JP2001021343A - Range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent false range finding even when another object exists in a range finding area at a different distance by providing a selecting means which selects the next range finding point in accordance with the range-found result of a prescribed point in a photographed picture. SOLUTION: A light emitting section is composed of a light projecting lens 1, a plurality of light emitting elements (IRED) 3, and a driver 6 for IRED and a light receiving section is composed of a light receiving lens 2, a position sensor (PSD) 4, and an IC (AFIC) 5 for analog operation 5. An arithmetic and control circuit (CPU) 7 decides a photographing distance by correcting and computing the output of the AFIC 5 and, at the same time, controls a motor 9 for driving photographing lens through a motor driver 8. The CPU 7 sends a range finding starting signal to the AFIC 5 by closing a switch 10 for release. When the CPU 7 sends the signal, a selecting means selects the next range finding point out of range finding points other than a prescribed point in accordance with the range-found result of the prescribed point in a photographed picture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device, and more particularly to a distance measuring device capable of measuring a subject distance corresponding to a plurality of points in a photographing screen.

[0002]

2. Description of the Related Art A camera having a distance measuring device for irradiating a subject with a light beam and receiving reflected light from the subject by a light receiving means to obtain distance information is widely used. The distance can be measured only at one point on the screen, mainly at the center. Therefore, if the main subject deviates from this point, a state called a so-called “hollow” occurs, and an out-of-focus photograph in which the main subject is out of focus is taken.

Therefore, a multi-point distance measuring device which irradiates a plurality of spot lights to a plurality of points on a screen and obtains a subject distance from the reflected light to prevent a dropout is disclosed in, for example, Japanese Patent Laid-Open No. 58-1983. -9013 and Japanese Patent Application Laid-Open No. 58-76.
No. 715, for example. In this type of multi-point distance measuring apparatus, since there is a high possibility that the subject is located at the closest distance point out of the distance information of the plurality of measured distance points, the photographing lens is driven and controlled to the closest distance. It has become.

[0004]

However, when measuring a distance to a plurality of distance measuring points, an object at another distance may be mixed in the distance measuring area, causing an error in the distance measuring. For example, in a distance measuring device that irradiates a subject with spot light, distance measurement can be accurately performed if all the spot light having a finite spread is applied to the subject. Since only the portion is reflected, an erroneous distance measurement occurs. Therefore, the problem of the erroneous distance measurement will be described with reference to FIGS. 9A to 11B.

FIG. 9A shows the state of the spot light 21 on the subject 11, and FIG. 9B shows the state of the reflected light 21 on the light receiving element (PSD) 4.
The state of a is shown.

[0006] As shown in FIG.
If the reflected light 21a completely enters
The light is ideally incident on the SD 4, and the PSD 4 outputs the correct distance measurement output from the position of the center of gravity. Then, the position of the center of gravity moves from a position corresponding to infinity on the PSD 4 to a position corresponding to the closest distance on the PSD 4 according to the subject distance.

However, as shown in FIGS. 10A and 11A, when the subject 11 is slightly shifted from the position of the spot light 21 and the spot light is not completely reflected, the distance is measured from the position of the center of gravity of only the reflected light. For output, even in the case of the subject 11 at the same distance as in FIG. 9A, in FIG. 10A, the position of the center of gravity is shifted to a short distance side on the PSD as shown in FIG. 10B, and is closer to that in FIGS. 9A and 9B. Outputs the distance measurement closer to the distance side. Conversely, in the case of FIG. 11A, the distance measurement output is shifted toward the far side as shown in FIG. 11B.

When one PSD receives one spot light, the amount of the erroneous distance measurement can be relatively small.
In the case of a multi-point distance measuring device that receives a plurality of spot lights with one PSD, the amount of movement of one spot light on the PSD from infinity to close distance is small. Ranging is a big one.

