JP2882627B2 - Camera multipoint 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 camera multipoint distance measuring device,
More specifically, a so-called active camera, which projects light for distance measurement from a plurality of light emitting elements toward a subject and automatically measures the distance to the subject by receiving reflected light from the subject. The present invention relates to a multipoint distance measuring device.

[0002]

2. Description of the Related Art As is well known, an active type auto focus (hereinafter abbreviated as AF) device is widely used, and many lens shutter cameras are of this type.
Equipped with F device.

[0003] However, many AFs of this type have been used so far.
In the camera, one infrared light diode (hereinafter, IRED)
Since the AF operation is performed by the abbreviation, the distance can be measured only to a certain point irradiated with the projection light from the diode. Therefore, in the composition to be photographed, if the main subject does not exist at the position where the optical signal for distance measurement is projected, the AF device may use another subject or background,
In other words, the camera focuses on (1), and the main subject is out of focus.

In order to eliminate this problem, an AF device which projects the infrared light onto three points on a screen where a picture is to be taken to thereby prevent the hollowing out has been developed.
JP-A-58-9013 and JP-A-58-93040
No., proposed by US Pat.

As shown in FIGS. 6A and 6B, the proposed multi-point distance measuring device uses a well-known position detecting light receiving device made of a semiconductor to receive infrared light emitted from a plurality of IREDs. The light is received by a light receiving element such as an element (hereinafter abbreviated as PSD), and in FIG.
The infrared light emitted from each of the IREDs 31a, 31b, 31c is collected by the light projecting lens 35 and projected toward the subject 37. The reflected light reflected from the subject 37 is
An image is separately formed on the PSDs 32a, 32b, and 32c by the light receiving lens 36, so that multi-point distance measurement is performed. Also, the one shown in FIG.
Instead of the three PSDs 32a, 32b, 32c, one
The image is formed on a plurality of large PSDs.

By arranging the light emitting element and the light receiving element in this way, as shown in FIG.
(Light-emitting diodes) Light emitted from the light-emitting diodes 38a, 38b, and 38c is condensed by the light projecting lens 35 and is projected toward the subject, so that three points on the subject can be measured.
Therefore, when photographing the subject 40 having the composition shown in FIG. 8, a normal AF device that measures the distance at one point only with the center frame 39 at the center will be hollow, but as shown in FIG. According to the AF device of three-point distance measurement, it is possible to prevent this hollowing out and to accurately measure the distance.

Here, the basic principle of a triangulation type active distance measuring apparatus using one PSD will be described with reference to FIG. In FIG. 9, the optical axis of the light receiving lens 42 is PSD
44, the light is projected from the IRED 43 to the subject 45 at the subject distance D via the light projecting lens 41, and the incident position of the reflected light reflected by the subject 45 Is x, the distance between the light projecting lens 41 and the light receiving lens 42, that is, the base line length is S, and the light receiving lens 4
Assuming that the focal length of No. 2 is f and the length of the PSD 44 is t, the following relationship is obtained: x = S · f / D (1)

Accordingly, the object distance D is obtained by obtaining the reflected light incident position x. PSD44 Since outputs two signal currents I _1, I ₂ in accordance with the reflected light incident position x, the current I _1, I ₂ is the total light current and I _0, respectively, I ₁ = {( t / 2) + x｝ · I ₀ / t I ₂ = {(t / 2) −x｝ · I ₀ / t Therefore, if the ratio of the signal currents I ₁ and I ₂ is calculated, the total light current I _0, which is a function of the reflectance of the object, disappears, and I ₁ / I ₂ = (t + 2x) / (t−2x). Therefore, x = t · {(1/2) −I ₂ / (I ₁ + I ₂ )}.

By substituting equation (1) into the above equation, D = (S · f / t) / ｛(1/2) −I ₂ / (I ₁ + I
₂ )｝, the photocurrent ratio I ₂ / (I ₁ +
When I ₂ ) is obtained, the subject distance D is obtained. Therefore, the PSD and IRED having the configuration shown in FIG.
Fig. 6 (A) above prepared three pairs each.
It is a method of.

