Software compensation color correction method for LED lamp beads

Abstract

The invention belongs to the technical field of LED driving, and particularly relates to a software compensation color correction method for LED lamp beads. By means of a light splitting test system in a lamp bead packaging link, key parameter values such as the position and the wavelength of a light-emitting wafer of each lamp bead and a lamp bead collection temperature value are comprehensively recorded, optical correction values are measured and calculated, and the optical correction values are stored in registers in the lamp beads; the application device is powered on to output the target brightness value, and the lamp bead calls the optical correction value in the register to achieve accurate control over the color of the lamp bead. The method provided by the invention thoroughly breaks through the limitation of a traditional Bin scheme, 96% of brightness / chromaticity deviation can be eliminated, lamp beads of different batches under different working conditions have completely consistent optical characteristics, and the method is particularly suitable for scenes such as Micro-LED display, medical endoscopes and the like which have extremely strict requirements on color precision.

Description

Technical Field

[0001] This invention belongs to the field of LED driving technology, and particularly relates to a software compensation color calibration method for LED chips. Background Technology

[0002] In modern high-quality LED applications, such as automotive lighting and Mini / Micro LED displays, the absolute consistency of the optical parameters of each LED chip is crucial, directly affecting the color uniformity and visual quality of the final product. However, in actual production, common process fluctuations such as micron-level offsets in die bonding positions and subtle differences in phosphor coating thickness can easily lead to significant color differences and uneven brightness in batch-produced LED chips.

[0003] Currently, the main method used is hardware sorting and compensation, which consists of the following three steps:

[0004] 1. Optical testing: The color coordinates (CIE x, y) and luminance value of the lamp beads are measured using an integrating sphere spectrometer;

[0005] 2. Fixed Bin Classification: Divide the area into 4-16 limited Bin zones according to a preset optical threshold;

[0006] 3. Mixed production of the same Bin group: LEDs of the same Bin level are woven into the same strip for use in the same batch of modules.

[0007] Using a spectrometer to select LED chips with similar emitting colors for tape packaging can result in the same batch of LED chips being divided into multiple batches of different colors. This limits the number that can be used in applications. The specific disadvantages are as follows:

[0008] 1. Insufficient precision: The granularity of the Bin area division is too coarse (maximum 16 levels), which cannot eliminate residual color differences within the same Bin area (single Bin color temperature fluctuation >100K) and only performs brightness screening, which cannot correct color deviation.

[0009] 2. Dynamic without compensation: Static Bin data cannot adapt to changes in working conditions. Current fluctuations will cause spectral drift and temperature rise will cause wavelength redshift.

[0010] 3. High cost: High-precision binning requires the elimination of more than 30% of the LED chips, and the cost of high-precision spectrometer equipment is much higher than that of ordinary spectrometer.

[0011] Application limitations: It cannot resolve color gamut deviations in multi-primary-color mixing scenarios. Summary of the Invention

[0012] To address the above problems, this invention proposes a software compensation color calibration method for LED beads.

[0013] The technical solution of this invention is as follows:

[0014] A software-based color calibration method for LED chips, characterized by comprising the following steps:

[0015] S1. Collect parameters from LED chips produced in the same batch. The parameters include the die-bonding coordinates (X, Y) of the chip and the wavelength. The LED chip diameter D and phosphor layer thickness h are set; simultaneously, the wafer reference coordinates for this batch of LED beads are established. , and fundamental wavelength ;

[0016] S2. Calculate the compensation coefficient based on the collected parameters, including:

[0017] The die-bonding coordinate compensation coefficient α is used in the Lambertian light source model, and the luminous flux loss caused by the offset is defined as follows: ,in = = Through the The formula is obtained by first-order approximation. Converted to exponential form, it is: Thus, the solid-state coordinate compensation coefficient α is obtained as = ;

[0018] Wavelength deviation compensation coefficient ,based on Using the photopic function in the CIE 1931 standard Perform the check table calculation, specifically by... The slope value is calculated at the corresponding wavelength range ±2nm position, and expressed as follows: = Then we can obtain = ;

[0019] S3. After obtaining the compensation coefficient for each LED based on the method in S2, the compensation coefficient is stored in the internal memory of the LED, and the actual driving current of each LED is corrected using the following formula:

[0020]

[0021] in, This is the corrected drive current. It is the target driving current for the LED;

[0022] By using a modified driving current to drive the LED beads, the brightness of LED beads produced in the same batch can be made uniform.

[0023] Furthermore, the method for acquiring parameters of LED beads in S1 is to use a spectrometer and an integrating sphere spectrometer.