Further, there is a risk that the erroneous distance measurement due to the departure of the spot light may occur for each spot light, and the risk of the multi-point distance measuring device is increased by the number of multi-points as compared with the one-point distance measuring device. In addition, since the distance measurement output deviating to the short distance side is used as the distance measurement result, a photograph out of focus may be taken.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in a distance measuring apparatus capable of measuring a distance at a plurality of points, an erroneous distance measurement is performed even when objects of different distances are mixed in the distance measuring area. It is an object of the present invention to provide a distance measuring device that does not perform the measurement.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, a distance measuring apparatus according to the present invention is a distance measuring apparatus for measuring a plurality of points in a photographing screen. According to another feature of the present invention, there is provided a selecting means for selecting a point to be measured next from other distance measuring points other than the predetermined point according to the distance result.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

Before describing the operation of this embodiment, the basic concept of the distance measuring apparatus of the present invention will be described with reference to FIGS. 2A to 2D, and a known practical measurement method using a PSD will be described with reference to FIG. Each of the distance devices will be described.

FIG. 2A is a diagram showing a distance measurement result when chart distance measurement is performed on a human face having a diameter of about 200 mm using the distance measurement apparatus shown in FIG. 1, and FIG. 2B shows an experimental method thereof. In the figure, when the subject distance l0 is set to around 2 m and the distance is measured while shifting the chart in the x direction substantially perpendicular to l0, as shown in FIG. Points x1, x2, x4,
Points x3, x5, and x6 at which a distance measurement error occurs on the far side become apparent.

According to the present invention, the distance measurement error occurring in the vicinity of x2 and x4 is intended to be improved by using adjacent distance measurement data. Data corresponding to the closest distance is output in x2 and x4. If so, ignore this.

Here, it is determined whether a distance measurement output corresponding to a close distance is output when a distance is actually measured at a close distance or a distance measurement output corresponding to the close distance is output due to a spot departure. The decision is made based on whether or not the data is closer to 1N. For example, in macro photography in which a subject at a distance of less than 1 m is photographed, the distance d1 between the IRED spots (see FIG. 2B) is relatively shorter than d1 = ltan .theta. This is because it is considered that data of two points among the light spots L, C, and R are similarly output data closer to the short distance comparison value 1N.

On the other hand, when the projection spot C outputs a result equivalent to the close-up due to the spot departure as shown in FIG. 2D, it is considered that the other points output results other than the close-up at a considerably high probability. . These determinations and determination of the payout distance are performed by a CPU 7 described later. The above is an explanation of the basic concept of the distance measuring apparatus of the present invention.

Next, referring to FIG. 3, P
A known one-point distance measuring device using the SD4 will be described.

When the IRED 3 'projects distance measuring light to the object 11 via the light projecting lens 1, the light receiving lens 2 condenses the reflected light of the distance measuring light on the object and forms the object image on the PSD 4. Form an image. At this time, the incident position x of the reflected light is a function of the subject distance 1 as shown in the following equation based on the principle of triangulation.

X = S · f / l (1) where S is the distance between the principal points of the light projecting and receiving lens (base line length), f is the focal length of the light receiving lens 2 and the PSD at this position.
4 are arranged. The PSD 4 outputs two photocurrent signals I1 and I2 which are functions of the incident position x of the distance measuring signal light. Now, when a line parallel to a line connecting the emission center of the IRED 3 ′ and the principal point of the light projecting lens 1 is extended from the principal point of the light receiving lens 2, a point crossing the PSD 4 is represented by PSD 4.
Assuming that the total signal light current is Ip0 and the total length of PSD4 is t at a point having a length a from the end on the IRED side, I1 = ｛(a + x) / t｝ Ip0 (2) I2 = [｛t − (A + x)｝ / t] Ip0 (3) Therefore, according to the above equations (2) and (3), the photocurrent ratio I1 / (I1
+ I2) can be obtained by calculation.

I 1 / (I 1 + I 2) = (a + x) / t = (1 / t) {a + (S · f / l)} (4) In the above equation (4), the total length t of PSD 4 , P
Since the length a from the IRED side terminal of SD4, the base line length S, and the focal length f of the light receiving lens are constants, if the photocurrent ratio I1 / (I1 + I2) is obtained, the reciprocal 1 / l of the object distance l is obtained. You can ask. The above is the description of the known single-point distance measuring device using the PSD.