[0010]

However, in the multipoint distance measuring means of FIG. 6A configured as described above,
Three PSDs are required. Also, as shown in FIG.
If an attempt is made to use only one PSD by increasing the area of the PSD, the influence of external light noise increases as much as the light receiving area of the PSD increases, and the distance measurement accuracy at a long distance deteriorates remarkably. Would.

Therefore, a multipoint distance measuring device having an arrangement as shown in FIG. 10 can be considered. In this multipoint distance measuring device, 3
The infrared light emitted from each of the IREDs 53a, 53b, 53c is condensed by the light projecting lens 51 and projected on the distance measurement target points 55a, 55b, 55c of the subject 55, respectively. Then, the reflected lights 56a, 56b, 56c reflected at the same distance measurement target points 55a, 55b, 55c are imaged on one side of the PSD 54 by the light receiving lens 52, respectively. In the multi-point distance measuring apparatus shown in FIG. 10 configured as described above, the PSD 54 can use a conventional PSD for one-point distance measurement, can use a common operation IC, and can reduce external light noise. The impact is the same as before,
There is no risk of deteriorating the ranging accuracy.

However, if the length of the PSD 54 is not sufficiently long, the IRE for measuring the distance measuring point 55c on the left side is used.
The signal light 56c due to the D53c deviates from the PSD 54 and the distance cannot be measured. As a result, the distance measurement range is reduced. Therefore, if the ranging accuracy and the ranging range are to be made the same for each ranging point, a light receiving element is required for each ranging point, and there is a disadvantage that the device becomes large.

In view of the above circumstances, the present invention provides a high-accuracy distance measuring device as a whole without increasing the size of the device.
It is another object of the present invention to provide a multi-point distance measuring device for a camera having a wide distance measuring range.

[0014]

SUMMARY OF THE INVENTION A multi-point distance measuring apparatus for a camera according to the present invention is designed to measure the distance at the center of a screen.
Distance measuring means and a distance measuring part of the periphery of the screen
The second distance measuring means, and the first and second distance measuring means.
Determines the distance to the main subject based on the output of the distance measuring means
In the camera multi-point distance measuring device provided with a distance determining means , the second distance measuring means is different from the first distance measuring means.
Distance measurement accuracy is low, but the distance range that can be measured is wide
On the short distance side than the predetermined distance
Determines the distance of the main subject from the output of the second distance measuring means
Characterized in that it.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing an optical arrangement of a multi-point distance measuring device of a camera showing one embodiment of the present invention. The multi-point distance measuring device includes a light projecting lens 1b and an IRED 3b, and a first light projecting means 47 constituting a first distance measuring means for central distance measuring that projects light in the optical axis direction of the photographing lens; Projection lens 1a and IR
A second light projecting means 48, which comprises EDs 3a and 3c and constitutes a second distance measuring means for projecting light in a direction other than the optical axis, for left and right distance measurement, a light receiving lens 2 and a PSD 4, and reflected light from a subject Means for generating output currents I ₁ and I ₂ according to the light receiving position of the photoelectric conversion means 49, which constitutes a distance measuring means.
And a calculating means 11 for calculating the subject distance D based on the output currents I ₁ and I ₂ from the photoelectric conversion means, and which constitutes a distance measuring means, constitute a main part thereof.

The optical axis of the light-receiving lens 2 of the photoelectric conversion means 49 is made coincident with the center line of the PSD 4 disposed behind the lens 2 and at a position separated by the focal length f of the lens 2. When the origin is set as the origin, the projection light from the first light projecting means 47 is reflected at the distance measurement target point 10b of the subject to become reflected light 29b, and is imaged at the position _xb on the PSD 4. Similarly, distances Δa, Δb are provided to the left and right of the optical axis of the lens 1a behind the light projecting lens 1a of the second light projecting means 48.
The projection light from the IREDs 3c, 3a shifted only by this is reflected at the distance measurement target points 10c, 10a of the subject to become reflected light 29c, 29a, and is imaged at positions x _c , x _a on the PSD 4, respectively. You.

