KR102352116B1 - The method of calibration of lens-free photon sensor pixel array by evaluating its characteristic - Google Patents

Abstract

The present invention relates to a characteristic evaluation and correction method of an optical sensor array, and the correction method through characteristic evaluation of the optical sensor array according to the present invention receives a collection characteristic value of the optical sensor array for a standard light source having a certain characteristic value as input extracting a first correction value of the collection characteristic value; receiving a collection characteristic value of the photosensor array with respect to the light source in the application environment and extracting a second correction value of the characteristic value of the light source in the application environment; and calculating a correction value for an application environment of the photosensor array by using the first correction value and the second correction value. According to the present invention, it is possible to prepare a test and calibration standard for securing the measurement reliability of the optical sensor array applied to various environments, and since the reliability range of the measured value can be grasped, the actual bio/medical application user makes the final decision In doing so, potential judgment errors can be reduced.

Description

{The method of calibration of lens-free photon sensor pixel array by evaluating its characteristic}

The present invention relates to a method for evaluating and correcting characteristics of an optical sensor array, and more particularly, to a method for improving reliability through correction of measurement values of an optical sensor array.

Until now, the largest application fields of image sensors (CCD, CMOS image sensor) have been in the smartphone and digital camera markets. The structure of these camera modules is composed of an external optical lens unit, an IR filter unit, and an image sensor. In the color filter layer inside the conventional CMOS and CCD image sensors, the R, G, and B filters are arranged in a uniform pattern for each pixel, and according to human visual characteristics, G is 50% and R and B are 25% each. This is called the Bayer pattern. As such, each pixel of the actual image sensor can detect only one color among R, G, and B, but in the camera image we see, the entire color of R, G, and B is displayed for each pixel. This is possible because the color is configured by interpolating the color values of neighboring cells for each pixel in software. Various algorithms, such as ISO evaluation method standards and image signal processing, have been developed for these image characteristics evaluation and correction methods.

However, in recent years, as sensor technology develops, cases of applying each of the optical sensor arrays without an external optical lens unit as a measuring device are increasing. In particular, it is used in bio photoreaction measuring devices, lens-free microscopes, in vitro diagnostic devices using photoreaction measurement of immunochromatography, multiplexing devices for DNA analysis, biosignal measuring devices for healthcare, implanted or patch type medical measuring devices, etc. However, in general, the characteristics of an image sensor produced in a semiconductor fab are different for each sensor position on the wafer, and even within the same sensor, each pixel has different characteristics. Accordingly, reliability of the measurement accuracy for each pixel of the optical sensor array becomes an important issue in such a diagnostic device, and it is necessary to set up a measurement device suitable for this, and to improve the accuracy through an array characteristic test method and correction.

In the present invention, the characteristics of all pixels of an optical sensor array applied to a field where the reliability of measurement accuracy is important is extracted in advance according to various conditions under a standard light source environment, and the first correction is performed. We propose a method of calculating reliable measurement values by proposing measurement and calibration standards according to It aims to reduce important judgment errors and increase reliability by recognizing them.

In a method for correction through characteristic evaluation of an optical sensor array according to the present invention for solving the above technical problem, a first correction value of the collection characteristic value by receiving a collection characteristic value of the optical sensor array with respect to a standard light source having a predetermined characteristic value extracting; receiving a collection characteristic value of the photosensor array with respect to the light source in the application environment and extracting a second correction value of the characteristic value of the light source in the application environment; and calculating a correction value for an application environment of the photosensor array by using the first correction value and the second correction value.

The extracting of the first correction value may include extracting a flattening correction value for flattening a collection characteristic value of the photosensor array according to a change in wavelength of the standard light source; and extracting a linearization correction value for linearizing a collection characteristic value of the photosensor array according to a change in the intensity of the standard light source.

The extracting of the second correction value may include: extracting a flattening correction value for flattening the collection characteristic value of the photosensor array of the applied wavelength of the light source of the application environment; and extracting a linearization correction value for linearizing the collection characteristic value of the photosensor array in the applied intensity band of the light source in the application environment.

