JP3703176B2 - Strobe device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention,A strobe device having an A / D converter for detecting the operation of the control target and a D / A converter for controlling the control target based on data of the A / D converterInIt is related.
[0002]
[Prior art]
Conventional,The exposure control method of the flashlight device is called so-called external measuring light, and the strobe reflected light from the subject is received by an optical system different from the shooting lens, and the received light amount is integrated. The one that stops the flash firing. Also called TTL dimming, it is widely used to stroboscopically stop the flash emission when it reaches a predetermined amount by integrating the light reflected from the subject through the photographic lens during flash photography. It has been broken.
[0003]
[Problems to be solved by the invention]
However, in the above-mentioned conventional external light metering, the center of the lens and the metering center of the strobe are difficult to match, and in a camera with interchangeable lenses, the shooting area of the taking lens may not match the metering area of the strobe. There was a problem that light errors were likely to occur. In the TTL film surface reflection dimming, the shooting area and the dimming area of the shooting lens coincide with each other, but there is a problem that the strobe exposure level changes due to the difference in film reflectance.
[0004]
In order to solve these problems, a strobe system that performs pre-flash toward the subject, measures the reflected light from the subject at the time of the pre-flash, and calculates the emission intensity of the main flash according to the photometric result Have proposed.
[0005]
This proposal will be described with reference to FIG. In the figure, 19 is a xenon tube which is a light emitting tube, 20 is a reflection shade, 21 is a Fresnel lens, 31 and 32 are light receiving elements, 200 is a microcomputer for controlling a strobe, and 201 is several tens of thousands. A DC / DC converter for generating a high voltage of V, 202 is a trigger circuit for applying a high voltage of several thousand volts to the xenon tube 19 to start light emission, 203 is a light emission control circuit, 204 and 205 are comparators, and 206 is data The selectors 207 and 209 are monitor circuits that amplify the output of the light receiving element, and 208 is an integrating circuit that integrates the output of the light receiving element 31.
[0006]
In this proposal, first, the data selector 206 selects the comparator 205 and performs the trigger circuit 202 in order to perform predetermined flat pre-emission.RWhen the trigger is emitted, light emission starts, and the light emission intensity of the flat light emission is just the light intensity centered on the voltage set at the non-inverting input terminal of the comparator 205, and the flat light emission is sustained. The light is received at 31 and integrated by the integration circuit 208 via the monitor circuit 207. After the pre-flash is completed, the output of the integration circuit 208 is read by the analog / digital conversion input terminal of the flash microcomputer 200, and during flash main light emission, the voltage obtained by adding or subtracting the light amount difference between the pre-light emission and the main light emission is added to and subtracted from the digital output. In addition to the analog conversion output DA0, the comparator 204 is selected by the data selector 206, and when the trigger circuit 202 gives a light emission trigger, the light emission starts, and the integration circuit 208 outputs the integrated output in the same manner as in the pre-light emission. When the voltage exceeds the DA0 output, the comparator 204 is inverted and the light emission is stopped.
[0007]
That is, if the pre-light emission and the main light emission are the same light emission amount, the same light emission amount should be obtained if the voltage read by the A / D conversion is directly set to the D / A conversion output. The light emission waveform in this case will be described with reference to FIG.
[0008]
In FIG. 12, “a” indicates a light emission waveform, and “b” indicates an output of the integration circuit 208. In the figure, when flat pre-emission is started at time t0, the integrated output b rises to a voltage level of c by the end of emission. This integrated output is read by AD which is an A / D conversion input of the microcomputer 200. Next, when light is emitted so that the main light emission has the same integral amount, if the same voltage level is set in the D / A conversion output DA0 of the microcomputer 200, the same light emission amount as that of the pre-light emission should be obtained.
[0009]
However, in actuality, even if an attempt is made to set the same voltage as the input voltage read by the A / D converter to the D / A converter, the mutual error D / A-A / D ERROR is as shown in FIG. As a result, the same light emission amount cannot be obtained.
[0010]
In addition, when using a D / A converter, a microcomputer equipped with a D / A conversion output is usually expensive, and in addition, it usually consists of a resistor ladder called R-2R, so the output impedance is high. 7FH: Hexadecimal notation (01111111B: Binary notation) and 80H (10000000B), etc., which are high and the resistance line greatly changes, have the problem that the D / A output is easily reversed.
[0011]
FIG. 14 shows a basic configuration of a D / A converter called the R-2R system described above. In FIG. 14, the configuration is an 8-bit configuration, D0 to D7 are input terminals 300 to 307, buffer amplifiers, and buffer amplifiers. Since the resistance connected in the horizontal direction to the output of this is R units and the resistance connected in the vertical direction is 2R units, it is called an R-2R type D / A converter. Here, in order to obtain complete unity increase, it is necessary to make the relative error of the resistance forming the resistance ladder extremely small, and for that purpose, it is necessary to make the resistance values uniform by trimming each resistance. Therefore, the yield is poor and expensive.
