Yubo

Introduction

Autofocus is one of the three basic camera auto-algorithms enabled in most consumer photography cameras, with the other two being auto-exposure and auto-white balance. Out of the three, both autofocus and auto-exposure requires a feedback mechanism to adjust physical characteristics of the camera lens or sensors, respectively. In the case of autofocus, the software will evaluate whether or not the captured image is in focus, and will adjust the lens position for subsequent captures if it is not.

This project will focus specifically on simulating the VCM focuser. The VCM focuser implemented in this project utilizes exclusively contrast detection, and does not use phase detection. In a VCM focuser, the camera is attached in a VCM barrel with springs on one side of the barrel, and a magnet on the other. The magnet is controlled using an electric current. When the magnet is inactive, the springs will hold the lens at the rest position, which usually focuses at infinity. When the magnet is activated, depending on the current, will move the lens to specified positions within the barrel.

This project attempts to provide a virtual focuser implementation and a basic autofocus algorithm to evaluate. There are many different focuser types, many of which have been covered in the lectures. There are many benefits to creating a virtual focuser. First, it allows the tweaking of physical focuser characteristics, without having to rely on an abundance of physical focuser modules. Second, it abstracts away the reliance on hardware when evaluating autofocus algorithms. This enables camera software developers to perform system and regression tests on a cloud environment without having to set up a static and controlled scene.

Related Lecture Material

Lecture 1 defines a scene to be in focus when it satisfies the lens maker equation (thin lens approximation):