The use of optical systems for identifying objects has applications in a wide variety of fields. For example, optical systems can be used to generate color images of documents, to compare two documents or to compare a document with stored data to determine whether the document matches the stored data. At least some known optical systems include multiple sensors with multiple lenses or a single sensor with multiple lenses. However, in at least some of these known systems, it can be difficult and time consuming to adjust the lens system to achieve a desired image quality across the entire image area. In addition, because sensors are typically sensitive to dust particles, particles in the air entering the camera system can produce artifacts in a video stream generated by the imaging system. In order to prevent dust from entering the system, the lens system is often placed at a substantial distance from the imaging sensor. However, at least some known optical systems are unnecessarily large and expensive to manufacture, use and maintain, or require a large amount of time to position the lens system and maintain a desired focus of the lens system. For example, one existing arrangement includes a single sensor and four lenses. The four lenses are positioned in front of the sensor. Two of the lenses have a positive power (e.g., to focus incoming light) and the other two lenses have a negative power (e.g., to disperse the incoming light). Accordingly, when a lens system having four lenses is used to provide focusing and image separation, this arrangement provides focusing at either a front focal position or a back focal position, but not at both positions simultaneously. As a result, the lens system must be first focused at the front focal position, and then refocused at the back focal position to achieve simultaneous focusing. At least some other existing systems use an arrangement including a single lens that is tilted at various angles with respect to the sensor. At least some of these known systems tilt the lens at a wide angle position relative to the sensor to achieve both front and back focusing, while other known systems tilt the lens at a narrow angle relative to the sensor to focus at a front focal position. However, these systems suffer from the problems noted above. Additionally, these systems fail to provide good optical quality when the lens system is focused at either the front focal position or the back focal position. For example, the lens system may produce artifacts or shadows. When the lens system is focused at the front focal position, the image quality can be improved by increasing the aperture of the lens system. However, at the back focal position, the image quality can be degraded if the aperture is increased because the lens system is not within a depth of field of the camera system. Furthermore, this arrangement typically uses a large sensor which increases the size of the system. Additionally, this arrangement requires that a relatively long fiber optic cable be used to transmit the image from the lens system to the sensor. Additionally, some known systems include a single-sensor having a relatively long optical path (i.e., the distance from a target to the sensor) relative to the size of the target. These systems typically use expensive components to obtain good resolution. However, as the size of the target decreases, the cost of the system increases as the sensor size increases. Because of these and other problems of known optical imaging systems, it is desirable to provide an optical imaging system and method that improves image quality and that is relatively easy to manufacture. It is also desirable to provide an imaging system and method that can be used in various different environments.