JPS5839387Y2 - digital exposure meter - Google Patents

Description

[Detailed explanation of the idea] This invention is a light meter that measures the amount of exposure of the camera.

In particular, the present invention relates to a digital exposure meter that converts an analog value into a digital value and calculates an appropriate exposure amount based on the digital value.

Conventionally, many applications have been filed regarding methods for calculating the exposure amount for photography.

Among these, the main exposure calculation methods are broadly classified into the following types.

That is, (1) a method of calculating the aperture value of the photographing lens as a calculation result of the brightness of the subject, the film sensitivity, and the shutter speed.

(2) A method of calculating the shutter speed value as a calculation result of the brightness of the subject, the film sensitivity, and the aperture value of the photographic lens.

(3) A method of calculating the exposure value of the subject based on the calculation results of the subject's brightness and film sensitivity.

Each of the above-mentioned methods has its own characteristics and has been put into practical use, but they also have drawbacks.

In method (1) above, since you are given the freedom to select the exposure time arbitrarily in advance, it is possible to shoot fast subjects such as snapshots or moving objects, or shooting conditions where there is a high possibility of camera shake such as telephoto shooting. Below, you can take into account the movement of the subject and camera shake by selecting a fast shutter speed, but when it comes to depth of field, it is possible to take into consideration the shutter speed that has been set in advance. Since the depth of field is determined by the aperture value calculated by Therefore, it cannot be said to be an appropriate exposure control method.

In addition, method (2) above is completely opposite to method (1) above, and can be used to photograph subjects with depth, such as landscapes and still life, and to use depth of field to create bokeh. For subjects you want to take advantage of, you can consider the depth of field, but on the other hand, the exposure time is not up to the photographer's discretion, so when photographing fast-moving subjects or hand-held photography, When a long exposure time is calculated as a result of arithmetic control, if you take a picture with the calculated shutter speed, you may end up with an undesirable result such as a blurred picture. This is not an appropriate exposure calculation method when shooting hand-held.

In addition, in method (3) above, the exposure value is calculated, which is the element that determines the shutter speed and aperture value, so when actually shooting, the shutter speed and aperture value are calculated. However, method (3) alone has drawbacks such as the inability to actually set photographing conditions.

In the end, in methods (1) and (2), the shutter speed,
In other words, since exposure time and aperture value each have the property of giving different visual effects, it is not limited to giving priority to only one of the two elements and automatically calculating the other element. Therefore, it is desirable to be able to freely select and prioritize shutter speed and aperture value depending on the photographer's intention at the time.

In view of this situation, a switching means is provided in the calculation mechanism of the exposure meter, and the aperture value is calculated in response to the brightness of the subject by setting the film sensitivity, shutter speed, etc. in advance according to the condition of the subject. An exposure meter has been proposed in which the shutter speed is calculated in response to the brightness of the subject by setting the film sensitivity, aperture value, etc., but this calculation is performed using an analog electric circuit. Because it depends on have.

Regarding the method (3), there are broadly two types of methods.

That is, there are two types of photometry: spot photometry, which measures only one point on the subject to obtain an exposure value, and average photometry, which measures each part of the subject and calculates the average value.

This photometric method also has its own drawbacks and advantages, similar to cases (1) and (2).

In other words, spot metering allows you to focus on one point on the subject, so if the subject is just one point, you can get a good exposure without being affected by the brightness of the surrounding area, but if the subject is over a wide area, only one point can be measured. This metering cannot provide the correct exposure for the entire image.

Moreover, in average photometry, the result is completely opposite.

In this respect, there are devices that can implement the differential photometry method, but in this case, the photometry results are processed using analog calculations, so the calculation circuit becomes complex and the photometry accuracy decreases, among other disadvantages. have.

As mentioned above, the exposure meter that calculates the amount of exposure in a camera is capable of calculating both the aperture value and the shutter time, and the light metering methods include spot metering, average metering, and double-sided light metering. It would be desirable to be able to use the method selectively.

