JP3080768B2 - Distance measuring device for passive autofocus system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a passive type auto-focusing device which receives light from a subject, measures the distance to the subject, and adjusts the focus based on the measurement result so that the taking lens is focused. A distance measuring device for measuring a distance to a subject.

[0002]

2. Description of the Related Art An autofocus device is a device that automatically measures a photographing distance of a camera or the like, adjusts a photographing lens based on a result of the distance measurement, and adjusts a focus. You can enjoy shooting more easily. Various types of auto-focusing devices have been developed, and the main one is a triangulation-based distance measurement method. There is a passive type that measures the shooting distance by receiving light from the camera.

[0003] Among passive distance measuring devices of this kind, two are known.
Some light receiving sensors are provided. In the distance measuring device including the two light receiving sensors, from the measurement result in the case where two objects are present, the existence of the object can be considered in two ways. There is a possibility that the image will be shifted.

For this reason, the present applicant has already proposed a distance measuring mechanism comprising three light receiving element arrays so that a clear image can be obtained by performing a reliable distance measurement (Japanese Patent Laid-Open No. 3-4).
2642). The principle of distance measurement by this distance measurement mechanism will be described with reference to FIGS. The distance measuring mechanism is the reference light receiving sensor 1 and the first
It comprises a light receiving sensor 2 and a second light receiving sensor 3, and these light receiving sensors 1, 2, and 3 are imaging lenses 1a, 2a, and 3a, respectively.
And the light receiving element arrays 1b, 2b, 3b, so that the subject image passes through the coupling lenses 1a, 2a, 3a and forms an image on the light receiving element arrays 1b, 2b, 3b. FIG. 18 shows a case where one subject P exists. Then, the displacement amount of the output signal P ₀ relating to the luminance distribution of the subject P detected by the light receiving element array 1b serving as a reference from the optical axis T ₀ of the reference light receiving sensor 1 is detected by x ₀ , and detected by the first light receiving element array 2b. The amount of displacement of the output signal P ₁ relating to the luminance distribution of the subject P from the optical axis T ₁ of the first light receiving sensor 2 is x ₁ , and the second light receiving element array 3
b of the output signal P ₂ relating to the luminance distribution of the detected subject P by the second light receiving sensor 3 the amount of displacement from the optical axis T ₂ and x _2. These displacement amounts x ₀ , x ₁ , x ₂ represent phase differences regarding the luminance distribution of the subject image detected by the light receiving element arrays 1b, 2b, 3b. Then, the optical axes T ₀ , T ₁ , T
₂ , the distance between the imaging lenses 1a, 2a, 3a and the light receiving surfaces of the light receiving element rows 1b, 2b, 3b is A,
a, 2a, the distance to the object P Lp, and the distance from the optical axis T ₀ to the subject P and X, the principle of triangulation from 3a,

X = x ₀ * Lp / A Further, including the sign of the direction in which the image of the output signal appears with reference to the optical axis T ₀ ,

[Number 2] _{-x 1 = {(B-X} ) / Lp} * A

X ₂ = {(B + X) / Lp} * A By substituting Equation 1 into each of Equations 2 and 3,

X ₁ = −４ (B / Lp) * A｝ + x ₀

X ₂ = (B / Lp) * A + x ₀

[0005] Comparing Equation 4 and Equation 5, x ₁ , x ₂
Are based on x ₀ , respectively.

It can be seen that there is a shift by (B / Lp) * A = Xp. Therefore, by obtaining this Xp,

## EQU7 ## Lp = A * B / Xp can be calculated.

An operation for obtaining the above Xp will be described with reference to FIG. (A) is a comparison of output signals relating to the luminance distribution of the subject images of the light receiving element arrays 1b, 2b, 3b that have received light from the two subjects P, Q, with reference output signals P ₀ , Q _0. If the waveforms of the output signals P ₁ and P ₂ are shifted until the output signals P ₀ , P ₁ and P ₂ coincide with each other as shown in FIG. Become. That is, since the shift amounts of P ₁ and P ₂ are equal at this time, when the output signals of the light receiving element array 2b and the output signal of the light receiving element array 3b are shifted by the same distance, and the waveforms of the three signals match. The waveforms of these three signals become information on the same subject P. Next, as shown in (C), if the output signals Q ₁ and Q ₂ are shifted until they coincide with the output signal Q ₀ , the shift amount becomes Xq.

The above-mentioned Xp and Xq obtained as described above
From equation (7), the distances Lp to the subjects P and Q are
Lq is required.

[0008]

However, when the above-described conventional distance measuring operation is performed in accordance with the principle, the correlation between the output signal of the reference light receiving element array 1b and the output signal of the first light receiving element array 2b is calculated. Next, the correlation between the output signal of the reference light receiving element row 1b and the output signal of the second light receiving element row 3b is calculated, and the reference light receiving element row 1b, the first light receiving element row 2b, and the second
Since the coincidence of the waveforms of the light receiving element row 3b will be detected,
The number of correlation operations increases and the signal processing time increases. For this reason, the time required for the distance measurement becomes long, and when the subject is dynamic, the image is taken out of focus, and the image may be unclear.

In view of the above, the present invention has three light receiving sensors, can perform signal processing in a short time, can obtain a clear image as much as possible, and has a distance measuring device with a minimum number of parts. It is intended to provide a device.

