# US 12,768,875 B2 · Electrical testing for panel characterization and defect screening

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- Number: US 12,768,875 B2
- Document ID: US12768875B2
- Status: Granted
- Kind: B2
- Application number: 18/656,567
- Filed: 2024-05-06
- Published: 2024-12-05
- Granted: 2026-10-20
- Earliest claimed: 2023-05-31
- Assignees: Apple Inc.
- Applicants: Apple Inc.
- Inventors: Xuebei Yang; Chung-Lun E Hsu; Cheuk Chi Lo; Hasan Akyol; Yingkan Lin; John T Wetherell; Han Zhao
- Web page: https://patentgrep.com/patent/US12768875B2

## CPC

- G01R 31/2635: {Testing light-emitting diodes, laser diodes or photodiodes}
- H10P 74/203: {Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

Systems and methods are provided for electrical testing to supplement or replace optical testing of an electronic display. Internal testing circuitry that includes analog front end (AFE) and analog-to-digital converter (ADC) circuitry may be included in the electronic display and may be used either alone or in combination with other testing devices to perform electrical characterization and defect screening. The electrical characterization and defect screening may be performed before or after self-emissive elements such as light-emitting diodes are installed, further improving yield. Types of electrical characterization and defect screening may include a partial passive mode electrical characterization of OLEDs, vertical or horizontal crosstalk measurement, scan line integrity testing, pixel bright dot testing, display pixel defect detection, and delayed defect detection for defects that may occur after some extended period of time (e.g., after several minutes, after several hours).

## Claims

### Claim 1

A system comprising:
an electronic display comprising:
an anode reset switch, wherein the anode reset switch is configured to couple anodes of self-emissive elements of selected display pixels to a test signal; and
a source driver coupled to test circuitry, via a test bus, wherein the source driver is configured to supply the test signal; and
a testing device configured to measure an aggregate current out of cathodes of the self-emissive elements of the selected display pixels that results due to the test signal to enable a current-voltage (IV) characterization of the self-emissive elements of the selected display pixels.

### Claim 2 (depends on 1)

The system of claim 1, wherein the selected display pixels comprise a plurality of rows of display pixels of the electronic display representing fewer than all rows of the electronic display.

### Claim 3 (depends on 2)

The system of claim 2, wherein the electronic display is configured to supply the test signal over an anode reset line of the electronic display.

### Claim 4 (depends on 3)

The system of claim 3, wherein the testing device is configured to change a number of rows under test based on a plurality of test voltages being applied.

### Claim 5 (depends on 1)

The system of claim 1, wherein the electronic display is configured to supply a plurality of test signals.

### Claim 6 (depends on 5)

The system of claim 5, wherein the selected display pixels comprise a first plurality of rows of display pixels of the electronic display when a first test signal of the plurality of test signals is supplied and a second plurality of rows of display pixels of the electronic display when a second test signal of the plurality of test signals is supplied.

### Claim 7

A method comprising:
programming display pixels of an electronic display with a plurality of test patterns;
measuring resulting currents through pixel circuitry of the display pixels using test circuitry disposed in the electronic display, wherein the test circuitry is configured to couple, via a test bus, to one or more source drivers of the electronic display; and
identifying a presence or an absence of vertical or horizontal cross talk based on the measurements.

### Claim 8 (depends on 7)

The method of claim 7, comprising determining to discard the electronic display in response to identifying the presence of the vertical or horizontal cross talk based on the measurements.

### Claim 9 (depends on 7)

The method of claim 7, comprising sensing a pixel current from a pixel, a row of pixels, or a column of pixels based on reset lines coupled to the test circuitry.

### Claim 10 (depends on 9)

The method of claim 9, comprising:
determining if the measurements are within an expected threshold; and
indicating that a panel of the electronic display is ready to proceed to self-emissive element installation.

### Claim 11 (depends on 9)

The method of claim 9, comprising:
determining if the measurements are outside an expected threshold; and
indicating that a panel of the electronic display is not ready to proceed to self-emissive element installation.

### Claim 12

A method comprising:
measuring display pixel currents associated with at least two display pixels of an electronic display using electrical test circuitry disposed in the electronic display, wherein the electrical test circuitry is configured to couple, via a test bus, to one or more source drivers of the electronic display; and
identifying a defect of the electronic display based on the measured display pixel currents.

### Claim 13 (depends on 12)

The method of claim 12, wherein:
the at least two display pixels comprise a first display pixel of a row and a last display pixel of the row; and
identifying the defect comprises identifying an integrity of a horizontal scan line based on whether the measured display pixel currents of the at least two display pixels fall within a specification.

### Claim 14 (depends on 12)

The method of claim 12, comprising programming all display pixels of the electronic display to display black;
wherein:
the at least two display pixels comprise all the display pixels of the electronic display; and
identifying the defect comprises identifying a presence of a bright dot pixel defect based on whether the measured display pixel currents of the at least two display pixels are nonzero.

### Claim 15 (depends on 14)

The method of claim 14, comprising repeating the programming, measuring, and identifying in a binary search pattern in response to identifying the presence of the bright dot pixel defect.

### Claim 16 (depends on 12)

The method of claim 12, wherein the method is performed before any self-emissive elements are installed on the electronic display.

### Claim 17 (depends on 16)

The method of claim 16, comprising, based on identifying the defect, indicating that a panel of the electronic display is not ready to proceed to self-emissive element installation.

### Claim 18 (depends on 17)

The method of claim 17, comprising sensing a pixel current from a pixel, a row of pixels, or a column of pixels based on reset lines coupled to the electrical test circuitry.

### Claim 19

A method comprising:
applying a bias or stress, or both, to display pixels of an electronic display;
measuring an aggregate current of all columns of the display pixels using test circuitry disposed in the electronic display, wherein the test circuitry is configured to couple, via a test bus, to one or more source drivers of the electronic display; and
identifying a presence or absence of a defective pixel based on a presence of a current that is outside of a specification.

### Claim 20 (depends on 19)

The method of claim 19, wherein the method is performed before any self-emissive elements are installed on the electronic display.

### Claim 21 (depends on 20)

The method of claim 20, comprising, based on identifying the presence of the defective pixel, indicating that a panel of the electronic display is not ready to proceed to self-emissive element installation.

### Claim 22 (depends on 21)

The method of claim 21, comprising sensing a pixel current from a pixel, a row of pixels, or a column of pixels based on reset lines coupled to the test circuitry.

### Claim 23

A method comprising:
providing an enable signal to a source driver connected to a data line of an electronic display;
testing the data line using test circuitry integral to the electronic display, wherein the test circuitry is configured to couple, via a test bus, to the source driver, and wherein testing the data line comprises measuring a voltage from the source driver on the data line that changes over time; and
identifying that the source driver has a non-T0 defect in response to measuring substantially zero voltage after previously measuring a nonzero voltage.

### Claim 24 (depends on 23)

The method of claim 23, comprising, based on comparing the voltage to thresholds, indicating that a panel of the electronic display is ready to proceed to self-emissive element installation.

### Claim 25 (depends on 23)

The method of claim 23, comprising, based on identifying the non-T0 defect, indicating that a panel of the electronic display is not ready to proceed to self-emissive element installation.