In view of this point, in the present invention, the exposure meter is constructed with a digital electric circuit that can be integrated, and the control circuit is equipped with a ROM (read memory) that executes microprograms.
The present invention provides a digital exposure meter that eliminates the above-mentioned drawbacks by making it possible to arbitrarily select various exposure amount calculations and light metering methods by employing sequence control means such as (only memory). be.

Next, the digital exposure meter according to the present invention will be explained.

Fig. 1 is a block diagram showing an embodiment of a digital exposure meter according to the present invention, where SPC is a light receiving element, opi is an operational amplifier, and Dl is a log diode to form a known photometry circuit to measure the light of the subject and logarithmically compress it. Outputs a voltage corresponding to the subject brightness.

PG is a pulse oscillator that sends a clock pulse with a constant period to a shift register AR, which will be described later, in synchronization with the start of photometry.
tell to.

L is a latch circuit, and DA is a digital-to-analog converter consisting of a known delay circuit or the like, which generates a voltage corresponding to the number of clock pulses input to register AR.

OF2 is a comparator connected to the operational amplifier OP1 and the output end of the digital-to-analog converter DA.

AR, BR, CR are shift registers, MIR, M3R
, M4R is a memory register and is an arithmetic circuit AC which will be described later.
It is connected to the.

Among these registers, AR is a register that stores calculation results such as exposure values, and BR and CR are used to temporarily store the contents of register AR and transfer data to be input to calculation circuit AC.

The memory register MIR has an RA part that stores the cumulative total and average value of photometric values, and an RN part that stores the number of photometric values.

Further, M3R is for storing the shutter speed value, and M4R is for storing the aperture value.

Arithmetic circuit AC is an adder ADD that adds the contents of registers AR, BR, CR, and MIR.

A divider Di that divides the contents of registers BR and CR, an indigo circuit muA'1 that multiplies the Ev value input to register AR by 2E, a multiplier muA2 that multiplies the contents of registers BR and CR. There is a root circuit RuT that routes the contents of register AR.

(2) is a determination circuit connected to the memory register MIR and the register AR, and determines whether photometry has already been performed during exposure calculation.

The ROM is a sequence control circuit that controls each of the above-mentioned circuits according to a program installed in advance.

K is a keyboard, and the program contents of the ROM are selected by keys arranged on the keyboard.

RU is an inverting circuit controlled by the output of the discrimination circuit ■.
Outputs the reciprocal of the contents of register AR.

Figure 2 is an external view of the keyboard of the digital exposure meter according to the present invention.O~9 and ・ are numeric keys for inputting shutter speed and aperture value, T and ↑ keys are shutter speed data, and 9F is for inputting shutter speed and aperture value. The 1Ev key is a photometry key that converts the program contents of the ROM shown in the first diagram into photometry calculations.

The H key is the average metering key that selects the program content for calculating the average of photometric values, the A key is the calculation key that selects the program that calculates the aperture or shutter speed value, and the DIN is the digital switch for setting the film sensitivity. It is.

The LED is the display means shown in the first diagram.

Next, the operation of one embodiment of the digital exposure meter according to the present invention will be explained.

To perform photometry, press the photometry key Ev in Figure 2.
, OM is selected, and a voltage corresponding to the subject brightness received by the light receiving element SPC is generated at the input terminal of the operational amplifier OP1 according to the program, and this voltage is applied to the log diode D1 and the operational amplifier OP1.
A voltage corresponding to the subject brightness Bv that has been logarithmically compressed by the voltage is transmitted to one input terminal of the comparator OP2.

Further, a control signal is transmitted to the pulse oscillator PG by the ROM to drive the pulse oscillator PG, and the pulse oscillator PG generates a pulse.

The pulse is stored in register AR and transmitted to DA converter DA via a latch circuit.

The DA converter DA generates a voltage corresponding to the number of pulses stored in the register AR, and transmits it to the other input terminal of the comparator OP2, and the comparator OP2 compares the voltage output by the DA converter with the operational amplifier OPI. The voltage corresponding to the subject brightness outputted by is compared with the voltage corresponding to the subject brightness, and when the two voltage values match, a photometry end signal is transmitted to the pulse generator PG, and the operation of the pulse generator is stopped.