FIG. 2 is a diagram showing an example of the configuration of the arithmetic means 11 . Signal current I _1, I ₂ output from PSD4 is supplied to the A F for IC6 that converts the same signal current to the distance signal. The AF IC 6 sends a timing pulse to the CPU 5 together with the distance signal.

The CPU 5 controls the sequence of the entire camera. In addition, a built-in distance determination unit is used, and at the time of three-point distance measurement, three distance measurement data having a high possibility that a main subject is present are calculated, and the closest data is selected from them. Based on the distance measurement data, the CPU 5 drives a motor 9 for extending the photographing lens via a driver 8 .

Next, the operation of the AF IC 6 will be described with reference to FIG.
4 and a timing chart of the AF operation shown in FIG. With this as a basic operation, the CPU 5 operates the IREDs 3a, 3b, 3
By repeating this basic operation three times while selecting c, three pieces of AF data are loaded into the CPU 5 in a time-division manner.

In the basic AF operation, the AF IC 6 is
It is started by receiving the AF start signal and the basic clock signal. Each of the IREDs 3a, 3b and 3c is oscillated by an oscillator 25, and is driven by a pulse signal a having a duty ratio of 50% at 16 KHz, for example, according to an IRED timing circuit 26 to start pulse emission. Then, output voltages V ₁ , of current-voltage conversion circuits 12, 13 supplied with photocurrents I ₁ , I ₂ from PSD 4 that received the subject light,
V ₂ has a waveform as shown in FIG.

The ratio between the peak values of the _two voltage waveforms V ₁ and V ₂ is equal to the aforementioned photocurrent ratio I ₁ / I ₂ . Also, A
Upon receiving the F start signal, the channel switching circuit 20, the positive integration number counter 22, and the total integration number counter 23 are reset. Therefore, since the channel switching signal d from the channel switching circuit 20 is at the "L" level, the channel switching switch 14 is turned off, and the switch 15 is turned on by the switching signal d whose phase has been inverted by the inverter 27 to the "H" level. Therefore, a voltage V ₂ proportional to the photocurrent I ₂ is applied to the BP • F 16.

Therefore, first, when the timing pulse e is sent from the integration timing pulse circuit 30 at the timing when it becomes "H" level substantially at the center of the "H" level of the drive pulse signal a as shown in FIG. 17 is turned on. At this time, the output of the BP / F 16 outputs a voltage proportional to the photocurrent I ₂ because the switch 15 is turned on.

Therefore, the integral output V _I of the integrator 18 is B
Since the integration is performed at the positive peak b ₁ of the filter output signal b of the P · F 16, the integration changes in the negative direction, that is, changes as the inversely integrated VI _−1. Voltage V
It repeats until it falls below ref. When the integrated output V _I becomes lower than the reference voltage Vref, the comparator - comparison output c of the capacitor 19 becomes the "L" level → "H" level, the channel switching signal d from the channel switching circuit 20, the fall of the timing pulse e e "L" level in synchronization with ₁ →
Since it is at the “H” level, the channel switch 14 is turned on and the switch 15 is turned off. The photocurrent I in place of the photocurrent I ₂ in B · P · F16
_At this time, the integration timing pulse circuit 30 outputs the timing signal e as the timing pulse e.
Compared to when the channel switch 15 is on, the IR
Outputs a timing pulse e ₂ which is delayed a half cycle of the frequency of the ED drive pulse signal a.

[0024] Thus, B · P negative peak of the filter output signal b output from · F16 - for integration with click b ₂ is performed, in turn, integrated in the positive direction, i.e., positive integration is performed. Thus, each time the integrated output V _I exceeds the reference voltage Vref, a signal proportional to the photocurrent I _1, I ₂ in a direction approaching to the reference voltage Vref is integrated in opposite directions.

Assuming that the total number of integrations is N ₀ , the relationship between the number of positive integrations N _S and the number of inverse integrations _NG is N ₀ = N _S + N _G (3). The relationship between the number of positive integrations N _S and the total number of integrations N ₀ is as follows: N _S = {I ₂ / (I ₁ + I ₂ )} · N ₀ (4) The (4) above in Equation (2) Substituting equation _{N S = {(1/2) -S} · f / D · t} · N 0 ...... (5).

