JPH06100497B2 - Camera with photometric device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a camera having a photometric device that divides a photometric region into a plurality of regions and obtains a photometric value based on luminance information for each of the plurality of regions. Particularly, it relates to correction when an all-round fisheye lens is attached as an interchangeable lens.

[Prior art]

Conventionally, various photometric devices have been proposed in which a field is divided into a plurality of regions, light is measured for each region, and proper exposure is given to a photographic screen by using the plurality of photometric luminance values.

As an example of the photometric device, Japanese Utility Model Publication No. 51-9271 (Japanese Patent Laid-Open No. 54-1230)
There are No. 30 etc.

These photometric devices measure the brightness of each of the divided regions of the object scene, and select and calculate the conditions under which the proper exposure of the screen can be obtained 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 photometry, which is generally used as a conventional camera photometry method, measures the entire screen with a single light-receiving unit, so in a backlit scene, etc. Was underexposed.

In recent years, some commercialized cameras have adopted a method in which the field of view is divided into multiple parts for photometry, and the average of each photometric value is taken as the photometric value for the entire screen. It has been recognized that the photometric values of a bright background and a dark main subject in a scene are averaged to reduce the degree of underexposure of the main subject. Also in this multi-division average photometry, the prerequisite is that the brightness of each divided area is accurately measured.

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

In the all-round fisheye lens, which is a type of interchangeable lens, the image circle is inscribed on the short side of the screen, so the subject light does not reach the periphery of the long side of the screen at all, so photometry in the peripheral area of the screen is also impossible. Become.

[Object of the Invention]

The present invention is a photometric device capable of dividing a photometric region to receive light and independently measuring at least a central region of a screen and a peripheral region thereof. A camera having a photometric device capable of obtaining an appropriate photometric value even when an all-round fisheye lens is attached. The purpose is to provide.

In order to achieve the above-mentioned object, the present invention is provided with a discriminating means for discriminating whether or not at least a full-circle fish-eye lens is mounted as an interchangeable lens, and when discriminating the mounting of the full-circle fish-eye lens by this discriminating means, the periphery is A camera having a photometric device for replacing area brightness information of an area with another value is characterized.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an optical layout diagram of a photometric system for realizing the present invention with a single-lens reflex camera. In the figure, 1 is a focusing screen, 2
Is a penta roof prism, 3 is an imaging lens, 4 is a light receiving part,
Reference numeral 5 is an eyepiece lens, 6 is an interchangeable photographing lens, 7 is a quick return mirror, and 8 is a film. In FIG. 1, the subject image formed on the focusing screen 1 by the taking lens 6 is
The imaging lens 3 guides and forms an image on the light receiving portion 4 to perform photometry.

FIG. 2 is an explanatory diagram of the light receiving surface of the light receiving section 4 shown in FIG. In the figure, 4A is a central area of the object scene, 4B is an intermediate area having a shape surrounding the area 4A, and 4C ₁ , 4C ₂ , 4, 4C ₃ and 4C ₄ are peripheral parts of the object scene. Each of the divided light receiving part regions for receiving light in each region is shown. The central region referred to in the present invention is a region obtained by combining the regions 4A and 4B, and the peripheral region is the region 4C.
_The combined area from _{1 to} 4C ₄ is shown.

The area shown by the dotted line in FIG. 2 shows the shooting range when the all-round fisheye lens is mounted as an interchangeable lens. This area is a circle that is almost inscribed in the short side of the entire photographable area in one frame of the film 8, and the periphery (outside the area) is not exposed at all. Although the actual size of the entire image-capturing area of the film 8 and the entire area of the light-receiving unit 4 are different, it is assumed that the light-guiding range of the object field is substantially the same.

