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Caution: Federal law restricts this device to sale by or on the order of a physician or a practitioner trained and certified in its use. Assisted Hatchling, Embryo Biopsy and PGD are not recommended for routine use in all IVF patients.

The ZILOS-tk: About Laser Alignment & Beam Quality

The Importance of Laser Alignment

Beam quality and precise physical laser alignment (alignment to the optical center of all components) are crucial for the most accurate, safe, and reliable results. Because of this, our lasers are aligned and beam quality optimized only under strictly controlled and documented factory conditions, leaving nothing to chance.

All the ZILOS-tk lasers undergo rigorous testing, following several precise protocols. The lasers are not released to production unless the physical beam alignment and quality meet the highest standards.

A thin slit transit fixture is one of the controlled tests used to optimize beam quality. Varying results (both unacceptable and acceptable) of this test are shown here.

Test results for each ZILOS-tk module are documented and recorded in the Device History Log (by serial number) according to FDA requirements. You may request a copy of the test for your ZILOS-tk laser at any time.

As an ISO 9001:2000 registered company, we are dedicated to providing the highest quality product and meeting our customers needs and expectations.

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Fixed Laser for Precise Optical Alignment

Since even the smallest movement of the laser beam can affect alignment to the optical center, the ZILOS-tk uses a fixed laser with alignment locked to the precise optical axis. There is only one centered optical axis from the laser diode, through the collimator, to the dichroic mirror, and finally through the objective lens; thus, there is also only one corresponding target in the field of view where a laser aligned to the center axis can hit (at a 90° angle). It is impossible to maintain alignment to the optical axis at multiple target points within one field.

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The Difference between "Target Alignment" and "Physical Laser Beam Alignment"

It is important to realize that 'target alignment" and "physical laser beam alignment" are different and that both are required for safe ablation.

Target alignment refers to the correlation between the computer-generated target overlay on the video monitor and where the laser beam will strike on firing. As should occur with all laser systems for compliance with Good Laboratory Practices, each day before any embryos are ablated, the target alignment on the ZILOS-tk is confirmed using a simple validation procedure (no embryo is needed for this protocol).

However, the alignment of the computer generated target does not affect the laser beam quality; it is the physical laser beam alignment that affects the quality of the laser beam. Physical beam alignment refers to the angle and translational position of the laser beam as it passes through the various optical components (collimator lens, dichroic mirror, and objective). On the ZILOS-tk, the physical laser beam alignment is locked to the optical axis, thus this does not need to be confirmed daily to comply with Good Laboratory practices (though we do provide a method of validation so that user can see for themselves that the beam is aligned). Conversely, the physical beam alignment on multi component laser systems should be checked every day before first use, plus any time a component is removed and reinstalled, and whenever the microscope is moved.

The Mechanics of a Laser System

There are several vital components inherent to a laser microsurgery apparatus. In addition to the laser itself, a collimating lens, a dichroic mirror, and an objective that can transmit the beam are required:

  • Laser: 1480 µm, Infrared Class 1
  • Collimating Lens: A lens used to produce a beam of parallel light rays
  • Dichroic Mirror: An optical device which acts like an optical gate to split light into two colors ("di" = two, "chroic" = pertaining to color). The dichroic mirror reflects the infrared laser beam up through the objective, while the visible light passes through.
  • Objective: Must allow transmission of laser beam to the sample.
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Why Does the End User Not Need to Perform Laser Alignment on the ZILOS-tk?

Once the optimum translational and angular alignments and beam quality are achieved, the laser is "locked" into place, and does not move position. We are able to do this because all the components of the laser system are integrated into a single unit (see image below).

This "locking" process is similar to that used for aligning and locking microscope objectives. Just like you do not have to align the inside components of your microscope objectives, you also do not need to align the internal components of the ZILOS-tk, even if you switch microscopes.

Why Do Other Lasers Require Alignment On-site by the End User?

The reason other laser systems need to be checked on-site for alignment is that two or three separate components are used to get the beam from the laser source to the sample. For example, laser modules that are inserted into the fluorescent light port also must have a dichroic mirror inserted in the filter cube port, and the objective attached to the turret (see illustration below). That makes three separate components that must stay aligned at all times. Every time the module or filter cube is removed and reinserted, or the microscope is moved, alignment must be checked.

In systems where physical laser alignment cannot be locked, for the highest precision in physical beam alignment, there should be two available methods of adjusting the laser beam: 1) angularly and, 2) translationally (left to right, up and down).

In the ZILOS-tk, these four components are housed in close proximity within the same module. Thus, once the laser is aligned and locked down, it stays aligned.

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Why Using a Pilot Laser Does Not Automatically Equal an Optically Centered Laser Alignment (Physical Beam Alignment)

While a pilot laser can act as an indicator of the laser target ("target alignment"), simple use of a pilot laser does not automatically mean that the laser beam is aligned both translationally and angularly to the center axis of all optics components (physical beam alignment).

Based on public claims that the path of the pilot laser replicates that of the infrared laser, it follows that if the pilot laser is off-axis, the drilling laser will also be off-axis. If a pilot beam is off-axis, the diffraction rings will appear elliptical upon defocusing in both directions. Diffraction ring images representing varying degrees of off-axis pilot beam positioning are shown below, with the more severe on the right.

Astigmatic Diffraction Rings

A pilot laser that is optically aligned to the axis will show diffraction rings that remain circular throughout various focus points (see image below). The laser is only properly aligned if the diffraction rings maintain their circular appearance upon defocusing in both directions.

 

For an interactive presentation of the Airy diffraction pattern at various depths of field, please see the Molecular Expressions Optical Microscopy Primer (developed by the National High Magnetic Field Laboratory at Florida State University).

A wonderful interactive tutorial about the effects of an off-axis beam as an optical aberration may also be found at Molecular Expressions Optical Microscopy Primer. Take particular notice of how off-axis light entering the lens makes the diffraction rings elliptical. Only when the light is perfectly aligned through the center of the optical axis are the diffraction rings circular.

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