# A Deep Learning Technique for Optical Inspection of Color Contact Lenses
## 4 Results and Discussion  
The manufacturing process for color contact lenses necessitates high precision and attention to ensure that the lenses are safe, comfortable, and provide the desired color effect for the wearer. The color contact lens has a transparent pupil part, and the surrounding iris section has a colorant applied in a pattern to the entire user iris. A contact lens manufacturing process via cast molding was performed according to the following steps. (i) A plastic manufacturing mold was provided. (ii) At least one imprint with lens material was deposited on the surface of said mold via silicon pad printing and dried using a blank annular plate. (iii) A colorant was deposited on the dried imprint via pad printing. (iv) The mold was filled with the lens material. (v) The lens material was polymerized. \begin{table}
\begin{tabular}{c c} \hline \hline
**Field** & **Specification** \\ \hline Training Solver & SGDM \\ Batch Size & 64 \\ Epochs & 100 \\ Initial Learning Rate & 0.001 \\ Learn Rate Schedule & Piecewise \\ Learn Rate Drop Factor & 0.15 \\ Learn Rate Drop Period & 20 epochs \\ Shuffle & Every epoch \\ Validation Frequency & 10 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Secondary training parameters. Figure 9: Confusion matrix of test result. (vi) The polymerized lens was separated from the molds. (vii) The swelling process of the contact lens applicable to a hydrogel state was applied. Finally, (viii) images were collected for the optical inspection of the colored contact lenses (Figures 10 and 11) [26,27]. In step (iii), a pad composed of silicon rubber, impregnated with silicon oil for easy release, was pressed against the laser engraving patterns. Subsequently, the colorant from the prepared colorant-containing solution was obtained. The colorant on the pad was transferred to the front surface of the coated upper mold, thus depositing the colorant in the desired pattern over the iris section. The printing step may be repeated one or more times using different patterns in different colors. Before the lenses were packaged, they were subjected to an inspection process to ensure that they satisfied the quality standards. This inspection step included checking for defects such as bubbles, scratches, or uneven coloring. Notably, according to the patterns and colors of the contact lenses, the recognition rate may vary depending on the individual inspector. Contact lenses comprise p(HEMA) networks that are chemically crosslinked, as shown in Figure 12. Initially, p(HEMA)-based contact lenses were synthesized via free radical polymerization with hydrophilic HEMA monomers using EGDMA as a crosslinking agent and AIBN as the initiator. The physical properties, such as elasticity and tensile strength of the contact lens, may vary depending on the ratio and species of the crosslinking agent and the monomer used. In this study, contact lenses were manufactured using the simplest and most common materials and ratios. Prior to the polymerization to obtain the contact lenses, the coating solution was prepared and immobilized on the surface of the upper mold. The coating solution prevented the colorant from eluting out of the lens. Poly(ethylene glycol) methyl ether methacrylate with a high molecular weight was added to the coating and  
Figure 11: Images of molds and colored contact lenses during the printing and curing processes: (**1**) coated upper mold, (**2**) color-printed upper mold, (**3**) lens-material-filled lower mold, (**4**) combination of color-printed upper mold and lens-material-filled lower mold, (**5**) obtained colored contact lens after removing the molds, and (**6**) colored contact lenses under swelling. Figure 10: Photographs of the contact lens manufacturing processes (provided by Jckmedical Co., Ltd., Gwangju, Republic of Korea). colorant-containing solutions to increase the viscosity of the solutions, thus preventing their flow down from the mold. The most important features of commercially available contact lenses are optical transparency, diameter, and WC.