LED integrated business screen light-emitting chips from the substrate and epitaxial layer after growth, and then through the process of vapor deposition, lithography, grinding, cutting, etc. in the space of light intensity and the spectral band has been determined. As the LED integrated business screen light-emitting area is small, the area of common light-emitting chips on the market today is generally 150umx200um, 125μumx275μm, 100μmx200μm, and 75μumx150μm. LED integrated business screen light-emitting chips can be approximated as a point source, approximating a Lambert luminous body. As shown in Figure 3.1:
Point source O (approximate Lambert luminous body) in space in a certain direction per unit area, unit stereo angle emitted light to a point P in space at a unit distance, P received irradiance for can be expressed in the formula (3-1), the unit is watts per spherical degree per square meter (W/Sr-m2).
In Equation (3-1), Ie is the radiation intensity, dS is the receiving area of point P. When the observer stands at the point P location, the luminosity of the point light source 0 perceived by the observer should follow the photometric equation, as Equation (3-2), (3-3), and (3-4) are shown:
I number is the luminous intensity, the unit candela (cd). L is the luminosity (hereinafter collectively referred to as luminance), also used to indicate the brightness of the LED integrated business screen light-emitting chip, unit candela per square meter (cd/m2). K (2) for the spectral light efficiency function. But LED integrated business screen light-emitting chip is not a standard Lambert luminous body, but a luminous intensity with the angle change with the decay effect of the polyhedral light source ( cosine luminous body ), as shown in Figure 3.2:
Luminous intensity and luminous angle relationship as shown in the formula (3-5).
Io for the normal luminous intensity. In for the spatial horizontal angle θn at the luminous intensity, m for the LED light-emitting chip horizontal direction of the light distribution coefficient. Iv for the spatial vertical angle θv at the luminous intensity, n for the LED light-emitting chip vertical direction of the light distribution coefficient. Figure(a),(b), and (c) shows measured red, green, and blue light-emitting chips in space light intensity distribution.
The above figure shows that the LED integrated business screen light-emitting chip at the normal luminous intensity of the maximum, with the increase in the luminous angle, LED integrated business screen luminous intensity gradually decays. Red, green, and blue luminous perspective is approximately equal, this paper's later analysis are red, green, and blue luminous chip luminous perspective is equal to the premise. When the LED integrated business screen light-emitting chip in the horizontal angle of θn, vertical angle of θv, where a beam of light after the distance d to a point in space P, P point at the observer feels the brightness not only with the luminous angleθn, θv, luminous intensity I related but also with the distance has relevance, as shown in the formula (3-6):
And when a huge number of LED integrated business screen light-emitting chips in accordance with a certain rule of arrangement, different positions of light-emitting chips relative to the same observation point light-emitting angle are not the same, with the number of increasing angle differences gradually increased. At the same time, LED integrated business screen light-emitting chips relative to the distance of the observation point are not the same, the same impact on the brightness of the point received LED integrated business screen light-emitting chips size. So when two LED integrated business screen light-emitting chips with the same luminous intensity due to the different positions in the display arrangement, resulting in the same observation point at the received brightness is not the same.
In order to make each display pixel on the display can be properly displayed, LED integrated business screen light-emitting chips and electrode leads, fixed components, etc. need to be connected together through certain technology. First, the light-emitting chips are fixed on a substrate, called "solid crystal"; in the process of solid crystal, it is necessary to ensure that all LED integrated business screen light-emitting chips' optical axis are parallel, but due to process errors will be one or more LED integrated business screen light-emitting chips optical axis shift, as shown in Figure 3.4.
The blue LED integrated business screen light-emitting chip in the figure, the optical axis of the shift, resulting in the maximum luminous intensity of the angle change, as shown in Figure 3.5.
Let the spatial horizontal angle offset and vertical angle offset be △θn and △θv, respectively, and substitute them into Equation (3-6) to get the change of brightness at the same point.
Equation (3-7), r (θh), r (θv), s (θh. △θh), and s (θv .△θv) are △θh and △θv functions, due to the LED integrated business screen light-emitting chip's optical axis offset relative to the distance d of a point in space is extremely small so that d does not change. θh = 0, θv= 0 into the equation (3-6) and (3-7), respectively, the two formulas for The degree of change of brightness after the angular shift is obtained by dividing the two equations, as shown in Equation (3-8):
Equation (3-8), the solid crystal process caused by the axial shift resulting in the same light-emitting angle of the luminance change in proportion to r(△θh,△θv) = r(△θh)m Xr(△θv)n.
After the completion of the solid crystal, the positive and negative light-emitting chips and circuit boards are connected, known as the "connection". After the completion of welding, through the "glue" for the array arrangement of light-emitting chips to establish a layer of protection. And in the process of sealing glue, the presence of particulate matter in the glue layer will refract, reflect, and absorption of light, so the thickness of the glue layer is different, which will have an impact on the LED integrated business screen light-emitting chip luminous perspective and luminous intensity. As shown in Figure 3.6.
As the sealing process in the solid crystal after, so the solid crystal after the luminous perspective as the initial perspective, luminous intensity as the initial LED luminous intensity. Let the light-emitting chip horizontal angle offset and vertical angle offset are △θh1 and △θv1. △θh1, △θv1, and L(θh+△θh,θv+△θv) will be brought into the equation (3-7) and (3-8) to get the change in luminance after sealing, as shown in equation (3-9):
Equation (3-9) shows that the law of luminance change after sealing and the law of luminance change after solid crystallization are similar, and are the function of angle change. The formula (3-6), (3-8), and (3-9) joint, and then brought into the sealing process of luminous intensity △I1, to obtain the overall luminance change, as shown in the formula (3-10).
The whole process is called LED integrated business screen packaging, which is a process that each LED display must go through to manufacture. After a series of complex packaging processes, the luminous intensity of the LED integrated business screen changes at a certain light angle, and this change is irreversible. After the manufacturing of the display is completed, the luminous intensity change due to the packaging process being fixed and unpredictable, so the luminance after packaging is the real LED integrated business screen luminance. In the collection correction process, the luminous intensity of the above changes is considered equivalent to the difference in brightness of the luminous chip itself, the same as the true value of the collection correction, rather than the collection error. So the display pixel in a direction of the true brightness difference is the difference between the brightness of the luminescent chip itself and the amount of luminous intensity change brought about by the packaging process and the value.