Accordingly, the total number of integrations N0 counted by the total integration number counter 23 is always kept constant by the termination circuit 24. Therefore, the positive integration number counted by the positive integration number counter 22 via the AND gate 21. object distance D is calculated from the integral number N _S.

In the multi-point distance measuring apparatus thus constructed, the total length of the PSD 4 is t, the base length between the first light projecting means 47 and the photoelectric conversion means 49 is S, and the focal length of the light receiving lens 2 is f. When the center of the PSD 4 in the length direction is coincident with the optical axis of the light receiving lens, the limit value (hereinafter, abbreviated as the close limit) Dminb of the close-side object distance that can be measured by the first light projecting means is Dminb = 2 · S · f / t That is, if the base line length S is reduced, the closest limit D
Since the minb becomes smaller, the distance can be measured even closer.

Therefore, as shown in FIG.
The light projecting lens 1b for condensing the light projected from the D3b and the light projecting lens 1a for condensing the light projected from the left and right distance measuring IREDs 3a and 3c are separated from each other. _1, the S _2, the base length S ₁ is set equal to the base length S of the conventional example, disposing the second light projecting means for the right and left distance measurement such that S _1> S _2. As a result, the accuracy of distance measurement by the first light projecting means for central distance measurement is realized as before.

On the other hand , the AF accuracy by the second light projecting means 48 is inferior to the AF accuracy by the first light projecting means 47, but at a short distance, the signal light is sufficiently strong, so that it is not at a level that poses a practical problem. Incidentally, the projected As apparent from the left ranging IRED3c from the figure, the imaging point x _c on PSD4 by reflected light reflected 29c by the object 10c is first
The light will deviate from the PSD 4 earlier than the image forming point _xb by the light projecting means 47.

The incident position x _c of the reflected light 29c on the PSD 4
Since IRED3c from the optical axis of the projection lens 1a is disposed shifted by .DELTA.a, a _{x c = (S 2 · f} / D) + Δa when the focal length of the light projecting and receiving lenses are equal. Thus, near the limit Dminc becomes _{Dminc = S 2 · f / {} (t / 2) -Δa)}.

By substituting f = 16 mm S ₂ = 31 mm t = 2 mm Δa = 0.5 mm as a practical numerical value in the above equation, the closest limit Dminc becomes approximately 1 m, and the same limit is obtained up to a short distance that does not hinder practical use. It can be seen that the distance can be measured by all the IREDs 3a, 3b, 3c using the PSD 4.

The IRED 3c of the second light projecting means shown in FIG.
Ranging light projected from the camera and the IRED of the first projecting means
Point P at which the center ranging ray projected from 3b crosses
_{Since c} is 38.4 cm according to the above numerical value, three points can be measured without fail in the practical use range of the camera.

[0033] When the relationship between the reciprocal of the distance measurement data N _S and the object distance D obtained by such a multi-point distance measuring device on the graph is as shown in FIG. IRED3 for center distance measurement
b is, since the position on the optical axis of the projection lens 1b, when the signal is sufficiently large, ranging data N _S by the IRED3b the near end is a straight line A ₁ of Dminb according (5).

IREDs 3a and 3c for left and right distance measurement
Is, [Delta] b from the optical axis of the projection lens 1a, is arranged at a position shifted to the left and right .DELTA.a, also the base length S ₂ S
Since less than _1, the IRED3a, distance measurement data N _S by the 3c, inclined loosely still and shifts up and down from the theory of center AF, Dmina closest end, respectively, a straight line A ₂ of Dminc, A ₃ Becomes Further, in the beyond than the object distance D _x which received signal is weak, the integrator 18 shown in FIG. 3, by the action of the adjusted offset voltage, forces,
Since it is designed so that the total number of integrations becomes N ₀ , FIG.
As shown in, the object distance D _x onward, nonlinear distance measurement data N _S converges to total integral number N ₀ rises.

[0035] Therefore, in this multi-point distance measuring device, the multi-point distance measurement is carried out, but the object distance is limited to between the Dminc to D _x, the object distance D _x is 5m beyond, Since the subject distance Dminc is around 1 m as described above, it can be used without any practical problems.

