JPH0715542B2 - Automatic film sensitivity input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a DX film-compatible camera, in which the film sensitivity described in the cartridge is applied to an exposure determination mechanism built into the camera such as a built-in exposure meter or exposure control device of the camera. The present invention relates to an automatic input device for film sensitivity.

[Conventional technology and its problems]

Exposure control in a still camera is based on determining the combination of exposure time and aperture according to the field brightness and giving the required exposure amount to the film according to the film sensitivity. In order to determine the combination of time and aperture, it is required that the film sensitivity and the field brightness be given as information.

First, FIG. 3 shows an example of a conventionally known exposure control circuit.

The exposure control circuit shown in FIG. 3 is assumed to be a program shutter exposure control circuit that uses shutter blades that also serve as aperture blades and that includes a sub-aperture blade that opens the light-receiving surface of the light-receiving element as the shutter blades open. However, it can also be applied as an exposure control device for a camera that performs so-called TTL direct photometry with aperture-priority automatic exposure of a single-lens reflex camera.

First, in FIG. 3, reference numeral 1 is a light receiving element using, for example, an SPD, and the light receiving element 1 has its anode side connected to the non-inverting input of the operational amplifier 2 and its cathode side connected to the inverting input of the operational amplifier 2, respectively. Output is log diode 3
Is being fed back through. Also, operational amplifier 2
Is connected to the base of a logarithmic expansion transistor TR ₁ connected in series with an integration capacitor 5, and a bypass transistor TR ₂ is connected in parallel to the capacitor 5.

Now, when light corresponding to the field brightness is incident on the light receiving element 1, a photocurrent in the opposite direction flows through the light receiving element 1 via the log diode 3, and a voltage drop due to this photocurrent occurs across the log diode 3. Occurs, and a level in which the voltage applied from the bias power supply 4 is superimposed on this voltage drop is introduced to the output of the operational amplifier 2.

The output of the operational amplifier 2 is connected to the base of a logarithmic expansion transistor TR ₁ connected in series with an integrating capacitor 5, and the capacitor 5 has a bypass transistor.
TR ₂ is connected in parallel. Therefore, the transistor TR _{2 is} operated by the sequencer 6 in conjunction with the shutter release operation.
Is cut off, the capacitor 5 is charged by the current flowing between the collector and the emitter of the transistor TR ₁ with the output level of the operational amplifier 2 determined according to the field brightness as the current supply level.

The charge level of the capacitor 5 is applied to the non-inverting input of the comparator 7, and the inverting input of the comparator 7 is applied with the reference level determined by the constant current source 8 and the resistor 9. Therefore, when the capacitor 5 is charged to the reference level, the output of the comparator 7 is inverted, and the sequencer 6 is the solenoid that holds the shutter blade closing member when the output of the comparator 7 is inverted.
Degauss 10 to end the exposure operation.

By the way, it is well known that the proper exposure amount differs depending on the film sensitivity. In order to input the film sensitivity in the exposure control device having the structure shown in FIG. It is conceivable to change the input voltage of the operational amplifier 2 according to the above, or (2) change the reference level of the comparator 7 according to the film sensitivity.

In the case of a camera equipped with a dial for setting the film sensitivity, these can be easily realized by a structure such as changing the resistance value of the sliding resistance according to the rotating position of the dial for setting the film sensitivity. You can

By the way, in recent years, DX film has been advocated in order to facilitate automation of sensitivity setting at the time of shooting, automation of film rewinding, or automation of development processing, and it has become popular internationally.

Here, the DX film is a film in which information such as film sensitivity and the number of shots is coded at a predetermined position of the cartridge by a conductive pattern, and the pattern is described as the fourth film.
Shown in the figure. Then, regarding the display of the film speed to which the present invention relates, the film speed is displayed as a binary code of 1/3 EV unit.

More specifically, in FIG. 4, bit 1 and bit 7 are common terminals, and conductive paint is always exposed in bit 1 and bit 7 regardless of the film type. And
Five bits from bit 2 to bit 6 are used for the film speed indication, the conductive bit is exposed for the bit to be turned on, and the insulating bit is applied to the bit to be turned off. In this DX code, each bit from bit 2 to bit 6 is weighted as shown in Table 1.

