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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

    Versatile, rugged laser distance sensors offering superior performance and capable of detecting sub-millimeter changes in distance.

    • Discrete, analog (0 to 10 V or 4 to 20 mA), clear object, and IO-Link models available
    • Reliable sensing range from as close as 25 mm and as far as 610 mm
    • Detects across a variety of target colors, materials and surfaces based on distance
    • Dual teach mode (intensity + distance) is ideal for error-proofing applications and enables clear object detection with no retro-reflector required
    • Robust housing rated to IP69K with FDA-grade stainless steel
    Q5X Series

    Laser Distance Sensor, 9.5 cm - 2 m Range

    Q5X 배경 억제 레이저는 산업 표준 직사각형 하우징으로 둘러싸인 경제적인 장치에 장착된 여러 가지 문제를 해결하는 강력한 센서입니다.

    • 범위: 9.5 cm(4 인치)~2 m(6피트 6인치)
    • 과잉이득이 예외적으로 높은 경우 이 센서는 가장 어두운 물체(반사율이 6% 미만인 검은색 물체)를 확실하게 감지할 수 있습니다.
    • 검은색 배경을 뒤로 한 검은색 표적, 반짝이는 금속 배경을 뒤로 한 검은색 표적, 투명한 반사 물체, 다양한 색상의 포장 및 모든 색상의 표적을 감지할 수 있습니다.
    • 이중 티칭 모드에서는 거리와 광도를 둘 다 측정해 가장 까다로운 응용 분야의 문제를 해결합니다.
    Q5X sensor
    VS8 Sensor
    VS8 Series

    Photoelectric Sensor with Blue LED

    • 가장 작은 공간에 설치 가능한 소형 센서
    • 소형 부품을 잘 감지할 수 있도록 밝고 정확한 레이저 광선 스팟을 제공하는 적색 레이저 모델
    • 청색 LED 장착 모델의 경우 반사 장치 없이도 어두운 물체, 반사 물체 및 투명한 물체를 포함해 까다로운 대상체를 안정적으로 감지
    • 가장 빠른 공정에서도 감지가 가능하도록 높은 스위칭 주파수 제공
    • 전자식 푸시 버튼 또는 원격 입력 기능을 사용한 사용자 친화적인 조작을 통해 신뢰할 수 있고 정확한 감지 가능
    • 응용 분야에 감지 광선을 맞출 수 있도록 적색 레이저, 적색 LED 또는 청색 LED 유형으로 제공
    • 견고한 강화 유리 섬유 플라스틱 하우징
    • 모델에 따라 PNP 또는 NPN 출력
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