JPS63281028A - Light measuring instrument - Google Patents

Abstract

PURPOSE:To obtain proper exposure for a main subject as all times by dividing the nearly center part of a subject field into plural small areas, finding the brightness level of the center area by using brightness information on each small area, and performing specific arithmetic operation according to the brightness level. CONSTITUTION:The area of the nearly center area of the subject field is divided into, for example, four small areas, and photodetecting elements 8-11 which photodetect the light of the subject field area at positions corresponding to the respective areas are arranged to measure the brightness of the subject field, thereby obtaining photocurrents iA1-iA4 corresponding to the brightness. Those photocurrents are compressed 16-19 logarithmically and voltage values VA1-VA4 are outputted. A center brightness value arithmetic circuit 24 inputs those voltage values VA1-VA4 at inputs I11-I14 and compares the maximum value among the input voltages with, for example, three preset reference voltages to judge its level. Then it is decided which of the four voltages VA1-VA4 which are arranged in increasing order is added to arithmetic according to the judged level, and the arithmetic result is outputted as an output O1. This voltage VA1 indicates the brightness information of the subject center area and is used as the light measured value of the center area as it is.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a method of dividing a field into a plurality of regions, obtaining luminance information for each of the plurality of regions, and obtaining a photometric value by various calculations. The present invention relates to a photometric device, and particularly to a photometric device that obtains a photometric value in an area approximately in the center of a photographic field.

[Prior art]

2. Description of the Related Art Partial photometry methods have been proposed in the past that measure only a portion of a field. This partial metering method measures only the main subject and gives the main subject an appropriate exposure even when the surrounding area of the subject is particularly bright or dark, such as in backlit scenes or black background scenes. It was one of the most effective photometric methods. However, in the conventional partial metering method, the area to be metered is always a fixed area, so when the main subject is somewhat small or the main subject is placed at a position slightly offset from the center of the metering area, etc. , there was a problem of underexposure or overexposure.

[Purpose of the invention]

The present invention is a suitable photometry device that assumes that the main subject is located approximately in the center of the field, and is particularly sensitive to the effects of the size of the main subject and the accurate placement of the main subject in the center of the field. An object of the present invention is to provide a photometry device that is not easily affected by the fact that the main subject is not exposed properly and is capable of calculating photometry values that can always give a proper exposure to a main subject.

In order to achieve the above object, the present invention includes a light receiving means comprising a plurality of light receiving sections that divides an area approximately in the center of a field into a plurality of small areas and obtains luminance information for each of the plurality of small areas. ,
Using a calculation means in which a calculation circuit corresponding to a plurality of calculation formulas including one or more of the brightness information for each of the plurality of small areas as a function is set in advance, and the brightness information for each of the plurality of small areas, The present invention is characterized by comprising a selection means for determining the brightness level of the central area and selecting an arithmetic circuit corresponding to one arithmetic expression from the arithmetic means according to the brightness level.

〔Example〕

FIG. 1 shows the results when the present invention is applied to a single-lens reflex camera.
It is a schematic diagram of an optical system. In the figure, 1 is a photographing lens, 2 is a quick return mirror, 3 is a focus plate, 4 is a pentaprism, 5 is an imaging lens, 6 is a light receiving section, and 7 is an image plane.

In this embodiment, a subject image formed on a focus plate 3 by a photographing lens 1 is guided and imaged onto a light receiving section 6 by an imaging lens 5, and photometry is performed. FIG. 2 is an explanatory diagram of the light-receiving surface of the light-receiving section 6 shown in FIG. 1.

In Figure 2, 2A is an area approximately in the center of the field, 2B
is a peripheral area outside area 2A, and area 2A and area 2B are each four small areas 2A.

2A2, 2A3, 2A4 and 2B1.2B2.2B3.
It is divided into 2B4. In this embodiment, as shown in FIG. 2, a plurality of light-receiving elements capable of receiving light in the field of view at positions corresponding to each region are arranged, and the field of view is divided into eight regions 2A, 2A,
, 2A2, 2A3, 2A4.2B, , 2B2.2B
The image is divided into 3.2B4 areas, and the field brightness is photometered for each area. In this embodiment, in order to provide a more effective photometric device, the photometric value at the approximate center of the object field is not directly output from the photometric device, but the photometric value at the periphery of the object field is also calculated. The configuration is such that the output of the photometric device is determined.

The contents of the calculation in this embodiment will be explained below with reference to the drawings.

FIGS. 3 to 7 are diagrams for explaining the circuit configuration of this embodiment.

In Figure 3, 8, 9, 10, 11, 12, 13, 1
4.15 is the above eight areas 2A, , 2A2, 2A3, 2
A4, 2B,.

It is a silicon photodiode (SPD) corresponding to 2B2.2B3.2B4, and the photocurrent iA I +iA 2 +lA 3 IIl corresponds to the brightness of each area.
4 +IB I +'B□+iB:l+is4 is generated. 16, 17, 18, 19, 20, 21, 22゜2
3 logarithmically compresses these photocurrents to vA I +vA
2 +vA3. vA4. vB1. v day 2. VB3. VB
This is a logarithmic compression circuit that outputs a voltage value of 4. vAI,
vA2. vA3゜vA4 +”B I +VB 2 +
VB 3 +”B 4 is constant aI+a2+a3.a4
．． a5. a6. a7. a8 (n o), b (〉o) and photocurrent iA I +iA 2 , tA3 +iA 4 +
It can be expressed as follows using 'B□, iB□+iB3+is4.