When the number of pulses corresponding to the subject brightness Bv value is counted in the register AR by the above-described operation, a control signal is transmitted to the register AR by the ROM, and the Bv value information stored in the register AR is transferred to the register CR.

Next, by operating the digital switch DIN shown in the second diagram, the logarithmically compressed and digitized film sensitivity Sv is transferred to the register AR, and the Sv value and the subject brightness value Ev transferred to the register CR are added to the adder ADD.
is added and transmitted to register AR.

By this operation, the exposure value Ev value is transmitted to the register AR.

When the Ev value is transmitted to the register AR, a control signal is transmitted from the ROM to the register AR, the exposure value Ev value is transmitted to the register BR, and the memory register M
The Ev value stored in the Ev accumulator RA part of the IR is called by the adder ADD and added together with the Ev value from the register AR by the adder ADD, and the added value is transmitted to the register AR and added to the RA part of the memory register MIR.
transferred to the part.

In this embodiment, since photometry is performed for the first time, no Ev value is input to the RA part of the memory register MIR, and the Ev value is input to the RA part for the first time by the above-described operation.

When the Ev value is input to the RA part, a control signal is transmitted to the register AR by the ROM, and the register AR is set to 11.
, is input, and the photometry number stored in the photometry number part RN part of the memory register MIR is called out, added by the adder ADD, and stored in the memory register M.
Transferred to the RN part of the IR.

Since this is the first photometry, the number of measurements has not been entered in the RN part of MIR, and the number of measurements is input into the RN part for the first time by this operation.

When the number is input to the RN part, a control signal is transmitted from the ROM to the register BR, and the Ev value stored in the register BR is transmitted to the register AR, and transmitted to the display circuit LED consisting of an LED etc. via the decoder driver DB, and the exposure is Display the value.

Next, a case where average photometry is performed will be explained.

When the above-mentioned photometry is repeated several times, the RA part of the memory register MIR has the sum of the exposure values Ev measured so far, and the RN part of MIR has the number of photometers input. If the Ev average key shown in the second figure is pressed, the average program programmed in the ROM is selected and the corresponding RO
A control signal is transmitted to the RA part and RN part of the memory register MIR by M, and the sum of Ev values stored in the RA part is transferred to the temporary register AR, and the sum of Ev values is transferred to the register BR via the register AR. do.

Also, the total number of photometric measurements stored in the RN part of the memory register MIR is transmitted to the register AR.

When the above operation is completed, a control signal is transmitted from the ROM to the registers AR and BR, and the total number of photometric measurements input to the register AR is transferred to the register CR.

At the end of the operation, the ROM transfers the control signal to register B.
Ev transmitted to R and CR and stored in register BH
The sum of the values and the sum of the numbers stored in register CR are divided by divider Di, and the result is stored in register A.
This will be communicated to R.

By this operation, the average value of all exposure values is stored in the register AR.

When the average value of the Ev values is stored in the register AR, a control □□ signal is transmitted from the ROM to the register AR, and the average value of the Ev values is transferred to the RA part of the memory register MIR, and is also transmitted via the decoder driver DB. The exposure value is transmitted to the display circuit LED and displays the exposure value.

Next, a case in which exposure calculation is performed will be explained.

When calculating the shutter time, the desired aperture value is pressed down using the number keys shown in the first diagram, and the aperture value A is input into the memory register M4R by pressing the F key.

Next, by pressing the calculation key A shown in the second diagram, the RO
The arithmetic program set in M is selected, and the control signal 11 from the ROM is transmitted to one input terminal of the discriminator circuit ■, and the number of photometry inputs to the RM part of the memory register MIR is transmitted to the other input terminal of the discriminator circuit ■. When the value input to the RN part is less than 21, that is, when photometry has not been performed even once, a signal is transmitted from the discrimination circuit ■ to the ROM, and as described above. Photometry is performed using a photometry program.

As a result, the Ev value is input to the register AR through the process described above, and the register AR is input by the control signal from the ROM.
The Ev value of is calculated as 2 to the EV power in the vote circuit mu71.