In the step of extracting the second correction value, it is preferable that the light amount of the standard light source is the target light amount, and the collection characteristic value according to the exposure time or gain of the photosensor array of the application environment determined according to the target light amount is input.

A diagnostic method through an optical sensor array for solving the above technical problem includes the steps of: receiving a collection characteristic value collected in the optical sensor array with respect to a light source of an applied environment; and receiving a response characteristic value that is reacted by a reactant to the light source of the application environment and collected in the optical sensor array, wherein the optical sensor array is an optical sensor array for a standard light source having a predetermined characteristic value A first correction value of the collection characteristic value and a collection characteristic value of the photosensor array with respect to the light source in the application environment are received and the second correction value of the characteristic value of the light source in the application environment is used Therefore, it is desirable to collect the corrected characteristic values.

According to the present invention, it is possible to prepare a test and calibration standard for securing the measurement reliability of the optical sensor array applied to various environments, and since the reliability range of the measured value can be grasped, a user engaged in the actual bio/medical field can measure the measurement. By recognizing the error range of the result, it is possible to reduce the error of judgment and increase the reliability.

In addition, since the optical sensor can be implemented without an additional external lens module configuration, the configuration can be simplified, and it contributes to the activation of industrial fields such as ultra-small, high-performance lab-on-a-chip or implantable patch-type diagnostic devices.

1 is an exemplary diagram showing the structure of a digital camera with respect to a general light source.
2 is an exemplary view showing the structure of a photosensor array according to an embodiment of the present invention.
3 is a flowchart illustrating a correction method through characteristic evaluation of an external lens-free optical sensor array according to an embodiment of the present invention.
FIG. 4 is a detailed flowchart showing the test step according to FIG. 3 in more detail;
5 is a flowchart illustrating a diagnosis method through characteristic evaluation of a corrected external lens-free photosensor pixel array according to an embodiment of the present invention.
6 and 7 are diagrams illustrating an environment of a first test step according to an embodiment of the present invention.
8 and 9 are diagrams illustrating a second test environment according to an embodiment of the present invention.

The following is merely illustrative of the principles of the invention. Therefore, those skilled in the art can devise various devices that, although not explicitly described or shown herein, embody the principles of the invention and are included in the spirit and scope of the invention. Moreover, it should be understood that all conditional terms and examples listed herein are, in principle, expressly intended only for the purpose of understanding the inventive concept, and not limited to the specifically enumerated embodiments and states as such. do.

The above-described objects, features and advantages will become more apparent through the following detailed description in relation to the accompanying drawings, and accordingly, those of ordinary skill in the art to which the invention pertains will be able to easily practice the technical idea of the invention. .

In addition, in the description of the invention, if it is determined that a detailed description of a known technology related to the invention may unnecessarily obscure the gist of the invention, the detailed description thereof will be omitted. Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The present invention will be described in detail with reference to the accompanying drawings as follows.

1 is a diagram illustrating an application example of a conventional optical sensor, and FIG. 2 is a diagram illustrating an optical sensor used according to an embodiment of the present invention.

1 and 2, the optical sensor according to the present embodiment does not include a separate external lens.

Specifically, since FIG. 1 additionally includes an imaging lens, it includes a mount structure and a barrel configuration for mounting the lens, and thus there is a problem in that the overall sensor thickness is increased.

In contrast, as shown in FIG. 2 , the photosensor according to the present embodiment consists only of a light source for irradiating light and a photosensor for measuring light coming from a test sample, so that the configuration can be relatively simplified.

However, the optical sensor according to the present embodiment should have different measurement conditions for characteristic values from a general camera sensor having an external lens. In addition, an image in a normal camera is determined by interpolating the values of surrounding pixels that have passed through the red filter, green filter, and blue filter assigned to each pixel. do. Also, reliability of accuracy is even more important because the purpose of each pixel is to be an instrument.

In addition, since the final signal value is affected not only by the light source and the sensor, but also by the PCB board that reads the signal value from the sensor, in the state of the flip-chip sensor mounted on the actual application PCB as in this embodiment separately from the existing wafer test It is desirable to thoroughly test and calibrate the entire array under various conditions.

