Diffuse Visual Transmission Density

1 Page 1 NIST Special Publication 250 NIST SP 250-99 Diffuse Visual Transmission Density Clarence J. Zarobila Robert E. Vest Maria E. Nadal This publication is available free of charge from: https://doi.org/10.6028/NIST.SP.250-99 Open at page → 2 Page 2 NIST Special Publication 250 NIST SP 250-99 Diffuse Visual Transmission Density Clarence J. Zarobila Robert E. Vest Maria E. Nadal Sensor Science Division Physical Measurement Laboratory This publication is available fre... Open at page → 3 Page 3 NIST SP 250-99 August 2022 Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended... Open at page → 4 Page 4 NIST SP 250-99 August 2022 i Abstract This document, SP250- 99, NIST Measurement Services: Diffuse Visual Transmission Density, describes the instrument used to measure diffuse visual transmission density of both x- ray... Open at page → 5 Page 5 NIST SP 250-99 August 2022 ii Table of Contents Introduction ......................................................................................................................... 1 Theory and Measurement Equations ..... Open at page → 6 Page 6 NIST SP 250-99 August 2022 iii Acknowledgments The text presented herein has been edited and revised from the original work of Edward A. Early, Thomas R. O’Brian, Robert D. Saunders, and Albert C. Parr in NIST Special Pu... Open at page → 7 Page 7 NIST SP 250-99 August 2022 1 Introduction Transmission density is an important physical property for exposed films in the fields of medicine, non- destructive testing, photography, and graphic arts. Standards for transmi... Open at page → 8 Page 8 NIST SP 250-99 August 2022 2 Overview Two radiant fluxes are important for determining transmission density. Following the nomenclature given in [5, 6], these fluxes are the aperture flux Φ j, which is the flux emerging... Open at page → 9 Page 9 NIST SP 250-99 August 2022 3 Fig. 1. Important Components of the Diffuse Transmittance Densiometer Measurement Equation Derivation The properties of the various components used in deriving the measurement equations are g... Open at page → 10 Page 10 NIST SP 250-99 August 2022 4 The differential radiant flux dΦ from the opal or the step to the collecting lens is given by d????????????(????????????,????????????,????????????)=????????????(????????????,????????????,????... Open at page → 11 Page 11 NIST SP 250-99 August 2022 5 ???????????? τ(????????????)= ???????????? j(????????????,????????????)∙ ????????????s (????????????,????????????) 1− ???????????? o (????????????)∙???????????? s (????????????) ∙????????????... Open at page → 12 Page 12 NIST SP 250-99 August 2022 6 ???????????? τ= ???????????? τ∙???????????? τ (19) for the transmitted flux. Re-expressing E q. (2) in terms of the aperture and transmitted fluxes, the transmission density is ???????????? Τ... Open at page → 13 Page 13 NIST SP 250-99 August 2022 7 integration in E q. (25) are 0 to κ, while for the total aperture and transmitted fluxes Φ Τ,j and Φ Τ,τ, respectively, the limits are 0 to π/2. The ratios of these fluxes are given by ??????... Open at page → 14 Page 14 NIST SP 250-99 August 2022 8 Description of the Instrument The instrument was designed and built to automatically measure the diffuse visual transmission density of film step tablets using the diffuse influx mode. The ma... Open at page → 15 Page 15 NIST SP 250-99 August 2022 9 The infrared filter assembly consists of aluminum plates for mounting to the lamp housing and the shutter, and an infrared filter. Infrared filtering is accomplished with a combination of wat... Open at page → 16 Page 16 NIST SP 250-99 August 2022 10 Film Transport System The film transport system picks up a film from a tray, positions the film to measure the transmission density of each step on the film, and drops the film in another tr... Open at page → 17 Page 17 NIST SP 250-99 August 2022 11 travel back down to the opal. The lenses, baffle, and filter are housed in a black- anodized aluminum cylinder. The 4 mm by 4 mm Si photodiode is contained in a package that provides both th... Open at page → 18 Page 18 NIST SP 250-99 August 2022 12 Fig. 5. Cross-Section of the Detector System The aperture stop of the optical system is the collecting lens, which defines an acceptance cone with a half-angle κ = 9.5° between it and the op... Open at page → 19 Page 19 NIST SP 250-99 August 2022 13 A schematic diagram showing all the components of the instrument and connections is shown in Fig. 6. A computer performs all the data acquisition and control . The GPIB interface communicate... Open at page → 20 Page 20 NIST SP 250-99 August 2022 14 solenoid valve s on the vacuum lines and the one on the exhaust line are also opened and closed using AC relays controlled by digital signals from the DI/O The gain on the photodiode amplifi... Open at page → 21 Page 21 NIST SP 250-99 August 2022 15 These standards specify both the geometrical and spectral conditions for this measurement. The characterization is detailed for the source and detector systems and for the step tablet films.... Open at page → 22 Page 22 NIST SP 250-99 August 2022 16 Fig. 8. Relative Flux Distributions components of reflection were included in the integrating sphere. The radiant flux at the detector port of the integrating sphere was measured with a Si p... Open at page → 23 Page 23 NIST SP 250-99 August 2022 17 Fig. 9. 