■A engineering=a1+b-1niA1 vA2=a2+b*12 ni
A2■A3=a3+b-I! n1A3 VA4=a 4 +b * jl! n1A4VBI
=a 5 +b* 1 n1BIVB2 =a
6 +b IIl n1B2VB3 =a 7
+b @12 n1B2VB3 =a B +
b-1n1B4 However, al+a 2+a3+a4+a
5+a6+a7+a8 is vA1=vA□=VA3=vA4"VB+"VB when the brightness of each area is equal
2 ” Logarithmic compression circuit 1 so that VB3 = vB4
It is assumed that the number is set in advance between 6 and 23. 24 is
Logarithmic compression circuits 16 to 19 output voltage vA1. vA2. v
A3. vA4 respectively input terminal 111+II□+■13+I
14, calculates the brightness value of the central part 2A of the object field, and outputs the voltage vA from the 01 output terminal. 25 is the output voltage V of the logarithmic compression circuits 20 to 23
B! , VB□, vB3゜VB4, respectively, at the input terminal I 21
+I22 +' 23 +' 24 It is a peripheral brightness value calculating circuit which calculates the brightness value of the peripheral part 2B of the object field by inputting it, and outputs the voltage v8 from the 0□ output terminal. The configuration of the central brightness value calculation circuit 24 is shown in FIG. 4, and the configuration of the peripheral brightness value calculation circuit 25 is shown in FIG.

FIG. 4 is a circuit diagram for explaining the circuit configuration of the center brightness value calculation circuit 24 of FIG. 3. In Figure 4, 101
, 102, 103, 104, 105 are magnitude comparison circuits,
This circuit outputs the larger one of the two voltage values input to Il+I2 from the OH output terminal, and outputs the smaller one from the OH output terminal. This magnitude comparison circuit 101-1
04 is shown in FIG. 66 is a comparator having a positive phase/negative phase input terminal and a positive phase/negative phase output terminal, and the positive phase input terminal voltage V
, when the negative-phase input terminal voltage V is v n v , an H-level voltage is output from the positive-phase output terminal, and an L-level voltage is output from the negative-phase output terminal, and when V -V , an L-level voltage is output from the positive-phase output terminal. , and an H level voltage is output from the negative phase output terminal. Analog switches 67 to 70 are in a conductive state when the voltage applied to the control terminal is at H level, and are in an open state when the voltage is at L level.

Assuming that the voltage input to the 11 input terminal is vll, and the voltage input to the I2 input terminal is VI2, when Vll>VI2, the positive phase input terminal voltage v2 of the comparator 66 becomes the negative phase input terminal voltage V. At this time, the voltage at the positive phase output terminal of the comparator 66 is at H level, the voltage at the negative phase output terminal is at L level, the control voltage of analog switch 67.70 is at H level, and the control voltage of analog switch 68.69 is at L level. Because there is an analog switch 67.7
0 is a conductive state, and the analog switches 68 and 69 are open. Therefore, the analog switch 6 is connected to the OH output terminal.
Voltage v1□ is output through 7, and the OH output terminal is
Voltage VI2 is output through analog switch 70. Similarly, when V, , < V, □, the positive phase input terminal voltage V of the comparator 66 becomes the negative phase input terminal voltage V
The positive phase output terminal voltage of the comparator 66 becomes L level, and the negative phase output terminal voltage becomes H level. Therefore, since the control voltage of analog switch 67.70 is at L level,
The analog switches 67 and 70 are in the open state, and since the control voltages of the analog switches 68 and 69 are at H level, the analog switches 68 and 69 are in the conductive state. At this time, the voltage vI□ is outputted to the OH output terminal through the analog switch 69, and the voltage vI+ is outputted to the OH output terminal through the analog switch 68.

In this way, the larger one of the voltages v1□ and v+□ is output to the OH output terminal, and the smaller one is output to the OH output terminal. In FIG. 4, five magnitude comparison circuits are used to calculate the voltage vA1.
vA□.

