THORLABS OCTH Series User manual

OCTH SERIES
OCT Handheld Scanner,
Lens Kit, and
Sample Z-Spacer
User Manual

Original User Manual – not translated

Table of Contents
Chapter 1 Warning Symbol Definitions....................................................................................... 1
Chapter 2 Introduction .................................................................................................................. 2
2.1. Safety........................................................................................................................2
2.2. Care and Maintenance.............................................................................................3
2.2.1. Optical Cleaning..............................................................................................................3
2.2.2. Service ............................................................................................................................3
2.2.3. Accessories and Customization......................................................................................3
Chapter 3 Scanner Compatibility................................................................................................. 4
Chapter 4 Installation .................................................................................................................... 5
4.1. OCTH Handling........................................................................................................5
4.2. OCTH Connections..................................................................................................6
4.2.1. Connecting the Electrical Control Interface.....................................................................6
4.2.2. Connecting the Optical Fiber to the OCT Base Unit.......................................................7
4.2.3. Fiber Cleaning Techniques Using the FBC1...................................................................8
4.3. Integration................................................................................................................9
Chapter 5 Description ................................................................................................................. 10
5.1. Theory ....................................................................................................................10
5.1.1. Signal Generation .........................................................................................................10
5.1.2. Limitations.....................................................................................................................10
5.2. Optical Design .......................................................................................................11
5.2.1. Common Path Setup.....................................................................................................11
5.2.2. Dual Path Setup (Special).............................................................................................11
5.2.3. Realization.....................................................................................................................12
5.3. Components...........................................................................................................13
5.3.1. OCTH Base Module......................................................................................................13
5.3.2. Reference Adjustment...................................................................................................15
5.3.3. Push Buttons.................................................................................................................17
5.3.4. OCTH Scan Lens Kits (Accessory)...............................................................................18
5.3.5. Sample Z-Spacers (Accessory) ....................................................................................19
Chapter 6 Troubleshooting......................................................................................................... 21
Chapter 7 Certifications and Compliance................................................................................. 22
Chapter 8 Specifications............................................................................................................. 23
Chapter 9 Warranty...................................................................................................................... 24
9.1. Lasers and Imaging Systems................................................................................24
9.2. Non-Warranty Repairs...........................................................................................24
9.3. Warranty Exclusions .............................................................................................24
Chapter 10 Mechanical Drawings ................................................................................................ 25
Chapter 11 Regulatory .................................................................................................................. 26
11.1. Waste Treatment is Your Own Responsibility.....................................................26
11.2. Ecological Background.........................................................................................26
Chapter 12 Thorlabs Worldwide Contacts.................................................................................. 27

OCTH Series Chapter 1: Warning Symbol Definitions
Rev B, April 08, 2016 Page 1
Chapter 1 Warning Symbol Definitions
Below is a list of warning symbols you may encounter in this manual or on your device.
Symbol
Description
Direct Current
Alternating Current
Both Direct and Alternating Current
Earth Ground Terminal
Protective Conductor Terminal
Frame or Chassis Terminal
Equipotentiality
On (Supply)
Off (Supply)
In Position of a Bi-Stable Push Control
Out Position of a Bi-Stable Push Control
Caution: Risk of Electric Shock
Caution: Hot Surface
Caution: Risk of Danger
Warning: Laser Radiation
Caution: Spinning Blades May Cause Harm

OCTH Series Chapter 2: Introduction
Page 2 MTN004428-D02
Chapter 2 Introduction
2.1. Safety
Please read this manual carefully before operating the OCTH handheld scanner. Please also read any manuals
for the systems being connected to the OCTH handheld scanner.
All statements regarding safety and technical specifications will only apply when the unit is operated correctly.
ATTENTION
This equipment is intended for laboratory use only and is not certified for medical applications,
including, but not limited to, life support situations.
WARRANTY WARNING
There are sensitive electronic and optical parts in the OCTH.
Any modification or servicing of this system by unqualified personnel renders Thorlabs free of
any liability.
Any modification of the MEMS scanner, the internal electronics or the camera may cause loss of
the factory optical alignment.
The connector cable of the device contains an optical fiber – stress on this cable should be as
low as possible. The radius of the cable may not be below 75 mm (2.95 inch) at any time.
This device can only be returned for service when it is packed into the complete original
packaging, including all foam packing inserts. Please contact Thorlabs’ tech support
([e-mail]) for replacement packaging if the original packaging has been lost.
LASER RADIATION WARNING
When a light source (e.g. SLD, laser) is being coupled into the OCTH, please observe the
appropriate laser safety precautions for your own protection. During normal operations, laser
light will be present within the scanner and will also be emitted from the scanner.
When the OCTH is equipped with a Thorlabs Scan Lens Objective and connected to a Thorlabs
OCT Base Unit, this OCT Base Unit gives the limit for the laser radiation – please check the
manual of the Base Unit for your own safety.
The OCT System may not be switched on, if there is no objective mounted on the OCTH.
In addition, laser light may be emitted from unexpected locations, e.g. if the fiber broke in the
connector cable.

