CN102937657A - Real-time correction method and system for high-speed atomic force microscopic imaging - Google Patents

Abstract

The invention discloses a real-time correction method and a system for high-speed atomic force microscopic imaging, and belongs to the technical field of high-speed atomic force microscopy. The method comprises that in a real-time phase correction module, one side of a bimorph is used as a test piece, a phase lag angle theta generated during each scan is tested, and acquired data are shifted to correct the phase lag; and in a non-linear correction module, actual space positions of data points acquired by the sinusoid scan are calculated through preset sampling point numbers of each period, and corrected probe deflection signals after correction are obtained through a certain mapping relation. According to the real-time correction method and the system for high-speed atomic force microscopic imaging, images can be processed in a scanning process instead of post processing, and a good real-time property is provided; and LabVIEW software is used for designing, so that the operation process is simple.

Description

A kind of real-time correction method and system for the imaging of high speed atomic force microscopy

Technical field

The present invention relates to the scanning microscopy imaging technical field, particularly a kind of real-time image correction system belongs to high speed atomic force microscopy field.

Background technology

Along with the development of science and technology, the fields such as biology, chemistry, material and nanosecond science and technology are in the urgent need to realizing at micro-nano-scale the technology of fast detecting or high speed imaging.Scanning probe microscopy (SPM) is the important tool of carrying out at present Nanometer Detection and Indication, is one of major technique that realizes micro-nano-scale imaging, detection and processing.

Atomic force microscope belongs to scanning probe microscopy family, is to improve on the basis of scanning tunnel microscope.Yet the image taking speed of traditional atomic force microscope is too slow, has limited its Detection ﹠ Controling to some dynamic processes such as biomacromolecule motion etc.Therefore, the sweep velocity that how to improve traditional atomic force microscope becomes the focus of research in recent years.

For high speed atomic force microscope, three-dimensional scanner is a key factor that affects sweep velocity.Scanister adopts piezoceramic material or quartz tuning-fork usually.Piezoceramic material has the advantages such as stable performance, easy to use and very high displacement resolution and dynamic responding speed, has become the main material of present making three-dimensional scanner.Realizing high-velocity scanning, generally be to realize with the very high piezoelectric ceramic stack of fundamental frequency, but the driving circuit of this device is complicated, needs powerful high pressure power amplifier and high-voltage power supply, also has in addition the problems such as cost is high, sweep limit is little.Another kind method is to use quartz tuning-fork to realize high-velocity scanning, namely is subject to the AC signal excitation and occurs realizing high-velocity scanning in the situation of resonance at quartz tuning-fork.But tuning fork is small-sized, lays the sample difficulty, and sweep limit is little, load capacity is low.Because the quality factor of tuning fork are very high, when its resonance scan, very easily be subjected to external interference in addition.So based on above analysis, list of references [1] (patent documentation CN101576466A) uses bimorph and piezoelectric ceramic tube, designs a kind of combined three-dimensional high-speed scanning device.In this device, bimorph is used for carrying out rapid scanning at directions X, and piezoelectric ceramic tube is used for regulating Y and Z both direction.Because excitation bimorph employed driving signal is sinusoidal signal but not triangular signal, so cause the image of collection to present nonlinear geometric distortion.Simultaneously, bimorph is realized rapid scanning by being operated under the resonance mode, so cause that gathering image produces the phase place hysteresis.Therefore, the image of the combined three-dimensional high speed device collection of list of references [1] design exists phase place to lag behind and nonlinear geometric distortion, need to be to correct image.

Summary of the invention

The objective of the invention is to exist phase place to lag behind and nonlinear geometric distortion for the image of existing combined three-dimensional high-speed scanning device collection, develop a kind of realtime graphic bearing calibration and system.The method can in whole data acquisition, the image that gathers is carried out real time correction, rather than process again the later stage to image.Realtime graphic corrective system of the present invention mainly comprises two aspects: a real-time phase correction module and a real time nonlinear correction module.These two modules all are based on existing hardware and LabVIEW software is realized.

