JPS63154921A - Photometric apparatus - Google Patents

Abstract

PURPOSE:To perform proper exposure, by providing a means for descriminating whether an all-round fisheye lens is mounted as an interchangeable lens and correcting the brightness information of a peripheral region only on the basis of the information of a central region and the brightness information of a substituted region or the central region when the fisheye lens is mounted to calculate a photometric value. CONSTITUTION:In an all-round fisheye lens, the light of a field to be photographed does not reach the outside of a dotted line circle. The kind information of CPU on the side of an interchangeable lens is discriminated on the side of a camera main body by a discrimination circuit S and a photometric value V0=(VA+VB)/2 is calculated only using the brightness signals VA, VB of regions 4A, 4B. In a case other than the fisheye lens, photocurrents generated by SPD 8-13 are compressed by logarithmic compressing circuits 14-19 corresponding to the brightnesses of six regions 4A-4C4 to output voltages VA-VC4 and the brightness values of the peripheral parts 4C1-4C4 of the field to be photographed are calculated from VC1-VC4 in a circuit 20, and voltages VA, VB and the voltage VC of the circuit 20 are used in a circuit 21 to emit voltage V0 as a measured value under the judge S of the non-mounting of the fisheye lens and proper exposure is performed in both cases.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a photometry device that divides a field into a plurality of regions and calculates a photometric value based on luminance information for each of the plurality of regions. This relates to correction when a full-circle fisheye lens is attached as an interchangeable lens.

[Prior art]

2. Description of the Related Art Conventionally, various photometering devices have been proposed that divide a field into a plurality of regions, measure light for each region, and use these plurality of photometered brightness values to provide an appropriate exposure to a photographic screen.

Examples of such photometric devices include Utility Model Publication No. 51-9271 and Japanese Unexamined Patent Publication No. 54-123030.

These photometers measure the brightness of each divided area of the field, and select and calculate conditions for obtaining the appropriate exposure of the screen from a plurality of outputs.

Therefore, the basic condition for obtaining proper exposure is to accurately measure the brightness of each divided area. In addition, center-weighted average metering, which is commonly used as a metering method for conventional cameras, measures the entire screen using a single light-receiving area, so in backlit scenes, etc., the center-weighted average metering is overshadowed by a bright background and the main area is The subject was underexposed.

In recent years, some commercialized cameras have adopted a method that measures the field of view by dividing it into many parts and calculates the average of each metered value to obtain the metered value for the entire screen, but in this case, backlighting It has been recognized that the photometric values of the bright background and dark main subject in the scene are averaged, reducing the degree of underexposure of the main subject. A prerequisite for this multi-division average photometry is that the brightness of each divided area is accurately measured.

However, in cameras with interchangeable lenses, accurate photometry may not be possible even after correction.

With a full-circle fisheye lens, which is a type of interchangeable lens, the image circle is inscribed in the short side of the screen, so the subject light does not reach the periphery of the long side of the screen at all, making it impossible to measure light in the peripheral area of the screen. Become.

[Object of the Invention] The present invention is a photometer that divides the field of view and receives light, and is capable of independently measuring at least the central area and the peripheral area of the screen, and is capable of determining appropriate photometric values even when a full-circle fisheye lens is attached. The purpose is to provide a photometric device that can

In order to achieve the above object, the present invention provides a determining means for determining whether or not at least a circumferential fisheye lens is attached as an interchangeable lens, and when the discriminating means determines whether the circumferential fisheye lens is attached, the peripheral The present invention is characterized by a photometry device that performs correction to replace brightness information of a region with brightness information of a central region, or perform correction to obtain a photometric value using only brightness information of a central region.

〔Example) Next, embodiments of the present invention will be described according to the drawings.

FIG. 1 is an optical layout diagram of a photometric system for implementing the present invention in a single-lens reflex camera.

In the figure, 1 is a focusing plate, 2 is a penta roof prism, 3 is an imaging lens, 4 is a light receiving section, 5 is an eyepiece lens, 6 is an exchangeable photographing lens, 7 is a quick return mirror, and 8 is a film. In FIG. 1, a subject image formed on a focusing plate 1 by a photographic lens 6 is guided and imaged onto a light receiving section 4 by an imaging lens 3, and photometry is performed.