vA3. The largest of vA4 is vA1*, the second largest is VAZ tree, the third largest is vA3*, and the smallest is VA4.
*It is configured so that it is output in a bound format. The voltage VAI is input to the 11 input terminal of the magnitude comparison circuit 101, and I2
A voltage VA2 is input to the input terminal, and the larger one is outputted from the OH output terminal, and the smaller one is outputted from the OH output terminal. Similarly, the voltage VA3 is input to the I1 input terminal of the magnitude comparison circuit 102, the voltage VA4 is input to the I2 input terminal, and the larger one is output from the OH output terminal,
The smaller one is output from the OH output terminal. In the magnitude comparison circuit 103, the voltage output from the OH output terminals of the magnitude comparison circuits 101 and 102 is inputted to the I, , 12 input terminals,
The magnitudes are compared, and the larger one is output from the OH output terminal, and the smaller one is output from the OH output terminal. Here, the voltages output from the OH output terminal are vAl, ■A2. vA3. v
This is the highest voltage among A4. Similarly, in the magnitude comparison circuit 104, the magnitude comparison circuit 101 and the OH of JO2
The voltage output from the output terminal is input to the I, , I2 input terminals, the magnitude is compared, and the larger one is output from the OH output terminal, and the smaller one is output from the OH output terminal. The output voltages are vA□, vA2. vA3. ■A
4, and the magnitude comparison circuit 105 inputs the OH output terminal voltage of the magnitude comparison circuit 103 and the OH output terminal voltage of the magnitude comparison circuit 104 to the 11 + 12 input terminals and compares them in magnitude. In the magnitude comparison circuit 105, vAI+
vA2. vA3. ■Middle 2 excluding the maximum and minimum of A4
It compares and outputs two voltage values, and the magnitude comparison circuit 10
5 (7) From the OH output terminal, vAl, vA2. vA
3゜The second largest voltage among VA4 is output, and OH
The third largest voltage is output from the output end. In this way, vAl, vA2. vA3. vA4 in descending order VA 1 *> VA 2 *> V A 3
*> V A 4 * Rearranged so that it becomes 2. Fourth
In the figure, 106 is a reference voltage generation circuit, which generates three reference voltages vra, Vrb, and vrc. The magnitude relationship among the reference voltages V ra , V rb , and V re is V ra > V rb > V re. 10
7, 108, 109 are comparators, and the largest voltage VA * of the input voltages vA1.vA2.vA3.vA4 from the III+"l□1I13+114 input terminals is input to the positive phase input terminal, and the negative phase Each input terminal receives a reference voltage V output from the reference voltage generation circuit 106.
ra, Vrb, and Vre are input,
Voltage vAI tree and reference voltages V ra , V rb ,
The magnitude of Vre is compared. Comparator 10
7 outputs H level voltage when VA, *≧V ra, and V
When AI*<Vra, an L level voltage is output. Similarly, the comparator 108 determines that V A I '>
When V rb, HL/bell is output, and when VA 1*<Vrb, L level is output, and the comparator 109 outputs V A 1
*> Outputs H level when Vrc, and outputs L level when vA1*<vrc. 110, 111, and 112 are inverters, and 113 and 114 are AND gates. The input of inverter 110 is connected to the output of comparator 107, the input of inverter 111 is connected to the output of comparator 108, and the input of inverter 112 is connected to the output of comparator 109. One input of the AND gate 113 is connected to the output of the inverter 110, and the other input is connected to the comparator 108.
One input of AND gate 114 is connected to the output of inverter 111 and the other to the output of comparator 109. Comparators 107-109, inverters 110-112, and AND gates 113,1
14, ■Il+11□+I+3+114The input voltage from the input terminal ``A I +vA 2 +''A 3 +
``The largest voltage VAI* of A4 and the three reference voltages V ra output from the reference voltage generation circuit 106
, V rb +Vrc, and the voltage vA,
Detects the level of *, and if Vra<VA, *, Vrb
If <VA 1'<Vra, then V rc < VA
The cases are classified into four cases: I*<Vrb, and vA1*<vrc. 115, 116, 11
7°118 is the or gate, or gate 115 2
The two inputs of the OR gate 116 are connected to the output of the AND gate 114 and the output of the inverter 112, respectively. , respectively, the output of the AND gate 113,
It is connected to the output of AND gate 114 and the output of inverter 112, and the three inputs of OR gate 118 are connected to the output of comparator 107, the output of AND gate 113, and the output of AND gate 114, respectively. 1
Reference numerals 19, 120, 121, and 122 are analog switches, which become conductive when the voltage applied to the control terminal is at H level, and open when the voltage is at L level. The control terminal of the analog switch 119 is connected to the output of the OR gate 115, the control terminal of the analog switch 120 is connected to the output of the OR gate 116, the control terminal of the analog switch 121 is connected to the output of the OR gate 117, and the control terminal of the analog switch 122 is connected to the output of the OR gate 118. connected to the output of or gate 1
15 to 118 and analog switches 119 to 122, the input voltage from the Ill + 112 + 113 + 114 input end is ``A I +vA 2 +vA3.v
The voltage VAI tree, vA2*, vA3*, vA4*, in which A4 is sorted in descending order by the magnitude comparison circuits 101 to 105, is
It is controlled to be conductive or non-conductive depending on the level of the maximum value VAI. The analog switch 119 becomes conductive to the voltage VAI' when the OR gate 115 outputs an H level voltage, and becomes non-conductive when the OR gate 115 outputs an L level voltage. The analog switch 120 becomes conductive to the voltage VA2* when the OR gate 116 outputs an H-level voltage, and becomes non-conductive when the OR gate 116 outputs an L-level voltage. In the analog switch 121, the voltage VA3 becomes conductive when the OR gate 117 outputs an H level voltage, and becomes non-conductive when the OR gate 117 outputs an L level voltage. The analog switch 122 is an or gate 118
Voltage VAJ* becomes conductive when it outputs an H-level voltage, and becomes non-conductive when it outputs an L-level voltage.

113.114, 115, and 116 are resistors with the same resistance value, and the voltages vA, *, vA, *, vA3*, vA
It constitutes an average value circuit that calculates the average value of the voltages that become conductive among the 4* voltages. 117 is an operational amplifier, the output terminal and the negative phase input terminal are connected, and it is used as a voltage follower, and the output voltage vA of the average value circuit composed of resistors 113 to 116 is input to the positive phase input terminal. . The output terminal voltage of the operational amplifier 117 is vA regardless of the circuit state after the output terminal, and this is the main power from the O1 output terminal.