[0010]

In order to achieve the above object, a distance measuring apparatus for a passive type autofocus apparatus according to the present invention comprises three sets of light receiving sensors having a line sensor for capturing a luminance distribution of a subject; 2. Convert the output signal of the line sensor into a digital signal and calculate a secondary difference of the digital value.
The output signal of the secondary difference calculation circuit and the secondary difference calculation circuit are interpolated, and a zero cross point when the output signal changes from positive to negative and a zero cross point when the output signal changes from negative to positive are determined. A zero-crossing detection circuit for detecting the zero-crossing position signal interpolated within one pixel of the line sensor together with the polarity data with respect to the zero-crossing behavior signal obtained by the zero-crossing detection circuit. A zero-cross memory circuit for separately storing, and a coincidence detecting circuit for comparing the zero-cross position data and the polarity data stored in the respective zero-cross memory circuits to detect coincidence between them. With respect to the zero crossing behavior signal obtained from the light receiving sensor of the reference with respect to one of the After sequentially shifting the zero-cross behavior signal obtained by detecting the coincidence of these zero-cross behavior signals by the coincidence detection circuit, it is characterized in that for calculating the distance to the object from the shift amount.

[0011]

The output voltage corresponding to the object luminance distribution is obtained by the light receiving element array constituting the light receiving sensor, and the secondary difference distribution of the output voltage behaves at the zero level. The zero-cross point of this behavior becomes equal with respect to the luminance distribution of the same part of the subject in a state where the three parts of the line sensor are appropriately shifted from a predetermined reference part.

The amount of deviation can be obtained as a shift amount if the coincidence detection circuit detects the zero-cross position data and the polarity data of the zero-cross behavior by shifting.

Then, the distance to the subject can be calculated from the shift amount by triangulation.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a distance measuring apparatus for an automatic focusing apparatus according to the present invention. FIGS. 1 to 14 show a first embodiment, and FIGS. 15 to 17 show a second embodiment.

Each of the light receiving sensors 10, 20, and 30 is constituted by combining one line sensor composed of a light receiving element array in which an appropriate number of pixels are arranged in parallel and three imaging lenses, as shown in FIG. On the front of the camera are three imaging lenses 10a, 20a,
The light emitted from the subject is transmitted through the imaging lenses 10a, 20a, and 30a to form an image on a corresponding portion of the line sensor 8 disposed behind. Therefore,
The line sensor 8 is divided into three parts, each having a line sensor central part 10b and a line sensor right part 20b.
b, the left side of the line sensor 30b. The light receiving sensors 10, 20, and 30 are respectively a center sensor 10 and a right sensor.
20, the left sensor 30. The optical axes 20c and 30c of the right sensor 20 and the left sensor 30 are symmetrical with respect to the optical axis 10c of the central sensor 10.

As shown in FIG. 1, a drive signal from a sensor driver 11 is input to the line sensor 8, and the line sensor 8 starts capturing light from a subject based on the drive signal. The sensor driver 11 is connected to the control circuit 40 by a drive control signal line 40a, and is controlled by a drive control signal output from the control circuit 40.

On the other hand, the output terminal of the line sensor 8
As shown in FIG. 1, the A / D converter 9 is connected,
The output signal of the line sensor 8 is digitally converted in synchronization with the clock pulse φ1 as shown in FIG. This A
A secondary difference calculation circuit 12 is connected to the output side of the / D converter 9, and the secondary difference calculation circuit 12 calculates a secondary difference of the luminance distribution signal of the subject obtained by the line sensor 8. . As shown in FIG. 3, the secondary difference calculating circuit 12 synchronizes the output signal AD of the A / D converter 9 with the clock pulse φ2 and stores the data by a D flip-flop.
a, 12b memorize sequentially,

[Mathematical formula-see original document] By calculating DIFF (n) = AD (n-2) -2 * AD (n-1) + AD (n), a secondary difference is obtained.

The output signal DIF of the secondary difference calculation circuit 12
As shown in FIG. 1, F is input to the zero-crossing detection circuit 13 and detects the zero-crossing point of the secondary difference obtained by the secondary difference calculation circuit 12. In the zero cross detection circuit 13,
First, the secondary difference signal DI is calculated by the interpolation arithmetic circuit shown in FIG.
FF is interpolated. In this interpolation operation circuit, the secondary difference signal DIFF is stored in a storage circuit 13a using a D flip-flop, and (-1) times and N times the stored value are obtained.
The data multiplied by N is input to the data select circuit 13b,
(-1) The data obtained by adding the multiplied data and the secondary difference signal DIFF are added to the output data of the data selection circuit 13b, and the added data is fed back to the data selection circuit. That is, in the interpolation operation circuit, in synchronization with the clock pulse φ3,

NDIFF (m) = N * DIFF (n-1) + m * (DI
FF (n) -DIFF (n-1)) to linearly approximate the signal DIFF to interpolate the secondary difference signal DIFF. At the same time as this interpolation operation, the sign signal SIGN indicates whether the sign of the data is positive or negative.

Next, as shown in FIG. 5, the sign output SIGN is input to the D flip-flop 13c of the zero-cross detection circuit 13, and the sign output SIGN and the inverted Q terminal of the D flip-flop 13c are connected to an AND circuit. 13d, the output signal of the sign output SIGN via the inverter 13e and the Q terminal of the flip-flop 13c are input to the AND circuit 13f.

