SU1381415A1 - Device for measuring photomaterial modulation transfer function - Google Patents

Abstract

The invention relates to photo and cinematography and allows to expand the range of analyzed spatial frequencies and to improve the accuracy and efficiency of measurements. As the test object 9, a transparent base is used with the image of 90 periodic gratings intersecting at an angle with a rectangular distribution coefficient. transmissions whose periods differ by no less than ten times. The light flux of the monochromatic source 3 is formed by the objective 7 of the first optical channel 4 into a beam of parallel rays focused by the objective 8 into the plane of the measurement slit 10. The rotary unit II sequentially scans the image spectrum of the test object 9. The second optical channel 5 containing the mirror 12 and compensating optical wedge 13, forms a reference beam of light, the intensity of which is harmonized according to the intensity of the signals image spectra of the test object 9. The signal processing unit 2 includes photodetectors 14, 15 connected via logarithmic converters 16, 17c with an adder 18. The output of the adder 18 through divider 19, the anti-log converter 20 is connected to a recording device 21. 4 silt (L SA as ate L a Fi

Description

The invention relates to the field of cinematography and photography and can be used to determine one of the main structural-sharp characteristics of photographic materials, the modulation transfer function.

The purpose of the invention is to expand the range of the analyzed spatial frequencies and to improve the accuracy and efficiency of measurements of the transfer function of the modulation of photographic materials.

FIG. 1 is a schematic diagram of the proposed device; FIGS. 2 and 3 show the known and proposed test object, respectively; in fig. 4 - plots of FPM of high-resolution photographic material, obtained by measuring FPM on the known and proposed devices.

A device for measuring FPM (Fig.) Contains an optical system 1 and a signal processing unit 2. The optical system of the device consists of a light source 3, first and second optical channels 4 and 5, respectively. The first optical channel 4 includes a lighting slot 6, the first and second collimation lenses 7 and 8, respectively, the analyzed test object 9 with the image of a rectangular lattice, the measuring slit 10, can be made to rotate together with the lens 8 relative to the analyzed test object 9 by means of iruyuschego swing member 11. The second optical channel 5 includes a mirror 12 and a compensating optical wedge 13. The optical axis of the channels 4 and 5 are disposed opposite the photodetectors 14 and 5, respectively, whose input D the signal processing unit 2.

To maintain the position of the optical axis of the channel 4 relative to the photodetector 14, when the objective 8 and the measuring slit 10 are rotated, a light guide can be used, the first end surface of which retains the perpendicular position to the light beam coming from the measurement slit 10, and the second surface of the optical fiber retains the perpendicular position to the photodetector 14.

Block 2 also contains logarithmic converters 16 and 17, input 0

five

0

five

0

The ports of which are connected to the outputs of photodetectors 14 and 15, respectively. The outputs of the logarithmic converters 16 and 17 are connected to two inputs of the adder 18, and the output of the adder 18 through the divider 19 with the input of the anti-log converter 20, the output of the latter is connected to the input of the recording device 21,

The principle of operation of such devices is based on scanning the image spectrum of a test object imprinted on photographic material and subsequent mathematical processing of the signal. When measuring an MTF of photo materials by a diffractometric method, a one-dimensional grid with a rectangular transmittance distribution or a set of such grids with different periods P is usually used as a text object. The basic spatial often-i of the grid is measured in mm and is determined as the reciprocal of the period P of this lattice), 1 / Р. The spatial amplitude spectrum P () of a periodic lattice with dark 1 and bright dashes of equal width is determined by the expression

one

five

FO) 00 + -a ,, + -a,. ,, ... 2KTT (21.0, 1)

0

five

Where

, (g.O,

To the fundamental spatial frequency of the first harmonic; amplitude of zero order and signal at spatial frequency l (2K + 1),; 0,1,2; ...

The signal intensity 1 (2k + 0l) measured by the photodetector of the diffractometric installation at a given spatial frequency (2K + 1) -0 |, is proportional to the square of the amplitude -) V, therefore the modulation transfer function T (h) is determined by the intensity of the signals 1 (2к4 |) measured for discrete values of the spectrum of a periodic lattice

-

but.

