Irradiance and Red Light/Near Infrared Bulbs
What is Near Infrared Energy?
Red light and infrared energy are parts of the electromagnetic spectrum. This is a band of energy, in which, types of energy are classified by wavelength. Light is among the types of energy in the electromagnetic spectrum. This includes light that can be seen by the naked eye and light that cannot.
Both red light and near infrared energy are types of light, although infrared energy is not visible without special equipment. Red light is energy that has wavelengths between 650 nanometers (nm) and 699 nm. Infrared energy has wavelengths between 700nm and 3000nm. Near infrared is a subset of infrared energy, having wavelengths between700nm and 1000nm.
What is Irradiance?
Irradiance is the technical term for intensity of light. Irradiance can apply to both visible light, which can be seen with the naked eye, and infrared energy, which is not perceptible to the naked eye. Whether the light/energy is visible or not, its irradiance decreases as distance from the source increases. (Think of how a lightbulb seems much brighter when you are beside it than when you are across the room from it.) For this reason, irradiance data always includes the distance from the source, such as .33M, .5M, 1M. Irradiance is measured in milliwatts per centimeter squared(mW/cm2), with larger irradiance numbers indicating more energy available at that distance.
How Are Irradiance Values Determined?
Measuring irradiance requires specialized test equipment and a controlled environment. This ensures that the distance and values are accurate, results are repeatable from bulb to bulb, and the only energy being measured is the energy produced by the bulb. Accurate and reliable irradiance values are those that were measured in a laboratory.
How Does Irradiance Affect Bulb Selection and Use?
Knowing the irradiance of a red light/near infrared bulb lets a user know how much energy the bulb emits at a given distance. This information can be used to compare two or more brands of bulbs or bulbs with different wattages. It can also be used to determine how close to get to the bulb. While safety dictates that 12 inches / .33M is the minimum distance to maintain from the bulb, irradiance data can help users determine the effects of using the bulb at a greater distance.
If you are looking for purchase a bulb for the red light and near infrared output, irradiance is a key consideration. Most companies provide irradiance data on their websites or in their product literature. If it is not among the information available online, it may be available from the manufacturer upon request.
To learn more about selecting a bulb, read our blog post How To Choose A Near Infrared Bulb