OCTH Series Chapter 2: Introduction
Rev B, April 08, 2016 Page 3
2.2. Care and Maintenance
The scanner should be treated with care, particularly during transportation and unpacking. Hitting or dropping
the scanner can damage the unit and lower system performance. If mishandling occurs, misalignment of the
optical components may occur, leading to a decrease in image quality. In this situation, the system should be
realigned by qualified personnel. Please contact Thorlabs’ technical support ([email protected]) for
more information.
Do not store or operate in a damp, closed environment.
Do not store or operate on surfaces that are susceptible to vibrations.
Do not expose to direct sunlight.
Do not use solvents on or near the equipment.
Keep the unit away from dust, dirt, and airborne contaminants, such as cigarette smoke. The system is
not designed for outdoor use. Protect the equipment from rain, snow, and humidity.
Do not subject the equipment to mechanical and thermal extremes. Protect the equipment from rapid
variations in temperature.
Handle all electrical and fiber connectors with care. Use of excessive force to form electrical or fiber
connections may damage the connectors.
The connector cable of the device contains an optical fiber –stress on this cable should be as low as
possible. The radius of the cable may not be below 75 mm (2.95 inch) at any time.
2.2.1. Optical Cleaning
The most common cause of low signal intensity is a contamination of the fiber due to airborne particles. To
minimize the fiber’s exposure to air, avoid unnecessary disconnections of the optical fiber patch cable. Ensure
that the connection is tight, and keep the fiber as straight as possible without placing it under tension. It is also
advisable to check the fiber when making other adjustments to the optical system, such as changing the
objective.
Thorlabs’ Fiber Inspection Scope (Item # FS200) can help determine when the fiber needs cleaning. We
recommend our Fiber Connector Cleaner (Item # FCC-7020) to quickly clean the fiber tips.
2.2.2. Service
Only trained and approved Thorlabs personnel are allowed to service the system. Please contact Thorlabs’
technical support ([e-mail]) for more information.
2.2.3. Accessories and Customization
The OCTH series OCT scanners are Thorlabs-qualified accessories for Thorlabs’ OCT Systems (i.e., our
CALLISTO, GANYMEDE-II, and TELESTO-II). We strongly suggest using Thorlabs’ OCTH-LK Lens Kits with
the OCTH, as they were specifically designed to work together.
In order to achieve the intended performance, this scanner should only be used with qualified parts. Please hold
a conversation with Thorlabs’ technical support to determine if other parts you wish to use are compatible. Any
modification or servicing of this system by unqualified personnel renders the warranty null and void, leaving
Thorlabs free of any liability.

OCTH Series Chapter 3: Scanner Compatibility
Page 4 MTN004428-D02
Chapter 3 Scanner Compatibility
The OCTH is a standalone, preassembled, integrated accessory to a Thorlabs OCT Base Unit. It is intended
for light-weight handheld operation providing ergonomic handling for imaging applications where mobility is
required.
This scanner is available in versions for different wavelength ranges.
The OCTH-900 handheld scanner for OCT systems working in the 900 nm regime.
The OCTH-1300 handheld scanner for OCT systems working in the 1300 nm regime.
In this manual we will use abbreviation for the OCTH scanner as follows:
OCTH OCTH-900 or OCTH-1300
For common statements the abbreviation “OCTH” is used for both setups.
The OCTH scanners are fully compatible with all Thorlabs OCT Base Units of the CALLISTO, GANYMEDE,
and TELESTO series.
The table below gives a short overview of the different handheld scanners, their usable wavelength range and
lists preferred OCT Base Units.
Handheld Scanner
Wavelength Range
OCT Base Unit
OCTH-900
850 nm – 1000 nm
CALxxx
GANxxx
OCTH-1300
1200 nm – 1400 nm
TEL13xx
Table 1 Usable Wavelength Range of OCT Scanner
The are selective optical components in the scanner. Depending on the type of the OCTH, their specifications
are different.

