CN202096194U - Measuring instrument for intraocular pressure - Google Patents
Measuring instrument for intraocular pressure Download PDFInfo
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- CN202096194U CN202096194U CN2011201060891U CN201120106089U CN202096194U CN 202096194 U CN202096194 U CN 202096194U CN 2011201060891 U CN2011201060891 U CN 2011201060891U CN 201120106089 U CN201120106089 U CN 201120106089U CN 202096194 U CN202096194 U CN 202096194U
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Abstract
The utility model discloses a measuring instrument for intraocular pressures, which comprises an electromagnetic force generating device, an electromagnetic force control device, a pressure measuring probe and an image sensor. The electromagnetic force generating device comprises a coil and a permanent magnet arranged inside the coil. The permanent magnet is connected with the pressure measuring probe. An optical path is arranged inside the pressure measuring probe. The image sensor is arranged at the end of the optical path. The electromagnetic force control device comprises a control module, a pressure control circuit, an electromagnetic drive unit and a current sampling circuit. The control module outputs a pressure control signal to the pressure control circuit. The pressure control circuit outputs a current to the coil. The current sampling circuit samples the field current in the coil. The output terminal of the current sampling circuit is connected with the input terminal of the control module via an A/D converting circuit. The output signal of the image sensor is transmitted to the input terminal of the image acquisition portion of the control module. The measuring instrument is simple, safe and reliable in pressure generation principle and mechanical structure. Meanwhile, the valve of the intraocular pressure is represented by an exciting current and is not measured by a pressure sensor.
Description
Technical field
This utility model is mainly used in the accurate measurement that realizes intraocular pressure and obtains real-time eye fundus image simultaneously; It is a kind of armarium based on FPGA; Be to reduce number of times and the expense of detecting; Be convenient to the instrument of doctor, belong to technical field of medical instruments according to the change diagnosis ophthalmic diseases of survey intraocular pressure value, the optical fundus variation of observing image demonstration in real time and optical fundus optic disc.
Background technology
Medical device technology is the high-tech type of a multidisciplinary intersection, knowledge, fund-intensive.Medical apparatus and instruments is separately or makes up instrument, equipment, utensil, material or other article that are used in human body; Comprise needed software; It is used for body surface and intravital effect is not to obtain with pharmacology, immunology or metabolic means, participates in and rise certain assosting effect but have these means.
FPGA is the abbreviation of field programmable gate array; Be on PLD and CPLD basis, to evolve and the special IC of a kind of semi-custom of coming; With FPGA is the restriction that core had both solved custom circuit, overcomes a limited number of shortcomings of gate circuit of original programming device again.Select FPGA need consider technical factors such as memory size on a density, the sheet, maximum clock frequency, running voltage, maximum IO number of pins and packing forms.
Eyes are most important visual organ of people and animal, and human eye is similar to spheroid, and eyeball is contained tissues such as wall of eyeball, ophthalmic chamber and content, nerve, blood vessel.The tolerant average pressure that wall of eyeball is applied of ophthalmic is an intraocular pressure.Normal person's intraocular pressure is stabilized in 11～12mmHg, fluctuates in time.Under the normal condition, between one day, intraocular pressure has the fluctuation of 2～6mmHg, has 4mmHg between the eyes with interior difference.But varieties of intraocular pressure is excessive harmful to eyes, and the too high optic nerve of then oppressing of intraocular pressure, intraocular pressure are low excessively to cause eyeball to be out of shape.Blinding property ophthalmic such as glaucoma etc. have invisible, and early diagnosis is the key of treatment.And tonometry and examination of ocular fundus are particularly important in ophthalmologic examinationes such as glaucoma.In recent years, the number of suffering from ophthalmic constantly rises.Estimate the year two thousand twenty, the whole world will have nearly 80,000,000 people to suffer from glaucoma, and efficient diagnosis is very important.
Because glaucomatous diagnosis of complex property, single ophthalmology detection architecture can not be made a definite diagnosis, and the ophthalmology detecting instrument can only be measured single parameter at present.Usually utilize tonometer to measure intraocular pressure earlier, utilize ophthalmoscope or fundus camera to observe the optical fundus optic disc again and change, need carry out repeated detection, increased patient's misery and expense.
