JP2001324671A - Auto-focusing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an auto-focusing device whose configuration is simplified and which can focus many points at low cost. SOLUTION: In the auto-focusing device, focusing light having specified wavelength is projected to a subject from a light emitting diode 10 through a light projecting lens 11. Then, reflected signal light from the subject being the focusing light is received by sensor arrays 14a and 14b through light receiving lenses 13a and 13b. Deflection panels 12a and 12b are arranged in front of the lens 11 and the lenses 13a and 13b, so that the optical path of the focusing light having the specified wavelength is switched. The panels 12a and 12b are electrically driven and controlled by a CPU 1 through oscillators 6a and 6b.

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,
More specifically, the present invention relates to an improvement in an automatic focusing device for a camera.

[0002]

2. Description of the Related Art In general, triangulation is known as a distance measurement technique. The triangulation is classified into an active method that projects light for distance measurement and a passive method that uses a correlation between luminance distributions of an object viewed from two points, and these methods are used in many cameras. .

Further, as disclosed in, for example, Japanese Patent Application Laid-Open No. 8-250594 filed by the applicant of the present application, many points in a screen are measured by a combination of a so-called active AF and a passive AF. Known distance measuring devices are known.

[0004]

However, the distance measuring device disclosed in Japanese Patent Application Laid-Open No. 8-250594 has dedicated sensors, such as active and passive sensors. Therefore, the device itself is large-scale.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above circumstances, and has as its object to provide a distance measuring apparatus which simplifies the configuration and is capable of measuring distance to more points at low cost. That is.

[0006]

In other words, the present invention provides a light projecting means for projecting a distance measuring light having a predetermined wavelength to a subject, and a light receiving means for receiving a signal signal of the distance measuring light reflected from the subject. Means, an optical path switching means disposed in front of the light projecting means and the light receiving means for switching an optical path of the distance measuring light having the predetermined wavelength, and an optical path switching control means for electrically driving and controlling the optical path switching means And characterized in that:

In the distance measuring apparatus according to the present invention, a light for distance measurement having a predetermined wavelength is projected from the light projecting means to the object, and a reflected signal light of the distance measuring light from the object is transmitted to the light receiving means. Received. Further, the optical path of the distance measuring light having the predetermined wavelength can be switched by an optical path switching means disposed in front of the light projecting means and the light receiving means. The optical path switching means is electrically driven and controlled by the optical path switching control means.

[0008]

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

FIG. 1 shows a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration of a main part of a camera to which the distance measuring device is applied.

In FIG. 1, a CPU 1 is an arithmetic and control unit composed of a one-chip microcomputer or the like for controlling the sequence of the entire camera. The CPU 1 includes a release switch 2 corresponding to a release button for performing a shooting operation of the camera, a driver 3 for driving an infrared light emitting diode 10 described later, a stationary light removing unit 4, The / D converter 5, the oscillators 6a and 6b, and the EEPROM 7 are connected.

The infrared light emitting diode 10 constitutes a light projecting means together with the light projecting lens 11, and light emission is controlled by the CPU 1 via the driver 3. The light beam from the infrared light emitting diode 10 is applied to a subject (not shown) via the light projecting lens 11 and deflection panels 12a and 12b described later. The luminous flux from the subject passes through the deflection panels 12b and 12a again, and further passes through the pair of light receiving lenses 13a and 13a.
b to the sensor arrays 14a and 14b.

The outputs of the sensor arrays 14a and 14b are
The data is supplied to the CPU 1 via the A / D converter 5. Also,
The outputs of the sensor arrays 14a and 14b are also supplied to the stationary light removing unit 4.

The deflection panels 12a and 12b are:
By changing the voltage value applied by the oscillators 6a and 6b, the directions of the molecules of the liquid crystal inside are switched. The EEPROM 7 is a memory for storing a correction coefficient when a correct distance measurement cannot be performed due to a variation in component accuracy.

The CPU 1 detects an input state of the release switch 2 and controls a photographing sequence of the camera.
This photographing sequence includes driving of a focusing lens (not shown) and control of a shutter, but prior to this, photometry and determination of a focusing distance must be performed.

