JP3076166B2 - Camera ranging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring apparatus (multi-autofocus) for a camera capable of measuring a plurality of points on a picture screen.

[0002]

2. Description of the Related Art Conventionally, a camera which can be used for focusing can only measure a distance at one point at the center of a photographing screen. However, such a camera that measures the distance at one point can only photograph a subject that is out of focus, that is, a so-called hollow phenomenon, in a scene where there is no subject at the center of the screen.

[0003] Therefore, a device capable of measuring a plurality of points on a screen has been invented, and various proposals have been made on which of the plurality of points on the photographing screen is to be focused. For example, typical ones are the closest selection described in U.S. Pat. No. 4,470,681 and the like, and the one focusing on the center described in Japanese Patent Application Laid-Open No. 60-233610.

[0004]

However, the subject closest to the screen to be photographed is not always the main subject. That is, according to a simple closest selection,
For example, when trying to photograph a person on the other side of the table, there is a problem that the table is focused and the person who is the main subject is out of focus. On the other hand, if the priority is given to the center, it is considered that the effect of preventing the phenomenon of hollowing out is degraded.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has the effect of preventing focusing on a rough object such as a table or a wall, and also has the effect of preventing a hollowing-out phenomenon and has a reduced side effect of a camera. It is intended to provide a device.

[0006]

That is, the present invention provides a distance measuring means for detecting a subject distance for a plurality of portions in a photographing screen, and a value relating to a variation in the plurality of subject distances measured by the distance measuring means. A calculating means for calculating, a comparing means for comparing the variation calculated by the calculating means with a predetermined value, and a subject distance determining means for determining a subject distance based on a comparison result of the comparing means. Features.

[0007]

In the camera distance measuring apparatus according to the present invention, subject distances are detected by the distance measuring means for a plurality of portions in the photographing screen, and variations in the subject distances measured by the distance measuring means are measured. The value is calculated by the calculation means. The variation calculated by the calculating means and a predetermined value are compared by comparing means. The subject distance is determined by the subject distance determining means based on the comparison result of the comparing means.

[0008]

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

FIG. 1 is a block diagram showing the concept of a first embodiment according to the multipoint distance measuring apparatus of the present invention. In FIG. 1, a center distance measuring section 1 is a means for measuring a distance substantially in the center of a photographic screen, and a peripheral distance measuring section 2 is a means for measuring a distance substantially in a peripheral area of a photographic screen. The outputs of the central distance measuring unit 1 and the peripheral distance measuring unit 2 are supplied to the closest distance selecting unit 3 and the standard deviation calculating unit 4, respectively.

A predetermined value stored in the storage unit 6 is input to the comparison unit 5 together with the calculation result of the standard deviation calculation unit 4. The comparison result of the comparison unit 5 is input to the gate circuit 8 via the inverter 7 together with the output result of the center distance measurement unit 1. On the other hand, the comparison result of the comparison unit 5 and the selection result of the closest selection unit 3 are input to the gate circuit 9. The focus adjustment unit 10 controls the focusing lens 11 according to the output results of the gate circuits 8 and 9. Incidentally, reference numeral 12 denotes a zoom lens.

In such a configuration, the center of the photographic screen is measured by the center distance measuring unit 1 and the peripheral area is measured by the peripheral distance measuring unit 2. Then, the outputs of the central distance measuring section 1 and the peripheral distance measuring section 2 are supplied to the closest distance selecting section 3, and the output indicating the closest distance is selected from the respective outputs of each distance measuring section. Further, the standard deviation calculating section 4 calculates the dispersion of the central distance measuring section 1 and the peripheral distance measuring section 2.

According to the present invention, a distance output for focusing is determined from the output result of each of the distance measuring units in accordance with the output result of the standard deviation calculating unit 4. In the comparison section 5, the output result of the standard deviation calculation section 4 is stored in the storage section 6
Is compared with a predetermined value stored in the. The comparator 5 selects the gate circuit 8 or 9 via the inverter 7. The closest adjustment result is input to the focus adjustment unit 10 in accordance with the variation in the distance, and the output result of the center distance measurement unit 1 is input via the gate circuit 8 or 9. Thereby, the focus adjustment unit 10 controls the focusing lens 11. Here, the concept of determining the focusing distance based on the above-described variation in distance will be described with reference to FIG.

