Systems, devices and methods for quality monitoring of deposited films in the formation of light emitting devices
This disclosure provides techniques for assessing quality of a deposited film layer of an organic light emitting diode (“OLED”) device. An image is captured and filtered to identify a deposited layer that is to be analyzed. Image data representing this layer can be optionally converted to brightness (grayscale) data. A gradient function is then applied to emphasize discontinuities in the deposited layer. Discontinuities are then compared to one or more thresholds and used to ascertain quality of the deposited layer, with optional remedial measures then being applied. The disclosed techniques can be applied in situ, to quickly identify potential defects such as delamination before ensuing manufacturing steps are applied. In optional embodiments, remedial measures can be taken dependent on whether defects are determined to exist.
1. A computer-implemented method for monitoring quality of a film deposited on a substrate, the film to form a layer in respective light emitting elements fabricated on the substrate, the film to span for each of the light emitting elements an area of predetermined dimensions, the computer-implemented method comprising:
for each one of the light emitting elements
obtaining a digital image of the film following deposition, the digital image encompassing the area of predetermined dimensions for the one of the light emitting elements,
masking the digital image to isolate image data corresponding to the area of predetermined dimensions for the one of the light emitting elements,
processing the isolated image data to emphasize gradients in the isolated image data which are greater than a non-zero threshold,
dependent on the emphasized gradients which are greater than the non-zero threshold, identifying the existence of a defect; and
automatically identifying a quality issue for the film deposited on the substrate, dependent on said identifying.
2. The computer-implemented method of claim 1 , wherein:
the light emitting elements each are a respective pixel of an electronic display device;
the computer-implemented method further comprises printing a liquid coat on the substrate to form the film, processing the liquid coat to convert the liquid coat to a layer of the respective pixels, using a camera to capture at least one digital image, and storing the at least one digital image in computer-accessible storage;
the display device is to be formed via a sequence of fabrication processes that in succession are to form respective layers of each of the respective pixels; and
the printing, processing and using the camera are each performed in association with given one of the fabrication processes, following completion of at least one process that precedes the given one of the fabrication processes in the sequence, and prior to the commencement of at least one process that follows the given one of the fabrication processes in the sequence.
3. The computer-implemented method of claim 2 , wherein using the camera to capture comprises imaging the layer after the liquid coat has been processed to convert the liquid coat to the layer, and wherein masking the digital image and processing the isolated image data are performed for each pixel of the display device.
4. The computer-implemented method of claim 2 , wherein the method further comprises initiating a remedial measure in the event the quality issue is identified, prior to commencement of the at least one fabrication process in the sequence that follows the given one of the fabrication processes in the sequence.
5. The computer-implemented method of claim 4 , wherein initiating the remedial measure in the event the quality issue is identified comprises interrupting the sequence.
6. The computer-implemented method of claim 1 , wherein:
the light emitting elements each are organic light emitting diodes (OLED) in a display device;
the computer-implemented method further comprises printing the layer as a liquid coat on the substrate to form the film, the liquid coat carrying an organic material, and processing the liquid coat to convert the liquid coat to a layer of the OLEDs; and
processing the liquid coat further comprises performing one of baking or curing the liquid coat to form the layer.
7. The computer-implemented method of claim 1 , wherein the light emitting elements are each light emitting diodes, wherein the film is to be formed within confines of a structural well respective to each of the light emitting elements, and wherein the masking the digital image comprises:
processing the digital image to detect the structural well for the one of the light emitting elements;
detecting the confines;
forming a mask image in dependence on the detected confines, the mask image to pass image data within the confines while masking image data outside of the confines; and
applying the mask image to the digital image, to pass image data within the confines, to thereby obtain the isolated image data.
8. The computer-implemented method of claim 1 , wherein processing the isolated image data to emphasize gradients in the isolated image data which are greater than a non-zero threshold comprises processing brightness values for the isolated image data, to convert the brightness values to gradient values, and comparing the gradient values to the non-zero threshold, to identify those gradient values which are greater than the non-zero threshold.
9. The computer-implemented method of claim 8 , wherein processing the brightness values to convert the brightness values to the gradient values comprises applying a Sobel operator to monochromatic brightness values to obtain the gradient values.
10. The computer-implemented method of claim 1 , wherein the non-zero threshold is a first threshold, and wherein identifying the existence of the defect comprises:
computing at least one numerical value dependent on a number of the gradients which are greater than the first threshold and dependent on magnitudes respectively associated with the gradients which are greater than the first threshold;
comparing the at least one numerical value with at least one second threshold; and
identifying the existence of the defect when the at least one numerical value exceeds the at least one second threshold.
11. The computer-implemented method of claim 10 , wherein processing the isolated image data to emphasize the gradients in the isolated image data comprises processing the isolated image data to obtain gradient values, and wherein computing the at least one numerical value includes identifying a number of the gradient values which exceed the non-zero threshold.
