Image point precision and acquisition depth test method based on optical coherence tomography imaging

Abstract

The application discloses a method for testing image point precision and collection depth based on optical coherence tomography, which comprises the following steps: 1) placing a collection trapezoidal test card in an OCT three-dimensional subsurface structure image collection window; 2) performing two-dimensional image section scanning from the acute angle side of the trapezoidal test card along the right angle side in the direction from thin to thick, and collecting two-dimensional image data; 3) generating a three-dimensional OCT image, magnifying the collected line pair calibration plate pattern to vertically fill a display screen, and checking the row and column positions of the clear resolution line of the line pair calibration plate pattern; 4) collecting the longitudinal depth pixel number from the acute angle side of the trapezoidal test card, and calculating a three-dimensional longitudinal image point precision value; 5) collecting the transverse depth pixel number from the acute angle side of the trapezoidal test card, and calculating a three-dimensional transverse image point precision value; and 6) collecting the maximum distance of the clear resolution line from the acute angle side of the trapezoidal test card, calculating the maximum depth of the clear resolution line, and obtaining an effective collection depth value; the application can calculate the image point precision and the effective collection depth of an OCT system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of image point precision and acquisition depth testing, and particularly relates to an image point precision and acquisition depth testing method based on optical coherence tomography (OCT). BACKGROUND

[0002] With the development of social economy, biometric applications are becoming more and more widely used. Traditional identity recognition methods are based on knowledge (password, username, etc.) and based on tokens (ID card, key, etc.), which are easy to be forged and forgotten. The biometric identity recognition method based on biological characteristics has the characteristics of universality, uniqueness, stability and collectability. Fingerprint is one of the most commonly used biological characteristics in the biometric recognition method, which has the advantages of easy collection and not easy to lose, and is applied to many places.

[0003] Fingerprint has internal fingerprint and external fingerprint. The internal fingerprint is located between the dermis layer and the epidermis layer, that is, the papillary layer, which is the source of the fingerprint structure. The external fingerprint is located in the epidermis layer, and the finger is easy to be wet, wear and easy to be forged. The internal fingerprint does not have these concerns, and it is not easy to be deceived by fake fingerprints. The traditional fingerprint collection system can only collect external fingerprints. Optical coherence tomography is a non-invasive, non-contact and non-invasive technology that can collect internal fingerprints. Compared with the traditional fingerprint collection system, OCT can obtain subcutaneous fingerprints, which will have higher security and stability.

[0004] The image point precision and acquisition depth of different OCT systems are different. An image point precision and acquisition depth testing method based on OCT is proposed to test the image point precision and acquisition depth of the OCT system to measure the performance of the system.

[0005] OCT image point precision and acquisition depth testing: image point precision is to place the OCT test card in the three-dimensional subcutaneous structure image acquisition window, make two-dimensional image cross-section scanning, collect two-dimensional image data, and generate three-dimensional body data of the test card. The number of vertical depth pixels of the test card is collected, and the three-dimensional vertical image point precision value is calculated according to the formula. The number of horizontal depth pixels of the test card is collected, and the three-dimensional horizontal image point precision value is calculated according to the formula. The acquisition depth is to place the OCT test card in the three-dimensional subcutaneous structure image acquisition window, make two-dimensional image cross-section scanning, collect depth data, and generate three-dimensional body data of the test card. The maximum distance of the clear resolution line of the test card is collected, the maximum depth of the clear resolution line is calculated according to the formula, and the effective acquisition depth value is obtained. SUMMARY

[0006] In order to overcome the technical deficiencies of the existing OCT system in image point precision and acquisition depth, the present application provides an image point precision and acquisition depth testing method based on optical coherence tomography. The present application has strong robustness, high efficiency and high precision, and can obtain the image point precision and effective acquisition depth of the three-dimensional body data collected by the OCT system.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0008] The image point precision and acquisition depth testing method based on optical coherence tomography comprises the following steps:

[0009] 1) Place the acquisition trapezoidal test card in the OCT three-dimensional subcutaneous structure image acquisition window.

[0010] 2) From the acute angle side of the trapezoidal test card, make a two-dimensional image cross-section scan along the right angle side from thin to thick, and collect two-dimensional image data.

[0011] 3) Generate a three-dimensional OCT image, enlarge the collected line pair calibration plate pattern to vertically fill the display screen, and check the row and column positions of the clear resolution line of the line pair calibration plate pattern.

[0012] 4) Collect the longitudinal depth pixel number from the acute angle side of the trapezoidal test card, and calculate the three-dimensional longitudinal image point precision value according to the formula.

