JP3091279B2 - Multi-beam autofocus controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam auto-focus control apparatus, and more particularly to the contents of auto-focus control for performing a distance measurement process using a plurality of beams in a camera.

[0002]

2. Description of the Related Art In a camera, auto focus control is performed. In this auto focus control, for example, a multi-beam is projected from a light projecting section to a subject, and a beam reflected from the subject is received by a light receiving section. It is performed by That is, as shown in FIG. 9, a lens barrel 4 holding a finder 2 and a lens 3 is arranged on the front surface of the camera body 1. Section (infrared light emitting diode) 5 and light receiving section 6
Are arranged side by side in the horizontal direction. The light projecting unit 5 and the light receiving unit 6 measure the subject distance (ranging) and output the number of auto focus (AF) stages as shown in FIG.

In FIG. 10 (a), when a beam is projected on an object at different distances P1 and P2 from the light projecting unit 5, a reflected beam from the object is received by a light receiving lens 6a in a light receiving unit 6.
Through the light receiving element 6b. At this time, in the light receiving element 6b, the reflected beam from the subject at the distance P1 is positioned at the position p1 in the base line length direction connecting the light projecting unit 5 and the light receiving unit 6.
Since the reflected beam from the subject at the distance P2 is received at the position p2, the subject distance is measured based on the position of the received beam. This light receiving element 6b has a structure shown in FIG.
As shown in the figure, the number of AF stages for autofocus control corresponding to the subject distance is assigned. First, the center of gravity 200 of the received beam (dotted line) 100 is detected, and this detected value is used as distance measurement information. When output from the light receiving element 6b, the number of AF stages is determined based on the distance measurement information. In this case, from the light projecting unit 5, three beams having different light projecting positions are sequentially output toward the subject 7 in order to secure the distance measurement as shown in FIG. The number of AF stages is output based on the AF stage number information. By driving the lens based on the AF stage number information, the subject 7 is focused.

[0004]

However, in the conventional multi-beam autofocus control, FIG.
As shown in FIG.
In the case where the beam does not completely hit and the beam returns in the direction of the base line connecting the light projecting unit 5 and the light receiving unit 6, there is a problem that the position of the center of gravity of the beam changes and erroneous distance measurement occurs. there were. That is, as shown in FIG. 10 (b), when the beam 100 is a perfect circle (dashed line), the center of gravity is at the position 200, whereas the beam 101 is a semicircle.
In the case of (solid line), the position of the center of gravity is shifted to the position of 201. Accordingly, although the number of AF stages to be output must be n, the number of AF stages of n-1 is actually output, and autofocus control becomes inaccurate.

FIG. 12 shows the output state of the number of AF stages when one beam is projected and the camera is swung by a predetermined angle. FIG. 13 shows the number of AF stages when three beams are projected. The output state is shown. In the above figure, the portion A shown in the drawing is in a state where there is no beam chipping, and the portion B where the number of AF stages is small (the distance is short) corresponds to the case of the beam 101 in FIG. A (light projection circle is turned left and right by the light projection lens).
Portion C where the number of F stages is large (the distance is long) is a case where the right side of the beam is missing. Therefore, the illustrated B and C portions where the beam is missing are NG regions where the focus is out of focus. The above is not a problem at a distant distance where only one beam can be projected on the subject 7 as shown in FIG. 11B. However, as shown in FIG. This is a problem when the subject 7 is at a short distance so as to hit the subject 7.
That is, when there are two or more beam outputs, the smaller number of AF stages that have been output is conventionally selected, and especially when the left beam is missing, FIG.
The focus is controlled by the number of AF stages in the NG area shown by B in FIG.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a multi-beam auto-focus control device capable of eliminating erroneous distance measurement due to lack of a beam and performing accurate focus control.

