| Adjusting Image Alignment |
Last Modified: 2006-10-23
In some camera modules for the CMUcam kit, the lens housings may not be centered properly. The result can be a large offset in the image. The image the camera should see and the image actually captured by the camera may be shifted by many pixels. The following procedure may be used to correct this offset. A small offset of a few pixels is normal. This procedure is only recommended for extreme offset problems.
Front of camera board.
It is possible to change the horizontal alignment of the image by replacing the lens housing screws with smaller machine screws. The new smaller screws make it possible to adjust the lens housing position.
This procedure uses some very tiny screws and nuts. Use care when handling them. It is easy to drop them and lose them on a carpet, down a crack in a floor, etc.
Remove one of the lens housing screws with a small Philips head screwdriver. Removing just one of the screws at this time will make the next step easier.
Removing the screws.
Insert a 0-80 3/8 inch screw up through the empty screw hole in the camera board, through the empty hole in the lens housing, and secure loosely with a matching nut. (Any screws roughly 1mm or smaller in diameter and at least 12mm long should work. The thread does not matter since the new screws will be small enough to pass through the lens housing mounting holes.)
Red line pointing to placement of the new screw.
Repeat the screw replacement for the other side of the lens housing.
Find the "J2" label on the lens side of the board. Slide the lens housing towards the side of the board farthest from the J2 label until the screws prevent any further motion. Secure the screws. You should be able to see a tiny hole right next to the lens housing, as shown in the photo below.
New lens position. Red line pointing to tiny hole in PCB.
If additional adjustment of the lens housing is desired, the screw holes may be filed or drilled to make them larger. This increases the risk of damaging the board so it is not recommended.
This page describes a remedy for horizontal image alignment problems in some CMUcam camera modules. A variation on this technique could also be used to add an arbitrary vertical offset.
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