6° - Hemispherical Reflectance of the Opal as a Function of Wavelength The diffusion coefficient d of the opal is specified to be greater than or equal to 0.9 [8]. The radiant flux f... Open at page → 24 Page 24 NIST SP 250-99 August 2022 18 Fig. 10. Normalized Signal from the Efflux of the Opal There are two methods for calculating the diffusion coefficient. The first is given in [ 7], ????????????= ∑????????????(????????????)... Open at page → 25 Page 25 NIST SP 250-99 August 2022 19 lenses is not included since it is constant with wavelength in the visible spectral region for BK-7 glass. The spectral responsivity of the Si photodiode was measured in the Spectral Compara... Open at page → 26 Page 26 NIST SP 250-99 August 2022 20 To use E q. (22) to calculate transmission density from the signals and gains, the linearity of the photodiode and the ratio of gains G τ/Gj must be determined accurately. The linearity of t... Open at page → 27 Page 27 NIST SP 250-99 August 2022 21 Table 3. Values of Successive Gain Ratios Gain Ratio Value Relative Standard Uncertainty G5/G4 10.00032 4.13 x 10 -6 G6/G5 10.00493 6.31 x 10 -5 G7/G6 10.00311 4.62 x 10 -5 G8/G7 10.00098 5.... Open at page → 28 Page 28 NIST SP 250-99 August 2022 22 Fig. 13. Reflectance and Transmittance of the Indicated Films Several other geometrical conditions are specified by [7] in addition to the diffusion coefficient of the opal. The half-angle o... Open at page → 29 Page 29 NIST SP 250-99 August 2022 23 Therefore, all that is required to center the opal in the transverse direction of each step is to determine the location of a reference position on each film. This is done by measuring the s... Open at page → 30 Page 30 NIST SP 250-99 August 2022 24 vacuum is applied to the film holder while it is released from the vacuum plate, which attaches the film to the holder. The holder is then raised and the process is repeated for the next ste... Open at page → 31 Page 31 NIST SP 250-99 August 2022 25 Uncertainties Each measurement of transmission density has an uncertainty associated with it. This section details the components of uncertainty, their evaluation, and the resulting uncertai... Open at page → 32 Page 32 NIST SP 250-99 August 2022 26 Note that the standard uncertainty of D T is proportional to the relative standard uncertainty of x. There are several components of uncertainty associated with calculating transmission dens... Open at page → 33 Page 33 NIST SP 250-99 August 2022 27 As mentioned in S ection 4, neither the opal reflectance nor the spectral product are in agreement with the standards specified in [5]. The uncertainties arising from these two components ar... Open at page → 34 Page 34 NIST SP 250-99 August 2022 28 Finally, the spectral product of the instrument S I ∙ VI is not S H ∙ VT, but approximately S H ∙ Vλ since the spectral response of the detector is nearly the photopic spectral luminous effi... Open at page → 35 Page 35 NIST SP 250-99 August 2022 29 Step non- uniformity A 4 0.003 Spectral Product B < < 0.001 b Combined Standard Uncertainty, u c 0.003 Expanded Uncertainty U (k = 2) 0.007 a Other sources of uncertainty including voltmeter... Open at page → 36 Page 36 NIST SP 250-99 August 2022 30 [12] National Institute of Standards and Technology (2019) Spectral Comparator Facilities. Available at /web/20220331175321/https://www.nist.gov/laboratories/tools- instruments/spectral-comp... Open at page → 37 Page 37 NIST SP 250-99 August 2022 31 Appendix A. Sample Report of Calibration SAMPLE REPORT OF CALIBRATION 38100C Diffuse Transmittance for One X-Ray Step Tablet Issued to: XXX Company Attn: Customer Name Customer Address Issue... Open at page → 38 Page 38 NIST SP 250-99 August 2022 32 measurement was 24 ºC, the ambient photometer temperature was 25 ºC, and the relative humidity during the measurement was 30 %. The transmission density, D Τ, is calculated from the ratios o... Open at page → 39 Page 39 NIST SP 250-99 August 2022 33 5 1.247 6 1.501 7 1.677 8 1.979 9 2.190 10 2.434 11 2.703 12 2.930 13 3.191 14 3.394 15 3.660 16 3.903 17 4.131 Table 2. Uncertainty contributions and expanded uncertainty (k = 2) of the tra... Open at page → 40 Page 40 NIST SP 250-99 August 2022 34 Combined Standard Uncertainty, u c 0.003 Expanded Uncertainty U (k = 2) 0.007 a Other sources of uncertainty including voltmeter accuracy, diffusion coefficient, and opal reflectance were de... 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