New Wavelengths Added

The established PROdigii digital laser module can now be offered with the following wavelengths: 375nm, 405nm laser, 450nm, 905nm, and 940nm. These additional wavelengths in UV, blue, and IR mean that the functionality packed PROdigii can address many additional applications. The 375nm UV digital laser module is suitable for UV curing applications. The blue 405nm digital laser is ideal for both 3D printing and particle measurement. The new 450nm laser is well suited to spectroscopy applications. The additional infrared wavelengths, 905nm and 950nm, make the PROdigii an ideal solution in robotics and gesture recognition as well as LiDAR applications.

The PROdigii Digital Laser Module Range

The PROdigii digital laser module delivers high performance, stability, and control even in challenging operating environments. The new wavelengths are available in addition to the existing 520nm, 638nm, 660nm, and 808nm options. It has a compact cylindrical form factor and is configurable to your application needs. It is offered with output powers up to 500mW CW, 1W pulsed, and various diffractive options including uniform line and elliptical spot. The PROdigii uses a digital RS485 communication interface which provides intelligent control and monitoring. In addition to the applications mentioned above, 3D measurement, high precision alignment, chemical, and biomedical analysis as well as high speed automated inspection will benefit from the high -performance, monitoring, and control offered by PROdigii.

Key Features

• Wavelengths: 375nm, 405nm, 450nm, 520nm, 638nm, 660nm, 808nm, 905nm, 940nm
• Compact, high performance, digital laser module
• RS485 intelligent control and monitoring
• Integral thermal management
• Uniform line, elliptical sport or diffractive patterns available
• Output power up to 500mW (CW); 1W (pulsed)

Benefits of Digital Laser Modules

Digital laser modules are most useful for applications that require enhanced control and monitoring functionality. Often an existing system will also have another digital component, in which case having one control system for all elements is key as it keeps the design concise and increases ease of use. One benefit of using a digital interface is output power control, which leads to enhanced laser diode life. Digital monitoring also allows for preventative maintenance to be scheduled rather than relying on the reactive repair. You can learn more about digital interfaces in our previous blog post on “The Benefits of a Digital Laser Module”.

PROdigii Digital Laser Interface

Thermal Management

Thermal management is another benefit of PROdigii digital laser modules. To prevent heat damage, a thermal pathway is needed to ensure heat flows away from the laser diode when lasing. In the PROdigii laser module, a Peltier thermo-electric cooling device (TEC), which is built into the compact form factor, is used to pump out the heat. The superior thermal management provides exceptional wavelength stability and makes the PROdigii ideal for use in challenging operating environments. You can learn more about thermal management in laser modules in our previous blog post “Thermal Management in Compact, High Power Laser Modules”.

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PROdigii’s innovative design incorporates a digital RS485 communication interface as well as integral thermal management. The RS485 intelligent control and monitoring interface provides ease of integration and in-service system function monitoring. Integrated thermal management enables exceptional wavelength stabilization with enhanced diode life. Digital control and monitoring provide superior output power control flexibility.

Digital Laser Module: Key Features

• RS485 intelligent control and monitoring
• Integral thermal management
• Wavelength options from 405nm to 850nm
• Uniform line generating or focused elliptical beam optical configurations
• Output power up to 500mW (CW); 1W (pulsed)

Digital Laser Module: Key Applications

• 3D measurement especially in high ambient light or temperature conditions
• High precision alignment
• Chemical and biomedical analysis and spectroscopy
• High speed automated inspection

Optical Options

As a configurable platform, PROdigii is available in a range of wavelengths from 405nm to 850nm with user-defined output power profiles up to 500mW continuous wave or 1W pulsed.

The digital laser platform can be configured as a uniform line generator for 3D measurement or with a focused elliptical output beam for analytical, spectroscopic or high-precision alignment applications. The laser module also provides an ideal solution for high-speed automated inspection, chemical and biomedical analysis and spectroscopy.

PROdigii’s compact, cylindrical form factor and custom mounting options make for straightforward integration into OEM products and machine vision systems.

The post New Digital Laser Diode Module appeared first on Prophotonix.

Requirement

In this application, the laser line provides a guide for the customer’s employees to connect the various sheets of metal within tight tolerances. As a result, the application required a uniform line thickness and line straightness. The existing laser module solution did not adequately meet the customer’s requirements.

Challenge

The laser module, operating at 660nm wavelength, needed to project a laser line with a working distance between 18 to 1800 inches (450mm to 4600mm). Across this working distance, the laser line needed to remain in focus. The challenge: to build a module with a depth of focus of 197 inches (5000mm), and a line width uniformity of 0.08 inches (2mm) along the length of the line and the entire range of working distances. Finally, the line straightness could not deviate beyond 0.0083°.

Line Measurement Technique

There are different methods of measuring line straightness in a laser. It was critical to develop a consistent and reliable line straightness measurement protocol between our engineers and our customer. A rotational technique, developed by ProPhotonix, accomplished the precise, accurate and reliable results across the long working distance.

Why Use Root Mean Square Value (RMS)?

If we sample the line thickness at tiny intervals we may get slightly different values. We use root mean square value to give us an average value over time. By squaring each value, adding up the square and dividing by the number of measurements we get the average square or mean square. Taking the square root of that gives us the “root mean square” (RMS) average value, a more accurate reflection of the beam width over time.

