I|||||||||||||IllIlllllllll||||||||||||||||||||||||||||||||||||||||||||||||
`US005592256A
`
`United States Patent
`
`1191
`
`Muramatsu
`
`[11] Patent Number:
`
`5,592,256
`
`[45] Date of Patent:
`
`Jan. 7, 1997
`
`[54] PHOTOMETRY DEVICE FOR A CAMERA
`
`[75]
`
`Inventor: Masaru Muramatsu, Kawasaki, Japan
`
`[73] Assigncc: Nikon Corporation, Tokyo, Japan
`
`[2]] App]. No.: 654.998
`
`[22]
`
`Filed:
`
`May 29, 1996
`
`Related us. Application Data
`
`[63] Continuation of Set. No. 246,424, May 20, 1994. aban-
`doned.
`
`[30]
`
`Foreign Application Priority Date
`
`Jun. 8, 1993
`
`[JP]
`
`Japan .................................... 5463919
`
`Int. Cl.“ ....................................................... G033 7/08
`[51]
`[52] US. Cl.
`......................... 396/225; 348362; 348/366;
`396/234
`[58] Field of Search ................................... .. 354/430, 432;
`348/362, 366
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,395,099
`4,476,383
`
`7/1983 Terasita .
`I0/1934 Fuknhztra et al. .
`
`4,797,942
`5,137,754
`5,233,517
`5,249,015
`5,266,984
`5,270,767
`5,319,415
`
`.......................................... 382141
`1/1939 Burt
`2/1993 Currin eta].
`
`8/1993 Jindra ................................ 364/413.13
`9/1993 Takagi ct al..
`_
`ll/1993 Mnramatsu et a].
`1211993 Hamadaet al.
`........................ 354/430
`6/1994 Takagi ..................................... 354/432
`
`Primary Examiner—Safet Metjahic
`Ass1'slantExam1'ner—D. P. Malloy
`
`[57]
`
`ABSTRACT
`
`A photometric device for use in a camera includes, but is not
`limited to. a segmented brightness measuring unit which
`segments a photographic scene of a camera into multiple
`areas and which outputs corresponding multiple photometric
`values. A spectral analysis unit performs spectral analysis of
`the spatial frequency of a photographic subject using the
`corresponding multiple photometric values output by the
`segmented brightness measuring unit. Also, a photometric
`computation unit computes photometric values based on the
`spectra] pattern of the photographic subject output by the
`spectral analysis unit. The spectral analysis urtit may be
`disposed within the photometric device, or may be located
`elsewhere in a camera's body.
`
`20 Claims, 4 Drawing Sheets
`
` DUDDD
`
`DCIDDCICJCIDCIEICJEICIUUUUCICIEICJCIDCI
`
`
`
`
`DUDDU
`DDUDD
`DDUDD
`DDUDD
`DDUDD
`DDDDD
`DDDUD
`
`SPECTRAL
`ANALYSIS UNIT
`
`MULTI-PATTERN
`PHOTOMETRIC UNIT
`
`
`
`EXPOSURE
`
`
`
`CONTROL VALUE
`
`
`
`Apple 1212
`
`U.S. Pat. 8,966,144
`
`Apple 1212
`U.S. Pat. 8,966,144
`
`

`
`U.S. Patent
`
`Jan. 7, 1997
`
`Sheet 1 of 4
`
`DDDDDDDD
`
`DDDDDDDD
`
`DDDDDDDD
`
`UDDDDDDD
`
`DDDDDDDD
`
`DDDDDDDD
`
`DDDDDDDD
`
`UDDDDDDD
`
`\I.'\f'J
`
`7
`
`

`
`U.S. Patent
`
`Jan. 7, 1997
`
`Sheet 2 of 4
`
`5,592,256
`
`FIG. 3
`
`DE
`DE
`DE
`DE
`BB
`DD
`
`UDDUUDDUUDDDUUDUDUDDDUDDDUDDUUUDDUUDUDDDHHHHHHHW
`
`DD
`
`SPECTRAL
`
`ANALYSIS UNIT
` MULTI-PA'|TERN
`
`PHOTOMETRIC UNIT
`
`
`
`EXPOSURE
`
`CONTROL VALUE
`
`FIG. 4
`
`
`
`

`
`U.S. Patent
`
`Jan. 7, 1997
`
`Sheet 3 of 4
`
`5,592,256
`
`FIG. 5
`
`HI
`
`LO
`
`DC
`
`DCSL(DC)
`
`DCMD(DC)
`
`ocsc(oc)
`
`

`
`U.S. Patent
`
`Jan. 7, 1997
`
`Sheet 4 of 4
`
`5,592,256
`
`o[n.m]=1/64 E; yE:(B[x.y']1:80i(:1n1_Eni/3)'0°S(2 er my/8))
`
`
`
`FIG. 9
`
`b[n,m]=1/64-Z? XT(B[x.