[0007]

To achieve the above object, the invention according to claim 1 measures all of the multi-beams.
A light projecting portion for projecting the object into距毎, in the multibeam autofocus control device for a camera having a light receiving portion, a for receiving the reflected beam from the object to output the distance measurement information by the light receiving position, the light receiving Check whether all beams received by the unit are missing or not.
A beam missing determining means for determining a beam is provided, and based on the output of the beam missing determining means, a beam having no or few beams in a base line length direction connecting the light projecting unit and the light receiving unit is selected. It is characterized in that auto focus control is performed based on distance measurement information. In the above description, the beam with the least beam missing selected for the focus control means that, for example, both of the received two beams may be missing, and means the beam with the smallest missing amount at that time.

[0008]

According to the above arrangement, the beam missing determining means determines whether or not each of the received beams has a beam missing based on the light quantity of each beam. It is measured by the time (number of times of light emission) or the light amount value per predetermined time. In this case, since the reflected light amount is small for a beam having a missing beam, for example, when measuring the beam light amount, it takes time to reach the predetermined light amount. Therefore, a beam having a predetermined light amount in the shortest time in the multi-beam is specifically selected as a beam having no (or little) beam missing. Then, the distance measurement information of the beam having no beam missing, for example, the number of AF stages corresponding to the distance measurement value is output, and the lens drive for autofocus is performed based on the number of AF stages.

[0009]

FIG. 1 shows a configuration of a multi-beam autofocus control device for a camera according to an embodiment. In the figure, a light emitting unit 10 has light emitting diodes 10a, 10b, 10c is provided. A CPU (Central Processing Unit) 12 is connected to these light emitting diodes 10a to 10c via a drive circuit 11, and this CP
Central and left and right light emitting diodes 1 output from U12
When the light emission number commands 0a to 10c are output to the driving circuit 11, the driving circuit 11
To 10c are sequentially driven to output pulsed infrared light beams in a predetermined order.

On the other hand, the light receiving section 14 has a reference light receiving element 14a.
And a wedge light-receiving element 14b. The reference light-receiving element 14a specifies the amount of light of each of the received beams. Baseline length (light-emitting part 1
It is provided [corresponding to FIG. 10B] to measure the distance based on the position in the direction of the line (the line connecting 0 and the light receiving unit 14) and to specify the number of AF steps. A current / voltage conversion amplifier 15a for performing a current / voltage conversion on infrared light by removing unnecessary external light and a gain amplifier 1 are provided downstream of the reference light receiving element 14.
6a, and the infrared light is output in pulse form,
An integration amplifier 17a that integrates this is connected. Similarly, the current / voltage conversion amplifier 15b, the gain amplifier 16b, and the integration amplifier 17 are provided downstream of the other wedge light receiving element 14b.
b is connected.

The reference light receiving element 14a is provided with a comparator 18 after the integrating amplifier 17a. The comparator 18 compares a reference voltage with the output voltage of the integrating amplifier 17a.
It is detected that the received light amount has reached a predetermined light amount. And
The outputs of the integrating amplifiers 17a and 17b and the comparator 18 are supplied to the CPU 12, and the CPU 12
First, the output of the integrating amplifier 17a on the side of the reference light receiving element 14a and the output of the integrating amplifier 17b on the side of the wedge light receiving element 14b are compared to determine the distance of the received light beam, that is, the light receiving position (centroid position) of each beam. Distance measurement is performed. The number of AF stages is detected and output based on the distance measurement value. Further, by the output of the comparator 18 described above,
When it is detected that each of the received beams has reached the predetermined light amount, the CPU 12 detects and outputs the number of light emission of each beam at this time. Then, among the received multi-beams, the beam that has emitted the least number of times of light emission, that is, the beam that has reached a predetermined light amount in a short time is determined to be a beam with no beam missing (or the least). Finally, it is selectively output. The CPU 12 drives the photographing lens 20, and the photographing lens 20 is driven based on the final number of AF steps.

