JPS5843724B2 - Electric shutter that uses an aperture to correct the intermediate value of the shutter time - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intermediate value correction device for an electric shutter in which the shutter time is adjusted stepwise, particularly for a TTL type electric shutter, in which the intermediate value correction is performed using an aperture.

Conventionally, in electric shutters that store the intensity of photographic light as a voltage value in a capacitor and use this capacitor for time setting, the shutter time has been adjusted steplessly.

However, the digital electric shutter that was developed after that generates a number of pulses according to the intensity of the photographing light and stores the number of pulses, but if you want to improve the accuracy, you need to increase the oscillation frequency of the pulses. At the same time, a large number of storage stages must be provided.

Since memory stages are usually constructed mainly of flip-flops, providing a large number of memory stages complicates the circuit and increases costs.

Therefore, an object of the present invention is to make it possible to obtain an exposure amount with a small error even if the number of storage stages is small.

The basic principle of the present invention is to divide the number N of pulses generated corresponding to the logarithmic value of the intensity of the photographing light by a constant number, determine the shutter time based on the quotient A, and convert the remainder B into a voltage value. The aperture is controlled according to this voltage value.

Accordingly, the present invention includes a light-responsive pulse generation circuit that generates a number of pulses corresponding to the logarithm of the intensity of photographing light, a frequency dividing circuit that divides the number of light-responsive pulses from this pulse generation circuit, and A shift register storage circuit that stores the number of subsequent optical response pulses, a reference pulse oscillator that generates a reference pulse of a constant frequency, and a shift register storage circuit that selects a binary carry pulse from the reference pulse and simultaneously opens the shutter. and a pulse selection circuit to send an additional pulse to the shutter, and a shutter control circuit that controls the shutter by using the time required for the signal stored in the storage circuit to shift from its storage position to a predetermined storage stage position before opening the shutter as a shutter time. A shutter circuit is provided, further comprising a pulse accumulation circuit which receives and accumulates the photoresponse pulse from the photoresponse pulse generation circuit and receives the photoresponse pulse after frequency division from the frequency divider circuit as a reset pulse; The present invention includes an aperture control mechanism that controls the aperture according to the pulse accumulated voltage of the circuit, and an intermediate value correction circuit that adjusts the aperture that has been previously adjusted to a desired value by a required amount in accordance with the pulse accumulated voltage. Hereinafter, the present invention will be described in detail based on embodiments of the present invention, which proposes an electronic shutter that uses an aperture to correct the intermediate value of the shutter time.

FIG. 1 shows an electric shutter in which the storage stage of the electric shutter is composed of a shift register, and which logarithmically compresses and stores intensity information of photographing light. An example of application is shown.

In the figure, a block A surrounded by a dotted line represents an electric shutter circuit, and a block B surrounded by a dotted line is a main part of the intermediate value correction device according to the present invention.

In this embodiment, the optical response pulse generation circuit for the intermediate value correction device is also used as that for the electric shutter.

First, the electric shutter circuit A will be explained.

This electric shutter circuit A sends the generated Surhals number as a shift pulse to a shift register in proportion to the logarithm value of the intensity of the photographing light and stores it, and then, after opening the shutter, a pulse train in which the pulse interval is sequentially extended is transmitted to the shift register. The additional shift pulse is sent to the shift register, and the time required for the shift register to shift to the final stage is defined as the shutter time.

Reference numeral 1 denotes a light-responsive pulse generation circuit that generates a pulse number proportional to the logarithmic value of the intensity of the photographing light.
Even if the number of pulses changes in multiples such as ・・・・・・・・・, the number of pulses generated is 1, 1+m, l+2m, 1+3m
The number of lid margins varies as follows.

These l and m can be determined arbitrarily, but for the sake of explanation, l
=m=4.

The photoresponse pulse generation circuit 1 operates, for example, in the region where the release button is previously pressed.

2 is a frequency dividing circuit, for example, a frequency dividing counter is used, and the frequency division ratio can be determined arbitrarily, but here, the photoresponse pulse is 4.
One pulse is output each time one pulse is input.

The relationship between this optical response pulse and the frequency-divided pulse is as shown in FIG.

3 is an OR circuit, and 4 is a shift register which receives the photoresponse pulse frequency-divided by the frequency dividing circuit 2 as a shift pulse via the OR circuit 3.

In the initial state, the first stage of the shift register 4 has an output of "1".