12. The computer-implemented method of claim 10 , wherein processing the isolated image data to emphasize the gradients in the isolated image data comprises processing the isolated image data to obtain gradient values, and wherein computing the at least one numerical value identifying a magnitude for each of the gradient values which exceed the non-zero threshold, computing for each of the gradient values a quantity correlated with the absolute value of the associated corresponding magnitude, and summing the quantities.
13. The computer-implemented method of claim 12 , wherein computing the at least one numerical value also includes identifying a number of the gradient values which exceed the non-zero threshold.
14. The computer-implemented method of claim 13 , wherein:
the at least one second threshold comprises a third threshold and a fourth threshold;
the at least one numerical value comprises a first number and a second number that respectively represent the number of the gradient values which exceed the non-zero threshold and the sum; and
automatically identifying the defect comprises determining that a defect exists when the first number exceeds the third threshold and when the second number exceeds the fourth threshold.
15. The computer-implemented method of claim 1 , wherein the defect is at least one of a fill defect or a delamination defect.
16. For use in a system that fabricates light emitting elements on a substrate, the system comprising a printer to deposit a liquid coat on a substrate, the liquid coat to be processed to convert the liquid coat to a layer in respective light emitting elements fabricated on the substrate, in a manner that spans for each of the light emitting elements an area of predetermined dimensions, an improvement comprising, in a subsystem that monitors quality of a film formed from the liquid coat:
for each one of the light emitting elements
obtaining a digital image of the film following deposition by the printer and processing of the liquid coat to convert the liquid coat to the layer, the digital image encompassing the area of predetermined dimensions for the one of the light emitting elements,
masking the digital image to isolate image data corresponding to the area of predetermined dimensions for the one of the light emitting elements,
processing the isolated image data to emphasize gradients in the isolated image data which are greater than a non-zero threshold,
dependent on the emphasized gradients which are greater than the non-zero threshold, identifying the existence of a defect; and
automatically identifying a quality issue for the film deposited on the substrate, dependent on said identifying.
17. The improvement of claim 16 , wherein:
the light emitting elements each are a respective pixel of an electronic display device;
the improvement further comprises printing a liquid coat on the substrate to form the film, processing the liquid coat to convert the liquid coat to a layer of the respective pixels, using a camera to capture at least one digital image, and storing the at least one digital image in computer-accessible storage;
the display device is to be formed via a sequence of fabrication processes that in succession are to form respective layers of each of the respective pixels; and
the printing, processing and using the camera are each performed in association with given one of the fabrication processes, following completion of at least one process that precedes the given one of the fabrication processes in the sequence, and prior to the commencement of at least one process that follows the given one of the fabrication processes in the sequence.
18. The improvement of claim 17 , further comprising interrupting the sequence in the event the quality issue is identified.
19. The improvement of claim 16 , wherein:
the light emitting elements each are organic light emitting diodes (OLED) in a display device;
the liquid film is to carry an organic material; and
the processing of the liquid film includes one of baking or curing the liquid coat to form the layer.
20. The improvement of claim 16 , wherein the light emitting elements are each light emitting diodes, wherein the film is to be formed within confines of a structural well respective to each of the light emitting elements, and wherein the masking the digital image comprises:
processing the digital image to detect the structural well for the one of the light emitting elements;
detecting the confines;
forming a mask image in dependence on the detected confines, the mask image to pass image data within the confines while masking image data outside of the confines; and
applying the mask image to the digital image, to pass image data within the confines, to thereby obtain the isolated image data.
21. The improvement of claim 16 , wherein the non-zero threshold is a first threshold, and wherein identifying the existence of the defect comprises:
computing at least one numerical value dependent on a number of gradients which are greater than the first threshold and on magnitudes respectively associated with the gradients which are greater than the first threshold;
comparing the at least one numerical value with at least one second threshold; and
identifying the existence of the defect when the at least one numerical value exceeds the at least one second threshold.
22. The improvement method of claim 16 , wherein processing the isolated image data to emphasize the gradients in the isolated image data comprises processing the isolated image data, to obtain gradient values, and wherein computing the at least one numerical value includes identifying a number of the gradient values which exceed the non-zero threshold.
23. The improvement of claim 16 , wherein processing the isolated image data to emphasize the gradients in the isolated image data comprises processing the isolated image data to obtain gradient values, and wherein computing the at least one numerical value identifying a magnitude for each of the gradient values which exceed the non-zero threshold, computing for each of the gradient values a quantity correlated with the absolute value of the associated corresponding magnitude, and summing the quantities.
24. The improvement of claim 23 , wherein computing the at least one numerical value includes identifying a number of the gradient values which exceed the non-zero threshold.
25. The improvement of claim 24 , wherein:
the at least one second threshold comprises a third threshold and a fourth threshold;
the at least one numerical value comprises a first number and a second number that respectively represent the number of the gradient values which exceed the non-zero threshold and the sum; and
automatically identifying the defect comprises determining that a defect exists when the first number exceeds the third threshold and when the second number exceeds the fourth threshold.
26. The improvement of claim 16 , wherein the defect is at least one of a fill defect or a delamination defect.