An apparatus and method for measuring the solid angle of emission from a top-emitting light-emitting device.

Abstract

This invention discloses an apparatus and method for measuring the solid angle of a top-emitting light-emitting device (PED). The apparatus includes a base for placing the PED and a hemispherical cavity disposed on the base. A photodiode is positioned at the intersection of two perpendicular meridians inside the hemispherical cavity, and several photodiodes are symmetrically arranged on both sides of the intersection along the same meridian. The apparatus provided by this invention allows for the accurate measurement of the solid angle of the PED. By inputting the measured solid angle parameters into an integrating sphere, the light intensity and brightness, and other related optical parameters of the PED can be accurately measured. This is of great significance for the research of PEDs.

Description

Technical Field

[0001] This invention relates to the field of measurement technology of the solid angle of light emission of light-emitting devices, and in particular to an apparatus and method for measuring the solid angle of light emission of a top-emitting light-emitting device. Background Technology

[0002] Based on the different light emission methods, light-emitting diode (LED) devices can be divided into bottom-emitting and top-emitting structures. In a bottom-emitting structure, only a portion of the emitted light can escape through the openings in the TFT (TFT-based photodiode), resulting in wasted light and a low aperture ratio. In a top-emitting device, light exits from the top and is unaffected by the TFT, effectively increasing the aperture ratio. Compared to ordinary bottom-emitting devices, top-emitting LEDs offer advantages such as improved color purity, adjustable emission color, and the ability to emit at specific wavelengths, making them advantageous for manufacturing large-size, high-brightness, and high-resolution displays. Furthermore, the ITO transparent electrodes used in bottom-emitting devices are expensive, a problem avoided by top-emitting designs. Therefore, top-emitting LEDs have a very promising future. The structure of top-emitting LEDs is essentially the same as that of bottom-emitting devices, making their research extremely important. Due to the microcavity effect of top-emitting LEDs, the emitted light is not Lambertian but rather divergent three-dimensional light with a certain angle. When using an integrating sphere to measure the optical performance parameters of a top-emitting light-emitting device, the integrating sphere measures the energy distribution at each wavelength, i.e., the radiant energy distribution. Integrating over a certain wavelength range yields the radiant flux of the entire device. Combined with the device's area and emission solid angle, the radiant brightness can be calculated. Due to the microcavity effect of top-emitting devices, the emitted light is not Lambertian but rather divergent solid light with a certain angle. Therefore, measuring the solid angle of the emitted light from a top-emitting light-emitting device is particularly important for accurately calculating the device's luminous intensity and brightness.

[0003] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an apparatus and method for measuring the solid angle of light emission of a top-emitting light-emitting device, in order to solve the problem that the prior art cannot accurately measure the solid angle of light emission of a top-emitting light-emitting device.

[0005] The technical solution of the present invention is as follows:

[0006] A device for measuring the solid angle of a top-emitting light-emitting device includes a base for placing the top-emitting light-emitting device and a hemispherical cavity disposed on the base. A photodiode is disposed at the intersection of two mutually perpendicular meridians inside the hemispherical cavity, and a plurality of photodiodes are symmetrically disposed on both sides of the intersection on the same meridian.

[0007] The apparatus for measuring the solid angle of light emission from a top-emitting light-emitting device is provided, wherein the angle formed by the line connecting any two adjacent photodiodes on the same meridian to the center of the hemispherical cavity is the same.

[0008] The apparatus for measuring the solid angle of a top-emitting light-emitting device includes 6-20 photodiodes evenly arranged on both sides of the intersection point on the two meridians.

[0009] The device for measuring the solid angle of a top-emitting light-emitting device has nine photodiodes evenly arranged on both sides of the intersection point on the two meridians.

[0010] The apparatus for measuring the solid angle of light emission from a top-emitting light-emitting device includes a first through-hole on the hemispherical cavity, through which the photodiode is electrically connected to an external current detector.