That is, as shown in the time chart of FIG. 6, the output signal Vin of the line sensor 8 is input to the A / D converter 9 and is digitally converted to obtain the output signal AD. When this output signal AD is input to the secondary difference calculation circuit 12, the secondary difference signal DIF is synchronized with the clock pulse φ2.
F is obtained, and this signal DIFF is
, The signal DIFF is first linearly approximated and interpolated into a signal NDIFF / N and a sign signal SIG.
N is obtained. The sign signal SIGN is further synchronized by the zero-cross detection circuit 13 with the clock pulse φ3, and the sign signal SIGN is output from the AND circuit 13d.
A pulse P-ZERO that rises when the signal changes from H to H is output as a zero-cross signal, and a pulse N-ZERO that rises when the sign signal SIGN changes from H to L is output from the AND circuit 13f. . That is, the pulse P-ZERO is the secondary differential signal DI
When the interpolation data NDIFF / N of the FF changes from positive to negative and crosses zero, the pulse rises and the pulse N
-ZERO is a signal that rises when the interpolation data NDIFF / N changes from negative to positive and crosses zero.

A signal corresponding to the zero-crossing behavior obtained by the zero-crossing detecting circuit 13 includes a portion corresponding to the line sensor central portion 10b and a portion corresponding to the line sensor right portion 20b,
The data is divided into parts corresponding to the line sensor 30b, and the divided parts are individually inputted to the zero-cross memory circuits 14, 24, and stored. At this time, the zero-crossing behavior is stored in the right part 20b and the left part 30b of the line sensor 8 corresponding to the address output from the address calculation circuits 25 and 35 in accordance with the pixel position. It is stored according to 50 count signals (COUNTER1).
That is, the first counter 50 is provided in the address operation circuits 25 and 35.
The count signal (COUNTER1) is input to the central memory circuit 14.
Are input and sequentially incremented, in the central memory circuit 14,

ADDRESS = COUNTER1 In the right memory circuit 24,

ADDRESS = COUNTER1 In the left memory circuit 34,

## EQU12 ## In accordance with ADDRESS = COUNTER1, it is stored at each address according to each pixel.

A count signal (COUNTER2) of a second counter 60 is input to the address arithmetic circuits 25 and 35, and the second counter 60 and the first counter 50 are controlled based on an output signal of the control circuit 40. Counting up and resetting. The second counter 60 increments an address when data is read from the zero-cross memory circuits 24 and 34, as described later. Further, address processing information is input from the control circuit 40 to the address calculation circuits 25 and 35, and based on the address processing information, a predetermined write signal and readout are performed from the address calculation circuits 25 and 35 to the zero-cross memory circuits 24 and 34. And a signal are output.

The above-mentioned zero-cross memory circuits 14, 24,
The interpolation position count signal (COUNTER3) is input to the interpolation position counting counter 55 from the interpolation position counting counter 55. The interpolation position counting counter 55 counts up and resets based on the output signal of the control circuit 40.
As shown in FIG. 6, the interpolation position counting counter 55 operates in synchronization with a clock pulse φ3 having a shorter cycle than the clock pulses φ1 and φ2, and furthermore, in synchronization with the clock pulse φ3, a secondary differential signal. The DIFF is divided into four parts, and position codes 0 to 3 are assigned to the respective divided parts. Then, corresponding to the interpolation number (4 in this case),
The interpolation position count signal (COUNTER3) of the interpolation position counting counter 55 is stored in the zero-cross memory circuit 1
4, 24, and 34, and the position code corresponding to the interpolation position count signal (COUNTER3) corresponds to the zero cross point detected by the zero cross detection circuit 13 in the zero cross memory circuits 14, 24, and 34. Is stored.

A match detection circuit 70 is connected to the output side of the zero-cross memory circuits 14, 24, 34, and the signals P-ZERO and N of the zero-cross behavior stored in the zero-cross memory circuits 14, 24, 34 are stored. -ZERO and the position code where the zero cross data exists are transmitted. And
The coincidence detection circuit 70 determines whether or not the zero-cross data coincides with the position code. further,
A control circuit 40 is connected to the output side of the coincidence detection circuit 70, and a coincidence signal of zero-cross data is transmitted.

The count signal of the first counter 50 is input to the address port 81 of the data memory circuit 80,
The count signal of the counter 60 is input to the distance data port 82 of the data memory circuit 80, and the interpolation position count signal of the interpolation position counting counter 55 is input to the data memory circuit 80.
Is input to the distance data port 83. Further, count signals of the first counter 50, the second counter 60, and the interpolation position counting counter 55 are all input to the control circuit 40. Further, a data memory signal is output from the control circuit 40 to the data memory circuit 80, and address data and distance data are stored in the data memory circuit 80 based on the signal.

FIG. 7 is a block diagram showing the coincidence detection in the coincidence detection circuit 70. The zero-cross memory of the subject luminance data output from the line sensor central portion 10b, the line sensor right portion 20b, and the line sensor left portion 30b is shown. The data stored in the circuits 14, 24 and 34 are indicated by C data, R data and L data, respectively. The L data is input to a D flip-flop 91 and an arithmetic circuit 92, the R data is input to a D flip-flop 93 and an arithmetic circuit 94, and the data latched by the D flip-flop 91 is The data input to 92 and latched by the D flip-flop 93 are input to the arithmetic circuit 94. Further, the interpolation position counting counter 55
Is input to the arithmetic circuit 92 and the arithmetic circuit 94, respectively. Then, the output of the arithmetic circuit 92 and the output of the arithmetic circuit 94 and the C data are input to the comparison circuit 95, and the data in the case where they are compared and matched by the comparison circuit 95 are output as coincidence data.

Next, with reference to FIGS. 8 to 12, the procedure of writing and reading the luminance information of the subject in the memory will be described. The first counter 50 and the second counter 60 operate in synchronization with the clock pulse φ2, and the interpolation position counting counter 55 operates in synchronization with the clock pulse φ3.