[0012]
This application has been made in view of the above, and is related to this application.DepartureIn the electronic equipment using the A / D and D / A conversion means for controlling the controlled object by the D / A conversion means based on the input signal read by the A / D conversion means, the A / D, D / A conversion meansPhase ofIt is an object to automatically correct the mutual error of the A / D and D / A conversion means and accurately control the controlled object without performing an adjustment action to match the mutual accuracy.
[0013]
[Means for Solving the Problems]
  In order to achieve the above object, the invention according to the present application isFor reading the amount of light emitted from the light source as digital data before shootingA / D conversion means and A / D conversion meansDigital data output fromBased on D / A conversion meansStrobe device that controls the amount of light emitted during shooting according to the set valueThe D / A conversion means outputs a reference signal of a predetermined level, the output is read by the A / D conversion means, and an error calculation means for calculating a mutual error between the reference signal and the read dataWhen,SaidError calculationCorrection means for correcting a mutual relationship between the A / D conversion means and the D / A conversion means based on error information calculated by the means;In the emission before the shooting, the flat emission is performed by periodically increasing / decreasing the emission intensity over a predetermined time, and in the emission at the time of shooting, the emission amount at the time of shooting is set according to the value set by the D / A conversion means. If the flash light emission is controlled, or the flat light emission that periodically increases or decreases the light emission intensity over the predetermined time, and the flash light emission is performed in the light emission during the photographing, the light emission amount during the photographing Prior to the control, the correction unit corrects the interrelation between the A / D conversion unit and the D / A conversion unit, and when the flat light emission is performed in the light emission at the time of photographing, the correction unit performs the A / D conversion. Does not correct the mutual relationship between the D conversion means and the D / A conversion meansIt is characterized by that.
[0014]
In the above configuration, the A / D conversion means converts the input voltage or input current as an analog signal into a digital signal, and the D / A conversion means converts the digital signal into an output voltage or output current as an analog signal. The error calculation means reads the reference voltage or reference current output from the D / A conversion means from the directly connected A / D conversion means, and calculates the mutual error. The means corrects a relative error between the D / A conversion means and the A / D conversion means.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 shows an electric circuit block when the present invention is applied to a strobe device.
[0016]
The strobe device is attached to a camera body (not shown) and performs light emission control in accordance with a signal from the camera. Reference numeral 19 denotes a xenon tube as a flash tube, which converts current energy into emission energy. Reference numerals 20 and 21 denote a reflector and a Fresnel lens, each of which plays a role of efficiently condensing light emission energy toward a subject. A strobe contact group 22 serves as an interface between the camera body and the strobe device. Reference numeral 31 denotes a first light receiving means such as a photodiode which is a light receiving means for monitoring the light emitted from the xenon tube 19, and directly measures the amount of light emitted from the strobe. 32 is a light receiving element such as a photodiode, which is a second light receiving means for monitoring the light emitted from the xenon tube 19. The light emission of the xenon tube 19 is limited by the output of the light receiving element 32 to control flat light emission.
[0017]
The stroboscopic microcomputer 200 is a circuit that controls the stroboscope according to a signal from a camera (not shown). The stroboscopic microcomputer 200 controls the light emission amount, the light emission intensity and light emission time of flat light emission, and the light emission angle.
[0018]
A DC / DC converter 201 as a booster circuit boosts the battery voltage to several hundred volts in accordance with an instruction from the strobe control circuit 200 and charges the main capacitor C1. R1 / R2 is a voltage dividing resistor provided for the strobe microcomputer 200 to monitor the voltage of the main capacitor C1. The stroboscopic microcomputer 200 performs A / D conversion on the divided voltage by an A / D converter with built-in stroboscopic microcomputer, thereby indirectly monitoring the voltage of C1 and controlling the operation of the DC / DC converter 201. The voltage of the main capacitor C1 is controlled to a predetermined voltage.
[0019]
Reference numeral 202 denotes a trigger circuit, which outputs a trigger signal via the strobe microcomputer 200 in response to an instruction from the camera microcomputer 100 when strobe light is emitted, and discharges the xenon tube 19 by applying a high voltage of several thousand volts to the trigger electrode of the xenon tube 19. And the charge energy stored in the main capacitor C1 is released as light energy through the xenon tube 19.
[0020]
Reference numeral 203 denotes a light emission control circuit using a switching element such as an IGBT.GadenWhen a pressure is applied, the Xenon tube 19 is turned on, a current is passed through the xenon tube 19, and when light emission is stopped, the current is cut off, thereby stopping the light emission.
[0021]
Reference numerals 204 and 205 denote comparators, 204 is used to stop light emission during flash light emission, which will be described later, and 205 is used to control light emission intensity during flat light emission. A data selector 206 selects the input from D0 to D2 according to the selection signals SEL1 and SEL2 from the strobe microcomputer 200, and outputs it to Y.