In determining the focusing distance, the distribution of light from the subject obtained through the pair of light receiving lenses 13a and 13b is detected by the sensor arrays 14a and 14b, and the positions of the two obtained image signals are determined. The difference x is based on the principle of triangulation.

FIG. 2 is a diagram for explaining the principle of the triangulation.

The above-mentioned pair of light receiving lenses 13a and 13
b has a focal length f and is shifted by the base line length B. In addition, the image of the subject existing at a position at a distance L from the light receiving lenses 13a and 13b is such that the position incident on the sensor array 14a with respect to the sensor array 14b by the positional difference indicated by x in the drawing is based on the optical axis. It will shift.

Since the position difference x has a relation of x = (B · f) / L, the CPU 1
The outputs of “a” and “14b” are input via the A / D converter 5 and compared with each other to obtain x, thereby obtaining the focusing distance L. The distance measurement based on the image signal is referred to as passive distance measurement.

When the subject 17 is wearing pure white clothes or when there is no clear contrast in the image, the driver 3 is controlled to control the light projecting means (the infrared light emitting diode 10 and the light projecting lens 11). ) May be projected. The use of the light projected from the camera in this way is called active distance measurement.

However, when the subject 17 is irradiated with sunlight or the like, the S / N ratio of the signal light deteriorates and the detection becomes impossible, so that the steady light removing unit 4 is operated to irradiate the subject 17 constantly. It is more effective if only the signal light component is extracted by using the difference between the frequency of the sun light and the frequency of the signal light projected in a pulsed manner.

If the signal light is formed into a spot shape, a reflected signal light component as shown in FIG. 2C is extracted from the sensor array 14a. FIG. 2B shows that the image signal of the subject 17 is output from the sensor array 14 without operating the steady light removing unit 4.
3 shows an image incident on a.

As shown in FIG. 2 (b), the position of the image signal changes in a solid line or a broken line depending on the subject distance L.

The feature of the first embodiment is that deflection panels 12a and 12b for electrically deflecting equivalent light are arranged in front of the distance measuring apparatus having such a configuration.

The deflecting panels 12a and 12b may have basically the same configuration except for the control timing. For example, as shown in FIG. 3A, the deflection panel 12a is a plate having a structure in which a liquid crystal and a monomer are sandwiched between a pair of glass or plastic substrates 20 and 21 having a transparent electrode coated on the inside. It consists of.

As shown in FIG. 3A, the liquid crystal and the monomer constitute a diffraction grating having a pitch d, and a relatively pure polymer portion 22 and a liquid crystal fine grain portion 23 are alternately formed. It has a structure that is repeatedly arranged. This liquid crystal section can cause a change in the refractive index that changes the molecular direction by applying a voltage.

When no voltage is applied, the polymer part 22 and the liquid crystal fine grain part 23 have different refractive indices.
A diffraction phenomenon as shown in (b) occurs, and the light beam can be deflected.

Here, assuming that the incident angle is θ and the exit angle is θ ′, the relational expression of sin θ−sin θ ′ = (mλ) / d is established. Where λ is the wavelength, m is the diffraction order,
d is the pitch.

When a voltage is applied, the direction of the optical axis of the liquid crystal molecules changes and matches the refractive index of the polymer portion 22, and the plate becomes a transparent cell. At this time, the light beam is not deflected, and the light incident on the plate passes through the plate without changing its direction.

As described above, the plate can eliminate or cause the bending (deflection) of the light beam having the wavelength λ depending on whether or not the voltage is applied to the plate. Therefore, the deflection panel using this plate can function as an optical element that can be electrically controlled to bend light.

In the deflection panels 12a and 12b, the voltage is applied by the oscillators 6a and 6b, whereby the direction of the molecules of the liquid crystal inside is switched, and the direction of the transmitted light beam is switched. Although the light beam whose direction can be changed is only a specific wavelength, it has sufficient characteristics to bend the distance measuring light of the active AF using an LED of a substantially single wavelength as a light source.