With the exception of some special-purpose films such as copy film, the minimum sensitivity of the currently commonly used films is
Since it is ISO 25, the DX code that is currently being standardized is designed to be compatible with films of ISO 20 and above, all bits are turned off at ISO 20, and carry is carried out bit by bit every 1/3 EV increase. It is displayed in binary code.

Table 2 shows the code list from ISO 20 to ISO 2000. In Table 2, switches S _{1 to} S ₅ are bit 2 respectively.
~ Corresponds to bit 6 on a one-to-one basis, and ○ corresponds to on-bit.

By the way, in the exposure control device having the structure shown in FIG. 3, in order to input the film sensitivity, it is necessary to change the input voltage of the operational amplifier 2 and the reference voltage of the comparator 7 in accordance with the film sensitivity. As already explained, when inputting the film sensitivity displayed by the DX code as a voltage, for example, the method of supplying a current corresponding to the weighting for each bit to the resistor and inputting it as the terminal voltage of this resistor is more conventional than the conventional method. It is considered.

FIG. 5 shows an example in which a current corresponding to the weighting for each bit of the DX code is supplied to the resistor and the input voltage of the operational amplifier 2 is set according to the film sensitivity.

In FIG. 5, the same elements as those in FIG. 3 are designated by the same reference numerals as those in FIG.
S _{1 to} S ₅ are switches corresponding to each bit of the DX pattern described in the Patrone, and switch S ₁ is bit 2 and
The switch S ₂ corresponds to bit 3, the switch S ₃ corresponds to bit 4, the switch S ₄ corresponds to bit 5, and the switch S ₅ corresponds to bit 6.

Further, A ₁ to A ₅ are each switch S ₁ to S ₅ represent a constant current source corresponding to one to one, on and off pattern of the switches S ₁ to S ₅ are applied to the input circuit 11, an input circuit 11 is each switch S ₁ ~
It is designed to activate the constant current source corresponding to the switch in the ON state of S ₅ . Therefore, each constant current source A _{1 to} A ₅
The operation pattern of No. ₁ corresponds to the on / off pattern of the switch groups S _{1 to} S ₅ shown in Table 2.

The constant currents A _{1 to} A ₅ respectively supply currents corresponding to the weights assigned to the corresponding switches S _{1 to} S ₅ to the resistor 12, and the terminal level of the resistor 12 is set to the gain 1 buffer. It is adapted to be applied to the input of the operational amplifier 2 via 13. In the figure, A ₀ and 14 respectively indicate a constant current source and a variable resistor for setting a reference level.

Now, in the circuit shown in FIG. 5, 96 mV is applied to the input of the operational amplifier 2 at ISO 25, and the exposure control corresponding to the film sensitivity is performed when the input level of the operational amplifier 2 is increased by 18 mV every 1 EV increase. If it can be done, for example, the resistance value of the resistor 12 is set to 3 KΩ, the current value of the constant current source A ₀ is adjusted to 30 μA, the current value of the constant current source A ₁ is set to 6 μA, and the current value of the constant current source A ₂ is adjusted. Constant current source with current value of 12 μA
Set the current value of S ₃ to 24 μA and the current value of constant current source A ₄ to 2 μA.
Then, the current value of the constant current source A ₅ may be adjusted to 4 μA.

When the above adjustments are made, the operation patterns of the constant current sources A _{1 to} A ₅ corresponding to the film sensitivity (ISO), the amount of current flowing to the resistor 12 (μA), and the resistor 12 Table 3 shows the correspondence table of the terminal level (mV).

In the case of varying the terminal level of the resistor 12 by avoiding operating the constant current source is weighted corresponding to each bit of the DX code in this manner in response to actuation pattern of the switch S ₁ to S _5, the The weight of the current source has a 12 times difference from a minimum of 1 / 3EV (constant current source A ₄ ) to a maximum of 4EV (constant current source A ₃ ). In the example shown in FIG. 5, the constant current source A ₄ is 2 μA. And the constant current source A ₃ becomes 24 μA.