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

In FIG. 3, 8,9,10,11,12,13 are the six areas 4 mentioned above.
A, 4B, 4C ₁ , 4C ₂ , 4C ₃ , 4C ₄ silicon photodiodes (SPD) corresponding to the photocurrent iA, iB, iC ₁ , iC ₂ , iC ₃ , Generate iC ₄ . 14 to 19
These photocurrents are logarithmically compressed to VA, VB, VC ₁ , VC ₂ , VC ₃ , VC ₄
Is a logarithmic compression circuit that outputs a voltage value Voltage VA, VB,
_{VC 1, VC 2, VC 3} , VC 4 is constant _{a 1, a 2, a 3} , a 4, a 5, a 6 (0), b
(> 0) and photocurrents iA, iB, iC ₁ , iC ₂ , iC ₃ and iC ₄ can be expressed as follows.

VA = a ₁ + b lniA VB = a ₂ + b lniB VC ₁ = a ₃ + b lniC ₁ VC ₂ = a ₄ + b lniC ₂ VC ₃ = a ₅ + b lniC ₃ VC ₄ = a ₆ + b lniC ₄ However, a ₁ , a ₂ , a ₃ ,, a ₄ ,, a ₅ , a ₆ are included in the logarithmic compression circuits 14 to 19 so that VA = VB = VC ₁ = VC ₂ = VC ₃ = VC ₄ when the brightness of each area is equal. Is set in advance.
20, the output voltage VC ₁ of the logarithmic compression circuit _{16~19, VC 2, VC 3,} VC 4
To the input terminals I ₁₁ , I ₁₂ , I ₁₃ , and I ₁₄ , respectively, to calculate the brightness values of the peripheral portions 4C _{1 to} 4C ₄ of the object scene, and output the voltage VC from the O ₁ output terminal.
Is a peripheral luminance value calculation circuit that outputs FIG. 4 shows the configuration of the peripheral luminance value calculation circuit 20.

In FIG. 4, 23, 24, 25 and 26 are resistors having the same resistance value, and are for averaging the voltages VC ₁ , VC ₂ , VC ₃ and VC ₄ . Reference numeral 27 is an operational amplifier, whose output end and anti-phase input end are connected, and which is used as a voltage follower.
As the output terminal voltage of the operational amplifier 27, a voltage equal to the positive phase input terminal voltage is output regardless of the circuit state after the output terminal. The output VC of the operational amplifier 27 is VC = (VC ₁ + VC ₂ + VC ₃ + VC ₄ ) / 4, and this is output from the O ₁ output terminal.

As described above, the peripheral brightness computing circuit 20 outputs the average value of the brightness of the peripheral part of the object field as VC from the O ₁ output terminal.

Reference numeral 21 in FIG. 3 indicates the output voltages VA and VB of the logarithmic compression circuits 14 and 15 and the output voltage VC of the peripheral brightness calculation circuit 20, respectively, as input terminals I ₂₁ , I ₂₂ and.
Input to I _23, and input the control voltage corresponding to the presence / absence of the attachment / detachment of the fisheye lens from the determination circuit S to the control terminal C / to select which of the two arithmetic expressions described later. This is a selection circuit that determines and calculates whether or not, and outputs the voltage Vo as a photometric value from the O ₂ output terminal. The configuration of the selection circuit 21 is shown in FIG.

FIG. 5 is a circuit diagram of the selection circuit 21 in FIG. 2
Reference numerals 8, 29 and 30 are resistors having the same resistance value and are for averaging the voltages VA, VB, VC or the voltages VA, VB. Reference numeral 31 is an inverter, which inverts the control voltage input to the control terminal C /. That is, the output voltage of the inverter 31 becomes L level when the control voltage is H level, and becomes H level when the control voltage is L level. 32 and 33 are analog switches, which are the average value (VA + VB + VC) / 3 of the voltages VA, VB, and VC, respectively, depending on the control voltage of the control terminal C /.
Alternatively, make (VA + VB) / 2 conductive. 34 is an operational amplifier, the output end of which is connected to the negative phase input end and is used as a voltage follower. As the output terminal voltage of the operational amplifier 34, a voltage equal to the positive phase input terminal voltage is output regardless of the circuit state after the output terminal. Output VO of operational amplifier 34
The (photometric value) is VO = (VA + VB + VC) / 3 or (VA + VB) / 2, and this is output from the O ₂ output terminal. As described above, the selection circuit 21 is the discrimination circuit S for discriminating the mounting of the all-round fisheye lens.
Which of the two arithmetic expressions is selected is determined according to the control voltage output from the output voltage VO corresponding to the arithmetic result from the O ₂ output terminal.