.1 1 (7K ..) 1

(

Zo

 (2K + 1)

 VO

(2)

9

Thus, when measuring the FPM of photographic materials on the indicated diffraction unit, the signal processing unit, consisting of a photodetector, amplifier, and plotter, must register (2K + 1) harmonic components of the spectrum of the photographic image of the grating. Moreover, as can be seen from expression (2), the signal intensity decreases inversely proportional to the square of the sequence number of the corresponding harmonic composition.

leyuyu (2K + 1). The reference spatial frequency, relative to which the normalization of MTF is carried out, of the analyzed photomaps is usually 2-5. To determine the FPM of a photo material on a periodic grating with such a reference spatial frequency, up to the boundary spatial frequency of the order of 500, 250-100 harmonic components must be measured. At the same time, with respect to the first harmonic, the intensity of the last measured harmonic decreases by 2.510 10 times. If it is necessary to measure the signal with a relative error of ± 1%, then the intensity range of the measured signal increases by two orders of magnitude, t. e. is 2.5 10 - 10.

A device for measuring FPM photographic materials works as follows.

The main optical channel 4 contains a source of monochromatic light 3, the light flux of which falls on the lighting slit 6 located in the focus of the first object 7 of the collimator. The second collimator lens 8 focuses the beam parallel to the lens 7 after the lens 7: Kh: x rays into the measuring plane D -: -, whether 10. Scanning swivel unit: 1 rotates the lens 8 and the slit 10 relative to the analyzed test object 9. Additional optical channel 5 generates a reference beam of light, relative to the intensity of luminescence, it is carried out the normalization of the intensities of the signals measured in the main optical channel: e 4 higher harmonic components

you t5

20 25 DL,

40

d

50

five

image spectra of the analyzed test object 9. The signals are normalized using an optical compensating wedge 13 by equalizing the intensities

g ofl

the reference beam I and the first harmonic component of the diffraction spectrum of the photographic image on-

lattice races, i.e. I 1 const.

When the lens 8 is rotated with the measuring slit 10 by the rotary device 1, the image spectrum is sequentially scanned and processed in block 2 of the analyzed signals.

The signal processing unit 2 calculates the quantities -Jl (I -Jl;) entering into expression (2) and performs a series of sequential operations. Photodetectors 14 and 15 of the measuring main and reference channels 4 and 5 convert light fluxes into electrical signals, the magnitude of which is proportional to ,, | and 1), const, respectively. The outputs of the photodetectors 14 and 15 are connected to the inputs of the logarithmic converters 16 and 17, which perform the logarithm operation. At the same time, logI signals (iKfOO Igl const, respectively, are formed at the output of the logarithmic converters 16 and 17. The outputs of the logarithmic converters are connected to the input of the adder 18, where the received signals are subtracted (algebraically summed)). At the output of the adder unit, a signal is generated

igif ,,,) - igi, igLiin o / i,

When processing logarithmic signals, the square root extraction operation required by expression (2) can be replaced by 1/2 multiplication operation, i.e. degree 1/2 can be removed from the logarithm sign. Therefore, in the proposed device, the output of the adder 18 is connected to the input of the divider 19. At the same time, at the output of the divider unit, a signal is generated

0.5 ,,,,, (7Kv, l-J, / Io7. The output of the divider 19 is connected to the input of the antilogarifier 20, at the output of which the desired signal is formed:

g I- 1

antilg lg I (,,, | o. / 1,0,

 .4,),, The use of logarid thermal converters in the proposed device allows significantly .i: iH r at their output the level of the measured signal and, with sag-1nm, distribute the measuring range of F1TM. to high spatial frequencies,

As was shown earlier, when measuring the FPM of photographic materials on a conventional diffractometric installation ps

periodic lattice with the main

„-I spatial frequency v. um

in the spatial frequency band of 5–500 mm and a permissible measurement error of ± 1%, the intensity range of the measured signal is i 0 °.

