Calibration target USAF 1951

Overview
USAF 1951 Glass Slide Resolution Test Targets are supplied in positive (chrome pattern on clear background) or negative (clear pattern on chrome background) formats. Positive targets are recommended for microscope and magnifier quality control; negative targets suit collimators, projection systems and other back-lit test setups. Each target is boxed and includes a resolution value chart. Targets conform to MIL-S-150A.

Key Features

• Positive and negative chrome patterns on float glass
• Two common sizes: 2×2 in and 3×3 in (other sizes on request)
• Each target boxed and supplied with resolution value chart
• High-resolution versions available (down to 645 lp/mm)

Number of Line Pairs / mm (USAF 1951)
Element | Group -2 | -1 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
1 | 0.250 | 0.500 | 1.00 | 2.00 | 4.00 | 8.00 | 16.00 | 32.0 | 64.0 | 128.0 | 256.0 | 512.0
2 | 0.280 | 0.561 | 1.12 | 2.24 | 4.49 | 8.98 | 17.95 | 36.0 | 71.8 | 144.0 | 287.0 | 575.0
3 | 0.315 | 0.630 | 1.26 | 2.52 | 5.04 | 10.10 | 20.16 | 40.3 | 80.6 | 161.0 | 323.0 | 645.0
4 | 0.353 | 0.707 | 1.41 | 2.83 | 5.66 | 11.30 | 22.62 | 45.3 | 90.5 | 181.0 | 362.0 | —
5 | 0.397 | 0.793 | 1.59 | 3.17 | 6.35 | 12.70 | 25.39 | 50.8 | 102.0 | 203.0 | 406.0 | —
6 | 0.445 | 0.891 | 1.78 | 3.56 | 7.13 | 14.30 | 28.50 | 57.0 | 114.0 | 228.0 | 456.0 | —

Positive vs Negative Targets

• Positive target: dark (chrome) bars on a bright/clear background — suited to front-lit or general lighting and microscope calibration.
• Negative target: bright (clear) bars on a chrome/dark background — optimised for back-lit, projection and high-contrast testing.
• Selection guide: choose pattern based on illumination method and detector contrast requirements.

Technical Specifications

• Substrate: Float glass
• Edges: Beveled
• Flatness: ≤0.00254 mm
• Optical density (OD average): ≥3.0
• Surface quality: 20-10
• Conformance: MIL-S-150A
• Packaging: Each target boxed with resolution value chart