Software, and Applications
9.1 COMBINING OPTICS, ELECTRONICS, AND SOFTWARE
Many modern optical systems include a combination of optics, electronics, software,
and/or rmware. Because each of these portions of the system is interrelated with
the other, understanding the capabilities of all three is crucial for an optimal design.
Additionally, many portions of the current optical systems utilize digital electronics
and microprocessors to replace some of the functionality that used to be performed
optically or using analog electronics.
For example earlier spectrometers that analyzed light transmission utilized a
reective chopper wheel to obtain a reference signal from a blank (e.g., a glass) and
another through the sample under test (e.g., a glass coated with the material under
test). The signal from two photodetectors was subtracted using analog electronics.
With the current spectrometers that utilize solid-state detector arrays and digital
electronics, this procedure has been simplied, and similar results are achieved with
much smaller apparatus and at much rapid rate. First, a scan of through a reference
sample is obtained (e.g., a glass substrate), saved in the spectrometer as background,
and then the sample is scanned, and transmission through the sample is displayed
in real time, referenced to the glass substrate that the sample material is coated on.
Another example is optical image processing, where earlier work on correlation
and ltering was performed optically because of the large set of image data and
the need for computationally intensive processing. Today much of the processing
is performed using digital processing electronics, while optics is used primarily for
The advantage of using digital electronics and software is the ability to upgrade
and optimize without the need for major hardware changes. This is why it is ever
more important to have a good understanding of the capabilities of all three: optics,
electronics, and software/rmware/processing.
For example, if designing a system that is used to perform three-color measure-
ment on a print based on red, green, and blue (RGB) light-emitting diodes (LEDs),
one option is to utilize an illumination system that is designed to maintain con-
stant illumination of all three bands (RGB). This could be prohibitively expensive.
If possible, a referencing system may be employed as shown in Figure9.1. A known
stationary reference can be placed in the system such that the response can be
simultaneously measured, and the signal can be calibrated. For example if the red
and blue LED intensities shift with respect to the green LED, then the print being
tested will appear more green than it actually is. By dividing the raw data with the