ANSI/IES LM-85-23 for LED Product Design provides a framework to eliminate significant error sources present when designing end user products using LEDs. With LM-85-23 “Approved Method: Optical and Electrical Measurements of LED Sources“, optical measurements are now tied to junction temperature, eliminating a significant error source. LED measurements will now be more consistent and repeatable. But how is LM-85-23 really applied when considering LED product design? What are the short-term and long-term benefits?
This webinar occurred in August 2025. The VIDEO is available on IESNA Elearning website.
Answers to some critical questions can be found below.
What is IES or IESNA?
Founded in 1906, the Illuminating Engineering Society (IES) is the global authority on illumination offering professional development and publications
What does IES do for you?
The IES / IESNA organization offers illumination expertise. Publications, known as standards or methods, are created by industry experts who volunteer their time to share their knowledge.
What is LM-85-23?
LM-85-23 is an approved method developed by the Illuminating Engineering Society (IES) that outlines procedures for both optical and electrical measurements of LED sources. It’s specifically designed for LED packages and arrays, and can be applied to white and single-color LEDs, as well as laser diodes. The standard defines various measurement methods, including single pulse, flash pulse, continuous pulse, and differential continuous pulse methods.
What does LM-85-23 do for you?
If a product outputs light such as an LED, array or Laser, or uses these devices to output light and quality is important then consider leveraging the light measurement expertise found in this document for your own quality procedures. Note that it is difficult for anyone to complain about using standardized procedures that are published.
What makes LM-85-23 better than previous versions?
LM-85-23 ties temperature control and thermal measurements to the common electrical and optical measurements so the true device characteristic of the device can be known and the measurements can be reliably repeated.
What is the visual or practical difference someone will see when using the LM-85-23 method when compared to industry standard.
Visually, a user would generally see lower than expected light output, or light output at an incorrect wavelength. The differences would be super-obvious when there are multiple light sources together in a room/ grouping.
What is meant by “too much light”
Too much light is used to indicate overly bright light, harsher and more prone to glare issues.
What is the LM-85-23 DCP Method?
DCP indicates Differential Continuous Pulse method. It is a method that leverages the reduced heating associated with the continuous pulse method and corrects pulse errors that exist when pulses are not square shaped, do not have fast rise time and fall time.
The DCP method is a breakthrough. What is the common error that DCP reduces?
The Differential Continuous Pulse (DCP) method effectively eliminates common continuous pulse distortions, including variations in pulse amplitude, width, and frequency, as well as dark signal and rise/fall time effects. When paired with a low-jitter pulsed SMU, the DCP method reduces measurement-related distortions by up to 100×—cutting errors from around 10% to as low as 0.1% and significantly improving measurement accuracy.
What is the takeaway for designers?
The improved testing methods in LM-85 have the potential to lift the industry, through more accurate datasheets, improved devices, and better, more efficient lighting products.
How can we use LM-85-23 standards to distinguish and good quality LED chip versus a bad quality LED chip?
The LM-85-23 methods when used result in accurate and repeatable measurements that, in theory, will allow identification of a “good quality LED chip” however there are better methods for determining flaky chips.
The recommendation is to make sure your LED suppliers are testing with LM-85-23 methods. Qualify LEDs yourself using LM-85-23 testing methods and equipment.
If we calculate our own operating point as recommended by LM-85-23, then would this data be useable when the LED must be replaced due to obsolescence?
Yes, characterizing the device(s) using a standard LM-85-23 method that includes electrical, optical, and thermal data is an excellent idea. This data would be useable when the LED/device(s) must be replaced due to obsolescense and/or product improvements occur.
I work with automotive design and one of the reasons we have isues with any variation of pulse measurement is that it takes thermal quenching away from the equation causing us to think there is more light than the LED actually does. For electrical measurements, this is a BIG step. But, does the optical section of LM-85 address that this is a better way of measuring flux while being able to touch the quenching effect too?
Yes. LM-85-23 ties all measurements to the junction temperature. LM-88-23 long-pulse test methods involve thermal quenching, matching the junction-temperature rise of older methods. LM-85-23’s short-pulse test methods are too fast to cause heating, but for those methods manufacturers can test parts at an elevated (working) temperature that matches the application condition. So, whichever LM-85-23 method is used, the published data will correspond to the actual light produced in the application.
Good to know that LEDs were even more efficient that were measured previously. Do I understand correctly that the increase in efficiency is about 4%?
The testing method does not directly make the LEDs more efficient. But the method can show that the LEDs, when operated at the datasheet temperature (e.g. 25 C, etc.) are really producing 4% more light than was measured with the older methods. Long-term we expect improved methods to help LED chip designers create better, more efficient LEDs.
For more information about LM-85-23, email info@vektrex.com