[0022]
Reference numeral 207 denotes a flash light emission control monitor circuit, which logarithmically compresses and amplifies the output of the light receiving element 31.
[0023]
An integration circuit 208 integrates the output of 207. A flat light emission control monitor circuit 209 amplifies the output of the light receiving element 32. An EEPROM 210 is a storage means for storing information necessary for various controls of the strobe. 211 is a known motor drive circuit, 212 is a zoom drive motor, 213 is a pinion gear, 214 is a rack gear, 215 is a zoom position detection encoder for detecting the position of the reflective shade 20, 216 is a dimming confirmation display LED indicating that light emission is possible is there.
[0024]
Next, each terminal of the flash microcomputer 200 will be described. CK is an input terminal for a synchronous clock for serial communication with the camera, DI is an input terminal for serial communication data, DO is a data output terminal for serial communication, and CHG is an output terminal for transmitting the strobe light emission status to the camera as a current. , X is a light emission signal input terminal from the camera, ECK is a communication clock for performing serial communication with a writable storage means such as EEPROM or flash ROM which is a storage means connected to the outside of the flash microcomputer 200 EDI is a serial data input terminal from the storage means, EDO is a serial data output terminal to the storage means, SELE is an enable terminal that permits communication with the storage means, and is enabled at Lo for explanation. Disable with Hi.
[0025]
In this example, the storage means is set outside the strobe microcomputer, but it goes without saying that it is the same even if it is built in the strobe microcomputer.
[0026]
POW is an input terminal for inputting the state of the power switch 215, OFF is an output terminal for turning off the strobe when connected to the power switch 215, and ON is a strobe when connected to the power switch 215. In the power ON state, the POW terminal is connected to the ON terminal. At that time, the ON terminal is in the high impedance state, the OFF terminal is in the Lo state, and vice versa in the power OFF state. CHG_LED is a display output terminal for displaying that light can be emitted.
[0027]
STOP is an input terminal for a light emission stop signal. For the sake of explanation, the light emission stop state is set to Lo. SEL0 and SEL1 are output terminals for instructing the input selection of the data selector 206. When the combination of SEL0 and SEL1 is (SEL1, SEL0) = (0, 0), the D0 terminal is connected to the Y terminal. Similarly, when (0, 1), the D1 terminal is selected, and when (1, 0), the D2 terminal is selected.
[0028]
DA0 is a D / A output terminal built in the flash microcomputer 200, and outputs the comparator level of the comparators 204 and 205 as an analog voltage. TRIG is a trigger signal output terminal for instructing the trigger circuit 202 to emit light. CNT is an output terminal for controlling the start / stop of oscillation of the DC / DC converter 201. For the purpose of explanation, charging starts at Hi and charging stops at Lo. INT is a terminal for controlling the start / prohibition of integration of the integration circuit 208. The integration is prohibited by Hi and the integration is enabled by Lo.
[0029]
AD0, AD1, and AD2 are A / D input terminals that convert input voltages into digital data so that they can be processed inside the microcomputer 200. AD0 monitors the voltage of the main capacitor C1, AD1 monitors the integrated output voltage of the integrating circuit 208, and AD2 is a monitor input terminal for detecting an error of the A / D converter and D / A converter, which will be described in detail later.
[0030]
Z0 and Z1 are control output terminals for controlling the motor control circuit 211 that drives the zoom drive motor 212, ZM0, ZM1, and ZM2 are input terminals for inputting the zoom position detection encoder 215, and COM0 is a ground for the zoom position detection encoder 215. This is a common terminal for drawing a current corresponding to the level.
[0031]
Next, the light emission operation will be described.
[0032]
<Pre-flash>
When the strobe is ready to emit light during the basic strobe operation described above, the pre-flash emission intensity and duration are communicated to the strobe from the camera (not shown) via the communication terminal, and pre-flash is instructed. Is done.
[0033]
The strobe microcomputer 200 sets a predetermined voltage in DA0 in accordance with a predetermined light emission intensity signal instructed from the camera body. Next, Lo and Hi are output to SEL1 and SEL0, and the input D1 is selected. At this time, since the xenon tube 19 has not yet emitted light, the photocurrent of the light receiving element 32 hardly flows, and the comparator 205ofSince the output of the monitor circuit 209 input to the inverting input terminal is not generated and the output of the comparator 205 is Hi, the light emission control circuit 203 is turned on. Next, when a trigger signal is output from the TRIG terminal, the trigger circuit 202 generates a high voltage to excite the xenon tube 19 and light emission is started.
[0034]
On the other hand, the stroboscopic microcomputer 200 instructs the integration circuit 208 to start integration after a predetermined time from the occurrence of the trigger, and the integration circuit 208 outputs the output of the monitor circuit 207, that is, the logarithmically compressed photoelectric output of the light receiving element 31 for light intensity integration. At the same time as the integration is started, a timer for counting a predetermined time is started. The reason why the start of integration is delayed from the generation of the trigger is to prevent the integration circuit from integrating noise other than the optical signal due to the noise caused by the generation of the trigger. This is because there is a delay of several μsec.