The probe deflection signal that described realtime graphic bearing calibration and system are used for offset of sinusoidal scanning acquisition carries out real-time phase correction and real time nonlinear correction, its principle of work is: in the real-time phase correction module, use a side of bimorph as detection lug, detect the phase place lag angle θ that each scanning produces, then the correction by the data that gather being shifted realize that phase place lags behind; In the real time nonlinear correction module, by per cycle sampling number of setting, at first calculate the true spatial location at each data point place of sine sweep collection, then by certain mapping relations, obtain real sample message.

Specifically, described realtime graphic bearing calibration comprises carries out real-time phase correction and real time nonlinear correction two parts to the probe deflection signal, described real-time phase is proofreaied and correct and is carried out in the real-time phase correction module, be specially: by the detection signal of bimorph, obtain the phase place lag angle θ of bimorph, utilize phase place lag angle θ and per cycle sampling number N, obtain the k that counts that phase place lags behind, with the data ordinal shift k position that gathers, can realize the initial acquisition data are carried out the correction that phase place lags behind at last.The described k of counting calculates by following formula:

k＝(θ/180)*N/2

Described real time nonlinear is proofreaied and correct, and carries out in the real time nonlinear correction module, is specially: at first set per cycle sampling number N, determine the locus i at each sampled point place.Secondly, determine the locus i of each sampled point and the mapping relations between the real sample message (being the probe deflection signal), this wherein comprises the relation of three kinds of mappings: many-one shines upon, shines upon one to one and can't shine upon.

The invention has the advantages that:

(1) real-time: can in scanning process, process rather than post-processed image;

(2) simplification: use the LabVIEW Software for Design, operating process is simple.

Description of drawings

Fig. 1 is the hardware structure diagram of realtime graphic corrective system provided by the invention;

Fig. 2 carries out the process flow diagram that real-time phase is proofreaied and correct among the present invention;

Fig. 3 carries out the process flow diagram that real time nonlinear is proofreaied and correct among the present invention.

Embodiment

The present invention is described in further detail below in conjunction with drawings and Examples.

The present invention is a kind of realtime graphic bearing calibration and system, and described corrective system comprises real-time phase correction module and real time nonlinear correction module.Described real-time phase correction module is used for the probe deflection signal is carried out phase place correction or lag, and described real time nonlinear correction module is used for the signal of real-time phase correction module output is carried out gamma correction.The specific implementation of described System with Real-Time is as follows:

As shown in Figure 1, high-speed data acquisition card can gather the detection signal of bimorph and the probe deflection signal of probe deflection detection system, and these two kinds of signals are flowed to the PC that LabVIEW is installed by pci bus, in described PC, include realtime graphic corrective system provided by the invention, be used for described probe deflection signal is proofreaied and correct.For the real-time phase correction module, as shown in Figure 2, its course of work is: the detection signal by bimorph at first, obtain the phase place lag angle θ of bimorph, utilize phase place lag angle θ and per cycle sampling number N, obtain the k that counts that phase place lags behind, at last with the data ordinal shift k position that gathers, can realize the initial acquisition data are carried out the correction that phase place lags behind.The described k of counting calculates to round by following formula and obtains:

k＝(θ/180)*N/2

For the real time nonlinear correction module, be to carry out on the basis of carrying out phase place correction or lag, its course of work at first, for sine sweep, by the per cycle sampling number N that sets, is determined the locus i at each sampled point place as shown in Figure 3.Secondly, determine the locus i of each sampled point and the mapping relations between the real sample message (being the probe deflection signal), this wherein comprises the relation of three kinds of mappings: many-one shines upon, shines upon one to one and can't shine upon.