FIG. 2 (a) shows a so-called "missing" scene that the conventional multi-auto focus (AF) is trying to solve. In other words, in a camera that can measure distance only at the center point of the photographing screen 13, even if two people stand as the main subject, it can measure only the scenery between the two persons, and the photograph becomes out of focus. It was a countermeasure against getting lost. In this case, the distance measuring points 14a, 14
The values of b and 14c represent 2 m, ∞ (infinity) and 2 m, respectively.

Conventionally, for such a subject, 3
By selecting the point indicating the shortest distance among the two distance measurement points and setting it as the focusing distance (closest selection), defocusing could be prevented.

However, if the closest selection is always performed, as shown in FIG. 2 (b), the main subject is relatively far away, for example, as in the entrance scene of a bride and groom at a wedding. However, in the situation where a person who originally did not intend to take a picture for the photographer interrupts the camera, the main subject is completely out of focus.

In the present invention, the main subject can be correctly focused in any of the scenes shown in FIGS. 2A and 2B. Is used to determine the focusing distance. In other words, to prevent the scene from being out of focus as shown in FIG. 2B, the scene in which a person stands on the left side of the screen becomes out of focus as shown in FIG. 2C. However, these differences are to be determined based on variations in the distance measurement results.

That is, in FIG. 2B, the distances between the distance measuring points 14a, 14b, and 14c are various values (1).
m, 4m, 5m), it can be seen that the scene is cluttered. In such scenes, there is often something other than the main subject nearby,
It is safer to focus on the center point of the photographing screen 13 than to perform a simple closest selection. In such a situation, the photographer often looks only at the center of the photographing screen.

Conversely, as shown in FIGS. 2A and 2C, in the case of a scene where there is relatively no variation in distance, a good photograph can be taken by using the conventional closest selection.

FIGS. 3 (a) to 3 (f) show typical scenes, and FIG. 4 shows the distance measuring points 14a, 14b and 14c in FIGS. 3 (a) to 3 (f). FIG. 5 is a diagram conceptually showing which of a distance, a medium distance, and a short distance is indicated.

In this embodiment, the closest selection is output in FIGS. 3A, 3B, and 3E with small variations in distance, and the distance is output from short distance to long distance.
As shown in FIGS. 3 (c), 3 (d) and 3 (f), the output of the central distance area is selected for those having a large variation in distance. However, as shown in FIG. 3 (c), for a photograph in which a person is very close in the shooting screen, the landscape is focused on while having almost the same composition as in FIG. 3 (b). In this case, with the closest selection, the landscape cannot be focused. Compositionally, the probability of photographing is lower than in FIG. Therefore, in the case of the scene as shown in FIG. 3C, focusing on the landscape does not lead to a reduction in the focusing rate.

Further, as shown in FIG. 3 (e), in a scene where many people gather in front of the camera and are photographed, the closest selection is adopted. Also, as shown in FIG. 3 (f), for the person on the other side of the table, the center selection is adopted. As a result, a photograph without failure can be taken.

FIG. 5 is a block diagram showing the configuration of a camera distance measuring apparatus according to a second embodiment of the present invention. In this embodiment, a known active triangular distance measuring device is used in which light for distance measurement is projected onto a subject, and the distance to the subject is obtained based on the incident position of the reflected signal light.

The three infrared light emitting diodes (IREDs) 16a, 16b, 1
6c is a CP via drivers 17a, 17b, 17c.
Light emission is controlled by U18. IRED16a, 16
The infrared light from b and 16c is radiated to a subject (not shown) via a light projecting lens 15 and is further reflected by the subject and is reflected via a light receiving lens 19 to a light position detecting element (PS).
D) The light is incident on 20a, 20b, and 20c.

