A Simple Imaging Lens
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| Figure 9: Imaging using a thin convex lens |
Say you want to take a picture of your friend. Consider a single point on your friend, such as the top of her head. This point radiates light in various directions. By holding a thin convex lens in front of her, you can collect the light rays from that point and converge them onto a single point, as shown in Figure 9. Since the lens does the same thing to all the points on your friend, a complete image of her is formed behind the lens. If we place a flat board (plane) right where the light rays are being focused, we can see the image that is formed. Better yet, we can record the image by placing an image sensor or a strip of film there instead of the board. Together, the lens and the image sensor form a camera.
In order to figure out where exactly we need to place the image sensor, and how sharp and how bright the captured images will be, we need to understand some basic properties of the lens.
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