Specifically, in the case of a system in which a camera lens is mounted on an existing semiconductor sensor, focus adjustment is possible by the lens, but the optical sensor according to this embodiment is measured at a level that almost comes into contact with the test sample without a lens, so the test environment for this setting method and correction method are required.

That is, in order to obtain the standardized response result of FIG. 2 , it is necessary to set correction parameters such as the optical path difference due to the surface structure of the optical sensor array or the structure such as the internal microlens and color filter.

Hereinafter, with reference to FIG. 3 , a correction method for securing reliability of optical characteristics emitted from a sample through a lens-free optical sensor according to the present embodiment, specifically used light intensity, wavelength, and measurement parameters including optical axis A setting method of .

The correction method (hereinafter, the correction method) through the characteristic evaluation of the optical sensor array according to the present embodiment includes a first test step S100 , a second test step S200 , and a correction step S300 .

In the present embodiment, the first test step S100 receives a collection characteristic value of the optical sensor array for a standard light source having a predetermined characteristic value, and extracts a first correction value of the collection characteristic value.

That is, for absolute evaluation of the optical sensor array through the standard light source, characteristic values including flatness, linearity, sensor sensitivity, and signal to noise ratio (SNR) can be measured.

For the first test, the configuration of the darkroom and the uniformity of the light source may be required.

The environment of the first test will be described with reference to FIGS. 6 and 7 .

6 and 7 are exemplary views illustrating an environment of a first test according to an embodiment of the present invention.

That is, in FIG. 6 , the entry of external clutter is prevented through the darkroom configuration 10 of the first test. Thus, the device to be tested can be sealed with a housing.

A specific test device will be described with reference to FIG. 7 .

FIG. 7 is an enlarged view of area A of FIG. 6 .

Referring to FIG. 7 , in this embodiment, light of a desired wavelength is obtained by passing a monochromator through a tungsten lamp light source as a light source 20 and then connected to an integrating sphere. The photosensor array 30 is disposed perpendicular to the output port of the integrating sphere. The spatial uniformity of the integrating sphere output port light source should be within 0.1% of the total area of the optical sensor array and within 0.5% of the time uniformity. It is desirable to maintain the homogeneity within 1% of the amount of light corresponding to one code of the pixel output value. In this embodiment, a light source environment that satisfies the performance verified by an accredited certification authority is referred to as a standard light source 20 .

Since the sensor according to the present embodiment does not include an external lens, the distance between the light source and the sensor may act as a parameter affecting the characteristic evaluation. It is possible. Additionally, a jig configuration 40 for aligning the optical axis or distance may be included.

When the initial setting for the first test according to the above description is completed, the output code values of all pixels are read while setting the wavelength of the light source and increasing the intensity of the light source at uniform intervals.

This will be described in more detail with reference to FIG. 5 .

Referring to FIG. 5 , in the first test step ( S100 ) according to the present embodiment, a flattening correction value for flattening the collection characteristic value of the optical sensor array according to the change in the wavelength of the standard light source is extracted ( S110 ), and the standard light source A linearization correction value for linearizing the collection characteristic value of the photosensor array according to the change in the intensity of is extracted (S120).

First, in order to extract a flattening correction value, it is preferable to obtain a matrix value for flattening correction of the optical sensor while changing the wavelength of the light source, and store it in a database to create a correction coefficient lookup table.

Referring to FIG. 2 for planarization according to the present embodiment, the optical sensor according to the present embodiment includes a microlens for each pixel of the sensor array without an external lens as shown in FIG. 1 .

At this time, the geometric curvature of each of the configured microlenses is slightly different, so that the difference in the optical paths occurs. In this embodiment, each pixel value itself means a measured value reacted by the corresponding pixel, so the curvature of the microlens or additional filter configuration In order to reduce an error of each pixel value due to a different optical path, it is necessary to normalize the pixel value to a reference pixel value.

Therefore, in order to obtain the response result as shown in Fig. 2, in this embodiment, the pixel values measured through the flattening correction coefficient calculation in software are normalized.

