CN109458934B - Optical micro-displacement measurement system - Google Patents
Optical micro-displacement measurement system Download PDFInfo
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- CN109458934B CN109458934B CN201810725273.0A CN201810725273A CN109458934B CN 109458934 B CN109458934 B CN 109458934B CN 201810725273 A CN201810725273 A CN 201810725273A CN 109458934 B CN109458934 B CN 109458934B
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- photodiode array
- output voltage
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- light
- adder
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- 238000006073 displacement reaction Methods 0.000 title claims abstract description 39
- 238000005259 measurement Methods 0.000 title claims abstract description 13
- 230000003287 optical effect Effects 0.000 title claims abstract description 11
- 238000005286 illumination Methods 0.000 claims abstract description 6
- 238000012545 processing Methods 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 4
- 230000005484 gravity Effects 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000003491 array Methods 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000010606 normalization Methods 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
Classifications
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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
Abstract
The invention discloses an optical micro-displacement measurement system.A measured object is connected with a laser tube through a connecting rod, and the laser tube and the measured object have the same displacement; if the light emitted by the laser tube forms a light spot through the lens system and only strikes a certain photodiode on the photodiode array, the position of the laser tube corresponds to the position of the light spot in the photodiode array, namely the serial number of the light receiving diode. When the light spot striking the photodiode array may cover a plurality of diodes, an equivalent photodiode can be envisaged, the serial number of which may be a non-integer, and the corresponding output voltage V, according to the laser intensity distribution on the photodiode array ∑ The contribution to the adder output is equal to the total light-receiving diode output V 1 …V i …V n Sum of contributions. The serial numbers of the equivalent photodiodes indicate the barycenter positions of all the light-receiving diodes of the photodiode array, the barycenter positions being related to the laser intensity distribution on the photodiode array, and being unrelated to the illumination intensity and propagation attenuation.
Description
Technical Field
The invention belongs to the field of measuring instruments, and relates to an optical micro-displacement measuring system.
Background
The side slopes of the reservoir bank of the large reservoir are subjected to geological disasters such as dangerous rock, landslide, land crack and the like on the mountain road and railway side slopes. Before these disasters occur, the related ground surface needs to undergo micro-displacement. The large-scale buildings such as bridges, dams, skyscrapers and the like can generate micro-displacement and micro-deformation in use. These minor variations directly affect the safety of the building. Micro-displacement measurement is a main monitoring means for hazard warning.
Patent ZL20031011925.9 "a micro-displacement measurement technique" is well applied, but when the measurement distance increases, the received signal decays rapidly, for example, the distance increases by 10 times, and the signal reflected by the corner reflector weakens by 10000 times under the same condition. The corner reflectors and the antenna are then large in size or in transmit power, which limits their application. The patent ZL201310067245.1 'remote micro-displacement measurement technology' overcomes the problems, and the micro-displacement of objects tens of thousands of kilometers away can be measured by using a coherent active reflector instead of a corner reflector.
However, the two micro-displacement measurement techniques are based on the microwave ratio phase ranging, the micro-displacement direction is required to be basically consistent with the observation direction, otherwise, the sensitivity of sensing the micro-displacement is reduced. This limits certain applications, such as: for a river-crossing bridge, the vertical micro-displacement generated by an automobile on a bridge deck is measured, and the micro-displacement measuring instrument cannot be placed on the river surface, but can only be placed on a bridge pier. At this time, the micro-displacement direction is not consistent with the observation direction and is approximately vertical, and precise distance measurement by microwave phase comparison cannot be performed. Another example is: the micro-displacement of the barrage is measured, the river is arranged at the downstream of the barrage, the micro-displacement direction is not consistent with the observation direction, the micro-displacement direction is approximately vertical, and the microwave phase-comparison precise distance measurement cannot be used.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides an optical micro-displacement measurement system.
