Centring and symmetry
Nested square frames make offsets between the image centre and the pattern centre visible.
Concentric Square Test Targets
Check scale, centre and field geometry.
Nested-square glass targets for pixel-to-length calibration, centring, alignment and qualitative distortion checks. Define square sizes, gaps, line widths and measurement method.
Product selection
What it is and what it does
A concentric-square target places several straight-edged squares around a common centre. Their known spans provide a two-dimensional length reference, while the shared edges and corners help align an optical axis or inspect field geometry. The target is a scale and alignment reference; it does not automatically replace a camera calibration board or a resolution chart.
When to choose it
Choose this family when the result you need is a physical scale, a repeatable centre or a check of edge geometry. Use a checkerboard or dot array when software must solve a full intrinsic and distortion model, and use USAF, NBS or Siemens patterns when the question is optical resolution.
Read a nested reference at several scales
Scale and geometry checks
Known side lengths can support local pixel-scale checks; unequal sides or curved edges require perspective and distortion to be considered separately.
Choose the frame dimensions and edge convention
| Choice | Selection basis |
|---|---|
| Nested sizes | Select side lengths and frame spacing for the required field and image magnification. |
| Measurement boundary | Define whether coordinates refer to line centres, inner edges or outer edges. They give different dimensions for a finite-width line. |
| Reference orientation | Use the intended plane and orientation. A tilted board changes apparent geometry even without lens distortion. |
Formats and pattern options
Concentric squares / primary view
76.2 mm plate
Primary 76.2 mm family view with nested frames around a shared centre. Confirm each nominal span from the drawing.
Concentric squares / alternate view
76.2 mm plate
Alternate view of the same concentric-square family; the image does not create a separate product type.
Concentric squares / dimensioned view
76.2 mm shown
Dimensioned view for configuration review. Use the drawing rather than the photograph as the controlling dimensional source.
Where this product is used
Nested frames show image centring, edge straightness and apparent geometry across the camera field.
Known frame spans establish local image scale at the microscope specimen plane.
Inspection and delivery
Inspect side lengths, frame spacing, straightness, corner geometry and concentricity over the active area. The report should state whether values are nominal or measured and whether dimensions refer to line centres, inner edges or outer edges.
The selected nested frames are supplied on glass with the stated edge convention, dimensions and reference centre.
Common questions
Can the square pattern identify orientation by itself?
No. A square has rotational symmetry. Add a datum mark or use the fixture orientation when a unique X/Y direction is required.
Selection notes
Concentric-square targets provide known nested outlines for scale, centre and geometric checks.
Specify frame dimensions, line width, shared centre and orientation. Distinguish perspective effects from lens distortion when reading the image.
Information for your inquiry
Frame dimensions, centre, line width, active area, substrate and imaging geometry.
Is one square image enough for full camera calibration?
A square image can check specific geometry. Full intrinsic and distortion calibration needs the observations and model required by the calibration method.