[0035]
When pre-emission is started, the photocurrent of the light emission intensity control light-receiving element 32 for flat emission increases, the output of the monitor circuit 209 increases, and a predetermined comparator voltage set as the non-inverting input of the comparator 205 When it becomes higher, the output of the comparator 205 is inverted to Lo, and the light emission control circuit 203 cuts off the light emission current of the xenon tube 19 and a discharge loop is formed. However, a diode D1 and a coil L1 form a circulation loop to emit light. The current gradually decreases after the overshoot due to the delay in the circuit is settled.
[0036]
As the light emission current decreases, the light emission intensity decreases, so the photocurrent of the light receiving element 32 decreases, the output of the monitor circuit 209 decreases, and when the output falls below a predetermined comparison level, the output of the comparator 205 again becomes Hi. , The light emission control circuit 203 is turned on again to form a discharge loop of the xenon tube 19, and the light emission current increases and the light emission intensity also increases. As described above, the comparator 205 repeatedly increases and decreases the emission intensity in a short period around the predetermined comparator voltage set to DA0, and as a result, the flat emission that continues emission at the desired substantially constant emission intensity. Can be controlled. When the above-mentioned light emission time timer is counted and the predetermined pre-light emission time elapses, the stroboscopic microcomputer 200 sets the SEL1 and SEL0 terminals to Lo and Lo, the input of the data selector 206 is selected as D0, that is, the Lo level input, and the output is The light emission control circuit 203 is forcibly set to the Lo level, interrupts the discharge loop of the xenon tube 19, and ends the light emission.
[0037]
At the end of light emission, the stroboscopic microcomputer 200 reads the output of the integration circuit 208 integrating the pre-light emission from the A / D input terminal AD1, performs A / D conversion, and reads the integrated value, that is, the light emission amount at the time of pre-light emission as a digital value. I can do things.
[0038]
During the pre-emission, the camera (not shown) measures the exposure amount EVF during pre-emission based on the reflected light from the subject from the output of the light receiving element 29 from the output of the light receiving element 29, and sets the strobe light to an appropriate amount with respect to natural light. Therefore, the main light emission amount at the time of photographing is calculated, and the strobe light emission amount of the main light emission following the pre-light emission is determined.
[0039]
<Main flash control>
Next, main light emission control will be described. In the main flash sequence, if the shutter speed of the camera (not shown) is faster than the flash synchronization speed, the flash intensity and flash time for flash emission by the flat flash will be sent from the camera via serial communication via the communication lines S0 to S2. Is done. In addition, when the shutter speed is equal to or less than the flash synchronization speed, the camera instructs the light emission intensity for light emission by flash light emission.
[0040]
The emission intensity in the main emission is defined as relative information with respect to the emission intensity in the pre-emission.
[0041]
Next, main light emission control during flat light emission will be described.
[0042]
<Flat main flash control>
The stroboscopic microcomputer 200 obtains the appropriate light emission intensity of the main light emission quantity based on the light emission intensity corresponding to the instructed main light emission quantity, and sets a predetermined voltage at the appropriate light emission intensity to the DA0 output. That is, if the emission intensity is the same as that of pre-emission, the same control voltage for pre-emission is output from the DA0 output terminal of the flash microcomputer 200. If there is a difference from pre-emission, a voltage obtained by adding or subtracting the difference is output from the DA0 output terminal. .
[0043]
Next, Lo and Hi are output to SEL1 and SEL0, and the input D1 is selected. At this time, since the xenon tube 19 has not yet emitted light, the photocurrent of the light receiving element 32 hardly flows, the output of the monitor circuit 209 input to the inverting input terminal of the comparator 205 is not generated, and the output of the comparator 205 is Hi. Therefore, the light emission control circuit 203 is turned on. Next, when a trigger signal is output from the TRIG terminal, the trigger circuit 202 generates a high voltage to excite the xenon tube 19 and light emission is started. In addition, the strobe microcomputer 200 starts a timer that counts the time instructed by the camera when the light emission starts. Since the emission intensity control of flat emission is the same as the pre-emission control, the description thereof is omitted.
[0044]
After the above-mentioned light emission time timer is counted and the predetermined light emission time has elapsed, the stroboscopic microcomputer 200 sets the SEL1 and SEL0 terminals to Lo and Lo, and the input of the data selector 206 is selected as D0, that is, the Lo level input, and the output is The light emission control circuit 203 cuts off the discharge loop of the xenon tube 19 and the light emission ends.
[0045]
<Flash main light emission control>
Next, flash main light emission control will be described. The stroboscopic microcomputer 200 obtains an appropriate light emission intensity of the main light emission quantity based on the light emission intensity corresponding to the main light emission quantity instructed from a camera (not shown), and sets a predetermined voltage that provides the appropriate light emission intensity to the DA0 output. The predetermined voltage includes a voltage corresponding to a relative light emission amount and a voltage corresponding to an error correction value to be described later with respect to the integrated output read from AD1 at the end of the pre-light emission.AddObtain by subtraction.