The central brightness value calculation circuit 24 in FIG.
The luminance information from 2A3 and 2A4 is input to the input voltage v.
A1. vA2. vA3. ■A4 is input from the input terminal ■11 + '+2 + II3 + 114, and the level is determined by comparing the maximum value vA1 tree of this input voltage with a preset reference voltage, and the level determined here is Depending on the level, the input voltage vA1. vA2
．． 4-horn voltage vAl*+VA2'+vA3*+vA4 sorted in descending order by comparing vA3゜vA4
It determines which voltage value of the tree is to be added to the calculation, and outputs the calculation result from the 01 output terminal as an output voltage vA. In this embodiment, this output voltage vA represents the brightness information of the central area of the field. A photometric device that calculates the photometric value at approximately the center of the object field may use this output voltage vA as the photometric value, but in this embodiment, the entire screen is used when the main subject is photographed, for example in a landscape photograph. In order to provide a photometric device that is effective even when the main subject is a white subject or a black subject, this output voltage vA is used as the brightness information of the central area of the subject, and the peripheral area of the subject is A photometric device is provided that obtains brightness information of a region and performs calculations using these two types of brightness information to obtain a photometric value.

Next, the circuit operation of the median brightness value calculation circuit shown in FIG. 4 will be explained.

(1) Vra<VAt*(VAIIVA21VA31V
(maximum value of A4) In this case, there is a particularly high-brightness subject in a part of the two-person area, a landscape photo with bright clouds or sky in the center area of the subject, or a landscape photo with white clothes. This applies to photographs of people, or photographs of people against bright backgrounds, where the person is small or placed slightly away from the center of the scene. Even in such cases, it is necessary to give appropriate exposure for people, etc., while giving an exposure that will slightly highlight whitish subjects or particularly high-brightness subjects. Luminance information v at the center of the field
A is four luminance information vA8.A from the central area of the field.
vA2. vA3. Only the minimum value VAd* of vA4 is determined using the following arithmetic expression (2).

vA=vA4*...■ Then, regarding the circuit operation in FIG. 4, first, four pieces of luminance information vA1. vA2. vA3゜vA
Since the maximum value vA1* of 4 is larger than the reference voltage vra,
Comparators 107 to 109 all output H level voltages, and OR gate 11 of OR gates 115 to 118
8 outputs an H level voltage, and the other OR gates 115
117 outputs an L level voltage. Therefore, among the analog switches 119 to 122, the analog switch 12
Only 2 becomes conductive and the other analog switches 119~
121 is in an open state, and the output voltage vA of the central brightness value calculation circuit becomes a VAA tree.

(2) When V rb < V A I k vra In this case, there is a somewhat high-brightness subject in a part of the two-person area, and it is similar to case (1), but in this case, is at a level where the distribution of brightness and darkness of the main subject placed in the central area of the field should be taken into consideration. That is, for example, if there is a dark part in the main subject, it is necessary to depict that part as black to some extent. Therefore, in this case, the brightness information vA at the center of the field is the four brightness information VA s IVA 21 VA 3 from the center area of the field.
1VA 4 f) l & Calculate using the following arithmetic expression (2) for the small value VA4* and the second smallest value vA3*.

vA = (VA3*+VA4*)/2 ・-■ And the circuit operation is as follows: VAl tree is larger than Vrb, and vr
Since it is smaller than a, comparator 107 outputs L level, comparators 108 and 109 output H level, AND gate 113 outputs H level, and OR gate 115
118, OR gates 117 and 118 output H level, and OR gates 115 and 116 output L level. Therefore, among the analog switches 119 to 122, the analog switches 121 and 122 are in a conductive state, and the analog switches 119 and 120 are in an open state, so that the output voltage vA of the central brightness value calculation circuit is (vA3 * + vA4 *)
/2.

(3) When Vrc<VAl *<Vrb In this case, there is no particularly high-brightness subject in the 2A area, and the photograph is a landscape photo or general snapshot in which bright clouds or sky are not located in the center area of the subject. , or even in the case of a photograph of a person, this corresponds to the case where the person is so thick that it covers the entire center area 2A.In such a case, the bright part of the main subject in the center is It is necessary to provide an exposure that appropriately depicts the highlights in the photograph, and the dark parts in the dark and shadows.Therefore, the brightness information vA in the center of the field is determined by the four values in the center of the field. All of the luminance information vA1.VA2.vA3.vA4 is calculated using the following arithmetic expression (2).

vA= (VA l *+vA2 *+vA3 *10v
A4 books) /4-... ■And the circuit operation is VAI tree v
Since it is larger than rc and smaller than Vrb, comparator 1
07 and 108 output L level, comparator 109 outputs H level, AND gate 114 outputs H level, and all OR gates 115 to 118 output H level. Therefore, all of the analog switches 119 to 122 become conductive, and the output voltage v of the central brightness value calculation circuit
A is (vA, *ten VA2*+VA3 tree ten vA4*)/4
becomes.

(4) When V A I * < V re In this case, there are only low-brightness subjects in the 2A area, and if a slightly dark subject is placed in the center, or if the subject is placed in the center of the subject. This corresponds to a case where the main subject is hardly illuminated by illumination light, resulting in a dark area. In such cases, it is assumed that there may be a particularly dark subject or extremely dark area in the center area of the subject, so in addition to depicting the dark subject or dark area as a slight shadow, The brightness information vA at the center of the field is set at the center of the field so that the person can be given almost appropriate exposure even when the person is placed in an area that is not illuminated by illumination light. Four brightness information VA from the area
1. VA2. Among VA3゜VA4, only the minimum value VAJ* is excluded, and the remaining three values vAI *+vA 2
*+”A 3 * is calculated using the following calculation formula (■).