When the distance measurement is started, charges are accumulated in the line sensor 8 (step 801), the second counter 60 is reset (step 802), and the read-out pixel number counter (not shown) in the control circuit is reset (step 801). Step 803
).

Since the line sensor 8 is composed of one line, it is first determined whether reading of the first pixel of the portion related to the line sensor left portion 30b has started based on the value of the read pixel number counter (step S1). 804),
The output is performed one pixel at a time until the reading of the first part is started (step 805). If the reading of the first portion is started, the process proceeds to step 806, where the first counter 50 is reset.

Next, after proceeding to step 901 (FIG. 9) to reset the counter 3, data relating to one pixel of the line sensor left portion 30b of the line sensor 8 is read (step 902). Then, the process proceeds to step 903, where
The interpolation operation is executed according to the equation to obtain the interpolation data NDIFF.
/ N is calculated, and a zero-cross point is detected together with the sign signal SIGN of the interpolation data. At this time, the interpolation calculation is performed based on the interpolation position count signal by counting up the interpolation position counter 55, and the count value of the interpolation position counter when the zero cross point is detected is stored (not shown). ). Next, proceeding to step 904, it is determined whether or not interpolation has been completed, that is, whether or not one pixel read out in step 902 has been divided into a predetermined number and interpolation has been performed, based on the value of the interpolation position counting counter 55. If not completed, the process proceeds to step 905, where the counter 55 for counting the interpolation position is counted up, and the process returns to step 903. Steps 903 and 904 are repeated until the interpolation is completed. When the division is completed, the process proceeds to step 906.

In step 906, the read pixel number counter is counted up, and the flow advances to step 907 to proceed to step 902.
The interpolated position data stored corresponding to one pixel of the line sensor left portion 30b read out and interpolated is written into the left zero cross memory circuit 34. Next, the process proceeds to step 908, where it is determined whether reading has been completed for all the pixels included in the line sensor left portion 30b, based on the value of the first counter 50. Step up after counting up 1 counter 50
Returning to 901, one pixel reading (step 902), interpolation calculation, zero cross detection (step 903), and writing to the left zero cross memory circuit 34 (step 907) are performed. When data is written to the left zero-cross memory circuit 34, an address is specified from the address arithmetic circuit 35 based on the count signal of the first counter 50 and stored. At this time, the data to be stored are the zero-cross position data and the polarity data, and the address to be stored is specified according to the above equation (12).

When reading of all the pixels of the left portion 30b of the line sensor is completed and YES is obtained in Step 908, Step 10 is executed.
In step 01 (FIG. 10), it is determined whether reading of the first pixel of the portion related to the line sensor central portion 10b has been started based on the value of the read pixel counter, and 1 is maintained until reading of the first portion is started. It is output pixel by pixel (step 1002). If the reading of the first part is started, the first counter 50 is reset (step 100).
3) As in steps 901 to 909, one pixel is read out after the interpolation position counting counter 55 is reset (step 1004) for the line sensor central portion 10b (step 1005), and the interpolation position counting is performed. While determining the completion of interpolation based on the signal value (step
1007, 1008), the interpolation calculation and the zero-cross detection (1006) are executed, then the read-out pixel number counter is counted up (step 1009), and the read data of one pixel is written into the central zero-cross memory 14 (step 1009). Steps
1010), the center of the line sensor based on the value of the first counter 50
Judgment of read completion for all pixels of 10b (step
1011) are repeated while counting up the first counter 50 (step 1012). The address to be stored is specified in accordance with equation (10).

When reading of all the pixels in the line sensor central portion 10b is completed and YES is determined in the step 1011, the process proceeds to a step 1101 (FIG. 11) to output one pixel at a time (step 1102). Right part 20b
The start of reading of the first pixel of the relevant portion is determined by the value of the read pixel number counter, and if the reading of the first portion is started, the first counter 50 is reset (step 1103). And the line sensor left part 30b
Similarly to the procedure for the line sensor center 10b, the interpolation position counting counter 55 is reset (step 1004) for the line sensor right portion 20b, and then one pixel is read out (step 1105). (Step 11)
07, 1108), the interpolation calculation and the zero-cross detection (1106) are executed, and then the read-out pixel number counter is counted up while the zero-cross detection is being performed (step 1109).
Is written to the right zero-cross memory 24 (step 1110), and the first counter 50
(Step 1111), the determination of the completion of reading of all the pixels of the line sensor right portion 20b by the value of
Is repeated (step 1112). When data is written to the right-side zero-cross memory circuit 24, the data is stored in the address specified by the address arithmetic circuit 25 in accordance with Equation 11 based on the count signal of the first counter 50.

If reading of all pixels of the line sensor 8 is completed and the determination in the step 1111 is YES,
Proceeding to step 1201 (FIG. 12), the interpolation position counting counter 55 is reset, and the first counter 50 is reset (step 1202). And the zero cross memory circuit 14,
Steps 907 and 1010, steps from 24 and 34
The memory data written in 1110 is read (step 1203), and the coincidence detection circuit 70 determines whether or not the data in the central zero cross memory circuit 14, the right zero cross memory circuit 24, and the left zero cross memory circuit 34 match (step 1203). Step 1204).

