Multispectral Camera

Ricoh has developed a multispectral camera that can acquire 2D spectral information as well as chromaticity and other color information for a subject in real-time. And it’s all packaged in a unique configuration similar in size to an ordinary FA camera.

Multispectral camera features

A multispectral camera can acquire color information from a subject. Although systems using swappable color filters and prisms have been established as normal techniques for acquiring spectral information, with interchangeable color filters time to swap poses a barrier to real-time imaging. With prisms it’s to make the camera more compact.

Ricoh multispectral cameras use optical devices that can acquire spectral information in a single snapshot, together with image processor that generates an image for each set of the spectral band. As a result, spectral distribution and chromaticity for particular wavelengths can be computed in real-time. This makes it possible to precisely acquire the desired color information. In addition, color information can be acquired with a device similar in size to a conventional factory automation (FA) camera. Beyond use to detect subjects hard to distinguish from each other, our multispectral cameras can be used to inspect objects whose states change over time and to detect foreign matter. And in addition to FA, possible applications include the food, pharmaceutical, agricultural, and security industries.

Overview of technology

The new multispectral cameras developed by Ricoh incorporate the following three technologies:
- A color filter that extracts multispectral information from an object
- A microlens array that distributes the multispectral information across sensor pixels
- An image processor that generates an image for each set of spectral information from the sensor image
Spectra and chromaticity are then computed from the multispectral information obtained in this way (see Figure 1).

Figure 1: Multispectral camera configuration
Figure 1: Multispectral camera configuration

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Multispectral camera applications

Usage scenario 1: color inspection

By computing chromaticity, it becomes possible to conduct high-precision color inspections that outperform previous color photograph imaging inspections in which certain color determinations are impossible.

This technology can be used for color inspections of LCD, OLED, or other light-emitting displays. By using traditional point color checker, you need to take more than one times for checking entire screen. In contrast to this, you can evaluate color inspection of display by only 1 shot using Multispectral camera, (see Figure 2A, 2B). You can also check the light-emitting property of display from spectrum distribution chart at a time.

This technology also can be used for color inspections of molded or painted products with color limit samples (see Figure 4). So far, you need to check physical object and color limit samples by sight alternately for many of times. Using Multispectral camera, the color relations between physical object and color limit samples become clear by chromaticity diagram. So the color inspections becomes easy (see Figure 3A, 3B).

Figure: 2A
Figure: 2A

Figure: 2B
Figure: 2B

Figure: 2C
Figure: 2C

Figure 2A shows the Multispectral camera capture image, taking display which represent 6 color patches. Square shapes are the measured area in Figure 2A, and each chromaticity is plotted at chromaticity diagram (See Figure 2B). Also each spectrum distribution is shown by graph (See Figure 2C).

Figure: 3A
Figure: 3A

Figure: 3B
Figure: 3B

Figure 3A shows the example of color inspections using color limit samples. Upper 3 samples are color limit samples, and under 2 samples are physical objects, and the right one is NG sample. Figure 3B shows the inspection example, 3 glay patchs correspond to the chromaticity of 3 color limit samples , and the red patch correspond to that of NG sample.

Figure 2: Color inspection usage scenario
Figure 2: Color inspection usage scenario

Usage scenario 2: state awareness

The state of a subject (freshness, purity, disease severity) can be quantitatively evaluated in ways that were not possible with previous color photography. By taking spectral images of individual subjects, the sweetness of produce and the freshness of food can be quantitatively evaluated from information derived from minute differences in color.

Since the spectrum function of this camera is collected in the exclusive lens, it can respond to broad application and use with one camera by exchanging an exclusive lens.

Figure 3: State awareness usage scenario
Figure 3: State awareness usage scenario

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