In FIG. 3, the discrimination circuit S discriminates whether or not the interchangeable lens mounted on the camera body is an all-round fisheye lens based on the output signal from the circuit CPU incorporated in the interchangeable lens side. The electrical communication between the camera body and the interchangeable lens is performed via the connector CN.

Next, the circuit operation of FIGS. 3 and 5 will be described.

(1) When an interchangeable lens other than the full-circle fisheye lens is attached, in other words, when it is determined that the full-circle fisheye lens is not attached; in this case, the light from the object field covers the entire area of the light receiving unit. It will be guided through, and the brightness of the entire field of view will be reduced except for the case of backlight shooting and special cases where the field of light or particularly dark objects such as the sun and the ground have entered. It is possible to obtain a photometric value that gives an appropriate exposure by averaging.

That is, the luminance signals VA, VB, VC of all the areas 4A, 4B, 4C _{1 to} 4C ₄ of the object scene are made symmetrical, and the photometric value is calculated by the following arithmetic expression.
Seeking VO.

VO = (VA + VB + VC) / 3 ... As the circuit operation, first, based on the lens type information signal stored in the circuit CPU of the interchangeable lens (in this case, other than the all-round fisheye lens) side, the L level voltage is output from the determination circuit S. It is output and the control voltage of the control terminal C / becomes L level. Therefore, the control voltage of the analog switch 32 for making the average value of the voltages VA, VB, VC conductive becomes H level by the inverter 31, and the control voltage of the analog switch 33 for making the average value of the voltages VA, VB conductive becomes L level. Therefore, in this case, the output voltage Vo from the operational amplifier 34 becomes (VA + VB + VC) / 3.

(2) When an all-round fish-eye lens is mounted as an interchangeable lens; In this case, as shown by the dotted line in FIG. Do not reach Explaining specifically with reference to FIG. 2, the field light does not reach the portion outside the circular dotted line indicating the area of the fisheye lens photographing range in the peripheral areas 4C _{1 to} 4C ₄ .
Therefore, if the photometric value is simply obtained by using the luminance signal VC (an average of VC _{1 to} VC ₄₎ obtained from the peripheral regions 4C _{1 to} 4C ₄ , it will be an erroneous value. This is because, for example, assuming that the area in which the subject light is guided in the peripheral regions 4C _{1 to} 4C ₄ is 1/3, the brightness corresponding to the 1/3 area in which this light is guided is calculated by the logarithmic compression circuit in FIG. VC ₁ = a ₃ + bln i
This is because the voltage information VC _{1 to} VC ₄ becomes luminance information of about 1/3 voltage due to C ₁ ).

Therefore, at least appropriate exposure is performed by obtaining a photometric value using only the luminance signals VA and VB in the areas 4A and 4B where at least appropriate luminance information is obtained (the subject light is guided to the entire surface).

That is, in this case, the regions 4A, 4 indicating the brightness of the central region
Using only the brightness signals VA and VB of B as contrasts, the photometric value VO is obtained by the following arithmetic expression.

