The present invention relates to means for adjusting camera electric circuits, and more particularly, to means for adjusting camera exposure control circuits.

In the past, a method for adjusting camera exposure control circuits or a method for adjusting a camera exposure level, a display level and the like, has been mainly by employing a semifixed resistor (trimmer resistor) or by adjusting an analog quantity with the trimming of a fixed resistor (employing a laser and the like).

An example of such a conventional adjusting means will be described with reference to FIG. 8. A photographing operation with an automatic exposure for a single-lens reflex camera is as follows. Information on brightness of an object being photographed is introduced through a photographing optical system or the like (not shown) into a photometric element 1 and is converted into a photocurrent therein. The photocurrent is further converted into a logarithmically compressed voltage by a photometric circuit comprising an operational amplifier 2 and a compression diode 3. The voltage is compensated in temperature and is adjusted in level by a diode 4 for compensating temperature, a semifixed resistor 5 for adjusting a level and a constant current source 8 and is then fed through an analog multiplexer 9 into an A/D converter 10. An aperture information voltage from a resistor 6 and a film sensitivity information voltage from a resistor 7 are fed through the multiplexer 9 into the A/D converter 10 to be subjected to an A/D conversion. An output from the A/D converter 10 is fed into a calculator 11. The calculator 11 digitally calculates a shutter speed Tv (denoted by the APEX system) for a proper exposure using the following well known equation:

Tv=Sv+Bv-Av

of the APEX system; where Av is an aperture value, Bv is a brightness value of an object being photographed and Sv is a film sensitivity value. Then, when a release initiate means (not shown) starts to stop down, the calculator 11 counts pulses from a contact piece 12 which slides in cooperation with the stop down operation. When a given number of pulses is reached, the calculator 11 turns a switching element 13 on to allow a magnet 16 for locking an aperture to operate, thereby terminating the stop down operation. Subsequently, upon rise of a movable mirror, a switching element 14 is rendered on to operate a magnet 17 for running a first shutter blind, thereby the first blind starts to run. After a time period calculated above, a switching element 15 is rendered on to operate a magnet 18 for running a second shutter blind, thereby the second blind being released to start running. Thus, the photographing operation is completed.

In the above photographing operation with automatic exposure, values of transmittivity of an optical system in a camera, efficiency of a photosensitive element, current of the constant current source 8, and resistances for setting a film sensitivity and an aperture vary, so that, after an A/D conversion of the values, these converted digital data are:

Bv'=Bv+ΔBv,

Av'=Av+ΔAv, and

Sv'=Sv+ΔSv,

including errors ΔBv, ΔAv and ΔSv.

To eliminate these errors, a conventional method compensates them by interposing the semifixed resistor 5. Specifically, the Bv value is corrected by a compensation value ΔCv and the corrected Bv value is subjected to an A/D conversion. While performing an assembling process, under the condition that a given amount of light is given to a camera, an exposure level is inspected and its deviation from a proper exposure value is compensated by adjusting the semifixed resistor 5. In other words, the calculator 11 actually calculates:

Tv32 Sv+ΔSv+Bv+ΔBv-ΔCv-(Av+ΔAv),

adjusting ΔCv so as to obtain the relation:

ΔCv=ΔSv+ΔBv-ΔAv.

In the conventional method of adjusting a semifixed resistor, however, an assembler or inspector reads an output from a circuit by an indicator and adjusts a semifixed resistor to a desired value, so that it is time-consuming, and it is difficult to reduce the cost of parts and assembling and also to automate the adjustment. Although a trimming with a laser or the like can be automated, there are such problems that an apparatus for the trimming becomes a large scale undertaking and readjustment is impossible; specifically it is practicable while electric parts are assembled on a substrate but it is impracticable while they are assembled in a case body of a camera.

Lately an EEPROM (electrically erasable and programmable read only memory) of a small capacity has been developed as a non-volatile digital memory element. The EEPROM is introduced under the item "aiming at a cost reduction by integrating an EEPROM on an analog-digital hybrid CMOS custom IC" in Japanese magazine "Nikkei Electronics", Jul. 1, 1985, page 235; in which it has remarkable effects on an economical advantage because of integrating only a required capacity and a DIP (dual in-line package) switch is replaceable by it. Thus, the EEPROM is suitable for storing operational procedures of instruments or the like and for calibration thereof. Also, it is possible to store and to renew a program. In addition, it is possible to use for trimming an analog circuit. As such, the range of its use is increasing from a digital circuit to an analog circuit.

