“In a reflective color sensor system, the detector and illuminator are usually installed together in a module. When the module is placed near the target, the light from the light source will fall on the target surface and be reflected to the detector. The color of the light reflected from the surface is a function of the color of the surface. For example, white light focused on a red surface is reflected as red. The reflected red light is incident on the color sensor to generate R, G, and B output voltages.
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Reflective color sensing using Avago Technologies’ RGB color sensor
Abstract—Reflective color sensing is usually achieved by photodiodes with multiple light sources or photodiodes coated with color filters containing a single light source. This article introduces the concept of reflective color sensing using RGB color sensors. First, discuss the theory of reflective color sensing and its basic elements. Then it discusses hardware design considerations and sensor output interpretation.
Reflection sensing theory in reflection sensing
There are three important elements: detector, target and light source. The detector is a device that captures the light reflected from an object. The goal is to measure color objects, such as colored paper or paint. Usually non-emissive, it reflects and absorbs different amounts of light of different wavelengths. Illumination is a light source whose spectrum covers the wavelengths of visible light, such as sunlight.
In a reflective color sensor system, the detector and illuminator are usually installed together in a module. When the module is placed near the target, the light from the light source will fall on the target surface and be reflected to the detector. The color of the light reflected from the surface is a function of the surface color. For example, white light focused on a red surface is reflected as red. The reflected red light is incident on the color sensor to generate R, G, and B output voltages. By interpreting the three voltages, the color can be determined. Since the three output voltages increase linearly with the intensity of the reflected light, the color sensor can also measure the reflectivity of surfaces or objects.
Non-overlapping spectral response
Reflective sensor system hardware design considerations Reflective sensor system
Contains three basic elements: RGB color sensors, external light sources such as LEDs, and non-luminous objects.
1) Select the detector
Which detector is suitable for reflective sensing? A suitable detector needs to have good sensitivity and spectral coverage. In reflective sensing, the light captured by the detector is reflected back from the object being measured. Therefore, the intensity of the reflected light is lower than the intensity of the direct light source.
The spectral responses of the individual red, green, and blue channels should overlap to ensure that all wavelength information is captured. Figure 1 and Figure 2 below show the overlapping and non-overlapping spectral responses, respectively. Figure 3 shows the arbitrary spectrum of the signal reflected from the blue surface.
Reflective color sensing using Avago Technologies’ RGB color sensor
Abstract—Reflective color sensing is usually achieved by photodiodes with multiple light sources or photodiodes coated with color filters containing a single light source. This article introduces the concept of reflective color sensing using RGB color sensors. First, discuss the theory of reflective color sensing and its basic elements. Then it discusses hardware design considerations and sensor output interpretation.
Reflection sensing theory in reflection sensing
There are three important elements: detector, target and light source. The detector is a device that captures the light reflected from an object. The goal is to measure color objects, such as colored paper or paint. Usually non-emissive, it reflects and absorbs different amounts of light of different wavelengths. Illumination is a light source whose spectrum covers the wavelengths of visible light, such as sunlight.
In a reflective color sensor system, the detector and illuminator are usually installed together in a module. When the module is placed near the target, the light from the light source will fall on the target surface and be reflected to the detector. The color of the light reflected from the surface is a function of the color of the surface. For example, white light focused on a red surface is reflected as red. The reflected red light is incident on the color sensor to generate R, G, and B output voltages. By interpreting the three voltages, the color can be determined. Since the three output voltages increase linearly with the intensity of the reflected light, the color sensor can also measure the reflectivity of surfaces or objects.
Non-overlapping spectral response
Reflective sensor system hardware design considerations Reflective sensor system
Contains three basic elements: RGB color sensors, external light sources such as LEDs, and non-luminous objects.
1) Select the detector
Which detector is suitable for reflective sensing? A suitable detector needs to have good sensitivity and spectral coverage. In reflective sensing, the light captured by the detector is reflected back from the object being measured. Therefore, the intensity of the reflected light is lower than the intensity of the direct light source.
The spectral responses of the individual red, green, and blue channels should overlap to ensure that all wavelength information is captured. Figure 1 and Figure 2 below show the overlapping and non-overlapping spectral responses, respectively. Figure 3 shows the arbitrary spectrum of the signal reflected from the blue surface.
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