Tonometer is divided into planishing type, pressure-sinking type and contactless three kinds according to the measuring principle difference.The Goldmann tonometer is the representative of planishing type tonometry; Probe diameter is 3.06mm; Two prisms that substrate is opposite are arranged in the probe, make with the roundel image shift of cornea contact position roundly into two, the intraocular pressure value is that two semicircles are when just contacting; Cornea applanation face diameter is exactly a 3.06mm institute applied pressure value, is the tonometry " goldstandard " of generally acknowledging.This utility model proposes new tonometry system according to the measuring principle basis of Goldmann planishing type.
Glaucomatous diagnosis of complex property, single ophthalmology detection architecture can not be made a definite diagnosis, and the ophthalmology detecting instrument can only be measured single parameter at present.Usually utilize tonometer to measure intraocular pressure earlier, utilize ophthalmoscope or fundus camera to observe the optical fundus optic disc again and change, need carry out repeated detection, increased patient's misery and expense.
Summary of the invention
Technical problem: the purpose of this utility model is based on FPGA and the soft nuclear of Nios II; Provide a kind of pressure to force eyeball deformation; And the device and method of corneal pressurized image and eye fundus image dynamic change record, be used for accurately detecting intraocular pressure value and real-time eye fundus image, clearly presenting images.
Technical scheme:
A kind of tonometry method, step comprises:
1) first electricity consumption magnetically-actuated control pressure measurement probe oppression eyeball makes cornea produce deformation; The cornea applanation image of dynamic change in the acquisition and recording oppression eyeball process again; Obtain the cornea applanation area according to this cornea applanation image at last;
2) electromagnetic force and the exciting current that produces electromagnetic force is big or small linear, and with the force value of exciting current sign oppression eyeball, this force value combines cornea applanation area to obtain the intraocular pressure value;
In the said step 1), the computational methods of cornea applanation area are to begin from cornea applanation image middle, scan connected domain and counting successively from upper and lower, left and right four direction, obtain the valid pixel of this connected domain, promptly obtain image; According to the ratio of this image and material picture, obtain the cornea applanation area again according to following formula;
(image that collects): (material picture)=(cornea applanation area): (material object in the industry standard flattens area).
In the said step 1), the method for solving of cornea applanation image is that (x y) carries out binaryzation, and (x, y), method is to obtain required binary image g with the original image f that collects
In the said step 1), also gather the eye fundus image of dynamic change in the oppression eyeball process; Cornea applanation image and the eye fundus image of gathering dynamic change in the oppression eyeball process are to adopt imageing sensor to collect through double light path.
For said imageing sensor, gather cornea applanation image and eye fundus image by double light path, the image size is respectively 512 pixel *, 512 pixels and 64 pixel *, 64 pixels.
Said iteration threshold method step comprises:
Obtain the maximum gradation value μ of binary image earlier
MAXWith minimum gradation value μ
MIN, make initial threshold T
0=(μ
MAX+ μ
MIN)/2;
Again according to threshold value T
0With image segmentation is prospect and background, obtains both average gray value μ respectively
0And μ
1, obtain new threshold value T then
K=(μ
0+ μ
1)/2;
Last iterative computation T
K+1, until T
KConvergence, i.e. T
K=T
K+1
Said maximum entropy threshold method step comprises:
Suppose that the image size is M * N, by gray value image is divided into background and prospect two parts earlier, the threshold value of cutting apart is T, and gray value is made N0 less than the number of pixels note of threshold value T in the image, and gray value is made N1 greater than the number of pixels note of threshold value T;
If it is ω that the foreground pixel point accounts for the ratio of entire image
0, average gray μ
0The ratio that the background pixel point accounts for entire image is ω
1, average gray is μ
1The average gray of entire image is μ, and inter-class variance is designated as g, then
N
0+N
1＝M×N，ω
0+ω
1＝1、 N
0+N
1＝M×N，ω
0+ω
1＝1，
μ＝ω
0μ
0+ω
1μ
1 μ＝ω
0μ
0+ω
1μ
1
g＝ω
0(μ
0-μ)
2+ω
1(μ
1-μ)
2 g＝ω
0(μ
0-μ)
2+ω
1(μ
1-μ)
2
Use the maximum threshold value T of inter-class variance g as optimal segmenting threshold.