VA=(VAI *+VA2 *+VA 3Q/3
・"■Then, the circuit operation is as follows: Since vA, * is smaller than Vre, comparators 107 to 109 all output L level, inverter 112 outputs H level,
Among or gates 115 to 118, or gates 115 to 118
117 outputs an H level, and only the OR gate 118 outputs an L level. Therefore, among the analog switches 119 to 122, the analog switches 119 to 121 are in a conductive state, only the analog switch 122 is in an open state, and the output voltage vA of the central brightness value calculation circuit is (VAI*+VA2
*+VA3*)/3.

The characteristic feature of the central brightness calculation circuit of the embodiment described above is that, assuming that the main subject is located in the approximately central area (2A) of the field area, the main subject is approximately the same size as the area 2A. It is possible to output brightness information to give an appropriate exposure to the main subject even when the main subject is small compared to the main subject or placed slightly away from the center of the field. As shown in the example, by separately obtaining the luminance information of the peripheral area of the subject and calculating the photometric value with the luminance information of the central part of the subject, a high-luminance subject can be compared to a high-luminance subject. This makes it possible to depict low-brightness subjects as if they were low-brightness subjects, and it is difficult to give an appropriate exposure when only the brightness information in the center of the field is targeted, as in landscape photography. In such a case, it is possible to provide a very effective photometry device that makes it possible to provide an appropriate exposure by actively utilizing the luminance information of the periphery of the object field.

The configuration of the peripheral brightness value calculation circuit 18 is shown in FIG.

In Figure 6, 20, 21, 22.23 are resistors with the same resistance value, and vBI + VB 2 + vB
It is for averaging 3 + vB 4. 24
is an operational amplifier, the output end and the negative phase input end are connected,
Used as a voltage follower. The output terminal voltage of the operational amplifier 24 is equal to the positive phase input terminal voltage regardless of the circuit state after the output terminal. The output VB of the operational amplifier 24 is Va = (Vs+ +VB2 +
Va 3 +VB 4 ) / 4, which is 0□
Output from the output end. As described above, the peripheral brightness value calculation circuit 18 outputs the average value of the brightness of the peripheral part of the object field as v8 from the 02 output terminal.

In FIG. 3, 19 inputs the output voltage vA of the central brightness value calculation circuit 24 and the output voltage VB of the peripheral brightness value calculation circuit 25 to the input terminals I31+I3□, calculates the photometric value, and outputs it from the output terminal 03. Voltage V. This is a photometric value calculation circuit that outputs . The configuration of this photometric value calculation circuit 19 is shown in FIG.

In FIG. 7, 25 is a reference voltage generation circuit, which generates reference voltages V rl , V r2 , V rs , V
r4 is occurring. Reference voltage V rl , V r2
, V rs and V r4 are as follows: V rt >
V r2 > V rs > V r4. 26,
27, 28, and 29 are comparators, the input voltage VB from the 132 input terminal is input to the positive phase input terminal, and the reference voltage V rl output from the reference voltage generation circuit 25 to the negative phase input terminal, respectively. V r21V rs , V
r4 is input, voltage v8 and reference voltage V rl
, V r2 , V rs , and V r4 are compared in magnitude. Comparator 26 is V B2V rl
When VB<vrl, an H level voltage is output, and an L level voltage is output when VB<vrl. Similarly, comparator 2
7 is H level when VB>Vr2, VB<Vr
2, the L level is output, and the comparator 28 outputs V 1
The comparator 29 outputs an H level when 3>Vrs, an L level when vB<vr3, and the comparator 29 outputs an L level when VB>Vrs.
r4 (7) When HL/Bell, "B < V r4
When , L level is output. 30, 31, 32, and 33 are inverters, and 34, 35, and 36 are AND gates.

The input of the inverter 30 is connected to the output of the comparator 26, the input of the inverter 31 is connected to the output of the comparator 27, the input of the inverter 32 is connected to the output of the comparator 28, and the input of the inverter 33 is connected to the output of the comparator 29. One input of the AND gate 34 is the inverter 30
The other input is connected to the output of the comparator 27, and one input of the AND gate 35 is connected to the output of the inverter 31.
The other side is connected to the output of the comparator 28, and the AND gate 3
One input of 6 is connected to the output of inverter 32, and the other input is connected to the output of comparator 29. Comparators 26-29. Inverters 30-33. and AND gates 34 to 36, ■ input voltage v from input terminal 32
8, and four reference voltages V rl , V r2 , V rs output from the reference voltage generation circuit 25.