Next, AF detected by the above circuit
The number of stages will be described with reference to FIGS. Here, as shown in FIG. 2, when the camera is shaken about ± 4 degrees from the center (± 0), the projection state of the projection beam to the subject 7 is as shown in FIG. FIG. 3 shows the change in the number of AF stages detected in step (a). That is, FIG. 4 shows the shape of the beam received by the wedge light receiving element 14b. In the case of the right chipping state in FIG.
(B), (f), and (g) correspond to the left missing beams (reversed when light is received), and the center of gravity is shifted to the left by the distance d1. On the other hand, in the case of the left chipping state in FIG.
(C), (d) and (e) correspond to the missing beam, in which case the center of gravity is shifted to the right by the distance d2. Therefore,
In FIG. 3, when the left and right projection beams are left missing, as shown in FIG. B, it is erroneously determined that the distance is short, and the number of AF stages shifts to a smaller direction. Occurs, it is erroneously determined that the distance is long as shown by C in the figure, and the number of AF stages shifts in a direction to increase.

However, as described above, in the embodiment, the comparator 18 and the CPU 12 detect the number of times of light emission reaching a predetermined light amount, thereby judging the state of beam missing, and based on the beam without beam missing, the number of AF stages is determined. I have decided. That is, FIG. 5 shows a change in the distance measurement time (or the gain of the amplifier circuit) when the camera is shaken by about ± 4 degrees as in the above case. Is selected. Therefore, considering FIG. 5 with respect to the measured values of FIG. 3, the measurement state of the number of AF stages shown in FIG. 6 can be obtained. In FIG. 6, although a slight up-down occurs at the switching point of each beam, this fluctuation is within the allowable range of focus, and there is no problem at all. Further, the embodiment shows a limit state in which one of the three projected beams is always projected on the subject 7, and when the distance is further shorter than this, the up-down described above becomes smaller.

The embodiment has the above configuration.
The operation will be described with reference to FIG. First, when the first-stage switch S by the photographing button is turned on in step 401 of FIG. 7, processing for the center beam is performed in steps 402 to 407, and in step 402, light emission for the center beam is performed. Diode 10
b, light receiving processing from light receiving by the light receiving elements 14a and 14b to integration is performed. Next step 403
Is detected, it is detected whether or not the output of the comparator 18 is in a High state in which the output is higher than the reference voltage.
If N ", the process proceeds to step 404. This step 4
In step 04, it is detected whether or not the number of times of light emission has reached, for example, 1000 times.
If Y ", the process proceeds to step 405. This processing is performed when the object 7 is farther than the predetermined distance.
This is performed to stop the comparison operation in.

If "Y" in step 403, the process proceeds to step 405, where the CPU 12 compares the integral level of the reference light receiving element 14a with the integral level of the wedge light receiving element 14b to measure the distance. This is performed, and the number of AF stages shown in FIG. 3 is detected. Then, in step 406, the number of times of emission of the center beam at the time when the High level is output in step 403 is output, and in step 407, the number of AF stages of the center beam detected in step 405 is output.

Next, from step 408 to step 413
The processing for the right beam is performed at step, and the same operation as the above-described center beam is repeated. At step 412, the number of times of light emission until reaching the predetermined light amount at the right beam is output. Is output. In step 410, the number of times of light emission is, for example, 50.
The output of the comparator 18 is stopped when the number of times reaches 0, taking into account that the left and right beams often deviate from the subject 7.

Finally, the process for the left beam is performed in steps 414 to 419 in FIG. 8, and the same operation as described above outputs the number of times of light emission until the predetermined amount of light in the left beam is reached in step 418. And step 4
At 19, the number of AF stages for the left beam is output. Then, in the next step 420, the number of AF steps detected by the three beams is compared, and in the embodiment, the object 7 is detected by detecting whether or not the average value of these AF steps is equal to or less than m. It is determined whether the state is within a predetermined distance. When the number of AF steps is equal to or greater than m, the subject 7 is at a long distance. Therefore, the process proceeds to step 423 without discriminating the beam missing state, and when the number of AF steps is equal to or less than m, the next step is performed. 421. In this step 421, the beam with the smallest number of times of light emission among the three beams is selected, and in the subsequent step 422,
The number of AF stages in the selected beam is output as a final AF stage numerical value.