`I50 3'50
`
`
`
`
`
`
`
`*sin(2 nnx/8)-sin(2 ll‘ my/8))
`Y]
`{L4
`
`2 .4ml).
`n:
`
`
`
`
`
` P[n.m]=a[n,m]-n[n.m] + b[n.m]-b[n.m]
`
`n:O..4 rn:0..4
`
`
`as
`
`DC=P[U.U]
`
`'6
`
`LO=E2 z’P[n,m] - DC
`n=D rn=U
`
`Q"4-I
`
`H1=):‘ z"P[n.m] —LO - DC
`n-0 man
`
`38
`
`as
`
`K[1]=Min[DCSL(DC), LOSL(L0). HISL(HI))
`
`K[2]=Min(DCMD(DC), LOSL(L0]. HISL(HI))
`
`:10
`
`K[.'5]=Min(DCBG(DC). LOSL(LD). HISL(HI))
`
`311
`
`K[4]=mn(ncsL(nc). LOBG(L0), HISL(HI))
`
`:12
`
`K[5]=Min(DCMD(DC). LOBG(LO), HISL(HI))
`
`313
`
`K[6]=Hin(DCBG(DC). LOBG(L0). HISL(HI))
`
`s14
`
`K[7]=Min(DCSL(DC), LOSL(L0). HIBG(HI))
`
`:15
`
`K[B]-—Min(DCMD(DC), LosL(Lo). HIE!G[HI))
`
`:16
`
`K[9]=N|in(DCBG(DC). LosL(Lo), 1-lIBG(HI)
`
`51?
`
`K[1U]=Min(DCS1.(DC), LOBG(L0), HIBG(HI))
`
`:13
`
`K[11]=Min(DCMD(DC), LOBG(LO), HIBG(I-II)"|u_/
`
`:19
`
`K[12]=Min(DCBG(DC). LOBG(L0), HIBG(HI))
`
`320
`
`BP[n]=W[n.1]-DC + 5'a'[n.2]-L0 +. W§r%..'5]-I-II + C[n]
`
`.21
`
`ao=n§;*(K[n1-eP[n1)/gfkinl
`
`

`
`5,592,256
`
`1
`PHOTONEETRY DEVICE FOR A CAMERA
`
`This application is a continuation of application Ser. No.
`08.-"246,424, filed May 20, 1994, now abandoned.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention relates to a camera photometric
`device and, more particularly,
`to a camera photometric
`device which segments a photographic scene into multiple
`areas in which to perform photometry.
`2. Description of the Related Art
`In the past. camera photometric devices included multi-
`pattcm photometric units which divided or segmented a
`photographic scene into multiple areas in which to perform
`classification of a photographic subject. The multiple areas
`were derived by examining the maximum brightness levels
`and the brightness differences among sections of a photo-
`graphic subject. The multiple areas were produced as a result
`of analysis of respective photometric outputs based on the
`aforementioned brightness levels which were selected from
`among several well-known methods, including an exposure
`value computation method which was appropriate for each
`pattern with respect to a photographic scene which corre-
`sponds to a respective pattern. The aforementioned outputs
`were then used to instruct camera circuitry to perform proper
`exposure control. For a discussion of exemplary brightness
`detecting photometric systems, refer to US. Pat. No. 4,395.