[0011] The apparatus for measuring the solid angle of light emission of a top-emitting light-emitting device, wherein each photodiode in the hemispherical cavity has a corresponding first through hole on its side.

[0012] The device for measuring the solid angle of a top-emitting light-emitting device includes a second through hole on the base through which the top-emitting light-emitting device is electrically connected to an external power source.

[0013] The apparatus for measuring the solid angle of light emission from a top-emitting light-emitting device, wherein the photodiode is a silicon photodiode.

[0014] The apparatus for measuring the solid angle of light emission from a top-emitting light-emitting device includes QLED devices and OLED devices.

[0015] A method for measuring the solid angle of a top-emitting light-emitting device based on the aforementioned measuring device, comprising the steps of:

[0016] Place the top-emitting light-emitting device on the base;

[0017] By energizing the top-emitting light-emitting device, the maximum current I0 output by the photodiode inside the hemispherical cavity is obtained;

[0018] Based on the maximum current I0, find the photodiode in a meridian whose output current is closest to I0 / 2 and record the first angle of the photodiode. Based on the first angle, obtain the first half-value angle of the top-emitting light-emitting device.

[0019] Based on the maximum current I0, find the photodiode in another meridian whose output current is closest to I0 / 2 and record the second angle of the photodiode. Based on the second angle, obtain the second half-value angle of the top-emitting light-emitting device.

[0020] The solid angle of the top-emitting light-emitting device is obtained based on the first half-value angle, the second half-value angle, and the correspondence between the half-value angle and the solid angle.

[0021] Beneficial Effects: This invention provides a device for measuring the emission solid angle of a top-emitting light-emitting device. It acquires the half-value angle of the emission from the top-emitting light-emitting device by using photodiodes uniformly arranged within a hemispherical cavity. Finally, based on the known correspondence between the half-value angle and the solid angle, the emission solid angle of the top-emitting light-emitting device is derived. By inputting the emission solid angle parameter measured by this invention into an integrating sphere, the light intensity and brightness, and other related optical parameters of the top-emitting light-emitting device can be accurately measured. This is of great significance for the research of top-emitting light-emitting devices. Attached Figure Description

[0022] Figure 1 This is a first-view exploded view of a device for measuring the solid angle of a top-emitting light-emitting device according to the present invention.

[0023] Figure 2 This is a second-view exploded view of a device for measuring the solid angle of a top-emitting light-emitting device according to the present invention.

[0024] Figure 3 This is a schematic diagram of the overall structure of a device for measuring the solid angle of a top-emitting light-emitting device according to the present invention.

[0025] Figure 4 This is a flowchart of a preferred embodiment of a method for measuring the solid angle of a top-emitting light-emitting device according to the present invention.

[0026] Figure 5 This is a schematic diagram of the light emission of the top-emitting light-emitting device of the present invention. Detailed Implementation

[0027] This invention provides an apparatus and method for measuring the solid angle of a top-emitting light-emitting device. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] The performance of luminescent materials and devices can generally be evaluated from two aspects: luminescent performance and electrical performance. Luminescent performance mainly includes emission spectrum, luminous intensity, luminous efficiency, luminous chromaticity, and lifetime; while electrical performance includes the relationship between current and voltage, etc. These are the main parameters for measuring the performance of materials and devices. Due to their microcavity effect, top-emitting light-emitting devices do not emit light from a Lambertian beam, but rather diffuse light with a certain angle. When using an integrating sphere to measure their optical characteristics, such as light intensity and brightness, the emission angle of the device is involved. Therefore, accurately measuring the emission solid angle of top-emitting devices is particularly important for accurately measuring their optical parameters.

[0029] Based on this, embodiments of the present invention provide a device for measuring the solid angle of emission from a top-emitting light-emitting device, such as... Figures 1-3 As shown, it includes a base 20 for placing a top-emitting light-emitting device 10, and a hemispherical cavity 30 disposed on the base 20. A plurality of photodiodes 31 are evenly disposed on two mutually perpendicular meridians inside the hemispherical cavity 30. A photodiode 31 is disposed at the intersection of the two mutually perpendicular meridians inside the hemispherical cavity 30, and a plurality of photodiodes 31 are symmetrically disposed on both sides of the intersection on the same meridian.

