JP2779451B2 - Auto focus camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus (hereinafter abbreviated as “AF”) camera, and more specifically, to a plurality of known distance measurement objects during an AF adjustment process. The distance measurement data for point adjustment is stored in the storage means, and the output characteristics of the distance measurement distance vs. AF distance measurement output are calculated from the adjustment distance measurement data, and the AF in actual use is calculated.
The present invention relates to an autofocus camera that corrects distance measurement data.

[Conventional technology]

2. Description of the Related Art Conventionally, for adjustment of, for example, a subject brightness level and AF ranging data level in an electric circuit of a camera, a semi-fixed resistor is mainly used to adjust an analog amount.

FIG. 5 is a circuit diagram of a conventional "ranging operation circuit" disclosed in Japanese Utility Model Application Laid-Open No. 63-67913 (hereinafter referred to as "first conventional example"), and uses one variable resistor. Thus, an example of adjusting the level shift is shown.

In the Figure 5, a series circuit of a cell D ₁ constituting the light receiving cell and the resistor r _1, to connect the series circuit of the cell D ₂ and the variable resistor r _2, respectively between the power supply and the ground, the cell D ₁ a connection point between the resistor r _1, the potential V ₁ of the connection point of the cell D ₂ and the variable resistor r ₂
The V ₂ via respective capacitors C _1, C ₂ and to one input terminal of the amplifier A _1, A _2, and the other input terminal of the amplifier A _1, A ₂ to the ground potential, the amplifier A _1, A ₂ after amplifying respectively the potentials V _1, V _2, the amplifier a _1, a each output a ₁ V ₁ of _2, a output ₂ V ₂ from the differential amplifier a ₃ in addition to the differential amplifier a ₃ a ₂ V so as to obtain the ₂ / a ₁ V _1.

In this case, the light emission profile is made to fluctuate over almost the entire light receiving element surface of the light receiving cell, and the resistance r ₁ and the variable resistance r ₂
Is such that r ₂ <r ₁ and the waveform of the voltage ratio is used to eliminate the infinity determination circuit.

In the case of the first conventional example, the measured distance-to-voltage ratio V ₂ / V ₁
The adjustment of the level shift in the relation of the ratio I ₂ / I ₁ of the cell currents I ₁ and I ₂ is performed by adjusting the variable resistor r ₂ .

FIG. 6 is a circuit diagram of a second conventional example for adjusting the output of distance measurement data in an AF camera. In the case of FIG. 6, pulse light reflected from a distance measurement object (not shown) is received by a light receiving lens. (Also not shown) via PSD (Position Se
nsitive device) 101, and the reflected pulse light is imaged corresponding to the position of the distance measurement target. This PSD101,
The incident position of the light spot can be known from the ratio of the two current outputs output from both ends, and distance information of the distance measurement target can be obtained from the two current outputs. These two current outputs are input to the inverting input terminals of the amplifiers 102 and 103, respectively. The non-inverting input terminals of the amplifiers 102 and 103 are at the ground potential.
The feedback resistors R ₁ and R ₂ are connected between each output terminal and the inverting input terminal.The current output output from the PSD 101 in these amplifiers 102 and 103 takes a difference from the ground potential to obtain a resistance R ₃ , R ₄
To the inverting input terminal and the non-inverting input terminal of the amplifier 104.

The non-inverting input terminal of this amplifier is grounded via a variable resistor 105 for level shift adjustment.
A variable resistor for gain adjustment is connected between the output
106 is connected.

The amplifier 104 takes the deviation of the outputs of the amplifiers 102 and 103 to amplify and output the distance measurement data.
In this case, the gain of the amplifier 104 is adjusted by the variable resistor 106, and the output level of the amplifier 104 is shifted by the variable resistor 105.
Adjustment is performed.

FIG. 7 is a diagram of Japanese Unexamined Patent Publication No.
FIG. 11 is a block diagram illustrating only a main part of the block diagram of the camera illustrated in “third conventional example”.

In FIG. 7, analog information corresponding to the luminance of a subject which has been preliminarily measured by the photometric circuit 107 under two luminances is digitally converted by analog / digital (hereinafter, referred to as "A / D") conversion means 108a in the microcomputer 108. The signal is converted into a signal, and correction data based on an error corresponding to the reference characteristic of the output characteristic of the A / D converter 108a is stored in the storage means 109, and A / D conversion is performed based on the correction data stored in the storage means 109. The photometric information converted into a digital signal by the D converter 108a is corrected by the correction means in the microcomputer 108.

