1. The area inside the central circle is the split image.

2. A simulative experimental instrument based on central split image focusing which is widely applied to single lens reflex camera is described.

3. An image splitting part generates split image data expressing two horizontally or vertically split images of the image expressed by manuscript image data.

4. Using the genetic algorithm, this paper solved the layout of the split image on mobile platform.

5. Then, present an improved algorithm to automatically determine the division threshold, using the gray-scale images mean and variance split image.

6. When you use a small aperture (large number aperture setting) with a lens such as a zoom lens, half of the split image becomes dark. In this case, use the matte screen to focus.