The data conversion operation at the time of coincidence detection in the coincidence detection circuit 70 is performed when the number of interpolations is "4".
(n) and L (n) are represented by r (n) and l (n), respectively. For the position data of R (n), r (n) + 4-COU
For the position data of NTER3 R (n-1), r (n-1) -COUN
TER3 l (n) + COUNT for position data of L (n)
ER3 For the position data of L (n-1), l (n-1) -4 + CO
Regarding the position data and polarity data converted by UNTER3, C
It is detected that all of the data, R data, and L data match. That is, FIG. 13 is a diagram for explaining the coincidence detection calculation performed in FIG. 7, and as shown in FIG.
With the data for one pixel of the C data fixed,
Match detection is performed while incrementing COUNTER3. Now, regarding the L data, the position data L (n
-1), L (n) and L (n + 1) are set to -4 to 7 from the upper bit side, and the position data R (n-2) and R (n-1 ) And R (n) are -4 to 7 from the upper bit side. When the interpolation position counter signal is 0 (COUNTER3 = 0), the position codes 0 to 3 of the L data and the position codes 0 to 3 of the R data are compared with the position codes 0 to 3 of the C data. You. Next, COUNTER3 is counted up. When COUNTER3 = 1, the position codes 1 to 4 for the L data and the position codes -1 and 2 for the R data are 0 to 3 for the position codes 0 to 3 of the C data. The position code is converted into a position code of 3 and subjected to a match comparison.
When COUNTER3 = 2, the position codes 2 to 5 for the L data correspond to the position codes 0 to 3 for the C data.
In the R data, the position codes -2 to 1 are converted into position codes of 0 to 3, respectively, and are subjected to coincidence comparison. Further, C
When OUTER3 = 3, the position codes 3 to 6 of the L data correspond to the position codes 0 to 3 of the C data.
In the data, the position codes -3 to 0 are converted into position codes 0 to 3, respectively, and are subjected to coincidence comparison.

If the data match, the process proceeds to step 1205, where the first counter 50
The count signal (COU1) of the second counter 60 is used as the address data using the value of the count signal (COUNTER1)
NTER2) as the upper bits of the distance data, and the interpolation count signal (CO
The numerical value of UNTER3) is written to the data memory circuit 80 as the lower bits of the distance data. If the determination in step 1204 is NO, the process proceeds to step 1206, where it is determined whether reading of memory data (reference data) corresponding to all valid pixels in the central portion 10b of the line sensor 8 has been completed. Judgment is made based on the value of the counter 50, and if not completed, the process proceeds to step 1207, where the first counter 50 is counted up, and then returns to step 1203 to execute step
Execute up to 1206.

When the reading of the reference data is completed, the flow advances from step 1206 to step 1208 to determine whether or not the interpolation has been completed according to the value of the interpolation position counting counter 55, that is, the data of the predetermined number of divided position codes is read. It is determined whether a match has been determined. If the interpolation has not been completed, the process proceeds to step 1209 to count up the interpolation position counting counter 55, and then returns to step 1202 to repeat the above steps 1202 to 1208. If the determination in step 1208 is YES, the process proceeds to step 1210, where the data of the right and left zero-cross memory circuits 24 and 34 are shifted by a specified amount with respect to the data of the central zero-cross memory circuit 14, and 12
It is determined from the value of the second counter 60 whether or not steps 01 to 1208 have been executed (shift reading) (step 1210). If the shift read is not completed,
The second counter 60 counts up, returns to step 1201, and repeats steps 1202 to 1210. When the shift reading is completed, the process proceeds to step 1212.

The reading of the memory data from step 1202 to step 1211 is performed by the first counter 50 and the address arithmetic circuits 25 and 35 by using the equations (10), (11),
According to the equation 12, from the center zero cross memory circuit 14,

ADDRESS = COUNTER1-1 From the right side zero cross memory circuit 24,

ADDRESS = COUNTER1 + COU
NTER2 From the left zero cross memory circuit 34,

ADDRESS = COUNTER1 + S−1
Readout according to -COUNTER2. Note that S in Expression 15 is a constant. The relationship between the write address and the read address at this time will be described with reference to FIG. When the address is negative, no reading is performed.

FIG. 14A shows a case where the count signal of the second counter 60 is 0 (COUNTER2 = 0). At this time, while the first counter 50 is incremented from 0 to W (step 1207), the line sensor 8 Each part of 10b, 20b,
The data stored in the address corresponding to each pixel of 30b is compared to detect a match between the data. Therefore, when COUNTER2 = 0, the address is incremented from 0 to (W-1) at the pixel at the line sensor central portion 10b, the address is incremented from 0 to W at the pixel at the line sensor right portion 20b, and the line sensor left portion is incremented. For the 30b pixel, the address is changed from (S-1) to (S +
W-1) is incremented. Then, for the pixel included in one address of the center zero cross memory circuit 14, as shown in FIG. 13 described above, the right zero cross memory circuit 24 and the left zero cross memory circuit 34 are located at two adjacent addresses respectively. While the pixels are sequentially shifted in accordance with the position code obtained by dividing the pixels by the interpolation number, the coincidence is detected.

Next, the second counter 60 is incremented (step 1211), and as shown in FIG. 14 (b), the first counter 50 is set to 0 while the count signal of the second counter 60 is 1 (COUNTER2 = 1). While incrementing from W to W (step 1207), each part 10 of the line sensor 8 is
The data stored in the addresses corresponding to the pixels b, 20b, and 30b are compared to detect a match between the data.
Therefore, when COUNTER2 = 1, the address ranges from 0 to (W-1) for the line sensor central portion 10b and 1 to (W + 1) for the line sensor right portion 20b.
Is incremented from (S-2) to (S + W-2) for the line sensor left portion 30b. That is,
The memory data of the right side zero cross memory circuit 24 and the left side zero cross memory circuit 34 are stored in the central zero cross memory circuit 14.
Is shifted from the memory data of FIG.
As shown in FIG. 13, the data included in the position code obtained by dividing one pixel at one address of the central zero cross memory circuit 14 into a predetermined number is compared with the right zero cross memory circuit 24.
The coincidence detection is performed while the data included in the position code obtained by dividing the pixel at the two adjacent addresses of the left zero cross memory circuit 34 is shifted.