In this correction, assuming that the photometric output output from the A / D converter 108a is BVo and the correction value by the linear function is BVo ', the correction is based on the linear function of BVo' = m.BVo + n (1) It is shown that a luminance value [BVo '] is obtained.

The third conventional example will be described more specifically. Photometric circuit
The photometric output of two luminances by 107 is BVo ₁ , BVo ₂ ,
The following equations (a) and (b) are established with the correction values by the linear function as BVo ₁ ′ and BVo ₂ ′, respectively.

BVo ₁ ′ = m · BVo ₁ + n (a) BVo ₂ ′ = m · BVo ₂ + n (b) By solving the simultaneous equations of the equations (a) and (b), the correction data m, n is obtained, the correction data m and n are stored in the storage means 109 in advance, and the photometric output BVo at the time of photometry is corrected by the correction data m and n as in the above equation (1).

This operation will be described with reference to the flowchart of FIG. When the power supply (not shown) of the camera is turned on, the correction data m and n stored in the storage means 109 are read into the microcomputer 108 by “read m and n from the E ² PROM into the CPU” in the flowchart, and the flowchart is executed. "AF
If the AF switch (not shown) is off at "SW ON?", The process goes to the NO side in the flowchart, returns to "AF SW ON?" In the flowchart again, and repeats the ON / OFF determination of the AF switch.

If the AF switch is on, the process proceeds to the processing step of “AF ranging, ranging data Vfx” in the flowchart, the ranging of the subject is performed by the focus detection circuit 110, the ranging data is output to the microcomputer 108, and the After digital conversion is performed by the A / D conversion means 108a in the computer 108, distance measurement data Vfx is obtained. This distance measurement data Vfx is corrected to Vf '= mVf + n (c) by the correction data m and n previously read at "Vf' = mVf + n ← Vfx" in the flowchart, and is corrected to "Vfx '= mVfx + n" in the flowchart. ,
The distance measurement data Vfx ′ of the AF to be measured is obtained as Vfx ′ = mVfx + n (d), and “1 / L = f (Vf ′) ← Vf” in the flowchart.
x ′ ”, the subject distance 1 / Lx is obtained from the distance measurement data Vfx ′ as 1 / Lx = f (Vf ′) (E), and“ 1 / Lx = f (Vfx ′) in the flowchart is obtained. ) "
Then, the subject distance 1 / Lx to be measured is obtained as 1 / Lx = f (Vfx ′) (f), and the processing step “x = g” in the flowchart is performed.
Go to (1 / L) ← 1 / Lx.

In this processing step, the extension amount x of the lens corresponding to the subject distance 1 / Lx obtained by the above equation (f) is obtained as x = g (1 / L) (g), and “Xx = g (1 /
Lx) ", the amount Xx of the predetermined lens extended is obtained as Xx = g (1 / Lx) (h).

Next, the microcomputer 115 controls the lens driving circuit 114 by the microcomputer 108 to drive the motor 115 by the lens extension amount Xx obtained by the above equation (b) in the “lens extension” of the flowchart, and the lens is extended.

Further, FIG. 9 is a diagram of Japanese Unexamined Patent Publication No.
FIG. 10 is a circuit diagram of an “electrical adjustment circuit of a camera” disclosed in “Fourth Conventional Example”.

In the case of the fourth conventional example, analog data of an exposure factor including subject brightness information is converted into a photocurrent by a light receiving element 121, and logarithmically compressed by a photometric circuit including an operational amplifier 122 and a compression diode 123 to a voltage value. It is converted and temperature compensated by temperature compensation diode 124 and constant current source 128.
The digital data A / D converted by the A / D converter 130 via the multiplexer 129 is input to the arithmetic unit 131.

Further, the aperture information voltage is generated by the aperture information input resistor 126 by the multiplexer 129 and input as a digital value to the arithmetic unit 131 via the A / D conversion means 130, and the film sensitivity information voltage is input to the film sensitivity information voltage resistor. The arithmetic unit 131 is generated by the A / D conversion means 130 and passed through the A / D conversion means 130.
Is input as a digital value.