[0046]
Next, Hi and Lo are output to SEL1 and SEL0, and the input D2 is selected. At this time, since the integration circuit is in an operation-prohibited state, the output of the integration circuit 208 inputted to the inverting input terminal of the comparator 204 is not generated and the output of the comparator 204 is Hi, so that the light emission control circuit 203 becomes conductive.
[0047]
Next, when a trigger signal is output from the TRIG terminal, the trigger circuit 202 generates a high voltage to excite the xenon tube 19 and light emission is started. Further, the strobe microcomputer 200 sets the integration start terminal INT to Lo level 10 seconds after the trigger noise by the trigger application is settled and the actual light emission is started, and the integration circuit 208 sends the output from the sensor 31 to the monitor circuit 207. Integrate through. When the integrated output reaches a predetermined voltage set by DA0, the comparator 204 is inverted, the light emission control circuit 203 is cut off through the data selector 206, and light emission stops.
[0048]
On the other hand, the stroboscopic microcomputer 200 monitors the STOP terminal. When the STOP terminal is inverted and the light emission stops, the SEL1 and SEL0 terminals are set to Lo and Lo to set the forced light emission prohibition state, and the integration start terminal is inverted to perform integration. Then, the light emission process ends.
[0049]
<Correction calculation>
Next, correction of D / A-A / D relative error, which is an important point of the present invention, will be described.
[0050]
In the case of the flat main light emission with respect to the flat pre-light emission described above, the main light emission is not controlled based on the output voltage of the integrating circuit 208 obtained by integrating the light emission amount of the pre-light emission. The emission intensity of pre-flash and main flash can be controlled simply by setting the control voltage. However, when the main flash is flash, the integration circuit integrates the flash output during pre-flash as described in the previous example. The output voltage is read from the A / D conversion input terminal AD0 as an integration voltage, and the voltage corresponding to the difference in the amount of main light emission is added to or subtracted from the aforementioned integration voltage, and the aforementioned relative error of A / D-D / A is corrected. The main emission control voltage is obtained by adding / subtracting the correction voltage to be added. The correction calculation method will be described in detail below.
[0051]
FIG. 2 is a flowchart showing a program built in the stroboscopic microcomputer 200 for obtaining a relative error of the A / D-D / A converter performed at the time of resetting and when the power of the stroboscope is turned on. In the following flowcharts, “#” is added as a mark indicating a step.
[0052]
[Step 101] Initialization processing of a RAM (not shown) and each port in the flash microcomputer 200 is performed at reset or when the power is turned on.
[0053]
[Step 102] A predetermined voltage VDA is output to the D / A conversion output terminal DA0 for A / D-D / A relative error measurement. Considering the case where this voltage is higher than the maximum readable voltage of the A / D converter, a voltage slightly lower than the maximum voltage that can be output by the D / A converter, for example, the D / A converter is 8 bits. Preferably outputs about F0H.
[0054]
[Step 103] The reference voltage of the D / A conversion output output in Step 102 is read from the AD2 input which is an A / D conversion input terminal and is set as VAD.
[0055]
[Step 104] The relative error DA_ERROR of the D / A conversion output and the A / D conversion input is obtained by the following equation.
[0056]
DA_ERROR = VDA−VAD For example, when the D / A conversion output VDA = F0H, if the A / D conversion input is F0H, the relative error is 0. If there is a difference, the difference is set as a relative error in the strobe microcomputer 200. Is stored in a RAM (not shown).
[0057]
[Step 105] The D / A conversion output DA0 that was outputting the VDA is inhibited from being output, and the relative error measurement process is terminated.
[0058]
During the relative error storing process, it is preferable that the oscillation of the DC / DC converter 201 that is a strong noise generation source is prohibited. The relative error measurement process may be performed every time the D / A or A / D converter is used, but it is sufficient to perform the relative error measurement process only at the time of resetting or power-on.
[0059]
  nextFlash mainA method for setting the D / A conversion output DA0 for controlling the light emission amount during light emission will be described with reference to FIG. FIG. 3 is a flowchart showing a program built in the flash microcomputer 200.
[0060]
[Step 201] The emission intensity data of the main emission is received from a camera body (not shown).
[0061]
[Step 202] At the end of preliminary light emission, the integrated output voltage is read from AD0 which is the A / D conversion input terminal of the flash microcomputer 200, and the integrated output by the preliminary light emission stored in the RAM (not shown) in the flash microcomputer 200 is read.
[0062]
[Step 203] In step 104, DA_ERROR which is an A / D-D / A relative error stored in a RAM (not shown) in the microcomputer 200 is read.