[0024] The beneficial effects of this invention are: the method of this invention completely breaks through the limitations of the traditional binning scheme, can eliminate 96% of the brightness / color deviation, and make the lamp beads of different batches and different working conditions present completely consistent optical characteristics, which is particularly suitable for scenarios with extremely strict requirements for color accuracy, such as Micro-LED displays and medical endoscopes. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall process of the present invention.

[0026] Figure 2 This is a schematic diagram of the visual curve. Detailed Implementation

[0027] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0028] This invention achieves precise control over LED color output through factory optical calibration calculations for individual LED chips and embedded storage technology. For example... Figure 1 As shown, specifically: using the spectral testing system in the LED chip packaging process, key parameter values ​​such as the position of the light-emitting chip, wavelength, and LED chip acquisition temperature of each LED chip are comprehensively recorded, optical correction values ​​are calculated, and stored in the register inside the LED chip; when the application device is powered on and outputs the target brightness value, the LED chip will call the optical correction value inside the register to achieve precise control of the LED chip color.

[0029] The detailed process of the three steps of the method of the present invention is described as follows:

[0030] I. Lamp Bead Parameter Acquisition: A spectrometer and integrating sphere spectrometer were used to acquire the die-attach coordinates (X, Y) and wavelength of the wafer. The four parameters are: LED chip diameter D, phosphor layer thickness h, etc. and For wafer reference coordinates, The base wavelength.

[0031] II. Calculation of Optical Correction Values:

[0032] 1. Determination of the solid-state coordinate compensation coefficient α:

[0033] Using the Lambertian light source model, the luminous flux loss caused by the offset is derived. ;

[0034] in: = = ;

[0035] Make a first-order approximation of the formula: ;

[0036] Convert to exponential form: ;

[0037] Therefore, the die-bonding coordinate compensation coefficient α is = ;

[0038] 2. Wavelength deviation compensation coefficient Determination:

[0039] Wavelength deviation compensation requires referring to the photopic function in the CIE 1931 standard. By measuring the photopic vision function for different target wavelength bands, the photopic vision curve is shown below. Figure 2 As shown. Calculate the slope value of the photopic vision curve at a specific wavelength range (±2nm) for the red, green, and blue regions:

[0040] = ;

[0041] = ;

[0042] Examples of commonly used red, green, and blue wavelengths, corresponding to blue light. Green light and red light Solve for the wavelength deviation compensation coefficient in the corresponding band. The specific method for calculating the slope value using a check table is shown in Table 1:

[0043] Table 1. Slope values ​​calculated using the test table.

[0044]

[0045] 3. The final output current based on die-bonding coordinate positioning and wavelength-intensity matching model. The formula is as follows:

[0046]

[0047] Where: solidification coordinate compensation coefficient = Wavelength deviation compensation coefficient Based on the fundamental wavelength Perform the tests at three different speeds: red, green, and blue. , and The choice.

[0048] The obtained optical compensation coefficients are written into the internal storage space of the LED. When the application outputs the brightness of the LED, the LED will automatically control and output an accurate brightness value, thus achieving uniformity of the brightness value of the entire board without occupying the computing power of the application control chip.

Claims

1. A software compensation color calibration method for LED chips, characterized in that, Includes the following steps: S1. Collect parameters from LED chips produced in the same batch. The parameters include the die-bonding coordinates (X, Y) of the chip and the wavelength. The LED chip diameter D and phosphor layer thickness h are set; simultaneously, the wafer reference coordinates for this batch of LED beads are established. , and fundamental wavelength ; S2. Calculate the compensation coefficient based on the collected parameters, including: The die-bonding coordinate compensation coefficient α is used in the Lambertian light source model, and the luminous flux loss caused by the offset is defined as follows: ,in = = Through the The formula is obtained by first-order approximation. Converted to exponential form, it is: Thus, the solid-state coordinate compensation coefficient α is obtained as = ; Wavelength deviation compensation coefficient ,based on Using the photopic function in the CIE 1931 standard Perform the check table calculation, specifically by... The slope value is calculated at the corresponding wavelength range ±2nm position, and expressed as follows: = Then we can obtain = ; S3. After obtaining the compensation coefficient for each LED based on the method in S2, the compensation coefficient is stored in the internal memory of the LED, and the actual driving current of each LED is corrected using the following formula: ， in, This is the corrected drive current. It is the target driving current for the LED; By using a modified driving current to drive the LED beads, the brightness of LED beads produced in the same batch can be made uniform.

2. The software compensation color calibration method for LED beads according to claim 1, characterized in that, The method for acquiring parameters of LED beads in S1 is to use a spectrometer and an integrating sphere spectrometer.

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