The outputs of the PSDs 20a and 20c are supplied to a differential operation circuit 27 via preamplifiers 21 and 22, compression diodes 23 and 24, and buffer circuits 25 and 26. On the other hand, the output of the PSD 20b is
, 29, compression diodes 30 and 31, and buffer circuits 32 and 33 to a differential operation circuit.
The outputs of these differential operation circuits 27 and 34 are C
It is supplied to PU18.

The CPU 18 controls a focusing lens 36 via a focus adjustment unit 35. Also, 37
Is a zoom lens, and the zoom position is input to the CPU 18 via the zoom encoder 38.

In the multi-point distance measuring device having such a configuration,
IRED 16a, 16b, 16c with three infrared light for distance measurement
And is projected through the light projecting lens 15 to different points in the photographic screen. This distance measuring light is reflected on the subject, collected by the light receiving lens 19,
The light is incident on the PSDs 20a, 20b, and 20c. The subject distance can be obtained from the incident position of the reflected signal light on the PSD according to the known principle of triangulation.

[0027] The PSD20a, 20b, 20c, as shown in FIG. 6, the position of the signal light and outputs two current signals i _a, a i _b. This i _a, i _b is the number 1
And the relational expression of Expression 2 below.

[0028]

(Equation 1)

[0029]

(Equation 2)

Here, i _p0 is the total signal light current. Further, from the relationship of m + n = tt = PSD length, the relational expression of Expression 3 is established.

[0031]

(Equation 3)

[0032] Since this m is the light incident position, than it t is a constant, by calculating a _{i a / (i a + i} b), can be calculated the incident position m of the reflected signal light, the object distance therefrom Can be obtained.

The output current i _a, i _b of the PSD is amplified by a preamplifier 21 and 21 or the preamplifier 28 and 29, is poured into the compression diodes 23 and 24 or 30 and 31,. Buffer circuits 25, 26, 32,
33 denotes the compression diodes 23, 24, 30, 3
The _Vref reference potential of 1 is input to the differential operation circuits 27 and 34.

The differential operation circuits 27 and 34 have a configuration as shown in FIG. In the figure, the common emitters of the pair of NPN transistors 39 and 40, the current source 41 of a current value I ₀ is connected. Also,
The resistor 42 is connected to the collector of the transistor 40. The collector currents of the transistors 39 and 40 are I ₁ and I ₂ , respectively. Assuming that the amplification factor of the preamplifier is β, the output potentials V _A and V _B of the compression diode are
It is obtained by the relational expressions of Expressions 4 and 5.

[0035]

(Equation 4)

[0036]

(Equation 5) Here, I _S is the reverse saturation current of the diode, the V _T is the thermal voltage. From the similar expressions, the relational expression of Expression 6 and the expression of Expression 7 hold for I ₁ and I ₂ and V _A and V _B.

[0037]

(Equation 6)

[0038]

(Equation 7) On the other hand, since i ₁ + i ₂ = i ₀ , the relational expression of Expression 8 and the relational expression of Expression 9 are further obtained.

[0039]

(Equation 8)

[0040]

(Equation 9) Therefore, the value r obtained by converting the current i ₂ into a voltage by the resistor 42
i ₂ is obtained by the relational expression of Expression 10.

[0041]

(Equation 10) That is, since r, i ₀ , and t are determined values,
The incident position m of the signal light to the PSD can be obtained from i ₂ .

Returning to FIG. 5, the light emitting / receiving lenses 15, 19
And the IRBD 16b and its driver 17b, PSD2
1b, the preamplifiers 28 and 29, the diodes 30 and 31, the buffer circuits 32 and 33, and the differential operation circuit 34 form the central distance measuring section 1 in FIG. In addition, lenses 15 and 19 for projecting and receiving light, IREDs 16a and 16c for measuring distance between left and right, and drivers 17a and
7c, PSDs 20a and 20c, preamplifiers 21 and 22,
The diodes 23 and 24, the buffer circuits 25 and 26, and the differential operation circuit 27 correspond to the peripheral distance measuring unit 2 in FIG.

