JP3408310B2 - Camera ranging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active type distance measuring device for a camera.

[0002]

2. Description of the Related Art An active distance measuring device used in a camera includes a light projecting portion that projects distance measuring light toward a subject and a light receiving portion that is arranged apart from the light projecting portion by a fixed baseline length. And a signal processing unit that processes a signal from the light receiving unit. A light emitting diode (IRED) that emits near-infrared light is generally used for the light projecting unit, and near-infrared light from the light-emitting diode is projected toward a subject as distance measuring light. Of the distance measuring light,
The light reflected by the subject passes through the light receiving lens and enters the light receiving portion. For example, a PSD (Position Sensiti
ve Devise) is used, and a photoelectric signal corresponding to the incident position of light appears at the pair of output terminals. And
Since the distance to the object can be calculated by performing the triangulation calculation in the signal processing unit based on this photoelectric signal, the focus position of the taking lens can be determined correspondingly.

The output level of the photoelectric signal appearing at the pair of output terminals of the PSD varies depending on whether the distance to the subject is short or far, but it depends on the output level by taking the ratio of these photoelectric signals. It is possible to detect the incident position of light on the PSD without performing the process. However, the detection accuracy tends to vary between when the ratio of both signals is obtained while the output level of the photoelectric signal is low, and when the ratio is obtained while the output level is high.

Further, since the photoelectric signals from the PSD are analog amounts, it is usual to convert these signals into digital amounts and then obtain the ratio. However, the photoelectric signals with low output levels are AD-converted respectively. There is still a difference in calculation accuracy between the case where the ratio is obtained and the case where the ratio is obtained by AD converting each photoelectric signal having a high output level. In order to eliminate such inconvenience, as described in Japanese Patent Laid-Open No. 4-199013, an amplifier system including a gain control circuit for each channel is connected to the output terminal of the PSD, and photoelectric signals from both channels are AD-converted. When doing, feedback is applied to the gain control circuit so that the sum of each digital value becomes a value in a certain range,
Amplification of each photoelectric signal with the same amplification factor is performed.

[0005]

However, since the circuit elements used for each channel, including the above gain control circuit, have variations, the gain itself is not constant between both channels. Therefore, in order to perform the gain control as described above, it is first necessary to equalize the amplification factors of both channels, and therefore, highly accurate circuit components constituting the amplifier system have been required. Even if high precision circuit parts are used, some variation still cannot be avoided.Therefore, at least one channel must be equipped with a circuit element for adjustment such as a potentiometer to adjust the gain of both channels. It is necessary, and it is difficult to reduce the cost because of the use of high-precision circuit parts and the adjustment work.

Further, in order to improve the distance measurement accuracy, a method is adopted in which the object is projected a plurality of times, the photoelectric signal is sampled each time, the distance calculation is performed, and the object distance is determined from the average value. However, the frequency of light emission is, for example, 1 kHz.
At a high frequency of about z, the signal level becomes small and the S / N ratio deteriorates unless the timing of sampling the photoelectric signal is accurately adjusted to the peak of the photoelectric signal. Conventionally, an adjusting element excellent in high-frequency response is indispensable for these adjustments, and the adjusting work is troublesome.

The present invention has been made in order to solve the above-mentioned problems in the prior art, and does not require a troublesome adjustment work between both channels, while using circuit parts with low accuracy, and has sufficient distance measuring accuracy. An object of the present invention is to provide a distance measuring device for a camera that can be maintained at

[0008]

In order to achieve the above object, the present invention provides a sub memory separately from a main program memory storing a distance measuring program, and adjusts circuit characteristics between channels to this sub memory. The necessary data can be written in advance for each camera. As such data, there are the maximum value and the minimum value of the gain determined by the gain control circuit. These values reduce the accuracy of the distance measurement calculation due to the insufficient level of the output of the light receiving element, or the amplifier of the light receiving element and each channel. It is decided in consideration of the dynamic range of the system. Further, when the gain control is performed to set the output level of the photoelectric signal to an appropriate range, if the gain value is not included between the maximum value and the minimum value previously written in the sub memory, , It means that the gain for distance measurement cannot be set in an appropriate range, but in this case, the focus position of the shooting lens is set to the hyperfocal position, or the subject distance is too short and the photoelectric signal By issuing a short-distance warning indicating that the overflow has occurred, meaningless distance measurement processing is prevented from being continued.