The 2 to the power of EV, ie 2EV, is transferred to register BR.

When the 2EV value is input to the register BR, a control signal is transmitted from the ROM to M4R, the A value is transferred to CR via the register AR, and the zEV value input to the BR and the zEV value input to the divider Di are input to CR. The A value is input and division is performed.

The resulting 2 EV /A value is transferred to register BR via register AR.

When the 2 EV /A value is transferred to the register BR, the divider Di again inputs the 2 EV /A value to the register BR.
The EV/A value is divided by the A value input into the register CR, and the 2E/A2 value, ie, the lower value, is input into the register AR.

When the clay figurine is input to the register AR, the discrimination circuit ■
is input and compared with the above-mentioned "1", and when the lower value is larger than 1, it is displayed on the LED as in the case of photometry described above.

Further, when the lower value is smaller than 1, the reciprocal is taken by the inverting circuit RU and displayed on the LED.

As a result, the constantly displayed value becomes a number greater than or equal to 1, and the photographer can easily read the shutter time.

On the other hand, when calculating the aperture value, press the number key with the desired shutter speed value in the same way as when calculating the shutter speed, and then press the A key to register M3 in the memory register.
The T value is input to R, and 2 is input to register BR as described above.
F and V values are input.

Next, the 2BV value is transferred to register CR via register AR, and multiplier circuit muA2 transfers the 2BV value to register BR.
2EV is multiplied by the T value of the register CR, and the resultant ZEVXT value is input to the register AR.Then, a route is taken by the route circuit RuT, m, that is, the F value is input to the register AR, and is displayed by the LED as described above.

In addition, in the above process, when comparing 11 with the number of photometry input in the memory register RN part in the discrimination circuit ■, if the value of the RN part is thicker than i st, if photometry has already been performed. Memory register MIR
Since the Ev value is input to the RA part of
The Ev value is transferred to the register AR by a control signal from the register AR, and the above calculation is performed using the Ev value that has already been photometered without performing new photometry.

As mentioned above, in the digital exposure meter according to the present invention, the exposure meter is constructed from a digital electric circuit that can be integrated, and the control circuit employs a sequence control means such as a ROM that executes a microprogram. Therefore, various exposure amount calculation and photometry methods can be arbitrarily selected and adopted, which brings about great effects in a digital exposure meter.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the digital light meter according to the present invention, and FIG. 2 is an external view of the keyboard of the digital light meter according to the present invention. AR, BR, CR...Register, MIR. M3R, M4R・・・Memory register, AC
... Arithmetic circuit, ROM ... Sequence control circuit, K ... Keyboard, ■ ...
Discrimination circuit, OPl... operational amplifier.

Claims (1)

[Scope of claim for utility model registration] In a digital exposure meter that calculates the appropriate exposure amount by converting analog quantities such as subject brightness into digital quantities. AD conversion means converts the logarithmically compressed subject brightness information output of the photometry means that measures the subject light into a digital quantity, and sets the film sensitivity value as a logarithmically compressed digital quantity, and also sets the aperture value, shutter speed value, etc. a photographing information setting means for setting various photographic information as digital quantities; a plurality of register means for storing the outputs of the AD converting means and the photographing information setting means, and connected to each other so that the stored contents can be transferred to each other; A calculation means connected to one register means and capable of performing operations such as at least addition and division, and a control signal for controlling the transfer of the storage contents of the register one means and the calculation of the calculation means in a series of order. and a sequence control means that stores the number of photometry in a part of the register, and a part that stores the number of photometry in a part of the register, and a part that stores the sum of the exposure values obtained through the calculation means or the sum total in each photometry of the number of photometry. A part for storing an average exposure value divided by the number of photometry times is provided, and further, when calculating a shutter time value and an aperture value, a part for determining the presence or absence of photometry in response to the output from the number of photometry storage part. A digital exposure meter characterized in that a discrimination means is provided which operates to cause the sequence control means to output a photometry and exposure value calculation control signal in accordance with a discrimination result.