JPS5919290B2 - Digital display exposure meter - Google Patents

Description

[Detailed Description of the Invention] The present invention measures the brightness of the subject surface when taking a photograph,
This invention relates to an exposure meter that digitally displays a lens aperture value corresponding to the amount of photometry.

In general, it is well known that the lens aperture value F in a camera device is given by the following relational expression, given the film sensitivity s, the brightness B of the subject surface, and the exposure time T as its determining factors.

Fo-c, /SXBXT・・・・・・・・・(1)5B
Assuming that T=, then F■(1fK......(2) τ As can be seen from equation (2), if we convert the root to the photometric amount, we can obtain a continuous line corresponding to the photometric amount. Lens aperture value can be obtained.

However, if a route conversion circuit is used for route conversion, the circuit configuration becomes complicated and the price of the device increases.

Furthermore, the lens aperture value currently set in the camera device is a common ratio JΣ, 4JΣ, or 6JΣ, except for the lens aperture value corresponding to the maximum aperture ratio of the lens set in the camera device.
It is generally set based on one of the geometric progressions of Jf (. As with variations in time, etc., this seems unnecessary if considered within the range that does not impair the photographic effect.

Therefore, the lens aperture value may be indicated in the exposure meter using any one of the geometric progressions of the common ratios. The present invention does not use a root conversion circuit, but distributes the amount of light measurement within a range of a geometric progression based on the common ratio, and digitally displays the lens aperture value corresponding to the amount of photometry using a numerical display element such as an LED. It is an exposure meter.

The present invention will be explained in detail below. FIG. 1 is a block diagram for explaining the present invention.

Reference numeral 1 denotes a photometering section that is equipped with a light receiving element and measures the brightness of the subject surface based on photographic elements (for example, film sensitivity and exposure time), and 2 is an analog quantity that is the photometry amount measured by the photometry section 1. 3 is a binary counting circuit section that counts the oscillation pulses from the A-D converter circuit 2 in binary, and 4 is a binary counting circuit that converts the oscillation pulses equal to 2n (n - 0
11, 2) is a distribution circuit section that distributes the parallel output signals based on the common ratio Ji of the lens aperture value, either 4JΣ or 6f d, and 5 is a distribution circuit section that distributes the parallel output signals corresponding to 4 This is a memory circuit section that stores lens aperture values in a geometric progression of common ratios at arbitrary memory addresses, and a display section that displays the lens aperture value selected in the memory circuit section 5 numerically using an LED or the like. It is.

In the circuit configuration, the photometric amount measured by the photometric unit 1 without using the route conversion circuit is expressed as a common ratio JΣ, 4. E or 6
An embodiment will be described in which the lens aperture value of the common ratio is distributed by a common ratio relative to the geometric progression of JΣ, and the lens aperture value of the common ratio is displayed digitally.

Here, if the common ratio is N, the lens aperture value F of the geometric progression is the lens aperture value expressed by the following formula.

First, the embodiment shown in FIG. 2 will be described in which the photometric amount is distributed by a common ratio relative to the lens aperture value in a geometric progression of the common ratio JΣ, and the lens aperture value is displayed.

The lens aperture values of the geometric progression of the common ratio JΣ are 1.00011.414, 2.012.828, 4.
The numerical sequence values are 000, 5.657...
(In order to simplify the explanation, the lens aperture value is shown as a two-digit nominal value in the numerical sequence values.)

Now, in FIG. 1, when the luminance of the subject surface is measured by the photometric section 1, the A/D conversion circuit section 2 outputs an oscillation pulse L proportional to the measured photometric amount A.

Then, it is counted by the binary counting circuit section 3 and output terminal 0 as shown in the figure.

, 0, , 02, .
Input terminals 1 of the highest level signal detection circuit 4' are connected in parallel. , 11, 12, .
transmitted to. Here, the highest level signal detection circuit 4' is
Its input terminal 1.