The arithmetic unit 131 obtains the input object luminance information B
Based on the v value (apex notation), aperture information Av value (apex notation), and film sensitivity information Sv value (apex notation), the shutter speed information Tv value (apex notation) is calculated as follows: Tv = Sv + Bv−Av (2) The arithmetic unit 131 calculates a shutter speed and an aperture value for obtaining an appropriate exposure by using an arithmetic expression.

The data output from the A / D conversion means 130 input to the arithmetic unit 131 are the transmittance of the optical system, the efficiency of the light receiving element 121, the current value of the constant current source 128, and the respective resistance values for setting the film sensitivity aperture. An error occurs due to variations in

To correct this error, the nonvolatile memory element 132
(Hereinafter referred to as "memory"), a jumper 133 and a data line 134, and the jumper 133
2 to store correction data to obtain the required accuracy for normal operation, such as exposure control accuracy and exposure instruction accuracy.
132 and the value based on the correction data
It is configured to be introduced from 31 into an exposure control circuit and an exposure display circuit (neither is shown).

[Problems to be solved by the invention]

In the case of the first conventional example shown in FIG. 5, the variable resistor r ₂
However, since the gain adjustment is not performed, there is a problem that good distance measurement accuracy cannot be obtained.

In the case of the second conventional example shown in FIG. 6, as an adjustment method, shift adjustment is performed by the variable resistor 105, and then gain adjustment is performed by the variable resistor 106, but the shift is changed by the gain adjustment. It is necessary to confirm the shift again, and if there is a harmful shift deviation after the gain adjustment, there is a drawback that the workability is poor such that the shift adjustment is required again.

Further, in the case of the third conventional example shown in FIG.
As shown in the diagram of the subject luminance information BV vs. photometric output Vi characteristic diagram, at the time of photometry, correction is performed using a linear expression with correction data m and n stored in advance in the storage unit 109 for certain subject luminance information BVx. However, since the error is considered to be changed linearly, good correction can be performed because the error is considered to be close to the design value. However, in the case of a high-order curve data output that is actually output, The error cannot be absorbed, and the approximation accuracy decreases.

In addition, since the photometric data is first-order approximated, and the shutter speed information value (Tv) and the aperture information value (Av) are calculated based on the first-order approximation, the photometric data is processed twice. It gets complicated.

Further, in the case of the fourth conventional example shown in FIG. 9, similarly to the third conventional example, the correction is performed by using the correction data stored in advance in the photometry result, and therefore, the photometry data is transmitted twice. Processing must be performed to obtain the shutter speed information Tv value and the aperture information Av value, which complicates the calculation.

The present invention has been made in view of the above circumstances, and an object of the present invention is to be able to directly process an AF output without having a theoretical value, and furthermore, variations in light receiving element characteristics and errors due to an A / D converter. Can be absorbed simply by performing simple arithmetic processing, and the storage capacity of the software is small.
It is an object of the present invention to provide an autofocus camera that has a short distance measurement time, can greatly reduce the time required from AF distance measurement to the calculation of a lens extension amount, and can sufficiently cope with a fast-moving subject.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a light projecting means for projecting light to a distance measuring object, and a light projecting means arranged at a place where a reflected spot light of the light projected by the distance measuring object is imaged, Position detecting means for continuously detecting the position of the incident spot light according to the distance of the distance measuring object based on the parallax with the means in the direction of position change due to the change in the distance, and an analog output of the position detecting means as a digital signal An analog / digital converter for converting the data into three or more distances to be measured at three or more points at a known distance during the auto focus adjustment step. Based on storage means for storing distance data and three or more of the adjustment distance measurement data stored in the storage means, the intermediate of the adjustment distance measurement data is interpolated by first-order approximation. An output characteristic calculating means for calculating an output characteristic of the distance-to-autofocus distance measurement output; and a distance to be measured from the autofocus distance measurement data measured by the position detecting means in actual use and the output characteristic. A feeding amount calculating means for calculating a lens feeding amount from the distance.

Further, in order to achieve the above object, the present invention is characterized in that a writable E ² PROM is particularly used as the storage means.

