NL1044332B1 - Method for improved scanning of a photographic emulsion - Google Patents
Method for improved scanning of a photographic emulsion Download PDFInfo
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- NL1044332B1 NL1044332B1 NL1044332A NL1044332A NL1044332B1 NL 1044332 B1 NL1044332 B1 NL 1044332B1 NL 1044332 A NL1044332 A NL 1044332A NL 1044332 A NL1044332 A NL 1044332A NL 1044332 B1 NL1044332 B1 NL 1044332B1
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- image
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- emulsion
- photographic emulsion
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- 239000000839 emulsion Substances 0.000 title claims abstract description 38
- 238000000034 method Methods 0.000 title claims abstract description 10
- 238000012545 processing Methods 0.000 claims abstract description 5
- 230000010287 polarization Effects 0.000 claims description 14
- 238000009826 distribution Methods 0.000 claims description 7
- 230000006872 improvement Effects 0.000 abstract description 4
- 238000007689 inspection Methods 0.000 abstract 1
- 238000005286 illumination Methods 0.000 description 17
- 238000003384 imaging method Methods 0.000 description 16
- 230000000739 chaotic effect Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 238000012935 Averaging Methods 0.000 description 3
- 230000010354 integration Effects 0.000 description 3
- 235000019988 mead Nutrition 0.000 description 3
- 238000000386 microscopy Methods 0.000 description 3
- 210000001747 pupil Anatomy 0.000 description 3
- 230000001360 synchronised effect Effects 0.000 description 3
- 244000153665 Ficus glomerata Species 0.000 description 2
- 235000012571 Ficus glomerata Nutrition 0.000 description 2
- 235000015125 Sterculia urens Nutrition 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 240000007594 Oryza sativa Species 0.000 description 1
- 235000007164 Oryza sativa Nutrition 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000010606 normalization Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/00795—Reading arrangements
- H04N1/00798—Circuits or arrangements for the control thereof, e.g. using a programmed control device or according to a measured quantity
- H04N1/00801—Circuits or arrangements for the control thereof, e.g. using a programmed control device or according to a measured quantity according to characteristics of the original
- H04N1/00806—According to type of the original, e.g. colour paper or transparency, or reading a plurality of different types of original
Abstract
Improved images from photographic emulsions are obtained by inspection of scattered light. Multiple image signals, have different levels of image noise but similar noise patterns. 5 Cancellation of image noise is, therefore, possible. In practical situations, scanning time is not increased. The improvements differ from existing methods in that they are of a fundamental nature that cannot be obtained by image processing. 10 1044332
Description
Title: Method for improved scanning of a photographic emul- sion
PRIOR ART
Explanation of the photographic imaging proces can be found in : "IMAGE SCIENCE" by J.C. Dainty and R. Shaw, ISBN 012008502
It describes the chaotic nature of photographic processes and its effect on film density, modulation transfer and filmgrain noise to a degree sufficient to understand the problem that the invention means to solve. -Three dimensional properties of photographic emulsions have been investigated by W.F.Berg as described in : " The photographic emulsion layer as a three-dimensional
Recording Medium"
APPLIED OPTICS December 1969 / Vol. 8 No 12.
It describes to what extent different layers of emulsions contribute to image formation. “The relation between different types of illumination and image contrast was first reported by A. Callier in: "Absorption und Diffusion des Lichtes in der entwickelten photographischen Platte"
Z. wiss. Photogr.Photophys.Photochem., vol 8,pp.257-272. -Further analysis of this callier effect, including its relevance for image noise, is given by: Chavel, P., and
Lowenthal, S. in : "Filmgrain Noise In partially coherent Imaging" .
SPIE Vol. 194 Application of Optical Coherence (1979)
They expres image contrast and noise in relation with angu- lar ranges of transillumination. This relationship leads to: "the callier surface of contrast". -Balancing of image noise versus image sharpness by adjust- ment of illumination has been described by "Terence William
Mead of Cintel International Limited" in :
US PAT 8,009,190 B2 (Aug 2011) -Manipulation of light after transmission through a film is described in: "Improvements relating to film scanners"
PO892939A2 (Mead) -Other methods for obtaining extra information from photo- graphic film are described by Trumpy in : "Optical detection of Dust and Scratches on Photographic
Film"
ACM Comput. Cult.Herit. 8,2, Article 7 (March 2015)
-Illumination over multiple angles has been described by:
Guoan Zheng et. Al. In : "Microscopy refocussing and dark field imaging by using a simple LED array"
OPTICS LETTERS Vol36, No36, No20 October 15, 2011/Vol. 30,
No 20 ~Also known is confocal drum scanning wherein single pixel values are successively generated and most of scattered light does not enter the lightpath. -Imaging of spatial frequencies beyond the diffraction lim- it of lenses has been demonstrated by M.G.L. Gustafsson In: " Surpassing the lateral resolution limit by a factor of two using structured illumination microscopy” .