Further, when there is a difference in gain control method for each channel, data relating to the gain adjustment difference is written in the sub memory, and the timing for sampling the photoelectric signal at the peak of the waveform is adjusted. Timing data can be written. By appropriately using these data when executing the distance measurement program, accurate distance measurement can be performed without accurately matching the electrical characteristics between the channels.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 2 schematically showing the electrical construction of a camera using the present invention, a light projecting section 2 comprises an IRED 3 which emits near infrared light as distance measuring light, and a light projecting lens 4. , The optical axis 4a of the projection lens 4 is the optical axis 5a of the taking lens 5.
It is almost parallel to. The ranging light from IRED3
The light projecting lens 4 forms a beam having a small diameter and directs it toward the center of the photographic screen.

The light receiving portion 7 is composed of a light receiving lens 8 and a PSD 9, and the optical axis 8a of the light receiving lens 8 is also the optical axis 5 of the photographing lens.
It is almost parallel to a. The PSD 9 outputs a signal according to the amount of incident light and the incident position to each output terminal 9a, 9b.
Output from. As is clear from FIG. 2, the shorter the distance to the subject S1, the more the reflected light is incident on the side of the terminal 9b of the PSD 9, but the sum and difference between the photoelectric signals obtained from the output terminals 9a and 9b, respectively. By taking the ratio, it is possible to obtain a signal corresponding to the incident position without depending on the amount of incident light. Note that the PSD 9 does not have a discriminating action in the horizontal direction, and if the incident heights in the vertical direction are the same, the difference between the photoelectric signals from the output terminals 9a and 9b and the difference will not occur even if the incident positions in the horizontal direction are different. And the ratio will be equal.

The IRED 3 is controlled by the signal from the autofocus IC 12 via the driver 11. The autofocus IC 12 executes a predetermined distance measuring sequence in accordance with a command from the microcomputer 14 to operate the driver 11, and
Amplify the photoelectric signals from the output terminals 9a and 9b of the PSD 9,
The sample and hold processing is performed and the result is input to the microcomputer 14.

The microcomputer 14 has a built-in AD converter 15 and has an autofocus IC 12
The photoelectric signal input from each channel from is converted from an analog amount to a digital amount. The microcomputer 14 performs distance measurement calculation based on the signal thus input for each channel, and calculates a distance signal corresponding to the distance to the subject. Then, in response to this distance signal, the motor 17 is driven via the lens moving circuit 16, the photographing lens 5 moves to the set position corresponding to the subject distance, and focusing is performed.

A general-purpose microcomputer is used as the microcomputer 14, and photometric data which is detected by the photometric circuit 19 and then digitally converted by the AD converter 20 is also input. The microcomputer 14 calculates the optimum exposure condition based on the photometric data, drives the stepping motor 22 via the exposure control circuit 21, and causes the program shutter 24 to operate.
Is opened and closed at an aperture value and shutter speed that satisfy the optimum exposure conditions. Also, the film transfer circuit 25 is used after photographing.
Thus, the film feeding motor 26 is driven to feed the film one frame.

The microcomputer 14 is provided with a connection terminal 14a for external equipment, and various adjustment data is sent to the terminal so that the operation of the distance measuring device can be confirmed when the camera is completely assembled and the operation can be performed accurately. It is used when inputting from the machine 28 to the micro computer 14. A part of the data input from the terminal unit 28 is an EEPROM (Electrically Erasa) which is used as a sub memory for storing the data necessary for executing the ranging process.
ble programmable ROM) 29.

FIG. 1 schematically shows the structures of the autofocus IC 12 and the microcomputer 14. P
The photoelectric signals output from the output terminals 9a and 9b of the SD9 are preamplifiers 30a and 30 for the respective channels.
b, gain control circuits 31a and 31b, sample hold circuits 32a and 32b, buffer amplifier 33a,
It is input to the AD converter 15 of the microcomputer 14 via 33b and the main amplifiers 34a and 34b. In addition, the autofocus IC 12 further includes the control circuit 3
5, a gain controller 36 and a sampling pulse generator 37 are included.

The preamplifiers 30a and 30b have an output terminal 9
The photocurrent signals from a and 9b are converted into voltage signals. The gain control circuits 31a and 31b amplify the voltage signals input to each with appropriate gains. The gain controller 36 determines the value of each gain for each channel. The sample hold circuits 32a and 32b are
At the timing when the sampling pulse is input from the sampling pulse generator 37, the gain control circuit 31
The voltage signals from a and 31b are sampled and held. The held voltage signal is transferred to the buffer amplifiers 33a and 33a.
After passing through b, the main amplifiers 34a and 34b are amplified under a constant gain.