With the above-described configuration, when a voltage is applied to the two deflection panels (plates) 12a and 12b, as shown in FIG. even straight after the condensing projected by the light projecting lens 11, with respect to the screen center direction a _1, so that the optical projection is done.

Similarly, the reflected light from the subject travels straight through the two deflection panels 12a and 12b and passes through the sensor arrays 14a and 14a.
14b. Therefore, these two sensor arrays 14a, the position difference x of the incident results to 14b, by performing the distance calculation by triangulation as described above, it is possible to point A ₁ to the distance measurement in the active type.

When a voltage is applied only to the deflecting panel 12a, the light passing through the deflecting panel 12a goes straight, but the light passing through the deflecting panel 12b is deflected, as shown in FIG. You will go in the direction of ₂ . This effect, the light is projected to the portion of the A ₂ shown in Figure 4 (a).

Similarly, the reflected light is bent at the deflection panel 12b, goes straight on the deflection panel 12a, and is incident on the sensor arrays 14a and 14b. Therefore, active distance measurement can be performed using the reflected signal light.

When the voltage is applied to the deflection panel 12b without applying the voltage to the deflection panel 12a,
As shown in FIG. 3 (e), the light is deflected by the deflecting panel 12a, is straight with deflection panel 12b, toward the direction of A _3. In other words, it is possible to light projection in the direction of A ₃ shown in Figure 4 (a).

The light returned from the direction of the A ₃ are straight similarly deflecting panel 12b, is bent by the deflection panel 12a and sensor array 14a, and is incident on 14b. Therefore, as described above, the two sensor arrays 14a,
By examining the position difference x of the reflected light on 14b, the distance can be measured.

As described above, in the active distance measurement, by switching the voltage application to the deflection panel where the light is electrically bent, as shown in FIG. 4A, three points (A) in the vertical direction of the screen are displayed. ₁ , A ₂ , A ₃ ), and since the sensor array has a monitor range (monitorable area 14 c) in the horizontal direction of the screen, passive distance measurement should be performed by increasing the number of points in the horizontal direction of the screen. Can be. Therefore, for example, as shown in FIG.
It is possible to measure two points 26. Therefore, as shown in FIG.
Center of 5 the scene that is not present in (A ₁ part), even for the composition which is a weak point in conventional cameras, properly subject 17
Distance measurement and focusing can be performed.

As described above, conventionally, there has been a demand for a camera capable of automatically focusing a subject anywhere on the screen simply by pressing a release button of the camera. However, according to the present invention, FIG. This can be dealt with even in the composition shown in b).

FIG. 5 is a flowchart for explaining the distance measuring operation of the camera having such a configuration. The control of this operation is performed under the control of the CPU 1.

That is, first, in step S1, a voltage is applied to the two deflection panels 12a and 12b, the subject image is sequentially determined in five portions of the sensor array by the passive AF system, and five-point distance measurement is performed. Will be These results
L _{P1 to} L _P5 .

Next, in step S2, the control of the two deflection panels 12a and 12b is the same as in step S1. Then, light for distance measurement is projected from the infrared LED 10, and components of the output of the sensor arrays 14 a and 14 b due to light that is constantly incident are removed by the stationary light removing unit 4, and only the pulse-like signal light is removed. Amplified. Thus, according to the principle of the active AF, A shown in FIG.
The distance measurement of the portion ₁ is performed (the result is assumed to be _LA1 ).
Note that, since the existence probability of the main subject is high at the center of the screen, the AF is performed twice, that is, the passive type and the active type, so that there are no poor subjects.

Next, in step S3, the above-described liquid crystal
Active due to the beam bending effect of the plate
A of FIG. 4 (a)_TwoDirection is measured and the result is
Is L _A2It is said. Similarly, in step S4, the liquid crystal display
Active method due to light bending effect by heat
And A in FIG._ThreeDirection is measured and the result is L
_A3It is said.

[0043] Then, in step S5, from the results of the _{L P1 ~L P5, L A1 ~L} A3 in step S1 to S4, focusing is performed shows the closest distance as L _1.