`099 to Terasita and U.S. Pat No. 4,476,383 to Fultuhara et
`al.
`
`It is important to note that prior photometric systems were
`designed so that in cases in which the maximum brightness
`of the photometric output was high and the differences in
`brightness levels were large, such photometric systems
`performed exposure control with an emphasis on low bright-
`ness conditions as if a photographic scene included the sun
`or sun light.
`In terms of the problems associated with conventional
`photometric devices of the type described above, there are
`cases in which different exposures are required even in
`photographic scenes classified as the same pattern. For
`example, conventional photometric devices were often
`designed to recognize and detect a scene with a high
`maximum brightness and large differences in brightness
`levels (c.g., a case such as that of a person being rear-lit by
`the sun]. In such situations, an exposure which emphasized
`tow-brightness levels of a photographic subject was set,
`which resulted in a problem in that the portions on which the
`sun was shining were overexposed. Accordingly, the con-
`ventional classification methods described above resulted in
`scenes which could not be sufficiently classified and which
`ultimately resulted in poor picture quality.
`
`SUMMARY OF THE INVENTION
`
`Accordingly, it is an object of the present invention to
`solve the above-mentioned problems associated with exist-
`ing photometric devices.
`It is another object of the present invention to provide a
`photometric device for a camera which can perform a
`classification of a photographic scene having complex pat-
`terns and brightness variances with high accuracy and which
`makes possible the selection of a photometric computation
`method that accurately conforms to a photographic subject.
`
`40
`
`45
`
`50
`
`55
`
`til)
`
`2
`It is still a further object of the present invention to
`provide a photometric device for a camera which utilizes a
`spatial frequency value uansforrnation operation to prepare
`exposure control commands.
`It is still another object of the present invention to provide
`a photometric device for a camera which utilizes a Fourier
`transformation operation to prepare exposure control com-
`rnands.
`
`It is yet another object of the present invention to provide
`a photometxic device which can be cost-efiectively imple-
`mented in a camera device.
`
`These and other objects of the present invention are
`achieved by providing a photometric device for use in a
`camera which includes. but is not limited to, a segmented
`brightness measuring unit which segments a photographic
`scene to be captured by the camera into multiple areas and
`which outputs corresponding multiple photometric values.
`Moreover, the photometric device includes a spectral analy-
`sis unit which performs spectral analysis of the spatial
`frequency of a photographic subject using the corresponding
`multiple photometric values output by the segmented bright-
`ness measuring unit. Also. the photometric device includes
`a photometric computation unit which computes photomet-
`ric values based on the spectral pattern of the photographic
`subject output by the spectral analysis unit.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The above-mentioned and other objects and advantages of
`the present invention will become apparent and more readily
`appreciated from the following description of the preferred
`embodiment, taken in conjunction with the accompanying
`drawings, of which:
`FIG. 1 is a block diagram which depicts an embodiment
`of a photometric device according to the present invention.
`FIG. 2 is a diagram which depicts a divisional configu-
`ration of the photometric device depicted in FIG. 1.
`FIG. 3 is a block diagram which depicts a. configuration
`of a photometric computation device part of the embodiment
`depicted in FIG. 1.
`FIG. 4 is a graph which depicts an example of a two-
`dimensional power spectra P.
`FIG. 5 is a diagram which depicts a condition in which a
`subject is classified by spectra.
`FIG. 6 is a line graph which depicts a membership
`function which relates to a direct current component DC.
`FIG. 7 is a line graph which depicts a membership
`function which relates to a low-frequency component 10.
`FIG. 8 is a line graph which depicts a membership
`function which relates to the high-frequency component HI.