A kind of tonometry appearance that makes said method comprises arrangement for producing electromagnetic force, electromagnetic force control device, pressure measurement probe and imageing sensor;
Said arrangement for producing electromagnetic force comprises the permanent magnet in coil and the coil, and permanent magnet connects the pressure measurement probe;
Be provided with light path in the said pressure measurement probe, imageing sensor is located at the end of light path;
Said electromagnetic force control device comprises control module, pressure control circuit, electromagnetic drive unit and current sampling circuit;
Said control module output pressure control signal is given pressure control circuit, and the pressure control circuit output current is given said coil; Current sampling circuit is sampled to the exciting current in the coil, the input of the outfan of current sampling circuit link control module behind the A/D change-over circuit;
The output signal of imageing sensor is passed to the input of the IMAQ part in the control module.
Said control module is connected with the image transmission circuit, is connected with background PC computer through the image transmission circuit.
Said control module is FPGA, and the core control circuit of this FPGA comprises:
Pressure control module, image processing module, image capture interface, image buffer storage and image coffret; The input of pressure control module connects the outfan of current sampling circuit, and the outfan of pressure control module connects pressure control circuit; The outfan of imageing sensor connects image capture interface, and image transmission circuit connection layout is as coffret;
Said pressure control module, image processing module, image capture interface, image buffer storage and image coffret are connected on the same AVALON bus.
The image frame per second of said imageing sensor is identical with the pressure change rate of pressure controling signal.
Said permanent magnet connects the pressure measurement probe through lever construction; Said lever construction comprises connecting rod and rotating shaft, is connected in the rotating shaft in the middle of the connecting rod; One end of connecting rod connects permanent magnet, and the pull bar other end connects the pressure measurement probe.
Said light path is a double light path.
Beneficial effect: principle and frame for movement that measuring instrument produces pressure are simple and easy and safe and reliable, characterize force value by exciting current, avoid the use of the method that pressure transducer obtains force value.Probe diameter adopts 7.2mm, and pressing face diameter is identical with probe diameter, gained pressure limit: 0～0.48982N, and precision is 0.05g.Real time imaging sensor record cornea applanation image change, and by image processing algorithm calculating pressing area.The absolute transfer rate of usb data is up to 41.4MB/s, and the transfer rate that frame per second is 200, resolution is 512 * 512 eye fundus image is 6.225MB/s, and visual result is accurate.
Description of drawings
Fig. 1 is based on the measuring instrument hardware elementary diagram of FPGA tonometry appearance.
Fig. 2 is based on the measurement measuring instrument framework sketch map of FPGA tonometry appearance,
The 1st, eyeball, the 2nd, double light path, the 3rd, connecting rod, the 4th, imageing sensor, the 5th, pressure measurement probe, the 6th, rotating shaft, F are electromagnetic force.
Fig. 3 is based on the measuring instrument software frame of FPGA tonometry appearance.
The specific embodiment
This tonometry method, step comprises:
1) through the pressure of solenoid actuated frame for movement control probe oppression eyeball, make cornea produce deformation.Simultaneously scioptics utilize the dynamic change of cornea applanation image and eye fundus image in the image recording sensor oppression eyeball process by double light path, obtain the cornea applanation area according to this cornea applanation image;
2) in the size of the power of driving device structure and the external magnetic field be that exciting current is linear in the coil of magnetic core with the electric magnet, characterize the force value that Ampere force obtains with exciting current, this force value combines cornea applanation area to obtain the intraocular pressure value;
Said cornea applanation image carries out image segmentation earlier, and area calculates again.
Owing to be the double light path design, the image size that measuring system needs: 512*512 (25bps) and 64*64 (200bps).Can know that according to the related register of imageing sensor configuration the frame frequency of image controlled by window and blanking depositor jointly.
