Visual inspection - lighting for manual control

In addition to machine vision solutions, employees are also required to visually inspect and evaluate test parts. For this area of manual quality control, our LED lights are specifically designed to meet the requirements of backlight or top-light inspection.

Of course, the luminaires can also be used as workstation and assembly luminaires. They provide a more pleasant light than conventional task lights and create a more uniform light in the work area.

Transmitted light

  • For transillumination and edge examination of objects
  • Rugged aluminum case in “neutral gray” color
  • No raised edge, matte finish
  • Standard light fittings D30, D40, D50 and D65
  • No IR or UV component in the light spectrum
  • With manual or digital controller

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Light cabins

  • Light booth for testing in a controlled environment
  • Glare-free reflector system for uniform illumination
  • Standard light fittings D30, D40, D50 and D65
  • No IR or UV component in the light spectrum
  • In 1 or 2 standard light colors, switchable and dimmable

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Reflected light

  • Normal light inspection lights for reflected lighting examination
  • Work and assembly light
  • Glare-free reflector system for uniform illumination
  • Standard light fittings D30, D40, D50 and D65
  • No IR or UV component in the light spectrum
  • In 1 or 2 standard light colors, switchable and dimmable

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AI-Systems

  • LED lighting for work and assembly station systems with integrated AI for real-time detection of irregularities
  • Individual adaptation to the inspection task
  • Completion of the assembly station with signal indicators for direct communication with the worker

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It is crucial to differentiate between whether the test parts are inspected and classified by a human or by a camera. The following factors play an even more significant role here than in industrial image processing:

  • the light intensity
  • the light color
  • the quality of light
  • the arrangement of the lights
  • the possibility of adapting to the respective person

As professionals with many years of experience and in-house development, we can cater to all special requirements. planistar has a product range that is specially adapted to the needs of visual inspection. We also offer individual lights for your visual inspection.

Why by a human and not with the help of image processing?

Visual inspection, often abbreviated to VT (= visual testing), is an optical or visual non-destructive material test.

Industrial image processing is becoming more and more common in our industry. However, the camera only sees a few pixels, which are evaluated by software according to fixed criteria.

The human eye, on the other hand, is a very precise measuring instrument. It can perceive many things and evaluate and assess them according to specifications and experience. This human component cannot be replaced by software.

In sensitive markets like the medical industry, an inspector is used as a second inspection step alongside image processing to assess products from every angle.

Visual inspection using top- or backlighting?

The fundamental question to be answered is whether the test should be performed in reflected or transmitted light. The specimen and its test characteristics are important in selecting the appropriate lighting.

Possible examination characteristics can be:

  • Presence
  • Completeness
  • Defects
  • Position
  • Surface quality

For this purpose, a description should be available in a specification sheet in which all features and work steps of the visual inspection (non-destructive testing) are listed.

It is also important to take the situation of the test environment into account:

  • Extraneous light, environmental light
  • Timing requirements for the audit
  • Positioning before, during and after the test

To achieve the ideal result, we take these and other factors into consideration during the planning and design process.

Direct or indirect visual inspection

In a direct visual inspection, the area to be inspected is viewed by an inspector. The area of the sample to be inspected is inspected directly with the naked eye. Observation, analysis, and evaluation are performed by one person.

Indirect visual inspection does not use the eye to directly inspect. A camera captures the inspection image and displays it on a monitor. Indirect visual inspection allows the inspection image to be further processed. For example, the image can be enlarged, details can be highlighted for analysis, or the image can be saved for documentation purposes. By transferring the image to a monitor, more than one person can assess the image.

It's all about the right lighting

The human factor is a subjective influence that depends on the visual acuity, experience and accuracy of the operator. With our experience in lighting and our specialized products, we can positively counteract factors such as fatigue, contrast, color perception and viewing conditions. Choosing the right lighting is critical to achieving a reproducible and meaningful assessment by the inspector.

Differentiation between different types of standard light

D30 (3000K) is similar to a bulb light and a pleasant warm tone. Can be an advantage in fault detection with various materials.

D40 (4000K) is rather rare, but is also used in certain fault detection applications.

D50 (5000K) is often used in the graphic arts industry and describes the test conditions for colors. This is described in DIN ISO 3664, among others.

D65 (6500K) is used for the visual comparison of colored materials.This is described in DIN EN ISO 3668, among others.

We used these standards as the basis for developing our Color Control Series.

The main specifications of the standards include:

  • The light must correspond to daylight with a color temperature of 3,000, 4,000, 5,000 or 6,500 K
  • The light source must have a color rendering index of Ra > 90 (with planistar even approx. >Ri97)
  • The surroundings must have a neutral grey, matt color
  • For top light, the illuminance must be approx. 2,000 to max. 4,000 lx.
  • Ideally, the colors to be tested are evaluated under different lighting conditions.

Ideally, the sample is viewed under both light colors. D65 simulates a gray, overcast sky at noon, while D50 simulates evening light because it contains less blue.

Not all whites are the same

In order to examine and evaluate colors, the white spectrum of the lighting is essential. This is because only those colors that are emitted by the spectrum of the luminaire can be reflected on the test object. If the spectrum is insufficient, the colors will be distorted.

For this reason, it is important that the spectrum of the light source be as close as possible to that of sunlight (Ra = 100). It should be noted that the color of sunlight also changes depending on the season and time of day.

The most neutral white is seen at about 5300 K, which is the standard D50 light color.

 

Daylight in the evening (5000 K) and daylight at noon (6500 K) are different and make colors look very different. Here is an example:

Any questions?

Our team will be at your disposal for any questions you may have. We will process your request as soon as possible.

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Friday 8.00 am - 01.00 pm
   

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