`FIG. 9 is a flow chart which illustrates the operations of
`the photometric device depicted in FIG. 1.
`
`DETAJLED DESCRIPTION OF A PREFERRED
`EMBODIMENT
`
`Reference will now be made to a detailed description of
`a preferred embodiment of the present invention with ref-
`erenoe to the drawing figures which were briefly described
`above. Like parts are referred to with like reference numer-
`als.
`
`therein depicted is a block
`Referring now to FIG. 1.
`diagram of a single-lens reflex (“SLR") camera built into
`which is a preferred embodiment of a photometric device
`according to the present invention.
`
`

`
`5,592,256
`
`3
`Light L reflected from a photographic subject which is to
`be photographed is directed to a focusing screen 4 after it
`passes through a picture-taking or objective lens 2. There-
`after, light L is reflected by a quick return mirror 3 to be
`observed as a scene by a photographer via a pentagonal
`prism 5 and conventional eyepiece optical system.
`Additionally. the image of the photographic subject which
`is produced by light L and which is formed on focusing
`screen 4 is directed to a photometric sensor 7 by a photo-
`metric image reforming lens 6. Photometric sensor 7 is a
`sensor with multiple segments and is shown in FIG. 2.
`Photometric sensor 7 produces photometric output signals
`which describe or otherwise model the brightness distribu-
`tion of the image of the photographic subject. The signals
`produced by photometric sensor 7 are sent to a photometric
`computation unit 8.
`Photometric computation unit 3 is configured to include,
`but should not be limited to. a microcomputer or a micro-
`processor. Photometric computation unit 3 computes expo-
`sure control values based on the photometric output signals
`produced by photometric sensor 7.
`Refening now to FIG. 2, therein depicted is a diagram
`which illustrates a photographic scene of a segmented
`photometric device according to the principles of the present
`invention. As shown in FIG. 2, segmented photometric
`sensor 7, in effect, segments the photographic scene into
`eight sections in both the horizontal and vertical directions
`and outputs a total of sixty-four individual signals indicative
`of scene brightness data. That is,
`the segments forming
`photometric sensor 7 are arranged rectangularly {e.g., a
`square), but the invention should not be so limited. In fact,
`other arrangements and quantities of segments may be
`possible. For purposes of explanation, the respective pho-
`tometric outputs are individually considered as the value
`B[x, y} where B represents BRIGI-ITNESS and the coordi-
`nate pair [x,y} indicates a particular segment of the photo-
`metric sensor 7.
`
`Segmented photometric device 7 is arranged so that a
`sample is 8 points {e.g., segments)><8 points {e.g., segments).
`Thus, a high-frequency component in which the spatial
`frequency is 4 or more cycles per 3 points, shades image
`reforming lens 6 and performs division using an optical
`low-pass filter in order to accurately detect low~frequency
`components.
`therein depicted is a block
`Referring now to FIG. 3,
`diagram which illustrates the configuration of photometric
`computation unit 8 for the preferred embodiment according
`to the present invention.
`The photometric computation device 8 is configured to
`include a spectral analysis unit 81 which implements a
`discrete two-dimensional Fourier transform operation. The
`discrete two-dimensional Fourier transform operation is a
`common and well-known technique which by way of the
`present invention can now be applied to determining bright-
`ness distribution of a photographic subject from a photo-
`metric sensor.
`In the context of the present
`invention,
`however, the two—dimensional Fourier transform is used to
`obtain a power spectrum of the spatial frequencies of a
`photographic subject. A multiwpattern photometric unit 82
`performs multi-pattem photometry using the power spec-
`trum of the spatial frequency of the photographic subject and
`also outputs an exposure control value.