Said image segmentation adopts thresholding method, comprises iteration threshold method, maximum variance between clusters or maximum entropy threshold method; Corresponding to the varying environment background three kinds of methods being obtained image compares and selects.
The computational methods of said cornea applanation area are to begin from cornea applanation image middle, scan connected domain and counting successively from upper and lower, left and right four direction, obtain the valid pixel of this connected domain; According to image and ratio in kind, obtain the cornea applanation area again.
The method for solving of the image size that measuring system needs is,
The picture frame frequency of the MT9M001 imageing sensor acquiescence that image capture module adopted in this example is 30bps, and valid pixel is 1280*1024.Gather cornea applanation image and eye fundus image by double light path, the related register that imageing sensor need be set through the serial port protocol of special use is provided with the image size that measuring system needs: 512*512 (25bps) and 64*64 (200bps).Can know that according to the related register of imageing sensor configuration the frame frequency of image controlled by window and blanking depositor jointly.
The frame frequency computational methods are following:
Wherein: the individual pixel clock of shutter_width=win_height1+vert_blank=(Reg0 * 09); Row_time=win_width+1+horiz_blank+244=((Reg0 * 04+1)+(Reg0 * 05-19)+244) individual pixel clock; Overhead_time=180 pixel clock; Reset_delay=(the individual pixel clock of 4 * Reg0 * 0C), therefore
CMOS dominant frequency f
ClkBe 24MHz, Reg0 * 05 and Reg0 * 0C use default value, therefore, the value of depositor 0 * 09 only need be set, and just frame per second can be set.The frame per second f of system requirements
RateBe 25fps (512*512) and 200fps (64*64), according to
Calculate, the value of imageing sensor depositor 0 * 09 is respectively 0 * 04F6 and 0 * 00DA.
Because of the different image quality that can influence image of light intensity of imageing sensor working environment, through the pixel gain that depositor 0 * 2B, 0 * 2C, 0 * 2D and 0 * 2E are provided with each each row of row of image separately is set.
Carrying out image segmentation, is that (x finds threshold value T in y), is two parts with image segmentation, and the image after cutting apart does at original image f
Get b
0=0, b
1=1, the image that obtains is exactly required binary image.
By the maximum gradation value μ that obtains image earlier
MAXWith minimum gradation value μ
MIN, make initial threshold T
0=(μ
MAX+ μ
MIN)/2; Again according to threshold value T
0With image segmentation is prospect and background, obtains both average gray value μ respectively
0And μ
1, obtain new threshold value T then
K=(μ
0+ μ
1)/2; Last iterative computation T
K+1, until T
KConvergence, i.e. T
K=T
K+1, T then
KBe the iteration threshold method of threshold value.
Suppose that the image size is M * N, by gray value image is divided into background and prospect two parts earlier, the threshold value of cutting apart is T, and gray value is made N0 less than the number of pixels note of threshold value T in the image, and gray value is made N1 greater than the number of pixels note of threshold value T.And to establish the ratio that the foreground pixel point accounts for entire image be ω
0, its average gray μ
0The ratio that the background pixel point accounts for entire image is ω
1, its average gray is μ
1The average gray of entire image is μ, and inter-class variance is designated as g.Then
N
0+N
1＝M×N，ω
0+ω
1＝1、 N
0+N
1＝M×N，ω
0+ω
1＝1
μ＝ω
0μ
0+ω
1μ
1 μ＝ω
0μ
0+ω
1μ
1
g＝ω
0(μ
0-μ)
2+ω
1(μ
1-μ)
2 g＝ω
0(μ
0-μ)
2+ω
1(μ
1-μ)
2
Make the maximum threshold value T of inter-class variance g be the maximum variance between clusters of the optimal segmenting threshold of being tried to achieve;
Utilize the maximum of image entropy to confirm that threshold value is exactly the maximum entropy threshold method, this method is existing mature technology, not further restriction.
