Cameras without sensor cover glass: selection considerations

A request for a camera without sensor cover glass should start with an optical requirement, not a modification. The unwanted reflection, spectral cutoff or focus error might come from a different layer entirely. This guide helps you identify that layer, estimate the optical consequences and prepare a specification for a factory-configured camera. It also explains why a compact board camera is not evidence of an exposed sensor, and what to verify before committing to a custom configuration.

Decide which optical layer causes the problem

Several transparent components can sit between the lens and the photosensitive surface. Their functions overlap, so location and construction matter more than the word “glass.”

Removing an infrared-cut filter does not necessarily remove the sensor cover. Conversely, a package cover can carry a coating that changes spectral transmission. A camera described as having no front window may still contain a covered sensor.

Ask for an optical stack drawing or a written description identifying every relevant layer. For compact assemblies, the M12 lens selection guide explains related lens-format and infrared-cut considerations. Do not assume the lens, camera and sensor package use the same filtering arrangement.

The first decision is therefore simple: specify the layer that must change and the measurable reason it must change.

Quantify the optical reason before specifying a change

A plane-parallel plate in a converging beam changes the best-focus position. Its effect depends on thickness, refractive index and the surrounding optical arrangement. A lens designed around a particular sensor window may also rely on that window for its aberration correction.

For a plate replacing an equal thickness of air, a useful paraxial estimate is:

This estimates the axial displacement introduced by the plate near normal incidence. It does not predict image quality across the field or fully describe a high-numerical-aperture system.

Worked example

Suppose an optical design includes a plate with a thickness of 0.50 mm and a refractive index of 1.50 at the operating wavelength.

Removing that plate reverses its contribution to the focus displacement. The calculation gives a starting estimate, not a camera adjustment specification. The actual assembly may contain additional filters, different glass or optics designed around the original stack.

Refocusing can compensate for an axial focus change, but it does not necessarily correct spherical aberration or other image-quality changes. This distinction matters with fast lenses, microscope objectives and other demanding optical systems.

If your real problem is reaching focus mechanically, first review focal length versus back focus in board cameras. An incorrect mount spacing or lens choice should not become an unnecessary sensor-package customization.

Check wavelength and reflection requirements separately

A spectral problem needs a transmission requirement. State the wavelength band, the required response and the illumination conditions. “No glass” is not a complete spectral specification.

The sensor itself must respond adequately at the intended wavelength. Removing a window cannot create sensitivity that the photosensitive material does not have. Remaining coatings, color filters, lens elements and adhesives may also limit the optical path.

For a transmission concern, request information covering the complete camera configuration rather than a generic glass-material curve. Ask whether the information includes coatings and any remaining filters.

For reflections or fringes, document the illumination geometry and bandwidth. Parallel optical surfaces can produce interference under sufficiently coherent illumination. However, unwanted reflections can also originate in the lens, a separate filter or the target.

Before requesting a glass-free configuration, compare these alternatives:

• A different antireflection coating, if the factory can provide one.
• A different filter arrangement that preserves the sensor package cover.
• A lens corrected for the existing optical stack.
• A change in illumination angle or bandwidth, where the inspection permits it.

These are options to evaluate, not interchangeable fixes. A coating change will not solve every absorption problem, and refocusing will not remove every reflection.

Compare camera architectures without assuming sensor construction

Both area scan cameras and board-level cameras can be starting points for a custom optical requirement. Packaging determines integration work, but it does not establish whether the sensor has cover glass.

The LS-CMR-0053 is a GigE area scan camera. Use its catalog information as a reference for the camera architecture, not as evidence of a glass-free sensor configuration.

The LS-BCM-0020 is a GigE board-level camera with a CS-mount. A board-level format still requires separate confirmation of the sensor package and optical stack.

Neither catalog entry supplied here specifies sensor cover-glass construction or a glass-free option. They are standard reference points for a selection discussion, not confirmed solutions to a cover-glass requirement.

Use the camera finder to narrow the interface, shutter and mounting requirements first. Then submit the optical requirement for confirmation. This avoids selecting an optically suitable configuration that cannot meet the acquisition or mechanical needs of the machine.

For broader integration tradeoffs, the board-level camera selection guide covers the decisions that remain even when the optical stack is settled.

Write a factory-configuration specification

A useful inquiry describes the required outcome and asks the manufacturer to define the configuration. Do not assume that a standard camera can be converted, or that a change applies across an entire camera family.