It is an object of the present invention, in order to solve the above problems, to provide a means for adjusting a camera electric circuit which is capable of reducing both the cost and space of the electric circuit by employing a memory element of the above-mentioned non-volatile type.

The adjusting means of the present invention feeds photographing data bearing digital values converted from analog values into the calculator; while calculating based on the digital values, reads digitized compensation data from the non-volatile memory element; and, after a calculating operation regarding the compensation data, controls an exposure control circuit or an exposure display circuit of a camera; thereby dispensing with provision of an analog adjusting circuit. The compensation data are stored by determining an error or difference between a result in control various variation factors of each camera and a proper value or a sequence of measuring an error and storing the compensation data is previously programmed in a calculator.

Consequently, according to the present invention, it is possible to dispense with the provision of conventionally used semifixed resistors for adjustment or to largely reduce the number of parts and the space occupied by the electric circuits and to facilitate an automatic adjustment.

FIG. 1 is a diagram illustrating a first embodiment of an electric circuit including an adjustment circuit for cameras according to the present invention;

FIG. 2 is a diagram illustrating a second embodiment of an electric circuit including an adjustment circuit according to the present invention;

FIG. 3 is a time chart of the adjustment circuit shown in FIG. 2;

FIG. 4 is a diagram illustrating a third embodiment of an electric circuit including an adjustment circuit according to the present invention;

FIGS. 5 to 7 are detailed diagrams of a non-volatile digital memory element more; particularly, FIG. 5 is a block diagram of its structure, FIG. 6 is a block diagram illustrating memory areas and FIG. 7 is a diagram illustrating an operational relation between EN and R/W and

FIG. 8 is a diagram illustrating an example of a conventional electric circuit including an adjustment circuit for cameras.

In the following embodiments, only novel structural portions will be described and the description of structural portions similar to those of a conventional apparatus described with reference to FIG. 8 is omitted, leaving only reference numerals in the following embodiments.

The present invention uses a non-volatile memory element described above eliminating the need for a conventional semifixed resistor.

In FIG. 1, a non-volatile digital memory element 20 (hereinafter refered to as a memory element) stores data from a data line 22 in its memory area while a jumper 21 is connected. During an assembling process, a given brightness is given to a camera and, under this condition, required data on the basis of a difference between an exposure value measured by a calibrated test instrument and a proper exposure value are stored in the memory element 20 by an entering apparatus (not shown). Assuring that the stored data are correct, the jumper 21 is removed. Thereafter, it is impossible to store further data in the memory element 20 and thus the stored data are not erroneously varied.

Methods for determining storing data and for compensating based on the stored data are as follows. As described above, data after the A/D conversion include respective errors, so that an exposure value deviates from a proper value by

ΔCv=ΔSv+ΔBv-Av.

Then, digital data corresponding to ΔCv are stored in the memory element 20. The calculator 11 reads the data corresponding to ΔCv before and after the A/D conversion from the memory element 20 and calculates the following:

Tv=Bv'+Sv'-Av'-ΔCv.

The Tv value thus obtained is

Tv=Bv+Sv-Av,

so that an error is cancelled and a proper shutter speed is determined.

In addition, it is possible to separately compensate an error ΔAv between an aperture value preset by a resistor 6 for inputting aperture information and an actual aperture value. Specifically, when an aperture value actually controlled is deviated by ΔAv from the preset aperture value, the number of pulses N corresponding to ΔAv which are produced at a sliding contact piece 12 is stored in the memory element 20. When ΔAv is positive (over-stopping), the number of pulses for operating a magnet 16 for locking an aperture may be reduced by N and when ΔAv is negative, the number of pulses may be added by N.