[0063]
[Step 204] D / A set raw value of main light emission obtained by adding the difference between the main light emission intensity received in Step 201 and the preliminary light emission obtained in Step 201 to the integrated output read out in Step 202, and read out in Step 203. The A / D-D / A relative error correction is calculated from DA_ERROR by the following formula.
[0064]
ΔDA # ERROR = DA # ERROR * DA # SET / VDA
VDA: Reference setting value for A / D-D / A error measurement
DA # ERROR: Measured relative error during A / D-D / A error measurement
DA # SET: Raw value to be set for D / A conversion output during main flash
[0065]
That is, the D / A output error at the time of main light emission is obtained in a proportional relationship with respect to the case where the relative error at the time of predetermined D / A output at the time of error correction is DA_ERROR.
[0066]
[Step 205] The relative error correction value obtained in Step 204 is added to the D / A conversion output raw value DA_SET obtained in Step 204, and the resultant light emission intensity is output to DA0 which is a D / A conversion output.
[0067]
[Step 206] Based on the main light emission intensity stopped in step 205, the main light emission control is performed, and the light emission process is terminated.
[0068]
In the above embodiment, the D / A converter and the A / D converter are described as the voltage mode. However, it is needless to say that the relative error can be similarly corrected in the D / A and A / D converter operating in the current mode. . In the above embodiment, the relative error is measured and stored only at one point, and during that time, the relative error is obtained by interpolation calculation. However, if the storage capacity of the storage unit allows, more D / A output is possible. By measuring and storing the relative error at, it is possible to reduce the relative error even when there is a non-linear region in the D / A output. In the above-described embodiment, the description is applied to the strobe device. However, it goes without saying that any electronic device using a D / A or A / D converter can be applied.
[0069]
As explained above, the first implementationFormThen, at the time of resetting, before turning on the power, or before using the D / A or A / D converter, a reference signal of a predetermined level from the D / A converter.TheWhen the output is read by the A / D converter, the mutual error is stored in the storage means, and the controlled object is controlled using the A / D and D / A converters, Correcting the relationship between A / D and D / A conversion based on this makes it possible to perform accurate control, and a strobe device to which this is applied has made it possible to perform high-precision strobe photography.
[0070]
(Second Embodiment)
In the second embodiment, the mutual error correction is performed at the time of reset, power-on, or before using the A / D and D / A converters described in the first embodiment. In the embodiment, the relative error is measured at the time of adjustment, the data corresponding to the relative error is stored in the writable storage means, and when the A / D or D / A converter is used, the relative data stored in the writable storage means is stored. By reading out the data corresponding to the error and performing the relative error correction, it is possible to use a high-speed and accurate A / D and D / A converter that does not require time for error measurement each time it is used. .
[0071]
The hardware configuration in the second embodiment is the same as that in the first embodiment, and a description thereof will be omitted.
[0072]
FIG. 4 is a flowchart showing a program built in the stroboscopic microcomputer 200 of the second embodiment for obtaining the relative error of the A / D-D / A converter performed at the time of adjustment.
[0073]
[Step 301] An error measurement process of the A / D-D / A converter is started by receiving a specific serial communication via the communication terminal 22 with the outside.
[0074]
[Step 302] A predetermined voltage VDA is output to the D / A conversion output terminal DA0 for A / D-D / A relative error measurement. Considering the case where this voltage is higher than the maximum readable voltage of the A / D converter, a voltage slightly lower than the maximum voltage that can be output by the D / A converter, for example, the D / A converter is 8 bits. Preferably outputs about F0H.
[0075]
[Step 303] The reference voltage of the D / A conversion output output in Step 302 is read from the AD2 input which is an A / D conversion input terminal and is set as VAD.
[0076]
[Step 304] The relative error DA_ERROR between the D / A conversion output and the A / D conversion input is obtained by the following equation.
[0077]
DA_ERROR = VDA-VAD, for example, when D / A conversion output VDA = F0H, if the A / D conversion input is F0H, the relative errorButIf it is 0 and there is a difference, the difference is regarded as a relative error.
[0078]
[Step 305] The relative error is stored in the EEPROM 210 which is a writable storage means.
[0079]
[Step 306] The output of the D / A conversion output DA0 that has output the VDA is prohibited, and the relative error measurement process is terminated.
[0080]
As in the first embodiment, it is preferable that the oscillation of the DC / DC converter 201 serving as a strong noise generation source is prohibited during the relative error storing process.
[0081]
Next, a method of setting the D / A conversion output DA0 for controlling the light emission amount during flash main light emission will be described with reference to FIG. FIG. 5 is a flowchart showing a program built in the flash microcomputer 200.
[0082]
[Step 401] The emission intensity data of the main emission is received from a camera body (not shown).
[0083]
[Step 402] At the end of preliminary light emission, the integrated output voltage is read from AD0 which is an A / D conversion input terminal of the flash microcomputer 200, and the integrated output by preliminary light emission stored in a RAM (not shown) in the flash microcomputer 200 is read.
