BC20 | Laser Photodiode Sensors | Power Sensors - Ophir



The BC20 is a photodiode sensor for measuring scanned or intermittent beams such as bar code scanners. It has a swivel mount and a 10x10mm aperture. It covers the spectral range 400-1100nm and its power measuring range is 0.1mW - 20mW. The sensor comes with a 1.5 meter cable for connecting to a meter or PC interface.


  • 10x10mm
  • 400-1100nm
  • 0.1mW-20mW
  • 118 L x 10 W x 18 D (mm)
  • N.A
  • 50W/cm²
  • 20mW
  • CE, UKCA, China RoHS
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How does the BC20 measure the true power of a scanned beam?

The BC20 has a peak measurement and hold circuit which measures the peak power on the detector and holds it. Therefore when a beam is scanned over the detector, when the beam is on the detector it goes up to a peak which corresponds to the same power the detector would measure if the beam was stationary and therefore the BC20 reads the correct power whether the beam is scanned or not. In order for the BC20 to do this, the beam must be on the detector (of size 10x10mm) for at least ~13µs and therefore this limits the scanning speed on the detector to 30,000 inch/s.

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What does the PD300 "Background Subtraction" do?

Ophir's Photodiode PD300 and PD300-1W sensors offer automatic background subtraction so the measurement is not sensitive to room light. With "filter out" (i.e. the external filter removed for low light measurements), 2 separate detector elements are visible. The beam to be measured is incident only on the outer of the 2 detectors, but background light reaches both detectors. The instrument will show the power measured by the outer detector minus that measured by the inner detector.This patented method cancels out 95% - 98% of background light under normal room conditions, even if it is constantly changing.

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Do I need to recalibrate my instrument? How often must it be recalibrated?

Unless otherwise indicated, Ophir sensors and meters should be recalibrated within 18 months after initial purchase, and then once a year after that.

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Why won’t a BC20 sensor work with the StarLite display?

The BC20 sensor was not intended to be used with the StarLite display. If you use the Nova II or Vega display it will work.

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Measuring power of scanned beams using the BC20 Measuring power of scanned beams using the BC20
FAQ: Photodiode Sensors for measuring very low laser powers FAQ: Photodiode Sensors for measuring very low laser powers FAQ: Photodiode Sensors for measuring very low laser powers

In this short “Basics” video, we review in general the use of photodiode sensors for measuring very low laser powers.

How to measure power of very low power pulsed laser beams How to measure power of very low power pulsed laser beams How to measure power of very low power pulsed laser beams

When using a photodiode laser power sensor to measure very low power pulsed beams (nW to mW), there are some issues you need to be aware of. This video shows you how to avoid some common problems and ensure maximum accuracy.

Photodiode Sensors for Measuring Very Low Powers Photodiode Sensors for Measuring Very Low Powers Photodiode Sensors for Measuring Very Low Powers

In this short "Basics" video, we review in general the use of photodiode sensors for measuring very low laser powers.

In this video, you will learn how the BC20 sensor enables correct power measurement of scanned beams, such as are used in barcode readers, laser shows and similarly challenging applications.


Tutorials and Articles

Laser Power Sensors introduction

As described in the general introduction, the thermopile sensor has a series of bimetallic junctions. A temperature difference between any two junctions causes a voltage to be formed between the two junctions. Since the junctions are in series and the «hot» junctions are always on the inner, hotter side, and the «cold» junctions are on the outer, cooler side, radial heat flow on the disc causes a voltage proportional to the power input. Laser power impinges on the center of the thermopile sensor disk (on the reverse side of the thermopile), flows radially and is cooled on the periphery. The array of thermocouples measures the temperature gradient, which is proportional to the incident or absorbed power. In principle, the reading is not dependent on the ambient temperature since only the temperature difference affects the voltage generated and the voltage difference depends only on the heat flow, not on the ambient temperature.


Common Reasons for Photodiode Sensor Damage or Out of Tolerance Conditions

We have included this document with your recent calibration order because we have noticed an out of tolerance condition obtained from your equipment when returned for calibration. This document was created to assist our valued customers in the proper care and maintenance of Ophir photodiode sensors. The following information is for reference only. If you have any reason to believe that the sensor is no longer performing within the original specifications, we always recommend that you send it in for repair and/or recalibration by our trained technicians to bring the unit back to the proper NIST traceable standards.

Ophir photodiode sensors can be used for many years without any repairs when used with the proper laser optical setup. Many of our customers have sensors that are using their original absorber that are over ten years of age. We hope that this document will enable you to also enjoy the long life and reliable results that Ophir- Spiricon is known for.


Are You Safe at a Laser Light Show? Using the Ophir BC20 to Evaluate Scanned Effects in Light Show Applications

The assessment of laser beam exposure used for entertainment applications is a challenging undertaking; both the emission and the environment pose particular obstacles to persons with the responsibility of ensuring emissions are below the permissible exposure limits. This article discusses how use of Ophir’s BC20 detector is able to offer significant improvements in measurements quality over traditional laser power detectors intended for CW beams. In addition, the BC20 simplifies the measurement process and allows measurement of live effects, opening the way for assessments to be undertaken with a much greater degree of accuracy. This provides benefits to assessors, whether they are operators, venue safety staff, or regulators, who can now additionally monitor emissions and ensure they are not exceeded during performances.


Effect of Ambient Conditions on Laser Measurements

We are often asked about the specified ranges of various ambient conditions (temperature, humidity, etc.) for Ophir instruments. In this article we will clarify the effects of these conditions on laser measurements, so you’ll be able to use your Ophir laser measurement instrument effectively.


Ophir Power/Energy Meter Calibration Procedure and Traceability/Error Analysis

This document discusses the interpretation and basis for stated measurement accuracy of Ophir Laser Power/Energy meters.
1. General Discussion
2. Combination of Errors and Total Error
3. Analysis of Power and Energy Calibration Errors
4. Detailed Analysis of Power and Energy Calibration Errors


Laser Measurements in Materials Processing: How and When They Absolutely, Positively Must Be Made

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5 Situations Where Laser Performance Measurement is Necessary

Measuring the performance of a laser has possible for a number of years and is accomplished with a variety of techniques. These electronic laser measurement solutions give the laser user more relevant, time-based data that shows trends in laser performance rather than single data points. While these solutions have provided laser users with the ability to present data in a simple and easy to understand manner, the application of the data still seems to be unclear to many laser users. Read more...