Here, the reason why the PSD is separated left and right but the pre-amplifier and the following are common is that the IRED emits light independently and can be shared. However, since the one for center distance measurement is used frequently, in consideration of the improvement of accuracy,
Separated from the preamplifier. This is because if the area of the PSD increases, the influence of disturbance increases, and the S / N deteriorates.

The CPU 18 A / D converts the output signal voltages of these distance measuring units with a built-in A / D converter and inputs them. The result is used for focusing control by a predetermined algorithm, and the focusing lens 36 is controlled via the focus adjustment unit 35. Note that the zoom position of the zoom lens 37 is input to the CPU 18 via the zoom encoder 38. Next, the above-described predetermined algorithm will be described with reference to the flowchart of FIG.

First, in each of steps S1, S2, and S3, the CPU 18 causes the drivers 17b, 17a, 1
The IREDs 16b, 16a, and 16c sequentially emit light via 7c. Each time, the CPU 18 inputs ri ₂ shown in FIG. 5 and based on the ri ₂ , the respective subject distances L _b , L _b
a and _Lc are determined. Here, the reciprocal is obtained for the following reason.

First, as shown in FIG. 9, the reciprocal of the distance (1 / L) and the focus position of the photographing lens are substantially proportional to each other. Step S4
In the above, these variations are calculated, but also by using the reciprocal of the distance, sensitive weighting can be performed on a short-range rough subject.

Also, the output result of the triangular distance itself is output in principle in proportion to 1 / L instead of L. Therefore, it is better to calculate the variation in step S4 while keeping the reciprocal of L. Be simple. Here, the standard deviation σ is adopted as a quantity representing the variation, but this is calculated in a form as shown in the relational expression of Expression 11.

[0048]

[Equation 11]

However, since the magnitudes can be compared without dividing by 3 or the square root, which is the number of distance measuring points, there is no need to strictly calculate the relational expression of Equation 11.

Next, in step S5, a judgment is made according to this result. If the variation σ is larger than the predetermined amount σ ₀ , the process proceeds to step S6, and the center distance measurement result 1 /
_Lb is selected. On the other hand, if it is smaller than σ ₀ , the process proceeds to step S7, and the closest distance from 1 / L _a , 1 / L _b and 1 / L _c is selected.

Here, the predetermined value σ ₀ for comparison is calculated as shown in FIG.
To determine. In FIG. 2A, σ is L _a , L _b ,
Respectively L _c 2m, When ∞, becomes 0.235. Also, L _a , L _b , and L _{c in} FIG.
Then, σ becomes 0.365. Therefore, if σ _{0 is set} to about 0.35, the closest selection is selected in FIG. 2A, and the center is selected in FIG. 2B. Further, FIG.
Is, L _a, L _b, and L _c 2m, ∞, When ∞, sigma =
It becomes 0.235. Therefore, the process branches from step S5 to step S7, and the closest selection is adopted, so that a photograph without a dropout is obtained.

FIG. 10 is a flowchart for explaining the operation of the third embodiment of the present invention. This is the same as the second embodiment except that a step S8 is added between step S3 and step S4 in the flowchart of FIG. 8 that takes into account the focal length of the photographic lens of the camera. That is, in this step S8, the zooming position is read from the zoom encoder 38 shown in FIG. 5 every time the photographing is performed, and the same selecting method as in the flowchart of FIG. Things.

On the other hand, on the short focus side, the closest selection is simply performed. This is apparent from FIG. That is, in a distance measuring device that measures a predetermined distance measuring point,
As shown in FIG. 11A, when the angle of view of the photographing lens of the camera changes between the telephoto (Tele) side and the wide angle (Wide) side, the distance measurement position in the photographing screen is changed as shown in FIG. It changes as shown in (c). At this time, on the short focal length side, the distance measurement point is located at the center of the photographing screen as shown in FIG. Note that the other steps are the same as those in the flowchart of FIG. 8 of the second embodiment described above, and thus the same step numbers are assigned and the description is omitted.

FIG. 12 is a flowchart for explaining the operation of the fourth embodiment of the present invention. This is obtained by replacing step S6 in the flowchart of FIG. 10 according to the third embodiment with step S9.