[0030] In this embodiment, the photodiodes 31 disposed on the two mutually perpendicular meridians are used to measure the light intensity of the light emitted by the top-emitting light-emitting device 10 at different angles, and convert the received light intensity into a photocurrent of corresponding magnitude. In this embodiment, the intersection of the two mutually perpendicular meridians is the vertex inside the hemispherical cavity 30. The photodiode at the intersection is connected to the center of the hemispherical cavity 30 to form a first line, and any photodiode on the meridian is connected to the center of the hemispherical cavity 30 to form a second line. The included angle between the first line and the second line is known.

[0031] In some embodiments, the angle formed by the line connecting any two adjacent photodiodes 31 on the same meridian to the center of the hemispherical cavity 30 is the same. In this embodiment, the photodiodes 31 on the same meridian are evenly arranged, so after setting a fixed number of photodiodes on the same meridian, the angle of each photodiode is known.

[0032] In some embodiments, assuming the angle between the line connecting two adjacent photodiodes 31 on the same meridian and the center of the hemispherical cavity 30 is 10°, nine photodiodes need to be evenly arranged at 10° intervals on both sides of the intersection point (clockwise and counterclockwise directions). The photodiode at the intersection point is marked as a0 = 0°. Then, each photodiode in the clockwise direction, from closest to farthest from the vertex, can be sequentially marked as a1 = 10°, a2 = 2°, etc. 0°, a3=30°, a4=40°, a5=50°, a6=60°, a7=70°, a8=80°, a9=90°; then each photodiode in the counterclockwise direction at the intersection point, from closest to farthest, can be sequentially labeled as a1'=-10°, a2'=-20°, a3'=-30°, a4'=-40°, a5'=-50°, a6'=-60°, a7'=-70°, a8'=-80°, a9'=-90°. Similarly, all photodiodes 31 on the other meridian can be marked. The number of photodiodes on the two meridians can be equal or unequal. Taking the number of photodiodes on the two meridians as an example, with the intersection point a0 as the origin on the other meridian, each photodiode on the other meridian, in a clockwise direction, can be marked as b1 = 10°, b2 = 20°, b3 = 30°, b4 = 40°, respectively, from the closest to the intersection point. b5 = 50°, b6 = 60°, b7 = 70°, b8 = 80°, b9 = 90°; correspondingly, each photodiode in the counterclockwise direction at the intersection point, from closest to farthest, can be sequentially marked as b1' = -10°, b2' = -20°, b3' = -30°, b4' = -40°, b5' = -50°, b6' = -60°, b7' = -70°, b8' = -80°, b9' = -90°.

[0033] Due to the microcavity effect of the top-emitting light-emitting device, the light intensity is strongest in the direction parallel to the normal of the top-emitting light-emitting device, and the light intensity weakens the further away from the normal. Taking the top-emitting light-emitting device located at the center of the hemispherical cavity 30 as an example, the light intensity collected by the photodiode a0 located at the intersection of the two meridians is the strongest, and its output photocurrent I0 is the largest. On one meridian, the positions of the photodiodes whose photocurrents are closest to I0 / 2 are found in both clockwise and counterclockwise directions at the intersection. The angle of the photodiode found in the clockwise direction is recorded as a, and the angle of the photodiode found in the counterclockwise direction is recorded as a'. At this time, one half-value angle 2α of the top-emitting light-emitting device is 2α = a + |a'|. On the other meridian, the positions of the photodiodes whose photocurrents are closest to I0 / 2 are found. The angle of the photodiode found in the clockwise direction is recorded as b, and the angle of the photodiode found in the counterclockwise direction is recorded as b'. At this time, the other half-value angle 2β of the top-emitting light-emitting device is 2β = b + |b'|.