Journal of Microscopy / Volume 198, Issue 2 p.82-87
Photographic emulsions contain randomly distributed parti- cles with light absorbing properties. When transilluminat- ed, this chaotic distribution of particles causes unwanted modulation, known as film grain noise. Traditionally, film grain noise is regarded as uncorrectable due to the lack of a fixed pattern for normalization. Although the particles that carry the image information, are chaotically distrib- uted and, therefore, cause film grain noise, they are fixed in a three dimensional constellation. Consequently, the way in which they transmit and scatter light is deterministic by nature and no fundamental law of physics forbids correc-
tion of film grain noise as caused by this chaotic distri- bution of particles.
The present invention aims to retrieve e.g. historic images stored in photographic emulsions with a considerable higher quality than is possible with prior art methods, resulting in fundamentally improved representations of those images.
To that end the present invention provides a method for scanning a photographic emulsion and retrieving an image stored therein and converting the retrieved image into a digital representation, the method comprising the steps of:
Transilluminating the photographic emulsion layer with light having a pre-determined angular distribution and dif- ferent modes of angular selection, spatial modulation, po- larization and or wavelength. -Detecting image signals according to one or more of said different modes of transillumination. -Storing two or more of said image signals in an image sen-
SOr Or processor. -Producing image signals that originate from, respectively, large and small relative amounts of light that has been scattered by the photographic emulsion. -Producung an improved image signal thereof.
The background of the invention will be explained with the aid of figures 1-6 and different embodiments will be ex- plained by figures 7-12 in which :
Fig.l shows light ray "L" that enters emulsion "E" and is partly transmitted and scattered.
Fig. 2 shows angular cones of transillumination.
Fig. 3 shows a callier surface of contrast "C". 5 Fig. 4 shows a surface of spatial bandwidth "B" versus F- number.
Fig. 5 shows Callier ridge "CR" and two more cross sec- tions.
Fig. 6 shows "CR" and "DL" indicating diffraction limita- tion.
Fig. 7 shows a lightpath of a system for limiting angular ranges.
Fig. 8 shows a lightpath for a system without moving parts.
Fig. 9 shows a system for spatial modulation.
Fig.l10 shows signals related to the system of fig.9
Fig.1ll shows a system having rotating polarization filters.
Fig.12 shows a system having circular polarization filters.
Emulsion "E" in fig 1 contains a stack of randomly distrib- uted particules of different sizes, shapes and positions.
Light ray "L" transverses this stack of particules partly in a streight line at an angle «, producing transmitted ray "T" and also partly deflected producing scattered light ray "S". Both rays "T" and "S" are subject to attenuation by the particules that carry image information. Scattered ray "Ss", may also be subject to multiple deflections, causing it to leave the emulsion with a lateral offset, causing un- sharpness. For different angles of incidence, the transmis- ion and scatter values vary to some degree due to the cha- otic structure. Likewise, transmision and scatter values also vary with the lateral position. As all pixels are, in- depentdently, subject to this proces, spatial image noise results. Therefore, both, spatial image noise and unsharp- ness depend on the conditions of transillumination.
Fig. 2 shows emulsion "E" being illuminated by a cone of light with angular range Aas which, after leaving the emul- sion, is accepted over an angular range Aap. Angular range
Aus can be as large as 180 degrees for diffuse illumina- tion, while angular range Aop depends on the imaging system that follows.
The accepted lightflux within angular range Aop contains scattered light to a degree expressed by the scatterratio.
The scatterratio depends on the type of emulsion, film- density and both angles Aas and Aap.
Variability of measured transmission values causes noise modulation "N" proportional to the inverse square root of the solid angular range (Aa)? of transillumination:
N ~ 1/Ac (1)
Where "Aa" is a general expression for linear angular range.