Because the valid pixel (prospect) of cornea pressurized image always is positioned in the middle of the image, and prospect do not have hollow, is special bianry image.
The cornea applanation area is that the bianry image that after image segmentation, obtains carries out area statistics by cubic up and down to scanning connected domain and counting, by image and ratio in kind contrast calculating, obtains the cornea applanation area again.
A kind of tonometry appearance that uses said method, its control core module are realized that by FPGA the core control circuit of this FPGA comprises soft nuclear design of Nios II and fpga logic design;
Said Nios II is soft, and the nuclear design comprises pressure control module and image processing module; The pressure control module generates pressure controling signal through the pressure of feedback cornea, drives pressure measurement probe oppression eyeball; Image processing module carries out image segmentation and area calculates;
Said fpga logic design comprises image capture interface, image buffer storage and image coffret; The output of imageing sensor connects image capture interface, and image transmission circuit connection layout is as coffret;
Said pressure control module, image processing module, image capture interface, image buffer storage and image coffret are connected on the same AVALON bus.
Said image transmission circuit is the image transmission circuit that meets the USB standard.
Said pressure control circuit comprises analog to digital conversion circuit and D/A converting circuit;
Control module output pressure control signal is given D/A converting circuit, and D/A converting circuit output exciting current is given the coil of electromagnetic drive unit; The exciting current information that collects is given analog to digital conversion circuit, exports to control module to this pressure information by analog to digital conversion circuit again.
In the present technique scheme, be core control circuit with FPGA, peripheral circuit mainly is divided into: pressure control circuit, IMAQ memory circuit and USB transmission circuit.And the logic control of application hardware language realization measuring instrument, realization speed is fast, motility is strong.Systems soft ware is designed to main core with the FPGA design with USB.
Wherein measurement module comprises pressure measurement probe, imageing sensor, frame for movement and electric magnet etc.Measuring instrument is used for oppression eyeball and makes cornea produce deformation through produced the pressure of a linear growth by FPGA control electric magnet.Size through exciting current characterizes force value, and scheme is novel.By the dynamic change of cornea applanation image and eye fundus image in this process of image recording sensor, use image processing techniques to calculate the cornea applanation area simultaneously, obtain intraocular pressure in conjunction with corresponding force value.Measuring instrument can obtain eye fundus image and be uploaded to main frame and show and preserve.
Pressure control unit is used to control the pressure size that electric magnet produces, and concrete the realization is to pass through bus regulation and control peripheral circuit state by FPGA, and peripheral circuit feeds back to FPGA through bus.Pressure control circuit is controlled the variation of exciting current with voltage, realizes the accurate feedback control of pressure.The IMAQ memory circuit is used to obtain real time imaging, and makes the image buffer memory with SDRAM, solves on the sheet problems such as the too small and collection of buffer memory, transmission speed do not match.The key of the real-time Transmission image operational efficiency of measuring instrument is the speed of data transmission bauds.Transmission speed depends on hardware interface to a great extent.USB is as common data transmission channel, and its very strong versatility has reduced development difficulty and cost.The image transmission circuit is interface with USB, and highly versatile, speed are fast, realizes uploading in real time of eye fundus image.
The FPGA design is interrelated through the Avalon bus by fpga logic design and the soft nuclear design of Nios II.The CPU of Nios II system comprises three kinds of allocation plans: quick type, standard type and economy.Fpga logic is accomplished the control to peripheral hardwares such as each imageing sensor and SDRAM as the key control unit of bottom.The soft nuclear of Nios II adopts the algorithm computation cornea applanation area of Flame Image Process such as image segmentation, and the generation of controlled pressure and variation.
The image segmentation scheme is utilized thresholding method.The characteristic that thresholding method often has characteristic to comprise gray scale or the color property of original image, obtained by original gray scale or value of color conversion.Select three kinds of iteration threshold methods commonly used, maximum variance between clusters, maximum entropy threshold methods to handle image, compare through rectangular histogram.Because the particularity of the eye fundus image of gathering, the valid pixel of image is a prospect, always be positioned in the middle of the image, and prospect does not have hollow, and area calculating can be with the most intermediary prospect as a connected domain, the number of reuse scanning method calculating valid pixel.