Next, there is a limit to control the uniformity of key characteristic parameters such as doping concentration during the semiconductor fabrication process of the sensor, and there is a light absorption physical characteristic of silicon constituting the photodiode, which causes sensitivity deviation between pixels and has nonlinearity. Therefore, in order to extract the linearization correction value, it is preferable to obtain a matrix value for linearity correction of the optical sensor while changing the intensity of the light source and store it in a database to make a correction coefficient lookup table.

In the present embodiment, a matrix value for flattening correction and a matrix value for linearization correction may be extracted through Equation (1).

[Equation 1]

는 i번째 행과 j번째 열의 픽셀 이름이고, n은 출력코드값이다. 예를 들면, 8비트 ADC(아날로그 디지털 컨버터)인 경우, n은 0에서 255까지의 값이다.here,

is the pixel name of the i-th row and j-th column, and n is the output code value. For example, in the case of an 8-bit ADC (analog-to-digital converter), n is a value from 0 to 255.

는 i번째행과 j번째 열에 있는 픽셀의 보정된 출력코드값이다.

is the corrected output code value of the pixel in the i-th row and j-th column.

는 i번째행과 j번째 열에 있는 픽셀의 측정된 출력코드값이다.

is the measured output code value of the pixel in the i-th row and j-th column.

는 i번째행과 j번째 열에 있는 픽셀의 평탄화 보정값이다.

is the flattening correction value of the pixel in the i-th row and the j-th column.

는 i번째행과 j번째 열에 있는 픽셀의 선형성 보정값이다.

is the linearity correction value of the pixel in the i-th row and j-th column.

In addition, the dynamic range and SNR value of the photosensor array according to the present embodiment may be included as characteristic values.

Additionally, the first test step (S100) according to the present embodiment further includes a step (S105) of setting the exposure time or gain of the photosensor array to a default value with respect to a standard light source, and the test may be performed on the set amount of light. .

Thereafter, in the second test step (S200) according to this embodiment, the light amount of the standard light source set in the first test step (S100) is the target light amount, and the application environment of the photosensor array having a correction reference value determined according to the target light amount It receives the collection characteristic value for the light source.

That is, it is desirable to set a standard that allows the light amount of the light source used in each test to correspond to each other in order to calculate the correction value for the photosensor array through the characteristic value for the application environment and the characteristic value for the standard light source. do.

In this case, since the exposure time and gain can be used as the setting parameters of the photosensor array, the exposure time at which the target light amount and the light amount in the environment to which the photosensor array is currently applied as a reference for extracting the correction value are the same or the ratio is the same Or set the gain.

In this embodiment, the exposure time or gain may be set to a value satisfying Equation (2).

[Equation 2]

In this case, Luminence_Ratio represents the ratio of the target light quantity (OC _refOC ) and the light quantity (MOC) in the applied environment, and the exposure time or gain adjustment value to match the light quantity of the applied environment light source to the target light quantity, or a collection characteristic according to a combination thereof A value can be selected, and it is applied by setting it as a correction reference value (exposure time, gain) (S205).

Next, in the second test step (S200) in the present embodiment, in the light source of the application environment, the collection characteristic value of the photosensor array in which the correction reference value is set is received, and a second correction value of the characteristic value of the light source of the application environment is extracted. do.

That is, the second test step ( S200 ) uses the characteristic value of the optical sensor array for the application environment, and for example, extracts a sensing characteristic value according to light emission or fluorescence related to a bio-response such as a biosensor.

It is preferable that the second test step (S200) according to the present embodiment is also performed through a darkroom configuration, similarly to the above-described first test step (S100).

Specifically, in the second test step ( S200 ), the structure of the sensor used in the first test step ( S100 ) is implemented in an actual packaging environment, and characteristics are measured accordingly.

Referring to FIG. 8 , the photosensor array according to the present embodiment may be configured in a capsule-type package that can be inserted into the body. Specifically, referring to FIG. 9 , the test is performed by configuring the light source or the light reaction region 120 and the photosensor array 130 in an actual packaging environment.

As an embodiment of the present invention, when the luminescence reaction occurs on the surface of the photosensor, the cumulative average value of each pixel before the reaction is obtained in a state where the corrected value in the first test is applied, and the cumulative average value of each pixel is obtained during the reaction, and then the difference between the two The value can be output as the final result value.