Callier was the first to investigate the effect of diffuse versus specular illumination on image contrast. This "Cal-
lier effect" has been quantified and related to film grain noise by Chavel and Lowenthal. This resulted in a surface of Contrast "C" as a function of both angular ranges Aas and Aap. The "callier surface", as shown in Fig.3, has a line of relative high contrast, here, indicated as Callier ridge "CR".
On line "CR", Aas and Aap are equal. This condition is, al- so known as having a coherence ratio of 1 or "matched illu- mination". The downhill shape of the callier surface is due to scattering of light by particules and depends on film- type, filmdensity, grain size, grain shape grain distribu- tion etc.
As scattering of light occurs in all directions, some scat- tered light also leaves the emulsion with a lateral offset before entering the imaging system. This reduces "image sharpness" or spatial bandwidth: "B".
The callier surface can be transformed into a meaningful representation of image quality by plotting spatial band- width "B" rather than contrast "C".
The relation between bandwidth "B" and contrast "C" follows from the Modulation Transform Function (MTF), in that con- trast "C" equals MTF at zero spatial frequency and band- width "B" equals the frequency at which the MTF has rolled off to a certain degree. Furthermore, we will plot the an- gular ranges in F-numbers as standardized in photography etc.
In accordance with expression "(1)", this logarithmic scale renders the horizontal coordinates into a value proportion- al to log (1/N). In this representation, of spatial band-
width "B", the area product "I" of its vertical and hori- zontal coördinates reads as:
I= B x~log(1/N) (2)
Equation (2) represents a relative amount of information density in the sense of Shannons information theory.
In this context, objective value "I" is meant to be equiva- lent with "image quality".
Fig.4 shows such a modified callier surface and two practi- cal operating conditions of transillumination.
The first operating point: "D/5,6" indicates diffuse illu- mination and an F/5,6 imaging lens. The second operating point "S/5,6" indicates specular illumination, also with an
F/5,6 imaging lens.
The line that connects these different illumination condi- tions represents the variation of diffuse versus specular illumination according to MEAD.
Fig. 5 shows the callier ridge "CR" of fig.4 as well as the cross sections through the vertical axis and operating points "D/5,6" and "S/5,6" respectively. Dotted lines de- lineate enclosed areas of information density "I".
Maximum image quality is obtained where such an area is maximal, in this example point "M" on "CR".
Fig. 6 shows Callier ridge "CR" together with curve "DL" which represents spatial bandwidth limitation by diffrac- tion. The spatial bandwidth of the system is, therefore, limited by both curves of which condition "M1" represents the condition for maximum information density.
Condition "M1" corresponds to the particular condition of transillumination whereby the maximum density of infor- mation can be obtained according to the state of the art.
As shown in figures 4,5 and 6 reduction of angular range of transillumination favours a high spatial bandwidth of the emulsion. However, the system bandwidth is also limitated by diffraction as indicated by curve "DL". This limits overall spatial bandwidth to where the bandwidth of the emulsion equals that of diffraction.
In Fig. 6 this condition is indicated as "M1".
Bandwidth extension beyond the diffraction limit of micro- scopes has been reported by M.G.L. Gustafsson and others by illumination with a pattern of a spatial frequency beyond the spatial pass band of a microscope objective.
Such "structured light illumination", mixes down high spa- tial frequency components, into the spatial pass band of an imaging lens.
Subsequent image processing transforms the resulting image signal into an extension of the spatial frequency spectrum.
The illuminating pattern is preferably produced by inter- ference of laserlight, for which no bandlimiting optics are needed.
A first improvement of image quality is obtained, by subse- quently transilluminating over a number of reduced differ- ent angular ranges and averaging their lightfluxes over the larger angular range that equals the sum of said reduced angular ranges. In this mode of angular limiting of light- 1044332 .
fluxes, an improved first image is obtained by lowering contributions of scattered light.
Fig.6 illustrates this by a horizontal shift from position "M1" to "M2", and the associated enlargment of enclosed ar- eas of information density.
In an opposite mode of angular selecting, the larger angu- lar range is illuminated except for the, subsequent, small- er angular ranges. This increases the contributions of scattered light on which a second image signal is based.