[0034] After obtaining the two half-value angles of the top-emitting light-emitting device, the emission solid angle of the top-emitting light-emitting device can be directly obtained according to the correspondence between the half-value angles and the emission solid angle.

[0035] In some embodiments, 6-20 photodiodes are evenly arranged on both sides of the intersection point along the two meridians. In this embodiment, by arranging different numbers of photodiodes on both sides of the intersection point, photocurrent data at different angles can be obtained; the more photodiodes arranged, the more angles of photocurrent data can be obtained, resulting in a more accurate half-value angle and thus a more accurate solid angle. For example, when 6 photodiodes are evenly arranged at both ends of the apex of the hemispherical cavity, it is equivalent to placing one photodiode every 15°. At this time, only the light-emitting diode closest to I0 / 2 can be found from 6 angles, which will cause the photocurrent of the found photodiode to differ significantly from I0 / 2, resulting in an inaccurate solid angle. For example, when 18 photodiodes are evenly arranged at both ends of the apex of the hemispherical cavity, it is equivalent to placing one photodiode every 5°. At this time, the light-emitting diode closest to I0 / 2 can be found from 18 angles, which makes the photocurrent of the found photodiode less different from I0 / 2, thus obtaining a more accurate solid angle.

[0036] In some specific implementation methods, such as Figure 1-3As shown, nine photodiodes are evenly arranged on both sides of the intersection point on the two meridians. At this time, a photodiode is arranged at a position equivalent to every 10° on the meridian. At this time, the light-emitting diode closest to I0 / 2 can be found from the nine angles of 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° and 90°. The photocurrent of the photodiode found at this time is small compared with I0 / 2, so a more accurate solid angle can be obtained.

[0037] In some implementations, such as Figure 1 and Figure 2 As shown, the hemispherical cavity 30 is provided with a first through hole 32, through which the photodiode 31 is electrically connected to an external current detector. Specifically, the photodiode operates under reverse voltage. In the absence of light, its reverse current is extremely weak, called dark current; under light, the reverse current rapidly increases to tens of microamps, called photocurrent. The greater the intensity of the received light, the greater the reverse current generated. Changes in light intensity cause changes in the photodiode current, which converts the light signal into an electrical signal. The photocurrent generated by the photodiode needs to be detected by an external current detector. Since the photodiode is located inside the hemispherical cavity 30, the wires connecting the photodiode need to be led out from inside the hemispherical cavity 30 to the outside through the first through hole 32, thus electrically connecting it to the external current detector. In some specific embodiments, each photodiode 31 in the hemispherical cavity has a corresponding first through hole 32 on its side, which facilitates reading the photocurrent value and quickly finding the angle corresponding to each photodiode.

[0038] In some specific embodiments, the photodiode is a silicon photodiode, but it is not limited thereto.

[0039] In some implementations, such as Figure 1 and Figure 2 As shown, the base 20 is provided with a second through hole 21, through which the top-emitting light-emitting device 10 is electrically connected to an external power source. Specifically, the top-emitting light-emitting device 10 needs to be electrically connected to and powered by an external power source to emit light. Since the top-emitting light-emitting device 10 is located on the base 20 and covered by the hemispherical cavity 30 during testing, the wires connecting the top-emitting light-emitting device 10 need to be led out from the inside of the hemispherical cavity 30 to the outside through the second through hole 21, thereby connecting it to the external power source.

[0040] In some embodiments, a limiting groove may be provided on the base 20 to facilitate the placement of the top-emitting light-emitting device in the limiting groove, thereby preventing the top-emitting light-emitting device from moving during the test, which would lead to inaccurate half-value angle measurements and ultimately affect the measurement accuracy of the solid angle.