[0013] 5) Collect the transverse depth pixel number from the acute angle side of the trapezoidal test card, and calculate the three-dimensional transverse image point precision value according to the formula.

[0014] 6) Collect the maximum distance of the clear resolution line from the acute angle side of the trapezoidal test card, calculate the maximum depth of the clear resolution line according to the formula, and obtain the effective acquisition depth value.

[0015] Further, the step 1) comprises the following steps:

[0016] (11) Design a trapezoidal structure;

[0017] (12) Design a line pair calibration plate for calculating the image point precision and effective depth value of the collected three-dimensional body data;

[0018] (13) Put the line pair calibration plate into the trapezoidal structure and stick it with glue;

[0019] (14) Put the prepared gelatin solution into the trapezoidal test card;

[0020] (15) Place the trapezoidal test card in the three-dimensional subcutaneous structure image acquisition window.

[0021] Further, the step 2) comprises the following steps:

[0022] (21) start the test system;

[0023] (22) scan the two-dimensional image section from the sharp edge of the trapezoidal test card along the right angle edge from thin to thick, and collect two-dimensional image data.

[0024] Further, the step 3) comprises the following steps:

[0025] (31) denoise the two-dimensional section image;

[0026] (32) reconstruct the denoised two-dimensional section image into three-dimensional volume data;

[0027] (33) check the row and column positions of the clear resolution lines of the line pair calibration plate pattern.

[0028] Further, the step 4) comprises the following steps:

[0029] Collect the longitudinal depth pixel number from the sharp angle edge of the trapezoidal test card, and calculate the three-dimensional longitudinal image point accuracy value according to formula (1), that is,

[0030]

[0031] In the formula:

[0032] d──image point accuracy (unit: um / pixel);

[0033] Mi──the longitudinal depth pixel number of the first row 1mm from the sharp angle edge of the trapezoidal test card;

[0034] α──OCT collection trapezoidal test card angle.

[0035] Further, the step 5) comprises the following steps:

[0036] Collect the transverse depth pixel number from the sharp angle edge of the trapezoidal test card, and calculate the three-dimensional transverse image point accuracy value according to formula (2), that is,

[0037]

[0038] In the formula:

[0039] d──image point accuracy (unit: um / pixel);

[0040] Mi──the transverse depth pixel number of the first row 1mm from the sharp angle edge of the trapezoidal test card;

[0041] α──OCT collection trapezoidal test card angle.

[0042] Further, the step 6) comprises the following steps:

[0043] The maximum distance of the clear resolution line from the acute angle edge of the trapezoidal test card is collected, the maximum depth of the clear resolution line is calculated according to formula (3), and the effective collection depth value is obtained, that is

[0044] h=N1*sin a (3)

[0045] In the formula,

[0046] h is the effective collection depth;

[0047] N1 is the maximum distance of the clear resolution line from the acute angle edge of the trapezoidal test card;

[0048] a is the included angle of the OCT collection trapezoidal test card.

[0049] The working principle of the present application is that the OCT data of the trapezoidal test card is collected by OCT, three-dimensional body data is formed after denoising, the maximum distance of the clear resolution line from the acute edge of the trapezoidal test card can be clearly obtained, and the point accuracy of the OCT measured image and the effective depth value of the collection can be calculated by using the information such as the acute angle of the trapezoidal structure.

[0050] The present application has the advantages that the effective depth of the collection can be conveniently measured by the designed trapezoidal structure and the line pair calibration plate, the maximum distance of the clear resolution line from the acute edge of the trapezoidal test card and the image point accuracy can be clearly obtained by the line pair calibration plate, then the two are combined to collect two-dimensional image data on the OCT device, three-dimensional body data can be obtained by processing, and finally the point accuracy of the OCT system measured image and the effective depth value of the collection can be conveniently calculated, and the calculation efficiency is high. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 It is the image point accuracy and collection depth step flow chart obtained by the method of the present application.

[0052] Figures 2a-2b It is a trapezoidal structure provided by an embodiment of the present application, wherein Figure 2a It is the trapezoidal structure as a whole, Figure 2b It is the trapezoidal structure split.

[0053] Figure 3 It is a schematic diagram of the specifications of the side plate triangle in an embodiment of the present application.

[0054] Figure 4 It is a schematic diagram of the pattern of the line pair calibration plate in an embodiment of the present application.

