The functionality of a manufactured product or its perceived quality is often linked to its transparency. Matt shipping labels require good contact clarity which allows QR codes to be read on high-speed conveyor lines, while recycled salad trays are preferred with low haze so the consumer can appreciate the vibrant colours of packed vegetables.
To optimise and improve transparency, a constant inline measurement of key parameters is more efficient than occasional offline measurements. Instant feedback from an sensors allows fine tuning of a process, ultimately achieving a better-quality product, with measured consistency throughout every production run.
Materials with high optical quality have low visual impact on objects viewed through them. The material itself is visually unobtrusive and almost invisible to the observer.
A hazy material causes colour seen through the material to appear washed out or faded. The severity of this loss of contrast is often related to the size of the gap between the object and the material.
A material which blurs the view of objects has low sharpness- this effect can be directional causing a visible pattern to be seen in the material.
Materials with poor optical qualities are visually intrusive and can be described as milky or opalescent. Patterns and texture which may be visible in the material drastically blur viewed objects.
The Rhopoint ID measurement technology (patent pending) was jointly developed with Eidgenössische Technische Hochschule (ETH) Zürich.
The Rhopoint ID-Inline is a camera-based system which fully quantifies product transparency with parameters that are highly correlated to human perception.
There are two versions of the Rhopoint ID-Inline. A short focal length version which has a separation distance of 45mm between the camera and graticule, or the long focal distance version which has a separation distance of 170mm.
The Rhopoint ID-Inline can be used for non-contact measurement of any sheeted or planar material - including plastic films, or glass. The Rhopoint ID-Inline can also be used for non-contact inline measurement of glass or plastic tubes.
This version is most suitable for production processes where the large focal distance is more suited to the customer production line.
Either version can be incorporated into an inspection station for 3D parts or large sheets of plastic or glass.
Standard or extended clearance models are available to encompass a wide variety of parts and installation configurations.
Flexible software allows single or multiple ID sensors to be combined with compatible measurement devices and tabulated in the Rhopoint ID laboratory software.
Up to 10 Rhopoint ID-Inline units can be connected simultaneously to a SAP/process control package using the Rhopoint ID TCP/IP connection client. This solution allows independent remote control of each instrument, measurement data is exchanged using Rhopoint TCP/IP protocol.
The TCP/IP client is designed to facilitate fast efficient operation of multiple devices by the SAP/process control package. Up to 10 measurements per second are possible from each sensor. The client can be hosted on a local PC or server.
Haze: quantifies the loss of contrast for objects viewed through a material.
When a material has haze, it changes the appearance of both the material and any objects viewed through it. This can lead to a reduction in perceived quality.
Measure Haze with the Rhopoint ID to ensure visibility of products are at their best and can be seen properly by the customer.
| Perception | Description |
|---|---|
| No Haze |
|
| Perfect Sharpness |
|
H = 0%
S = 100%
T = 100%
| Perception | Description |
|---|---|
| Medium Haze |
|
| High Sharpness |
|
H = 10.4%
S = 92.32%
T = 92.3%
| Perception | Description |
|---|---|
| High Haze |
|
| Low Sharpness |
|
H = 30%
S = 78.8%
T = 89.7%
Haze can be affected by factors such as the choice of resin, the moulding process and any surface textures. Haze can be caused by:
For example, a plastic with an incorrect melt viscosity for a particular process.
Cooling a plastic material too quickly can introduce micro textures onto the surface of the film or structures in the bulk which reduce optical quality.
Wear and tear in moulds, chill rollers and slip dies can induce visible surface defects in the material.
Sharpness quantifies the loss of perceived detail for objects viewed through a material.
When viewed through a material with high sharpness, an object appears sharp and distinct. As material sharpness decreases, the object appears blurry and obscured.
A material can often exhibit optical effects which are directional. These phenomena are often induced in plastic parts by specific processing faults.
Visible texture is a common feature of plastic films and causes a significant reduction in their see- through quality.
The Rhopoint ID is the only instrument that can measure directional effects in materials using the ID laboratory analysis software.
The images to the right show the visual impact of different ID Sharpness (S) values in vertical and horizontal directions.
Measuring directional effects can be used in advanced optical quality control and for adjusting processing parameters to obtain optimal transparency.
Note: Clarity and Sharpness do NOT capture poor optical characteristics associated with wavy/orange peel surfaces.
Quantifies the blurriness of an object when viewed through a material, results are proportionate with Sharpness, but the measurement scale is compressed and the measurement resolution is reduced.
Clarity is a scale used by traditional haze and clarity meters. When measured using the 8mm adaptor plate, Rhopoint ID Clarity data conforms to specifications written for these meters.
Inter-instrument Clarity agreement between Rhopoint ID and traditional sphere instruments for commercial plastic films (<1000μm) is typically <0.4% C (SD).
Inter-instrument Clarity agreement between traditional sphere instruments and Rhopoint ID for thick transparent plastic materials (<6mm) is typically <0.5% C (SD).