When using an equipment in such a large range, the level of the measured signal 10 only photodetectors and logarithms work. At the output of logarithmic converters, the range of signals is narrowed: i.e. within limits, i.e., i.e., decreases from several units. In the same range, the signal is at the output of the adder -6 1; T: .-,.,) о / -. ; At the output of the divider, the range of sig is -IT: halved

 4i (,,, o / I,.,

At the output of the antilog: prg lies in the;:;; range - 5

ten

FIG. 2 scheme gchchps: i 5K: ..; af. j device worlds with image -. dimensional periodic;:.: m: j -. c, g closer to the goose-s; cr /;,. r ;; i -, - sti to offer: n 0 ..;;: fig. 3 shows P1 ;. 1lg, r- T - vii ;. ni; -.: i i by the image of the two-dimensional pe; ie i:; . Offered by lla co-ne: ;;: s:; i,. . base with H5o5pa; "efiv - / r pci-i ,, Binging at an angle of 90 psr - x -T h-:, - lattice g pr mg ;; v-; ,; by dividing the coefficients.: - npui :: .- c to; / g; ..-, periods P and FM of which.;: -: ..;: not less than 10 ha, T.I ::,:. ; A grating with a period of - ... hl: -;, to determine the FPM fi goma i .p: -i; i i -n in the area of low run / run}; ; -:; .- frequencies, respegka with Peoc.:: ;;;; -,;

/ i 1C g ;; the highest spatial hl-;: g Prschcha-sasma is a two-dimensional world,; .-. ::; , :: sr1-1il :: 1 ek | ;) i-i mf Battle. CiieKvp,: uibHbie are coherent with both D- 1; Cr 1b ppos tt are osedelenno and

g

; Bc; utl 90.

; : nal; tz spectrum photographic image of the proposed two; the vniipbi epnoe ischtsevlut when scanning the spectrum:; y, x was ush, their 1 (2k-i) 9 and T ,,), - |) in two mutually perpendicular ; - the xy and x directions of the x and., and the modulation transfer function of the photographic material is calculated in accordance with the expression (2) in the low simple frequency region

T.v) T ()

-jliL -riljP

(3)

. .. ki; -; ri :) goofy frequencies

,,; to. . (four)

i4 (j

ij

 inventions

) to measure the function of modulation of photographic materials, t-: l-.: i iaioaei the first optical channel, o. -t g-l: 14 P from the point of monochromatic- .-. I v. .: TJ: ocwegnts; J ъ} H-th Shelly,

O.:; 6 jt KTI-s: B. its t-object with -: S, with:.; r i- and .; Pr to and: G oh f-o and recte,.; :; .iru: 01; e: h; la with gadgetry. -: f, face of si Ci: r.-iana,, /, and Г; -111Й receiver and register-:. -. pociously, with t. I li h a h) - i,; -: leK, h-: o, for the purpose of dil. ;: - .. G; g -; 2G) ..-- 1 we analyze, tx npoci- .. those :: s and novgpen: exact AND .- l, h changes,

 .I.-: R .:; - tccc;:. K,: r-rkzl

. /: (, d and logari: .mi. .., - -.: ;;; oi ..r ,;. r -; LDTS,

J: j; : with ... iifmi. if lly,,: rkch; r-logy logf-: -; - :. .; and, n, G o-1 b; oa sgga e geG s c o di yen

. ; . . , :: ь ..- О ГЦЛ

 L,:; t ;: And V npecf pa 3ot ir tely ccj

 -S; -:, p g / -1I SumME: With RYA,

i - J .-;:,.: .. - ;. j-is / v, VSH-: i -; i with Y; -; p.1s: -. : J:, /.:. Apif: oche: lOI o

; VS Brazo; - ,. ; -,:; -. v; the course of which is soy; .-: ;at}; : ;; - ::,, g 1 ГРС 1 Г Вог,

. - -. GG: BJ (L:) - H VP

713814158

a transparent base with an image of the coefficient distribution of peristals that intersect at an angle of 90 °, whose pegyody differs from one odic lattice with a rectangular no less than 10 times.

2

FIG.

l

.S

: ifd

B

at

.

Claims (1)

And and 'Tx': 'YYAIOLTT t VI' 7 1381415 8 de transparent base with the image of intersecting at an angle of 90 ° periodic gratings with a rectangular the distribution of transmittance, the periods of which differ by no less than 10 times. Figure 1 Figure 2. I381415