Further, in order to achieve the above object, the present invention is arranged such that a light projecting means for projecting light to a distance measurement target and a reflection spot light of the light projected by the distance measurement target are imaged,
Position detecting means for continuously detecting the position of the incident spot light in accordance with the distance of the distance measuring object based on the parallax with the light projecting means in a position change direction due to a change in the distance, and an analog output of the position detecting means To a digital signal, and three or more analog / digital converters output from the analog / digital converter when three or more distance measuring objects having a known distance are measured in the auto focus adjustment step. A storage means for storing the adjustment distance measurement data, and a camera which firstly approximates the middle of the adjustment distance measurement data based on the three or more adjustment distance measurement data stored in the storage means. An autofocus output characteristic diagram is formed based on the obtained autofocus distance measurement output data, and the lens is extended according to the autofocus output characteristic diagram. Is obtained by said determining the amount.

(Operation)

In the autofocus camera configured as described above, the position of the incident spot light that is projected on the distance measurement target by the light projecting means and reflected by the distance measurement target and enters the position detection means is determined by the change in distance. The position change direction is continuously detected, and at the time of the auto focus adjustment step, the detection outputs of three or more distance measuring objects of known distances are used as adjustment distance measurement data by an analog / digital converter using digital values. After that, the data is stored in the storage unit by the arithmetic unit.

Further, the output characteristic calculation means reads out the three or more adjustment distance measurement data stored in the storage means, and interpolates the intermediate distance adjustment data by linear approximation to obtain the distance measurement distance versus the auto focus measurement data. The output characteristic of the distance output is obtained as a first-order approximation formula, and the distance of the object to be measured is obtained from the above-described output characteristics and the auto-focus distance measurement data obtained by detecting the position in actual use by the feeding amount calculation means. Calculate the lens extension amount.

Further, in the autofocus camera configured as described above, since the E ² PROM is used as the storage means, the adjustment distance measurement data can be easily written in the E ² PROM, and the adjustment work can be easily performed. It can be carried out.

〔Example〕

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a block diagram showing the overall configuration of an embodiment of an autofocus camera according to the present invention.

In FIG. 1, reference numeral 1 denotes a light projecting element such as a light emitting diode, which receives an output of the light projecting circuit 2, emits light, and projects the light to a distance measuring object (not shown).

The light emitting circuit 2 is controlled by an arithmetic unit 3 (hereinafter, referred to as a “CPU”) to cause the light emitting element 1 to emit light and stop the light emission.

Reference numeral 4 denotes a semiconductor position detecting element such as a PSD, and the semiconductor position detecting element 4 and the light receiving circuit 5 constitute "position detecting means".

The semiconductor position detecting element 4, which is one component of the position detecting means, will be described here using a PSD for convenience of explanation.

This PSD 4 has one-dimensional continuous position resolution, and reflected pulse light is imaged at a position corresponding to the distance of the distance measurement target. In the PSD 4, the ratio (difference) of the two current outputs changes according to the incident position of the light spot, and information on a distance measurement target can be obtained from the two current outputs.

These two outputs are sent to the light receiving circuit 5. Although the internal configuration of the light receiving circuit 5 is not shown in FIG. 1, the two current outputs of the PSD are added to a difference detection circuit based on a control signal of the CPU 3, and the difference is calculated there.
Is output as a distance detection signal corresponding to the current ratio of the first and second current outputs.

Since this distance detection signal corresponds to the distance to be measured (that is, the subject distance), the distance detection signal is used as adjustment distance measurement data in an AF adjustment process in a factory, and when the camera is actually used. Is used as AF distance measurement data at the time of AF distance measurement.

The output of the light receiving circuit 5 is input to an analog / digital (hereinafter, referred to as “A / D”) converter 6. The A / D converter 6 digitizes the analog output of the light receiving circuit 5 and outputs it to the CPU 3.

The CPU 3 uses the output of the A / D converter 6 during the AF adjustment process.
The data is stored in the storage means 7. The calculation function of the CPU 3 will be described later in detail.

In this embodiment, the storage means 7 uses an E ² PROM. In the AF adjustment step, at least the adjustment distance measurement data of a different known distance is stored. This adjustment distance measurement data is read.

The CPU 3 is used for AF ranging in actual use of the camera.
The distance measurement data for adjustment is read from the storage means 7 and, as shown in FIG. 2, two points (Vf ₁ , 1 / L) of the coordinates of the AF output (Vf) versus the distance measurement distance (1 / L) are used. ₂ ) and a straight line passing through (Vf ₂ , 1 / L ₂ ), , And by substituting the AF distance data after A / D conversion into equation (3),
Calculation for obtaining a certain distance measurement distance (subject distance) 1 / Lx is also performed.