FIG. 2 is an explanatory diagram of the light-receiving surface of the light-receiving section 4 shown in FIG. 1. In the figure, 4A is the central area of the field, and 4B is the area 4A.
The middle region of the shape surrounding the 4G+, '4
C2,4G3. 4C4 indicates each divided light receiving area that receives light from each area of the divided peripheral part of the object field. Note that the central region in the present invention refers to the combined area of areas 4A and 4B, and the peripheral area refers to the combined area of areas 4C and 4C4.

In addition, the area indicated by the dotted line in FIG. 2 indicates the photographing range when a full-circle fisheye lens is attached as an interchangeable lens. This area is a circle that is almost inscribed in the short side of the entire photographable area of one frame of film 8, and its surrounding area (
(outside the area) will not be exposed at all. It is assumed that although the actual sizes of the entire photographable area of the film 8 and the entire area of the light receiving section 4 are different, the range to which the light of the object is guided is almost the same.

3 to 5 are circuit diagrams for explaining the circuit configuration of the first embodiment of the present invention.

In Figure 3, 8, 9, 10, 11, 12°13 are
The above six areas 4A, 4B, 4C+, 4G2.4G3,
Silicon photodiode (SPD) compatible with 404
and the photocurrent iA according to the brightness of each area,
iB, ice.

i C2,i C3,i (Generate z.14~1
9 logarithmically compresses these photocurrents to obtain VA, VB
.

This is a logarithmic compression circuit that outputs voltage values of V C+, V C2, V C3, and V 04. Voltage VA, VB
, M.C.I.

V C2,V (:3. V Ca is constant al +
a2, a3.

a< , as , aa (>O), b (>O) and photocurrent iA , iB , ice, iC2,
It can be expressed as follows using iC3 and iC4.

VA=13. +b [n1A VB =a2+b uniB VC1=a3 +b fLn 1cIV(:2=a4
+b j2n 1c2VC3=a5+b j2ni
c3 VC4=a6+ b fL n i C4 However, a
+ , a2 , a3 , a4 , a5 , and a6 are VA = VB = V C+ when the brightness of each area is equal.
It is assumed that the logarithmic compression circuits 14 to 19 are set in advance so that = V C2 = V C3 = V Ca. 20 is the output voltage V l of the logarithmic compression circuits 16 to 19
:+, V C2, V C3, V C4 each input terminal 1
1.

■ Input to +2+ 113+ 114, calculate the brightness value of the peripheralmost part 2C of the object, and output the voltage V from the 01 output terminal.
This is a peripheral brightness value calculation circuit that outputs C. The configuration of this peripheral brightness value calculation circuit 20 is shown in FIG.

In FIG. 4, 23, 24, 25.26 are resistors having the same resistance value, and the voltage VC+.

This is for averaging V Cx, V C3, and V C4.

Reference numeral 27 denotes an operational amplifier, whose output end and anti-phase input end are connected, and is used as a voltage follower. The output terminal voltage of the operational amplifier 27 is equal to the positive phase input terminal voltage regardless of the circuit state after the output terminal. The output VC of the operational amplifier 27 is VC=(VC++ VC2+ V
C3 + VC4) / 4 There is a signal, and this is output from the 01 output terminal.

As described above, the peripheral brightness calculation circuit 20 outputs the average value of the brightness of the peripheral part of the object field as VC from the o1 output terminal.

21 in FIG. 3 is the output voltage V of the logarithmic compression circuit 14.15
A, VB, and the output voltage VC of the peripheral brightness calculation circuit 20 are input to the input terminals 1211, 1221, and 123, respectively, and a control voltage corresponding to the determination of whether or not the all-round fisheye lens is attached is input manually from the determination circuit S to the control terminal C/input. This is a selection circuit which determines which of the two arithmetic expressions to be selected from two arithmetic expressions to be described later, performs the arithmetic operation, and outputs a voltage ◯o as a photometric value from the 02 output terminal. This selection circuit 2
The configuration of 1 is shown in FIG.

FIG. 5 is a circuit diagram of the selection circuit 21 in FIG. 3.