FIG. 2 shows a second embodiment of the present invention which is applied to an exposure control camera of the film surface reflex photometry type. In FIG. 2, a calculator 11 turns a switch 36 on and simultaneously a switch 37 off, prior to an exposure operation. Consequently, a constant current is integrated by a capacitor 35 of a standard voltage integration circuit including a constant current source 28. An output of an operational amplifier 34 rises as shown by a characteristic line A in FIG. 3. After a timer period to corresponding to a film sensitivity, the calculator 11 turns the switch 36 off and thus the integration is completed. Thereafter, the calculator 11 turns a switching element 14 on to energize a magnet 17 for running a first shutter blind, thereby the first blind starts to run, and at the same time opens a switch 32 of a photometry circuit. As a result, a photocurrent of a photometric element 1 which receives a light ray reflected by surfaces of the first blind and a film is integrated by a capacitor 31 and an output voltage of an operational amplifier 33 rises as shown with a characteristic line B (FIG. 3). With the lapse of a time period Ts until the characteristic lines A and B cross each other, an output of a comparator 38 becomes a low level L to turn a switching element 39 off. Thereby, a magnet 40 for locking a second shutter blind is deenergized to release the second blind, thereby the second blind starts to run. Thus, the exposure is completed.

Electric contact pieces 41 to 44 read film sensitivity information, that is, a Dx code among pieces of information from a film cartridge.

In operation, a film cartridge including the given film sensitivity information is loaded into a camera and a taking lens having a given diaphragm aperture is mounted on the camera. A light ray of a given brightness is given to the front surface of the taking lens. Under this condition, the camera is exposed to the light ray with a shutter speed Tsa as the adjusting means operates as described above.

On the other hand, the calculator 11 calculates a ratio Ts' between a previously standardized shutter speed Ts and an actual shutter speed Tsa while jumpers 21, 22 are connected. The ratio Ts'=Ts/Tsa is stored in the memory element 20.

With the above procedures, during an actual exposure with the jumpers 21, 22 removed, the calculator 11, prior to an exposure, compensates an integration time to of a capacitor 35 by multiplying Ts', whereby a proper exposure can be achieved.

In addition, when a given value to a different film sensitivity is preset in the same way as before, it is possible to independently compensate for each of a high and a low film sensitivity by removing either of the jumpers 21, 22 while data are stored in the memory element 20. Particularly, in an exposure control circuit of non-compression type, there may be an occasion when trends in exposure error for a low and a high film sensitivity in ISO are different because of effects such as offset of an operational amplifier, in which adjusting based on a film sensitivity is impracticable with a semifixed resistor. At this time, however, the present invention advantageously makes it possible to effect adjustment based on a film sensitivity in ISO.

An essential point in the second embodiment is that, as described in the prior art, as long as there are a lens having a given aperture and a brightness generating means, even without a calibrated test instrument, it is possible to adjust an exposure in a simple way by providing such a spontaneous adjusting program in the calculator 11.

In the case where a diaphragm aperture is compensated as described in the first embodiment, it is also possible to spontaneously store a compensation in the memory element 20 with a combination of the jumpers 21, 22 by programming the number of pulses corresponding to a difference from the number of pulses N defined to a given brightness in the calculator 11.

Such an operation that an operator reads error data in a test instrument with his eyes and effects adjustment by rotating a semifixed resistor for adjustment takes much time and must be repeated since a relation between the errors and an amount of the rotation is indefinite, whereas in the present invention a compensation may be made with one time release of a shutter since a relation between errors and their compensation is distinctly defined.

In addition, as described in the first embodiment, it will be understood that it is possible in the memory system to simultaneously compensate exposure display data not shown.

FIG. 4 shows a third embodiment of the present invention which is applied to an exposure display circuit. In the third embodiment also, as described above, a given brightness, a lens having a given aperture, the number of steps for stopping down and an output to be obtained by an ISO sensitivity which is a given shutter speed display are previously programmed in the calculator 11 and data to compensate a difference between an actual display and a proper display are stored in the memory element 20 by applying the given brightness, the lens having a given aperture and a film sensitivity in ISO to a camera. Then, a jumper 21 is removed. After that, the calculator 11 reads the above compensation value from the memory element 20 in addition to the brightness, aperture, the number of steps for stopping down and the ISO value, and a result of the compensation calculation is displayed on a display element 50.