In an actual circuit, it is extremely difficult to adjust the current value error of the constant current source, which greatly differs in the required current value, within an allowable range, and as shown in FIG. When the current flowing from each constant current source A _{1 to} A ₅ is superimposed on the current as the film sensitivity becomes higher with the current at ISO 20 as the reference, and the current flows to the resistor 12, each constant current source A _{1 to} A ₅
As the film sensitivity increases, the error in the current value of will be added, and the input error will be extremely large for films with normal sensitivity such as ISO100 to ISO400.

[Means for solving problems]

The present invention has been made in order to solve such a problem, it is possible to reduce the error in the current value required for each constant current source, especially in the film of the normal sensitivity such as ISO100 ~ ISO400 film An object of the present invention is to provide a novel film speed automatic input device capable of reducing the sensitivity input error.

In summary, the film sensitivity automatic input device of the present invention is: A camera equipped with an exposure determining mechanism that applies voltage information indicating film sensitivity to a voltage input point, and corresponds to a common film sensitivity at the voltage input point. A reference voltage generating circuit for applying a reference voltage, a plurality of voltage adding means for adding a voltage corresponding to the film sensitivity step to the voltage input point, and a plurality of voltage adding means for subtracting a voltage corresponding to the film sensitivity step from the voltage input point Voltage subtraction means: a switch group corresponding to a coded pattern indicating a film sensitivity written at a predetermined position of the cartridge; an operation pattern of the plurality of voltage addition means and a plurality of operation patterns of the plurality of voltage addition means; And a decoder for controlling the operation pattern of the voltage subtracting means of the: By addition and or subtraction around the pressure it has been made to be able reduce the cumulative amount of error.

[Action]

In the case of the present invention as well, the film sensitivity described as a coded pattern on the cartridge is read to control the voltage at the voltage input point. The voltage corresponding to the normal sensitivity range is added as a reference voltage in advance, and the voltage addition is performed when a higher voltage is required, and the lower voltage is required. In such a case, voltage subtraction is performed, so that the number of voltage combination stages is reduced, particularly in the normal sensitivity region, and the accumulated amount of error can be reduced.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

First, FIG. 1 is a circuit diagram of a film sensitivity automatic input device according to one embodiment of the present invention. Since the structure itself of the exposure control device is the same as the conventional one, the same reference numerals as those in FIG. 3 and FIG. A duplicate description will be omitted. Therefore, also in the circuit shown in FIG. 1, the terminal level of the resistor 12 is determined by controlling the amount of current flowing through the resistor 12 according to the film sensitivity, and this is applied to the input of the operational amplifier 2 via the buffer 13. Then, the film sensitivity can be input as a voltage.

Then, as in Fig. 5, when the film sensitivity is ISO 25, theoretically 96 mV is applied to the input of the operational amplifier 2, and the input level of the operational amplifier 2 is increased by 18 mV every time the film sensitivity increases by 1 EV.
If it is possible to control the exposure corresponding to the film sensitivity when the film sensitivity is increased, the conventional method shown in FIG. 5 first determines the terminal level of the resistor 12 when the film sensitivity is ISO 20, and then the film sensitivity increases. The voltage corresponding to the difference in sensitivity is superposed every time the adjustment is made. In the embodiment of the present invention shown in FIG. 1, for example, a common film sensitivity such as ISO200 is used as the reference sensitivity, and the reference sensitivity is satisfied. If the voltage of the resistor 12 is set as the reference voltage and the film sensitivity that is coded below is lower than the reference sensitivity, the terminal level of the resistor 12 is subtracted corresponding to the film sensitivity difference, and coded in reverse. When the film sensitivity is higher than the reference sensitivity, the terminal level of the resistor 12 is added according to the film sensitivity difference.

Now, the embodiment of the present invention will be described more specifically below with reference to FIG.

First, in FIG. 1, I ₀ is a constant current source for supplying a reference current to the resistor 12 and setting the terminal level of the resistor 12 when the film sensitivity is ISO 200, and 14 is a constant current source I ₀ . This is a variable resistor for adjusting the current value. Then, for example, when the resistance value of the resistor 12 is 3 KΩ, the terminal level of the resistor 12 when the film sensitivity is ISO200 is the same as above.
Since the setting to 150 mV is required, the current value of the constant current source I ₀ is adjusted to 50 μA.