The control circuit 35 has a serial-in-parallel-out shift register (8 bits), and this shift register has a serial data pulse "AFS".
The control data transmitted from the microcomputer 14 is written by "D". This control data is composed of gain data “GAIN” (5 bits), IRED selection data “IRED” (2 bits), ON-OFF data “SET” (1 bit), and the gain data is read by the gain controller 36. , Used to determine the gains of the gain control circuits 31a and 31b. Also, IRED selection data and ON-OFF
The data determines whether the IRED3 is turned on or off.

A control pulse "AFLCK" is further input from the microcomputer 14 to the control circuit 35. The control pulse is used to latch the control data and determine the light emission timing of the IRED 3, and also to the sampling pulse generator 37. Sample hold circuit 3
It is also used to determine the data latch timing by 2a and 32b.

The microcomputer 14 has a CPU 4
0, serial port 41, A / D converter 15,
It comprises a ROM 42 storing a main distance measuring program for executing the distance measuring sequence and a RAM 43 temporarily storing data and various flags obtained in executing the distance measuring sequence. The output port of the serial port 41 is switched by a command from the CPU 40, and the serial data pulse “AFSD” or the control pulse “AFL” described above is selected.
CK ”is input to the control circuit 35. The AD converter 15 converts the analog signal voltage sent from the main amplifiers 34a and 34b of the autofocus IC 12 into an 8-bit digital value (representing 0 to 255 in decimal) corresponding to its output level.

FIG. 3 shows a circuit used in the control circuit 35.
The bit serial in-parallel out shift register 45 is conceptually shown. The gain data “GAIN” and D5 to D described above are stored in the 5 bits D0 to D4.
2 bits of 6 have IRED selection data "IRED", D
ON-OFF data “SET” is assigned to each 1 bit of 7.

The 5-bit gain data of D0 to D4 is
The values from the “0” level to the “31” level can represent different gains. Further, the selection data of IRED of D5 to D6 is, for example, three IRs in order to project the distance measuring light at a plurality of places on the photographing screen to measure the distance at a plurality of places.
This is for determining which IRED emits light when using an ED. In the present embodiment, one IRED is used.
Since the distance measurement is performed only by the ED3, this 2-bit data is originally unnecessary. However, in the following description, when "01" is set as the selection data "IRED", the IR
It is assumed that ED3 is selected.

The basic distance measuring process of the distance measuring apparatus of the present invention will be described below with reference to the flow chart. When the shutter button of the camera is half-pressed, the main distance measuring program stored in the ROM 42 is started as shown in FIG. 4, and it is first determined whether or not the adjustment mode is set. The adjustment mode is performed by the microcomputer 1 so that the distance measuring device operates properly after the assembly of the camera is completed.
In this mode, input data from the terminal 28 connected to the connection terminal 14a of No. 4 is written in the EEPROM 29, which is not used by general users.

When used by a user in a normal state, distance measurement processing is executed. First, the distance measurement process is performed by the EEPROM 29.
The adjustment data written in is stored in a predetermined area of the RAM 43, and then the operation is started. Subsequently, as shown in FIG. 5, offset value detection processing, gain determination processing, measured distance processing, and reciprocal calculation processing of the object distance are executed. The offset value detection process is performed for the purpose of detecting how much signal noise is output from the output terminals 9a and 9b without turning on the IRED 3, and during actual distance measurement (actual distance measurement).
It is used when correcting the data obtained in. In addition,
In order to accurately detect the offset value, the output terminals 9a,
Data is captured from 9b a plurality of times (for example, 32 times), and the average value of these values becomes the offset value.

The gain determination processing is for setting the gain of the amplifier system to an appropriate value when performing the actually measured distance, and when the object distance is long and the output level of the photoelectric signal from the PSD 9 becomes small, a large gain value is obtained. Is set. In the measured distance processing, the IRED3 is set to 12 in 0.5 seconds, for example.
The light is turned on repeatedly eight times, and the data obtained from the AD converter 15 is added each time. Then, the distance measurement data is obtained by averaging the added data. The reciprocal of the object distance is calculated based on the distance measurement data thus obtained, and the set position of the taking lens 5 is determined based on the calculation processing.

FIG. 6 is a flowchart showing the offset value detection processing. During the offset detection process, the gain data “GAIN”, the IRED selection data “IRED”, and the ON-OFF data “SET” are set in the shift register 45. The gain data at this time is the minimum value “GAINMIN” individually determined for each camera. For example, when “GAINMIN = 8”, the shift register 45 stores “01000000” (2
The base number is set. As a result, "GAIN = 8",
Each control data of “IRED = 00” and “SET = 0” is set.