, 11, 12, the circuit detects which input terminal the highest signal corresponds to, and outputs an encoded signal corresponding to the terminal. This is a circuit with a corresponding function. Therefore, the most significant signal of the counting signals from the binary counting circuit section 3 is detected by the most significant signal detection circuit 4', and the encoded signal corresponding to the most significant input terminal is transmitted to the memory circuit section 5. A storage address is selected according to the encoded signal, and the lens aperture value stored corresponding to the storage address is displayed. A description will be given of how the photometric quantity is distributed in a geometric progression of common ratios Ji through the series of circuit operations described above.

It is well known that each of the parallel output terminals of the binary counting circuit section 3 corresponds to a numerical value of 2n (n=O, 1, 2...), which is a common ratio. It is a geometric progression of 2.

Therefore, detecting the most significant signal among the count signals output to the output terminal means that all the count signals below it depend on the most significant signal, for example. If ゛゜1'' or ``0'' is used as a transmission signal, ``1'' means that there is a transmission signal, and ゛゜0'' means that there is no transmission signal, then the count signal of 8 is 1000 in binary, which is 9)2. In the binary number 1111 of 1001 and 15, the highest signals of the count signals of 8, 9, and 15 are detected equally.In other words, the count value 2n of the parallel output terminal of the binary counting circuit section 3 is detected. This is the common ratio 2
It becomes a geometric progression. Therefore, the photometric quantity K is distributed in a geometric progression with a common ratio of 2, and Equations (4 and (3)) hold true.

To explain with a specific example, if there are seven oscillation pulses proportional to the photometric amount measured by the photometric circuit section 1 and converted by the A-D converter circuit section 2, then the binary counting circuit section 3 A counting signal 111 is outputted to the output terminal of.

Then, the most significant signal detection circuit 4' of the distribution circuit section 4 detects that the most significant digit of the count signal corresponds to 22, and an encoded signal is outputted to select the third digit of the memory circuit section 5. Then, the lens aperture value 2.0 stored in the memory circuit section 5 is called up, and the lens aperture value 2.0 is displayed on the display section 6. Further, if the measured photometric amount is very small and the oscillation pulse of the A-D conversion circuit section 2 is zero, the highest signal detection circuit 4' detects that there is no count signal from the binary number circuit section 3, An encoded signal for selecting address 0 of the memory circuit section 5 is outputted, and 0.0 is displayed on the display section 6. Also, instead of displaying 0.0, the encoded signal is used to display under (meaning that the amount of photometry is very small).
By providing , it is also possible to express under.

Next, the photometric amount is distributed by the common ratio relative to the lens aperture value in the geometric progression of the common ratio "J", and the third part displays the lens aperture value.
The embodiment shown in the figure will be explained.

The lens aperture values of the geometric progression of the common ratio 4JΣ are 1.000, 1.189, 1.414, 1.682,
2.000, 2.378, .

(To simplify the explanation, the lens aperture value is shown as a two-digit nominal value). and the output terminal of the binary counting circuit section 3,
The input terminal of the highest signal detection circuit 4' of the distribution circuit section 4 is I as shown in FIG.

is 0. , 11 is 0-1 and 00 is the gate circuit ANDI
is logically AND-connected at , and its output terminal and 12 are 01
And 13 is 0. and 01 are logically AND-connected in a gate circuit AND2, and their output terminals are connected in the same manner as described above. Distribution circuit section 4 with the configuration shown in FIG.
The operating principle of the highest level signal detection circuit 4' is the same as that described in FIG. 2, so a description thereof will be omitted.

In the configuration shown in FIG. 3, it will be explained how the photometric quantity is distributed by the common ratio relative to the lens aperture value of the geometric progression of the common ratio 4JΣ. (From equation (3), therefore, according to FIG. 3, the input terminal I of the highest level signal detection circuit 4'.

, ll, l2...... have a binary counting circuit section 3.
The output terminals 0-1, 01, 00, 01 are connected directly or via gate circuits ANDI, AND2, .

, I, , l2 . . . , it can be considered that the above numerical values are transmitted using the following common ratio. That is 1
.

There is a relationship between Numerical values are transmitted between the input terminals in different geometric progressions with ratios of 1.50 and 1.33. In the device of the present invention, I between the input terminals. It is considered that the numerical value is transmitted using one common ratio in which ~11 and ~12~ are equal.
In other words, assuming that it is transmitted by the geometric mean common ratio of the common ratios obtained by equations (6) and (7), the geometric mean common ratio is
becomes.