Further, based on the distance measurement distance (1 / Lx), the lens extension amount (x) versus the lens extension amount shown in the distance measurement distance (1 / L) characteristic shown in FIG. 2 is calculated.

Further, the CPU 3 controls the lens driving circuit 8 so as to extend the lens by the calculated amount of extension of the lens.

The operation of this embodiment thus configured will be described with reference to the flowcharts of FIGS.

FIG. 3 is a flowchart showing an operation flow of an AF adjustment process, and FIG. 4 is a flowchart showing an operation flow at the time of AF distance measurement when the camera is actually used.

First, the AF adjustment step will be described with reference to the flowchart of FIG. It is assumed that five distance measurement points for adjustment from the camera to be measured are N = 1 to N = 5. The distance from the camera to each of these five adjustment ranging points is
It is assumed that it is known in advance.

Next, in the flowchart of FIG. 3, "N = 1"
Of the adjustment ranging points N = 1 to N = 5, the adjustment ranging point is set to N = 1, and a chart is set at, for example, the closest distance in “Adjustment chart distance setting” in the flowchart, and “AF” in the flowchart is set. The process moves to the "ranging" process.

In this AF distance measurement, the light emission circuit 2 is driven by the CPU 3,
The light projecting element 1 is caused to emit light by the output of the light projecting circuit 2, and the light is emitted to the adjustment point N = 1 of the distance measurement object generated from the light projection element 1, and the adjustment distance measurement point N = 1 of the distance measurement object is set. The incident spot light from is received by PSD4 and formed into an image.

Two current outputs corresponding to the incident position of the incident spot light at the adjustment distance measuring point N = 1 formed by the PSD 4 are input to the light receiving circuit 5, and the adjustment measurement corresponding to the current ratio of the two current outputs is performed. The adjustment distance measurement data for the distance point N = 1 is obtained. The distance measurement data output from the light receiving circuit 5 is input to the A / D converter 6 in the “A / D conversion” processing step of the flowchart.

The A / D converter 6 converts the adjustment distance measurement data at the adjustment distance measurement point N = 1 of the analog signal input from the light receiving circuit 5 into a digital signal.

Hereinafter, similarly, the A / D converter 6 A / D-converts the adjustment distance measurement data of the adjustment distance measurement points N = 2 to N = 5 obtained by setting up a chart at different distances. N =
5? ”, If N = 5, the flowchart is
The process exits to the NO side, and returns to the processing steps of “adjustment of chart distance for adjustment” in the flowchart.

Also, in “N = 5?” Of the flowchart, N = 5
If, the process proceeds to step "E ² data written to PROM" of the flow chart, CPU 3 is stored adjustment distance data Vf ₁ ~Vf ₅ of the adjusting distance measurement point N = 1 to N = 5 means 7 And the series of operations in the AF adjustment process is completed.

Next, the operation at the time of AF ranging when the camera is actually used will be described with reference to the flowchart of FIG.

The operation at the time of AF ranging when the camera is actually used at the time of "power on" in the flowchart of FIG. 4 will be described.

The power of the camera is turned on by "power on" in the flowchart of FIG.

Then, CPU to "Vf _1, Vf ₂ of the flow chart from the E ² PROM
The CPU 3 moves to the processing step of “read in”, and the CPU 3 sets the two adjustment distance measurement points N = 1 and N = 2 out of the adjustment distance measurement data Vf _{1 to} Vf ₅ stored in the storage means 7. Read the distance measurement data Vf ₁ and Vf ₂ for adjustment of the
f ₁ , 1 / L ₁ ) (Vf ₂ , 1 / L ₂ ) and a straight line 1 / L = f (Vf).

In this processing step, the CPU 3 determines two points (Vf ₁₎ of the coordinates of the AF output Vf versus the distance measurement distance 1 / L shown in FIG. 2 corresponding to the adjustment distance measurement data Vf ₁ and Vf ₂ read from the storage means 7. , 1 /
L ₁ ) (Vf ₂ , 1 / L ₂ ), that is, a straight line passing through the equation (3) is obtained.

Once this formula (3) is calculated by reading the distance measurement data for adjustment Vf ₁ , Vf ₂ once, it will be used until the battery is replaced in the camera.
It is not necessary to read again.

