User`s manual

6.6 Range Resolution

Range resolution is the minimum distance the stereo system can distinguish.

Since stereo is a triangulation operation, the range resolution gets worse

with increasing distance from the stereo head. The relationship is:

r Δ=Δ

where b is the baseline between the imagers, f is the focal length of the lens,

and

dΔ is the smallest disparity the stereo system can detect. For the

STOC/-C, b is 90 mm, and

dΔ is 0.375 um (pixel size of 6.0 um, divided

by the interpolation factor of 16).

Table 4 plots this relationship for several focal lengths. At any distance, the

range resolution is inversely proportional to the focal length.

6.7 Changing Miniature Lenses

The STOC comes with 12 mm diameter miniature lenses glued firmly in

place. We do not recommend changing the lenses, but it is possible to do.

If the lenses are changed or in any way moved, then the device will lose its

calibration, and a calibration must be performed and the results downloaded

to the device (see the Calibration Addendum for information about

performing the calibration step). Section

8 has information about how to

download a calibration file to the STOC.

While the lenses have been glued into their holders, the hold of the glue can

be broken, and the lenses removed. Doing so may damage the lenses, and

for this reason we do not recommend changing them.

To remove the lenses, use a pliers with a soft tissue around the top of the

lens, to prevent scratching from the plier jaws. Grab the lens head firmly

with the pliers, and rotate counter-clockwise. The lens should rotate in its

socket, but it takes some force to do this.

Once the lens has been removed, use pressurized air to clean out the lens

holder. Then install the new lens, which should have a 12 mm diameter

barrel, with a screw pitch of 0.5 mm. Install the lens as described below,

and check for a good focus.

The screw mates with the lens holder opening. To insert a lens, place its

back end on the lens holder opening as straight as possible, and slowly turn

it counter-clockwise (looking down at the lens), applying some slight

pressure, until you feel a small “click”. This indicates that the threads are

in a position to engage. Without removing pressure, rotate clockwise until

the threads of the lens engage the lens holder. If you encounter a lot of

resistance, you may be cross-threading the lens. Forcing it on at this point

will damage the lens holder or lens threads.

Once the threads are engaged, continue screwing it on until some portion of

the thread on the lens barrel is in the lens holder. Then, plug in the device,

and start video streaming (in Original Image mode). Screw the lens down

Figure 6-1 Range resolution in mm as a function of distance, for

several different lens focal lengths.