In addition, I ₁ , I _2, and I ₅ are constant current sources for addition, and constant current source I ₀
Each of the set currents is superimposed on the current supplied from the resistor 12 to the resistor 12 and the terminal level of the resistor 12 is added. Then, the constant current source I ₁ is weighted by + 2EV, and the constant current source I ₁ is weighted.
₂ is weighted by + 1EV, and the constant current source I ₅ is weighted by + 1 / 3EV.

Further, I ₃ , I ₄ , I ₆ are constant current sources for subtraction, and the constant current source I ₀
Each setting current is made to flow to the ground from the current supplied from the to the resistor 12, and the terminal level of the resistor 12 is subtracted. The constant current source I ₃ is weighted by −1 EV, the constant current source I ₄ is weighted by −2 EV, and the constant current source I ₃ is
₆ has a weight of −1 / 3EV.

Therefore, when changing the resistance 12-terminal level by 18 mV every 1 EV change with film sensitivity at ISO 200 as the center,
The current value of the constant current source I ₁ is +12 μA, the current value of the constant current source I ₂ is +6 μA, the current value of the constant current source I ₃ is −6 μA, the current value of the constant current source I ₄ is −12 μA, The current value of the constant current source I ₅ is +
The current value of the constant current source I ₆ is set to 2 μA and −2 μA.

Further, in FIG. 1, reference numeral 15 denotes a decoder,
15, the constant current sources I _{1 to} I ₆ are determined by the ON / OFF patterns of the switch groups S _{1 to} S ₅ corresponding to the DX code described as a conductive pattern on the cartridge, and the resistance is determined. 12 The amount of current flowing is controlled so that the terminal level of the resistor 12 becomes a level corresponding to the film sensitivity.

Now, for example, when the film sensitivity is ISO 200, when the decoder 15 turns off all the constant current sources I _{1 to} I ₆ , only a current of 50 μA from the constant current source I ₀ is supplied to the resistor 12, and its terminal level is 150 mV. In this embodiment, it becomes a reference point for inputting film sensitivity.

Then, in the case of ISO400 in which the film sensitivity is increased by 1 EV, if only the constant current source I ₂ is activated, the resistor 12 has a current of 50 μA from the constant current source I ₀ and 6 μA from the constant current source I ₂ . When the current is superimposed and supplied, the terminal level of the resistor 12 increases by 18 mV to 168 mV. Also, the film sensitivity has increased by 2EV
In the case of O800, if only constant current source I ₁ is activated, resistance 12
The current from the constant current source I ₀ to the 50 μA current from the constant current source I ₁ is
When the current of 12 μA is superimposed and supplied, the terminal level of the resistor 12 rises 36 mV to 186 mV. Furthermore, film sensitivity is 3
In the case of ISO 1600 with EV rise, if only the constant current sources I ₁ and I ₂ are activated, the resistor 12 has a current of 50 μA from the constant current source I ₀ and a constant current of 12 μA from the constant current source I _1. The current of 6 μA from the current source I ₂ is superposed and supplied, and the terminal level of the resistor 12 rises by 54 mV to 204 mV.

On the other hand, in the case of ISO100 in which the film sensitivity has decreased by 1 EV, if only the constant current source I ₃ is operated, the current of 50 μA supplied from the constant current source I ₀ to the resistor 12 flows to the constant current source I ₃ . 6
A current of 44 μA is supplied by subtracting the current of μA, and the terminal level of the resistor 12 drops by 18 mV to 132 mV. Further, 50.mu. film sensitivity in the case of ISO50 was 2EV lowered, if actuated only constant current source I _4, the resistor 12 is supplied from the constant current source I ₀
A current of 38 μA is supplied by subtracting the current of 12 μA flowing out to the constant current source I ₄ from the current of A, and the terminal level of the resistor 12 is 36 mV.
It falls to 114 mV. Furthermore, in the case of ISO25 the film sensitivity is 3EV lowered, the constant current source I ₃ and if ask only the actuating I _4, the constant current source to the resistor 12 from current 50μA supplied from the constant current source I ₀ I ₃ Current of 12 μA and constant current source I ₄
A current of 32 μA, which is a reduction of the current of 6 μA flowing out to, is supplied, and the terminal level of the resistor 12 drops by 54 mV to 96 mV.