Then, while incrementing the second counter 60 (step 1211), the coincidence detection is repeated until the count signal of the second counter 60 becomes COUNTER2 = S-1.

That is, the zero-cross memory circuits 14, 24,
When the memory data of 34 coincides with respect to the zero-cross point, the value of the value of the second counter 60 as the upper bit and the value of the interpolation position counting counter 55 as the lower bit corresponds to the shift amount Xp in the equation (6). . Then, this shift amount is stored in the data memory circuit 80 as distance data in step 1205.

If it is determined in step 1210 that the predetermined shift readout is completed, the flow advances to step 1212. In step 1205, the distance data written in the data memory circuit 80 is output to a photographic lens driving device (not shown). The lens moves to a predetermined position to focus on the subject.

The data stored in the zero-cross memory circuits 14, 24 and 34 for the above-mentioned coincidence detection are polarity data and position data. The position data is divided into, for example, a quadratic differential signal DIFF and divided into four. When storing at the address of each part, a memory capacity of 4 bits is required for one polarity and one bit is required for two polarities, but it is stored as polarity data and a position code. In this case, a memory capacity of 2 bits as the memory for the position code, 1 bit for the presence / absence of data, and 1 bit for the polarity data is sufficient for a total of 4 bits. Therefore, the required memory capacity can be reduced, and the processing time for matching comparison can be reduced.

Next, a second embodiment shown in FIGS. 15 to 17 will be described.

In the second embodiment, the light receiving sensors 10, 20,
Numeral 30 is configured by combining a line sensor composed of a light receiving element array in which an appropriate number of pixels are juxtaposed and an imaging lens,
As shown in FIG. 16, three imaging lenses 10 are provided in front of the camera.
a, 20a, and 30a are provided, and light emitted from the subject passes through these imaging lenses 10a, 20a, and 30a to form an image on line sensors 10b, 20b, and 30b that are provided behind. The light receiving sensors 10, 20, and 30 are a central sensor 10, a right sensor 20, and a left sensor 30, respectively. The optical axes 20c, 30c of the right sensor 20 and the left sensor 30 are the central sensor.
It is located symmetrically with respect to ten optical axes 10c. The line sensors 10b, 20b, and 30b are respectively a center line sensor 10b, a right line sensor 20b, and a left line sensor 30b.
b.

The line sensors 10b, 20b, 30b have
As shown in FIG. 15, drive signals from the sensor drivers 11, 21, and 31 are separately input, and the line sensors 10b, 20b, and 30b start capturing light from the subject based on the drive signals. The sensor drivers 11, 21, and 31 are connected to the control circuit 40 by a drive control signal line 40a.
Is controlled by a drive control signal output from the controller.

On the other hand, the output terminals of the line sensors 10b, 20b, 30b are connected to the A / D converter 16, as shown in FIG.
26 and 36 are connected to convert the output signals of the line sensors 10b, 20b and 30b into digital signals. This A / D converter
On the output side of 16, 26, and 36, respectively, the secondary difference calculation circuit 1
2, 22, and 32 are connected, and the second-order difference calculation circuits 12, 2
Line sensors 10b, 20b, 30b by 2, 32
The secondary difference of the luminance distribution signal of the subject obtained in the above is calculated. The secondary difference operation circuits 12, 22, and 32 are the same as those in FIG. 3 shown in the first embodiment, and the secondary difference is calculated by the above equation (8).

As shown in FIG. 15, the output signals of the secondary difference calculation circuits 12, 22, and 32 are zero-cross detection circuits 13, 2
3 and 33, and the secondary difference operation circuits 12, 22, and 32
The zero-cross point of the secondary difference obtained by the above is detected. The zero-cross detection circuits 13, 23, and 33 are the same as those shown in FIGS. 4 and 5 of the first embodiment. -ZERO and a pulse N-ZERO are detected.

The signals of the zero-crossing behavior obtained by the above-mentioned zero-crossing detecting circuits 13, 23, 33 are input to and stored in the zero-crossing memory circuits 14, 24, 34, respectively. At this time, the zero-cross behavior depends on each line sensor 10b, 2
Address operation circuits 15, 2 corresponding to pixel positions 0b, 30b
It is stored in correspondence with the address output from 5, 35.
That is, the count signal (COUNTER1) of the first counter 50 is input to the address operation circuits 15, 25, and 35, and the address signal is sequentially incremented.

ADDRESS = COUNTER1-S In the right memory circuit 24,

ADDRESS = COUNTER1-S In the left memory circuit 34,

## EQU18 ## In accordance with ADDRESS = COUNTER1, it is stored at each address according to each pixel. Note that S in Expressions 16 and 17 is a constant.

The count signals (COUNTER2) of the second counter 60 are input to the address arithmetic circuits 25 and 35, and the second counter 60 and the first counter 50 are controlled based on the output signals of the control circuit 40. Counting up and resetting. The second counter 60 increments the address when data is read from the zero cross memory circuits 24 and 34. Further, address processing information is input from the control circuit 40 to the address calculation circuits 15, 25, and 35, and the zero-cross memory circuits 14, 2 are input from the address calculation circuits 15, 25, 35 based on the address processing information.
Predetermined write and read signals are output to 4 and 34.

