CN202502296U - Accurate open-loop control system of an electrothermic type micro-mirror - Google Patents

Abstract

The utility model discloses an accurate open-loop control system of an electrothermic type micro-mirror. The control system comprises a laser light source, a first spectroscope, a second spectroscope, a micro-mirror device, a screen and a position sensitive sensor; The control system is characterized in that: the micro-mirror device is provided with an accurate open-loop control circuit comprising a central processor, an output digital-to-analog conversion module, a signal processing module, a sampling module and a security module. An accurate open-loop control method of an electrothermic type micro-mirror includes the steps of system parameter calibration and open-loop control. The accurate open-loop control system of the utility model is advantaged in that: micro-mirror process and packaging require no modification of processing; the accurate open-loop control system having few optical path elements is of low cost, simplicity in realization and strong practical applicability, and is capable of being used in micro-mirrors in a same edition after a first parameter calibration; the peripheral control circuit is simple and can be realized repeatedly; the open-loop system comprises a closed-loop control, greatly optimizing the accuracy of the system; and the open-loop system can accurately control a deflection angle of the micro-mirror.

Description

A kind of accurate open-loop control system of electrothermal micro mirror

Technical field

The utility model is a kind of accurate open loop controlling schemes of MEMS devices, belongs to the electronic circuit design field to MEMS.

Background technology

MEMS (Micro-electro-mechanical systems is called for short MEMS) is to utilize the produced three-dimensional devices of micro-processing technology, comprises that at least a movable structure satisfies certain mechanical effect.Therefore the MEMS device is applied to a lot of different fields owing to used for reference the technology of integrated circuit.This century, increasing sensor and actuator all tended to adopt the MEMS technology, and wherein the MEMS micro mirror is exactly one of them excellent illustration.The power that the MEMS Drive Structure produces is very little, but be enough to drive minute surface it is deflected.The electrothermal micro mirror is the MEMS that a dependence thermal deformation makes mirror deflection in numerous MEMS micro mirrors.The electrothermal micromirror systems mainly comprises minute surface, sway brace and three parts of actuating arm, and wherein actuating arm relies on electrocaloric effect to produce deformation exactly and drives mirror deflection.

Electrothermal micro mirror accurately control is complicated process, need utilize the external circuit system to weigh the attribute of system itself, demarcates the angle of micro mirror deflection with this.Electrothermal micro mirror graph scanning scheme cooperates laser display technology; Be applied to optical coherence tomography (Optical Coherence Tomography; Abbreviation OCT) technology can be used for the nothing wound tomoscan imaging of biological tissue; Be specially adapted to the early diagnosis of human viscera organ's cancer, its marketable value is quite huge, and prospect is also very wide in the application in the optical communication in addition.

Though some comparatively ripe controlling schemes have been arranged in MEMS micro mirror field, the scheme of carrying out accurate open loop control through electrothermal method is not arranged in electrothermal micro mirror field as yet, especially low-cost, the open loop controlling schemes that reliability is higher.

Summary of the invention

The utility model purpose is that the characteristic to heat driving micro mirror provides a kind of electrothermal micromirror systems and control method thereof of accurate open loop control.

The utility model adopts following technical scheme for realizing above-mentioned purpose:

A kind of accurate open-loop control system of electrothermal micro mirror comprises LASER Light Source, first spectroscope, second spectroscope, micro-mirror device, screen and position sensitive detector; Laser beam reaches on the micro mirror minute surface through first spectroscope, and the light beam of micro mirror direct reflection reaches on second spectroscope through first spectroscope, and second spectroscope is divided into two bundles with light beam, a branch of beating on position sensitive detector, a branch of beating on the coordinate screen; It is characterized in that: said micro-mirror device has accurate open-loop control circuit, and said accurate open-loop control circuit comprises central processing unit, the output D/A converter module, and signal processing module, sampling module and security protection module, wherein

Said sampling module comprises sampling resistor and analog-to-digital conversion module, and the driving voltage of gathering each actuating arm of micro-mirror device in real time through sampling resistor changes into digital signal and sends said central processing unit to;

Said central processing unit stores has output voltage variation delta V and corresponding standard micro mirror deflection angle variation delta θ; Output micro mirror drive signal, and the driving voltage variable signal of the actual actuating arm that transmits according to the said sampling module that receives is compared, is calculated deviate with the micro mirror deflection mirror surface angle changing value and the value of storage and compensates exporting signal;

Said output D/A converter module is that the numerical information with the output of central processing unit converts analog voltage signal to;

Said signal processing module is used for converting the analog voltage signal of said output D/A converter module output to the micro mirror driving voltage;

Said security protection module is to prevent to power on and the impact of power down moment surging signal to micro mirror.