28, 29.30 are resistors with the same resistance value, and the voltage V
A, VB, Vf; or voltages VA, VB are averaged. 31 is an inverter that inverts the control voltage input to the control terminal C/input.

That is, the output voltage of the inverter 31 becomes L level when the control voltage is H level, and becomes H level when it is L level. 32.33 is an analog switch, and the average value of voltages VA, VB, Vf: (VA + V
B +VC)/3 or (V^+VB)/2 is considered conductive. 34 is an operational amplifier, an output end and a negative phase input end are connected, and the operational amplifier is used as a voltage follower. The output terminal voltage of the operational amplifier 34 is
Regardless of the row circuit state, a voltage equal to the positive phase input@voltage is output. The output VO (photometric value) of the operational amplifier 34 is V
O = (V to VB + VC) / 3 or (VA + VB
) 721'A'l, this is output from the 02 output terminal. As described above, the selection circuit 21 determines which of the two arithmetic expressions to select according to the control voltage output from the discrimination circuit S that discriminates whether the all-round fisheye lens is attached. , the output voltage corresponding to the calculation result is 0.
Output from 2 output terminals.

In FIG. 3, the discrimination circuit S discriminates whether or not the interchangeable lens attached to the camera body is a full-circle fisheye lens, based on an output signal from a circuit CPU incorporated in the interchangeable lens side. Note that electrical communication between the camera body and the interchangeable lens is performed via the connector CN.

Next, the operation of the circuits shown in FIGS. 3 and 5 will be explained.

(1) When an interchangeable lens other than the all-round fisheye lens is attached, in other words, when it is determined that the all-round fisheye lens is not attached; Except for special cases such as backlit photography or when the subject includes a particularly bright subject such as the sun or the ground plane, or a particularly dark subject, the brightness of the entire subject area is reduced. By averaging, you can find the photometric value that will give you the correct exposure.

That is, all areas 4^, 4B of the field.

Using the luminance signals VA, VB, and VC of 4C2 to 4C4 as symmetry, the photometric value VO is determined by the following arithmetic expression (2).

VO= (to V+VB +VC) /3
,...■ As for the circuit operation, first, based on the lens type information signal stored in the circuit CPU on the side of the interchangeable lens (in this case, other than the full-circle fisheye lens), the discrimination circuit S
An L level voltage is output from the control terminal C/input, and the control voltage at the control terminal C/in becomes L level. Therefore, the control voltage of the analog switch 32, which conducts the average value of voltages VA, VB, and VC, becomes H level by the inverter 31, and the control voltage of the analog switch 33, which conducts the average value of voltages VA, and VB, becomes L level. Therefore, in this case, the output voltage V from the operational amplifier 34. is (VA +VB +VC)/3.

(2) A full-circle fisheye lens was installed as an interchangeable lens.
: In this case, as shown by the dotted line in FIG. 2, the field light that has passed through the all-round fisheye lens does not reach the entire area of the light receiving section 4. Specifically, referring to FIG. 2, the field light does not reach the portion outside the circular dotted line indicating the area of the fisheye lens photography range in the peripheral areas 4G, 4C4. Therefore, if the photometric location is simply determined using the luminance signal VC (the average of VC, VC4) obtained from the surrounding areas 4G+ to 4C4, an incorrect value will be obtained. This is because, for example, the peripheral area 4C.

~404, if the area to which the subject light is guided is set to 1/3, the brightness for the 1/3 area to which this light is guided is determined by the calculation of the logarithmic compression circuit in FIG. 3 (for example, VC1=a3+bln
iC+) to the voltage value VC.

This is because the luminance information becomes approximately 1/3 of the voltage for VC4.

Therefore, the brightness signal VA in areas 4A and 4B where at least appropriate brightness information can be obtained (subject light is guided to the entire surface)
, VB alone to determine the photometric value so that approximately appropriate exposure is performed.

That is, in this case, a photometric value (2) of 0 is determined using the following arithmetic expression (2), with only the brightness signals VA and VB of the areas 48 and 4B indicating the brightness of the central area as symmetry.