OCTH Series Chapter 4: Installation
Rev B, April 08, 2016 Page 5
Chapter 4 Installation
4.1. OCTH Handling
The OCTH offers various options for handling during OCT image acquisition to match the individual needs of
the imaging. The housing ergonomics are specially designed to allow for both right- and left-handed operation
and using either your thumb or index finger for pushing the buttons on top. The OCTH enables pointing it at a
sample while holding it at the rear end grip but you can also hold it at the front part and still be able to reach the
push buttons. The long cable connecting the OCTH to the OCT Base Unit gives you flexibilityto move and reach
for samples over a large span. If connected properly a green light in the middle of the push buttons indicates
that the OCTH is running.
ATTENTION
When pulling at the OCTH too hard it may cause the connected OCT Base Unit to move and fall
off. This could severely damage the OCT Base Unit. Make sure to stay within reach of the cable
length! Secure the OCT Base Unit against falling off!
Extreme pulling may cause the strain-relief to give way! This could severely damage the
electrical and optical connections. Do not inadequately pull the connection cable!
Figure 1 Right-Handed Operation of OCTH Holding the Rear End Grip

OCTH Series Chapter 4: Installation
Page 6 MTN004428-D02
4.2. OCTH Connections
4.2.1. Connecting the Electrical Control Interface
Make sure that the OCT Base Unit is switched off.
The electrical probe control cable and optical fiber are permanently connected to the OCTH. The electrical probe
control cable connects to a Thorlabs OCT Base Unit via a standard Thorlabs OCT probe control AUX interface
with one alignment key. For backwards compatibility to Thorlabs OCT Base Units fabricated prior to 2015
adapter cables are available to connect to AUX interfaces with two alignment keys. Please contact Thorlabs’
tech support for information regarding the pin configuration.
Figure 2 AUX interface with one and two alignment keys
Attach the control probe cable of the OCTH to the Aux connector on the Thorlabs OCT Base Unit. This interface
is located at the back of the OCT Base Unit. Align the red dot of the plug to the alignment mark of the port. Push
the connector into the plug until a “click” sound is heard. This click indicates that the connector is locked.
Figure 3 Installation of the Electric Connector at the Thorlabs OCT Base Unit

OCTH Series Chapter 4: Installation
Rev B, April 08, 2016 Page 7
4.2.2. Connecting the Optical Fiber to the OCT Base Unit
ATTENTION
When installing the fiber, make sure that the fiber tip does not get contaminated by dust.
Thorlabs’ FS200 Fiber Inspection Scope and MCC-7020 Fiber Connector Cleaner are useful for
keeping the optical path clean.
Do not touch the fiber tip!
The fiber connector of the OCTH needs to be plugged in the FC/APC fiber connector on the back of the Thorlabs
OCT Base Unit.
Attention
The fiber connector needs to be oriented such that alignment key slides into the key slot of the
OCT Base Unit connector. If the key is NOT properly aligned with respect to the key slot, you will
still be able to screw in the fiber connector, but significant light intensity losses will result from
this incorrect connection.
Figure 4 Installation of the Fiber Connector at the Thorlabs OCT Base Unit
Figure 5 Fiber Installation Detail

OCTH Series Chapter 4: Installation
Page 8 MTN004428-D02
4.2.3. Fiber Cleaning Techniques Using the FBC1
This section details how to clean fiber bulkheads and fiber connectors using the FBC1 one-step cleaner.
Using Extended Mode
Figure 6 FBC1 Extended Mode
To use extended mode, pull the tip outward while simultaneously pushing down on the lock button. Extended
mode is useful for panels with multiple bulkhead connectors or other tight spaces.
Cleaning Fiber Bulkheads
Figure 7 FBC1 Extended Mode
Remove the guide cap completely from the device, and insert the tip of the cleaner into the bulkhead connector.
Push the case to start the cleaning process; a click indicates that the cleaning is complete.

OCTH Series Chapter 4: Installation
Rev B, April 08, 2016 Page 9
Cleaning Fiber Connectors
Figure 8 Cleaning Fiber Connectors
Open the cover on the guide cap, and insert the fiber connector over the guide cap. Push the case to start the
cleaning process; a click indicates that the cleaning is complete.
4.3. Integration
The OCTH only works properly when used together with an OCT system that is running this scanner.
We suggest to make use of this scanner together with Thorlabs OCT Base Units like the CALLISTO,
GANYMEDE II, or TELESTO II.
Make sure that the wavelength range of the base unit corresponds to the wavelength range of the OCTH.
For the full integration into such a system, please refer to the user manual of the system.