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

FIG. 6 shows a circuit as a specific example of the discrimination circuit S shown in FIG. In the figure, 40 is the reference voltage Vr ₁
Is a reference voltage generating circuit, and 42 is a comparator. The comparator 42 compares the reference voltage Vr ₁ with the lens type information signal 44 (voltage level signal) output from the interchangeable lens side circuit CPU and generates an H level output when voltage 44> voltage Vr _1. On the contrary, when the voltage 44 <the voltage Vr ₁ , the L level output is generated. A circuit CPU is incorporated in each interchangeable lens, but based on the memory information in this circuit CPU, the lens type information signal 44 supplied from the circuit CPU to the discriminating circuit S in the all-round fisheye lens is at the H level (reference). The voltage level is higher than the voltage Vr ₁ ), and the information signals 44 are set to the L level (voltage level lower than the reference voltage Vr ₁ ) in the other lenses.

Next, a second embodiment of the present invention will be described with reference to FIGS. 7 and 8.

The same components as those in the first embodiment described above are designated by the same reference numerals and detailed description thereof is omitted.

In FIG. 7, reference numeral 117 is a reference voltage generating circuit on the side of the interchangeable lens, and the reference voltage VF is transmitted to the camera body side via the connector contact 118. 113-116 is the peripheral area 4C
Compared in _{1 ~4C 4} and a voltage VC ₁ to Vc ₄ and the reference voltage VF generated from the logarithmic compression circuit 16 to 19 of the luminance information, the logarithmic compression circuit of the luminance information of the region 4B of the intermediate portion adjacent to the peripheral region Ten
8 voltage or VB generated from, by selecting whether the voltage VC ₁ to Vc ₂ generated from the logarithmic compression circuit 109 to 112, VC ₁ respectively from the output terminals 01 to 04 'to Vc _4' to output a voltage of Is a selection circuit. FIG. 8 shows the configuration of the selection circuit 109 as a typical example. In the figure, 125 is a reference voltage generating circuit for generating a reference voltage Vr, 126 is a comparator, and the voltage value of the reference voltage Vr input to the positive phase input terminal and the input terminal I ₁₃ input to the negative phase input terminal. When Vr> VF, an H level voltage is generated from the output terminal, and when Vr <VF, an L level voltage is generated from the output terminal. Reference numerals 127 and 128 denote analog switches, which are conductive when the voltage applied to the control terminal is H level and open when the voltage is L level. 129 is an inverter.

Reference numeral 130 denotes an operational amplifier, which is used as a voltage follower in which the output terminal and the negative-phase input terminal are connected.
As for the output terminal voltage of 0, a voltage equal to the positive phase input terminal is output regardless of the circuit state after the output terminal voltage.

In FIG. 8, when Vr> VF, the H level voltage is output from the comparator 126, so the analog switch 127
Is conductive and 128 is open, so the voltage input from the input terminal I ₁₂ is applied to the positive phase input terminal of the operational amplifier 130.
VC ₁ is input, and the voltage VC ₁ is output from the output terminal 01 via the operational amplifier 130.

On the other hand, when Vr <VF, the L level voltage is output from the comparator 126, so the analog switch 127 is in the open state and the analog switch 128 is in the conducting state. Therefore, the positive phase input terminal of the operational amplifier 130 is connected to the input terminal I ₁₁ from the input terminal I ₁₁ . Input voltage VB
Is input and the voltage V is output from the output terminal 01 via the operational amplifier 130.
B is output.

The reference voltage VF on the LENS side in FIG. 3 is set to Vr <VF when the interchangeable lens is an all-round fisheye lens, and is set to Vr> VF when the interchangeable lens is other than the all-round fisheye lens. . Therefore, the voltage output from the selection circuits 113 to 116
VC ₁ ′ to VC ₄ ′ are all at the voltage VB when the all-round fisheye lens is mounted, and are at the voltages VC _{1 to} VC ₄ when lenses other than the all-round fisheye lens are mounted. In FIG. 4, 119 to 124 are resistors having the same resistance value, and the voltage V
It is for averaging A, VB, VC ₁ ′, VC ₂ ′, VC ₃ ′, VC ₄ ′. An operational amplifier 132 has an output terminal and an antiphase input terminal connected to each other, and is used as a voltage follower. As the output voltage VO (photometric value) of the operational amplifier 132, a voltage according to the type of interchangeable lens is output.

