OCR (Optical Character Recognition) is the input device that converts bitmap images of characters to equivalent ASCII codes. OCR is a technology that allows computers to recognize printed or written text characters and convert them into machine-readable text. It is widely used to digitize printed documents so that they can be edited, searched, and stored more compactly.

OCR works by utilizing advanced image processing algorithms to analyze the shapes and patterns of characters in a bitmap image. It identifies the individual characters and then converts them to their corresponding ASCII codes. ASCII (American Standard Code for Information Interchange) is a character encoding standard that assigns unique numeric codes to represent each character.

Let's explore the other options and understand why they are not the correct answers:

- OMR (Optical Mark Recognition): OMR is a technology that is used to detect and recognize predefined marks or patterns on paper forms. It is commonly used in surveys, questionnaires, and multiple-choice examinations. OMR is not designed to convert bitmap images of characters to ASCII codes.

- Scanner: A scanner is a device that captures images, documents, or objects and converts them into digital images. While a scanner can create bitmap images of characters, it does not have the capability to convert them into ASCII codes. The conversion process requires OCR technology.

- Touch Screen: A touch screen is an input device that allows users to interact with a computer or electronic device by touching the display. It does not have the capability to convert bitmap images of characters to ASCII codes.

In conclusion, OCR is the correct answer because it is specifically designed to convert bitmap images of characters into equivalent ASCII codes. This technology plays a crucial role in digitizing printed documents and making them machine-readable.