinhole is controlled; a pinhole 104 for emitting convergent light through the Alvarez lens group; the light detector 105 is used to detect the light energy transmitted through the pinhole.
In the present embodiment, the light source 101 is a laser, an LED, or the like.
Fig. 3 and 4 show schematic diagrams of power change generated by the movement of the Alvarez lens. From fig. 3 and 4, it is evident that: when the second Alvarez lens 103 moves in the direction perpendicular to the optical axis relative to the first Alvarez lens 102 and generates a small displacement, the focal length of the whole Alvarez lens group changes, from the original f to f Δ f, and the light spot changes from the original one point to the light spot with the radius of r.
As shown in fig. 2, in this embodiment, a collimating lens 106 is further disposed between the Alvarez lens unit and the light source 101, so that divergent light emitted from the light source 101 passes through the collimating lens 106 and then becomes parallel light to be incident on the Alvarez lens unit.
In this embodiment, it is assumed that the polynomial coefficient a of the first Alvarez lens 102 and the second Alvarez lens 103 is 1.0E-2(1/mm2), the lens material is PMMA (refractive index n is 1.5), the clear aperture D is 10mm, and the radius r of the pinhole is 10mm0Is 2 um. The distance from the pinhole plane to the Alvarez lens is assumed to be 20 mm; when the focus is just at the pinhole plane, all the light energy can be fully transmitted, and thenThe second Alvarez lens 103 is moved by a distance δ of 2.5mm relative to the first Alvarez lens 102. When δ changes by 1um (i.e., the second Alvarez lens 103 moves a distance of 1um with respect to the first Alvarez lens 102), i.e., Δ δ is 1um, it can be obtained from equation (5):
at the pinhole plane, the radius r of the spot is:
assuming that the energy of the light spot is uniformly distributed on the pinhole plane, the energy transmitted through the pinhole can be obtained from equation (6) as the energy of the light beam (the energy transmitted through the pinhole when the focus is at the pinhole plane position):
assuming that the detector is capable of accurately measuring the amount of change in the beam energy 1/1000, the accuracy of the Alvarez lens movement distance measurement can be calculated as follows:
therefore, the measuring precision of 1.33nm can be achieved, and the accurate measurement of nanometer level can be realized.
In this embodiment, the displacement test system is applied to displacement measurement, and the measurement method includes:
after the second Alvarez lens 103 is fixed on the object to be measured, the light source 101, the collimating lens 106, the first Alvarez lens 102, the second Alvarez lens 103, the pinhole 104 and the light detector 105 are sequentially arranged along the optical axis direction;
the relative displacement of the first Alvarez lens 102 and the second Alvarez lens 103 is calculated according to the light energy transmitted through the pinhole 104, and the displacement is the displacement of the measured object.
The above-mentioned embodiments are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only the most preferred embodiments of the present invention, and are not intended to limit the present invention, and any modifications, additions, equivalents, etc. made within the scope of the principles of the present invention should be included in the scope of the present invention.
Claims (4)
1. A displacement measurement method is characterized in that a system for realizing the displacement measurement method comprises the following steps:
a light source;
the Alvarez lens group consists of a first Alvarez lens and a second Alvarez lens which are complementary in surface shape, the second Alvarez lens moves relative to the first Alvarez lens along the direction vertical to the optical axis, the focal length of the Alvarez lens group is adjusted by adjusting the moving distance, and then the light energy of emergent light of the light source reaching a pinhole is controlled;
a pinhole for emitting convergent light through the Alvarez lens group;
a light detector for detecting light energy transmitted through the pinhole;
the displacement measuring method comprises the following steps:
after the second Alvarez lens is fixed on the object to be measured, the light source, the collimating lens, the first Alvarez lens, the second Alvarez lens, the pinhole and the light detector are sequentially arranged along the optical axis direction;
calculating the relative displacement of the first Alvarez lens and the second Alvarez lens according to the light energy penetrating through the pinhole and the formula (1), wherein the displacement is the displacement of the measured object;
wherein r is0The radius of the pinhole, D the beam aperture impinging on the Alvarez lens, δ the distance the second Alvarez lens is moved relative to the first Alvarez lens, and μ the energy received by the pinhole.
2. The displacement measuring method according to claim 1, wherein a collimating lens is disposed between the light source and the Alvarez lens group, for converting the emitted light emitted from the light source into parallel light and emitting the parallel light.
3. The displacement measuring method of claim 1, wherein the light source is a laser, an LED.
4. The displacement measuring method of claim 1, wherein the optical detector is replaced with an optical power meter.
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| CN108845382A (en) * | 2018-06-12 | 2018-11-20 | 杭州电子科技大学 | A kind of Alvarez lens zoom system containing harmonic diffraction surfaces |
| CN108931192A (en) * | 2018-06-12 | 2018-12-04 | 杭州电子科技大学 | A kind of displacement measurement system and measurement method |
| CN109001915A (en) * | 2018-08-28 | 2018-12-14 | 杭州电子科技大学 | A kind of Alvarez zoom intelligent glasses |
| CN109164596A (en) * | 2018-08-28 | 2019-01-08 | 杭州电子科技大学 | A kind of sandwich style Alvarez zoom intelligent glasses |
| CN109116581A (en) * | 2018-08-28 | 2019-01-01 | 杭州电子科技大学 | A kind of humorous diffraction Alvarez zoom intelligent glasses |
| CN109116580A (en) * | 2018-08-28 | 2019-01-01 | 杭州电子科技大学 | A kind of humorous diffraction Alvarez zoom intelligent glasses of sandwich style |
| US20220206119A1 (en) * | 2020-12-28 | 2022-06-30 | Beijing Voyager Technology Co., Ltd. | Mems actuated alvarez lens for tunable beam spot size in lidar |
| CN112764227A (en) * | 2021-01-28 | 2021-05-07 | 深圳珑璟光电科技有限公司 | Near-to-eye display system |
| CN114296155B (en) * | 2021-12-02 | 2023-02-07 | 华中科技大学 | Wide-spectrum optical zoom system based on double-layer medium super-surface |
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| KR101301448B1 (en) * | 2006-03-06 | 2013-08-28 | 옴니비젼 씨디엠 옵틱스 인코퍼레이티드 | ZOOM LENS SYSTEMS and METHOD FOR USE THEREOF |
| JP2014534462A (en) * | 2011-10-07 | 2014-12-18 | シンガポール国立大学Ｎａｔｉｏｎａｌ Ｕｎｉｖｅｒｓｉｔｙ Ｏｆ Ｓｉｎｇａｐｏｒｅ | MEMS type zoom lens system |
| TWI525802B (en) * | 2012-11-08 | 2016-03-11 | 威動光私人有限公司 | Zoom lens, optical device, method for manufacturing the same, and handheld electronic device comprising the same |
| GB201302719D0 (en) * | 2013-02-15 | 2013-04-03 | Adlens Ltd | Variable-power lens |
| CN113960702A (en) * | 2014-01-08 | 2022-01-21 | 威动光有限公司 | Lens assembly and actuator for optical system and method thereof |
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