FILENAME: OPTICAL ENCODERS

This documentation consists of four files (with five figures), as follows:

1. Principles of operation (incl. Fig. 1 and Fig. 2)
2. Schematic_1 (Fig. 3 ), (related to "Principles of operation")
3. High density optics (Fig.4)
4. Schematic_2 (Fig. 5) (related to "High density")

1. PRINCIPLES OF OPERATION

As shown in Fig. 1. optical sensor (IC6) is in the middle of darkness, when
another sensor is on the edge. This arrangement corresponds to 90 Degrees
shifted signals, and is basics for explained solutions in this document.
With detector circuit in Fig. 3, is possible to obtain both, up/down and count
signals. The corresponding pulse diagrams are shown in Fig. 2. It is "visible"
that count signal comes after predefined up/down level.

Count signal is generated on every edge of optical disc (black-to-white and
white-to-black).If you don't need up/down information, you can exclude IC7,
N8 and N12 components (Fig. 3)

NOW COMES HIGH DENSITY ENCODER DISC !

On Fig. 4 you can see a copy of early Siemens application. This arrangement is
only for counting,(without direction of rotation). The principle of operation
is like previous solution, but resolution is increased using Raster mask element.
This element is obtained as segment of optical disk, he has identical dimensions
of black and white segments. In this arrangement, when black segments of disc
overlapps white segments of raster mask, receiver is in dark. When black segments 
are on black, receiver is 50 % enlighted. In this way you can get high
resolution on small disc.

Schematic on Fig. 5 is used to decode signals form optics on Fig. 4. Again, if
no direction information is needed, U1, U3a and U3b, with their passive 
components are ommited. The principle of operation is the same
as in previous solution. Normally, if one need direction information, must make
two optical systems, arranging them in 90 Degrees shifted positions, and all of
electronics in Fig. 4.

I designed my optical disc in CorelDraw, and maked standard positive film, then
mounted on the rotated shaft. I made raster mask as a smal segment of optical
disk, and as "twins" positioned about 10 mm one from another. One part of
"twins" is rotated, to obtain 90 Degrees shifting.

On the end, I hope my English is understndable, because i never learned in the
shool.
I'm ready to obtain any further information, when needed.
Best regards
mr_peja