Reference numeral 5 denotes an SCR as a switching element that receives the final stage output of the shift register 4, and is turned on by the output when the shift register 4 has shifted to the final stage.

6 is an electromagnet for closing the shirt. Reference numeral I designates a pulse train generation circuit that generates a pulse each time a geometrical series time elapses after the shutter is opened, and here a pulse is generated each time a multiplexed time elapses after the shutter opens.

Therefore, this pulse train generation circuit γ includes a reference pulse oscillator 8 that generates reference pulses of a constant period, and a pulse train of 2 to the nth power (n-0, 1, 2) among the pulses from the reference pulse oscillator 8.
. . . ), that is, a binary carry pulse.

As shown in FIG. 3, the pulses output from the pulse train generating circuit 7 have a time period from the opening of the shutter to the generation of each pulse, which is sequentially multiplied.

The reason why the time from when the shutter opens until each pulse is generated follows a geometric progression is that the number of light response pulses is not simply proportional to the intensity of the photographing light, but is due to so-called logarithmic compression. This is because it is necessary to extend the shutter time in order to obtain an appropriate shutter time.

The pulses generated by the pulse train generation circuit I are inputted to the shift register 4 via the OR circuit 3 as additional shift pulses.

Next, in the intermediate value correction circuit B, 10 is a pulse accumulation circuit, which receives the optical response pulse from the optical response pulse generation circuit 1 and accumulates the number of pulses as a voltage value. Each time reaches a certain number, that is, frequency divider circuit 2
Each time a pulse after frequency division is received, the accumulated voltage value is reset and the pulse number is measured again.

The relationship among these optical response pulses, the optical response pulses after division, and the pulse accumulation voltage is clearly shown in FIG.

Reference numeral 11 denotes an aperture leg mechanism that controls the aperture according to the accumulated voltage value of the pulse accumulation circuit.

In this embodiment, the number of light response pulses was proportional to the logarithm of the intensity of the photographing light, so the aperture control mechanism 11 operates to narrow down the aperture as will be described later.

This aperture control mechanism may be a servo motor, a meter, or the like.

The operation of the electric shutter circuit A and the intermediate value correction circuit B will be explained.

Point the camera at the subject, adjust the aperture to the desired value, and press the release button. The light response pulse generation circuit 1 is activated in the previous press area, and the pulse generator generates a pulse that is proportional to the logarithm of the intensity of the photographing light at that time. The number of pulses is determined by the frequency dividing circuit 2 and the pulse accumulation circuit 10.
sent to.

The number of photoresponse pulses is large when the photographing light is strong, and is small when it is weak.

Now, assuming that the intensity of the photographing light is 2.75 LV, the number of light response pulses will be 11 as shown in FIG.

The frequency dividing circuit 2 to which these 11 pulses have been sent outputs two pulses as shown in the figure.

Further, as shown in the figure, the pulse accumulation circuit 10 also repeatedly accumulates pulses and resets using pulses after frequency division, and finally reaches the voltage vA.

As a result of the voltage constantly changing in the range from 0 to VA as shown in the figure before the pulse accumulation circuit 10 settles on the final voltage VA, there is a concern that the diaphragm will constantly repeat opening and closing operations due to this changing voltage. The changes are extremely fast and the aperture has inertia so it does not move while the stored voltage is changing.

The two pulses output from the frequency dividing circuit 2 are sent to the heliset of the pulse accumulation circuit 10 as described above, and are also sent to the OR
The signal is sent through the circuit 3 to the shift register 4 as a shift signal.

The shift register 4 that receives this shift pulse moves from the first stage to the final stage by the number of pulses (two pulses).
shift.

Therefore, the shift position stores the number of input pulses.

In other words, this shift register 4 controls the intensity of the photographing light by 2LV.
There is an error of 0.75 LV between the actual strength of 2.75 LV and the actual strength of 2.75 LV.

If you continue shooting as is, you will be overexposed by 0.75LV.

The role of the intermediate value correction circuit B is to correct this error.

That is, since the pulse accumulation circuit 10 was at the final voltage VA in parallel with the storage in the shift register 4, the aperture control mechanism 11 that receives this voltage adjusts the aperture, which had been adjusted to the desired value, by an amount equivalent to 0.75 LV. Refine.

It can be seen that the relationship between the storage in the shift register 4 and the pulse accumulation voltage described above satisfies the basic principle of the present invention described above.