[0041] In some embodiments, to facilitate efficient measurement of the solid angle of different top-emitting light-emitting devices, the base 20 and the hemispherical cavity 30 are detachably connected. For example, the base 20 is circular, and a circular protrusion ring 22 with the same center as the base 20 and a radius smaller than the radius of the base 20 is provided on the base 20. The inner diameter of the bottom circle of the hemispherical cavity 30 is equal to the outer diameter of the circular protrusion ring 22. The hemispherical cavity 30 can be directly placed on the base and limited by the circular protrusion ring 22. In some more specific embodiments, the circular protrusion ring 22 is provided with an external thread, and the bottom of the hemispherical cavity 30 is provided with an internal thread adapted to the external thread. By placing the hemispherical cavity 30 on the circular protrusion ring 22 and rotating the hemispherical cavity 30, the hemispherical cavity 30 and the circular protrusion ring 22 can be detachably connected through the adaptation of the external and internal threads.

[0042] In some embodiments, the top-emitting light-emitting device includes top-emitting QLED devices and top-emitting OLED devices, but is not limited thereto.

[0043] In some embodiments, a method for measuring the emission solid angle of a top-emitting light-emitting device based on the measuring device is also provided, such as... Figure 4 As shown, it includes the following steps:

[0044] S10. Place the top-emitting light-emitting device on the base;

[0045] S20. Power on the top-emitting light-emitting device and obtain the maximum current I0 output by the photodiode in the hemispherical cavity.

[0046] S30. Based on the maximum current I0, find the photodiode in a meridian whose output current is closest to I0 / 2 and record the first angle of the photodiode. Based on the first angle, obtain the first half-value angle of the top-emitting light-emitting device.

[0047] S40. Based on the maximum current I0, find the photodiode in another meridian whose output current is closest to I0 / 2 and record the second angle of the photodiode. Based on the second angle, obtain the second half-value angle of the top-emitting light-emitting device.

[0048] S50. The solid angle of the top-emitting light-emitting device is obtained based on the first half-value angle, the second half-value angle, and the correspondence between the half-value angle and the solid angle.

[0049] In this embodiment, as Figure 5 As shown, due to the microcavity effect of the top-emitting light-emitting device, the light intensity is strongest in the direction parallel to the normal of the top-emitting light-emitting device, and the light intensity is weaker the further away from the normal. By finding the photodiode whose output current is closest to I0 / 2 on two mutually perpendicular meridians in the hemispherical cavity and recording the angle of the photodiode, the two half-value angles of the top-emitting light-emitting device on the two meridians are obtained. Finally, the solid angle of the top-emitting light-emitting device is obtained according to the correspondence between the half-value angle and the solid angle.

[0050] Specifically, extending the definition of radians as the size of a planar angle to three-dimensional space, we define a solid angle as the ratio of the area of ​​a sphere to the square of its radius. Given that the luminous angles of a lamp in two mutually perpendicular directions are 2α and 2β, find the corresponding solid angles.

[0051] Let the radius of the sphere be 1 unit, and the origin of the coordinate system be at the center of the sphere. By definition, we only need to find the area of ​​the sphere enclosed by the two angles, which is the size of the solid angle. Due to symmetry, we only need to find the area within the first octant and multiply it by 4.

[0052] The formula for calculating the area of ​​a curved surface is:

[0053]

[0054] The equation of the upper hemisphere is:

[0055]

[0056] Depend on

[0057]

[0058] have to

[0059] Substituting into equation (1), we get:

[0060]

[0061] Using polar coordinates, we obtain:

[0062] The projection of the integration region onto the xy-plane is bounded by two elliptic curves, whose equations are as follows:

[0063]

[0064]

[0065] The coordinates of the intersection point are:

[0066]

[0067]

[0068] Substituting x = rcosφ and y = rsinφ into equations (8) and (9), we obtain the boundary equations in polar coordinates as follows:

[0069]

[0070]

[0071] Based on symmetry, we have:

[0072] A = 4(A1 + A2) (14)

[0073]

[0074]

[0075] then,

[0076]

[0077] Let t = sinφ, then cosφdφ = dt.