Successive averaging over the same large angular range fa- vours correlation of noise patterns. Therefore, arithmetic combination of the first and second image signals can pro- vide image signals having reduced image noise.
Fig. 7 shows, by way of example, an embodiment of the in- vention for creating different modes of angular selection, having multiple light sources that are synchronized with a scanning disk "SD" of the Nipkov type in the pupil plane of the imaging lens.
Here, the programmable lightsource "PL", subsequentially, illuminates different angular cones of lightflux, via con- densor "Co" on emulsion "Em". Imaging lenses transfer imag- es that are contained in emulsion Em onto the image sensor.
Scanning disc "SD", is meant for rotation in the pupil plane of the imaging lens. Here, openings in "SD", corre- spond to reduced angular ranges that the programmable lightsource "PL", illuminates according to the mode of an- gular selection as chosen.
For some conditions, the polarity of the noise pattern re- verses at a high scatterratio. In such cases, weighed addi-
tion of lightfluxes from different angular selections re- duces image noise when integrated by the image sensor.
Fig.8 shows a system for producing different modes of angu- lar selecting, not having moving parts. Here, multiple im- age sensors, each, receive light exclusively from a single, angular range. Tot this end, mirrors in the pupil plane re- flect small angular ranges of light to respective image sensors.
Fig. 9 shows a system that produces different modes of spa- tial modulation by illuminating the emulsion with a spatial pattern of a slightly lower frequency than the spatial bandwidth limitation of the imaging system. To this end, patterned lightsources "A" and "B" are successively, imaged on emulsion "Em" through imaging lens "Ll". The patterns in "A" and "B" are of opposite polarity. Spatially modulated images on "Em" are further imaged by imaging lens "L2" onto the image sensor that produces image signals as shown in fig. 10. Synchronized demodulation by the image processor separates modulated from average signal. As light, that has been scattered by the emulsion, contributes more to the av- erage signal and less to the modulation, signals relating to different scatter ratios are obtained.
Fig 10 shows how alternating "A" and "B" frames provide signals from which unwanted components are cancelled.
In this embodiment, alternation between "A" and "B" frames are obtained by slightly shifting the modulating lightpat- tern. Furthermore, selection of planes of best focus within the film provides 3-dimensional information if so wanted.
Another system is based on polarized illumination together with crossed polarization of light that leaves the emul- sion. This increases the scatterratio. Similarly, parallel polarization decreases the scatterratio.
As each angle of polarization comes with unrelated image noise, all or almost all angles of polarization are repre- sented for noise reduction by averaging.
Fig. 11 shows, by way of example, an embodiment based on polarized illumination by a lightsource and condensor lens "Co" that illuminates emulsion "Em" which is further imaged by the imaging lens on an image sensor. "Ps" is a rotating disc with a polarization filter preceding the entrance side of the emulsion, while "Pp" is a rotating disc in the lightflux that leaves the emulsion and is synchronized to disk "Ps". One halve of disc "Pp" has its direction of po- larization parallel with filter "Ps" ; the other halve has it crossed. Electronic system "EL" modulates the intensity of the lightsource according to the position of disc "Ps", the position of disk "Pp" and the integration interval of the image sensor in order to create successive image sig- nals of different modes of polarization. All angles of po- larization are equally represented if the integration time of the image sensor equals a full number of rotations of the rotating disks.
Furthermore, circular polarization can be applied to modify scatterratios. For instance, a left handed circular polari- zation filter polarizes the illuminating light flux and a right handed circular polarization filter, on the other side of the emulsion, attenuates light that has not been scattered.
This increases the scatterratio and , similarly, an even- handed filter decreases the scatterratio. Because of rota- tional symmetry, there is no need, here, for rotating the filters.
This type of modification of scatterratios by circular po- larization is easily, but not necessarily, combined with a system based on angular selecting.
An embodiment enabling such a combination is shown in fig.12 in which the system of fig. 7 is extended with left handed polarization filter "LH pol" in the illumination path and filters "LH" and "RH" on the scanning disc. Elec- tronic system "EL" selects successive modes of collimation and/or polarization in synchronism with the integration in- terval of the image sensor and modulates the lightsource for obtaining adequate signal levels.