[0055] Figure 5 It is the specifications of the line pair calibration plate in an embodiment of the present application. DETAILED DESCRIPTION

[0056] The application will be further described below in conjunction with the drawings and embodiments:

[0057] Referring to Figure 1 , the image point accuracy and depth test method based on optical coherence tomography includes the following steps:

[0058] 1) Place the depth test card in the OCT three-dimensional subcutaneous structure image acquisition window, and the processing steps are as follows:

[0059] (11) Design a trapezoidal structure, and the overall structure and split structure are shown in Figure 2a and Figure 2b . The trapezoidal structure is composed of a line pair calibration plate, a glass cover plate 1, a glass cover plate 2, gelatin, and a side plate. The line pair calibration plate, the glass cover plate 1, the glass cover plate 2, and the side plate are assembled and filled with gelatin inside. The side plate triangle is shown in Figure 3 , the side plate triangle has a right angle side a of 6.4 mm, a right angle side b of 20.0 mm, an oblique side c of 21.0 mm, and a thickness of 2.0 mm;

[0060] (12) Design a line pair calibration plate, and the line pair calibration plate pattern schematic diagram is shown in Figure 3 . The pattern specification and pattern specification are as follows: the line pair calibration plate pattern specification is 16 mm x 16 mm, each square size is 1 mm x 1 mm, the number of line pairs is 16 x 16, the line width is 0.05 mm, the line pair calibration plate position is coincident with the acute angle side without digital annotation, see Figure 3 and Figure 5 ; the line pair calibration plate pattern specification is that the first column has a line width of 0.05 mm and a line direction of cross, the second column has no line width and line direction, the third column has a line width of 0.10 mm and a line direction of horizontal, the fourth column has a line width of 0.10 mm and a line direction of vertical, the fifth column has a line width of 0.05 mm and a line direction of horizontal, the sixth column has a line width of 0.05 mm and a line direction of vertical, the seventh column has a line width of 0.02 mm and a line direction of horizontal, the eighth column has a line width of 0.02 mm and a line direction of vertical, and the ninth to sixteenth columns repeat the patterns of the first to eighth columns as shown in Figure 4 ;

[0061] (13) Place the line pair calibration plate as shown in Figure 4 on the glass cover plate 2 in the trapezoidal structure, and stick it with 502 glue as shown in Figure 5 ;

[0062] (14) Place the prepared gelatin solution in the trapezoidal test card, and the specific steps are as follows:

[0063] (141) To make the gelatin solution, an electronic balance is used to weigh the gelatin. First, turn on the electronic balance and heat it to the working temperature, then use the given 200g weight to calibrate, and after calibration, weigh 12g and 24g of gelatin;

[0064] (142) Measure 100ml deionized water with a measuring cylinder;

[0065] (143) Respectively, 100ml deionized water is introduced into the beaker containing 12g and 24g gelatin with a glass rod;

[0066] (144) Fill 1 / 2 of the ultrasonic cleaner with water, and perform water bath at 65℃ and ultrasonic dissolution, and use a glass rod to stir to accelerate the dissolution of gelatin, to obtain a gelatin solution;

[0067] (145) Different concentrations of gelatin solution are respectively filled into two trapezoidal test cards with a syringe, and try not to generate bubbles during filling, otherwise it will affect the experimental results;

[0068] (15) Place the glass cover plate 2 of the trapezoidal test card on the prism surface of the OCT sample collection arm.

[0069] 2) Data acquisition is performed on the trapezoidal test card obtained according to step 1), and two-dimensional image data is collected by scanning the two-dimensional image section from the thin to thick direction along the right angle edge of the trapezoidal test card starting from the acute angle edge, including the following steps:

[0070] (21) Start the test system;

[0071] (22) Scan the two-dimensional image section from the thin to thick direction along the right angle edge b of the trapezoidal test card, and collect two-dimensional image section data.

[0072] 3) According to the two-dimensional image section data obtained in step 2), generate a three-dimensional OCT image, and magnify the collected line pair calibration card pattern to vertically fill the display screen, and check the row and column positions of the clear resolution lines of the line pair calibration plate pattern, including the following steps:

[0073] (31) Denoise the two-dimensional section image;

[0074] (32) Reconstruct the denoised two-dimensional section image into three-dimensional volume data;

[0075] (33) Check the row and column positions of the clear resolution lines of the line pair calibration plate pattern.

[0076] 4) According to the row and column positions of the clear resolution lines of the line pair calibration plate pattern obtained in step 33), calculate the three-dimensional longitudinal image point precision value, specifically including:

[0077] Collect the longitudinal depth pixel number from the acute angle edge of the trapezoidal test card, and calculate the three-dimensional longitudinal image point precision value according to formula (1), that is,

[0078]

[0079] In the formula:

[0080] d - image point accuracy (unit: um / pixel);

[0081] Mi - longitudinal depth pixel number of the first row 1mm from the acute angle side of the trapezoidal test card;

[0082] α - OCT collection trapezoidal test card included angle.

