# US 2024/0201244 A1 · Light output estimation method for light-emitting device

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- Number: US 2024/0201244 A1
- Document ID: US20240201244A1
- Status: Published application
- Kind: A1
- Application number: 18/533,998
- Filed: 2023-12-08
- Published: 2024-06-20
- Earliest claimed: 2022-12-16
- Assignees: Nikkiso Co., Ltd.
- Applicants: Nikkiso Co., Ltd.
- Inventors: Kenta URA; Naoki SHIBATA
- Web page: https://patentgrep.com/patent/US20240201244A1

## CPC

- G01R 31/2635: {Testing light-emitting diodes, laser diodes or photodiodes}
- G01R 31/2642: {Testing semiconductor operation lifetime or reliability, e.g. by accelerated life tests}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

A light output estimation method for light-emitting device is a method for estimating light output of a light-emitting device that has a nitride semiconductor light-emitting element. The light output estimation method for light-emitting device includes a first estimation criterion to estimate light output of the light-emitting device in a period before a predetermined accumulated light emission time TX, and a second estimation criterion to estimate light output of the light-emitting device in a period after the predetermined accumulated light emission time TX. The first estimation criterion and the second estimation criterion are different criteria.

## Claims

### Claim 1

A light output estimation method for light-emitting device to estimate light output of a light-emitting device comprising a nitride semiconductor light-emitting element, the method comprising:
a first estimation criterion to estimate light output of the light-emitting device in a period before a predetermined accumulated light emission time TX; and
a second estimation criterion to estimate light output of the light-emitting device in a period after the predetermined accumulated light emission time TX,
wherein the first estimation criterion and the second estimation criterion are different criteria.

### Claim 2 (depends on 1)

The method according to claim 1, wherein each of the first estimation criterion and the second estimation criterion is expressed as a function of accumulated light emission time of the light-emitting device, and wherein a slope of the function for the first estimation criterion immediately before the predetermined accumulated light emission time TX is greater than a slope of the function for the second estimation criterion immediately after the predetermined accumulated light emission time TX.

### Claim 3 (depends on 1)

The method according to claim 1, wherein each of the first estimation criterion and the second estimation criterion is a criterion to estimate light output of the light-emitting device in such a manner that a deterioration rate of the light-emitting device decreases with a lapse of light emission time of the light-emitting device, and wherein the second estimation criterion is a criterion to estimate light output of the light-emitting device in such a manner that change in the deterioration rate of the light-emitting device over time is more gradual as compared to the first estimation criterion.

### Claim 4 (depends on 1)

The method according to claim 1, wherein each of the first estimation criterion and the second estimation criterion is expressed as a function of accumulated light emission time of the light-emitting device, and wherein the method comprises:
determining a coefficient of the function for the first estimation criterion based on at least a portion of light output data of the light-emitting device;
calculating an estimated light output value PX at the predetermined accumulated light emission time TX by using the first estimation criterion for which the coefficient has been determined; and
determining a coefficient of the function for the second estimation criterion based on the estimated light output value PX at the predetermined accumulated light emission time TX calculated using the first estimation criterion for which the coefficient has been determined.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the estimated light output value PX at the predetermined accumulated light emission time TX calculated using the first estimation criterion and an estimated light output value at the predetermined accumulated light emission time TX calculated using the second estimation criterion are the same value.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the first estimation criterion is expressed as a function including a term proportional to t1n1 (n1 is a value more than 0 and less than 1), where t1 is any given accumulated light emission time before the predetermined accumulated light emission time TX.

### Claim 7 (depends on 6)

The method according to claim 6, wherein the first estimation criterion is expressed by the following equation (1):
P
1
(
t
1
)
=
C
A
⁢
{
1
-
(
C
B
×
t
1
Cc
)
}
(
1
)
where P1 is an estimated light output value of the light-emitting device at the any given accumulated light emission time t1 and CA, CB and CC are predetermined coefficients.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the second estimation criterion is expressed as a function including a term proportional to exp(−n2×t2) (n2 is a value more than 0 and less than 0.001), where t2 is any given accumulated light emission time after the predetermined accumulated light emission time TX.

### Claim 9 (depends on 8)

The method according to claim 8, wherein the second estimation criterion is expressed by the following equation (2):
P
2
(
t
2
)
=
C
D
×
exp
⁡
(
-
C
E
×
t
2
)
(
2
)
where P2 is an estimated light output value of the light-emitting device at the any given accumulated light emission time t2 and CD and CE are predetermined coefficients.

### Claim 10 (depends on 1)

The method according to claim 1, wherein the light-emitting device emits deep ultraviolet light.