Fast, high-resolution lenses for large line and area sensors

High-quality images at high magnification: Fast, high-resolution lenses for large line and area sensors

In the new "d.fine HR" product line, Qioptiq offers the high-resolution LINOS® d.fine HR 2.4/128mm 3.33x lens for demanding line and area sensors. Due to its very high luminous intensity, it offers high scanning speeds and is ideally suited for high-end inspection tasks in industrial manufacturing. When the beam splitter is perfectly matched to the lens, optimal coaxial line illumination is achieved, which enables line sensors to obtain sharp images with high contrast. In addition, its optional area module (d.fine HR area scanning module) also makes this high-resolution inspection lens ideal for use with 2D area sensors.

Figure 1: Quality Assurance at Qioptiq: High-resolution inspection in industrial manufacturing also requires suitable precision optics

The ever-tighter tolerance ranges in industrial production place ever-higher demands on optical inspection and quality assurance. In addition to industrial cameras with larger, higher-resolution image sensors, this also applies to the required industrial lenses. In order to fully utilize the high-resolution sensors of modern camera systems, high-performance optics from specialist manufacturers such as Qioptiq are required. The German subsidiary of Excelitas Technologies has expanded its existing product range and now offers high-resolution lenses with outstanding imaging performance and a good price-performance ratio.

A perfect combination

Given the high demands in the field of machine vision, the production of each individual component is a major challenge. However, even more critical is the interaction between components, assembly technology and adjustment systems. The entire production process chain must be perfectly coordinated, from the specific glass, to the optical design combined with the mechanical design, to the mounting and measurement technology. Qioptiq has gained extensive experience in this interaction over the years. Its new LINOS® d.fine HR 2.4/128mm 3.33x lens is based on a meltfit calculation; this means that each piece of glass used is measured and the optical design is then adjusted to the specific glass melt. This is a necessary step, because even the tightest tolerance levels offered by glass manufacturers are too large to guarantee a consistently high image quality in series production. In addition, the position of each individual lens element must be adjusted extremely precisely for tilting, centering and positioning. Qioptiq has developed its own assembly technology for this purpose, which far exceeds the mounting accuracy of usual standard lenses.

Very suitable for fully automatic inspection systems

The LINOS® d.fine HR 2.4/128mm 3.33x lens is targeted at manufacturers of image processing systems and fully automated inspection equipment. Available as a standard product, it reduces time to market for next-generation inspection systems, as there is no need to consider additional development time for custom lenses. Qioptiq also offers matching accessories for this lens: the d.fine HR prism module, which ensures optimal coupling of coaxial illumination in line scan applications. And, the d.fine HR area scan module, which can be used with area sensors. In addition, the d.fine HR standard system enables precise focusing and is suitable for industrial cameras with M72, M90 and M95 threads. The total length of the lens and prism module can be controlled to 177.1 mm, and the total length of the lens with the area scan module can be limited to 146 mm.

The optical performance of the new lens exceeds that of the well-established inspec.x L lens series on the market. The HR lenses deliver high-resolution, sharp images with uniformly high contrast across the entire image field and are therefore ideally suited for further electronic processing.

Figure 2: It has perfect resolution for inspecting the finest circuit structures on a wafer, for example.

Its fields of application include quality control in the production of wafers, flat screens, OLEDs, printed circuit boards and glass. Here, large areas must be scanned in short cycles with tolerances in the micrometer range. Thanks to its large aperture, the new d.fine HR lens is ideal for such applications and provides sufficient light to the sensor even in fast applications. With a focal length of 128 mm and a magnification of 3.33x, the lens meets industrial requirements and replaces the inspec.x L 4/105 3.5x. In addition, its relatively large working distance of 60 mm provides flexibility for integration into a wide range of systems and applications.