`A Fourier coeflicient “a" of the cos component of the
`two-dimensional spectrum of the photometric output B[x, y]
`and a Fourier coeificicnt “b" of the sin component are
`described as follows:
`
`4
`
`rrln. m] = U64 - E, 2.2 (B[Jr. y] - eos(2mm'8) - cos(2rc-n_v!8]
`
`Where: :1 and m are numbers from 0 to 4;
`
`El
`
`expresses a sum from x=0 to ?;
`
`53;
`
`expresses a sum from y=G to 7.
`
`bid. ml = N64 A 3: Ea (Eli. Jfl - sintlrr.-iris) - sintlronytflj)
`
`[2]
`
`Where:
`
`3:
`
`expresses a sum from x=0 to 7;
`
`E4
`
`expresses a sum from y=0 to 7.
`If the number of segments in the horizontal and vertical
`directions is a power of 2. the photometric sensor 7 can use
`a so—called fast Fourier transform (FFT} algorithm, so it can
`execute the computations in equations U] and [2] at a high
`speed using conventional techniques.
`The two-dimensional power spectrum P is as follows:
`
`Pin. mI=-’-II". rnlvaln. ml+b[n, mlvblrr, m]
`
`[3]
`
`Referring now to FIG. 4, therein depicted is a graph which
`illustrates an example of the two—dimensional power spectra
`P output by spectral analysis unit 81 (FIG. 3). A total of 25
`power spectra from PH), 0] to P[4,4] are indicated.
`The multi-pattern photometric unit 82 is divided into three
`frequency ranges: the direct current component DC of P[0,
`0] in FIG. 4, 8 iow-frequency ranges which are indicated by
`A and 16 high-1'requency ranges which are indicated by B.
`With the three-mentioned ranges, photometric computation
`unit 8 computes the low-frequency component 1.0 which is
`the total value of the power spectra of low—frequency range
`A, and the high-frequency component HI which is the total
`value of the high-frequency range B. Photometric compu-
`tation unit 8 computes the direct current component DC, the
`low-frequency component L0 and the high-frequency enm-
`poncnt I-III according to the following equations:
`
`25
`
`30
`
`35
`
`40
`
`50
`
`D-C=P[0. 0]
`
`L0:
`
`1'-52¢-.P|n. ml -00
`
`P[n, m]—DC +1»: [5}
`
`Where:
`
`is
`
`expresses a sum from n=0 to 2; and
`
`is
`
`65
`
`expresses a sum from m=0 to 2.
`
`m=z13uPIn.ml-L0-DC
`
`[41
`
`[5]
`
`[6]
`
`

`
`5,592,256
`
`5
`
`Where:
`
`2';
`
`expresses a sum from n=0 to 2; and
`
`Zn
`
`expresses a sum from m=0 to 2.
`Referring now to FIG. 5, therein depicted is a diagram
`which illust.rates classification of a photometric subject.
`Classification is performed using the abovc—mentioned
`direct current component DC, low-frequency component L0
`and high—frcquency component H}.
`In FIG. 5, the photographic subject is classified into a total
`of twelve (12) patterns, with three (3) patterns from the size
`of the direct current component DC, two (2) patterns from
`the size of the low~frequency component L0, and two (2)
`patterns from the size of the h.igh—frequcncy component H1.
`Referring now to FIGS. 6-8. therein depicted are line
`graphs which illustrate the membership function for obtain-
`ing a degree K{n] of conformity between the photographic
`subject and a spectral pattern depicted in FIG. 5. The degree
`of conformity is determined with reference to the direct
`current component DC, the low-frequency component L0
`and the high-frequency component HI.
`FIG. 6 shows membership function DCSL.(DC) such that
`the direct current component DC of a photographic subject
`expresses a small degree of conformity. Membership func-
`tion DCMD(DC) expresses a medium degree of conformity
`and membership function DCBG(DC) expresses a large
`degree of conformity.
`FIG. '7 shows membership function LOSL[b0) such that
`the low-1'requency component LO of the subject expresses a
`small degree of conformity and membership function LOB-
`G(l..O) expresses a large degree of conformity.