Next, when the release button is pressed down to the final stage, the shutter opens and the pulse train generation circuit 7 is activated.

Therefore, the pulse P1 as shown in FIG. P2. P3...
. . . are sent one after another as additional shift I pulses to the shift register via the OR circuit 3, and the shift register which has already been shifted by two pulses by the photoresponse pulse is 4 is shifted further to the rear.

When the shift register 4 has shifted to the final stage, the output from the photographing stage causes the 5CR5 to turn ON and the electromagnet 6 to be excited, thereby closing the shutter.

Therefore, the shutter time is determined by the time it takes for the shift register 4 to shift to the final stage after the shutter opens.In this case, the shutter time is determined by the time required for the shift register 4 to shift to the final stage. The shutter time is equivalent to .

In this way, in this embodiment, the memory stage of the electric shutter stores the intensity of the photographing light for each ILV, and the aperture is controlled for the intermediate value, so even though the number of memory stages is small, First, you can obtain an exposure amount commensurate with the intensity of the photographing light.

In the above embodiment, the electric shutter identifies the intensity of photographing light at ILV intervals and creates a corresponding shutter time. Even if the distance is 2LV, there is no problem in implementing the present invention.

Further, the present invention can be applied even if the electric shutter is a closed-down photometry method or an open photometry method is adopted and the electric shutter is used in °C.

For example, when the electric shutter employs an open metering method, the preset ring, which has been adjusted to a set value in advance, can be controlled by an aperture control mechanism by an amount corresponding to an intermediate value.

If the aperture is controlled by an amount equivalent to the intermediate value as a result, the control means can adopt the configuration most suitable for the camera.

Next, a specific example of a circuit whose structure is not considered to be well known among the circuits shown by the block in FIG. 1 will be described.

4 and 5 show a specific example of the photoresponse pulse generation circuit 1, which is a circuit that generates a number of pulses proportional to the logarithmic value of the intensity of photographing light.

The circuit shown in FIG. 4 is composed of a photoelectric timer circuit 12 and a pulse oscillation circuit 13.

A voltage regulated by logarithmic compression diode 14 and CDS 15 is input to transistor 18 via transistor 16 and variable resistor 17 to change the internal resistance of transistor 18.

The transistor 18 and capacitor 19 constitute a time constant circuit.

20 is a switching transistor which inputs the voltage between the terminals of the capacitor 19; 21 is the O of the transistor 20;
It is an electromagnet excited by N, and is used to open the switch 22.

23 is a variable resistor for changing the oscillation frequency, and 24 is a unijunction transistor.

In FIG. 5, the timer circuit 25 is a normal timer circuit and is independent of the intensity of the photographing light, and the pulse oscillation circuit 26
The oscillation frequency is proportional to the logarithm of the intensity of the photographing light.

In addition, in FIGS. 4 and 5 above, the variable resistor included in the timer circuit or pulse oscillation circuit has an exposure factor (
For example, it can be used to calculate film sensitivity).

FIG. 6 shows a specific example of the pulse selection circuit 9.

27 is a binary counter, 27a, 2γb.

27c is each bit stage of the binary counter 27, 28a
328b t 28c is an SCR that turns ON upon receiving the output of each bit stage.

Although only three bit stages and three SCRs are shown in the figure, in reality, a large number of them are provided.

Each SCR is equipped with a differentiator circuit consisting of a capacitor and a resistor, and when the SCR is turned on, the differential pulse is ORed.
The signal is sent to circuit 29.

In this pulse selection circuit, when the reference pulse from the reference pulse oscillator 8 is input to the binary counter 27 at the same time as the shirt shutter is opened, each bit stage 27a, 27b,
27c outputs a binary output.

In response to this output, 5CRs 28a, 28b, and 28c are sequentially turned on during the first, second, and fourth reference pulses, and as a result, the OR circuit 29 obtains a pulse train as shown in the figure.

This pulse train includes the shutter opening latter pulse P1. P2.
P3. The time until P4...

7 and 8 show specific examples of the pulse accumulation circuit 10. FIG.

The number of pulses from the photoresponse pulse generation circuit 1 is stored in the capacitor 30 as a voltage value.

In the circuit of FIG. 7, this accumulated voltage is
It is transmitted to the aperture control mechanism 11 via.