[0084]
[Step 403] DA_ERROR, which is an A / D-D / A relative error, stored in the EEPROM, which is a writable storage means in Step 305, is read.
[0085]
[Step 404] D / A setting raw value = DA_SET for main light emission obtained by adding the difference between the main light intensity received in step 401 and the preliminary light emission received in step 401 to the integrated output read in step 402, and read in step 403. The A / D-D / A relative error correction amount is calculated from the DA_ERROR by the following equation.
[0086]
ΔDA # ERROR = DA # ERROR * DA # SET / VDA
VDA: Reference setting value for A / D-D / A error measurement
DA # ERROR: Measured relative error during A / D-D / A error measurement
DA # SET: Raw value to be set for D / A conversion output during main flash
[0087]
That is, the D / A output error at the time of main light emission is obtained in a proportional relationship with respect to the case where the relative error at the time of predetermined D / A output at the time of error correction is DA_ERROR.
[0088]
[Step 405] The relative error correction value obtained in step 404 is added to the D / A conversion output raw value DA_SET obtained in step 404, and the resultant light intensity is output to DA0, which is a D / A conversion output.
[0089]
[Step 406] The main light emission control is performed based on the main light emission intensity stopped in step 405, and the light emission process is terminated.
[0090]
In the above embodiment, the D / A converter and the A / D converter are described as the voltage mode. However, the relative error can be similarly corrected in the D / A and A / D converter operating in the current mode. Needless to say.
[0091]
In the above embodiment, the relative error is measured and stored only at one point, and during that time, the relative error is obtained by interpolation. However, if the storage capacity of the writable storage means allows, more D By measuring and storing the relative error at the / A output, the relative error can be reduced even when there is a non-linear region in the D / A output. In the above-described embodiment, the description is applied to the strobe device. However, it goes without saying that any electronic device using a D / A or A / D converter can be applied.
[0092]
As described above, in the second embodiment, the relative error measurement process is started by receiving a specific serial communication command at the time of adjustment, and a reference signal of a predetermined level is output from the D / A converter. Is read by the A / D converter, the mutual error is stored in a writable storage means, and the control object is controlled using the A / D and D / A converters, the A based on the stored error. By correcting the relationship between / D and D / A conversion, it becomes possible to perform high-speed and accurate control that does not require time for error measurement each time it is used. High-speed and high-precision flash photography is now possible.
[0093]
(Reference example)
6 to 10 show reference examples of the present invention. Reference exampleThen, as an embodiment of the A / D converter used in the first and second embodiments, a substantially DC voltage obtained by smoothing an output signal of a PWM (pulse width modulation) system by a filter means is used. The voltage to be controlled is controlled by using a low-cost D / A converter capable of monotonically increasing.
[0094]
FIG.Reference example1 is a block diagram showing the configuration of the strobe device in FIG. 1. The same members as those in FIG.
[0095]
In FIG. 6, reference numeral 220 denotes a D / A converter for converting a PWM (pulse width modulation) signal into a substantially direct current through a low-pass filter, and its internal configuration is shown in FIG. 7, 221, 224, and 227 are resistors, 222, 225, and 228 are capacitors, 223 and 226 are operational amplifiers, and FIG. 8 shows the signal waveforms. In FIG. 8, a rectangular wave is a PWM signal output from the strobe microcomputer 200 and input to the D / A converter, and the ON / OFF ratio is variable at a constant frequency.
[0096]
V1 is the output V1 of the operational amplifier 223, which is the first stage active filter, and D / A OUT is the output of the second stage active filter. Various other configurations are known as filter configurations, but simple active filter stacking is excellent for blocking the spike component of the input PWM signal. The output voltage characteristic is proportional to the DUTY ratio and has a monotonous increase / decrease characteristic, and an A / D converter having an excellent characteristic with a low output impedance can be realized with a simple configuration.
[0097]
However, in order to reduce the ripple of the D / A output, it is necessary to sharpen the cutoff characteristics of the filter and increase the high-frequency component removal capability. Therefore, it is impossible to cope with the fluctuation of the D / A output, and the rise time at the start of the output of the D / A converter becomes long.
[0098]
Therefore,Reference example of the present inventionThen, in consideration of the rise time of the D / A converter, the output of the D / A converter is given to the filter means before being used for the control of the emission intensity, and the output of the filter means becomes in a substantially steady state. The light emission control is performed around the time.
[0099]
FIG.Reference example of the present invention2 shows a flat light emission waveform and an output state of a pulse width modulation type D / A converter for controlling the flat light emission intensity. In the figure, a is a light emission waveform at the time of pre-light emission, a ′ indicates an output of the D / A converter at the time of pre-light emission, b is a light emission waveform at the time of main light emission, and b ′ is a main light emission. The output of the D / A converter at the time is shown. As shown in the figure, the D / A converter is started at time t0 prior to the pre-light emission time t1. Similarly, at the time of main light emission, the D / A converter is started at time t4 prior to time t5 of main light emission. FIG. 10 is designed to start up the D / A converter faster than in FIG. We are trying to speed up the time.