Further, the zero cross memory circuits 14, 24,
In the same manner as in the first embodiment, the interpolation position count signal (COUNT
R3) is input, and the interpolation position counting counter 55 counts up and resets based on the output signal of the control circuit 40. As shown in FIG. 6, the interpolation position counting counter 55 operates in synchronization with a clock pulse φ3 having a shorter cycle than the clock pulses φ1 and φ2, and performs writing and reading by dividing data into small pieces. In addition, the secondary differential signal DIFF is divided into four in synchronization with the clock pulse φ3,
Position codes 0 to 3 are assigned to the respective divided parts. The interpolation position count signal (COUNTER3) of the interpolation position counting counter 55 corresponding to the number of interpolations (in this case, 4) is stored in the zero-cross memory circuit 1.
4, 24, and 34, and the position codes are detected by the zero-cross memory circuits 14, 24, and 34 by the zero-cross detection circuits 13, 23, and 33 in synchronization with the interpolation position count signal (COUNTER3). The position code of the zero-cross point is stored.

A match detection circuit 70 is connected to the output side of the zero-cross memory circuits 14, 24, 34, and the signals P-ZERO and N of the zero-cross behavior stored in the zero-cross memory circuits 14, 24, 34 are stored. -ZERO and the position code where the zero cross data exists are transmitted. And
The coincidence detection circuit 70 determines whether or not the zero-cross data coincides with the position code. further,
The control signal 40 is connected to the output side of the coincidence detection circuit 70, and a coincidence signal of zero cross data is transmitted.

The count signal of the first counter 50 is input to the address port 81 of the data memory circuit 80,
The count signal of the counter 60 is input to the distance data port 82 of the data memory circuit 80, and the interpolation position count signal of the interpolation position counting counter 55 is input to the data memory circuit 80.
Is input to the distance data port 83. Further, count signals of the first counter 50, the second counter 60, and the interpolation position counting counter 55 are all input to the control circuit 40. Further, a data memory signal is output from the control circuit 40 to the data memory circuit 80, and address data and distance data are stored in the data memory circuit 80 based on the signal.

Next, the procedure for writing and reading the luminance information of the subject in the memory will be described with reference to FIG.

When the distance measurement is started, the line sensors 10b, 20
b and 30b are accumulated (step 1701), the second counter 60 is reset (step 1702), and the first counter
50 is reset (step 1703), and the interpolation position counting counter 55 is reset (step 17).
04). Then, data corresponding to one pixel of each of the line sensors 10b, 20b, and 30b is read (step 1705), and interpolation calculation and detection of a zero-cross point are performed as in the first embodiment (step 1706). Next, it is determined whether or not the interpolation has been completed based on the value of the interpolation position counting counter 55 (step 1707). If the interpolation has not been completed, the interpolation position counting counter 55 is counted up (step 1708). Returning to 1706, steps 1706 and 1707 are repeated until the interpolation is completed. When the interpolation is completed, the process proceeds to step 1709, where the read data is written to the zero cross memory circuits 14, 24, 34 (step 1709). Then, the process proceeds to step 1710, where it is determined whether reading has been completed for all pixels based on the value of the first counter 50.
Proceeding to 1711, the first counter 50 is counted up, and the process returns to step 1704, where the interpolation position counting counter 55
Reset (step 1704), one pixel read (step 1705), interpolation calculation, and zero-cross detection (step 170)
6), the completion of interpolation is determined (step 1707), and writing to the zero-cross memory circuits 14, 24, 34 is performed (step 1709). Then, when data is written to the zero-cross memory circuits 14, 24, 34, the data is stored in a memory whose address is designated by the address operation circuits 15, 25, 35 based on the count signal of the first counter 50. At this time, the address to be stored is specified in accordance with the above formulas (16), (17) and (18). If the address is negative, no writing is performed.

If the reading of all pixels is completed and the determination in step 1710 is YES, the procedure from step 1201 to step 1212 shown in FIG. 12 is executed. That is, the memory data is read from the zero-cross memory circuits 14, 24, and 34 (step 1203), and the coincidence detection circuit 70 matches the data in the center zero-cross memory circuit 14, the right-side zero-cross memory circuit 24, and the left-side zero-cross memory circuit 34. It is determined whether or not to do so. Note that the data conversion operation at the time of detecting a match in the match detection circuit 70 is the same as described above.
When the shift reading is completed, the distance measurement data is output from the data memory circuit 80 (step 121).
2).

In the procedure for detecting the coincidence of the memory data of the zero-cross memory circuits 14, 24 and 34, the first counter 50 and the address arithmetic circuits 25 and 35 use the above-mentioned equation (16) and equation (17).
The central zero-cross memory circuit 14 corresponds to the equation
From

ADDRESS = COUNTER1-1 From the right side zero cross memory circuit 24,

[Equation 20] ADDRESS = COUNTER1 + COU
NTER2 From the left zero cross memory circuit 34,

ADDRESS = COUNTER1 + S−1
Readout according to -COUNTER2. Note that S in Equation 21 is a constant. The relationship between the write address and the read address at this time is the same as in the case of the first embodiment described above.
Match detection is performed while incrementing the first counter 50 from 0 to W.