In FIG. 4, symbols CLK, Data, EN and R/W exhibit a clock signal, a serial signal line, an enable signal to gain access to the memory element 20 and a signal to select storing or reading out data from the memory element 20, respectively.

As such, when data are serially delivered to and received by the memory element 20, it is advantageous that the number of signal lines is greatly reduced.

In addition to the above compensation data, the memory element 20 retains the number of film frames which is preset by a switch 53 and required data to be stored such as an operation mode even when an exhaustion of a battery or while removal of a battery as occasion demands. These data are further displayed on the outside of the camera or within a view finder by a display driver 51 and a display element 52.

FIGS. 5 to 7 show details of the non-volatile digital memory element 20 which is used in the present invention. In the memory element 20, as shown in FIG. 5, a clock signal CLK is delivered to an address control circuit 61, and when either or both of a chip control signal EN and R/W are at the low level L, an address is subjected to increment or decrement by the clock signal CLK. Serial data which are delivered from the Data line in synchronism with the clock signal are converted to parallel data within a serial-parallel converter 62 and are delivered on an internal data bus 62a. The data delivered to the internal data bus 62a are further latched to a display data register 63 which is addressed by an address control circuit 61. After the data display is completed, data such as the number of film frames, ± a compensation amount and a photographing mode are delivered to and converted in parallel by the serial-parallel converter 62 to deliver them to the internal data bus 62a. The data are further latched to a memory register 64 which is addressed by the address control circuit 61.

A normal storing operation is completed as described above. While compensation data are stored the jumpers 19,21 (FIG. 4) are connected and thereafter the calculator 11 further delivers compensation data which are obtained by a given means to the Data line. Consequently, a compensation value which becomes parallel data by the serial-parallel converter 62 in the same manner as above is latched to the memory register 64 corresponding to a compensation value memory area (2) (n-2 to n) of a non-volatile memory 65, as shown in FIG. 6. Data such as the above-mentioned number of film frames, ± a compensation amount and a photographing mode excepting the compensation data are latched to the register 64 corresponding to a memory area (1) of the memory 65.

When transfer of the data is completed, data on the register 64 are stored in the memory 65, as they are, by turning the R/W and EN lines to the L level by the calculator 11. FIG. 7 shows an operational relation between R/W and EN.

When the jumpers 19, 21 are removed after the compensation value is stored in the memory area (2) as described above, the calculator 11 is unable to store a compensation value and after the jumper 19 is removed, the memory element 20 is also unable to store it in the compensation data area (2). Thereby, an erroneous change of compensation data is prevented.

When a power source is closed, the calculator 11, as occasion demands, turns the EN line to the L level to direct the memory element 20 to transfer data. When the EN line is at the L level, data in the memory 65 are delivered to the register 64 at one time and data in the register 64 are converted in parallel-serial by the serial-parallel converter 62 with increment or decrement of an address in the same way as when storing, to serially deliver them to the Data line. Thus, the non-volatile digital memory element operates.

A means for compensating control by reading out a compensation value stored in the non-volatile memory will be described hereinafter. By way of example, taking a direct value of four bits as compensation data and assuming that two bits of higher orders are integers and two bits of lower orders are decimals, the compensation can be made at intervals of 0.25 within the range of -2.0 through +1.75.

On the other hand, it is possible to use the stored value as an indirect value without using it as a direct compensation value. Specifically, when the compensation requires a multiplication, not an addition and subtraction, there are frequent occasions when a required series is a geometric one. At this time, in order to store a direct value a number of bits (memory capacity) are required. Consequently, in such case each value of four bit data is made to correspond to a value as shown in the following table.

______________________________________                                    
         F   1.834                                                        
         E   1.681                                                        
         C   1.542                                                        
         .   .                                                            
         .   .                                                            
         .   .                                                            
         2   0.595                                                        
         1   0.545                                                        
         0   0.5                                                          
______________________________________                                    

Then, it is possible to obtain a sufficient accuracy without increasing a capacity of the memory 20 by incorporating the above table into the calculator.