[0078]

[0079] Similarly, A2 = φ2 - arcsin(cosβsinφ2) (16);

[0080] Substituting equations (15) and (16) into equation (14), we obtain the final result:

[0081]

[0082] Specifically, when α = β, Φ1 = Φ2 = π / 4, then,

[0083] As an example, take the correspondence between half-value angles and solid angles shown in Table 1.

[0084] Table 1. Correspondence between half-value angle and solid angle

[0085]

[0086] As shown in Table 1, when the two half-value angles of the top-emitting light-emitting device on the two meridians are 60° and 75° respectively, the solid angle of the top-emitting light-emitting device is 1.237; when the two half-value angles of the top-emitting light-emitting device on the two meridians are both 90°, the solid angle of the top-emitting light-emitting device is 2.094.

[0087] In summary, this invention provides a device for measuring the emission solid angle of a top-emitting light-emitting device. It acquires the half-value angle of the emitted light from the top-emitting light-emitting device by using photodiodes uniformly arranged within a hemispherical cavity. Finally, based on the known correspondence between the half-value angle and the solid angle, the emission solid angle of the top-emitting light-emitting device is derived. By inputting the emission solid angle parameter measured by this invention into an integrating sphere, the light intensity and brightness, and other related optical parameters of the top-emitting light-emitting device can be accurately measured. This is of great significance for the research of top-emitting light-emitting devices.

[0088] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A device for measuring the solid angle of emission from a top-emitting light-emitting device, characterized in that, It includes a base for placing a top-emitting light-emitting device, and a hemispherical cavity disposed on the base. A photodiode is disposed at the intersection of two mutually perpendicular meridians inside the hemispherical cavity, and several photodiodes are symmetrically disposed on both sides of the intersection on the same meridian. The angle formed by the lines connecting any two adjacent photodiodes on the same meridian to the center of the hemispherical cavity is the same; The measurement method using the aforementioned apparatus for measuring the solid angle of a top-emitting light-emitting device includes the following steps: Place the top-emitting light-emitting device on the base; By energizing the top-emitting light-emitting device, the maximum current I0 output by the photodiode inside the hemispherical cavity is obtained; Based on the maximum current I0, find the photodiode in a meridian whose output current is closest to I0 / 2 and record the first angle of the photodiode. Based on the first angle, obtain the first half-value angle of the top-emitting light-emitting device. Based on the maximum current I0, find the photodiode in another meridian whose output current is closest to I0 / 2 and record the second angle of the photodiode. Based on the second angle, obtain the second half-value angle of the top-emitting light-emitting device. The solid angle of the top-emitting light-emitting device is obtained based on the first half-value angle, the second half-value angle, and the correspondence between the half-value angle and the solid angle.

2. The apparatus for measuring the solid angle of a top-emitting light-emitting device according to claim 1, characterized in that, Six to twenty photodiodes are evenly arranged on both sides of the intersection point on the two meridians.

3. The apparatus for measuring the solid angle of a top-emitting light-emitting device according to claim 1, characterized in that, Nine photodiodes are evenly arranged on both sides of the intersection point on the two meridians.

4. The apparatus for measuring the solid angle of a top-emitting light-emitting device according to claim 1, characterized in that, The hemispherical cavity is provided with a first through hole, and the photodiode is electrically connected to an external current detector through the first through hole.

5. The apparatus for measuring the solid angle of a top-emitting light-emitting device according to claim 4, characterized in that, In the hemispherical cavity, each photodiode has a corresponding first through hole on its side.

6. The apparatus for measuring the solid angle of a top-emitting light-emitting device according to claim 1, characterized in that, The base is provided with a second through hole, through which the top-emitting light-emitting device is electrically connected to an external power source.

7. The apparatus for measuring the solid angle of a top-emitting light-emitting device according to claim 1, characterized in that, The photodiode is a silicon photodiode.

8. The apparatus for measuring the solid angle of a top-emitting light-emitting device according to claim 1, characterized in that, The top-emitting light-emitting devices include QLED devices and OLED devices.

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