The level of the input voltage VB is detected by comparing it with Vr4, and if V,l<V8, Vr2<VB<V
rl (7) If V rs< V B < V r2
If V rA≦V B < V rs, V
It is classified into 5 cases where B < V r4. 3
7.38 is a comparator, and 131 is connected to the positive phase input terminal.
The input voltage vA from the input terminal is input, and the reference voltages V rl and V r4 output from the reference voltage generation circuit 25 are input to the negative phase input terminal, respectively, and the voltage vA
The reference voltages V rl and V r4 are compared in magnitude. The comparator 37 outputs an H level voltage when vA > V rl, and outputs an L level voltage when vA < vrl. The comparator 38 outputs an H level voltage when vA≧Vr4, and outputs an L level voltage when VA<Vr4.
Outputs level voltage. 39° 40 is an inverter, and the input of the inverter 39 is connected to the output of the comparator 37.
The input of inverter 40 is connected to the output of comparator 38. 41°42 and 43.44 are AND gates. One input of the AND gate 41 is connected to the output of the comparator 26, and the other input is connected to the output of the comparator 37.
One input of the AND gate 42 is connected to the output of the comparator 26, the other to the output of the inverter 39, one input of the AND gate 43 is connected to the output of the inverter 33, the other is connected to the output of the comparator 38, One input is connected to the output of inverter 33, and the other input is connected to the output of inverter 40. comparator 37,
38, inverters 39, 40, and gates 41 to 44
When the level of the input voltage ①8 is determined to be Vrl<v8 and vB<vr4, the level of the input voltage vA is further detected, and when Vrl≦vA and vA are determined, respectively.
< Vrl, and Vr4<V
It is classified into two cases: A case and VA<V, 4 case. As explained above, comparators 26 to 29
, 37.38, inverter 3o~33°39.40. ANDGATE 34-36. 41-44 is ■3□.

■. The input voltages vA and VB from the input terminals are converted into the reference voltage V rl r V r2 output from the reference voltage generation circuit 25.
, Vrs + Vr4, the following seven cases are classified, and one of the AND gates 34 to 36. 41 to 44 is set to H level, and all others are outputted to L level. There is.

(1) Vrl < VB, Vrt < VA
(AND gate 41) (H level) (2) Vrl <
v8. vA< Vrl (7nd gate 42) HL
/ Bell) (3) Vr2 < V B < V
rl (7nd gate 34) MiHL/Bell) (4)V
r3 < VB < Vr2 (7nd gate 35) HL/Bell) (5) Vr4 < VB
< Vr2 (7nd gate 36) HL/Bell) (6) VB< Vr4 Vr4< VA (7
(7) VB < Vr
4. VA < Vr4 (7:/gate44) H
L/Bell) 45.46 are OR gates with 6 inputs and 3 inputs respectively. The six inputs of the OR gate 45 are the output of the AND gate 41, the output of the AND gate 42, the output of the AND gate 34, the output of the AND gate 36, the output of the AND gate 43, and the AND gate 4.
4, and the three inputs of the OR gate 46 are
They are connected to the output of AND gate 34, the output of AND gate 35, and the output of AND gate 36, respectively. 47
．． Reference numerals 48, 49, and 50 indicate analog switches, which are in a conductive state when the voltage applied to the control terminal is at H level, and are in an open state when the voltage is at L level. The control terminal of the analog switch 47 is connected to the output of the AND gate 41, the control terminal of the analog switch 48 is connected to the output of the OR gate 45, the control terminal of the analog switch 49 is connected to the output of the OR gate 46, and the control terminal of the analog switch 48 is connected to the output of the OR gate 46.
The 0 control terminal is connected to the output of the AND gate 44.

A reference voltage V rl is output from the reference voltage generation circuit 25 according to the level of the input voltage vA from the 131 input terminal and the input voltage VB from the I22 input terminal by the analog switches 47 to 50 (or game) 45, 46, V r
4 and the input voltage V from the 131 input terminal and the 132 input terminal
A + "B are controlled to be conductive or non-conductive. 51, 52, 53, and 54 are resistors having the same resistance value, and the reference voltage V rl output from the reference voltage generation circuit 25 , Vr4, and the input voltages vA and VB from the ■3□ input terminal and I32 input terminal, which form an average value circuit that calculates the average value of the voltages that become conductive. 55 is an operational amplifier; The output terminal and the negative phase input terminal are connected and used as a voltage follower, and the output voltage V of the average value circuit composed of resistors 51 to 54 is input to the positive phase input terminal.The output of the operational amplifier 55 The terminal voltage is V regardless of the circuit state after the output terminal, and this is output from the 03 output terminal.

As shown above, the photometric value calculation circuit 19 in FIG.
Input to the input terminal and output voltage V from the 03 output terminal. is outputting. This output voltage V. However, in this embodiment, an arithmetic expression that includes only the brightness information of the central area of the object field, an arithmetic expression that includes only the brightness information of the peripheral area of the object field, or an arithmetic expression that includes the brightness information of the central area of the object field and the peripheral area. One of the three equations is selected from a few equations that include both luminance information, and the photometric value is determined by calculation based on the selected equation.

Next, the operation of the circuit shown in FIG. 7 will be explained with reference to FIG.

(1) V rl < V B, V rl < V
A: In this case, there is a fairly high-brightness subject in both the 2B and 2A areas, and a whitish or shining subject is placed in the center as the main subject, with the clear sky or sea in the background. This is the case. In such a case, it is necessary to provide exposure that appropriately highlights the main subject, depending on the brightness level of the main subject.

Therefore, the photometric value V. As shown in FIG. 8(a), the target is the brightness information vA of the central area 2A, and is a constant Vrl for appropriately highlighting the brightness information vA according to the level of the brightness information vA.
It is calculated using the following calculation formula (■).