Next, a distance measuring apparatus according to an embodiment of the present invention will be described. FIG. 1 is a configuration block diagram of a camera using a distance measuring apparatus according to an embodiment of the present invention. This camera includes a light emitting unit including a light projecting lens 1, a plurality of light emitting elements (IRED) 3, and an IRED driver 6, and a light receiving unit including a light receiving lens 2, a PSD 4, and an analog operation IC (AFIC) 5. An arithmetic control circuit (CPU) 7 composed of a one-chip microcomputer or the like, which corrects the output result of the AFIC 5 to determine the photographing distance and controls the photographing lens driving motor 9 via the motor driver 8. Consists of The IRED 3 has an IRED 3C as a first light projecting means disposed at the center thereof, and IREDs 3R and 3L as second light projecting means disposed on both sides thereof.
Consists of Reference numeral 10 denotes a release switch, 1
1 is a subject.

The CPU 7 sends a distance measurement start signal to the AFIC 5 by closing the release switch 10 shown in FIG. At this time, the IRED emission driver 6
Are enabled by the CPU 7 so that the central IRED 3c as the first light emitting means emits light. And the actual light emission timing is AFI
Determined by C5. About AFIC5,
The details are described in Japanese Patent Application Laid-Open Nos. 63-132110 and 1-1114707 proposed by the present applicant, but here, as shown in FIG.
AF based on the same operation principle as that disclosed in
The circuit will be briefly described.

In the figure, reference numeral 4 denotes the same P as in FIG.
In the SD, reference numerals 12a and 12b denote preamplifiers for removing a photocurrent output from the PSD 4 in a DC state and amplifying only an IRED signal photocurrent incident on the PSD 4 in a pulsed manner.

The preamplifier outputs Ix and Iy are injected as current signals into the compression diodes 13 and 14, respectively, and are converted into compressed voltage signals. Reference numerals 15 and 16 denote buffers which output compressed voltage signals VA and VB to a decompression operation circuit composed of NPN transistors 17 and 18, a constant current source 19, a current-voltage conversion circuit 20, and the like.

Here, assuming that the thermal voltage is VT and the reverse saturation current of the diodes 13 and 14 and the transistors 17 and 18 is Is, the symbols V0 and VZ shown in FIG.
VA = VT In (Ia / Is) + VZ = V0 + VT In (Iy / Is) (5) VB = VT In (Ib / Is) + VZ = V0 + VT In (Iy / Is) (6) The following relational expression holds. From the above equations (5) and (6), the relational expression of Ib = (Ia / Ix) .Iy... (7) is derived. From Ia + Ib = I0... (8), Ia = ｛Ix / ( Ix + Iy)｝ I0 (9) Since Ix and Iy are respectively proportional to I1 and I2 in FIG. 2, from the above equations (4) and (9), Ia = (I0 / t) ｛a + (S · f) / l｝ (10), and Ia∝1 / l and Ia∝a hold.

The collector current Ia is output from the AFIC 5 in the current-voltage conversion circuit 20, and is taken in as a digital value by the A / D conversion circuit built in the CPU 7, and the reciprocal 1 / l of the object distance is 1 /l={t.(Ia/I0)-a}.1/S.f (11) However, as shown in FIGS. 1 and 3 in this 1 / l calculation, when the left and right distances are measured, when the focal lengths of the light emitting and receiving lenses 1 and 2 are equal, a in Equation (11) is It is necessary to change to a-α, a + α.

The CPU 7 determines the extension distance of the focusing lens based on the distance information 1 obtained in this manner. The algorithm for this will be described below with reference to the flowchart of FIG.

First, the first distance information lc is measured by the center light projecting spot C, and it is determined whether or not the distance measurement result lc is closer to the short distance comparison value 1N (steps S1 and S1).
2). The short distance comparison value IN is 1 m, which is closer to the near distance than near the normal focal length of 2 m. If the result is closer to 1N, there are two possible ways to determine whether the distance is erroneous due to an out-of-spot or the subject is really close. Therefore, the second determination unit including steps S7 to S11 arranged in the left column in the drawing makes a determination with reference to the second distance information from the right or left second light projecting means.