The USB program comprises firmware program, driver and application program three parts, is used to be provided with image size, frame per second and gain, shows in real time and preserves eye fundus image, and IMAQ is started and stop control, accomplishes uploading in real time of eye fundus image.
Below in conjunction with the accompanying drawing and the specific embodiment present technique scheme is further specified:
The complete tonometry appearance based on FPGA of one cover like accompanying drawing 1 with shown in the accompanying drawing 3.
A, fpga core control circuit are the maincenters of measuring instrument, and pressure is controlled through I
2The C bus is sent digital voltage to analog-digital chip, converts aanalogvoltage to, with since change electromagnetic force.Order about electric magnet through pressure control circuit control exciting current size and produce an electromagnetic force that increases in time, by modulus conversion chip with the electromagnetic force sampling and pass through I
2The C bus feeds back to FPGA, realizes the closed loop control of electromagnetic force, adjusts force value in real time.This electromagnetic force drives pressure measurement probe oppression eyeball through the effect of frame for movements such as lever, makes cornea produce deformation gradually.The dynamic change of cornea applanation image and eye fundus image in the image recording sensor compressing process simultaneously.
The suffer oppression dynamic changing process of image and eye fundus image of the cornea of b, image acquisition circuit record stores the image that collects in the fpga logic design in the image buffer storage through the fpga core control circuit, solves not matching of IMAQ and transmission speed.Image transmission transfers to PC with data through image transmission circuit and highly versatile, fireballing USB cable.
The algorithm of Flame Image Process such as cornea Threshold Segmentation and area calculating is accomplished in c, the soft nuclear design of Nios II.The USB firmware is to transmit upper PC instruction and transmit the optical fundus dynamic image data that the fpga core control circuit is uploaded through firmware program, driver and application program, and display image, preservation image are realized man-machine interaction in real time.
With reference to figure 2
Said permanent magnet connects the pressure measurement probe through lever construction; Said lever construction comprises connecting rod and rotating shaft, is connected in the rotating shaft in the middle of the connecting rod; One end of connecting rod connects permanent magnet, and the pull bar other end connects the pressure measurement probe.
Said light path is a double light path, and this double light path is made up of two convex lenss and a reflecting mirror, obtains eye fundus image by bigger convex lens, obtains the cornea applanation image by less convex lens.The corresponding eye fundus image of 512 pixel *, 512 pixel portion of imageing sensor, the corresponding cornea applanation image of 64 pixel *, 64 pixel portion.
Realize principle
The measurement structure of measuring instrument combines to realize driving the power of tonometry and the tracking collection of image with the fpga core control circuit.Measuring instrument need produce the external force that can accurately control and flatten cornea, and this external force is the exciting current size through the control DM.Solenoid actuated produces mechanical movement according to the effect that the current in the magnetic field receives power.In electromagnetic drive unit, with the magnetic core of permanent magnet as coil, then coil is in the external magnetic field that permanent magnet produces.When passing to exciting current in the coil,, produce relative motion thereby make between coil and Magnet because the existence of external magnetic field makes coil receive the effect of Ampere force.Keep magnetic direction constant, change the direction of exciting current in the coil, can change the direction of Ampere force.Apply the exciting current of different directions to coil, can realize the different direction of motion of popping one's head in respectively.Exciting current is linear in the size of probe generation Ampere force and the coil.The exciting current of control coil just can accurately be controlled the pressure that the pressure measurement probe produces.
Survey intraocular pressure and need straight line pressure, select solenoid electromagnet,, select loricate solenoid electromagnet for use in order to increase electromagnetic force.Flexible for realizing probe; Replace its armature with permanent magnet, with coil as movable stressed member, according to four fundamental equations such as electromagnetic attraction, magnetic potential, voltage and heatings; Combine with ANSYS emulation through Theoretical Calculation, draw the electromagnet structure parameter that adheres to specification.
