Surface inspection and gloss measurement

Single-channel inline spray jet monitoring in the Ex area using the reflected light method
When extremely small amounts of spray need to be detected, a reflected light spray jet system is the obvious choice. The SPECTRO-T-1-FIO-RL spray jet control system in conjunction with the ABL-V-ARRA-KL-M18-XL-A3.0 fiber optic frontend has a hardware integrator that enables even the smallest amounts of spray to be reliably detected. By means of the fiber optic frontend, the system is also Ex area compatible. The blow air attachment unit integrated in the frontend prevents droplets being deposited on the optics. The working distance of the measuring sensor to the spray jet is 50mm.

Single-channel inline spray jet monitoring in reflected light mode
With the help of the SPECTRO T 1 Scope V1.0 Windows® PC software, the SI-JET3-FIO-RL spray jet control system can be optimally adapted to the respective application. The digital outputs provide information on the correct spray quantity; by means of a PROFINET adapter there is also access to the raw data of the measuring system.

Single-channel inline spray jet control systems using the transmitted light method
If the system requires a larger distance to be maintained between the sensor system and the spray jet to be measured, there is no alternative but to use a transmitted light system. With the help of the SPECTRO-1-CONLAS electronic control unit and the frontends of the A-LAS-N series, laser spots from 0.3mm diameter up to 16mm x 2mm are available. The laser light spot is directed onto the spray cone in such a way that it is completely covered by the spray jet. The closer the laser light curtain is to the outlet opening of the nozzle, the greater the influence on the measurement signal.

Single-channel inline transmitted light systems for monitoring individual droplets
Both in the pharmaceutical and in the electrical industry for selective soldering, liquids are applied to a carrier material in packets (in form of droplets), for example using a piezo nozzle or an electromagnetic nozzle. The task of the spray jet control system is to monitor the amount of spray applied to the carrier material. Firstly, the droplets are counted and secondly, the size of the individual droplets (width and length) is determined using a laser light curtain.
Extensive PC software is also available for the parameterization with this measuring system. The included SCOPE function can be used to record an image of the droplet sequence, for example. The measurement system used for this was an A-LAS-CON1 electronic control unit in conjunction with an A-LAS-F12 laser fork light barrier.

Single-channel inline spray jet monitoring in the Ex area using the transmitted light method
For the Ex area, a fiber optic version is available for spray jet control in transmitted light mode. A so-called transmitted light fiber optics, for example a D-S-Q3-(18x0.3)-1200-67°, is connected to an electronic control unit of the type SPECTRO-1-FIO-JC. In principle, fiber optic cross-sections with a diameter of 0.6mm to 3.0mm or a rectangular cross-section of 3.0mm x 0.5mm to 48mm x 0.15mm can be used. Attachment optics are available for the vast majority of fiber optics, which can be used to increase the distance between the transmitting and receiving optical fibers.
Relatively extended spray cones can also be monitored with a corresponding light curtain provided by cross-section transformer, for example a Q3 (18mm x 0.3mm). When the spray jet is activated, part of the light in the light curtain is absorbed or scattered, reducing the received signal accordingly. Both digital signals (0V/+24V) and an analog signal are available at the output of the electronics, which reflects the curve of the signal attenuation triggered by the spray jet..

Three-channel inline spray jet monitoring systems in transmitted light mode
For additional control of the spray cone with regard to the geometry, for example the spray cone opening angle or the deviation from the ideal symmetry axis, at least three points in the spray cone must generally be monitored. The compact laser spray control system SI-JET-CONLAS3-T-d1.5 (transmitter unit) + SI-JET-CONLAS3-R (receiver unit and evaluation electronics) has three collimated laser light beams that can detect spray cones even with a small opening angle in the tightest of spaces. The SCOPE function in the PC software can be used to analyze the signal curves of the three channels due to the influence of the spray jet. This allows conclusions to be drawn about the spray jet intensity as well as the spray jet geometry.

Three-channel inline spray jet monitoring in the Ex area using the transmitted light method
A fiber optic arrangement is provided to implement the three-channel spray jet control in the Ex area. Red light is fed in on the transmitter side via three fiber optics strands. Three fiber optics strands are also available on the receiver side, each of which is directed to an optoelectronic receiver. Again, the attachment optics are used to increase the transmitter/receiver distance, with which the light beams can be collimated or focused accordingly.
If the attachment optics are selected appropriately, several spray cones can be detected simultaneously. The signals received provide information about the signal attenuation in total. However, if one of the spray jets deviates from the normal state, this can still be reliably detected by the electronic control unit.
SI-JET3-FIO-RL + for example:
• R3-M-A1.1-(1.5)-3000-67°-3X +
   KL-M18-A1.1 + ABL-M18-5-B
• R3-M-A2.0-(2.5)-3000-67°-3X +
   KL-M18-A2.0 + ABL-M18-5-B

Inline spray jet profile sensors using the transmitted light method
If a three-channel system is not sufficient for analyzing the spray jet, a complete section through the spray cone can be laid and evaluated using a laser line through-beam sensor system. The collimated laser light curtain directed onto the spray jet hits a line detector element on the receiver side after passing the spray cone. The video signal provided by the line detector provides information about the respective local attenuation of the laser light by the spray cone.
With the help of special algorithms, individual spray jets can be localized in the spray field and their peak height and exact position in relation to the spray jet profile can be determined. If a simple spray cone is present, its symmetry and spray jet intensity can also be precisely determined.
Sensor type for example:
L-LAS-TB-100-T-AL-SC +
L-LAS-TB-100-R-AL-SC
 