Include the following information:

• Inspection task: what must be detected or measured, and what currently prevents it.
• Optical arrangement: lens or objective, aperture, working geometry and any relay optics.
• Spectral requirement: operating wavelength band and relevant transmission or sensitivity criteria.
• Unwanted effect: focus shift, aberration, reflection, fringes or spectral attenuation.
• Requested stack: which layer must be absent or changed, and which protective layers may remain.
• Acceptance criteria: measurable image-quality and acquisition requirements.
• Integration constraints: interface, trigger behavior, mount, size and synchronization needs.

Request written confirmation of the sensor package construction, remaining optical layers and any changes to specifications or handling requirements. Ask how the factory configuration will be identified on the quotation, order and delivered documentation.

A custom configuration should have an unambiguous identifier. A verbal description such as “the standard camera, but without glass” is insufficient for purchasing, incoming inspection or later replacement.

If this is also a redesign of an existing machine, the camera replacement planning guide helps separate optical changes from mechanical and acquisition changes.

Resolve contamination and handling requirements early

A sensor cover provides a surface between contamination and more delicate internal structures. Without that barrier, particles or accidental contact may affect surfaces that are difficult or impossible to clean without damage.

Do not treat ordinary lens-cleaning practice as an approved procedure for an exposed sensor. Microlenses, color filters and surface coatings can require different handling. Ask the manufacturer to specify permitted cleaning methods and who is authorized to perform them.

Before ordering, determine:

• How the camera is protected during shipment and receiving inspection.
• What cleanliness controls are required during lens installation.
• Whether the optical assembly can remain closed after integration.
• How suspected contamination is diagnosed without touching the sensor.
• What service route applies if contamination occurs.

Keep the optical opening protected according to the supplied instructions until assembly. Plan the installation sequence so the sensor is not repeatedly exposed during unrelated mechanical work.

Also distinguish removable particles from pixel defects and illumination nonuniformity. A fixed mark in an image does not, by itself, prove that the package cover is responsible. Record flat-field images and compare them under controlled conditions before deciding on corrective action.

Validate a sample against the actual requirement

The acceptance test should reproduce the intended optical conditions, not merely demonstrate that the camera produces an image. Establish a baseline using the existing configuration whenever practical.

A focused validation sequence is:

1. Record the complete setup, including wavelength, aperture, focus method, exposure and image processing.
2. Capture dark and uniformly illuminated images to document offsets, nonuniformity and visible artifacts.
3. Image the real target at the intended operating settings.
4. Measure the requirement that motivated the change, such as reflection contrast or feature visibility.
5. Repeat after thermal stabilization and after the planned installation procedure.

For focus-sensitive work, compare the center and corners rather than selecting only the sharpest central region. Record any refocusing needed between configurations, so a focus offset is not mistaken for a sensitivity change.

For spectral comparisons, hold illumination and acquisition settings constant where possible. If settings must change, document them and explain how you normalized the comparison. Automatic exposure or gain can conceal differences between configurations.

Use the EMVA 1288 camera comparison guide when interpreting camera performance measurements. Standard performance data remains useful, but it may not describe a custom optical stack at your operating wavelength.

Define pass or fail before reviewing the sample images. For example, if the inspection requires distinguishing a feature from its background, specify the contrast or measurement repeatability needed by the application rather than judging appearance alone.

Check the order and recognize when standard glass is better

A standard covered sensor is usually the better starting point when the supposed limitation has not been isolated. It preserves the documented optical arrangement and avoids adding an exposed surface without a demonstrated benefit.

Retain the standard stack when a lens-spacing correction, appropriate filter or lighting adjustment meets the inspection requirement. Consider a factory-defined alternative when testing shows that the existing stack prevents acceptable performance and simpler changes do not resolve it.

Before placing the order, check that:

• The exact optical configuration appears in the written specification.
• The document distinguishes package cover, infrared-cut filter and front window.
• Any remaining optical surfaces are identified.
• Focus and image-quality implications have been reviewed with the optical design.
• Handling, cleaning and service instructions are documented.
• Sample testing meets the application's acceptance criteria.
• Replacement ordering and configuration traceability are defined.

Do not specify cameras without sensor cover glass merely because an application uses unusual wavelengths or demanding optics. Specify them when the measured requirement and confirmed optical construction justify the additional integration burden.

Start with the camera configurator to define the acquisition requirements. Then send the optical stack requirement and acceptance criteria through application support for confirmation before selecting a camera configuration.