`FIG. 8 shows membership function H1SL(HI) such that
`the high-frequency component HI of the subject expresses a
`small degree of conformity and membership function HIE-
`G(I-II) expresses a large degree of conformity.
`By using the membership functions discussed above, the
`degree Kjn] to which there is conformance between the
`photographic subject and the twelve (12) spectral patterns in
`FIG. 5 is obtained as follows:
`Where: Miutnl, n2. . . . , n”) are coefiicients which return the
`minimum value from among n1. n2, .
`.
`. , nN.
`
`K[1]=Min(DCS1.{DC). LoSL(D0J. HTSL.(Hl})
`
`K{2i=Min(DCMD(DC). LOSL{L0). I-ustnm)
`
`K{3t=Min(DcsG(oc). L.OSL(I.O), Hts1.tHI))
`
`K|4]=Min(DCSLfDC). LOBG(L0). H1sLrHI))
`
`K[5]=Min(DCMD(DC). t.ooG(t.o), H1SL(H'I)}
`
`K|6}=Min(DCBG(DC). LOBG(I.O), 1-tIst.rHt))
`
`Krr|=Min(ocsL(DC). LosL(Lo). HIBG(Hl))
`
`K[B]=Min(DCMD(DC}, LOSl.(LO). HreG(H1))
`
`Kl9|=MirI(DCBG(DC). L031-(I40). HIEG{H3l))
`
`K[1c1=Mjn(DCsLrDC). LOBG(L0). H]BG(HI))
`
`Kl] l]=Min(DCMD(DC}. LoBG(to}. HIBG(HI))
`
`K[12t=I'u'tin(DCBG{DC). LOBG(l_.O), I-t1BG(HI)}
`
`in
`
`[st
`
`191
`
`[101
`
`[111
`
`[121
`
`[131
`
`[14]
`
`I15]
`
`[16]
`
`[ 1 :-'1
`
`us]
`
`6
`patterns shown in FIG. 5 using the direct current component
`DC.
`the low-frequency component L0 and the hjgh-fre-
`quency component HI. Moreover, BP[n] is computed as
`follows:
`
`Bf’lnE=lrPIn.
`
`ll-.0C+W]n, 2]-L0+W[I'I. 3}-HR-C{r1]
`
`[19]
`
`to 12.
`Where: n is a number from l
`In equation [19], W and C are weighting coefficients.
`Preferably, weighting coeflicients are chosen from those
`which have been studied and optimized through analysis of
`subject patterns extracted in advance.
`An exposure control value B0 is obtained based on
`equation [20] (listed below) by taking a weighted mean of
`BP[n] using the degree of conformance K[n]:
`
`80=£..u<1ni-BPtnnrr., that
`Where:
`
`2|]
`
`3::
`
`expresses a sum from n=O to 12; and
`
`31;
`
`[20]
`
`30
`
`35
`
`4!]
`
`45
`
`50
`
`expresses a sum from n=0 to 12.
`Referring now to FIG. 9, therein depicted is a flow chart
`which outlines the operation of the photometric device of the
`present embodiment. Moreover,
`the flowchart shows the
`operational flow from when photometric value B is obtained
`to when the exposure control value B0 is obtained. It is to
`be understood that the operational flow depicted in FIG. 9 is
`to be carried out by photometric computation unit 3 using
`well-known software and computer programming concepts
`and constructs.
`
`is
`
`In step s1, photometry is performed and B[x, y]
`obtained.
`In step 52, Fourier oocflicient a of the cos component of
`the two—dimensional spectrum of the photometric output
`B[x, y} is computed. and in step s3, Fourier coefficient b of
`the sin component is computed.
`In step s4, the power spectrum P[n, m] is computed from
`Fourier coeificient a and Fourier coellicient b.
`In step s5, the direct current component DC is obtained
`from the power spectrum P{n,
`In]. In step 56,
`the low-
`frequeney component L0 is obtained.