As described above, according to the first embodiment, a light beam direction switching function having a simple structure is utilized by utilizing the fact that the distance measuring light used in the active AF is light of a single-wavelength LED. Since the direction of the distance measurement is increased by effectively utilizing the deflection panel with the attached, it is possible to provide a camera having a simple configuration capable of focusing regardless of the position of the main subject in the screen.

Further, since the active AF and the passive AF are used in combination, in the central portion of the screen where there is a high probability that the main subject exists, the distance measurement can be performed correctly by compensating for the weak points of both methods, thereby improving the accuracy. be able to.

Further, since the number of the sensor arrays may be one, the area of the light receiving element can be increased to prevent an increase in cost.

Next, a second embodiment of the present invention will be described.

FIG. 6A is a diagram showing a configuration of a main part of a distance measuring apparatus according to a second embodiment of the present invention.

In the above-described first embodiment, one light-emitting element is used. In the second embodiment, three light-emitting elements (LEDs) are prepared and the first light-emitting element is used. As in the case of the embodiment, 3 × 3
= 9 active distance measurement (FIG. 6)
(B)).

That is, a total of three sets of LEs
D10a, 10b, and 10c are prepared. The other configuration is similar to the configuration shown in FIG. 1 of the above-described first embodiment, and the description is omitted.

In the second embodiment, in the monitorable area 14c of the sensor array, the distance can be measured even by the passive AF method. Therefore, three active distance measuring points in this area are active. By selecting the more reliable one of the two types, passive and passive, it is possible to perform distance measurement overcoming difficult subjects. In addition, since there are active AF ranging points above and below,
As shown in FIG. 6C, it is possible to focus on the main subject 17 present at the corner of the screen 25.

According to the second embodiment, similarly to the first embodiment, in the passive AF that basically performs distance measurement using an image signal based on visible light, a light beam having only a specific wavelength is bent. By combining active AF with light projection of a specific wavelength to overcome the difficult subject and enable multi-point ranging, where the effect cannot be obtained with a liquid crystal panel that can perform Focusing is possible.

In the first and second embodiments described above, the size of the plate is reduced by bending light in a direction orthogonal to the direction connecting the light projecting lens and the light receiving lens.

That is, when the light beam is bent in the direction connecting the light emitting and receiving lenses, as shown in FIG.
Since light enters and exits the plate from portions wider than the outside of each of the light receiving lens 13 and the light receiving lens 13b (in the figure, the direction above the light receiving lens 13b), the plate becomes large, resulting in cost and space disadvantages.

However, if the camera has a specification that allows this, it is possible to expect effects different from those of the above-described first and second embodiments with the configuration shown in FIG. 7A. .

That is, as a third embodiment, two infrared light emitting diodes 10
If the light is bent in the vertical direction in FIG. 7A by the deflection panel 12a or 12b when the distance is measured by sequentially irradiating the distances b and 10c, the distance measuring point shown in FIG. 10b ₂ and 10c ₂ can be measured, and if the light is not bent, the distance measuring points 10b ₁ and 10c _{1 are} measured.
Can be measured. In FIG. 7B, reference numeral 14c denotes a range (monitorable area) monitored by the sensor array 14a or 14b when the light is not bent.

As described above, it is possible to measure the distance of a wide field of view and the distance of a narrow field of view by switching the optical path. For example, according to the flowchart shown in FIG. You may do so.

In this case, as shown in FIG.
The distance measuring points 10b ₂ and 10c ₂ are suitable for the wide screen indicated by W, and when this area is measured on the tele screen indicated by T, the distance becomes an off-screen distance.

Here, the operation of the third embodiment of the present invention will be described with reference to the flowchart of FIG.

First, in step S11, passive distance measurement is performed in the monitorable area 14c. Next, in step S12, low contrast determination is performed to determine that an image signal cannot be obtained. Here, when the contrast is not low, the process proceeds to step S14, and when the contrast is low, the process proceeds to step S13.