[0083] 5) According to the row and column positions of the clear resolution line of the line pair calibration plate pattern obtained in step 33), the three-dimensional lateral image point accuracy value is calculated, specifically including:

[0084] The lateral depth pixel number from the acute angle side of the trapezoidal test card is collected, and the three-dimensional lateral image point accuracy value is calculated according to formula (2), that is,

[0085]

[0086] In the formula:

[0087] d - image point accuracy (unit: um / pixel);

[0088] Mi - lateral depth pixel number of the first row 1mm from the acute angle side of the trapezoidal test card;

[0089] α - OCT collection trapezoidal test card included angle.

[0090] 6) According to the row and column positions of the clear resolution line of the line pair calibration plate pattern obtained in step 33), the maximum depth of the clear resolution line is calculated, and the effective collection depth value is obtained, including the following steps:

[0091] The maximum distance of the clear resolution line from the acute angle side of the trapezoidal test card is collected, the maximum depth of the clear resolution line is calculated according to formula (3), and the effective collection depth value is obtained, that is,

[0092] h = Ni * sin α (3)

[0093] In the formula:

[0094] h - effective collection depth;

[0095] Ni - maximum distance of the clear resolution line from the acute angle side of the trapezoidal test card;

[0096] α - OCT collection trapezoidal test card included angle.

[0097] The content described in the embodiments of the present specification is only a list of implementation forms of the inventive concept, and the protection scope of the present application should not be regarded as limited to the specific forms stated in the embodiments, and the protection scope of the present application also extends to equivalent technical means that can be thought of by those skilled in the art according to the inventive concept.

Claims

1. A method for testing the point precision and the acquisition depth of an image based on optical coherence tomography, characterized in that, It comprises the following steps: 1) Place the trapezoidal test card in the OCT three-dimensional subcutaneous structure image acquisition window; it comprises the following steps: (11) Design a trapezoidal structure; wherein the trapezoidal structure is composed of a line pair calibration plate, a first glass cover plate, a second glass cover plate, gelatin and a side plate, the line pair calibration plate, the first glass cover plate, the second glass cover plate and the side plate are assembled and filled with gelatin inside; (12) Design a line pair calibration plate to calculate the image point accuracy and the effective depth value of the collected three-dimensional body data; (13) Put the line pair calibration plate into the trapezoidal structure and stick it with glue; (14) Put the prepared gelatin solution into the trapezoidal test card; (15) Place the trapezoidal test card in the three-dimensional subcutaneous structure image acquisition window; 2) From the acute angle edge of the trapezoidal test card, make a two-dimensional image cross-section scan along the right angle edge from thin to thick, and collect two-dimensional image data; 3) Generate a three-dimensional OCT image, enlarge the line pair calibration plate pattern to be perpendicular to the display screen, and check the row and column positions of the clear resolution line of the line pair calibration plate pattern; 4) Collect the longitudinal depth pixel number from the acute angle edge of the trapezoidal test card, calculate the three-dimensional longitudinal image point accuracy value according to formula (1), that is, (1) In the formula: d──image point accuracy (unit: um / pixel); Mi──the longitudinal depth pixel number of the first row 1mm from the acute angle edge of the trapezoidal test card; α──OCT acquisition trapezoidal test card angle; 5) Collect the transverse depth pixel number from the acute angle edge of the trapezoidal test card, calculate the three-dimensional transverse image point accuracy value according to formula (2), that is, (2) In the formula: d──image point accuracy (unit: um / pixel); α──OCT acquisition trapezoidal test card angle; - the number of horizontal depth pixels of the 1st row at 1 mm from the acute angle side of the trapezoidal test card; 6) Collect the maximum distance of the clear resolution line from the acute angle edge of the trapezoidal test card, calculate the maximum depth of the clear resolution line according to formula (3), and obtain the effective acquisition depth value, that is, (3) In the formula: α──OCT acquisition trapezoidal test card angle; h ──effective acquisition depth; Ni──the maximum distance of the clear resolution line from the acute angle edge of the trapezoidal test card.

2. The optical coherence tomography based image dot precision and collection depth test method of claim 1, wherein, The step 2) comprises the following steps: (21) Start the test system; (22) From the acute edge of the trapezoidal test card, make a two-dimensional image cross-section scan along the right angle edge from thin to thick, and collect two-dimensional image data.

3. The optical coherence tomography based image dot precision and collection depth test method of claim 1, wherein, The step 3) comprises the following steps: (31) Denoise the two-dimensional cross-section image; (32) Reconstruct the denoised two-dimensional cross-section image into three-dimensional body data; (33) Check the row and column positions of the clear resolution line of the line pair calibration plate pattern.

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