As is well known, the sensitivity of currently marketed films is 1 /
The steps are in 3EV units, and the DX code also encodes film sensitivity in 1 / 3EV steps.

In the present embodiment, the current amount of the constant current source I ₅ is + 1 / 3E.
Since it is + 2mA corresponding to V, the film sensitivity is 1 / 3EV higher than the film sensitivity of 1EV unit (for example, ISO64 or ISO125
In the case of), if the constant current source I ₅ is activated,
A current of 2mA is superimposed, and the terminal level rises by 6mV, which corresponds to 1 / 3V.

Further, in this embodiment, the current amount of the constant current source I ₆ is -1 / 3EV.
It is equivalent to −2mA, so it is 1 / 3EV lower than the film sensitivity of 1EV unit (for example, ISO80 or ISO160).
If the constant current source I ₆ is activated, the constant current source I ₆
The current of 2mA flows out through and the terminal level of the resistor 12 is 1/3.
It will fall by 6 mV, which is equivalent to EV.

In addition, next, the decoder 15 corresponding to the film sensitivity (ISO)
Table 4 shows the correspondence relationship between the operation patterns of the constant current sources I _{1 to} I ₆ controlled by the current amount (μA) flowing through the resistor 12 and the terminal level (mV) of the resistor 12.

Also, the DX code itself is being standardized internationally, the on / off patterns themselves of the switch groups S _{1 to} S ₅ are the same as in Table 2, and the input pattern of the decoder 15 is the switches S _{1 to} S 5. It is the same as the on / off pattern of ₅ .

Further, FIG. 2 shows an example of the circuit of the decoder 15. When the ON / OFF pattern of the switch groups S _{1 to} S ₅ shown in Table 2 is given as an input pattern to the decoder 15 of this kind configuration, Table 4 shows The operation patterns of the constant current sources I _{1 to} I ₆ shown in are obtained as the output pattern of the decoder 15.

Next, the operation of this embodiment will be described with reference to the above matters.

First, when the DX film is set in the camera and the power of the camera is turned on, the switch S corresponding to the pattern of the film sensitivity in the DX code written in the conductive pattern at the predetermined position of the cartridge is displayed. _{1 to} S ₅ are turned on and off, and this pattern is matched by the input circuit 11 and given to the input of the decoder 15. The input pattern of on-off pattern and the decoder 15 of the switch S ₁ to S ₅ corresponding to the film sensitivity at this time is as shown in Table 2.

The decoder having the structure shown in FIG. 2 decodes the input pattern into a pattern as shown in Table 4 to generate a constant current source I ₁
~ Determine the activation pattern of I ₆ .

On the other hand, the constant current source I ₀ has been operating since the
The current of A is supplied to the resistor 12. Then, from the constant current sources I ₁ · I ₂ · I ₅ each specific current constant current source I ₀ when either of the constant current source I ₁ · I ₂ · I ₅ is actuated by the output pattern of the decoder 15 Resistance superimposed on the supplied current
Fed to 12, and, the constant current source when either the output pattern of the decoder 15 of the constant current source I ₃ · I ₄ · I ₆ is actuated
Since supplied to the I ₃ · I ₄ · I ₆ are each resistor 12 is subtracted from the current supplied to specific current from the constant current source I _0, a current shown in Table 4 correspond to the loaded film speed It will flow to the resistor 12.

Since the terminal level of the resistor 12 is determined by the amount of current flowing through the resistor 12, the terminal level of the resistor 12 is
It will be decided according to the DX code written on the patrone of the DX film, and the level shown in Table 4 will be the terminal level of the resistor 12 corresponding to the ISO sensitivity of the mounted film.

Then, the terminal level of the resistor 12 is applied to the input of the operational amplifier 2 via the buffer 13 of gain 1.

On the other hand, since the photocurrent corresponding to the field brightness flows through the log diode 3 in the light receiving element 1 from the time of power-on, the output of the operational amplifier 2 from the buffer 13 due to the voltage drop of the log diode 3 due to the photocurrent. A level obtained by superimposing the output level of the added operational amplifier 2 is introduced, and the collector-emitter current of the transistor TR ₁ is controlled with the output level of the operational amplifier 2 as the current supply level.