For the situation of many-one mapping, the numerical value of the collection that the locus is identical is averaged, as the data after proofreading and correct; For the situation of shining upon one to one, with the data after directly conduct is proofreaied and correct at the numerical value on this locus; For situation about can't shine upon, because the maximal rate of sine sweep can not surpass the twice of linear sweep speed, so at most only can occur a zone between the adjacent area can't corresponding situation, therefore, we average two adjacent numerical value of this zone as the data after proofreading and correct.Whole image correction process carries out simultaneously with data acquisition, storage, does not need the data that gather are carried out the processing in later stage.

Embodiment:

A real-time image correction system is based on existing hardware and the realization of LabVIEW software.Hardware consists of as shown in Figure 1, high-speed data acquisition card DA output sinusoidal drive signals drives bimorph resonance, the probe deflection signal of the detection signal of synchronous acquisition bimorph and probe deflection detection system, high-speed data acquisition card is connected with the PC that LabVIEW is housed by pci bus.Use LabVIEW software, design real-time phase correction module and real time nonlinear correction module.

In the real-time phase correction module, as shown in Figure 2, for the bimorph detection signal, utilize the extraction simple signal module among the LabVIEW, detect the angle θ (degree) that described detection signal phase place lags behind, utilize formula k=(θ/180) * N/2, round and calculate the number k that data need be shifted.Wherein, N is per cycle sampling number.Then utilize the one-dimension array shift module among the LabVIEW, with the probe deflection signal data that gathers successively mobile k position, can realize the correction that described detection signal phase place is lagged behind.

In the real time nonlinear correction module, as shown in Figure 3.

The first step is utilized formula

N=0 ~ (N/2-1), n is integer, rounds to calculate n corresponding locus i of sampled point in sine sweep, wherein, N is per cycle sampling number, and all locus i are formed an one-dimension array, and described one-dimension array has N/2 element.

Second step, the number m of each locus i in the array that the calculating first step obtains, the number of the probe deflection signal data that namely each locus i is corresponding.Specifically can realize by nested While circulation in the circulation of the For in the software, the counting terminal counting of While circulation is then exported the number m of each locus i: utilize the search one-dimension array module in the software, the position at the place of element i from 0 to (N/2-1) each i in the one-dimension array that retrieval obtains in the first step, if do not find element i, then the counting terminal counting of While circulation is 0, the While circulation stops, and retrieves next element i+1; If found element i, then the counting terminal counting accumulative total 1 of While circulation continues to seek the next position of element i, until search out last position of i, the counting terminal counting of While circulation is m, and the While circulation stops, and retrieves next element i+1.Obtain at last the one-dimension array of N/2 element.

The 3rd step, by the number m of each definite locus i of second step, determine which kind of mapping relations the corresponding probe deflection signal data of each locus i is, then process respectively.At For circulation nested inside construction of condition, utilize "True" " vacation " branched structure of construction of condition to adopt diverse ways to carry out Data correction.At first, utilize the array of indexes module, return respectively the element m of the one-dimension array index position i that second step obtains.

As shown in Figure 3, if m〉0, then be many-one mapping (m〉1, the corresponding a plurality of probe deflection signal datas in same locus) or one to one mapping (m=1), then utilize the embedded For circulation of "True" branched structure of construction of condition, utilize the array of indexes module in the software, m the probe deflection signal data that retrieves the same space position i got average, obtain the size of data (comprised m=1 here, be equivalent to directly with the corresponding data output in locus) after proofread and correct this locus.

If m=0, it then is the situation (i place in locus does not have corresponding probe deflection signal data) that to shine upon, then utilize " vacation " branched structure of construction of condition, utilize array of indexes module in the software to retrieve the probe deflection signal data of previous some i-1 of this locus i and rear 1 i+1, then get the mean value of these two data values as the last correction data of this locus i.

Probe deflection signal after the correction that so just obtains.

Need to prove that above-described embodiment just is used for illustrating technical characterictic of the present invention, be not to limit patent claim of the present invention, but its theory and structure still belongs to patented claim category of the present invention.