As shown in FIG. 13, the relationship between the photographing magnification and the probability of a photograph being taken indicates that the main subject is f ×
It can be seen that the probability of shooting between 1/50 and f × 1/80 is high. Therefore, in the step S9, focusing is performed with priority given to the object having this distance.

That is, also in the fourth embodiment, the side effect of the multi-AF is considered to occur only when the angle of view of the photographing lens is small, as in the flow chart of FIG. 10. Therefore, only when the focal length of the photographing lens is long. , The variation determination in step S5 is performed.

In this embodiment, when the variation in the subject distance is large in step S5, the process proceeds to step S6,
Among them, the one whose photographing magnification is closest to f × 1/70, that is, the one whose distance is close to 70 × f, is selected. For example, for a 50 mm lens, 50 × 70 =
The closest distance to 3500mm = 3.5m, L _a,
L _b, selected from L _c, may, combined focus there.

[0058]

As described above, according to the present invention, when shooting a scene including a lot of cluttered subjects, such as a party venue or a car, the subject in the center of the shooting screen is focused. To provide a practical camera distance measuring device that can prevent focusing on a rough subject such as a wall and can correctly focus on a main subject, has an effect of preventing a dropout phenomenon, and has no side effects. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a concept of a first embodiment according to a camera distance measuring apparatus of the present invention.

FIGS. 2A to 2C are diagrams illustrating an example of a composition of a camera with respect to a subject.

FIGS. 3A to 3F are diagrams showing typical scenes.

FIG. 4 shows distance measuring points 14 in FIGS. 3 (a) to 3 (f).
FIG. 4 is a diagram conceptually showing which of a, 14b, and 14c indicates a long distance, a medium distance, and a short distance.

FIG. 5 is a block diagram showing a configuration of a camera distance measuring apparatus according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating the PSD of FIG. 5;

FIG. 7 is a circuit diagram showing a configuration of the differential operation circuit of FIG. 6;

FIG. 8 is a flowchart illustrating the operation of the second embodiment.

FIG. 9 is a diagram showing a relationship between a reciprocal (1 / L) of a distance and a focus position of a photographing lens.

FIG. 10 is a flowchart illustrating the operation of the third embodiment of the present invention.

11A is a diagram illustrating an angle of view of a photographing lens of a camera, FIG. 11B is a diagram illustrating a ranging position in a shooting screen when the angle of view is on the telephoto side, and FIG. FIG. 7 is a diagram showing a distance measurement position in a shooting screen when is on the wide angle side.

FIG. 12 is a flowchart illustrating the operation of the fourth embodiment of the present invention.

FIG. 13 is a diagram illustrating a relationship between a photographing magnification and a distribution probability of a subject.

[Explanation of symbols]

Reference numeral 1 denotes a central distance measuring unit, 2 denotes a peripheral distance measuring unit, 3 denotes a closest selecting unit,
4 standard deviation calculation section, 5 comparison section, 6 storage section, 7 inverter, 8, 9 gate circuit, 10 focus adjustment section,
11, 36: Focusing lens, 12, 37: Zoom lens, 13: Screen, 14a, 14b, 14c: Distance measuring point, 15: Light emitting lens, 16a, 16b, 16
c: Infrared light emitting diode (IRED), 17a, 17
b, 17c: driver, 18: CPU, 19: light receiving lens, 20a, 20b, 20c: light position detecting element (PS
D), 21, 22, 28, 29 ... preamplifiers, 23, 2
4, 30, 31 ... compression diode, 25, 26, 32,
33: buffer circuit, 27, 34: differential operation circuit, 35
... focus adjustment unit, 38 ... zoom encoder.

Claims (1)

(57) [Claims] 1. A distance measuring means for detecting a subject distance for a plurality of portions in a photographing screen; a calculating means for calculating a value relating to a variation in a plurality of subject distances measured by the distance measuring means; A distance measuring device for a camera, comprising: comparing means for comparing the variation calculated by the above with a predetermined value; and subject distance determining means for determining a subject distance based on a comparison result of the comparing means.