# Research of Tri-State Optical Signal Detectors for Ternary Optical Computers
## 2 Materials and Methods
### Theory of Three-State Optical Signal Detectors  
#### 2.2.1 Photoelectric Conversion  
The main objective of this study is to accurately convert the 576 polarized optical signals from an optical operator to the corresponding electrical signals.  
Ideally, the same polarized light would be presented with the same light intensity on the top LCD of each processor bit. The optical operator of the SD16 uses a backlight board as the light source [12], which in theory should be a uniform-intensity light source. However, the structure of the backlight board determines that it is not a uniform light source. There are seven LED beads inside the backlight board, and their positions are shown in Figure 3. They are concentrated on one edge of the backlight board, and the light source of the LED beads is reflected to other parts of the backlight board through the internal reflection film. This causes the light intensity near the LED beads to be stronger, while away from the LED beads, the light intensity is weaker, ultimately presenting the inconsistent light intensity of the LCD pixels.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**First** & **First Liquid** & **Second** & **Second Liquid** & **Third** & **Third Liquid** & **Fourth** & **Light** \\
**Polarizer** & **Crystal** & **Polarizer** & **Crystal Layer** & **Polarizer** & **Crystal** & **Polarizer** & **Highness** \\
**Layer** 2 & **Layer** & **Layer** & **Crystal Layer** & **Layer** & **Layer** & **Layer** & **Hight** \\ \hline V & 0 1 & W & 0 & W & 0 & W & Dark light state \\ V & 0 & W & 0 & W & 1 & W & Dark light state \\ V & 0 & W & 1 & W & 0 & W & Dark light state \\ V & 0 & W & 1 & W & 1 & W & Dark light state \\ V & 1 & V & 0 & W & 0 & W & Dark light state \\ V & 1 & V & 0 & W & 1 & W & Dark light state \\ V & 1 & V & 1 & V & 0 & H & secondary bright state \\ V & 1 & V & 1 & V & 1 & V & Strong bright state \\ \hline \hline \end{tabular} Note: 1 0 indicates the control signal is not given, and the liquid crystal keeps rotating the light (such as changing V light to H light); 1 indicates the control signal is given, and the liquid crystal does not rotate the light. 2 The 1 st, 3 rd, 5 th, and 7 th columns are the light states after the light passes through the polarizer.  
\end{table}
Table 1: Spin light mode, output light state, and light brightness comparison table.  
Figure 2: Optical processor result graph.  
Since the actual light intensity of the liquid crystal pixels is not uniform, this study uses \"point-to-point sensing\", i.e., each liquid crystal pixel has its own corresponding photosensitive sensor and photoelectric conversion circuit. An LCD pixel will present three light intensities, so two bits of data are needed to represent them. In this paper, we specify 11 for V light, 10 for H light, and 00 for W light.  
According to this provision, this paper uses a voltage divider circuit in the photoelectric conversion circuit part to process the electrical signal from the photosensitive sensor, and the specific circuit implementation will be described in detail in Section 2.3.1.