For example, considering the case where the camera is swung at +0.8 degrees as shown in FIG. 2B, the B portion of the left beam is conventionally selected as shown in FIG.
Although the number of stages is n-3, in the embodiment, as shown in FIG.
As shown in (1), n, which is the number of AF stages of the center beam, is finally selected. Thus, step 4
When the output of the 22 AF steps is completed, the process proceeds to step 423, where the second switch S of the photographing button is operated, and in the next step 424, the photographing lens is driven to a predetermined position by the final number of AF steps. Thus, shooting can be completed under accurate autofocus control.

In the above-described embodiment, the beam loss of each beam received by the reference light receiving element 14a is determined based on the number of times of light emission (time) when a predetermined amount of light is reached. However, the beam loss is also determined by the gain of the amplifier circuit. It can be determined by measuring the intensity of the light intensity of the received light beam. Also, when all the received beams are missing, that is, not only in the case of missing in the base line length direction but also in the upper and lower parts, the beam with the least beam missing is treated as a beam without beam missing. Will be.

Further, in the above-described embodiment, the case where the beam missing in the base line length direction is determined in a state where the light projecting unit 10 and the light receiving unit 14 are arranged in the horizontal direction of the camera has been described. Since the center of gravity is shifted in the longitudinal direction of the base line when the light receiving unit 10 and the light receiving unit 14 are arranged side by side, in this case, the present invention can be applied to the case where the longitudinal beam is chipped.

[0021]

As described above, according to the present invention,
For each distance measurement, it is determined whether or not each beam received by the light receiving unit has a missing beam for all multi-beams.
The beam chipping discriminating means discriminated have provided, this beam chipping select no or lowest beam of the beam missing in the base length direction connecting the light receiving portion the light projecting unit on the basis of the output of the discriminating means, measuring the selected beam Since auto focus control is performed based on distance information, even if a beam break occurs in the base line length direction and the center of gravity moves, accurate auto focus control is performed based on distance measurement information of other beams without beam breaks It becomes possible to do.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a multi-beam autofocus control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a projection state of each beam when a camera is shaken with respect to a subject.

FIG. 3 is a graph showing a change in the number of AF stages obtained under the conditions of FIG. 2;

FIG. 4 is an explanatory diagram showing a moving state of a center of gravity when a beam is missing.

FIG. 5 is a graph showing a distance measuring time of each beam when a distance measuring operation is performed under the conditions of FIG. 2;

FIG. 6 is a graph showing a change in the number of AF stages finally obtained in the embodiment.

FIG. 7 is a flowchart showing the operation of the embodiment.

FIG. 8 is a continuation of the flowchart of FIG. 7 showing the operation of the embodiment.

FIG. 9 is a diagram showing a configuration of a camera front part.

10A and 10B are explanatory diagrams showing a conventional distance measuring state, and FIG. 10A is a diagram showing a light emitting and receiving state of infrared light, and FIG.
FIG. 3 is a diagram showing a light receiving state of the light receiving element.

FIG. 11 is an explanatory diagram showing a state where a multi-beam is projected on a subject.

FIG. 12 is a graph showing a change in the number of AF stages detected when a camera is swung by a predetermined angle using one beam in the related art.

FIG. 13 is a graph showing a change in the number of AF stages detected when a camera is swung by a predetermined angle using three beams in the related art.

[Explanation of symbols]

5, 10: light-emitting unit, 6, 14: light-receiving unit, 7: subject, 10a, 10b, 10c: light-emitting diode, 12: CPU, 14a: reference light-receiving element, 14b: wedge light-receiving element, 17a, 17b: integrating amplifier , 18 ... Comparator.

Claims (1)

(57) [Claims] A light-emitting unit for projecting all of the multi-beams to a subject for each distance measurement, a light-receiving unit for receiving a reflected beam from the subject and outputting distance-measuring information based on the light-receiving position;
A multi-beam autofocus control device for a camera, comprising: a plurality of multi-beams. A beam having no or a minimum beam in the base line length direction connecting the light projecting unit and the light receiving unit based on the output of the multi-beam, and performing autofocus control based on distance measurement information of the selected beam. Auto focus control device.