In this way, when the straight line of the above equation (3) is obtained, the CPU 3 determines whether or not an AF switch (not shown) is on in a processing step of “AF SW ON?” In the flowchart. , Until the AF switch turns on
Repeat this check. When the AF switch is turned on,
The processing shifts to the processing step of “AF ranging, ranging data Vfx” in the flowchart, and the CPU 3 drives the light emitting circuit 2 to cause the light emitting element 1 to emit light.

The spot light emitted by the light emitting element 1 and condensed by the light projecting lens is projected on a camera subject, and the incident spot light reflected from the subject is projected onto the PSD 4 in the same manner as in the AF adjustment step. An image is formed, and the position of the incident spot light is input to the light receiving circuit 5 as two photocurrent outputs.

The light receiving circuit 5 outputs AF ranging data Vfx corresponding to the current ratio of the two current outputs, sends it to the A / D converter 6, where it is digitized and output to the CPU 3.

The CPU 3 substitutes this AF distance measurement data Vfx into the above equation (3) in the processing step of “1 / L = f (Vf) ← Vfx” in the flowchart, and “1 / Lx = f (Vfx)” in the flowchart. AF in
First-order approximation ranging distance 1 / Lx corresponding to ranging data (Vfx)
Ask for.

With respect to the distance measurement distance (subject distance) 1 / L, the lens extension amount x is apparent from the left part of FIG.
Since it is uniquely determined, "x = g (1 /
In the processing step of “L) ← 1 / Lx”, the CPU 3 substitutes the distance measurement distance 1 / Lx into x = g (1 / L) and obtains “Xx = g” in the flowchart.
(1 / Lx) ", the lens extension amount Xx with respect to the distance measurement distance 1 / Lx is calculated.

At the same time as calculating this lens extension amount Xx, the CPU 3
Controls the lens drive circuit 8 to extend the lens by the lens extension amount Xx calculated in the processing step of “lens extension” in the flowchart of the photographing lens (not shown), and focuses the object for distance measurement.

In the AF ranging when the camera is actually used, if the adjusting ranging points are N = n, (n-1) formulas (3) are created.

As described above, according to this embodiment, in the AF adjustment process, the distance measuring data for the five adjusting distance measuring points is measured by the position detecting means, A / D converted, and then stored in the storage means 7 by the CPU 3. When performing AF ranging when the camera is actually in use, read out the distance measurement data for adjustment from the storage means, and calculate the formula of a straight line passing through the coordinates of AF output vs. distance measurement distance from the adjustment distance measurement data. Is calculated by the CPU 3, and between each ranging point, interpolation is performed by first-order approximation to obtain an AF output characteristic composed of a first-order approximation formula, which is then detected by the position detection means to perform A / D conversion. The measured distance (subject distance) is obtained by substituting the obtained AF distance measurement data into this first approximation formula, so that the AF output is always corrected by the theoretical value and the correction data as in the third conventional example. Because it does not have a theoretical value compared to when In addition, the configuration time of software can be shortened.

Also, as in the third prior art AE SPD, the output is almost one.
It is possible to adjust not only the linear characteristic but also the higher-order curvilinear output characteristic, and the error caused by the dispersion of the PSD 4 and the A / D converter 6 as the light emitting element 1 and the light receiving element can be reduced. There is an advantage that it can be absorbed.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention.

For example, if the number of lens extension steps is small or E ²
If the PROM has sufficient capacity, an AF output characteristic diagram is formed based on the AF measurement data Vf measured in advance in the above equation (3), and the lens extension amount corresponding to the AF measurement data Vf is determined. You may make it as a table.

Since this table is stored in the E ² PROM as the storage means 7 in the AF adjustment process, the processing steps of “read Vf ₁ and Vf ₂ from the E ² PROM into the CPU” in the flowchart of FIG. Of ((Vf ₁ , 1 / L ₁ ),
(Find straight line 1 / L = f (Vf) passing through (Vf ₂ , 1 / L ₂ )), and the ranging distance 1 / L is calculated from the AF ranging data Vf.
Since L and lens extension x are uniquely determined, A
There is an advantage that the time from the F distance measurement to the calculation of the lens extension amount can be greatly reduced, and the capacity of the software storage means 7 can be small.