A kind of accurate open-loop control method of electrothermal micro mirror comprises the steps:

(1) demarcation of systematic parameter:

After laser beam impinges perpendicularly on the micro mirror minute surface; Direct reflection goes out a branch of light and gets on screen and the position sensitive detector through second spectroscope; Be activated the deflection that certain angle takes place after the driving of voltage when minute surface; Certain skew can take place in the laser point on the screen; The coordinate position of record corresponding offset and position sensitive detector output sends to alive information of institute and position sensitive detector coordinate information in the computer upper computer software, simulates the relation curve of institute's making alive value and drift angle automatically; Calibrate the voltage linear district of micro mirror work, each deflection angle corresponding voltage value, the maximal value of the resolution of angle and micro mirror institute on-load voltage;

(2) open loop control:

Control the deflection angle of micro mirror according to the micro-mirror device systematic parameter control-driven system output voltage values of demarcating, it is corresponding with one of which one that the amount of the every changes delta V of output voltage has the Δ θ value of a standard; Feed back the size of on-load voltage on the micro mirror actuating arm through the real-time sampling of sampling resistor; In case the corresponding error that occurs with the relation of voltage of the deflection angle of micro mirror, D/A converter module is exported corresponding difference voltage by way of compensation, makes the precalculated position that forwards to that the drift angle of minute surface can be correct.

The utlity model has following advantage:

1, first the electrothermal scaling method is used for the deflection control of micro mirror.

2,, need not to do any processing change with encapsulating in micro mirror technology from the control of electronic circuit angle.

3, cost is low, realizes easily.

4, light path element is less, realizes simply, and is practical, behind the calibrating parameters, can use to same version micro mirror.

5, peripheral control circuit is simple, repeats easily to realize.

6, through the communicating by letter of host computer and Circuits System, data upload to upper computer software is calculated, simulate the relation of micro mirror voltage and angle automatically.

7, comprise closed-loop control in the open cycle system, the degree of accuracy of optimization system greatly can accurately be controlled the deflection angle of micro mirror.

Description of drawings

Fig. 1 is the utility model synoptic diagram;

Among the figure, 1, LASER Light Source; 2, first spectroscope; 3, micro-mirror device; 4, second spectroscope; 5, position sensitive detector; 6, screen; 7, sampling resistor; 8, sample circuit; 9, D/A converter module; 10, central processing unit; 11, signal processing module; 12, upper computer software; 13, security protection module.

Embodiment

Light path design: as shown in Figure 1 mainly is the light path method of building and the design of size; A branch of light that first spectroscope 2 is launched LASER Light Source 1 in the utility model is got on the micro mirror minute surface, the most important thing is that the minute surface of laser and micro mirror will keep strict vertical relation.Micro-mirror device 3 is activated the driving minute surface generation angular deflection of voltage; Light beam can reach on second spectroscope 4 through first spectroscope 2; Second spectroscope 4 is divided into two bundles with light beam, a branch ofly beats on position sensitive detector 5 (PSD) a branch of beating on coordinate screen 6.First spectroscope 2 will keep minimum distance apart from the distance of micro mirror minute surface; Second spectroscope, 4 positions will guarantee that light that first spectroscope 2 penetrates is beaten can strict vertical beating on position sensitive detector 5 (PSD) in 4 last times of second spectroscope, guarantees that again light can not depart from the beam split minute surface.Screen 6 will be tried one's best far with the distance of position sensitive detector 5 (PSD) distance second spectroscope 4, tries one's best with the scope measurement data of full scale the high resolving power when setting up with assurance micro mirror deflection angle and driving voltage relation.

The open loop circuit system design: the circuit of open cycle system as shown in Figure 1 comprises central processing unit 10, output D/A converter module 9, signal processing module 11, sampling resistor 7, sample circuit 8 and security protection module 13.Central processing unit 10 is centers of sequential operation, and D/A converter module 9 is that the numerical information with central processing unit 10 converts analog voltage signal to.Analog voltage signal is loaded on the micro mirror through the voltage signal that signal processing module 11 obtains the driving micro mirror that we set.Sampling module comprises that sampling resistor 7 and sample circuit 8 are to monitor the alive situation of micro mirror actuating arm in real time, and security protection module 13 is to prevent to power on and the impact of power down moment surging signal to micro mirror.

The scaling method of systematic parameter: the systematic parameter of demarcation is the deflection angle and alive relation of micro mirror.After laser vertical incides the micro mirror minute surface; Direct reflection goes out a branch of light and gets on screen 6 and the position sensitive detector 5 (PSD); Be activated the deflection that certain angle takes place after the driving of voltage when minute surface, certain skew can take place in the laser point on the screen 6, the coordinate position that record corresponding offset and position sensitive detector 5 (PSD) are exported; Alive information of institute and PSD coordinate information are sent in the computer upper computer software 12, simulate the relation curve of institute's making alive value and drift angle automatically.Calibrate the voltage linear district of micro mirror work, each deflection angle corresponding voltage value, the maximal value of the resolution of angle and micro mirror institute on-load voltage.