(1) Voltage VC ₁ ′ = VC ₂ ′ when the full-circle fisheye lens is attached
= Since it is _{VC 3 '= VC 4' =} VB, photometric value Vo is expressed by the following equation.

VO = (VA + 5VB) / 6 ... In this case, since the amount of light received by the second view of the peripheral region 4C ₁ ~4C ₄ incurs depleted exposed error, replace the photometric value of the light-receiving region (intermediate region) 4B adjacent It is a thing.

(2) Voltage VC when lens other than all-round fisheye lens is attached
_{Since 1} ′ = VC ₁ , VC ₂ ′ = VC ₂ , VC ₃ ′ = VC ₃ , VC ₄ ′ = VC ₄ , the photometric value Vo is expressed by the following equation.

VO = (VA + VB + VC 1 + VC 2 + VC 3 + VC 4) / 6 ... The 4C ₁ ~4C ₄ also peripheral region if it is possible operation using all the output because it metering.

In the first and second embodiments described above, when an interchangeable lens other than the all-round fisheye lens is attached to the camera body,
The brightness signals (voltages) VA, VB, and VC of the entire subject area were simply averaged to obtain the photometric value. For example, the brightness signals V of the central areas 4A and 4B
A, or to correct the photometric value when it is detected that the luminance difference between the luminance signal VC of the VB and the peripheral region 4C ₁ ~4C ₄ is large backlit scene, also the brightness of the peripheral area 4C ₁ ~4C ₄ When the signal VC is compared with a reference value and it is detected that the summer sky or sea is in the field, or when a dark ground plane is in the field, highlight control correction Alternatively, shadow control correction is effective for obtaining more accurate exposure.

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

〔The invention's effect〕

As described above, the present invention can provide a camera having a photometric device that can obtain an appropriate photometric value even when an all-round fisheye lens is used.

[Brief description of drawings]

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 view showing a plurality of photometric areas in the light receiving section of FIG. FIG. 3 is a circuit diagram of the photometric device as the first embodiment. FIG. 4 is a detailed circuit diagram of the peripheral brightness calculation circuit of FIG. FIG. 5 is a detailed circuit diagram of the selection circuit of FIG. FIG. 6 is a circuit diagram showing a specific example of the judgment circuit of FIG. 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 shown in FIG. 4A, 4B, 4C ₁ , 4C ₂ , 4C ₃ , 4C ₄ ...... Receiving areas, S ...... Discrimination circuit.

Claims (2)

[Claims] 1. A light receiving section comprising a plurality of light receiving sections, each of which divides a photometric area into at least two areas of a central area of a central area and a peripheral area outside the central area, and obtains area brightness information for each of the plurality of areas. Means, and a photometric value calculation circuit for obtaining a photometric value based on the area luminance information of the central area and the peripheral area obtained by the light receiving means, and the photographing light transmitted through the interchangeable lens is received by the light receiving means. In a camera having a photometric device that receives light by means, when determining that at least a full-circle fisheye lens has been attached as the interchangeable lens, and that the full-circle fisheye lens has been attached by the determining means And a brightness information correction unit for replacing the area brightness information of the peripheral area with another value. 2. A light receiving section comprising a plurality of light receiving sections for dividing the photometric area into at least two areas, namely, a central area in the central area and a peripheral area outside the central area, and obtaining area brightness information for each of the plurality of areas. Means, and a photometric value calculation circuit for obtaining a photometric value based on the area luminance information of the central area and the peripheral area obtained by the light receiving means, and the photographing light transmitted through the interchangeable lens is received by the light receiving means. In a camera having a photometric device that receives light by means, when determining that at least a full-circle fisheye lens has been attached as the interchangeable lens, and that the full-circle fisheye lens has been attached by the determining means And a 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.