OCTH Series Chapter 5: Description
Page 10 MTN004428-D02
Chapter 5 Description
5.1. Theory
5.1.1. Signal Generation
Spectral Domain Optical Coherence Tomography (OCT) generates cross-sectional images up to several
millimeters deep into tissue. The images are assembled by performing a series of scans at adjacent, increasing
depths, allowing 2D and 3D reconstruction of the specimen.
The Thorlabs SD-OCT Base Unit (i.e., the CALLISTO, GANYMEDE-II, or TELESTO-II), to which the OCTH
might be attached, consists of a broadband light source with a high-speed spectrometer. In the scanner, the
light is split into two arms. In one arm the light is sent to the specimen, where it is back-reflected and back-
scattered back into the scanner and to the spectrometer in the base unit; in the other arm the light is sent to a
stationary optical reference arm.
In custom setup, the light is sent directly into the specimen without splitting and guided back into the scanner;
the other arm is a dedicated external optical reference arm.
The phase delay of the back-reflected and back-scattered light (with respect to the stationary reference) is
recorded as a function of wavenumber, and a Fast Fourier Transform (FFT) yields the cross-sectional images
as a function of sample depth.
5.1.2. Limitations
The spatial resolution and sensitivity of the OCT system using the OCTH depends on several parameters,
including the following:
Imaging speed: The internal MEMS scanner limits the system speed. It is recommended to stay below
28 frames or B-Scans per second in the 2D Mode which corresponds e.g. to 1024 A-Scans per B-Scan
at 28 kHz system speed. Greater imaging speeds will distort the scan and degrade the duty cycle of the
acquisition. This is also valid for the 3D mode, where only the fast axis has this speed restriction and
should staybelow the 28 B-Scans per second. The slow axis settings are independent of that restriction.
The ThorImage software indicates this limit with a warning sign.
Correct Wavelength Range: The optical components within the OCTH are optimized for a wavelength
range centered at 0.9 µm or 1.3 µm, depending upon the model you ordered.
Optical Power: The sensitivity of the OCT system is directly related to the intensity of the light returning
from the sample. Dirty fibers, blocked or cropped beams, condensing, and humid environments tend to
reduce the light intensity collected from the sample, directly reducing the image quality.
Physical Movements: OCT systems use a camera to detect the phase relation of the light returning
from the sample. Even small movements of the specimen in relation to the optical reference arm will
“wash out” the wavenumber-resolved phase contrast, affecting the image.
Imaging: In a fiber-based OCT setup, the light returning from the sample is focused into the core of an
optical fiber (through which the light propagates further). Hence, the fiber can be thought of as a spatial
filter for the light. This filter has an effective diameter, referred to as the “Mode Field Diameter”, of only
a few microns. (The mode field diameter for single mode use is bigger than the core diameter.) Poor
focusing, caused by optical aberration or misalignment, therefore leads to loss of contrast and
sensitivity.

OCTH Series Chapter 5: Description
Rev B, April 08, 2016 Page 11
5.2. Optical Design
5.2.1. Common Path Setup
As shown below, the OCTH is factory-configured such that the sample beam and reference beam are generated
after the beam leaves the fiber. This allows us to use single-mode optical fiber to transport the beam into the
scanner while minimizing the use of free-space propagation.
This approach avoids problems that can degrade image quality, related to optical phenomena like polarization
mode dispersion (PMD) and birefringence, and makes the performance of the system independent from the
length of the single-mode fiber.
Figure 9 Diagram of the Common Path Setup
5.2.2. Dual Path Setup (Special)
Shown below is an alternative beam geometry to the Common Path Setup when the scanner is ordered in a
configuration without reference. The sample beam and reference beam are generated within different fibers,
before the beam exits into free space. In this configuration, the scanner becomes the sample arm of the
interferometer. By using two different fibers, the beam splitter used in the Common Path Setup is no longer
needed.
This configuration allows single mode optical fiber to be used to a greater extent within the setup, and the OCTH
is fully capable of this geometry. While this approach is able to provide greater sensitivity due to the absence of
the beam splitter (which reduces the intensity of the light that returns to the fiber), it issignificantlymore sensitive
to the optical phenomena mentioned before. Please contact Thorlabs’ tech support for details.
Figure 10 Diagram of the Dual Path Setup