Measuring instrument need pass through I
2C control exciting current comes DM work, and the pressure control circuit important component part is the current drives part, and is higher to the size and the required precision of output current.Selection is made up of amplifier, audion, sampling resistor and load resistance (being electromagnet coil) etc.FPGA in order to the control that electromagnetic force changes, feeds back FPGA with electromagnetic force through analog-digital chip gained aanalogvoltage simultaneously again, to realize closed loop control.
Image acquisition circuit needs imageing sensor is carried out type selecting.Two types of essential processing technique of CCD and CMOS are analyzed.To practice thrift the measuring instrument cost and to reduce the power consumption consideration, select cmos image sensor.Consider real-time images acquired, data volume is big, and buffer memory can not satisfy on the sheet, needs the outer large capacity cache of expansion sheet.According to cost performance and designing requirement, static RAM (SRAM), dynamic ram, Flash ROM are selected suitable image buffer storage, the SDRAM model is H57V2562GTR-75C.
FPGA and cmos image sensor realization function comprise to be provided the CMOS work clock, the CMOS mode of operation is set and receives the cmos image data, and connection line realizes that picture frame is synchronous.Through confirming that imageing sensor is provided with parameters such as sequential dateout sequential, frame per second setting and gain are provided with to gathering.
The image transmission circuit mainly uses Slave fifo mode among the EZ-USB FX2, and peripheral control unit is FPGA.When this mode of operation, the CPU of FX2 does not participate in transfer of data directly, but with its size FIFO that is 4KB as the data channel between FPGA and the USB.FPGA and USB can directly share these FIFO, and allow FPGA that data are transferred to FIFO continuously, after FIFO writes completely, submit to USB automatically, can fine solution USB fast mode transmission optical fundus dynamic change Time Bandwidth problem.
Image stores FIFO buffer memory and SDRAM large capacity cache on the sheet.The design of sdram controller is that storage is crucial, comprises measuring instrument control interface, command analysis module, command response module and data path module.
Measuring instrument customization Nios II CPU, interpolation IP kernel, interpolation I
2The C EBI, add the User Defined peripheral hardware, the base address be set and interrupt priority level customizes the soft nuclear of Nios II.Adopt the soft nuclear design of Nios II controlled pressure to produce and the processing image, mainly divide two modules: pressure control, Flame Image Process.
Pressure control promptly passing through I
2C bus feedback control electric magnet produces accurate electromagnetic force, drives pressure measurement probe oppression eyeball.The image frame per second of measuring intraocular pressure is 200, and pressure change rate also is required to be 200, and the intervalometer cycle was made as 1/200 second.Fpga core utilizes intervalometer interruption branch to pass through I 200 times
2The C bus is sent digital voltage and is given analog-digital chip, makes it to produce the magnitude of voltage of 200 linear growths, converts current value rear drive electric magnet to.Write analog-digital chip through main frame force value is set, read modulus conversion chip by main frame again and obtain force value.
Flame Image Process is mainly calculated through image segmentation, areameter and is carried out Flame Image Process.Image segmentation adopts and realizes simply, amount of calculation is little, the thresholding method of stable performance.This measuring instrument selects three kinds of iteration threshold method, maximum variance between clusters, maximum entropy threshold methods commonly used to cut apart respectively, can show rectangular histogram in real time.Through the analogy of three kinds of method principles, iterative method is applicable to bimodal apparent in view, the image that the lowest point is darker of rectangular histogram, and can obtain satisfactory result fast; But bimodal not obvious to rectangular histogram, or image object and background ratio difference great disparity, iterative method is not as maximum variance between clusters; But maximum variance between clusters is defectiveness also, when the size of target in the image and background is very little, and poor.Area calculates and to begin from the image middle, from four direction single pass connected domain and counting up and down, obtains the valid pixel of this connected domain, according to image and ratio in kind, obtains the cornea applanation area again.
The eye fundus image transmission procedure comprises Design of Firmware, Driver Design, application programming and the test of image transfer rate.Main frame to USB device order control, and reads the data of specified quantity from USB device through driver, supplies with main frame and does further date processing, demonstration and preservation etc.
