For more information, contact Optex Technologies Inc. at 800-877-6656, x123 and ask for the new interactive CD which illustrates all the features of the ProSwing Elite.

Jim Sargent

Over the last several years focused active IR sensor performance has seen significant improvement due primarily to the availability of compact high speed microprocessors and memory chips at competitive price points. The ability to process more data at a faster rate has resulted in quicker response times, more precise detection patterns and increased operating stability against environmental interferences.

How does it work?

A Focused Active IR sensor has a number of transmitter/receiver pairs. Each IR transmitter emits infra-red towards a background (the floor) and a portion of the IR is reflected back to the receiver (photo diode). During initial set up, based on the reflectivity of the operating environment, the sensor adjusts the transmitted IR to achieve a specific balance of reflected IR verses transmitted IR. This balance is referred to as the threshold level of reflected IR. When the reflected IR changes significantly above or below the threshold level (person or object entering the IR pattern) the sensor will send a signal to the door control.

A focused active IR sensor uses its Emitter / Receiver pairs to generate a matrix of IR spots on a background. In the case of an Automatic door the background is the floor. Through software the spots can be designated for presence or motion detection. Each spot actually is a presence detector but the spots can be individually programmed with a quick relearn time and act as a motion detector.

For example, in the drawing below the sensor pattern is made up of five rows. Rows one and two can be designated as presence and rows 3,4 and 5 as motion. If someone were to stop moving in rows 3 thru 5, the sensor would drop detection. In rows 1 and 2 (near the sliding panels, a motionless person would remain detected.

Some environmental conditions that or known to cause interference to IR sensors are sun light, florescent lights, rain, snow and small objects blowing around in the sensor pattern. Over the years engineers have developed an understanding of the affects of these types of interferences and have developed programming to increase stability and nearly eliminate all adverse affects.

One of the biggest improvements achieved in active IR sensors is the increased ability to detect people or objects regardless of color and texture. A known characteristic in IR technology is that the reflectivity of IR is affected by texture and color of different objects. A bright white tile floor has a higher reflective quality than a dark carpeted floor. A blue denim jacket has a lower reflective quality than a white polyester lab coat.

Earlier versions of Diffused Active IR sensors required an increase in reflected IR above its normal threshold level in order to change states and send an output signal to the door control.

The picture & graph below depicts a threshold level of returned IR of 5. When a person enters the pattern and the sensor detects a sufficient increase in reflected IR above the threshold level it goes into detection mode and sends a signal to the door control. This meant that a person wearing clothing with a low reflectivity characteristic might have to get further in the detection pattern to initiate the required return before being detected. This type of sensor has been, and continues to be, reasonably safe. Focused active IR sensors, however, improve the consistency of the detection pattern.

Focused Active IR sensors can place an upper and lower trigger point around the threshold IR level. The graph below represents a sensor with an upper trigger point (an increase of reflected IR) and a lower trigger point (a decrease in reflected IR) created around the threshold level. Anything entering the IR pattern that results in a significant decrease of reflected IR, as well as an increase, will put the sensor into detection. Texture and color of an object now has a more even affect on the sensor increasing the stability and reliability of the detection area.

Simply stated when the sensor detects sufficient contrast between a target and the background it sends a signal to the controller.

Small changes in the detection area (such as blowing leaves, small insects, lights turning on or off) result in changes of the reflected IR that remain well within the bandwidth created by the upper and lower trigger points. These items do not cause the sensor to detect, however, anything entering the IR pattern that results in a significant decrease, as well as an increase, of reflected IR (person entering the sensor pattern) will put the sensor into detection.

These are just the basics about focused active IR sensors. There are other things to know about active IR sensors such as presence timers, operational modes (rain mode, snow mode), frequency settings, and sensitivity adjustments. These things are accomplished in different ways by different manufacturers. For questions regarding these issues, contact the manufacturer of the specific sensor you are curious about.

Following are several key points that will help you gain accurate information.

• Have a questioning plan.
• When you are negotiating, it is important to have a goal in mind and to have a questioning plan that will help you achieve that goal.
  • What type of information will help you in making a good decision?
  • How will you go about getting that information?
  • Will you be direct?

• Move from the broad to the narrow
• It is helpful to start with broad questions. Then, as you gain answers to broad questions, you can refine and hone your questions to eventually yield specific information.

• Ask permission to ask a question
• Asking permission is more than the polite thing to do. Once your counterpart has granted you permission, he is more likely to give you a complete answer. An example is, “Can I ask you a question about _______?

• Have proper timing
• We have all experienced situations where we asked the wrong question at the wrong time. If this happens, consider leaving and come back later if appropriate.

Peter B. Stark, president of Peter Barron Stark & Associates, Inc., travels internationally, speaking and training business leaders in the art of negotiation. He lives in Poway, California, with his wife and their three children.