The setting of the control data is latched at the time of P1 shown in the timing chart of FIG. 7, that is, when the control pulse AFLCK becomes low level after the control data is transmitted. Further, after the control data is transmitted, a "COUNT = 3" is stored in a predetermined register in the CPU 24.
2 ”is set.

Among the control data set in the shift register 45, the data of "GAIN = 8" is gain control circuit 31a, 31 through the gain controller 36.
b to the gain control circuits 31a and 31b.
Are set to "8". Although the maximum gain “GAINMAX” is basically “31” and the minimum gain “GAINMIN” is “0”, these values correspond to PSD9 and later amplifier systems. Individual values are set for each camera, and E
It is stored in the RAM 43 from the EPROM 29.

After transmitting the control data, the photoelectric signals from the first and second channels are converted into digital data ADDATA by the AD converter 15 and read by the microcomputer 14 for each channel. When this reading process is performed, the control pulse "AFLCK" is first set to the low level as shown in the flowchart of FIG. After that, the serial data pulse “AFSD” becomes low level, and at the time of actually measured distance, the IRED3 is turned on at the timing P2 when it becomes next high level. Note that the IRED 3 remains unlit when the offset value is detected.

When ΔT1 has elapsed from the timing P2, the serial data pulse "AFSD" becomes high level again. At this timing P3, the sampling pulse generator 3
A sampling pulse is sent from 7 to the sample hold circuits 32a and 32b, and the gain control circuit 31
The photoelectric signals from a and 31b are held at the peaks of their waveforms. The value of the deviation ΔT1 from the timing P2 when the IRED3 is turned on until the photoelectric signal of each channel reaches a peak is usually different for each camera, corresponding to the amplifier system after PSD9. Therefore, an appropriate value for this ΔT1 is determined for each camera and is written in the EEPROM 29 as “SHTIME”.

The serial data pulse "AFSD" becomes low level after a lapse of a predetermined time ΔT2 from the timing P2, and is used as a timing signal for stopping the light emission of the IRED3 during the actual measurement distance. The photoelectric signal sampled and held at the timing P3 is then sequentially A
AD conversion is performed by the D converter 15. The digital data ADDATA after AD conversion is read by the CPU 40 as distance measurement data AFD1 and AFD2 for each channel.

At this time, one distance measurement data AFD2 is read as it is as the input digital value, but the other distance measurement data AFD1 is corrected by the correction coefficient "GPARA".
Is multiplied. This makes it possible to correct the error between the channels while keeping the gains of the gain control circuits 31a and 31b of the respective channels the same. Therefore, the gain control circuits 31a, 3a
The disadvantage of individually setting the gain of 1b can be avoided.

After the distance measurement data AFD1 and AFD2 are read in this way, the serial data pulse "AFSD",
Each of the control pulses “AFLCK” becomes high level,
After the control pulse “AFLCK” goes high, Δ
When T3 has elapsed, one cycle of distance measurement data reading processing is completed.

By repeating the above process, 32 pieces of distance measurement data AFD1 and AFD2 are obtained for each channel. These are added for each channel and divided by the number of reading times "32". As a result, the offset values OFS1 and OFS2 for each channel are obtained. The circuit constants of the amplifier system of each channel are set so that the value of the digital data ADDATA output from the AD converter 15 falls within a certain range when the offset value detection processing is performed. Therefore, the value of the digital data ADDATA output from the AD converter 15 during the offset value detection process does not become zero or minus.

As will be described later in gain determination processing, during the above-described offset value detection processing, the values are monitored when reading the distance measurement data AFD1 and AFD2, and the values are too small or too large. In this case, the over counter is incremented by one, for example 32
The offset value detection process may be performed again when the overcount value becomes “4” during the reading. When the overcount value is "3" or less, the average value may be calculated excluding the distance measurement data at that time.

After the above offset value detection processing, FIG.
And the gain determination process shown in FIG. 10 is performed. In the gain determination process, first, the EEPROM 29 is set as the initial gain.
Is set to "GAINMIN" expanded in the RAM 43. Then, "SUBCNT" on the RAM 43
The data "1" is set in the area, and step ST is set in the RAM 43 or an appropriate register in the CPU 40.
Each data indicated by 1 is set. The data listed in ST1 has the following contents.

OVCNT: Permissible number of readings when the data read for each channel is too small or too large AFADD: Value obtained by adding the data obtained for each channel and subtracting the offset value ADSUM1: Data of the first channel ADSUM2: Addition value of the second channel data PRECNT: Number of times data is read with the same gain UND flag: Flag set when the read data is too small OV flag: Flag that is set when the read data is too large CNT: Data read count

After the initial setting of ST1, gain data "GAINMIN", IRED selection data "01", O
It is transmitted to the shift register 45 in the control circuit 35 together with the N-OFF data “1”. Then, as shown in FIGS. 7 and 8, reading of data is started for each channel.

