Complete Overview and Analysis of an Electro-Luminescent Based Optical Cell

Electro-luminescent optical cells form the first layer in the unique sound of an optical compressor and are the main element in achieving gain reduction. This research was carried out in order to identify key low-level parameters within the optical cell assembly that relate to the colouration added to the musical signal. Variations of an optical cells were built, each with a modification to the identified parameter (electro-luminescent panel, light dependent resistor, exposure area, etc.). Objective analysis was performed, and multiple tests were carried out to determine the performance characteristics of each modified cell. Various stimuli were utilised which included broadband pink noise, band-limited pink noise (63 Hz band and 1 kHz band) and sine wave bursts. Further to the individual cell testing, audio measurements and analysis of the resultant signal utilising the cells within an audio compressor were undertaken.

Key findings of the report conclude that the optical cells do exhibit a ‘memory effect’ determined by the amount of compression applied. They also have a two-staged attack characteristic that is independent from the audio stimuli and a different timing response based on the combination of the two elements inside the optical cell (the Light Dependent Resistor and the Electro-Luminescent panel). Further to this, it was determined that the attack/release characteristics of the optical compressor and the Total Harmonic Distortion (THD) levels of the compressed audio stimuli changed as a direct result of the optical cell’s modified parameters. Moreover, it was proved that some electro-luminescent panels do exhibit a colour-shift phenomenon and a frequency-dependent brightness that affect the cell’s compression characteristics with different audio stimuli. Further to the findings, additional attack and release characteristics are proposed based on parameter modifications.