V 6 = (VA + Vrl ) / 2'''■ Then, regarding the circuit operation in FIG. 7, first, since the luminance information v8 of the peripheral area 2B is larger than the reference voltage Vrt, the comparators 26 to 29 all output H level. Also, since the brightness information vA of the central region 2A is higher than the reference voltage V rl, the comparator 37 outputs the H level. Therefore, among the AND gates 34 to 36 and 41 to 44, only the AND gate 41 outputs the H level. All of the other AND gates 34 to 36 and 42 to 44 output L level.Therefore, among the analog switches 47 to 50, analog switch 47.48 is conductive, and the other analog switches 49.50 are open. The output voltage of the photometric value calculation circuit is V.

is (V A+Vrl)/2.

(2) When Vrl < VB, VA < Vrl In this case, there is a fairly high-luminance object in the 2B area,
When there is a subject in the 2A area that is not very bright,
This is the case when the main subject, such as a person, is placed in the center against the background of the sky or the sea on a clear day, or when a so-called backlit scene is taken.

In such a case, it is necessary to ignore the brightness information of the background and provide appropriate exposure to the main subject. Therefore, the photometric value V.

As shown in FIG. 8(b), the luminance information vA of the central area 2A is the target, and is determined from the following arithmetic expression (2).

(2) o=vA... (2) In the circuit operation, the comparators 26 to 29 all output H level, and the comparator 37 outputs L level. Therefore, only the AND gate 42 outputs the H level, and the other AND gates 34 to 36°41, 43, and 44 all output the L level. Therefore, among the analog switches 47 to 50, the analog switch 48 is in a conductive state, and the other analog switches 47, 49, and 50 are in an open state, so that the output voltage V of the photometric value calculation circuit. becomes vA.

(3) When Vrz≦V B < V rl In this case, there is a somewhat high-luminance subject in the 2B area, which corresponds to a bright outdoor scene on a clear day. In such cases, unlike in cases (1) and (2), the 2B area is often an important shooting target, so it is necessary to appropriately depict not only the central area but also the peripheral area. . Therefore, the photometric value V. As shown in FIG. 8(c), the luminance information vA of the central region 2A and the luminance information v8 of the peripheral region 2B are both targeted, and is determined from the following arithmetic expression 〇.

V 6 = (VA+Va) /2 − (2) In the circuit operation, the comparator 26 outputs an L level, and the comparators 27 to 29 output an H level.

Therefore, only the AND gate 34 outputs the H level, and the other AND gates 35, 36, and 41 to 44 all output the L level. Therefore, among the analog switches 47 to 50, analog switches 48 and 49 become conductive,
The other analog switches 47.50 are in the open state,
Output voltage V of the photometric value calculation circuit. is (VA +VB)/2
becomes.

(4) When V r3 < V B < V r2 In this case, there is a subject with medium brightness in the 2B area, and this corresponds to a general outdoor or bright indoor scene. In such a case, the brightness information of the main subject in the center is thicker than the light hitting the main subject, depending on the reflectance of the main subject, that is, whether the subject is whitish or dark. In order to render a whitish or blackish subject blackish, it is better to determine the exposure based on the luminance information of the peripheral area.Therefore, the photometric value v0 is determined by the luminance information VB of the peripheral area 2B as shown in Fig. 8(d). It is calculated using the following calculation formula (■).

vo=v8...■Then, the circuit operation is as follows: comparators 26 and 27 are at L level, comparator 2
8 and 29 output H level.

Therefore, only the AND gate 35 outputs the H level, and the other AND gates 34, 36, 41 to 44 all output the L level. Therefore, among the analog switches 47 to 50, the analog switch 49 is in a conductive state, and the other analog switches 47, 48, and 50 are in an open state, so that the output voltage V of the photometric value calculation circuit. becomes v8.

(5) When Vr4≦VB<Vr3 In this case, there is a somewhat low-luminance subject in the 2B area, and this corresponds to a typical dark outdoor or indoor scene. In such cases, it is assumed that the background is a little dark compared to the main subject, a so-called black background scene, or that only the main subject is illuminated, so the surrounding areas may also be reflected in the central area. It is also necessary to give the area adequate exposure.

Therefore, the photometric value V. As shown in FIG. 8(e), the luminance information vA of the central region 2A and the luminance information v8 of the peripheral region are both targeted, and is determined by the following arithmetic expression (2).

Vo = (VA + Va) /2 - (2) In the circuit operation, the comparators 26 to 28 output L level and the comparator 29 outputs H level.

Therefore, only the AND gate 36 outputs the H level, and the other AND gates 34, 35, and 41 to 44 all output the L level. Therefore, among the analog switches 47 to 50, the analog switches 48 and 49 are in the conductive state,
When the analog switches 47 and 50 are open, the output voltage of the photometric value calculation circuit is V. is (vA+VEI)/2.

(6) VB < Vr4. Vr4 < VA (7)
In this case, there is a subject with considerably low brightness in area 2B, and a subject with not-so-low brightness in area 2A, for example, when the light falls on a person placed in the center of a dark background such as a stage. This corresponds to a so-called black background scene. In such a case, it is necessary to ignore the brightness information of the background and provide appropriate exposure to the main subject. Therefore, the photometric value V. As shown in FIG. 8(f), the brightness information vA of the central area 2A is used as the object, and the following calculation formula
Seek more.