It is determined in steps ST2 and ST3 whether or not the values of the distance measurement data AFD1 and AFD2 read for each channel belong to the standard range. These distance measurement data are represented by 8-bit digital values,
It has a size of "0" to "255", and it is checked whether these values are smaller than the reference minimum value "5" or larger than the reference maximum value "230". This check is to confirm whether or not the gain set in the gain control circuits 31a and 31b is "GAINMIN". If it is determined to be appropriate, the distance measurement data AFD1,
AFD2 is added value ADSUM1, ADSUM, respectively.
2 is stored in the RAM 43.

When it is confirmed that the number of data reading "CNT" has become "0", the value "1" of "SUBCUT" is written as "PRECNT", and the processing shifts to the processing of FIG. In the initial setting, “CNT =
Since "1", "CNT ≠" in step ST4.
When it is "0", it means that there is an error, and therefore the data reading process is performed again.

In ST2, the distance measurement data AFD1, A
When it is determined that any value of FD2 is too small, the "UND flag" is set. Then, as in the case where it is determined in ST3 that either one of the distance measurement data AFD1 or AFD2 is too large, “OVCNT” to “−
1 ”processing is performed. In the initial setting, "OVCNT
Since "1" is set, "OVCNT = 0" is normally set by this processing, and after the "OV flag" is set, the processing shifts to the processing of FIG. 10. However, when "OVCNT ≠ 0", an error occurs. Then, the data reading process is performed again.

In the process of FIG. 10, first, in step ST5, the presence or absence of the "OV flag" is checked. "OV
In the case of "no flag", "ADSUM1", "ADS"
The value of "UM2" is divided by "SUBCNT", and the result is new distance measurement data "AFD1", "AFD2".
Is saved as. At step ST6, as shown in the figure, "(AFD1 + AFD2)-(OFS1 + OFS2)
≧ 136 ”is determined. "OFS1", "OFS
The value "2" has already been obtained in the above-described offset value detection processing.

At ST6, whether the sum of the distance measurement data "AFD1" and "AFD2" obtained from the first and second channels is sufficiently large even after the offset value is subtracted. Have confirmed. As will be described later, the distance measurement data "AFD1" and "AFD2" are used in the subsequent distance calculation, but it is preferable that the sum of these is "136" or more in order not to deteriorate the calculation accuracy. .

At ST6, the distance measurement data "AFD1",
When it is confirmed that the magnitude of the sum of "AFD2" is at an appropriate level for executing the distance measurement calculation, the gains of the gain control circuits 31a and 31b are "GAIN" at that time.
Value (initial value "GAINMIN"), and the process shifts to the actual distance measurement process shown in FIG.

At ST6, the distance measurement data "AFD1",
If it is confirmed that the magnitude of the sum of "AFD2" is inappropriate, the value of "GAIN" is changed on condition that the "GSNG flag" described later is not set.
The value of "GAIN" is "(AFD1 + AFD2)-(O
FS1 + OFS2) ”and is determined according to the gain table in the following table.

[0046]

[Table 1]

This GAIN addition value is used as the "GA
The value added to "IN" becomes a new "GAIN", but if this value exceeds "GAINMAX" in step ST7, the processing shifts to the processing in FIG. "GAIN
When it is less than or equal to "MAX", the new "GAIN" is transmitted to the shift register 45 as control data. Furthermore, in step ST8, the new value of "GAIN" is changed to "G
AINMAX-16 ", that is, it is determined whether the gain is larger than approximately the intermediate value of the gain. If smaller, the process returns to FIG. 9 and the gain determination process is performed again.

On the other hand, if the new value of "GAIN" is larger than almost the intermediate value of the gain, "SUBCNT ←
8 ”and then returning to FIG. 9 to determine the gain. The reason for increasing the number of data readings when the new gain value becomes larger than the intermediate value is that the noise component increases as the gain increases.

If it is determined in ST5 that "OV flag is present" and that "GAIN = GAINMIN" is confirmed in step ST9, EEP is performed for each camera.
The maximum gain value "GAINM" written in the ROM 29
This means that the gain setting process based on “AX” and the minimum value “GAINMIN” cannot be executed due to noise or disturbance. Then, in this case, the processing shifts to the processing in FIG.

