On most nights, Tom Yeh puts his 3Â-year-Âold son on his lap, opens a children's book and reads aloud. It's a muchÂ-loved activity for both father and son as the characters are brought to life. A year ago, while reading the children's classic Goodnight Moon , Yeh, an assistant professor in computer science, began thinking about how to make books more accessible to visually impaired preschool-Âage children.