〔The invention's effect〕

As described above in detail, according to the present invention, during the AF adjustment step, the adjustment distance measurement data of a plurality of points at different known distances is stored in the storage unit after A / D conversion, and the AF distance measurement in actual use is performed. At times, read the distance measurement data for adjustment from the storage
Calculates the AF output characteristics by calculating the linear approximation of a straight line passing through multiple points of the AF output vs. distance measurement coordinates, and calculates the distance measurement distance from the AF distance data after A / D conversion and the above output characteristics. Since the lens extension amount is calculated from this distance measurement distance, it is possible to simplify the processing of the AF distance measurement data and shorten the software configuration time, and those with linear output characteristics Of course, it is also possible to adjust the output characteristics of high-order curved AF distance measurement data, which can absorb errors due to variations in the light emitting element, position detection means, A / D converter, etc. It is possible to provide an autofocus camera which occupies a small amount of storage means and can shorten the AF ranging time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of an autofocus camera according to the present invention. FIG. 2 is a diagram showing AF output and lens extension amount versus distance measurement distance 1 for explaining the operation of the embodiment. FIG. 3 is a flow chart for explaining the flow of the operation for storing the adjustment distance measurement data at the time of the AF adjustment process in the embodiment, and FIG. FIG. 5 is a flowchart for explaining a flow of an operation for obtaining a distance measurement distance at the time of AF distance measurement in actual use in the example, FIG. 5 is a circuit diagram of a distance measurement arithmetic circuit of a first conventional example,
FIG. 6 is a circuit diagram of a distance measuring circuit part of the AF camera of the second conventional example, FIG. 7 is a block diagram showing only essential parts of the camera of the third conventional example, and FIG. 3 is a flowchart for explaining a flow of an operation of obtaining distance measurement data and extending a lens in the conventional example, FIG. 9 is a circuit diagram of an electric adjustment circuit of the camera in the fourth conventional example, and FIG. FIG. 9 is a characteristic diagram illustrating a relationship between luminance information and photometric output for describing an example. DESCRIPTION OF SYMBOLS 1 ... Light emitting element, 2 ... Light emitting circuit, 3 ... CPU (arithmetic unit), 4 ... Semiconductor position detecting element, 5 ... Light receiving circuit, 6 ... A / D converter, 7 ... Storage Means 8, lens drive circuit,

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 7/11

Claims (3)

(57) [Claims] 1. A light projecting means for projecting light to a distance measuring object, and a light projecting means arranged at a position where a reflected spot light of the light projected by the distance measuring object is imaged, based on a parallax between the light projecting means and the light projecting means. Position detecting means for continuously detecting the position of the incident spot light according to the distance to be measured in the direction of the position change due to the change in the distance, and analog / digital conversion for converting an analog output of the position detecting means into a digital signal. Storage means for storing three or more adjustment distance measurement data output from the analog / digital converter when three or more distance measurement objects of known distances are measured in the autofocus adjustment step. Based on three or more of the adjustment distance measurement data stored in the storage means, first-order approximation of the middle of the adjustment distance measurement data to interpolate the distance measurement distance versus the autofocus Output characteristic calculating means for calculating the output characteristic of the distance output, and the distance of the object to be measured is determined from the autofocus distance measurement data measured by the position detecting means in actual use and the output characteristic, and the lens extension amount is calculated from the distance. And a feed amount calculating means for calculating the following. 2. An autofocus camera according to claim 1, wherein said storage means is a writable E ² PROM. 3. A light projecting means for projecting light to a distance measuring object, and a light projecting means arranged at a position where a reflected spot light of the light projected by the distance measuring object forms an image, based on a parallax between the light projecting means and the light projecting means. Position detecting means for continuously detecting the position of the incident spot light according to the distance to be measured in the direction of the position change due to the change in the distance, and analog / digital conversion for converting an analog output of the position detecting means into a digital signal. Storage means for storing three or more adjustment distance measurement data output from the analog / digital converter when three or more distance measurement objects of known distances are measured in the autofocus adjustment step. And a camera that first-order approximates the middle of the adjustment distance measurement data based on the three or more adjustment distance measurement data stored in the storage means. Based on the distance measurement output data to form an autofocus output characteristic diagram, autofocus camera and determining the lens movement amount in accordance with the autofocus output characteristic diagram.