Vo=VA...■Then, the circuit operation is such that comparators 26 to 29 all output L level,
Further, the comparator 38 outputs an H level. Therefore, only the AND gate 43 outputs the H level, and the other AND gates 34 to 36°41, 42, 44 all output the L level. Therefore, among the analog switches 47 to 50, the analog switch 48 becomes conductive, and the other analog switches 47, 49, and 50 become open, so that the output voltage V of the photometric value calculation circuit. becomes vA.

(7) VB <Vr4. When VA<Vr4, in this case there is a subject with considerably low luminance in both the 2B area and the 2A area, such as a night scene. Usually, in such a case, the main subject is a shadow part in the 2A area or 2B area, so it is preferable to provide an exposure that appropriately depicts a shadow according to the brightness level. In addition, in such cases, it is likely that there is a strong light source or extremely dark area in the peripheral area, so it is easier to obtain an appropriate exposure if the brightness information of the central area is used as the standard. .

Therefore, the photometric value V. As shown in FIG. 8(g), using the brightness information vA of the central area 2A as the target, and using the constant V r4 to appropriately depict shadows according to the level of the brightness information vA, the following calculation formula (■) is obtained. demand.

Vo=(VA+Vr4)/2 . . . In the circuit operation, the comparators 26 to 29 all output L level, and the comparator 38 outputs L level.

Therefore, only the AND gate 44 outputs the H level, and the other AND gates 34 to 36 and 41 to 43 all output the L level. Therefore, among the analog switches 47 to 50, the analog switch 48.50 becomes conductive,
The other analog switches 47 and 49 are open, and the output voltage of the photometric value calculation circuit is V. (V A ten V r4 )
/ It becomes 2.

The characteristic feature of the photometry device of the embodiment described above is that, assuming that the main subject is in the center of the field area (area 2A), proper exposure can be achieved even in backlit scenes and black background scenes. In addition, it is possible to perform photometric value calculations that provide exposures that depict whitish subjects as if they were whitish subjects and blackish subjects as if they were black subjects.

In the embodiment described above, the area 2A at the center of the screen is divided into four small areas 2A 1, 2A2, 2A3 . Although the image is divided into 2A4 areas, it is also possible to divide the image into more small areas and use similar calculations to obtain the brightness information of the center of the object. The maximum value of the brightness information of the four small areas is depicted and the calculation formula is determined according to the brightness level, but the brightness level of the average value of the brightness information of the four small areas, the maximum value and the minimum value The calculation formula may be determined according to the brightness difference, which is the difference in values.Also, in the embodiment described above, the calculation formula is selected by dividing the brightness levels of the four small areas into four stages. , it is also possible to perform a more detailed case classification and select the arithmetic expressions in five or six stages.

Furthermore, in the embodiment described above, not only the luminance information of the central area of the subject but also the luminance information of the peripheral area is obtained, so that appropriate exposure can be given even to whitish subjects or dark subjects. However, it goes without saying that the output of the central luminance value calculation circuit in the embodiment described above may be directly output as a photometric value and used as a photometric device for only the central area of the object field.

Note that the present invention is not limited to single-lens reflex cameras, but can also be favorably applied to lens-shutter cameras and the like. Note that in this embodiment, the selection circuit is configured with a logic circuit, but it may also be processed using software using a microcomputer.
Naturally, it is a matter of enthusiasm that the present invention will be put into practice.

〔Effect of the invention〕

As explained above, the present invention is a suitable photometry device that assumes that the main subject is located approximately in the center of the field. It is possible to provide a photometric device that is capable of calculating photometric values that can give appropriate exposure to the main subject even when the main subject is not located in the central area of the photographic field.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical system as an embodiment when the present invention is applied to a single-lens reflex camera. FIG. 2 is an explanatory diagram showing a plurality of light-receiving areas on the light-receiving surface of the light-receiving means of FIG. 1. Figure 3 is a circuit diagram of the photometric device. FIG. 4 is a detailed circuit diagram of the central brightness value calculation circuit shown in FIG. 3. FIG. 5 is a detailed circuit diagram of the magnitude comparison circuit shown in FIG. 4. FIG. 6 is a detailed circuit diagram of the peripheral brightness value calculation circuit of FIG. 3. FIG. 7 is a detailed circuit diagram of the photometric value calculation circuit shown in FIG. 3. FIG. 8 is an explanatory diagram illustrating the photometric value calculation formula selected in FIG. 7. 2A, 2A2, 2A3.2A4.2B, 2B2.2
B3.2B4・・・・・・・・・・・・・・・・・・
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・・・・・・Each small area to receive light 6・・・・・・・・・・・・
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・・・・・・・・・・・・・Light receiving section 24・・・・・・・
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・・・・・・・・・・・・・Center brightness value calculation circuit 25
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・・・・・・・・・・・・・・・・・・Ambient brightness value calculation circuit 26・・・・・・・・・・・・・・・・・・
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...Photometric value calculation circuit/shi3 ZAwo

Claims (1)

[Scope of Claims] Light-receiving means comprising a plurality of light-receiving sections that divide a region approximately in the center of a field into a plurality of small regions and obtain luminance information for each of the plurality of small regions; the central region using a calculation means preset with a calculation circuit corresponding to a plurality of calculation formulas including one or more of the brightness information for each area as a function, and the brightness information for each of the plurality of small areas; A selection means for determining a brightness level and selecting an arithmetic circuit corresponding to one arithmetic expression from the arithmetic means according to the brightness level, and photometry for an area approximately in the center of a field. Device.