Here, to describe the error that occurs between C6) and the common ratio obtained by equation (7), there is a photometric difference of -0.16 eV between the common ratios 1 and 50 obtained by equation (6). Furthermore, although there is an error of +0.18 eV between the common ratio of 1.33 obtained with the It can be seen as a geometric progression of ratios Ji.

In other words, the photometric amount K is distributed by the common ratio of J, and K
=J2n(n=0, 1, 2......) as (
5) By substituting into the equation, it can be seen that the right-hand side holds true.

To explain with a specific example, if there are seven oscillation pulses proportional to the photometric amount measured by the photometric circuit section 1 and converted by the A-D converter circuit section 2, then the binary counting circuit section 3 A counting signal 111 is outputted to the output terminal of.
The topmost signal detection circuit 4' of the distribution circuit section 4 has 11
1 is transmitted, it is detected that the input terminal 13 is at the highest level, and an encoded signal for selecting address 4 of the memory circuit section 5 is output. Then, an encoded signal for selecting address 4 of the memory circuit section 5 is output. Then, the lens aperture value 1.7 stored in the memory circuit section 5 is called up, and the lens aperture value 1.7 or less is displayed on the display section 6.

The 0.0 display is the same as the explanation in FIG. 0.0 is not displayed in this case as well.

Next, an embodiment shown in FIG. 4 will be described in which the photometric amount is distributed by a common ratio relative to the lens aperture value in a geometric progression with a common ratio of 6J, and the lens aperture value is displayed.

The lens aperture value of the geometric progression with a common ratio of 6J is from equation (3): 1.000, 1.122, 1.1260) 1.41
The numerical sequence values are 4, 1.5687, 1.782, .

(To simplify the explanation, the lens aperture value is shown as a two-digit nominal value). The output terminal of the binary counting circuit section 3 and the input terminal of the highest signal detection circuit 4' of the distribution circuit section 4 are connected to I as shown in FIG.

is 0. , 11 is 0-2 and 00 are gate circuits ANDI
is logically AND-connected at , and its output terminal and 12 are 0-
1 and 0. are logically AND-connected in the gate circuit AND2, and are connected to the output terminal thereof in the same manner as described above. The principle of operation of the highest signal detection circuit 4' of the distribution circuit section 4 in the configuration shown in FIG. 4 is the same as that described in FIG. 2, so a description thereof will be omitted.

In the configuration shown in FIG. 4, it will be explained how the photometric amount is distributed by the common ratio relative to the lens aperture value of the geometric progression of the common ratio ゜J〉. In other words, it is only necessary to prove that the above equation (8) holds true from equations (2) and (3).

Therefore, according to FIG. 4, the input terminal I of the highest level signal detection circuit 4'. , , 12...... are the output terminals 0-2, 0-1, 00... of the binary counting circuit section 3.
・Direct or gate circuit ANDI, AND2...
It is connected via..., and numerically it is an input terminal.

, I, , 2 ...... It can be considered that the above numerical values are transmitted using different common ratios. In other words, I. and 11, 13, 14, etc., there is another 1
There is a relationship between 1 and 12, 14 and I, etc., and between 12 and 13, 15 and 16... Ratio 1.25, 1.20 and 1.33
Numerical values are transmitted between input terminals in different geometric progressions. In the device of the present invention, I between the input terminals. It is assumed that numerical values are transmitted using one common ratio where ~I and ~12~ are equal. In other words, (9), QO, assuming that it is transmitted by the geometric mean common ratio of the common ratios obtained by the disant equation, the geometric mean common ratio is
becomes.

Here, let us state the error that occurs between the common ratio obtained by the equations 9), aω, and aυ. The common ratio obtained with 1.
33, an error of -0.16 eV occurs, but it is enough to not impair the photographic effect when taking photographs, and therefore it can be considered that the input terminals are a geometric progression with a common ratio of 3J. .

