Geoscope Standard - adding baffles
The Geoscope Standard is a fine stereoscope for viewing widely separated stereoscopic images but it does not include sufficient light baffles to block secondary images and light leaks and these cause a lot of confusion for people inexperienced at viewing stereoscopic images and also lessens the immersion. Some simple baffles for the Geoscope are proposed below.
The most immediate secondary images are those directly adjacent to the first mirror and their proximity to the main image makes them particularly distracting. These secondary images are a direct view of the target and have not been attenuated by the mirrors so they are significantly brighter than the main image, and the path length to these images is different to the main image so they will appear blurry when focused on the main image. These secondary images are circled below.
Fortunately a simple baffle placed on the bottom of the Geoscope can block a good portion of these secondary images. The mirrors in the Geoscope are not as large as the optical paths would permit giving room to add this baffle without blocking the main image and it was possible to extend the baffle 3/4 inch each side of the middle section of the Geoscope. The middle section of the Geoscope has a large hole for your nose to fit and in order to allow ventilation the baffle attached to the bottom can include openings at the top a bottom. If this baffle is made of a thin and strong material then it can remain attached when packing the Geoscope.
The results below show the significant improvement achieved with this simple and convenient baffle installed.
While the above baffle is a significant improvement there remain wider secondary images, from wider direct views that are not blocked by the bottom baffle and from reflections from the large outer mirrors, as illustrated below.
These secondary images can be blocked with a baffle on the top of the viewer. The baffle needs to be high enough to avoid blocking the light path from the first to the second mirror and a baffle fitting over the eyepiece was constructed from cardboard, and includes legs to hold the hight even without the eyepiece installed.
The view below illustrates the blocking of these secondary views. A small secondary view remains in the photograph and is a direct view that could not be blocked without interfering with the optical path, however this photograph was taken from a very acute angle to show the blocking of the side images and in typical viewing this secondary image may not even be visible.
A light leak from past the bottom of the large mirrors is also distracting. The mirrors are not as large as possible for a viewer this size and under certain viewing conditions it is possible to see past the bottom of the large outer mirror and if you are in a bright room then this can be a bright reflection and distracting as illustrated below. Note that reflections from outside the top of the large outer mirrors are already blocked by the top baffle.
This light leak can be blocked by a baffle that extends below the outer mirrors, and it can well be incorporated into the top baffle as shown below.
Below its can be seen that is light leak has been blocked. If the green legs are also distracting then this baffle could be moved to the inside of the legs and if constructed from a strong and thin material then it may well be possible to leave it installed when packed.