As described above, when the transistor TR ₂ is cut off in conjunction with the shutter release, the transistor T
The capacitor 5 is charged by the collector-emitter current of R ₁ and the output of the comparator 7 is inverted when the charge level reaches the reference level of the comparator 7, whereby the sequencer 6 demagnetizes the solenoid 10 to end the exposure operation. .

Also in the case of this embodiment, since the input level of the operational amplifier 2 rises corresponding to the film sensitivity, the charging current of the capacitor 5 flowing through the transistor TR ₁ increases as the film sensitivity increases in the same field brightness. However, the shutter speed also rises, and it becomes possible to provide proper exposure.

By the way, in the case of the present embodiment described above, the terminal level of the resistor 12 determined corresponding to the film sensitivity is exactly the same as that of the conventional example shown in FIG. 5 and Table 3, but in the case of the present embodiment, first, The terminal level of the resistor 12 required at ISO200 which is the central sensitivity of the common film in 1 is determined by the current supplied from the constant current reduction I _0, so ISO100 or ISO400
For the most frequently used film, such as, there is little duplication of error and high-precision exposure control becomes possible. Furthermore, since the terminal level of the resistor 12 required at ISO200, which is the central sensitivity of regular films, is used as a reference, sensitivity is set by adding / subtracting the level due to superimposition and outflow of current from each constant current source. In the case of the present embodiment, the setting range of each constant current source is 2 μA to 12 μA, which is half that of the conventional one. Therefore, the setting error of each constant current source is also reduced, and high accuracy is obtained for a wider range of film sensitivity. It enables precise exposure control.

Although the film sensitivity is input as the input voltage of the operational amplifier 2 in the above description, it may be input as the reference voltage of the comparator 7.

Further, in the above, the example in which the present invention is applied to the exposure control device of the program shutter using the shutter blade that also serves as the diaphragm blade is shown, but the present invention is not limited to the exposure control device of the type in which the film sensitivity is input as a voltage. In addition to the automatic exposure control device as described above, for example, even with a built-in camera type exposure meter that displays exposure information in the viewfinder, the film sensitivity can be input as voltage. The present invention can be widely applied as long as it is one.

Furthermore, in the above example, the amount of current flowing through the resistor is controlled by the operation patterns of the constant current source that supplies the current and the constant current source that causes the current to flow, and the terminal level of the resistor is set to a level corresponding to the film sensitivity. Although shown, the same effect can be obtained by using the voltage adding circuit and the voltage subtracting circuit.

〔effect〕

As described above, according to the present invention, since the central sensitivity of the common film can be adjusted as a reference, the exposure error when the common film is loaded becomes extremely small. or,
Since the number of stages of the power source for adjustment is also reduced, the adjustment error is reduced and the exposure control can be performed with high precision for a wider range of film sensitivity.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of a circuit of a decoder according to the present invention, FIG. 3 is a circuit diagram of a conventionally known exposure control circuit, and FIG. Is a DX pattern configuration diagram, and FIG. 5 is a circuit diagram of a conventional film sensitivity automatic input device. S ₁・ S ₂・ S ₃・ S ₄・ S ₅ …… Switch 11 …… Input circuit, 12 …… Resistance 13 …… Buffer, 15 …… Decoder I ₀・ I ₁・ I ₂・ I ₃・ I ₄・ I ₅・ I ₆ …… Constant current source

Claims (1)

[Claims] 1. A camera provided with an exposure determining mechanism adapted to apply voltage information indicating film sensitivity to a voltage input point, and a reference voltage generating circuit for applying a reference voltage corresponding to a common film sensitivity to the voltage input point. , A plurality of voltage adding means for adding a voltage corresponding to the film sensitivity step to the voltage input point, a plurality of voltage subtracting means for subtracting a voltage corresponding to the film sensitivity step from the voltage input point, and a predetermined position of the cartridge. A switch group corresponding to the coded pattern indicating the described film sensitivity, and an operation pattern of the switch group are decoded to control an operation pattern of the plurality of voltage adding means and an operation pattern of the plurality of voltage subtracting means. A decoder, and adds and / or subtracts the voltage applied to the voltage input point around the reference voltage. Film speed automatic input apparatus characterized by was Unishi.