Figure 3: d.fine HR lenses with prism modules are used to couple coaxial illumination, ensuring the highest image quality with 16k/5µm and 16k/3.5µm line sensors

Diffraction-limited and distortion-free

LINOS® d.fine HR 2.4/128mm 3.33x achieves extremely high resolutions with up to 300 line pairs per millimeter in the object. It is optimized for an image circle of 82 mm, making it ideal for long-line sensors (16k/32k) and medium format large-area sensors (101MP/151MP). In addition, it features excellent color correction to ensure high imaging performance right up to the edges. Distortion is virtually non-existent in the large image circle of 82 mm. Its nominal value is less than 0.1%, so no software correction is required.

The high aperture of 2.4 compared to the magnification of 3.33x, and the resulting measured numerical aperture of 0.13, pushes the diffraction limit upwards, providing high resolution and light intensity. This helps to shorten exposure times and speed up the production process, thereby increasing yield. This is where the new lenses based on diffraction-limited design come into play. For comparison, the aperture of the inspec.x L series lenses is f/3.5 or f/4.

Precision manufacturing in Germany

The d.fine HR lens is the first in the LINOS machine vision lens family to support pixel sizes down to 3.5µm at magnifications greater than 1. In comparison, the inspec.xL lens is optimized for a pixel size of 5µm and theoretically achieves a maximum imaging performance of 50 LP/mm on the sensor with a contrast of 38% in a spectral distribution of 420-680 nm. The new d.fine HR lens also achieves these values ​​at 72 LP/mm across a large image field of 82 mm. In order to maintain this high quality in series production, a stable production process with high demands on assembly and measurement technology must be used. Qioptiq uses a variety of proprietary assembly technologies to ensure that the optical components are precisely aligned, centered and fixed in position to meet the tight tolerances. Qioptiq has state-of-the-art laboratories and measurement facilities to develop and manufacture high-quality inspection lenses. In addition to MTF systems from well-known manufacturers in the metrology industry, Qioptiq has also developed its own MTF system to demonstrate how to meet the special requirements of inspection lenses and support product development. Development, prototype manufacturing, series assembly and certification work are carried out in parallel in the new factory in Feldkirchen near Munich, Germany, which was built in 2010. The precision optical components of the lenses are precisely manufactured, coated and tested using the latest processes in Regen in the Bavarian Forest. This ultra-modern factory was put into operation in 2006.

Compared with Figure 5

100% Acid Test

All lenses are 100% MTF tested before delivery and certified to environmental requirements following the following ISO test procedures.

• Temperature: DIN ISO 9022-10-05-1 / 9022-11-05-1 / 9022-14-03-1

• Impact resistance: DIN ISO 9022-31-01-0

• Shock resistance: DIN ISO 9022-36-07-1

This ensures that Qioptiq's industrial lenses are rugged and durable, remain intact during transportation and storage, and function stably and for a long time in harsh industrial environments.

Of course, the LINOS® d.fine series also meets the environmental requirements of modern industrial products and complies with RoHS and REACH standards. Qioptiq is even more proud that it has been certified as a carbon neutral company since 2021, contributing to innovation and sustainable development.

Figure 6: Qioptiq has state-of-the-art machine vision lens manufacturing and testing facilities in Feldkirchen and Regen, Germany (here: MTF measurement of the new HR lens)

Perfectly coordinated modules

Qioptiq offers HR lenses in combination with prism modules or area scan modules. The beam splitter prism greatly facilitates the configuration of a complete optical system consisting of lens and illumination, as it provides optical coupling for the coaxial illumination of the line scan camera. This is particularly important for surfaces with high reflectivity, such as displays or wafers. Lens and beam splitter prism must form an optical unit and the components must be perfectly matched to each other. High optical requirements and mounting technology for the prism are also crucial here. Together, these components achieve the best possible diffraction-limited imaging performance. The mounting and connection of the lens to the camera and prism is done via a V-groove. This allows the position of prism and lens to be perfectly aligned and the illumination to be precisely adjusted.

If line illumination via a prism module is not required, the glass thickness of the prism block needs to be compensated, which is already taken into account in the lens design. The area scan module solves this problem. The biggest advantage is that, depending on the additional module, the same lens can be used for line sensors and area sensors with coaxial illumination.

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