`In step s7, the high-frequency component H1 is obtained.
`Steps 58 through s19 obtain the degrees K[n] of conform-
`ance between a photographic image and the twelve (12)
`spectral patterns using the direct current component DC, the
`low—frequeney component L0, the high-frequency compo-
`nent I-11, and membership functions DCSU DCMD, DCBG,
`LOSL, LOBG, HISL and HIBG as such were described
`above.
`In step s20. BP[n] is calculated using the direct current
`component DC, the low—frequency component L0, the high-
`frequency component HI, and eoeflicients W and C as such
`were described above.
`In step 521. the weighted mean of BP[n] is taken using the
`degree of conformance I([n] to obtain the exposure control
`value B0, thereby completing the operational now.
`In the present embodiment, only the power spectra were
`used in the spectral pattern classification, but it is also
`possible to classify using the respective frequency phases.
`Where respective frequency phases are used,
`the photo-"
`graphic subject can be even more accurately classified.
`The phases (9 at the respective frequencies are as foltows:
`
`The operation expression indicated by equation [19]
`(listed below) is prepared for each of the twelve (12) spectral
`
`GIN. rr:|=ua.n“‘ (bin. ml/aln. ml)
`
`[21]
`
`

`
`5,592,256
`
`5
`
`10
`
`IS
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`7
`For example, E){l , 1] expresses the phase of the wave of
`the first cycle in the vertical and the horizontal directions,
`and if @[ l , l] is 0 degrees. it will be observed that the center
`section is dark and in a rear—lit condition. If SH, 1] is 180
`degrees, it will be observed that the center section is bright
`and in a front.-lit condition.
`The description above indicates that if classification is
`performed using 6[l , l], it is possible to classify the subject
`into front-lit and rear-lit conditions. In this way, spectral
`classification is not limited to the methods described above.
`To the contrary, if classification is done using the power
`spectrum and the phase,
`it is possible to determine the
`exposure of the subject more accurately.
`Moreover. the spectral analysis device should be under-
`stood as limited to use of the Fourier transform. To the
`contrary, other spectral analysis methods may also be used.
`For example, a subject can be classified using spatial fre-
`quency operations, or even a discrete cosine transform
`(DCT) which only uses a cosine function. Moreover, a
`discrete sine transform, which only uses a sine function, or
`a Walsh transform, which uses a Walsh function which is a
`binary function of +1 and -1, may be used. In a Walsh
`transform, in particular. since only the two values of +1 or
`-1 are used, it is possible to perform spectral analysis
`computations at a high speed even with a small—scale device.
`The optimum spectral analysis unit can be operated from
`among the above-mentioned methods, but should not be so
`limited. As new and different methods are developed and
`miniaturized such methods may also be used. All that is
`necessary is that a particular method be able to provide
`required performance levels and be capable of implcn1en—
`tation in a camera's photometric device.
`Although a preferred embodiment of the present invention
`has been shown and described, it will be readily appreciated
`by those of ordinary skill in the an that many changes and
`modifications may be made to the embodiment without
`departing from the spirit or scope of the present invention
`which is defined in the appended claims and in equivalents
`thereof.
`What is claimed is:
`1. A photometric device for use in a camera, the photo-
`metric device comprising:
`segmented brightness measuring means for segmenting a
`photographic scene of the camera into multiple areas
`and for outputting corresponding multiple photometric
`values;
`spectral analysis means for performing spectral analysis
`of the spatial frequency of a photographic subject using
`the corresponding multiple photometric values output
`by said segmented brightness measuring means; and
`photometric computation means for performing photo-
`metric computations based on the spectral pattern of the
`photographic subject output by said spectral analysis
`means to produce exposure control values.
`2. The photometric device according to claim 1. wherein
`said spectral analysis means performs spectral analysis by
`using a Fourier transfonnation operation.
`3. The photometric device according to claim 1, wherein
`said segmented brightness measuring means includes a
`plurality of segments corresponding to sections of the pho-
`tographic scene of the camera.