The method of the accurate open loop of electrothermal control: utilize the electric heating Characteristics Control drive system output voltage values of micro mirror to control the deflection angle of micro mirror, it is corresponding with one of which one that the amount of the every changes delta V of output voltage has the Δ θ value of a standard.Feed back the size of on-load voltage on the micro mirror actuating arm through the real-time sampling of sampling resistor.In case the corresponding error that occurs with the relation of voltage of the deflection angle of micro mirror, the output D/A converter module is exported corresponding difference voltage by way of compensation, makes the precalculated position that forwards to that the drift angle of minute surface can be correct.

Be connected on the external sampling resistor by the 4 pass pin of putting up after the light path MEMS shown in Figure 1, the magnitude of voltage of driving circuit output 0-4V stepping 100mV, respectively on the coordinate paper of screen and position sensitive detector (PSD) output terminal read coordinate figure; Upper computer software be recorded as (X, Y, V) with (X1; Y1; V1) wherein X represents horizontal ordinate, and Y represents ordinate, the V representative voltage.Response curve is exported and simulated to all coordinate figures.According to curvilinear characteristic, demarcate the voltage of sampling resistor and the corresponding relation of deflection angle.Demarcate the relation of MEMS resistive voltage and sampling resistor voltage difference and deflection angle again.Whether the voltage that utilizes the sample circuit acquisition monitoring to be loaded on the MEMS pin meets the magnitude of voltage of corresponding angle on the curve, if having deviation then D/A converter module output corresponding compensation voltage makes micro mirror can reach desirable inflection point.

Electrothermal MEMS micro mirror mainly is that actuating arm passes through different materials electrocaloric effect generation deformation generation stress zone index glass deflecting facet.Each micro mirror has 4 identical actuating arms, and when the on-load voltage value was the voltage of U, the heat Q that on actuating arm, produces can be expressed as:

$I_m=I_s=\frac{U_S}{R_S}$ $Q={I_m}^2{R}_{m}t=\frac{{U_m}^2}{R_m}t$ Q=cm Δ T+Q _Radiation+ Q _{Convection current}

U＝Um+Us R＝Rm+Rs

Rm is the heating resistor of MEMS actuating arm, and Rs is extraneous sampling resistor.U is the voltage of drive signal, and Um is the voltage on the MEMS actuating arm, and Us is the voltage at sampling resistor two ends.

Because the little light weight of actuating arm volume; Calorie value Q can convert temperature T on the actuating arm of micro mirror; Each T can have a deflection angle corresponding with it, thus the variation delta Q of heat corresponding Δ T, the corresponding relation of the deflection angle Δ α of Δ T and minute surface can be set up thus.Under the condition of constant voltage driving, the deflection angle of micro mirror and two relating to parameters, i.e. Um and Rm, wherein Rm can be changed by Influence of Temperature, can be expressed as:

R _m2＝R _m1(1+ΔT·TCR)

TCR is the temperature coefficient of resistance, and Rm1 is the resistance value under the heating resistor normal temperature, and Rm2 is a resistance value after the variation that causes of thermal conductance.Therefore the relation curve of actual voltage of depicting and angle has comprised two kinds of relations, and one is the variation that the variation of Um causes Q, thus one to be the variation of Q cause the variation of actuating arm temperature T to cause the variation of Rm.The sampling resistor value does not receive Influence of Temperature, and therefore Um=U-Us can cause the variation of Um the change curve of Q from these two kinds of relations, to be separated, and draws the performance number of consumption on actuating arm according to Im=Us/Rs simultaneously, and is mapped with deflection angle.

After setting up the relation curve of driving voltage and deflection angle, can set the deflection angle of micro mirror arbitrarily according to demand.The situation of the voltage monitoring deflection angle of gathering according to AD simultaneously, in case voltage changes, it is that set angle is constant that the voltage automatic compensating of DA output keeps the micro mirror angle to the corresponding driving arm.

Claims (1)

1. the accurate open-loop control system of an electrothermal micro mirror comprises LASER Light Source, first spectroscope, second spectroscope, micro-mirror device, screen and position sensitive detector; Laser beam reaches on the micro mirror minute surface through first spectroscope, and the light beam of micro mirror direct reflection reaches on second spectroscope through first spectroscope, and second spectroscope is divided into two bundles with light beam, a branch of beating on position sensitive detector, a branch of beating on the coordinate screen; It is characterized in that: said micro-mirror device has accurate open-loop control circuit, and said accurate open-loop control circuit comprises central processing unit, the output D/A converter module, and signal processing module, sampling module and security protection module, wherein

Said sampling module comprises sampling resistor and analog-to-digital conversion module, and the driving voltage of gathering each actuating arm of micro-mirror device in real time through sampling resistor changes into digital signal and sends said central processing unit to;

Said central processing unit is used to receive the driving voltage variable signal and the micro mirror deflection mirror surface angle changing value of the actual actuating arm that said sampling module transmits;

Said output D/A converter module is that the numerical information with the output of central processing unit converts analog voltage signal to;

Said signal processing module is used for converting the analog voltage signal of said output D/A converter module output to the micro mirror driving voltage;

Said security protection module is to prevent to power on and the impact of power down moment surging signal to micro mirror.

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