In Step S13, the LEDs 10b, 10
c is projected and the distance measurement point 10b ₁, 10c₁About
Distance measurement is performed. At this time, the deflection panels 12a, 12b
No voltage application and optical path bending are performed. This
Therefore, it is possible to measure distance even for subjects that passive AF is not good at
Become.

Next, in step S14, the zoom position of the camera is determined. Here, if the zoom position is wide, the process proceeds to steps S15 and S16,
The optical path is bent by the deflection panels 12a and 12b. Then, the LEDs 10b and 10c emit light, and the distance measuring points 10b ₂ and 10c ₂ are measured.

On the other hand, when the zoom position is tele, this area is outside the screen, so that the above steps S15 and S1
6 is not performed and the distance is not measured.

Based on the above distance measurement results, in step S17, the closest distance is selected and set as the focusing distance.

As described above, according to the third embodiment, the field of view of the distance measurement is expanded or narrowed as necessary, so that the optimum distance measurement point can be selected in accordance with the zoom lens. And highly accurate focusing can be achieved. Also,
Since the width of the sensor array can be reduced, it is also useful for cost reduction.

According to the above embodiment of the present invention,
The following configuration can be obtained.

(1) Light projecting means for projecting a distance measuring light having a predetermined wavelength onto a subject, light receiving means for receiving the reflected signal light of the distance measuring light from the subject, the light projecting means, A distance measuring device comprising: an optical path switching means disposed in front of a light receiving means and capable of electrically switching an optical path of a predetermined wavelength; and an optical path switching control means for controlling the optical path switching of the optical path switching means.

(2) The distance measuring apparatus according to (1), wherein the optical path switching direction of the optical path switching means is a direction orthogonal to a direction connecting the light projecting means and the light receiving means.

(3) The optical path switching means sets the optical path to the first
The distance measuring apparatus according to the above (1), comprising: a first plate for switching to a second direction; and a second plate for switching an optical path to a second direction.

[0070]

As described above, according to the present invention, it is possible to provide a distance measuring apparatus capable of measuring a large number of points on a screen with a simple configuration, thereby enabling focusing in any scene. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a main part of a camera to which a distance measuring device is applied in a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the principle of triangulation.

FIG. 3 is a diagram for explaining a configuration of the deflection panel of FIG. 1;

FIG. 4 is a diagram illustrating a ranging point in a screen.

FIG. 5 is a flowchart illustrating a distance measurement operation of the camera according to the first embodiment.

FIG. 6A is a view showing a configuration of a main part of a distance measuring apparatus according to a second embodiment of the present invention, and FIG. 6B is a view showing a distance measuring point in the second embodiment; FIG. 7C is a diagram showing an example of a subject that can be measured according to the second embodiment.

FIG. 7A is a diagram showing a configuration of a main part of a distance measuring apparatus according to a third embodiment of the present invention, and FIG. 7B is an example of a distance measuring point according to the third embodiment; FIG.

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

[Explanation of symbols]

 1 CPU, 2 release switch, 3 driver, 4 steady light removing unit, 5 A / D converter, 6a, 6b oscillator, 7 EEPROM, 10 infrared light emitting diode, 11 light emitting lens, 12a, 12b deflection panel, 13a, 13b light receiving lens, 14a, 14b sensor array, 14c monitorable area, 17 subjects, 20, 21 substrate, 22 polymer part, 23 liquid crystal fine grain part, 25 screens.

Claims (3)

[Claims] 1. A light projecting means for projecting a distance measuring light having a predetermined wavelength onto a subject, a light receiving means for receiving a reflection signal light of the distance measuring light from the subject, a light projecting means, and a light receiving means Light path switching means disposed in front of the means and capable of switching an optical path of the distance measuring light having the predetermined wavelength; and light path switching control means for electrically driving and controlling the optical path switching means. Distance measuring device. 2. The distance measuring apparatus according to claim 1, wherein an optical path switching direction of said optical path switching means is a direction orthogonal to a direction connecting said light projecting means and said light receiving means. 3. The optical path switching means includes a first plate that switches an optical path in a first direction and a second plate that switches an optical path in a second direction different from the first direction. The distance measuring apparatus according to claim 1.