OCTH Series Chapter 5: Description
Page 12 MTN004428-D02
5.2.3. Realization
The basic optical layout of the OCTH in Common Path layout is illustrated below.
Figure 11 Optical Layout of the Common Path Setup
The output of an FC/APC fiber is collimated and routed to a beam splitter. Here, the beam is divided into a
sample beam and a reference beam, similar to a Michelson interferometer. The sample beam is routed over a
2-axis MEMS mirror to allow for scanning in two axes with a common pivot point. The scan objective then
focuses the beam in the sample. Back-scattered and back-reflected light is collected bythe scan objective again
and travels back to the fiber. The light reflected into the reference arm is retro-reflected back into the fiber. There
is an optimum intensity for the reference light that can be adjusted using the reference intensity adjustment
screw which will open or close the variable aperture inside the imaging scanner.
For the Dual Path layout the reference components are not inserted.
Figure 12 Optical Layout of the Dual Path Setup

OCTH Series Chapter 5: Description
Rev B, April 08, 2016 Page 13
5.3. Components
The OCTH is intended as an accessory for use with Thorlabs OCT Base Units.
Figure 13 OCTH Scanner
An OCTH contains a scanning system with adjustment options for intensity and integrated reference
components. For full usage of the OCTH, additional kits like the Lens Kit are strongly recommended. The OCTH
is specially designed with regard to optical path length. Changing the Lens Kit will hardly change optical path
length in the sample arm, therefore no adjustment of reference arm optical path length is required.
The following sections describe the module and possible accessories in detail.
Please contact a member of the Thorlabs’ technical support team to determine if other parts you wish to use
are compatible. Any modification or servicing of this system by unqualified personnel renders the warranty null
and void, leaving Thorlabs free of any liability.
5.3.1. OCTH Base Module
The OCTH base module provides high-speed, two-dimensional (X and Y) raster scans of the specimen. The
clear aperture of the scan mirror used within is Ø 3 mm. Due to the use of a 2-axis MEMS mirror both raster
scans in X and Y share a common pivot point. The module also contains a high-resolution video camera for
recording the sample during the measurement.
Figure 14 OCTH Base Module

OCTH Series Chapter 5: Description
Page 14 MTN004428-D02
ATTENTION
The optical fiber is inside the probe control cable and has to be handled with care.
Avoid any unnecessary force that may cause the fiber to bend sharply and break.
Cap end face when connector is not in use.
The electrical probe control cable and optical fiber are permanently connected to the OCTH. The electrical probe
control cable connects to a Thorlabs OCT Base Unit via a standard Thorlabs OCT probe control AUX interface
with one alignment key. For backwards compatibility to Thorlabs OCT Base Units fabricated prior to 2015
adapter cables are available to connect to AUX interfaces with two alignment keys. For identification of your
probe control interface and connection requirements please refer to chapter 4.2.1 or contact Thorlabs’ tech
support. Please contact Thorlabs’ tech support for information regarding the pin configuration.
The optical fiber connects to a standard FC/APC receptacle at a Thorlabs OCT Base Unit, see chapter 4.2.2.
The optical output heading in direction of the reference is equipped with an aperture which is manipulated using
the reference adjustment screw. In order to adjust the reference intensity, it is necessary to rotate the reference
intensity adjustment screw. The reference adjustment screw is located inside the OCTH housing, see chapter 0
below.
ATTENTION
The functionality of the reference light or length adjustment does not require inadequate torque.
Modifications and adjustments have to be done in a clean, dust-free environment.

OCTH Series Chapter 5: Description
Rev B, April 08, 2016 Page 15
5.3.2. Reference Adjustment
In order to access the screw for the reference adjustment the scanner housing needs to be opened. Please use
a Phillips 1 head screw driver to remove the screw on the lower rear end of the scanner as indicated in Figure
16.
Figure 15 Remove Housing Fixation Screw
Carefully lift off the lower part of the housing.
Figure 16 Opening the OCTH

OCTH Series Chapter 5: Description
Page 16 MTN004428-D02
Reference Intensity Adjustment
The reference adjustment screw is now accessible inside the scanner. Please use the provided 1.5 mm hex
screw driver to rotate the screw for reference intensity adjustment. Rotating clock-wise will reduce the reference
intensity, rotating counter-clock-wise will increase it. As a qualitative indication, observe the reference intensity
bar in the OCT software. Please refer to the Software Manual for additional guidance.
Reference Length Adjustment
After opening the lower part of the housing the red reference length adjustment wheel is accessible inside the
scanner.
Plus and minus indicate the direction of the length adjustment. Plus increases the reference length, minus
decreases it. As a qualitative indication, observe the image in the OCT software. Please refer to the Software
Manual for additional guidance.
After finish the reference intensity or length adjustment, please close the housing again by placing the lower
part of the housing back in its place and tightening the Phillips screw.