As shown in fig. 1, the measured object 1 is connected with the laser tube 2 through a connecting rod, the displacement of the measured object 2 is the same as that of the measured object 1, and the displacement range of the measured object 1 is d; the light emitted by 2 is formed by the lens system 3, and the light spot is formed on a certain photodiode of the photodiode array 4, and the position of 2 corresponds to the position of the light spot in the photodiode array, namely the serial number of the light receiving diode. The output circuit 5 gives a voltage representing the position data according to the serial number. This simple design actually solves two problems: a. although the micro-displacement positions of the measured object are in one-to-one correspondence with the serial numbers of the light receiving diodes, the laser propagation attenuation is greatly affected by the atmospheric visibility, and under the condition that the positions of the measured object are the same as the serial numbers of the corresponding light receiving diodes, the laser intensities reaching 4 in different weather are different, the output voltages of the output circuits are different, and the positions cannot be represented. b. The light spot striking the photodiode array may cover a plurality of diodes, i.e. the plurality of diodes receives light. The output circuit should still output a voltage indicative of the displacement of the object under test. Simply, a threshold voltage can be set, and the serial number of the light-receiving diode with the largest output voltage is selected to represent the displacement of the measured object. The intensity of the laser light reaching the photodiode array changes with changes in atmospheric visibility and thus the photodiode output voltage. This threshold voltage is difficult to select and must vary with atmospheric visibility. In addition, it is difficult to distinguish between the largest and second largest light-receiving diodes with low signal-to-noise ratios. For this purpose, a data processing and micro-displacement output circuit as shown in fig. 2 is proposed.
The photodiode array is provided with n photodiodes (the photodiodes of the photodiode arrays S4111-16Q, S4111-35Q, S4111-46Q and n are respectively 16, 35 and 46) which are popular in the market, and the output voltage of the photodiodes is V after laser irradiation 1 …V i …V n They are output in parallel to the data processing and micro-displacement output circuit. 7 are n low noise preamplifiers. 8 is an adder formed by an operational amplifier, U 1 For its output voltage, R f For feedback resistance, G 1 …G n Is the conductance value of n input resistors. Reference numeral 9 denotes an auxiliary adder formed by operational amplifiers, U 2 For its output voltage, R f The conductance values of the n input resistors are all G as feedback resistors. 10 is a divider, the output voltage is: u=u 1 /U 2 。
Wherein the method comprises the steps ofTherefore, it is
Description is now given of G 1 …G i …G n Is calculated as follows:
the n photodiodes provided with the photodiode array are sequentially and individually irradiated by lasers with near saturation intensity according to the sequence number i=1, 2, …, n, and the photodiodes sequentially output the same voltage V i =v, i=1, 2, …, n. The adder output is required to increase in steps as the serial number i of the light receiving photodiode increases. The ith photodiode receives light and outputs V as the time phase detector i . The method can write out: v (V) n ＝VR f G n ，V i ＝VR f G i ＝V n (i/n)＝VR f G n (i/n), thus
G i ＝G n (i/n) or R i ＝R n (n/i)(2)
The output voltage U and the lack of optical path attenuation will now be describedThe illumination intensity and the optical path attenuation only affect the signal to noise ratio. Set V 1 …V i …V n Is the output voltage of the photodiode in the original environment, and if the light path attenuation is reduced due to weather change, the illumination intensity is increased, and the output voltage of the photodiode is increased to k (V 1 …V i …V n ) Then
It can be seen that: the output voltage U is independent of the illumination intensity and the optical path attenuation.
The output of the output circuit is now described as representing the displacement of the object under test when the spot illuminating the photodiode array may cover a plurality of diodes. For ease of understanding, if a spot is struck at an adjacent diode seam, then the output U is: and->This is the spot illuminated at i and i+1 photodiode outputs +.>And->Is a median value of (c). If the light spot evenly irradiates on the adjacent diode, V i ＝V i+1 Then->This is exactly the spot average illumination i and i+1 photodiode outputs +.>And->Average value of (2).