Further, at ST9, "GAIN ≠ GAIN
When it is confirmed that it is "MIN", the "GSNG flag" is set. This "GSNG flag" is set when the set gain is improper. After the "GSNG flag" is set, "GA
A new gain is set as "IN ← GAIN-1",
The gain determination process of FIG. 9 is restarted under the gain.

While performing the above gain determination processing, ST6
When the process shifts to the process shown in FIG. 11, the actual distance measurement process is started using "GAIN" at that time. In this actual distance measurement process, the IRED3 is repeatedly turned on 128 times, and the distance measurement data AFD1 and AFD2 are read each time. Then, as in the case of the gain determination processing, it is confirmed whether or not these values are within the appropriate range. If the values are in an appropriate range, these distance measurement data AFD1,
AFD2 is further added to "ADSUM1" and "ADSUM2", which have been stored since the gain determination processing, respectively.

When the number of readings of the distance measurement data "CNT" becomes "0", the distance measurement calculation process shown in FIG. 12 is started. At this time, the number of readings of distance measurement data "CNT"
Indicates, as shown in the process of step ST10, “CNT
<-SUBCNT-PRECNT ”. In the measured distance, basically "SUBCNT = 128"
As described above, the distance measurement data is read 128 times, but the number of readings during the actual distance measurement process is reduced by the number of “PRECNT” due to the above subtraction.
However, when the number of times the data is read in the gain determination process is included, the number of times is “128”.

"PRECNT" is the number of times the distance measurement data is read in the gain determination process that has already been performed prior to the actual distance measurement, as shown in FIG. Therefore,
When the distance measurement data is read eight times in the gain determination process, the number of times the distance measurement data is read at the time of actually measuring the distance is 120.

Distance measurement data AFD1, AF at the time of actual distance measurement processing
When the value of D2 is too small, the "UND flag" is set as in the gain determination process. Then, including the case where it is too large, "OVCNT" is subtracted by "1". Since the value of "OVCNT" is set to "16" by the initial setting of ST10, the ranging data AFD is read while reading the ranging data "CNT" times.
Even if any one of 1 and AFD2 is an inappropriate value, it is allowed up to "15" times, and the actual distance measurement process is continued.

When the reading of the distance measurement data "CNT" times is completed, as shown in FIG. 12, the calculation for obtaining the reciprocal of the object distance is performed. First, "ADSUM1", "A
Offset values “OFS1” and “O” for DSUM2 ”
The correction is performed by "FS2", but since the total number of data readings from the gain determination process is 128 times,
The value obtained by multiplying each offset value by 128 is "ADSUM
1 "and" ADSUM2 ".

Then, "ADSUM1", "ADSUM"
2 ”addition data“ AFADD ”and subtraction data“ AFD
“IF” is calculated, and the ratio “AFRATIO” is calculated. Next, the reciprocal of the subject distance "INV.LEN" is calculated. In this calculation, the EEPROM 29
The coefficient “ADJ0” stored in RAM 43 from RAM is “A
DJ1 ”is read. These coefficients are values appropriately set according to the optical characteristics of each camera. Then, the reciprocal of the object distance thus obtained, "INV.
“LEN” is input to the CPU 40, and the focus position of the taking lens 5 is determined based on this. In addition,
“Α” is a constant value that does not depend on the individual difference of the camera.

In the process of executing the gain determination processing of FIG. 9 and the actual distance measurement processing shown in FIGS.
If the distance measurement data AFD1 and AFD2 are too large even though "AIN = GAINMIN", it means that there is a high-intensity light incident on the PSD 9 and the object distance is a close distance. There is. Therefore,
As shown in Fig. 12, "∞" is set as the value of "INV.LEN", whereby the focus position of the taking lens 5 is adjusted to the closest distance, and a short distance warning is issued.

During execution of the gain determination process, "AFD1
The value of “+ AFD2” has not reached an appropriate level, and the value of “GAIN” that was newly set in ST7 is the maximum gain value “GAIN” set for each camera.
When it exceeds MAX, it means that the light incident on the PSD 9 is extremely weak. In this case, it means that the subject distance is extremely far, so "0" is set as the value of "INV.LEN",
Thereby, the focus position of the photographing lens 5 can be adjusted to the position for infinity photographing.

The characteristic feature of the distance measuring device is that the EEPROM 29 is provided for each of the offset value detecting process, the gain determining process, the actually measuring distance process, and the reciprocal calculation process of the object distance.
From the data stored in the RAM 43, that is, the maximum value “GAINMAX” and the minimum value “GAINMI” of the gain.
N ”,“ SHTIME ”that determines the timing of sampling and holding the photoelectric signal from the PSD 9, a coefficient“ GPARA ”that corrects the deviation between the first and second channels, and a coefficient“ ADJ0 ”that is used when calculating the reciprocal of the subject distance. "
And “ADJ1” are used appropriately.

