Using a 4K Digital Microscope in RGB Measurements

In a human eye, the retina separates the light reflected from a viewed object (visible light with a wavelength of 400 to 700 nm) into red (R), green (G), and blue (B) and transmits this stimulus to the brain where it is judged as color. In the same manner, a colorimeter measures these three types of light stimuli, quantifying them as tristimulus values: X, Y, and Z.
This measurement method is referred to as the stimulus value direct reading type. This type of colorimeter is relatively inexpensive, compact, and easy to handle, so it is widely used in color inspections and similar operations at manufacturing sites. On the other hand, the numeric values vary depending on the light source, so this device is not suited to the advanced analyses performed with spectrophotometers, explained next.

A spectrophotometer measures reflectance by using a sensor with multiple receivers to disperse into multiple wavelengths the light emitted from the light source and reflected from the target. In addition to calculating tristimulus values X, Y, and Z, this device is also capable of color (wavelength) analysis via spectral reflectance with a graph or something similar.
Differing from the stimulus value direct reading type colorimeter, a spectrophotometer can use the data of various light sources to investigate differences in viewing methods attributable to the light source (color rendering), the phenomenon that occurs when two colors appear to match under one lighting condition (metamerism), and differences in target surface conditions. Although they are more expensive than colorimeters, spectrophotometers enable more advanced color analysis and are therefore mainly used in research and development.

This is the first color system established by CIE. This system expresses color as a mixing ratio (an additive mixture of colors) of the three primary colors (also known as tristimulus, reference color stimuli, and color stimuli) R (red), G (green), and B (blue) that actually exist. The spectrum of the three primary colors is R = 700 nm, G= 546.1 nm, and B = 453.8 nm. However, there are colors that cannot be expressed as an additive mixture of colors in the RGB color system. For example, bright cyan cannot be created with any combination of the three primary colors.

The XYZ color system is widely used in various industrial fields. Using X, Y, and Z to express colors, this system was designed to mathematically avoid the problem of the RGB color system not being able to accurately reproduce monochromatic light of the color gamut.
R, G, and B are the spectrum that actually exists and are called true colors. On the other hand, X, Y, and Z in this color system are the colors of mathematically converted light. Because some of these colors do not actually exist, X, Y, and Z are called false colors. Instead of systemizing colors perceived by people, using false colors with the purpose of displaying colors in a quantified manner makes it possible to express all colors as X, Y, and Z values.

The color difference (ΔE) can be found by using the values obtained from these three axes in the color difference formula. Colorimeters, widely used in quality inspections, also calculate color differences with this method.
Setting this ΔE as a control index is useful in improving quality by enabling quantification in color difference management and comparative judgment against reference colors in industrial fields.

Tips:What is sRGB?
This is an international standard established by the International Electrotechnical Commission (IEC) in 1999. A wide range of products including monitors, printers, and digital cameras conform to this standard. It has excellent versatility and is highly compatible with monitors and other color modes. Because it makes advanced color management easy, it is also used in fields such as the capturing, editing, and printing of images.

The VHX Series 4K digital microscope is equipped with an advanced optical system and a 4K CMOS image sensor that combines a large depth of field with high resolution imaging capabilities.
The VHX Series can easily and quickly acquire clear, magnified images of films, which have various surface conditions. For example, even if the surface is rough, the large depth of field allows for automatic focusing throughout the entire field of view. It is difficult to determine the lighting conditions for glossy films, but the Multi-lighting function, which automatically acquires multiple images under omnidirectional lighting at the press of a button, makes this work easy.
The high-resolution 4K images acquired with these simple operations can be used in highly accurate RGB measurements and color difference evaluations. Additionally, when a past image is selected, the conditions used to capture that image are fully reproduced, enabling fast RGB measurements and quantitative color difference evaluations under the same conditions even for a different sample of the same type of product.

The VHX Series 4K digital microscope can capture clear 4K images and perform highly accurate RGB measurements. These features make it useful in identifying different types of films, which are difficult to determine visually.
In addition to accurate differences between RGB measured values, the VHX Series can clearly capture subtle texture differences—which are normally difficult to check for due to their low contrast—arising from differences in materials and processing.
Furthermore, it is easy to identify film product types by comparing their images side-by-side on a large, 27-inch color LCD monitor specially designed to display images faithful to the target.
This advanced core performance not only simplifies the operations of measuring film RGB values, investigating color differences, and differentiating between product types, but also the advanced observation and analysis of microscopic flaws and defects on film surfaces.

Examples of conversions between XYZ values and RGB values conforming to sRGB are shown in the following table. W.P. is an abbreviation of white point.

Excel can be installed directly on the VHX Series 4K digital microscope, making it possible to easily convert measured values and automatically create reports with this one device.