Can realize that through this utility model intuitive and reliable tonometry and optical fundus detect in real time, provide ophthalmic two important diagnostic foundations simultaneously.
Claims (6)
1. a tonometry appearance is characterized in that comprising arrangement for producing electromagnetic force, electromagnetic force control device, pressure measurement probe and imageing sensor;
Said arrangement for producing electromagnetic force comprises the permanent magnet in coil and the coil, and permanent magnet connects the pressure measurement probe;
Be provided with light path in the said pressure measurement probe, imageing sensor is located at the end of light path;
Said electromagnetic force control device comprises control module, pressure control circuit, electromagnetic drive unit and current sampling circuit;
Said control module output pressure control signal is given pressure control circuit, and the pressure control circuit output current is given said coil; Current sampling circuit is sampled to the exciting current in the coil, the input of the outfan of current sampling circuit link control module behind the A/D change-over circuit;
The output signal of imageing sensor is passed to the input of IMAQ part in the control module.
2. tonometry appearance according to claim 1 is characterized in that said control module is connected with the image transmission circuit, is connected with background PC computer through the image transmission circuit.
3. tonometry appearance according to claim 2 is characterized in that said control module is FPGA, and the core control circuit of this FPGA comprises: pressure control module, image processing module, image capture interface, image buffer storage and image coffret; The input of pressure control module connects the outfan of current sampling circuit, and the outfan of pressure control module connects pressure control circuit; The outfan of imageing sensor connects image capture interface, and image transmission circuit connection layout is as coffret; Said pressure control module, image processing module, image capture interface, image buffer storage and image coffret are connected on the same AVALON bus.
4. tonometry appearance according to claim 1 is characterized in that the pressure change rate of image frame per second and pressure controling signal of said imageing sensor is identical.
5. tonometry appearance according to claim 1 is characterized in that said permanent magnet connects the pressure measurement probe through lever construction; Said lever construction comprises connecting rod and rotating shaft, is connected in the rotating shaft in the middle of the connecting rod; One end of connecting rod connects permanent magnet, and the pull bar other end connects the pressure measurement probe.
6. tonometry appearance according to claim 1 is characterized in that said light path is a double light path.
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| CN2011201060891U CN202096194U (en) | 2011-04-12 | 2011-04-12 | Measuring instrument for intraocular pressure |
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| CN202096194U true CN202096194U (en) | 2012-01-04 |
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| CN2011201060891U Expired - Fee Related CN202096194U (en) | 2011-04-12 | 2011-04-12 | Measuring instrument for intraocular pressure |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102813501A (en) * | 2012-08-06 | 2012-12-12 | 淮南师范学院 | Dynamic intraocular pressure measuring device and method for controlling probe to be coaxial with eyeball |
| CN105342551A (en) * | 2015-10-23 | 2016-02-24 | 济南三维医疗器械有限公司 | Instrument for detecting cornea biomechanics and application method of instrument |
| CN112383309A (en) * | 2020-11-13 | 2021-02-19 | 广东澳鸿科技有限公司 | Analog-to-digital conversion circuit of magnetoelectric revolution speed sensor |
-
2011
- 2011-04-12 CN CN2011201060891U patent/CN202096194U/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102813501A (en) * | 2012-08-06 | 2012-12-12 | 淮南师范学院 | Dynamic intraocular pressure measuring device and method for controlling probe to be coaxial with eyeball |
| CN102813501B (en) * | 2012-08-06 | 2014-04-02 | 淮南师范学院 | Dynamic intraocular pressure measuring device and method for controlling probe to be coaxial with eyeball |
| CN105342551A (en) * | 2015-10-23 | 2016-02-24 | 济南三维医疗器械有限公司 | Instrument for detecting cornea biomechanics and application method of instrument |
| CN105342551B (en) * | 2015-10-23 | 2019-03-19 | 济南三维医疗器械有限公司 | A kind of biological mechanics detecting instrument and its application method |
| CN112383309A (en) * | 2020-11-13 | 2021-02-19 | 广东澳鸿科技有限公司 | Analog-to-digital conversion circuit of magnetoelectric revolution speed sensor |
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