First, distance measuring light is projected from the right (R) second light projecting means to measure the second distance information lR (step S).
7) If the distance measurement result lR is also shorter than the short distance comparison value 1N (step S8), the center distance measurement result is assumed to be correct, and the distance measurement result l of the center light projection spot C is determined.
The lens is extended according to c (step S1).
2). Even if the second distance information lR based on the right projection spot R is farther than the short distance comparison value lN, the second distance information lL based on the left projection spot L is measured (step S).
9) If the distance measurement result LL indicates a value closer to the short distance comparison value lN (step S10), the distance measurement result by the center light projecting spot C is assumed to be correct, and the distance measurement result is determined according to the center distance measurement result. Focus control is performed (step S12).

As described above with reference to FIG. 1, these lens controls are performed by the CPU 7 by the motor 9 via the motor driver 8, and the right (R) and left (L) I
The CPU 7 switches the RED light projection as well.
The control is performed by controlling the driver 6.

As described above, the center and left or the center and right projected spots are similarly set to the short distance comparison value l.
When outputting data near N or less, this algorithm determines that the spot is not out of the spot, and performs focusing with emphasis on the first distance information lc by the central projection spot.
However, the first distance information lc based on the central light projecting spot C is used.
If only one outputs data near 1N or more, it is considered that the central light projecting spot C is out of the spot and is erroneously measured. Therefore, it is determined that the subject is exactly at the point x2 in FIG. 2A, and focusing is performed according to the distance measurement result lL of the projection spot L obtained in step S9 (step S11). Next, consider a case where the result that the first distance information lc by the central light projecting spot C is far from the long distance comparison value IF is output (step S3).

In this case, it is considered that the hollow phenomenon, which often causes a problem in the conventional auto focus in which only one point can be measured, has occurred. This is a phenomenon in which, for a subject in which two persons are lined up as shown in FIG. 6A, the distance measuring light passes between the two persons and the background is focused. In this case, in the present invention, the left (L) and right (R) distance measuring points are measured as shown in FIG. 6B, and focusing is performed on the closer distance measuring result. This is a general method performed by a conventional multipoint distance measuring apparatus.
In this case, the third determination unit consisting of steps S4 to S6 arranged in the center row in the figure performs the R point ranging (step S4) having the same contents as step S7 and the same determination as step S9. L point ranging (step S5)
After each of these steps, the lens is extended on the basis of the closer distance measurement data of the second distance information lR and lL obtained from each distance measurement (step S6).

Finally, when the first distance information lc by the central light projecting spot C is between the short distance comparison value 1N and the long distance comparison value IF, this is not a spot departure,
It is determined that there is no omission, and the first distance information lc is focused by the first determination unit consisting of step S12 arranged in the left column in the figure (step S12). As described above, when the subject located at the center is near the normal focus, the distance is not measured on the left and right, and the focusing is performed on the first distance information lc, so that the time lag can be suppressed short.

FIG. 7 is a modified example of the flow shown in FIG. 5. The difference between this flow and FIG. 5 is that the second determination unit which determines whether the macro photography or the right spot is out of position is used. That is, the distance measurement of the second distance measurement information lR by the light spot R is stopped, and the flow is made only by the light projection spots C and L. Therefore, in FIG. 7, FIG.
The same step numbers are assigned to the same routines, and the description thereof is omitted, and only different routines will be described.

In FIG. 7, step S3a is the same as step S3 in FIG. 5 described above, except that the direction of the inequality sign is different.
S22 is provided to the third determination unit in the center row, that is, step S12.
Becomes the first determination unit. On the other hand, the left column, that is, step S
9 to S11 correspond to the second determination unit as in FIG. If the first distance information lc is smaller than the short distance comparison value lN in step S2, that is, if the first distance information lc is closer than the predetermined distance range lN to IF, the process immediately proceeds to step S9 without going through steps S7 and S8 in FIG. , S10, S11
Execute The reason for this is that even if the first distance information lc is shorter than the predetermined distance range lN to IF because of a spot departure, this spot departure is as described with reference to FIGS. 10A and 10B. , Which is out of the right spot where the distance is erroneously measured close to, so that I in the second light projecting means which projects light further to the right than the light projecting spot C by the first light projecting means.
This is because there is no need to project light from the RED3R (see FIG. 1).