The output U of the divider generally represents the output voltage distribution V of n photodiodes after the photodiode array receives light 1 …V i …V n Is included in the normalized weighted sum of (c). The normalization factor is the denominator of U. The weight coefficient isAfter the weight coefficient is selected, U is only distributed with the laser intensity on the photodiode array, namely V 1 …V i …V n The relevant amount is independent of weather visibility and propagation attenuation. The laser intensity distribution over the photodiode array includes the case where a large spot covers multiple diodes, and even multiple spots. The expression of U is rewritten as follows:
wherein the method comprises the steps ofG ∑ =ug, note G is a constant.
After the photodiode array receives light, an equivalent photodiode is envisaged, the output voltage of which is V ∑ The sequence number of the weight coefficient is G ∑ Its contribution to the adder output is equal to the total light-receiving diode output V 1 …V i …V n Sum of contributions. This is the physical meaning of U. It represents the position of the center of gravity of all the light receiving diodes of the photodiode array.
Drawings
Fig. 1 is a schematic diagram of optical micro-displacement measurement. In fig. 1, 1 is a measured object: 2 is a laser tube: 1 and 2 have the same displacement, and the displacement range is d:3 is a lens system, 4 is a photodiode array, 5 is a data processing and micro-displacement output circuit.
Fig. 2 is a schematic diagram of a data processing and micro-displacement output circuit. In fig. 2, 6 is a photodiode array circuit, 7 is a low noise preamplifier, 8 is an adder constituted by an operational amplifier, 9 is an auxiliary adder constituted by an operational amplifier, and 10 is a divider.
FIG. 3 calculation of R using Mathcad i (i=1, 2, …, 16) and V i (i＝1,2,…,16)。
Implementation of the measurement modes
For example: for n=16, let R f ＝50k，R 16 ＝5k，V 16 =5v, then R i ＝R 16 (16/i) calculating the weighted resistance R of the adder by Mathcad i (i=1, 2, …, 16) and photodiodes are individually illuminated in sequence V i (i=1, 2, …, 16), note adjacent biv i The difference is 0.3125 as follows:
Claims (2)
1. an optical micro-displacement measurement system, characterized in that: the object to be measured (1) is connected with the laser tube (2) through a connecting rod, the two are in the same displacement, light emitted by the laser tube (2) forms light spots through the lens system (3) to strike the photodiode array (4), the output voltage of the data processing and micro-displacement output circuit (5) is only related to the laser intensity distribution on the photodiode array, and is irrelevant to illumination intensity and propagation attenuation, the laser intensity distribution on the photodiode array (4) comprises the condition that the light spots cover a plurality of diodes, and the output voltage represents the gravity center position of all light-receiving diodes of the photodiode array.
2. An optical micro-displacement measurement system according to claim 1, wherein: in the data processing and micro-displacement output circuit,the photodiode array is provided with n photodiodes, and the output voltage is V after receiving laser irradiation 1 …V i …V n The method comprises the steps of carrying out a first treatment on the surface of the Amplified by n low noise preamplifiers, and then sent to an adder composed of operational amplifiers and an auxiliary adder composed of operational amplifiers in parallel, the output voltage of the adder isThe output voltage of the auxiliary adder isWherein R is f For feedback resistance, G 1 …G n For n input conductance values of the adder, G is the n input conductance values of the auxiliary adder; the divider output voltage is +.>An equivalent photodiode is conceivable, the output voltage of which is V ∑ The sequence number of the weight coefficient is G ∑ Its contribution to the adder output is equal to the total light-receiving diode output V 1 …V i …V n The sum of the contributions, which represents the first moment position of all the photodiodes of the photodiode array.
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Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1979091A (en) * | 2005-12-02 | 2007-06-13 | 鸿富锦精密工业（深圳）有限公司 | Optical measuring system |
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- 2018-07-04 CN CN201810725273.0A patent/CN109458934B/en active Active
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