`4. The photometric device according to claim 3, wherein
`said plurality of segments is a power or 2.
`5. A photometric device for use in a camera, the photo~
`metric device comprising:
`a segmented brightness measuring unit segmenting a
`photographic scene of the camera into multiple areas
`
`S
`and outputting corresponding multiple photometric val-
`ues;
`
`a spectral analysis unit performing spectral analysis of the
`spatial frequency of a photographic subject using the
`corresponding multiple photometric values output by
`said segmented brightness measuring unit; and
`a photometric computation unit computing exposure con-
`trol values based on the spectral pattern of the photo-
`graphic subject output by said spectral analysis unit.
`6. The photometric device according to claim 5, wherein
`said spectral analysis unit performs spectral analysis using a
`Fourier transformation operation.
`7. The photometric device according to claim 5, wherein
`said segmented brightness measuring unit includes a plural-
`ity of segments corresponding to sections of the photo-
`graphic scene of the camera.
`8. The photometric device according to claim 7, wherein
`said plurality of segments is a power of 2.
`9. The photometric device according to claim 8, wherein
`said plurality of segments comprises 64 segments arranged
`rectangularly.
`1|]. A photometric device for use in a camera, the photo-
`metric device comprising:
`a segmented brightness measuring unit segmenting a
`photographic scene of the camera into multiple areas
`and outputting corresponding multiple phototnetric val-
`ues; and
`a photometric computation unit computing exposure con-
`trol values based on a spatial frequency distribution of
`said corresponding multiple photometric values.
`11. The photometric device according to claim 10, further
`comprising:
`a spectral analysis unitpcrforming spectral analysis of the
`spatial frequency of a photographic subject using the
`corresponding multiple photometric values output by
`said segmented brightness measuring unit to produce
`spectral output values, said photometric computation
`unit computing said exposure control values based on
`said spectral output values.
`12. The photometric device according to claim 11,
`wherein said spectral analysis urtit performs spectral analy-
`sis using a Fourier transformation operation.
`13. The photometric device according to claim 11,
`wherein said spectral analysis unit performs spectral analy-
`sis using a discrete cosine uansfonn [DCI') operation.
`14. The photometric device according to claim 11,
`wherein said segmented brightness measuring unit includes
`a plurality of segments corresponding to sections of the
`photographic scene of the camera.
`15. The photometric device according to claim 14,
`wherein said plurality of segments is a power of 2.
`16. A photometric device for use in a camera, the photo-
`metric device comprising:
`a segmented brightness measuring unit to segment a
`photographic scene of the camera into multiple areas,
`and in response, outputting corresponding multiple
`photometric values;
`a spectral analysis unit to perform a spectral analysis of
`the corresponding photometric values to obtain a power
`spectrum of the spatial frequencies of a subject; and
`a multi-pattern photometric unit to determine a direct
`current component, a low—frequcney component, and a
`high frequency current component of the power spec-
`trum, to obtain degrees of conformance between the
`photographic scene and a plurality of spectral paltems
`using the direct current, low—frequency and high-Ere-
`
`

`
`5,592,256
`
`9
`quency components and a plurality of membership
`functions, and to obtain an exposure control value by
`taking a weighted mean using the degrees of conform-
`anoe.
`
`17. The photometric device according to claim 16,
`wherein the spectral analysis unil performs the spectral
`analysis by using a Fourier transform operation.
`13. The photometric device according to claim 16,
`wherein the spectral analysis unit performs the spectral
`analysis by using a discrete cosine transform operation.
`
`10
`19. The photometric device according to claim 16,
`
`wherein the spectral analysis unit performs the spectral
`analysis by using a discrete sine transfonn operation.
`
`20. The photometric device according to claim 16,
`
`wherein the spectral analysis unit performs the spectral
`analysis by using a Walsh transform operation.
`
`*
`
`*
`
`*
`
`*
`
`*