Transistor 32 is a switching transistor that is turned on in response to a reset pulse to discharge the voltage accumulated in capacitor 30. Reference numeral 633 is a display member such as a lamp, which visually confirms that the intermediate value correction is being performed. It is for.

In the circuit shown in FIG. 8, the aperture control mechanism is not operated by the output of the transistor 31, but the intermediate value correction amount is displayed, and the aperture is manually adjusted based on the displayed amount.

34, 35, 36 are switching transistors with different switching levels; 37, 38, 39 are lamps inserted on the output side of each transistor; It is designed to identify and display the intermediate value correction amount.

Note that instead of these switching transistors, lamps, etc., a meter may be inserted on the output side of the transistor 31 for display.

FIG. 9 shows an example of a configuration for determining whether or not the operation of the aperture control circuit 11 has been completed. The aperture ring 40 is provided with a comb-shaped contact 41, to which power is constantly supplied. There is.

42 is a fixed contact that makes sliding contact with the comb-shaped contact 41, and 43 is a lamp that is supplied with power through the comb-shaped contact 41 and the fixed contact 42.

While the aperture ring 40 is rotating, the comb-shaped contact 41 and the fixed contact 42 are repeatedly connected and disconnected, and as a result, the lamp 43 blinks, so you can know that the aperture control circuit 11 is operating, and the lamp When the icon stops blinking, you will know that the aperture correction operation has been completed.

Note that the means for detecting the rotational movement of the diaphragm may be an electromagnetic type, a photoelectric type, or the like.

Specific examples of each circuit have been explained above, but these are -
This is just an example, and it goes without saying that other circuits with similar functions can be used.

As described above, in the present invention, even though the shutter time is adjusted in stages, the aperture can be controlled for intermediate values to obtain the appropriate exposure amount. At least a highly accurate exposure amount can be obtained.

In particular, the number of light response pulses for controlling the aperture corresponds to the logarithm of the intensity of the photographing light, so the amount of change in the number of pulses is constant whether the photographing light is bright or dark (for example, ILV (The number of intermediate value pulses between and 2LV is equal to the number of intermediate value pulses between 10L and IILV), and the intermediate value correction amount can be determined according to the number of intermediate value pulses.

For example, if the number of intermediate value pulses between lLV and 2LV is 3, and the number of intermediate value pulses between l0LV and IILV is 9, then when the intensity of the photographing light is 1.5LV, the intermediate value It is necessary to perform aperture control of 0.5LV with two pulses, and when the number of pulses is 10.5LV, it is necessary to perform aperture control of 0.5LV with five intermediate value pulses, but the present invention eliminates this trouble. There is no feeling.

[Brief explanation of drawings]

Fig. 1 is an electrical block diagram of an electric shutter that implements the present invention for converting the intensity of photographing light into the number of pulses and storing it, and Fig. 2 shows the optical response pulses in each of the above embodiments, after frequency division. FIG. 3 is a diagram showing the pulses generated from the pulse train generation circuit in the embodiment described above, and FIGS. 4 to 9 are diagrams showing the relationship between the pulses and the pulse accumulation voltage. FIGS. FIG. 3 is a diagram showing a specific example. 1...Photoresponse pulse generation circuit, 2...
Frequency divider circuit, 4...Shift register, 10...
...Pulse accumulation circuit, 11...Aperture control mechanism.

Claims (1)

[Claims] 1. A photoresponse pulse generation circuit that generates a number of pulses corresponding to the logarithm of the intensity of the photographing light, a frequency dividing circuit that divides the number of photoresponse pulses from this pulse generation circuit, and a number of photoresponse pulses after frequency division. a shift register memory circuit that stores a reference pulse, a reference pulse oscillator that generates a reference pulse of a constant frequency, and a pulse that selects a binary carry pulse from the reference pulse and sends it as an additional pulse to the shift register memory circuit at the same time as the shutter opens. an electric shutter circuit for controlling the shutter by using the time required for the signal stored in the storage circuit to shift from its storage position to a predetermined storage stage position as a shutter time before opening the shutter; , a pulse accumulation circuit that receives and accumulates the photoresponse pulse from the photoresponse pulse generation circuit, and receives the frequency-divided photoresponse pulse from the frequency divider circuit as a reset pulse, and a pulse accumulation voltage of the pulse accumulation circuit. A shutter comprising: an aperture control mechanism that adjusts the aperture according to the pulse accumulation voltage; An electric shutter that uses an aperture to correct the intermediate value of time.