The DOI (Distinctness of Image) Difference for Floors

This article was originally published in Facilities Management Magazine.

We've heard it many times: One of the first things people notice upon entering a facility is the floor, and if those floors aren't shiny and clean, it reflects poorly on the facility. In addition to potential health risks, dirty floors can give visitors a negative image of a business or facility's overall operations while clean, well maintained floors create a positive first impression. One way building owners and operators can improve customer perception of their facilities is to ensure their floors have a high distinctness of image (DOI).

What is DOI?

DOI is best defined as the measure of how crisply and sharply an image is reflected from a surface, indicating the clarity of a reflection seen in the floor. DOI is gaining popularity and quickly becoming the new measure of floor restoration, protection, and maintenance quality. It should not be confused with other measures like gloss, haze, and RSpec measurement.

Gloss. The most popular term used to describe the appearance of a floor's surface is gloss. Gloss refers to shine or light reflection and causes surfaces to have a polished or lustrous, metallic appearance. Many factors can affect gloss, including the maintenance materials used, condition of the flooring, and frequency of polishing. For customers, gloss has been one of the most important aspects of visual perception.

To measure a floor's gloss, a meter projects a beam of light onto the floor and measures the amount of light reflected back in a narrow angle range centered at an equal but opposite angle. The amount of light measured in this angle range is used to calculate gloss. However, the clarity of a reflected image is dependent on the spread of light within the measured angle range. If light is predominantly at the center of the range, the image will be crisp and clear. Light spread more evenly across the entire angle range will result in a blurry image. Thus, the amount of reflected light measured on two different floors might be the same but have a much different distribution across the measurement. So two floors with an equal gloss could have very different appearances.

This is why traditional gloss measurements alone don't always equate to a favorable customer perception.

Haze. This is the milky halo or "bloom" on a floor adjacent to the reflected image. If you place a high light source on a surface and the reflection image blooms and creates a blurry halo, the surface is considered high haze. Haze is an important measure for highly polished surfaces. Higher haze values indicate lower quality and can be caused by dirt or oil contamination creating a rough surface. If the surface or coating is not completely smooth, the reflection of light or image is scattered, broadening the specular gloss.

Floor maintenance professionals strive for a low haze value, which is seen to have a deep reflection and high-reflected contrast. Hence, haze is a common measurement of maintenance quality. Yet while haze affects the clarity and reflection of surfaces, it is only one aspect of surface quality and doesn't measure the overall floor's appearance.

RSpec. Peak specular reflectance (RSpec) is the peak gloss value of a surface. It is the gloss measured only at the specular angle and is the peak gloss reading. Specular gloss is the reflection of an object on a perfectly smooth surface, such as a mirror, in which the reflection is sharp and clear. Of course, if a surface is not perfectly smooth, it scatters the reflection of the light beam and broadens specular gloss.

RSpec is limited in measuring the true appearance of a surface because it only represents the peak gloss value. It does not take into account the distribution of light around the specular angle.

DOI takes this distribution into account, and therefore is an accurate measure of the clarity of the reflected image.

Read the full article here to learn how to measure DOI and how to achieve high DOI.