[0059]

As described above, according to the distance measuring apparatus for a passive type auto-focusing apparatus according to the present invention, the luminance of the subject is captured by three sets of light receiving sensors, and the secondary difference is calculated from the data. The zero-cross data of the next difference is stored with the zero-cross point of the next difference as a feature point, and the zero-cross data obtained from the other two light-receiving sensors is sequentially set to 1 based on the zero-cross data obtained from one of the three light-receiving sensors. Since the three data are compared with each other with respect to the zero-cross point while shifting each pixel, the distance to the subject is calculated using the shift amount when the three data match as the distance data. The calculation processing speed is faster than that required. Therefore, it is possible to reliably capture a dynamic subject and perform quick focusing. Moreover, the output signal of the line sensor is A / D
Since the conversion is performed and the secondary difference is calculated by digital processing, the calculation processing is simplified and the processing speed can be further increased as compared with the analog processing.

Further, since the output signal of the secondary difference calculation circuit is interpolated, distance division can be increased with a small number of pixels.

Further, since the position data and the polarity data interpolated within one pixel of the zero-cross data for which a match is to be detected are stored, the memory capacity can be reduced.

In addition, since the zero-cross data of the secondary difference is compared, the distance data can be obtained with high accuracy because it does not depend on the pattern of the subject luminance distribution on the line sensor.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a first embodiment of a distance measuring apparatus for a passive type autofocus apparatus.

FIG. 2 is a side view showing a schematic structure of a light receiving sensor.

FIG. 3 shows A / D conversion of the output of the line sensor, and FIG.
FIG. 3 is a circuit block diagram of a secondary difference calculation circuit that performs digital processing on a next difference and calculates the difference.

FIG. 4 is a block diagram of an interpolation operation circuit that interpolates an output signal of a secondary difference operation circuit by digitally processing the signal to approximate the signal linearly;

FIG. 5 is a circuit diagram of a zero-crossing detection circuit that detects a zero-crossing point of the interpolated data of the secondary difference signal obtained by the secondary difference calculation circuit.

FIG. 6 is a time chart of output signals of a line sensor, an A / D converter, a secondary difference calculation circuit, and a zero-cross detection circuit.

FIG. 7 is a block diagram of a zero-cross data match detection circuit;

FIG. 8 is a flowchart showing a procedure for writing data obtained from a line sensor into a zero-cross memory circuit, and is a part of a process relating to a left portion of the line sensor.

FIG. 9 is a flowchart showing a procedure for writing data obtained from the line sensor into the zero cross memory circuit, which is another part related to the left part of the line sensor.

FIG. 10 is a flowchart showing a procedure for writing data obtained from a line sensor to a zero-cross memory circuit, and relates to a central portion of the line sensor.

FIG. 11 is a flowchart showing a procedure for writing data obtained from a line sensor into a zero-cross memory circuit, and relates to a right portion of the line sensor.

FIG. 12 is a flowchart showing a procedure for reading predetermined data from the zero-cross memory circuit in order to detect a coincidence of data stored in the zero-cross memory circuit.

FIG. 13 is a conceptual diagram for describing a procedure for detecting coincidence of data stored in a zero cross memory circuit.

FIG. 14 is a diagram illustrating an operation procedure when reading and comparing data stored in the zero-cross memory circuit.

FIG. 15 is a circuit block diagram of a second embodiment of the distance measuring apparatus for a passive type autofocus apparatus.

FIG. 16 is a side view showing a schematic structure of a light receiving sensor of a second embodiment.

FIG. 17 is a flowchart illustrating a procedure for writing data obtained from a line sensor into a zero-cross memory circuit.

FIG. 18 is an optical path diagram illustrating a principle of distance measurement.

FIG. 19 is a diagram for explaining a measurement procedure based on the principle of distance measurement, and is a signal diagram relating to a luminance distribution of a subject image detected by a light receiving element array.

[Explanation of symbols]

 10, 20, 30 Light receiving sensor 10a, 20a, 30a Imaging lens 10b Center line sensor 20b Right line sensor 30b Left line sensor 9, 16, 26, 36 A / D converter 11, 21, 31 Sensor driver 12, 22, 32 Secondary difference calculation circuit 13, 23, 33 Zero cross detection circuit 14, 24, 34 Zero cross memory circuit 15, 25, 35 Address calculation circuit 40 Control circuit 50 First counter 60 Second counter 55 Interpolation position count counter 70 Match detection Circuit 80 Data memory circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) G01C 3/00-3/32 G02B 7/11 G02B 7/28-7/32 G03B 13/36

Claims (1)

(57) [Claims] 1. A set of three light receiving sensors having a line sensor for capturing a luminance distribution of a subject, and a secondary difference calculating circuit for converting an output signal of the line sensor into a digital signal and calculating a secondary difference of the digital value. Interpolating the output signal of the secondary difference calculation circuit, and a zero crossing point when the output signal changes from positive to negative;
A zero-crossing detection circuit that determines a zero-crossing point when the value changes from negative to positive, and detects it as polarity data; and a zero-crossing position interpolated within one pixel of the line sensor with respect to a zero-crossing behavior signal obtained by the zero-crossing detection circuit. A zero-cross memory circuit that stores data together with the polarity data with respect to the three sets of light-receiving sensors; And a zero-crossing behavior signal obtained from one of the three sets of light receiving sensors as a reference and obtained from the reference light receiving sensor.
The passive cross-talk signal obtained by sequentially shifting the zero-cross behavior signals obtained from the other two parts, detecting the coincidence of these zero-cross behavior signals by the coincidence detection circuit, and calculating the distance to the subject from the shift amount. Distance measuring device for type autofocus device.