If it is determined in step S3a that the first distance information lc exceeds the long-distance comparison value IF, the process proceeds to the third determination unit, where steps S5 and S4 are executed, but step S6 in FIG. Are divided into two routines S21 and S22. Note that the first determination unit is exactly the same as in FIG. According to the modification shown in FIG. 7, the second judging unit that judges whether the right spot is out of place or the macro shooting is performed.
Since the distance measurement is not performed, the time lag during macro shooting can be suppressed.

FIG. 8A is a flow chart for determining the lens extension distance of the CPU in a distance measuring apparatus in which the IRED is increased and the third light projecting means is provided outside the first light projecting means and the second light projecting means. The projection spot on the top is shown in FIG. 8B.
It is formed as follows. In the flow shown in FIG. 8A, the first determination unit consisting of step S12 is the same as in FIGS. 5 and 7. In addition, the second determination unit consisting of steps S7a to S11a also replaces the projection spot of the distance measuring light by the second projection unit on the subject from R and L to R1 and L1. It is exactly the same as the flow. Therefore, the description of the first and second determination units is omitted, and the third determination unit after step S31 in step numbers will be described below. Note that the flow of FIG. 8A is similar to that of the second and third light projection spots shown in FIG.
When the distance information is closer to the short distance comparison value N, it is assumed that the macro shooting is performed instead of the spot departure, and the second distance information R1 based on the light projection spot R1 near the center light projection spot C is selected. .

In FIG. 8A, if the first distance information lc from the first light projecting means by the central light projecting spot C is larger than the short distance comparison value 1N (steps S1 and S2), this state indicates that the distance measurement is normal. In addition to the case where the projection is performed, it is conceivable that the light projection spot C is missing in the center or is out of the left spot during macro shooting (see FIGS. 11A and 11B).
Then, proceeding to step S3, the first distance information lc is compared with the long distance comparison value IF, and if it is larger than the comparison value IF,
Because the spot is missing from the left spot in macro shooting or macro shooting,
The process proceeds to the third determination unit following step S31. After step S31, the third determination unit determines the shooting distance by regarding the second distance information lR1, lL1 as the first distance information, and regarding the third distance information lR2, lL2 as the second distance information. ing.

First, the right projection spot R1 from the second projection unit is measured for distance (step S31), and the resulting second distance information lR1 on the right is compared with the short distance comparison value lN (step S32). ). If the second distance information l on the right
If R1 is smaller than the short distance comparison value lN,
Since the right light emitting spot R1 from the second light emitting means is out of the right light spot (see FIGS. 10A and 10B) or macro shooting, the distance of the right light emitting spot R2 from the third light emitting means is measured (step S33). Then, the obtained third distance information lR2 on the right is compared with the short distance comparison value lN (step S).
34). If the third distance information lR2 on the right side is smaller than the short distance comparison value lN, the second distance information lR1 on the right side is also smaller than the short distance comparison value lN (step S3).
2), it is determined that the macro shooting is performed by the light projecting spots R1 and R2, and the photographing lens is extended to the position of the second distance information R1 by the light projecting spot R1 close to the central light projecting spot C (step S35). To end.

Returning to step S34, the third right
If the distance information lR2 is larger than the short distance comparison value lN, this state indicates that the light emitting spot R1 is out of the right spot, or that the light emitting spot R2 is normal, out of the left spot, or missing, so the process proceeds to step S37 and the right Third distance information lR2
Is compared with the long distance comparison value IF. Then, the comparison value IF
If not, the light spot R1 is out of the right spot, or the light spot R2 is in the middle and the left spot is out. Therefore, the process proceeds to step S38, where the right third distance information R2
The lens is extended to the position and the flow ends. On the other hand, the third distance information lR2 on the right is a long distance comparison value IF.
If it is larger, the light spot R1 is out of the right spot or the light spot R2 is normal, so the process proceeds to step S37 described later.