VO= (to V+VB) /2
...■ As for the circuit operation, first of all, the interchangeable lens (
In this case, an H level voltage is output from the discrimination circuit S based on the lens type information signal stored in the circuit CPU on the all-round fisheye lens side, and the control voltage at the control terminal C/in becomes H level. Therefore, the voltage V
The control voltage of the analog switch 33 that conducts the average value of A and VB becomes H level, and the voltages VA and VB
, V, the control voltage of the analog switch 32 which makes the average value conductive is set to L level by the inverter 31. Therefore, in this case, the output voltage 0 from the operational amplifier 34 is (VA+VB)/2.

FIG. 6 shows a circuit as a specific example of the discrimination circuit S shown in FIG. In the diagram, 40 is the base! I! It is a reference voltage generation circuit that outputs the voltage ■rl, and 42 is a comparator. The comparator 42 has a reference voltage Vr,
and the lens type information signal 44 (voltage level signal) output from the circuit CPU on the interchangeable lens side. When voltage 44>voltage VrI, an H level output is generated, and conversely, when voltage 44>voltage VrI, an H level output is generated. When Vr, an L level output is generated. All types of interchangeable lenses have a built-in circuit CPU, and based on the memory information in this circuit CPU,
In the all-round fisheye lens, the lens type information signal 44 supplied from the circuit CPU to the discrimination circuit S is set to H level (reference voltage Vr
For other lenses, the information signal 44 is set to an L level (a voltage level lower than the reference voltage Vr).

Next, a second embodiment of the present invention will be described based on FIGS. 7 and 8.

Note that the same components as those in the first embodiment described above are denoted by the same reference numerals, and detailed explanations are omitted.

In FIG. 7, 117 is a reference voltage generation circuit located on the interchangeable lens side, and the reference voltage VF is transmitted to the camera body side through a connector contact 118. 113-116
is the peripheral area 4C.

The electrification VC generated from the logarithmic compression circuits 16 to 19 of luminance information in ~4C4, ~■C4 is compared with the reference voltage VF, and the luminance information from the logarithmic compression circuit 108 of the intermediate area 4B adjacent to the peripheral area is compared. The generated voltage VB or the voltages VC2 to ■C generated from the logarithmic compression circuits 109 to 112
2, and output each v c from output terminals 01 to 04.
, '~vc4'. FIG. 8 shows the configuration of the selection circuit 109 as a representative example. In the figure, 125 is a reference voltage generation circuit that generates the reference voltage Vr, and 126 is a comparator, which compares the voltage value of the reference voltage Vr inputted to the positive phase input terminal and the input terminal 113 inputted to the negative phase input terminal. Comparing with the voltage value VF, Vr >
In the case of VF, an H level voltage is generated from the output terminal, and V
When r<VF, an L level voltage is generated from the output terminal. Reference numerals 127 and 128 designate 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. 129 is an inverter.

Reference numeral 130 is an operational amplifier, and its output terminal and negative phase input terminal are connected and used as a voltage follower, and the output terminal voltage of the operational amplifier 130 is equal to the voltage at the positive phase input terminal regardless of the circuit state after the output terminal voltage. be done.

In FIG. 8, when Vr>VF, the comparator 12
6 outputs an H level voltage, the analog switch 127 becomes conductive, and 128 becomes open, so the voltage ■C1 manually applied from the input terminal 112 is input to the positive phase input terminal of the operational amplifier 130. operational amplifier 13
A voltage vC1 is output from the output terminal 01 via the voltage VC1.

On the other hand, when Vr<VF, an L level voltage is output from the comparator 126, so the analog switch 127 is open and the analog switch 128 is conductive. The generated voltage VB is inputted manually, and the voltage VB is output from the output 401 via the operational amplifier 130.

The reference voltage VF on the LENS side in Fig. 3 is set so that Vr<VF when the interchangeable lens is a full-circle fisheye lens, and set so that Vr>VF when the interchangeable lens is a full-circle fisheye lens. .

Therefore, the voltages v c,' to ■C4' output from the selection circuits 113 to 116 are all voltages VB when a full-circle fisheye lens is attached, and when a lens other than a full-circle fisheye lens is attached, the voltages are respectively VC1~VC4
becomes. In FIG. 4, 119 to 124 are resistors having the same resistance value, and voltages VA, VB, vc
, ', vc2', vc, ', VC4'. Reference numeral 132 denotes an operational amplifier, whose output end and anti-phase input end are connected, and is used as a voltage follower. The output voltage of this operational amplifier 132 ■0
(Photometric value) outputs a voltage according to the type of interchangeable lens.

