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Resolution Test Targets![]()
R1DS1N Ø1" 1951 R1L3S6P Variable Line Grating Target R1L1S1P Combined Resolution R3L3S1N Negative 1951 USAF Target R1L1S2P Sector Star Target R2L2S1P1 Positive, High-Frequency Related Items ![]() Please Wait
Features
Resolution test targets are typically used to measure the resolution of an imaging system. They consist of reference line patterns with well-defined thicknesses and spacings and are designed to be placed in the same plane as the object being imaged. By identifying the largest set of non-distinguishable lines, one determines the resolving power of a given system. Thorlabs offers resolution test targets with 1951 USAF, NBS 1952, and NBS 1963A patterns. Targets are also available with sector star (also known as Siemens star) patterns, a variable line grating, or a combination of patterns for resolution and distortion testing. For more information on each pattern, see the Resolution Targets tab. Many of our resolution test targets are available with positive and negative patterns. The positive targets consist of low-reflectivity, vacuum-sputtered chrome patterns plated on clear substrates and are useful for front-lit and general applications. The negative targets use the same chrome coating to cover the substrates, leaving the patterns clear, and work well in back-lit and highly illuminated applications. Each pattern is manufactured using photolithography, allowing for edge features to be resolved down to approximately 1 µm. Mounting Photolithographic Target Manufacturing Birefringent Target Manufacturing Thorlabs also offers a complete line of reticles for superimposing a reference pattern onto an object.
![]() Click to Enlarge Line pairs help measure how well a camera can distinguish two objects from one another. Imaging ResolutionThe resolution of an imaging system is often specified in line pairs per millimeter (lp/mm), where a line pair is one light line and one dark line. This value represents the smallest distance between two objects that can be registered by the system; a higher value in lp/mm means the distance between each pair of lines is smaller. The diagram to the right illustrates the resolution limit of a system. The line pair imaged by the camera on the left cannot be resolved; the two lines are registered by adjacent pixels on the camera sensor, causing them to appear as a single object. In contrast, the line pair on the right has a greater spacing, and thus can be resolved by the system. The sections below describe the line patterns found on the resolution test targets sold on this page. 1951 USAF Targets
These resolution targets have a series of horizontal and vertical lines that are used to determine the resolution of an imaging system. A set of six elements (horizontal and vertical line pairs) are in one group, and ten groups compose the resolution chart. The image below shows Elements 2 and 3 of Group -2 on a resolution target. With line sets of three, these targets offer the advantage of an increased ability to recognize spurious resolution. Spurious resolution occurs when a set of lines is sufficiently blurred such that the overlap appears to form inverted, more distinct lines. This can cause a misreading of the resolution of the optical system, since it will appear that the lines are distinguishable. Spurious resolution also results in the appearance of one less line than exists in the line set. Since the difference between three lines and two is more easily noticed than the difference between five lines and four, for example, it is easier to recognize the occurrence of spurious resolution in targets with sets of only three lines. The spacing between the lines in each element is equal to the thickness of the line itself. When the target is imaged, the resolution of an imaging system can be determined by viewing the clarity of the horizontal and vertical lines. The largest set of non-distinguishable horizontal and vertical lines determines the resolving power of the imaging system. The chart below lists the number of line pairs per millimeter for a given element within a group based on the equation below. With our resolution targets, the maximum resolution is 228.0 line pairs per millimeter, which equates to roughly 4.4 µm per line pair. The 3" x 3" targets feature ten groups from -2 to +7; the 3" x 1" wheel pattern versions feature 9 targets, each with groups +2 to +7; the 18 mm x 18 mm (0.71" x 0.71") combined targets feature six groups from +2 to +7; and the Ø1" targets feature six groups, from +2 to +7. ![]() Example Line Sets
![]() Click to Enlarge Close Up of the R3L3S6P NBS 1952 Target NBS 1952 Targets
NBS 1952 Targets have sets of three vertical lines and sets of three horizontal lines. Each line and the space between it and the next line can be thought of as a line pair or a cycle. The resolution that each target is able to test is given by the frequency of line pairs in line pairs/mm (lp/mm). A list of every frequency available between our two NBS 1952 targets is given in the table below, along with the corresponding line widths. These targets offer two main advantages: the minimization of spurious resolution and the feasibility of one-pass scanning. Spurious resolution occurs when a set of lines is sufficiently blurred such that the overlap appears to form inverted, more distinct lines. This can cause a misreading of the resolution of the optical system, since it will appear that the lines are distinguishable. Spurious resolution also results in the appearance of one less line than exists in the line set. Since the difference between three lines and two is more easily noticed than the difference between five lines and four, for example, it is easier to recognize the occurrence of spurious resolution in targets with sets of only three lines. The advantage of one-pass scanning is made possible by the arrangement of the line sets on these targets. The horizontal and vertical line sets are arranged in an identical fashion, with identical frequencies, such that the target is symmetric across a diagonal line from the upper left to the lower right. If one scans from left to right or from top to bottom on the target, the frequency of the lines will increase until the center is reached and then decrease to the opposite edge. Whether done horizontally or vertically, this single pass across the full pattern covers each frequency available on the target. Thus, movement in only one direction is required to determine the resolution of an optical system.
![]() Click to Enlarge Microscope Image of R2L2S1N Negative Test Target NBS 1963A Targets
NBS 1963A Targets have line sets of five vertical and five horizontal lines. Each line and the space between it and the next line can be thought of as a line pair or a cycle. The resolution that each target is able to test is given by the frequency of the cycles in cycles/mm. On Thorlabs' NBS 1963A targets, each line set is labeled with its frequency. By determining the smallest lines that are distinguishable (highest cycles/mm), you can determine the resolution of an imaging system. Our standard NBS 1963A targets offer 26 line sets with resolutions scaled from 1.0 cycles/mm to 18.0 cycles/mm. For more rigorous resolution testing, our high-frequency NBS 1963A targets have 48 line sets with frequencies from 1.0 cycles/mm to 228 cycles/mm, and our R1L3S5P combined resolution and distortion test target has 35 line sets with frequencies from 4.5 cycles/mm to 228 cycles/mm. The size of each cycle is simply the reciprocal of the frequency and is given for all available frequencies in the table below. For the individual line width, divide the cycle size in half.
![]() Click to Enlarge Close Up of the R1L1S3P Sector Star Pattern Sector Star TargetsSector star targets, also known as Siemens star targets, consist of a number of dark bars that increase in thickness as they radiate out from a shared center. The blank spaces between the bars can themselves be thought of as light bars, and they are designed to be the same thickness as the dark bars at any given radial distance. Theoretically, the bars meet only at the exact middle point of the target. Some sector star targets, including all those sold on this page, have a blank center circle that cuts the bars off before they touch. However, depending on the resolution of the optical system through which the targets are viewed, the bars will appear to touch at some distance from the center. By measuring this distance, the user is able to define the resolution of the optical system. To calculate the resolution at any given radial distance from the center of the sector star, start by calculating the thickness of a line pair, or one dark bar and one light bar, at that radius. This can be done using the formula for the chord length, given below, where r is the radial distance from the center. The angle Θ is the number of degrees covered by one pair of light and dark bars and is equal to 360° divided by the total number of bars. Once the thickness of the line pair is calculated, the resolution is the reciprocal of the thickness. Thorlabs offers two dedicated sector star targets (R1L1S2P and R1L1S3P) and three targets that include sector stars along with other patterns (R1L3S5P, R1L1S1P, and R1L1S1N). The table below summarizes the sector star pattern on each target.
![]() Click to Enlarge Close Up of R1L3S6P Variable Line Grating Pattern Variable Line GratingsLine gratings consist of dark, parallel bars with widths that are equal to the distance between them. In any line grating, one dark bar and one blank space compose a line pair. The resolution of an optical system is dependent on its ability to distinguish adjacent line pairs. Thus, the grating resolution is defined by the number of line pairs in a given amount of space and is typically given in line pairs per millimeter (lp/mm). A variable line grating has some number of grating sections, which increase or decrease in resolution as you move from one to the next. By identifying the highest resolution line grating that an optical system is able to resolve, the user determines the resolution of the system. Thorlabs offers a variable line grating target with a range of resolutions from 1.25 lp/mm to 250 lp/mm. The table below gives the included resolutions along with a conversion of the line pair size.
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Thorlabs offers positive and negative Ø1" (Ø25.4 mm) resolution test targets that are made by plating low-reflectivity, vacuum-sputtered chrome on a soda lime glass substrate. These targets have 6 groups (+2 to +7) with 6 elements, offering a maximum resolution of 228.0 line pairs (one light line and one dark line) per millimeter. For more information on the 1951 USAF pattern, please see the Resolution Targets tab above. Because these targets feature sets of three lines, they reduce the occurrence of spurious resolution and thus help prevent inaccurate resolution measurements. For more information on spurious resolution, please see the Resolution Targets tab. The R1DS1P positive target consists of a chrome pattern plated on to a clear substrate and is useful for front-lit and general applications. Alternatively, the R1DS1N negative target uses the same chrome coating to cover the substrate, leaving the pattern itself clear, and works well in back-lit and highly illuminated applications. ![]()
Thorlabs offers positive and negative 3" x 1" (76.2 mm x 25.4 mm) resolution test targets that are made by plating low-reflectivity, vacuum-sputtered chrome on a soda lime glass substrate. The 3" x 1" wheel pattern targets have 9 USAF 1951 targets, each with 6 groups (+2 to +7), offering a maximum resolution of 228.0 line pairs (one light line and one dark line) per millimeter. For more information on the 1951 USAF pattern, please see the Resolution Targets tab above. Because these targets feature sets of three lines, they reduce the occurrence of spurious resolution and thus help prevent inaccurate resolution measurements. For more information on spurious resolution, please see the Resolution Targets tab. The R3L1S4P positive target consists of a chrome pattern plated on to a clear substrate and is useful for front-lit and general applications. Alternatively, the R3L1S4N negative target uses the same chrome coating to cover the substrate, leaving the pattern itself clear, and works well in back-lit and highly illuminated applications. ![]()
Thorlabs offers positive and negative 3" x 3" (76.2 mm x 76.2 mm) resolution test targets that are made by plating chrome on a soda lime glass substrate. The 3" x 3" targets have 10 groups (-2 to +7) with 6 elements per group, offering a maximum resolution of 228.0 line pairs (one light line and one dark line) per millimeter. For more information on the 1951 USAF pattern, please see the Resolution Targets tab above. Because these targets feature sets of three lines, they reduce the occurrence of spurious resolution and thus help prevent inaccurate resolution measurements. For more information on spurious resolution, please see the Resolution Targets tab. The R3L3S1P positive target consists of a chrome pattern plated on to a clear substrate and is useful for front-lit and general applications. Alternatively, the R3L3S1N negative target uses the same chrome coating to cover the substrate, leaving the pattern itself clear, and works well in back-lit and highly illuminated applications. ![]()
Thorlabs' 3" x 1" (76.2 mm x 25.4 mm) NBS 1952 Resolution Target offers 48 sets of lines with 24 different frequencies ranging from 2.4 to 80 line pairs (one light line and one dark line) per millimeter (lp/mm), as listed in the table below. In the center of the NBS 1952 target is a crosshair with a length and width of 610 µm and two concentric circles with diameters of 250 µm and 500 µm. Because the line sets on this target are arranged such that every resolution can be viewed by traveling in only one direction (either horizontally or vertically) along the pattern, the resolution of an optical system can be determined with one pass. For more information about the NBS 1952 pattern, please see the Resolution Targets tab above. Because this target features sets of three lines, it reduces the occurrence of spurious resolution and thus helps prevent inaccurate resolution measurements. For more information on spurious resolution, please see the Resolution Targets tab. The pattern on this target is made from low-reflectivity, vacuum-sputtered chrome deposited on a 0.06" (1.5 mm) thick soda lime glass substrate to achieve an optical density of ≥3 at 430 nm. The dark pattern and clear substrate are useful for front-lit and general applications.
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Thorlabs' 3" x 3" (76.2 mm x 76.2 mm) NBS 1952 Resolution Target offers 48 sets of lines with 24 different frequencies ranging from 0.48 to 16 line pairs (one light line and one dark line) per millimeter (lp/mm), as listed in the table below. In the center of the NBS 1952 target is a crosshair with a length and width of 3100 µm and two concentric circles with diameters of 1250 µm and 2500 µm. Because the line sets on this target are arranged such that every resolution can be viewed by traveling in only one direction (either horizontally or vertically) along the pattern, the resolution of an optical system can be determined with one pass. For more information about the NBS 1952 pattern, please see the Resolution Targets tab above. Because this target features sets of three lines, it reduces the occurrence of spurious resolution and thus helps prevent inaccurate resolution measurements. For more information on spurious resolution, please see the Resolution Targets tab. The pattern on this target is made from low-reflectivity, vacuum-sputtered chrome deposited on a 0.06" (1.5 mm) thick soda lime glass substrate to achieve an optical density of ≥3 at 430 nm. The dark pattern and clear substrate are useful for front-lit and general applications.
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Thorlabs' 2" x 2" (50.8 mm x 50.8 mm) NBS 1963A resolution test targets offer 26 line sets with frequencies from 1 to 18 cycles/mm, corresponding to cycle sizes from 1.0 mm to 55.6 µm (see the table to the right and the Resolution Targets tab for more information). Each set of lines on the pattern contains five horizontal and five vertical lines and is labeled with the frequency of the lines in cycles/mm, as shown in the images to the right. The resolution of an optical system can be determined by identifying the highest frequency line set that the system is able to resolve. These resolution targets are offered in positive and negative versions. The R2L2S1P positive target consists of a chrome pattern plated on to a clear substrate and is useful for front-lit and general applications. Alternatively, the R2L2S1N negative target uses the same chrome coating to cover the substrate, leaving the pattern itself clear, and works well in back-lit and highly illuminated applications. ![]() ![]() Click for Details Line sets with frequencies of 32 and 29 cycles/mm on the R2L2S1N1 negative target. The enlarged image shows line sets of 7.1 through 228 cycles/mm. ![]() Click for Details Line sets with frequencies of 32 and 29 cycles/mm on the R2L2S1P1 positive target. The enlarged image shows line sets of 7.1 through 228 cycles/mm.
Thorlabs' 2" x 2" (50.8 mm x 50.8 mm) high-frequency NBS 1963A resolution test targets offer 48 line sets with frequencies from 1 to 228 cycles/mm, corresponding to cycle sizes from 1.0 mm to 4.4 µm (see the table below and the Resolution Targets tab for more information). Each set of lines on the pattern contains five horizontal and five vertical lines and is labeled with the frequency of the lines in cycles/mm, as shown in the images to the right. The resolution of an optical system can be determined by identifying the highest frequency line set that the system is able to resolve. These resolution targets are offered in positive and negative versions. The R2L2S1P1 positive target consists of a chrome pattern plated on to a clear substrate and is useful for front-lit and general applications. Alternatively, the R2L2S1N1 negative target uses the same chrome coating to cover the substrate, leaving the pattern itself clear, and works well in back-lit and highly illuminated applications.
![]() ![]() Click for Details This image depicts the pattern placement relative to the inscribed rectangles on the front of the test target. ![]() Click for Details Image of R2L2S1B as seen through two crossed wire grid polarizers. The enlarged image shows the positive pattern on the left and negative pattern on the right.
Thorlabs offers a birefringent 2" x 2" (50.8 mm x 50.8 mm) NBS 1963A resolution test target that is made by sandwiching a birefringent pattern between two N-BK7 glass substrates. The test pattern is only observable if the target is placed between a pair of crossed polarizers (see image to the right). The target is designed so that it can display both positive and negative patterns by adjusting the orientation of the crossed polarizers relative to the test target. If the cross polarizers are aligned with the sides of the glass covers, the positive image will be formed. If the cross polarizers are aligned at 45° to the sides of the glass covers, the negative image will be formed. Because of its polarization sensitivity, this resolution target is ideal for calibrating and testing the resolution of polarizing microscopes, microscopes with a Nomarski mode, polarization imaging systems, or Mueller Matrix polarimeters. This target has 26 sets of five horizontal and five vertical lines. Each set of lines is labeled with a number, which refers to the number of cycles per mm. With a maximum frequency of 18 cycles/mm, the smallest cycles are only 0.0556 mm. For more information, please see the Resolution Targets tab above. Since the pattern is only visible through crossed polarizers, the target is inscribed with two rectangles for reference. The image on the far right shows the pattern placement with respect to these inscribed rectangles.
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Thorlabs offers two 1" (25.4 mm) square targets with positive Sector star (also known as Siemens star) patterns. The R1L1S2P target has 36 bars over 360°. The resolution at the center circle of this target is 57.5 lp/mm. Alternatively, the R1L1S3P target has 72 bars over 360°, and the resolution at the center is 115 lp/mm. Both targets also have a Ø200 µm center circle and are useful for determining the resolution of an optical system by noting how close to the center of the pattern an optical system is able to resolve adjacent bars. For more information about sector star patterns, please see the Resolution Targets tab.
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The R1L3S6P Variable Line Grating Target offers 18 sections of line grating with resolutions ranging from 1.25 line pairs (one light line and one dark line) per millimeter (lp/mm) to 250 lp/mm. The table below lists of each available resolution. The resolution of an optical system can be measured by determining the highest resolution grating with lines that the system is able to resolve.
![]() ![]() Click to Enlarge Close Up of the Smaller Grid on the R3L3S5P Target with Labels Added (See Tables Below)
Thorlabs' 3" x 3" (76.2 mm x 76.2 mm) Concentric Circle and Crosshair Grid Target offers 289 individual grids, arranged in a larger, 2" x 2" grid of 17 rows and 17 columns. The smaller grids each have four concentric circle patterns and five crosshair patterns of varying sizes. The concentric circle and crosshair patterns on the smaller grids are labeled in the image to the right but not on the target itself. Each concentric circle pattern features seven different radii, while the crosshairs each have a single or a double cross. For details on the dimensions of these patterns, see the tables below. The pattern on this target is made from low-reflectivity, vacuum-sputtered chrome deposited on a 0.06" (1.5 mm) thick soda lime glass substrate to achieve an optical density of ≥3 at 430 nm. The dark pattern and clear substrate are useful for front-lit and general applications.
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Thorlabs offers positive and negative 18 mm x 18 mm x 1.5 mm combined resolution / distortion test targets that are made by plating vacuum-sputtered, low reflectivity chrome with an optical density of ≥3 at 430 nm on a soda lime glass substrate. They are ideal for calibration of imaging systems and microscope stages. The test targets include a 1951 USAF pattern (Groups 2 - 7), a sector star, concentric circles, grids (100 µm, 50 µm, and 10 µm), and Ronchi rulings (30 - 150 lp/mm). These targets are useful for testing resolution, field distortion, focus errors, and astigmatism. The USAF 1951 targets are useful for measuring imaging resolution. For more information, please see the Resolution Targets tab above. The grids can be used to measure image distortion, while the concentric circles are ideal for identifying focus errors, astigmatism, and other aberrations existing in an imaging system. The Ronchi rulings are excellent for evaluating resolution, field distortion, and parfocal stability. These resolution targets are offered in positive and negative versions. The R1L1S1P positive target consists of a chrome pattern plated on to a clear substrate and is useful for front-lit and general applications. Alternatively, the R1L1S1N negative target uses the same chrome coating to cover the substrate, leaving the pattern itself clear, and works well in back-lit and highly illuminated applications.
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Thorlabs offers positive 3" x 1" x 0.06" (76.2 mm x 25.4 mm x 1.5 mm) combined resolution / distortion test targets that are made by plating vacuum-sputtered, low reflectivity chrome with an optical density of ≥3 at 430 nm on a soda lime glass substrate. They are ideal for calibration of imaging systems and microscope stages. They are sized to fit in our MLS203P2 stage slide holder for use with our MLS203 microscope stages. The test targets include an NBS 1963A pattern, a sector (Siemens) star, concentric circles, grids, Ronchi rulings, and more (see table below). These targets are useful for testing resolution, field distortion, focus errors, and astigmatism. The NBS 1963A, sector star, and concentric circle targets are useful for measuring imaging resolution. For more information, please see the Resolution Targets tab above. The grids can be used to measure the distortion introduced by an imaging system. The Ronchi rulings are excellent for evaluating resolution, field distortion, and parfocal stability.
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