Returning to step S32, the second right
If the distance information lR1 is larger than the short distance comparison value lN, the projection spot lR1 is normal, the left spot is out of place, or the center is missing. Therefore, the right second distance information lR1 is compared with the long distance comparison value IF (step S36) If it is smaller than the comparison value IF, the light projection spot R1 is normal, and the process proceeds to step S35. If it is larger than the comparison value IF, the light projection spot R1 is out of the left spot or one of the voids. The process proceeds to "L1 ranging" in step S31A. Steps S31A to S38A are performed in steps S31 to S3.
8, the projection spots R1 and R2 are replaced with the projection spot L1.
, L2, the letter A is appended to the same step number, and the description is omitted.

In step S36A, the left second distance information l
If L1 is greater than the long distance comparison value IF, the light projection spot L
Since 1 is the left spot missing or missing, "L2 ranging" is performed (step S39), and the resulting third distance information lL2 on the left is compared with the long distance comparison value IF (step S40). If the left third distance information lL2 is greater than the long distance comparison value IF, the position is determined by the first distance information lc, and if it is smaller than the long distance comparison value IF, the position is determined by the left third distance information lL2. Then, each lens is driven to end this flow.

According to the flow of FIG. 8A, five IRs
Since five distance-measuring lights are projected onto the subject using the ED, spot missing or hollowing out is almost completely prevented, thereby improving the distance measuring accuracy.

[0045]

As described above, according to the present invention, even for a subject not located at the center of the photographing screen, it is possible to prevent a dropout and prevent an erroneous distance measurement due to a deviated spotlight. A remarkable effect that the distance can be measured accurately is exhibited.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a camera using a distance measuring apparatus according to an embodiment of the present invention.

2A is a diagram showing a distance measurement result when chart distance measurement is performed, FIG. 2B is a diagram showing an experimental method thereof, and FIG. ), (D)
FIG. 3 is an explanatory diagram of a light projection spot irradiated on a subject.

FIG. 3 is a view showing an optical arrangement of a known one-point distance measuring device using a PSD in a camera using the distance measuring device of the embodiment.

FIG. 4 is a circuit diagram showing a main part of an AFIC in FIG. 1 in a camera using the distance measuring device of the embodiment.

FIG. 5 is a flowchart for determining a lens extension distance of a CPU in FIG. 1 according to a camera using the distance measuring device of the embodiment.

6 (A) and 6 (B) are views for explaining a hollow defect phenomenon in a camera using the distance measuring device of the embodiment. FIG.

FIG. 7 is a flowchart in which a second determination unit in FIG. 5 is simplified according to a camera using the distance measuring device of the embodiment.

8A is a flowchart for determining a lens extension distance of a CPU according to the present embodiment, and FIG. 8B is a layout diagram of a projection spot, according to a camera using the distance measuring device of the embodiment. is there.

9A is a diagram showing a related position of a projection spot on a subject in a conventional distance measuring apparatus, and FIG.
FIG. 4 is a diagram showing a relative position on a PSD of a reflected light spot.

FIG. 10A is a diagram showing a related position of a light projection spot on a subject in a conventional distance measuring apparatus;
(B) is a diagram showing a relative position on the PSD of the reflected light spot.

FIG. 11A is a diagram showing a related position of a light projection spot on a subject in a conventional distance measuring apparatus;
(B) is a diagram showing a relative position on the PSD of the reflected light spot.

[Explanation of symbols]

 3C... IRED (first light emitting means) 3L, 3R... IRED (second light emitting means) 5... AFIC (first to third distance measuring means) 7 CPU. Shooting distance determining means)

Claims (1)

[Claims] 1. A distance measuring device for measuring a plurality of points in a photographing screen, wherein, according to a distance measuring result of a predetermined point in the photographing screen, a distance measuring point other than the predetermined point is next. A distance measuring device having a selection means for selecting a point to be measured.