These adjustment data are IRED3, PS
D9, an appropriate value is determined for each camera in accordance with the electrical characteristics of the amplifier system of the first and second channels. Therefore, the adjustment mode shown in FIG. 4 can be executed. When the camera is assembled, the adjustment terminal 28 is connected to the connection terminal 14a of the microcomputer 14. Then, the standard subject is arranged at a constant subject distance position, and standard values are input as the above-mentioned adjustment data by operating the keyboard of the terminal device 28. The adjustment data input from the terminal 28 is temporarily stored in the RAM 43.

After that, test distance measurement is performed. The test distance measurement may be exactly the same as the distance measurement processing described above,
Appropriate data such as "S
Data such as “UBCNT”, “OVCNT”, and “GAIN” may be input by the keyboard.

When the test distance measurement for the standard subject is started, the offset values "OFS1", "OFS2", the distance measurement data AFD1, AFD2, the addition data "ADSUM" are displayed.
1 ”,“ ADSUM2 ”, etc. are obtained, and these data are fed back to the terminal 28,
Stored in memory. Therefore, these data are evaluated to determine whether or not each of the adjustment data input as standard values is appropriate. As a result of the test distance measurement, if appropriate adjustment data needs to be corrected, this is adjusted and the test distance measurement is performed again.

In this way, the test distance measurement and the adjustment data correction are performed, and when it is confirmed that the test distance measurement is satisfactorily executed, the terminal device 28 is operated to write the respective adjustment data into the EEPROM 29. . This allows
Each adjustment data corrected to an appropriate value for each camera is written in the EEPROM 29.

As described above, if the adjustment data having individual differences for each camera is written in the EEPROM 29 and the distance measurement processing is performed by appropriately using these adjustment data, a potentiometer or the like in the autofocus IC 12 can be used. It is possible to perform good distance measurement with a small error without providing an adjustment element and adjusting the adjustment element to adjust the amplifier system. Also, for example, IRED3 or P
When the distance measuring accuracy is deteriorated due to the change of SD9 with time, etc., the microcomputer 14 is used for the inspection and repair.
By connecting the terminal device 28 to the connection terminal 14a and performing the same work as above, the ranging accuracy can be easily restored.

Although the present invention has been described above with reference to the illustrated embodiment, the distance measuring program can be partially improved or modified, and gain determination processing and repeated reading of distance measuring data during actual distance measurement are possible. The number of times and the like can be set appropriately. Also, instead of finally calculating the reciprocal of the subject distance, “AFR
The focus position of the taking lens 5 may be obtained from the value of "ATIO". In addition, the present invention uses one IR
Not only the one that measures the distance with the ED3, for example, three IREDs with different light projection directions are used, and the distance measurement light is projected to the center of the photographic screen and the three places on the left and right of the IRED to measure the distance. It can also be used for the ones.

[0066]

As described above, in the distance measuring device of the present invention, the main program memo storing the distance measuring program is stored.
In addition to this, a sub memory is provided, and different adjustment data for each camera is written in this sub memory , and this adjustment data is used as a pair of output terminals of the PSD by using the use data when executing the distance measurement program. Since the amplifier systems connected to each other operate in an equivalent manner, the work of adjusting the electrical characteristics of each channel is unnecessary, and a low-cost and accurate camera ranging device can be realized. .

In order to improve the distance measurement accuracy, a gain control circuit that amplifies the photoelectric signal of each channel to an appropriate output level is used, but the maximum value and the minimum value are different for each camera. Therefore, it is effective to set the maximum value and the minimum value for each camera and store them in the sub-memory, and to perform gain control based on these values. If you cannot set the appropriate gain between the minimum value and the minimum value, set the focus position of the shooting lens to the hyperfocal position or display a warning to avoid meaningless repetition of distance measurement. It is possible to deal with quick shooting.

Furthermore, it is of course possible to write coefficient data for adjusting the gain difference between the channels and data for determining the sample and hold timing of the photoelectric signal in the sub memory, which allows adjustment. Efficient manufacturing is possible by omitting the work of assembling circuit elements and adjusting them.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an autofocus IC and a microcomputer.

FIG. 2 is a schematic diagram of a camera using the present invention.

FIG. 3 is a conceptual diagram of a shift register for storing control data.

FIG. 4 is a flowchart showing a process of an adjustment mode when a terminal is connected.

FIG. 5 is a flowchart showing basic processing of a distance measuring program.