Claims (8)

1. A real-time correction method for high-speed atomic force microscopy imaging, characterized in that: comprising carrying out real-time phase correction and real-time nonlinear correction to the probe deflection signal obtained by sinusoidal scanning; The real-time phase correction specifically includes: obtaining the phase lag angle θ of the bimorph through the detection signal of the bimorph, using the phase lag angle θ and the number of sampling points per cycle N to obtain the number of points k of the phase lag, and finally The collected data is sequentially shifted by k bits, that is, the correction of the phase lag of the initial collected data is realized; The real-time nonlinear correction is specifically as follows: firstly, the number of sampling points per cycle N is set, and the spatial position i of each sampling point is determined; secondly, the mapping between the spatial position i of each sampling point and the probe deflection signal is determined The probe deflection signal is corrected according to the mapping relationship. 2. a kind of real-time calibration method for high-speed atomic force micro-imaging according to claim 1, is characterized in that: the number of points k of described phase lag is calculated by following formula: k=(θ/180)×N/2. 3. A kind of real-time correction method for high-speed atomic force microscopic imaging according to claim 1, it is characterized in that: the relation of described mapping comprises: Many-to-one mapping: the same spatial position corresponds to multiple probe deflection signals; One-to-one mapping: one spatial position corresponds to one probe deflection signal; Unable to map: There is no corresponding probe deflection signal at a spatial location. 4. A kind of real-time correction method for high-speed atomic force microscopy imaging according to claim 1 or 3, is characterized in that: For the case of many-to-one mapping, the values collected at the same spatial position are averaged as the corrected data; For the case of one-to-one mapping, the value at the spatial position is directly used as the corrected data; For the situation that cannot be mapped, the average value of the two values adjacent to the spatial position is taken as the corrected data. 5. A kind of real-time calibration method for high-speed atomic force microscopy imaging according to claim 1, characterized in that: the spatial position i, using the formula $i=(-\cos \frac{\mathrm{no}\·\mathrm{\π}}{N/2}+1)\&Center\; Dot;\left(\frac{N}{2\&Center\; Dot;2}\right),\mathrm{no}=0~(N/2-1),$ n is an integer, rounded to calculate the spatial position i corresponding to the nth sampling point in the sinusoidal scan. 6. A real-time correction system for high-speed atomic force microscopy imaging, characterized in that: it includes a real-time phase correction module and a real-time nonlinear correction module; the real-time phase correction module is used to correct the phase lag of the probe deflection signal , the real-time nonlinear correction module is used to perform nonlinear correction on the signal output by the real-time phase correction module. 7. A kind of real-time correction system for high-speed atomic force microscopy imaging according to claim 6, characterized in that: the specific implementation of the real-time phase correction module is as follows: First, the phase lag angle θ of the bimorph is obtained through the detection signal of the bimorph, and the phase lag point k is obtained by using the phase lag angle θ and the number of sampling points per cycle N, and finally the collected data is sequentially shifted by k bits, The correction of the phase lag of the initial acquisition data can be realized. The number of points k is calculated by the following formula: k＝(θ/180)*N/2 For the real-time nonlinear correction module, it is carried out on the basis of phase lag correction, and its working process is as follows: First, for the sinusoidal scan, the spatial position i of each sampling point is determined by setting the number of sampling points per cycle N ;Secondly, determine the mapping relationship between the spatial position i of each sampling point and the probe deflection signal, which includes three mapping relationships: many-to-one mapping, one-to-one mapping and unmapping; For the case of many-to-one mapping, the values collected at the same spatial position are averaged as the corrected data; For the case of one-to-one mapping, the value at the spatial position is directly used as the corrected data; For the situation that cannot be mapped, take the average value of the two values adjacent to the spatial position as the corrected data. 8. A real-time correction system for high-speed atomic force microscopy imaging according to claim 6 or 7, characterized in that: said real-time phase correction module and real-time nonlinear correction module are implemented using LabVIEW software.

Images