Dim Lines in OLED Display

[desertsky]

Hello everyone,
I've been working with the CFAL128128A0-015X display, and I've noticed something on my display:

There are dim lines running through the display, I've noticed they fall on rows where more of the pixels are lit up. My gut instinct is to mess with the value of the current sense resistor. Before I start doing some rework in a difficult area of my pcb I wanted to check in here to see if anyone else has seen this behavior and if it is in fact related to the current sense resistor value. Also, to increase the current limit of the display, do I need to increase or decrease the resistance on this resistor?
Schematic attached, resistor in question is R9:

Thank you!
-Andy

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[CF Kelsey]

Hi Andy,

This isn't a problem with your design, but instead is an effect of OLED technology. When more pixels on a common line are on, the impedance on that line is increased and thus the current through the OLEDs is lowered resulting in a less bright pixel.

There are a few things you could do to mitigate this effect.

1. Modify the brightness (gray scale) of the affected pixels. The SSD1327 controller in this display allows for individual pixel gray scale settings. You can read about it in section 7.2 of the SSD1327 datasheet
2. Reduce the overall brightness of the pixels to make the effect less obvious.
3. Modify the UI layout to spread the lit pixels more evenly across the lines of the display.

You can see in our demo photo that we did not mitigate the effect and the rows with more pixels on are dimmer: