Karl Norris: A Pioneer in Optical Measurements and Near-Infrared Spectroscopy, Part II

Part II of this "Icons of Spectroscopy" series continues the story of Karl H. Norris by examining the depth and breadth of his scientific legacy. This article highlights Norris’ most influential publications, patents, and technical achievements that have left an enduring mark on the field of near-infrared spectroscopy. Beyond instrumentation and methods, Norris’ legacy is also defined by his role as a mentor, collaborator, and visionary who helped elevate NIR into a mainstream analytical tool used in pharmaceuticals, food science, clinical diagnostics, and industrial quality control. Through decades of research and global influence, Norris not only advanced analytical science but also built a community of scientists and engineers committed to pushing the boundaries of what NIR could achieve.

Foundational NIR Work

The following section summarizes Norris’ foundational NIR publications using their original scientific language and measurement units as reported in the respective research papers.

Karl H. Norris (Photo Courtesy of Reference [1])

Norris and Hart explored specific water absorption bands in the NIR region to evaluate moisture content in grains and seeds using spectrophotometry (9). The 1.94 μm (micrometers) band was identified as having minimal spectral interference in ground wheat samples for water measurements. Moisture levels in wheat, soybeans, flour, and bran were measured by analyzing transmittance differences between 1.94 and 2.08 μm after mixing the samples with carbon tetrachloride. The resulting optical density differences correlated well with standard moisture determinations, yielding calibration curves with standard deviations between 0.28% and 0.37% over a 0–20% moisture range. Additionally, the 0.97 μm band was used to assess moisture in whole peanuts, achieving accuracy within ±0.7%. The results support the feasibility of using direct spectrophotometric methods for moisture analysis in various solid biological materials (9).

In 1968 Ben-Gera and Norris reported the use of direct spectrophotometric methods to analyze the NIR absorption characteristics of thin meat emulsion samples. The observed spectra reflected both O-H and C-H stretching vibrations along with scattering effects. Specific optical density differences showed strong correlations with moisture and fat levels: the 1.80–1.725 µm range was linked to moisture, while the 1.725–1.65 µm range correlated with fat. The technique predicted moisture content with a ±1.4% error and fat content with a ±2.1% error. The findings highlight the potential of NIR spectroscopy for rapid moisture and fat analysis, while also noting challenges that remain for routine implementation (10). Note that one of the earliest applications of NIR spectroscopy for moisture determination in grains was also published by Ben-Gera and Norris in 1968 (11).

Hruschka and Norris modeled near-infrared reflectance spectra of ground wheat as linear combinations of spectra from known components, optimized using a least-squares approach (12). The resulting coefficients were correlated with protein and moisture content, and improvements were made by using multiple coefficients and substituting sample spectra for pure components. These refinements significantly reduced prediction errors, achieving a correlation (r) of 0.998 for protein with a standard error of 0.15%. The method’s performance was also evaluated under varying spectral conditions and sample characteristics, including particle size and noise (12).

Norris and Butler developed a specialized, high-sensitivity NIR spectrophotometer to record absorption spectra from a variety of biological samples with minimal sample preparation (13). This single-beam system featured a double-prism monochromator, tungsten light source, and end-window phototube, delivering high linearity across an optical density range of up to 8 AU. With low noise and precise measurement capabilities—even for samples with significant light scattering—it offered flexible scanning speeds across wavelengths from 200 to 1200 mμ (nanometers). The setup supported multiple sample types, including liquids, powders, homogenates, tissues, and solids, with custom mounting options to optimize measurement accuracy (13).

Norris, Barnes, Moore, and Shenk published an evaluation of NIR reflectance spectroscopy (1.4–2.4 µm) as a method for assessing the nutritional composition of 87 ground forage samples, including both temperate (such as alfalfa, and tall fescue) and tropical species (for example, bermudagrass) (14). Standard lab analyses measured protein, fiber, lignin, digestibility, and energy intake. Spectral data were transformed into a second-derivative form for statistical modeling using MLR. Predictions based on up to nine wavelength points showed strong correlations with lab results, especially for crude protein (r = 0.99) and fiber components. Validation using a test set confirmed the method’s accuracy, with resulting low prediction errors. The findings suggested that NIR reflectance offered a fast, reliable way to assess forage quality (14).

Williams, Norris, and Sobering reported that the Trebor GT-90 near-infrared transmission spectrometer (900–1050 nm) was designed to measure crude protein and moisture content in whole grains such as wheat and barley (15). It was capable of processing large sample sizes (150–250 g) with a completed measurement in about 45 seconds. Performance was assessed by comparing results to standard Kjeldahl protein and air-dry oven moisture methods, as well as to other widely used NIR reflectance instrument results. The instrument demonstrated adequate accuracy and precision for grain sorting and classification purposes. Additional tests examined how factors such as temperature, tempering, contaminants, grain size, and harvest year influenced measurements (15).

Norris wrote a definition for near-infrared reflectance spectroscopy (NIRS) in a foundational book published on the subject of NIR to measure forage quality (16). It was reported that NIR offers a rapid, non-destructive, and reliable way to analyze the chemical makeup of forages. The technique relies on the specific absorption features of key organic components, which influence diffuse reflectance and enable compositional assessment. This overall United States Department of Agriculture-Agricultural Research Service (USDA-ARS) handbook serves as an introduction to the development and application of NIRS in evaluating forage quality (16).

Norris recounts in the Early History of Near Infrared for Agricultural Applications, the foundational work that led to the development of near-infrared spectroscopy (NIRS) for evaluating agricultural products. His descriptive and historical article highlights key milestones, technical breakthroughs, and the initial challenges in applying NIRS to assess moisture, protein, and other components in various crops, including forages (17).

Kuenstner, Norris, and McCarthy used a modified NIRSystems Model 6500 spectrophotometer and collected visible and near-infrared transmittance spectra of analyzed blood to estimate hemoglobin levels (18). Despite minimal control over pathlength and temperature, hemoglobin was predicted with a standard error of 0.43 g/dL using a second-derivative spectral ratio. Calibration and validation were performed on separate patient sample sets, and the method showed high reproducibility with a variability of only 0.63%. The study highlights a fast and straightforward approach for measuring hemoglobin using diffuse transmittance NIR spectroscopy (18).

Throughout his career, Norris published extensively on the theory and application of NIR spectroscopy, often collaborating with researchers across disciplines. He contributed to numerous journal articles, book chapters, and technical reports, detailing both instrumental advancements and the computational techniques required for reliable spectral interpretation. His influence extended beyond research publications, as he also played a key editorial role in disseminating instrumental developments through professional journals and industry reports.

U.S. Patents Issued

Norris made notable contributions to applied optical sensing through several patents spanning food inspection, analytical instrumentation, and agricultural analysis. Early patents, such as US-2700321-A (19) and US-2833408-A (20), introduced optical methods for detecting blood in eggs and sorting them by color. Later work, including US-3877818-A (21) and US-4172902-A (22), applied photo-optical techniques to measure fat in meat and developed a stable natural pigment for food products. Norris also advanced spectroscopic instrumentation with patents like US-4997280-A (23) and US-6031608-A (25), improving signal accuracy and optical focus. His one NIR patent, US-5132538-A (24), demonstrated near-infrared reflectance for protein measurement in whole grains for a broader impact on agricultural quality assessment.

US Patent US-2700321-A, titled "Method and apparatus for detecting blood in eggs," issued on January 25, 1955, to inventors Albert W. Brant and Norris, describes a method and device for identifying the presence of blood in whole shell eggs. This system involves projecting a light beam rich in wavelengths between 12,600 and 14,000 angstroms through an egg and measuring the transmitted light to detect anomalies like blood spots. The technique enables non-destructive internal inspection of eggs using specific light properties to assess internal contents (19)

The US-2833408-A patent, titled "Egg separating machine," granted on May 6, 1958, to Norris and Albert W. Brant, outlines a machine designed to separate eggs based on color characteristics using optical sensing. The apparatus consists of a moving conveyor system equipped with trays and designated bins; as each egg’s color is optically analyzed, it is directed into a corresponding bin, allowing for efficient sorting and classification according to color properties (20).

Patent US-3877818-A, titled "Photo-optical method for determining fat content in meat," issued on April 15, 1975, to George F. Button and Norris, presents a photo-optical system for measuring the fat content in meat. Using incandescent light and an interference filter that operates at varying angles, the system captures specific wavelengths in the infrared range corresponding to fat absorption bands. A tilting mirror directs the light onto a detector, which converts the optical signal into an electronic readout indicating the fat percentage (21).

In US Patent 4172902-A, titled "Stable foods and beverages containing the anthocyanin, peonidin 3-(dicaffeylsophoroside)-5-glucoside," issued on October 30, 1979, Norris discloses a method for enhancing the visual appeal of foods and beverages using a natural anthocyanin-based colorant derived from the Heavenly Blue Morning Glory flower. The pigment, identified as peonidin 3-(dicaffeylsophoroside)-5-glucoside, maintains vibrant color stability across a wide pH range (2.0 to 8.0), offering an effective solution for natural product color formulation in consumables (22).

The invention in US-4997280-A, titled "Spectrophotometric instrument with rapid scanning distortion correction," awarded on March 5, 1991, to Norris, addresses signal distortion in rapid-scanning spectrophotometers. The system processes output from photodetectors by sampling and digitizing signal amplitudes, then applying a first derivative correction algorithm. This derivative is multiplied by a constant to offset distortion, and the result is added back to the original signal to improve the accuracy of intensity data during high-speed spectral scans (23).

In US-5132538-A, titled "Measuring percentage of protein in whole grain samples," granted on July 21, 1992, Norris presents a NIR spectroscopic method for determining protein content in whole grain kernels. The approach uses reflectance data from selected wavelengths below 1600 nm, with mathematical normalization and regression-based modeling to convert absorbance data into protein percentages. An alternate approach applies second-derivative spectroscopy for improved predictive accuracy using calibration coefficients from known samples (24).

The patent US-6031608-A, titled "Spectroscopic instrument with offset grating to improve focus", issued on February 29, 2000, to Kenneth P. Vonbargen and Norris, improves the focus quality in a scanning spectroscopic instrument by modifying the orientation of the spherical diffraction grating. The rotation axis is intentionally offset from the grating’s tangent center, enhancing focus uniformity across the scanned spectral field. Additionally, the grating's center of gravity is aligned with the pivot axis to optimize mechanical balance and spectral clarity (25).

At USDA, Karl Norris developed the first computerized near-infrared spectrophotometer (Photo Courtesy of Reference [2]).

Achievements, Awards, and Recognitions

Norris received numerous accolades for his innovation and impactful contributions to agricultural engineering, spectroscopy, and instrumentation development (Table I). His USDA honors included two Superior Service Awards (1955 and 1963), a Distinguished Service Award (1986), and induction into the Agricultural Research Service Science Hall of Fame (1989).

He was elected a Fellow of the American Society of Agricultural Engineers in 1967 and received its prestigious Cyrus Hall McCormick Medal in 1974. In 1980, he was elected to the National Academy of Engineering for his pioneering work in analytical instrumentation. His alma mater, Penn State, recognized him as an Outstanding Engineering Alumnus (1986) and an Alumni Fellow (1988) (3-8).

Additional honors included the Thomas Burr Osborne Medal from the American Association of Cereal Chemists (1986) and the Maurice F. Hasler Award from the Spectroscopy Society of Pittsburgh (1991). In 1995, the International Council for Near-Infrared Spectroscopy (ICNIRS) named him its first Honorary Fellow in recognition of his foundational role in the field. The New York Society for Applied Spectroscopy recognized him with the Gold Medal Award in 2001. The Eastern Analytical Symposium honored him with the Award for Outstanding Achievements in Near-Infrared Spectroscopy in 2001 (3-8).

Norris received widespread recognition for his contributions to analytical spectroscopy and instrumentation. These awards reflect the broad impact of his work across engineering, chemistry, and agricultural science communities.

Long-Term Influence and Legacy

The methodologies that Norris developed for spectral analysis remain fundamental to modern NIR spectroscopy. His work directly led to the adoption of NIR techniques in grain quality assessment, moisture determination, and compositional analysis of food and biological materials. The commercial deployment of NIR analyzers for agriculture, pharmaceuticals, and petrochemical applications can be traced back to his pioneering studies.

Beyond instrumentation, Norris’s emphasis on computational approaches to spectral data analysis foreshadowed the integration of chemometrics and ML in spectroscopy. His work laid the groundwork for multivariate calibration techniques that are now standard practice in quantitative spectroscopy.

Norris also played a vital role as a mentor and educator, guiding researchers and fostering international collaborations. His contributions to the NIR community continue to be honored through scientific awards and symposiums dedicated to advancements in the field.

Closing Comments

Karl Norris’s career exemplifies the transformative power of interdisciplinary research. By combining agricultural engineering, physics, and computational methods, he revolutionized analytical spectroscopy—particularly in near-infrared (NIR) techniques. His innovations improved agricultural quality control and paved the way for applications in pharmaceuticals, polymers, and other industries. Norris’s legacy endures in the widespread use of NIR spectroscopy as a vital tool for rapid, non-destructive analysis across scientific and industrial fields. As a mentor, researcher, and innovator, his lasting impact will continue to shape generations of scientists and engineers.

Table I: Karl Norris’ achievements, awards, and recognitions

References

(1) Photo courtesy of USDA Hall of Fame Page. Available at: https://www.ars.usda.gov/oc/hall-of-fame/browse-hall-of-fame (accessed 2025-04-09).

(2) Photo courtesy of USDA Agricultural Research Service Page. Available at: https://www.ars.usda.gov/oc/timeline/light (accessed 2025-04-09).

(3) Williams P. Karl H. Norris, the Father of Near-Infrared Spectroscopy. NIR news. 2019, 30 (7-8), 25–27. DOI: 10.1177/0960336019875883

(4) U.S. National Academy of Engineering, Karl H. Norris Page. Available at: https://www.nae.edu/260644/KARL-H-NORRIS-19212019 (accessed 2025-04-09).

(5) Dignity Memorial Karl H. Norris Obituary Page. Saturday, October 05, 2019. Available at: https://www.dignitymemorial.com/obituaries/alexandria-va/karl-norris-8782330 (accessed 2025-04-09).

(6) Beltsville News Page, September 09, 2019. Karl H. Norris, Obituary 2 Page. Available at: https://www.beltsvillenewstoday.com/post/2019/09/09/obituary-norris-karl-howard (accessed 2025-04-09).

(7) National Agricultural Library, U.S. Department of Agriculture Karl Norris Publications Archive Page. Karl H. Norris Papers, Collection Identifier: MS0490 (1948–2013). Available at: https://archivesspace.nal.usda.gov/repositories/4/resources/956 (accessed 2025-04-09).

(8) Beltsville Agricultural Research Center of the U.S. Department of Agriculture Karl Norris Search Page. Available at: https://search.usa.gov/search?affiliate=agriculturalresearchservicears&query=%22Karl+Norris%22 (accessed 2025-04-09).

(9) Norris, K. H.; Hart, J. R. Direct Spectrophotometric Determination of Moisture Content of Grain and Seeds. In Principles and Methods of Measuring Moisture Content in Liquids and Solids; Reinhold Publishing: New York, 1965; Vol. 4, pp 19–25. https://opg.optica.org/jnirs/viewmedia.cfm?uri=jnirs-4-1-23&seq=0 (accessed 2025-04-09).

(10) Ben-Gera, I.; Norris, K. H. Direct Spectrophotometric Determination of Fat and Moisture in Meat Products. J. Food Sci.1968, 33 (1), 64–67. DOI: 10.1111/j.1365-2621.1968.tb00885.x

(11) Ben-Gera, I.; Norris, K. H. Determination of Moisture Content in Soyabeans by Direct Spectrophotometry. Israel Journal of Agricultural Research 1968, 18 (3), 125–32 ref. Bibl. 15, CABI Record Number: 19691701115. https://www.cabidigitallibrary.org/doi/full/10.5555/19691701115(accessed 2025-04-09).

(12) Hruschka, W. R.; Norris, K. H. Least-Squares Curve Fitting of Near Infrared Spectra Predicts Protein and Moisture Content of Ground Wheat. Appl. Spectrosc, 1982, 36 (3), 261–265. DOI: 10.1366/0003702824638458

(13) Norris, K. H.; Butler, W. L. Techniques for Obtaining Absorption Spectra on Intact Biological Samples. IRE Trans. Bio-Med. Electron. 1961, 8 (3), 153–157. DOI: 10.1109/TBMEL.1961.4322890

(14)Norris, K. H.; Barnes, R. F.; Moore, J. E.; Shenk, J. S. Predicting Forage Quality by Infrared Reflectance Spectroscopy. J. Anim. Sci. 1976, 43 (4), 889–897. DOI: 10.2527/jas1976.434889x

(15) Williams, P.C., Norris, K.H. and Sobering, D.C., 1985. Determination of protein and moisture in wheat and barley by near-infrared transmission. J. Agric. Food Chem. 1985, 33 (2), 239–244. DOI: 10.1021/jf00062a021

(16) Norris, K. H. Definition of NIRS Analysis. In Near Infrared Reflectance Spectroscopy (NIRS): Analysis of Forage Quality; Marten, G. C., Ed.; USDA-ARS Agriculture Handbook No. 643; U.S. Department of Agriculture: Washington, DC, 1989; p 6. https://www.scribd.com/document/227659404/CAT89919964PDF-1 (accessed 2025-04-09).

(17) Norris, K. H. Early History of Near Infrared for Agricultural Applications. NIR News 1992, 3 (1), 12–13. DOI: 10.1255/nirn.105

(18) Kuenstner, J. T.; Norris, K. H.; McCarthy, W. F. Measurement of Hemoglobin in Unlysed Blood by Near-Infrared Spectroscopy. Appl. Spectrosc. 1994, 48 (4), 484–488. DOI: 10.1366/000370294775269036

Patent References

(19) Brant, A. W.; Norris, K. H. Method and Apparatus for Detecting Blood in Eggs. U.S. Patent 2,700,321, January 25, 1955.

(20) Norris, K. H.; Brant, A. W. Egg Separating Machine. U.S. Patent 2,833,408, May 6, 1958.

(21) Button, G. F.; Norris, K. H. Photo-Optical Method for Determining Fat Content in Meat. U.S. Patent 3,877,818, April 15, 1975.

(22) Norris, K. H. Stable Foods and Beverages Containing the Anthocyanin, Peonidin 3-(Dicaffeylsophoroside)-5-Glucoside. U.S. Patent 4,172,902, October 30, 1979.

(23) Norris, K. H. Spectrophotometric Instrument with Rapid Scanning Distortion Correction. U.S. Patent 4,997,280, March 5, 1991.

(24) Norris, K. H. Measuring Percentage of Protein in Whole Grain Samples. U.S. Patent 5,132,538, July 21, 1992.

(25) Vonbargen, K. P.; Norris, K. H. Spectroscopic Instrument with Offset Grating to Improve Focus. U.S. Patent 6,031,608, February 29, 2000.