In another embodiment of the present invention, in the case of a fluorescence reaction or a transmission reaction, the wavelength or intensity of the light source is controlled for uniformity of the light source.

That is, in this embodiment, when an LED (Light Emitting Diode) is used as the light source 120 as an example, the efficiency of the LED is affected by temperature. It can be applied to a substrate to be mounted so that a constant temperature is maintained.

In addition, in order to implement the uniformity of the brightness of the LED, it is possible to control the incoming power to give a constant brightness by implementing APC (Automatic Power Control) as a feedback circuit in the LED circuit.

Specifically, in this embodiment, the light source may be composed of a single LED of a specific wavelength or a combination of three primary color LEDs (RED, BLUE, GREEN). Furthermore, in order to form a physical spatially parallel light, a diffuser or a collimated light lens may be combined. Additionally, it is possible to adjust the intensity of the light source by configuring a dimmer circuit.

In addition, the method may further include aligning the optical axis of the light emitted from the light source in addition to the above-described setting of the uniformity of the light source. Specifically, in this embodiment, the optical axis of the parallel light of the light source is preferably aligned perpendicular to the sensor surface. That is, referring to FIG. 8 , a MEMS (Micro Electro Mechanical Systems) grating 140 may be used as one of the methods for determining whether alignment is present.

Referring to FIG. 5 , in the second test step ( S200 ) according to this embodiment, a flattening correction value for flattening the collection characteristic value of the applied wavelength of the photosensor array in which the correction reference value of the light source of the packaged application environment is set ( S205 ) and extracting (S210) a linearization correction value for linearizing the collection characteristic value of the optical sensor array in the applied intensity band of the light source of the application environment (S220).

First, it is preferable to obtain a flattening correction value of the photosensor array at the wavelength of the light source to be used for the bioreaction of the applied environment, and store it in a database to make a correction coefficient lookup table.

Next, it is preferable to obtain the linearity correction value of the optical sensor for some steps sampled with respect to the intensity band including the intensity of the light source of the applied environment, and store it in a database to create a correction coefficient lookup table.

In the present embodiment, the flattening correction value and the linearization correction value may be extracted by applying Equation 1 to some sampled steps.

In the correction step ( S300 ), a correction value for the application environment of the photosensor array is calculated by using the first correction value and the second correction value, and the correction value is applied to correct the photosensor array. That is, a correction reference value for the application environment of the optical sensor array is set, and in this embodiment, the flattening correction value and the linearity correction value obtained in the first test are multiplied by the flattening correction value and the linearity correction value abbreviated in the second test. A correction value is calculated, and flattening correction and linearity correction of each pixel of the optical sensor array are performed.

Additionally, referring to FIG. 6 , the final measurement through correction calculates the cumulative average of the characteristic values collected from each pixel before the reaction of the photosensor array to which the correction value is applied ( S410 ), and the characteristic value collected from each pixel during the reaction A cumulative average is calculated (S420), and the difference is calculated as a final pixel value (S430).

In this case, the cumulative average pixel value before the reaction may be extracted through Equation (3).

That is, a cumulative average is calculated by dividing the accumulated value of the collected pixel values by the number of collections.

[Equation 3]

는 반응전 (i,j)위치에 있는 픽셀에 대한 특성값인 출력코드값을 의미한다.

는 반응전 (i,j)위치에 있는 픽셀에 대한 특성값인 출력코드값의 누적 평균값을 의미한다. here,

denotes an output code value, which is a characteristic value for the pixel at the (i, j) position before the reaction.

is the cumulative average value of the output code value, which is a characteristic value of the pixel at the (i, j) position before the reaction.

Next, the accumulated average pixel values collected during the reaction may be extracted through Equation (4).

[Equation 4]

는 반응 동안 (i,j)위치에 있는 픽셀에 대한 특성값인 출력코드값을 의미한다.