As described by Dainty and Shaw, the relative amount of scattered light by an emulsion depends on the wavelength of illuminating light. Therefore, transilluminating with light of slightly different wavelength provide image signals that relate to slightly different scatter ratios. Substraction of two of these signals, therefore, produces a modified im- age signal that, largely, originates from scattered light.
According to the invention, the improvements it provides can be further increased in that illumination with struc- tured light and means for subsequent image processing ex- tend the spatial frequency range of the system towards that of the emulsion. In Fig.6 this would be expressed as a ver- tical extension of the information area enclosed by "M2".
Multiple systems according to the invention can produce im- age signals that are determined by different scatterratios and are suitable for combined processing and creating one or more improved image signals thereof.
Such production or calculation of other image signals is supposed to be part of the invention.
Claims (3)
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL1044332A NL1044332B1 (en) | 2022-05-17 | 2022-05-17 | Method for improved scanning of a photographic emulsion |
| PCT/NL2023/050279 WO2023224482A1 (en) | 2022-05-17 | 2023-05-17 | Method for improved scanning of a photographic emulsion |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL1044332A NL1044332B1 (en) | 2022-05-17 | 2022-05-17 | Method for improved scanning of a photographic emulsion |
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| Publication Number | Publication Date |
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| NL1044332B1 true NL1044332B1 (en) | 2023-11-24 |
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| NL1044332A NL1044332B1 (en) | 2022-05-17 | 2022-05-17 | Method for improved scanning of a photographic emulsion |
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| NL (1) | NL1044332B1 (en) |
| WO (1) | WO2023224482A1 (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030197901A1 (en) * | 2002-04-22 | 2003-10-23 | Pentax Corporation | Film scanner |
| US20050219518A1 (en) * | 2002-09-30 | 2005-10-06 | Doron Korngut | Dark field inspection system |
| US20070263226A1 (en) * | 2006-05-15 | 2007-11-15 | Eastman Kodak Company | Tissue imaging system |
| US8009190B2 (en) | 2005-09-06 | 2011-08-30 | Cintel International Limited | Optical scatter correction for film scanners |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2343077A (en) | 1998-08-21 | 2000-04-26 | Cintel Int Ltd | Film scanner using a diffuser to reduce visibility of imperfections on film surface |
-
2022
- 2022-05-17 NL NL1044332A patent/NL1044332B1/en active
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2023
- 2023-05-17 WO PCT/NL2023/050279 patent/WO2023224482A1/en unknown
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030197901A1 (en) * | 2002-04-22 | 2003-10-23 | Pentax Corporation | Film scanner |
| US20050219518A1 (en) * | 2002-09-30 | 2005-10-06 | Doron Korngut | Dark field inspection system |
| US8009190B2 (en) | 2005-09-06 | 2011-08-30 | Cintel International Limited | Optical scatter correction for film scanners |
| US20070263226A1 (en) * | 2006-05-15 | 2007-11-15 | Eastman Kodak Company | Tissue imaging system |
Non-Patent Citations (6)
| Title |
|---|
| A. CALLIER: "Absorption und Diffusion des Lichtes in der entwickelten photographischen Platte", PHOTOGR.PHOTOPHYS.PHOTOCHEM., vol. 8, pages 257 - 272 |
| GUOAN ZHENG: "Microscopy refocussing and dark field imaging by using a simple LED array", OPTICS LETTERS, vol. 36, no. 36, 15 October 2011 (2011-10-15) |
| LOWENTHAL, S.: "Filmgrain Noise In partially coherent Imaging", APPLICATION OF OPTICAL COHERENCE, vol. 194, 1979 |
| M.G.L. GUSTAFSSON: "Surpassing the lateral resolution limit by a factor of two using structured illumination microscopy", JOURNAL OF MICROSCOPY, vol. 198, pages 82 - 87, XP008083176, DOI: 10.1046/j.1365-2818.2000.00710.x |
| TRUMPY: "Optical detection of Dust and Scratches on Photographic Film", ACM COMPUT. CULT.HERIT., vol. 8, no. 2, March 2015 (2015-03-01), XP058066216, DOI: 10.1145/2597894 |
| W.F.BERG: "The photographic emulsion layer as a three-dimensional Recording Medium", APPLIED OPTICS, vol. 8, no. 12, December 1969 (1969-12-01) |
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| WO2023224482A1 (en) | 2023-11-23 |
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