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    • Detecting Dark Objects

    Q4X sensor detects very dark parts

    Dark objects, such as solar wafers or automotive parts, absorb a large amount of light, especially red light. Due to the low reflectivity of these targets, it can be challenging for LED- and laser-based sensors to reliably detect the presence of very dark objects—especially against a similarly dark background.   

    In spite of the challenges, there are both photoelectric and laser sensors that can reliably solve these applications. Keep reading to learn how to identify a solution for dark object detection. 

    Challenges
    Solutions and Applications
    Featured Products
    Challenges of Detecting Dark Objects
    Q4X sensor detects dark features on an equally dark background

    There are several options for detecting dark objects. A through-beam or retro-reflective photoelectric sensor is an obvious choice since the sensor can easily detect when a dark object passes between the emitter and reciever unit, or when the beam of light between the emitter and a reflector is interrupted. However, in many applications, mounting devices on both sides of the application is impractical, if not impossible.   

    In these cases, a diffuse sensor (emitter and receiver in the same housing) is required.  However, diffuse sensors rely on the target to act as a reflector, and targets must return enough light back to the sensor to verify the object's presence. If a target aborbs the majority of the light, as in the case of dark objects, the sensor may fail to reliably detect the target.  To solve these challenges, a sensor with high excess gain, or blue light instead of red, can help ensure reliable detection. 

    In many of these applications, not only must the sensor detect the dark object, but it must do so against an equally dark background (for example, detecting dark parts on a dark auto body panel). The lack of contrast between target and background is also challenging for many photoelectric sensors to detect.  For these applications, a distance-based laser sensor is a must.  Keep reading to learn why. 

    3 Solutions to Reliably Detect Dark Objects
    The Q5X sensor detects black components on a black seat
    High Excess Gain

    Excess gain is an important metric for any application, but it is especially important when detecting dark objects. Excess gain is a measure of the minumum light energy needed for reliable sensor operation. A high excess gain helps the sensor overcome a weaker signal reflected by a dark object.  

    The amount of excess gain you need, over and above what you might need for a "typical" target, will depend on how dark your target is as well as the environment of your application.  Pristine environments with little dust will require less excess gain than a dirty environment with debris that can cloud the sensor lens and further reduce signal strength. 

    Fortunately, determining the amount of gain you need doesn't have to be a manual process. Smart sensors can recognize if very little light is returning to the receiver and automatically adjust exposure settings for additional gain and a stronger signal.

    Distance-Based Detection

    Sensors that rely solely on contrast will struggle to detect very dark objects against a similarly dark background; however, these applications are common, especially in the automotive industry.  For example, in the application pictured to the right, verifying that foam and other components are present on automotive door panels is extremely important.  If any part is missing, the quality of the final door assembly is adversely affected. 

    Since door panels are often dark colors such as black or gray, and the foam used to eliminate rattles and provide stiffness is generally black, it can be difficult for standard sensors to differentiate between foam presence and absence due to poor contrast.  A laser measurement sensor can reliably detect these parts by detecting changes in distance instead of color. 

    The Q4X sensor detects dark parts on a dark background in an automotive application
    Solar cells and other very dark objects absorb light and are difficult to detect
    Blue LED Light

    Some targets are designed specifically to absorb red light. For example, solar wafers are designed to absorb as much sunlight as possible and are covered in anti-reflective coating. This makes solar wafers very difficult for traditional photoelectric sensors to detect. 

    In these applications, a photoelectric sensor with a blue LED light can be a cost-effective solution. Blue light is not absorbed by dark objects to the same extent as red light. Since more light is remitted back to the sensor, a sensor with blue light will be able to detect extremely dark objects with greater reliability.

    Featured Products
    Q4X Sensor
    Q4X Series

    Laser Distance Sensor, 25-610 mm

    Sensores de distância a laser versáteis e robustos que oferecem alto desempenho e são capazes de detectar mudanças de distância submilimétricas.

    • Modelos discretos, analógicos (0 a 10 V ou 4 a 20 mA), para objetos transparentes e com IO-link disponíveis
    • Alcance do sensor a partir de 25 mm até 610 mm
    • Detecta uma grande variedade de cores, materiais e superfícies de alvo com base na distância
    • O modo dual TEACH (intensidade + distância) é ideal para aplicações de verificação de erros e permite a detecção de objetos transparentes sem a necessidade de retrorrefletores
    • Corpo robusto de aço inoxidável de grau FDA com classificação IP69K
    Q5X Series

    Laser Distance Sensor, 9.5 cm - 2 m Range

    O laser com supressão de fundo do Q5X é um sensor um poderoso para solução de problemas em um dispositivo econômico com corpo retangular padrão da indústria.

    • Alcance de 9,5 cm (4 polegadas) a 2 m (6 pés e 6 polegadas)
    • Ganho excepcionalmente alto permite que o sensor detecte com segurança os objetos mais escuros (<_6 alvos="alvos" pretos="pretos" refletivos="refletivos" li="li">
    • Detecta com segurança alvos pretos contra um fundo preto, alvos pretos contra um fundo de metal brilhante, objetos claros e reflexivos, embalagens multicoloridas e alvos de todas as cores
    • O modo dual mede a distância e a intensidade da luz para resolver as aplicações mais desafiadoras
    Q5X sensor
    VS8 Sensor
    VS8 Series

    Photoelectric Sensor with Blue LED

    • Sensor em miniatura para instalação nos espaços mais pequenos
    • Os modelos com laser vermelho fornecem um spot de laser brilhante e preciso para uma ótima detecção de peças pequenas.
    • Os modelos com um LED azul detectam alvos desafiadores, incluindo objetos escuros, reflexivos e transparentes, sem exigir um refletor
    • Alta frequência de comutação para detecção, mesmo nos processos mais rápidos
    • A operação simples utilizando botão eletrônico ou entrada remota proporciona detecção confiável e precisa
    • Laser vermelho, LED vermelho e LED azul disponíveis para ajustar o feixe de detecção com a aplicação
    • Encapsulamento de plástico robusto, reforçado com fibra de vidro
    • Saída PNP ou NPN, dependendo do modelo
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