Results

A baseline assessment of the legacy module with multiple line straightness measurements, taken at different working distances for the legacy module, provides the starting characteristic. Tests on the legacy module showed a line thickness RMS value of ~600µm, at 600mm working distance. This is equivalent to a line straightness of 5.4%. The profile across the projected laser line is neither symmetric or consistent . The test results on the ProPhotonix module gave an RMS value of 37µm at 600mm projection distance, equivalent to a straightness of 0.6%.

Figure 2. Graph showing a comparison of line straightness between the legacy module (a) and the 3D PRO (b) The legacy module has a line straightness value of 127µm. The 3D PRO has a line straightness value of 25.5µm.

Solution

Final results showed that the optimum solution to maximize depth of focus was to employ an AF version of our standard laser line generator module, where the apex of the line generating lens was precisely oriented to the longest axis of the elliptical beam. The results are a line straightness of 0.129%, versus the customer specification of 1% maximum.

To learn more about laser line generators from ProPhotonix, contact us.

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Laser Line Generator

A laser module which utilizes a cylindrical lens, known as a laser line generator, is sufficient for the majority of applications. A cylindrical lens produces a non-uniform, Gaussian laser profile with intense center area and fading edges along the projected line. Line modules utilizing these lenses are an easy and inexpensive solution but deficient in optical performance and uniformity.

Structured Light Laser – Powell Lens

A laser module utilizing a Powell lens, often referred to as a structured light laser, is preferred for applications with more exacting requirements. A Powell lens resembles a round prism with a two-dimensional aspheric element on its apex. The output line from a Powell lenses is a uniform distribution of energy. This is achieved when the laser beam hits the apex causing spherical aberrations (imperfection of the produced image) within the lens redistributing the light such that it decreases the light in the central area of the line while increasing the light intensities at the ends of the line. The output is an optically efficient, uniform line.

Key Considerations

Beam Width

The powell lens performance is very sensitive to beam diameter. It is also wavelength dependent. To get an even distribution of energy, the apex curvature needs to be precisely optimized for a particular laser beam width.

Fan Angle

The fan angle of the output beam is dependent on the refractive index of the glass and the roof angle of the Powell lens. The steeper the roof and the higher the refractive index, the wider the fan angle and the longer the line of a given projection distance. In extreme fan angles (90° – 125°), the Powell lens is more difficult to manufacture and prone to unintended aberrations in the output beam. As a result of these manufacturing issues, structured light laser modules that incorporate Powell lens tend to more expensive than line generator modules but with a much better beam characteristic.

Powell Lens Configuration

The Powell lens has two configurations based on lens placement relative to the incoming laser beam. Powell lens positioning directly affects depth of focus and the thickness of the laser line. To achieve a narrow incident beam orientation, a thin laser line with a small depth of focus is generated (we refer to this as AS configuration).

To achieve a wide incident beam orientation, a thicker laser line with a large depth of focus is generated (we refer to this as AF configuration). This configurability along with variation on lens properties (focal length, etc) allows for a wide variation of customer laser line requirements.

Conclusion

For the most part, using cylindrical lenses are sufficient for certain customer applications. However, if your application requires uniform distribution of light, a structured light laser is required.

The post Benefits of Structured Light Laser vs Laser Line Generator appeared first on Prophotonix.

The structured light source would generally be in the form of a line (or series of lines), a matrix of dots or in some cases a randomly generated pattern. There are a number of key requirements for consideration when choosing a structured light laser:

Uniformity

Uniformity of the line projected by a structured line laser is important in inspection. If the line is not uniform, the image captured by the camera will vary in intensity over the inspection area which would affect measurement accuracy.

There are several different levels of uniformity which can be grouped into:

1. High uniformity

High uniformity lasers are generally used in applications where high measurement resolution is required across the full line, for instance where the object has a surface which is flat or smooth such as that found in semiconductor applications (e.g. wafer inspection). In this particular application, the customer is looking for non-destructive inspection to detect any defects such as an uneven surface, scratch or a crack which may occur during the production process.

2. Low uniformity

Lasers with a lower uniformity level are acceptable for applications where measurement accuracy is less critical, and when the extremities of the line are not captured by the camera.

Depth of Focus

The depth of focus is an important characteristic which can determine the usable range of the laser around the focal position of the line. The depth of focus is defined as follows:

where B is the line thickness at the focusing point (measured at 13.5% intensity level) and λ is the wavelength of the laser.

There are two typical working conditions depending on the object being measured:

1. Short depth of focus
2. Long depth of focus

1. Short depth of focus

Short depth of focus is used where the line thickness is very thin such as semiconductor applications. It is important when you need to detect minute details such as surface quality. Whilst this offers the advantage of a thinner line at the focal point, beyond the focal point the line would diverge quickly reducing the measurement accuracy accordingly.

2. Long depth of focus

For objects which have larger geometrical variations in the z-axis its important that the line thickness remains within an acceptable range, in this case the measurement resolution is lower but the range over which measurements can be taken is increased.

Fan Angle

The fan angle is related to the projection distance and the size of the item that you are inspecting. A structured light laser solution provider can determine the system fan angle you require depending on your application. The working distance of the laser determines the fan angle in order to cover the size of area/item that you are inspecting.

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Line Quality

The quality and accuracy of the measurement provided by a machine vision laser is important. Several factors can affect line quality including the design of the module, optics and the internal mechanical structure of the module minimising internal reflections.

Conclusion

In selecting a structured light laser, one needs to consider several important parameters. We have listed the most common elements which the majority of customers require in order to identify the solution for their application. These parameters are: uniformity, depth of focus, line thickness, fan angle and line quality.

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