FIG. 6 is a flowchart showing offset value detection processing.

FIG. 7 is a timing chart showing how control data is transmitted and ranging data is read.

FIG. 8 is a flowchart showing distance measurement data reading processing.

FIG. 9 is a flowchart showing a part of gain determination processing.

FIG. 10 is a flowchart showing another part of the gain determination processing.

FIG. 11 is a flowchart showing a measured distance process.

FIG. 12 is a flowchart showing a reciprocal calculation process of a subject distance.

[Explanation of symbols]

2 Projector 3 IRED 5 shooting lens 9 PSD 12 Autofocus IC 14 Microcomputer 14a connection terminal 28 terminals 29 EEPROM 31a, 31b Gain control circuit 32a, 32b sample and hold circuit 42 ROM 43 RAM

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01C 3/06 G01B 11/00 G02B 7/32 G03B 13/36

Claims (5)

(57) [Claims] 1. The distance measuring light projected from a light projecting unit and reflected by a subject is made incident on a light receiving element, and is output for each channel from a pair of output terminals of the light receiving element corresponding to the incident position. In the range finding device for a camera, which adjusts the photoelectric signal to a predetermined output level by a gain control circuit capable of gain adjustment, and calculates the focusing position of the photographing lens based on each photoelectric signal after the level adjustment, the photoelectric signal A main program memory storing a distance measuring program for calculating the focusing position of the photographing lens based on the above, and used for adjusting the gain of the gain control circuit by executing the distance measuring program, and set for each camera. and a sub-memory storing the gain maximum value and the minimum value of the gain control circuit, the Sabumemo Is, electrically erasable E
A distance measuring device for a camera , characterized by comprising an EPROM . 2. A light is projected from a light projecting portion and reflected by a subject.
The distance measuring light that has come
Corresponding to each channel from the pair of output terminals of the light receiving element.
The gain control that can adjust the gain of the photoelectric signal output to
Adjust the output level to the desired level using the trawl circuit, and
Pin of the shooting lens based on each photoelectric signal after adjustment
In a camera distance measuring device for calculating a focusing position, a focusing position of a photographing lens is calculated based on the photoelectric signal.
A main program that stores a ranging program for calculating
Gram memory and the execution of the distance measurement program
Used when adjusting the gain of the gain control circuit.
Gain control times set individually for each camera.
A sub-memory that stores the maximum and minimum values of the road gain
When the gain value adjusted by the gain control circuit is equal to or larger than a predetermined value determined corresponding to the maximum value of the gain stored in the sub memory, the light is received under the gain. features and to Luke camera distance measuring device that photoelectric signal was read out a plurality of times from the device. 3. When adjusting the photoelectric signal from the light receiving element to the predetermined output level, when the gain of the gain control circuit is not included between the maximum value and the minimum value stored in the sub memory, The distance measuring device for a camera according to claim 1 or 2, wherein a signal for setting the photographing lens at a hyperfocal position or a warning signal is output. 4. Distance measuring light projected from a light projecting unit and reflected by a subject is made incident on a light receiving element, and is output for each channel from a pair of output terminals of the light receiving element corresponding to the incident position. In the range finding device for a camera, which adjusts the photoelectric signal to a predetermined output level by a gain control circuit capable of gain adjustment, and calculates the focusing position of the photographing lens based on each photoelectric signal after the level adjustment, the photoelectric signal A main program memory storing a distance measuring program for calculating the focusing position of the photographing lens based on the above, and used for reading a photoelectric signal from each channel of the light receiving element by executing the distance measuring program. And a sub-memory storing a correction coefficient set for each camera corresponding to a gain difference between channels. For a camera characterized by correcting digital data obtained from one channel by a correction coefficient written in the sub-memory when the photoelectric signals of each channel amplified by the troll circuit are digitally converted and read. Ranging device. 5. Distance measuring light projected from a light projecting unit and reflected by a subject is made incident on a light receiving element, and is output for each channel from a pair of output terminals of the light receiving element corresponding to the incident position. In the range finding device for a camera, which adjusts the photoelectric signal to a predetermined output level by a gain control circuit capable of gain adjustment, and calculates the focusing position of the photographing lens based on each photoelectric signal after the level adjustment, the photoelectric signal A main program memory for storing a distance measuring program for calculating the focusing position of the photographing lens based on the above, and a photoelectric signal used when reading a photoelectric signal from each channel of the light receiving element by executing the distance measuring program. Stores timing data set for each camera to determine the sampling timing of each channel Camera distance measuring apparatus characterized by having a sub-memory has.