(1) When a full-circle fisheye lens is attached, the voltage v c,'=
VC2'=VC3'-=VC4'=VB, and the photometric value V0 is expressed by the following equation.

VO= (VA +5VB)/6...
-■ In this case, the amount of light received in the peripheral areas 4C3 to 4c4 in FIG. 2 is drastically reduced, causing an exposure error, so the photometric value of the adjacent light receiving area (intermediate area) 4B is replaced.

(2) Voltage V when wearing a lens other than a full-circle fisheye lens
C1' = 'V C1, V C2' = V C2, V
C3'=V 03. Since V (:4' = V Cs), the photometric value V0 is expressed by the following equation.

VO= (VA +VB +VC, +VC, +VC3+
V Ca ) / 6...
・■ In this case, since the peripheral area and 4G, ~404, can be photometered, calculations can be made using all outputs.

In addition, in the above-mentioned first and second embodiments, when an interchangeable lens other than a full-circle fisheye lens is attached to the camera body,
Simply calculate the brightness signals (voltages) of the entire subject area VA, VB,
The photometric value was obtained by averaging the VC, but for example, the brightness signals VA and VB of the central areas 48 and 4B and the peripheral areas 4C1 to 404
When it is detected that there is a large difference in brightness from the brightness signal VC of
When it is detected that the summer sky or the sea is in the field of view, or when it is detected that a dark background is in the field of view, it is possible to perform highlight control correction or shadow control correction. This is effective for obtaining more accurate exposure.

Further, in the first and second embodiments described above, the central areas 4A and 4B of the object field are divided into two, but they may be combined into one.

[Effects of the Invention] As described above, the present invention can provide a photometric device that can obtain appropriate photometric values even when a full-circle fisheye lens is used.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical system when the present invention is applied to a single-lens reflex camera. FIG. 2 is an explanatory diagram showing a plurality of photometric areas in the light receiving section of FIG. 1. FIG. 3 is a circuit diagram of a photometric device as a first embodiment. FIG. 4 is a detailed circuit diagram of the peripheral brightness calculation circuit shown in FIG. 3. FIG. 5 is a detailed circuit diagram of the selection circuit of FIG. 3. FIG. 6 is a circuit diagram showing a specific example of the discrimination circuit shown in FIG. 3. FIG. 7 is a circuit diagram of a photometric device as a second embodiment. FIG. 8 is a detailed circuit diagram of the selection circuit of FIG. 7. 48, 4B, 411:I, 4C2, 4Cs, 4C4-11111 Light-receiving areas, S----1 Discrimination circuit.

Claims (2)

[Claims] (1) A light-receiving means comprising a plurality of light-receiving units that divides the field into at least two regions, a central region at the center and a peripheral region outside the central region, and obtains region brightness information for each of the plurality of regions. and, based on the area brightness information obtained by the light receiving means,
and a photometric value calculation circuit for calculating a photometric value, and in which the light receiving means receives field light transmitted through an interchangeable lens, whether or not at least a full-circle fisheye lens is attached as the interchangeable lens. a discriminating means for discriminating;
brightness information correction means for replacing the area brightness information of the peripheral area with the value of the area brightness information of the central area when the discrimination means determines that the all-round fisheye lens is attached. A photometric device characterized by: (2) Light-receiving means comprising a plurality of light-receiving sections that divides the field into at least two regions, a central region at the center and a peripheral region outside the central region, and obtains region brightness information for each of the plurality of regions. and, based on the area brightness information obtained by the light receiving means,
and a photometric value calculation circuit for calculating a photometric value, and in which the light receiving means receives field light transmitted through an interchangeable lens, whether or not at least a full-circle fisheye lens is attached as the interchangeable lens. a discriminating means for discriminating;
When the discrimination means determines that a full-circle fisheye lens is attached, photometric value calculation correction is performed to obtain the photometric side using only the area brightness information of the central area without using the area brightness information of the peripheral area. A photometric device comprising: means.