The short distance area closer to the object distance Dminc is a so-called macro area. In this area, even if the left and right distance measuring IREDs 3a and 3c are projected at a certain angle, the area on the object is not affected. Since the distance between the distance measurement target points is small, even if the multipoint distance measurement effect cannot be obtained, there is no problem in use.
In other words, any IRE of the IREDs 3a, 3b, 3c
This means that even if D emits light, the projection light is likely to hit the subject. Therefore, the macro AF can be realized continuously without mechanical switching by reading the data of the right distance measuring IRED 3a capable of measuring the distance to the closest distance.

Generally, portrait photography is performed between 2 and 3 m, and subjects farther than that are likely to be landscapes. Therefore, IRED3b base length S ₁ is the left and right distance measuring IRED3a for the central distance measurement, 3c base length S of
Since the distance is set to be larger than ₂ , the distance measurement accuracy at a long distance is improved, and an AF camera excellent in the descriptive power of scenery can be realized.

As described above, according to the embodiment of the present invention, the object distance is reduced to about 5 by the right ranging IRED 3a.
The distance can be measured as close as possible to 0 cm. Between 1 m and 2 to 3 m, multi-point distance measurement is performed. Further, at a distance of 4 to 5 m or more, a long-distance subject such as a landscape can be accurately measured by the data of the central distance measuring IRED 3b. That is, AF with a wide ranging range and high ranging accuracy can be realized.

Further, the conventional PSD for one-point distance measurement is used as the PSD.
Since the SD can be used, the influence of external light noise is smaller than in the conventional multi-point distance measurement, which is almost the same as the one-point distance measurement. Furthermore, since the conventional circuit can be used as it is as the processing circuit, various remarkable effects such as an advantage in cost are exhibited.

[0040]

According to the multi-point distance measuring apparatus for a camera according to the first aspect of the present invention, without increasing the size, the camera as a whole is highly accurate and has a wide distance measuring range. Can be provided.

[0041]

[0042]

[Brief description of the drawings]

FIG. 1 is an arrangement diagram of an optical system, a light projecting unit, and a photoelectric conversion unit in a multipoint distance measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a configuration of a calculating means in the multipoint distance measuring apparatus of FIG. 1;

FIG. 3 is a block circuit diagram of the AF IC in FIG. 2;

FIG. 4 is a timing chart showing waveforms at various parts in FIG. 3;

[5] diagram showing a relationship reciprocal of object distance D of the distance data N _S obtained above examples.

6A and 6B are layout diagrams of a distance measuring optical system in a conventional multi-point distance measuring apparatus. FIG. 6A shows a case where three PSDs are used as light receiving elements, and FIG. 6B shows one PSD. The figure which shows the case where each is used.

FIG. 7 is a diagram showing an example of light projecting means in a conventional multipoint distance measuring apparatus.

FIG. 8 is a front view showing an example of a photographed image frame.

FIG. 9 is a layout diagram of a distance measuring optical system for explaining a conventional active triangulation.

FIG. 10 is an arrangement diagram of a distance measuring optical system in a conventional multipoint distance measuring apparatus.

[Explanation of symbols]

 5 CPU (distance determining means) 11 arithmetic means (first and second distance measuring means) 47 first light emitting means (first distance measuring means) 48 second light emitting means ( (Second distance measuring means) 49 ... photoelectric conversion means (first and second distance measuring means)

Claims (1)

(57) [Claims] 1. a) Distance measurement is performed at a central portion of a screen.
The first distance measuring means and the peripheral area of the screen are measured.
Second distance measuring means, and the first and second distance measuring means
To determine the distance to the main subject based on the output of
The multi-point distance measuring device for a camera comprising a determination unit, b) the second distance measuring means, than the first distance measuring means
Although the ranging accuracy is low, the range of distance that can be measured should be wide
Configured to, c) in the near side of the predetermined distance, measured in the second
A multi-point distance measuring device for a camera, wherein a distance of a main subject is determined by an output of a distance means .