[0100]
In addition,Reference exampleIn the D / A converter, the rise time of the D / A converter described above is used instead of the digital data set in the D / A converter described in the first and second embodiments. In consideration of the above, it may be set as a PWM signal having a predetermined DUTY ratio, and the relative error correction between the D / A converter and the A / D converter may be performed in the same manner as in the first and second embodiments. The description is omitted.
[0101]
As explained above,Reference exampleThen, an effect that a high-precision strobe device can be realized at low cost by controlling light emission of the strobe with a substantially DC voltage obtained by smoothing a PWM (pulse width modulation) type output signal with a filter means. There is.
[0102]
(Relationship between claims and embodiments)
In the above embodiment, the AD0, AD1, and AD2 input terminals of the strobe microcomputer 200 correspond to A / D conversion means, and the DA0 output terminal of the strobe microcomputer 200The childIt corresponds to a D / A conversion circuit, the stroboscopic microcomputer 200 corresponds to error calculation means, the RAM or EEPROM 210 (not shown) in the stroboscopic microcomputer 200 corresponds to storage means, and the stroboscopic microcomputer 200 performs A / D and D / A conversion. The correction means for correcting the mutual relationship between meansWinThe
[0103]
【The invention's effect】
  In the invention according to claim 1,When performing a flat flash before shooting and flashing during shooting,A reference signal of a predetermined level is output from the D / A conversion means, the output is read by the A / D conversion means, and the mutual error between the reference signal and the read data is an error.CalculationCalculated by means,SaidError calculationBased on the error information calculated by the means, the A / D-D / A conversion meansMutualSince the relationship is corrected, accurate control is possible.,Flash photography is possible with high accuracy.On the other hand, when flat light emission is performed before shooting and flat light emission is performed even during shooting, the interrelation between the A / D-D / A conversion means is not corrected.
[Brief description of the drawings]
FIG. 1 is an electric circuit block diagram showing an electrical configuration of a strobe according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing a program for performing relative error storage according to the first embodiment;
FIG. 3 is a flowchart showing a main light emission operation of the strobe of the first embodiment.
FIG. 4 is a flowchart showing a program for performing relative error storage according to the second embodiment.
FIG. 5 is a flowchart showing a main light emission operation of the strobe of the second embodiment.
FIG. 6 shows the present invention.Reference exampleThe electric circuit block diagram which shows the electric constitution of the electronic flash.
FIG. 7 shows the present invention.Reference exampleThe electric circuit diagram which shows the pulse width modulation type D / A conversion circuit which concerns on.
8 is an operation waveform diagram of the pulse width modulation type D / A conversion circuit of FIG. 7;
FIG. 9Reference example of the present inventionThe figure which shows the operation waveform of the strobe light emission waveform at the time of the strobe light emission control which concerns on, and a pulse width modulation type D / A converter circuit.
FIG. 10Reference example of the present inventionThe figure which shows the operation waveform of the strobe light emission waveform at the time of the strobe light emission control which concerns on, and a pulse width modulation type D / A converter circuit.
FIG. 11 is a block diagram of an electric circuit showing an electrical configuration of a conventional strobe device.
FIG. 12 is a diagram showing a light emission waveform of a conventional strobe device.
FIG. 13 is a diagram showing a light emission waveform of a conventional strobe device.
FIG. 14 is an electric circuit showing a known R / 2R type D / A conversion circuit.
[Explanation of symbols]
19 Xenon tube
200 Strobe microcomputer
203 Light emission control circuit
204,205 Comparator
207 Integration circuit
210 EEPROM

Claims (1)

A / D conversion means for reading the light emission amount of the light source in light emission before photographing as digital data , and according to the value set by the D / A conversion means based on the digital data output from the A / D conversion means With a strobe device that controls the amount of light emitted during shooting ,
An error calculating means for outputting a reference signal of a predetermined level from the D / A converting means, reading the output by the A / D converting means, and calculating a mutual error between the reference signal and the read data; and the error A correction unit that corrects a mutual relationship between the A / D conversion unit and the D / A conversion unit based on error information calculated by the calculation unit ;
In the pre-shooting light emission, the flat light emission is periodically increased / decreased over a predetermined time, and in the light emission during the shooting, the light emission amount at the time of shooting is controlled according to the value set by the D / A conversion means. Either flash light emission or flat light emission that periodically increases or decreases the light emission intensity over the predetermined time, and when the flash light emission is performed in the light emission at the time of shooting, control of the light emission amount at the time of shooting Prior to the correction, the correction unit corrects the interrelation between the A / D conversion unit and the D / A conversion unit, and the correction unit performs the A / D conversion when performing the flat emission in the emission at the time of photographing. A strobe device characterized by not correcting the mutual relationship between the means and the D / A conversion means .

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