Inline measurement of the color of a surface using the 45°/0° method
To make the actual color more apparent, the direct reflection must be suppressed as much as possible. On the detector side, mainly diffusely reflected transmitter light is incident. Gloss effects are avoided as far as possible on the receiver side. This significantly reduces the difference between glossy and matt surfaces. This color measurement method is mainly used for flat surfaces (flat within the measuring spot). Moreover, homogeneous surfaces should be measured. For the measurement of structured surfaces, this measuring principle is less suitable.
SPECTRO-3-28-45°/0°-MSM-ANA-DL

Inline measurement of the color of a surface using the Diffuse/0° method
This measuring method is particularly suitable for structured surfaces, as surface differences are largely compensated for by diffuse light. Yet this measuring method is also extremely suitable for wire-shaped objects (e.g. metal wires, plastic wires and textile threads). Since the measurement is done inline here, an integrating sphere cannot be used as a diffuse light source. Instead, a combination of volumetric diffusers and a Sunlight-LED cluster is used. This ensures that the entire half-space is illuminated almost homogeneously.
SPECTRO-3-20-DIF-MSM-ANA-DL

Spot inline color measurement
iber optic frontends are suitable for inline color measurement of small surface sections. Depending on the application, either a combination of transmitter and receiver fiber optics in a V-shaped arrangement or a reflected light fiber optics in which the transmitter and receiver branches are equally present can be selected. Corresponding cross-section converters enable both circular and rectangular light spots.

Inline color measurement with optical fibers
A color sensor system with a fiber optics interface is used to measure the color of pearlescent effect color marks, for example. The light is projected onto the color marks by means of a reflectied light optical fiber with attachment optics and a part of the diffuse reflected light is directed backwards to the color-sensitive detector element.
SPECTRO-3-FIO-MSM-ANA-DL +
R-S-R2.1-(6x1)-1200-67°+ KL-8-R2.1

Inline gloss measurement
When assessing the quality of a surface, gloss is used in addition to color. Gloss is the direct reflection on the object surface. It is important to ensure that the surface within the light spot is flat and homogeneous. Depending on the degree of gloss, measurements are taken at different angles to the normal:
• 20°(high-gloss surface)
• 60°(glossy to matt surface)
• 85°(matt surface with low gloss)
• 45°(matt to glossy paper surface, TAPPI standard)
• 75°(matt paper surface, TAPPI standard)

For inline gloss measurement, it is necessary to ensure that the measuring distance, i.e. the distance between the gloss measurement system and the surface to be measured, is constant and corresponds to the specified measuring distance. In addition to the stated measuring angles, different apertures are available for each measuring angle. This allows light spot sizes from 1mm in diameter to be realized, which means that correspondingly small objects can be measured.
GLOSS-20-20°
GLOSS-20-45°
GLOSS-20-75°
GLOSS-15-60°
GLOSS-5-85°

Inline haze control
In difference to gloss measurement, where direct reflection is decisive, haze control is concerned with the diffusely scattered portion of directed light on the surface to be measured. If, for example, a line grid is projected onto the surface to be measured, a so-called haze effect appears due to the diffuse reflection, which shows the image on the surface slightly blurry. The haze effect is measured using imaging optics including a line sensor integrated into the measuring system.If a haze-free surface is present, the image on the line appears with high contrast, i.e. light-dark transitions inthe line grid show a high amplitude on the video signal. However, if the surface is slightly diffuse, the contrastis reduced and the amplitude on the video signal decreases accordingly.
GLAST-85-30°/30°-DIF-0.5/0.5
GLAST-85-30°/30°-DIF-1.0/1.0
GLAST-85-30°/30°-DIF-2.0/2.0

Inline fluorescence measurement
Fluorescent surfaces are characterized by the fact that they respond to the exposure to light (primary light) of a certain wavelength by emitting secondary light. Once the primary emission has ceased, the secondary emission also ends abruptly. Thus, there is no afterglow. Typical excitation wavelengths are in the so-called UVA range (typically 365nm), but certain phosphors can also be excited in the blue or red wavelength range. Secondary emission thereby occurs in the longer-wave visible range or in the near infrared range. A color sensor system equipped with UVA LEDs is used for inline fluorescence measurement. By using optical long-pass filters, secondary light as from the blue wavelength range can hit the color detector.
SPECTRO-3-30-UV/BL-MSM-ANA

Spot inline fluorescence measurement
For measuring very small fluorescent surfaces, sensors with attachment optics that are connected to the measuring system via an optical fiber are most suitable. This allows light spot sizes from approx. 1mm in diameter or cross-sections of 2mm x 0.3mm to be realized. The visible wavelength range is evaluated here as well. The color of the secondary emission can also be determined using a three-range detector (L*a*b*).
SPECTRO-3-FIO-UV/BL-MSM-ANA +
R-S-A3.0-(3.0)-1200-22°-UV + KL-9-A3.0

Inline phosphorescence measurement

In contrast to fluorescent surfaces, an afterglow can be detected on phosphorescent surfaces, the intensity of which decays exponentially with a marker-specific time constant (TAU) after the end of the primary emission. Depending on the marker used, suitable excitation wavelengths extend from the UVA range (e.g. 365nm) through the visible wavelength range (e.g. blue or red) to the near infrared range. The primary emissions are either in the visible wavelength range or in the near infrared range.
The marker-specific, exponential decay curve can be described using two parameters: The initial intensity INT and the time constant TAU.
Depending on the marker dosage, the excitation wavelength, the secondary emission and the time constant TAU can be specifically influenced. This allows markers to be customized for the respective application.
LUMI-TAU-INLINE-SL-IR/IR

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