In other words, the photometric amount K is distributed by a common ratio of 3f,
K= 3,/7n(no, 1, 2...
By substituting ・) into equation (8), it can be seen that the right-hand side holds true.

To explain with a specific example, if the A-D converter circuit section 2 generates seven oscillation pulses proportional to the photometric amount just measured, a count signal 111 is output to the output terminal of the binary counter circuit section 3. be done. The count signal 111 is then transmitted to the highest level signal detection circuit 4' of the distribution circuit section 4, which detects that the 12th input terminal is the highest, and encodes it to select address 3 of the memory circuit section 5. A signal is output. Then, the lens aperture value 1 stored in the memory circuit section 5
．． 4 is called up, and the lens aperture value 1.4 is displayed on the display section 6.
is displayed. The 0.0 display is the same as the explanation in FIG.
-, even if the count signal is output only to the top signal detection circuit 4', the signal is not transmitted to the highest signal detection circuit 4', so in this case 0.0
is displayed.

The embodiment of the device of the present invention has been described above assuming that the number of oscillation pulses from the A/D conversion circuit section 2 is seven, but the amount measured by the photometry circuit section 1 varies depending on the brightness of the subject. Even if the number of oscillation pulses is other than seven, various different aperture values can be displayed in the same way.

As mentioned above, the photometric quantity measured by the device of the present invention is determined by detecting the highest signal of the counting signal of the binary counting circuit directly or via an AND gate circuit without using a route conversion circuit. To provide an inexpensive digital display light meter having a simple circuit configuration and distributing the photometric amount using a common ratio close to the root conversion value within a range that does not impair the effect.

[Brief explanation of the drawing]

FIG. 1 shows a block diagram of a digital display light meter of the present invention, FIG. 2 shows an electric circuit diagram of an embodiment of the digital display light meter of the present invention, and FIGS. 3 and 4 show a block diagram of a digital display light meter of the present invention. An electric circuit diagram of another embodiment of the digital display exposure meter is shown. DESCRIPTION OF SYMBOLS 1...Photometry section, 2...A-D conversion circuit section, 3...Binary counting circuit section, 4...Distribution circuit section, 5. ...Memory circuit section, 6...
Display section.

Claims (1)

[Scope of Claims] 1. A photometric section including a light receiving element that measures subject brightness, an A-D conversion circuit section that generates pulses in response to the output of the photometric section, and a count signal that counts the pulses in binary. and a top signal detection circuit that detects the most significant signal of the binary counting signals and distributes it to a geometric progression of common ratios of the lens aperture values, a distribution circuit unit that outputs an encode signal corresponding to the signal; and a plurality of memory addresses storing a plurality of lens aperture values corresponding to a geometric progression of the lens aperture values, and the encoder outputs the encode signal from the distribution circuit unit. a memory circuit unit to which a signal is applied, selects the memory address according to the encode signal, and outputs the lens series value signal in the selected memory address; and the lens aperture value signal outputted from the memory circuit unit. A digital display exposure meter consisting of a display section that displays numerical values according to the 2 The common ratio of the geometric progression distributed by the highest signal detection circuit is 2, and the multiple lens aperture values stored in the multiple memory addresses of the storage circuit section are of the geometric progression of √2. A digital display exposure meter according to claim 1. 3. The distribution circuit section includes a gate circuit that is connected to each of the plurality of output terminals provided in the binary counting circuit section and applies an output signal corresponding to the binary counting signal to the highest level signal detection circuit, The common ratio of the geometric progression distributed by the top signal detection circuit is √2, and the plurality of lens aperture values stored in the plurality of memory addresses in the storage circuit section are of the geometric progression of 4√2. A digital display exposure meter according to claim 1. 4. The distribution circuit section includes a gate circuit connected to each of the plurality of output terminals provided in the binary counting circuit section and applying an output signal corresponding to the binary counting signal to the highest level signal detection circuit, The common ratio of the geometric progression distributed by the top signal detection circuit is 3√2, and the plurality of lens aperture values stored in the plurality of memory addresses of the storage circuit section are the common ratio of the geometric progression of 6√2. A digital display exposure meter according to claim 1.