는 반응 동안 (i,j)위치에 있는 픽셀에 대한 특성값인 출력코드값의 누적 평균값을 의미한다.here,

means the output code value, which is a characteristic value for the pixel at (i, j) position during the reaction.

is the cumulative average value of the output code value, which is a characteristic value for the pixel at the (i, j) position during the reaction.

The resulting pixel value D(x _i ,y _i ) calculated through their difference may be expressed by Equation (5).

[Equation 5]

In addition, in the second test step ( S200 ) in the present embodiment, it is also applicable to implement an environment that is packaged and used in addition to the packaging environment to calculate the characteristic value. For example, if the sensor according to the present embodiment is to be inserted into the human body to measure the blood glucose level in the body, it may be to implement the human body insertion environment as an environment inside the human body and to measure the characteristics thereof.

Next, it is desirable to write a report that contains at least the following information so that users who use the measurement data can understand how much error there is in reading the data.

First, it is desirable that the report on the test environment specification include the items shown in Table 1 below.

test Equipment and Environmental specification Value Tolerance Min Typical Max Illumination type Wavelength(λ) of Light source [nm] Two dimensional Uniformity of Light intensity at the each pixel surface [%] Uniformity of Light intensity when the time goes on [%] Angle of Light incidence with respect to the each pixel surface [ ^o ] Temperature [ ^o C] Humidity [%RH] Analog supply voltage [DC Volts] Analogue Supply current [mA] Digital Supply voltage [DC Volts] Digital Supply current [mA] external clock [MHz]

It is desirable that the specifications of the photosensor array include the contents shown in Table 2 below.

CMOS Photon sensor Specification Value Tolerance Min Typical Max sensor maker model name Pixel size [um * um] Resolution ADC [bit] Sensitivity Dynamic Range

It is preferable that the lookup table of the correction value includes the contents shown in Table 3 below.

Code /
( # of Photon) Calibrated Output Code value Measured Output Code value average Planarization Calibration Coefficient Linearity Calibration Coefficient One/
( ) .
.
. .
.
. .
.
. .
.
. .
.
. 100/
( ) .
.
. .
.
. .
.
. .
.
. .
.
. 200/
( ) .
.
. .
.
. .
.
. .
.
. .
.
. 255/
( ) .
.
. .
.
. .
.
. .
.
. .
.
.

According to the present invention as described above, it is possible to prepare a test and calibration standard for securing the measurement reliability of the optical sensor array applied to various environments, and since the reliability range of the measured value can be grasped, the actual bio/medical application user can finally It is possible to reduce potential judgment errors in judgment.

In addition, since the optical sensor can be implemented without an additional external lens module configuration, the configuration can be simplified, and it contributes to the activation of industrial fields such as ultra-small, high-performance lab-on-a-chip or implantable patch-type diagnostic devices.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains may make various modifications, changes and substitutions within the scope without departing from the essential characteristics of the present invention. will be.

Accordingly, the embodiments disclosed in the present invention and the accompanying drawings are for explaining, not limiting, the technical spirit of the present invention, and the scope of the technical spirit of the present invention is not limited by these embodiments and the accompanying drawings . The protection scope of the present invention should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

10: dark room 20: standard light source
30: optical sensor array 40: jig for optical axis and distance alignment
100: light sensor array package 120: light source or light reaction area
130: optical sensor array 140: MEMS grating

Claims (5)

setting an exposure time or gain of the photosensor array to a default value for a standard light source;
measuring a collection characteristic of the photosensor array by controlling a wavelength or intensity of the standard light source having a predetermined characteristic value;
obtaining a flattening correction value for flattening a collection characteristic value of the photosensor array according to a change in the wavelength of the standard light source;
obtaining a linearity correction value for linearizing a collection characteristic value of the photosensor array according to a change in the intensity of the standard light source; and
performing correction of the photosensor array using the flattening correction value and the linearity correction value;
Comprising, Calibration method through the characteristic evaluation of the optical sensor array. The method of claim 1,
The flattening correction value or the linearity correction value is obtained as a matrix value, a correction method through characteristic evaluation of an optical sensor array. The method of claim 1,
wherein the flattening correction value or the linearity correction value is stored in a database in the form of a correction coefficient lookup table. delete delete

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