JPH06105328B2 - Automatic focusing device - Google Patents

Description

The present invention relates to an automatic focusing device suitable for use in a video camera or the like.

[Conventional technology]

In video cameras, various techniques for automating various adjustment mechanisms have been proposed and implemented, and their operability has been rapidly improved. Various automatic focusing devices have been proposed for automatically adjusting the focusing mechanism for focusing on the subject, and an automatic focusing device using infrared rays is known as one example (for example, Japanese Patent Application Laid-Open No. 2004-242242). Akira
57-20708).

This irradiates the subject with infrared light emitted from the light emitting element,
The reflected light is received by the light receiving element, and the deviation from the in-focus state for the subject is determined according to the light receiving state of the light receiving element. This light receiving element is composed of two light receiving portions, and moves in conjunction with the feeding operation of the imaging lens. If the light receiving portions of each of the light receiving elements are irradiated with an equal amount of reflected light (that is, when the light receiving amounts of the two light receiving portions are equal to each other, this is hereinafter referred to as the light receiving amount is balanced), Based on the detection output of the light receiving element, it is determined that the object is in focus, and the image pickup lens is also in a position in which the subject is in focus. When the amount of light received by the light receiving element is not balanced, the light receiving element moves so that the amount of light received is balanced, and along with this, the imaging lens also moves so as to be in focus.

[Problems to be solved by the invention]

By the way, when infrared light is emitted from the light emitting element on the video camera side, part of the infrared light may not be reflected to the video camera side depending on the subject or the position of the subject within the field of view of the video camera. is there. When the subject is completely irradiated with infrared rays, the irradiation area (that is, the projection spot) becomes circular, and if the reflectance within this projection spot is almost uniform, the entire projection spot will be reflected with a uniform amount. Occurs. However, when focusing on a subject such as a black and white pattern in which different reflectance regions are combined or a subject with uneven reflectance (hereinafter, such a subject is referred to as a subject having contrast), In some of the projection spots, the amount of reflected light is smaller than in the other portions, and the light-receiving spots produced by the light-receiving element have a circular shape with a part cut off. Further, when the projection spot on the subject partly protrudes from the boundary of the subject, there is no reflected light from the protruding part. Therefore, also in this case, the circular light-receiving spot in the light-receiving element is partially lacking.

As described above, if the light receiving spot of the light receiving element has a partly lacking shape, there is a problem that an error occurs in the focus determination and the performance of the automatic focusing device deteriorates. Hereinafter, this point will be described with reference to FIG.

In the figure, the light receiving element 31 is a two-divided light receiving element having two light receiving portions 31a and 31b divided by a separation band 32. When the subject is completely irradiated with infrared rays and the infrared rays are uniformly reflected from the entire projection spot on the subject, the light receiving spots of the light receiving element are circular, and when focusing, as shown in FIG. 10 (a), The light receiving spots 33 are generated so that the light receiving amounts of the light receiving portions 31a and 31b are equal to each other, that is, they are symmetrical with respect to the separation band 32. In this state, the light receiving element 31 is in a state in which the amount of received light is balanced.

On the other hand, when a part of the light receiving spot is missing, as shown in FIG. 10 (b), the circular spot including the part indicated by the broken line of the light receiving spot 33 (this is the missing part) is a separation band. When it occurs at a position symmetrical with respect to 32, the in-focus state is obtained.
Since the light receiving amounts of 31b are different and unbalanced, the light receiving element moves so that the light receiving units 31a and 31b have the same light receiving amount as shown in FIG. 10 (c). The lens focus lens also moves. In the state shown in FIG. 10 (c), the amount of light received by the light receiving element is balanced, but the light receiving spot 33 is displaced toward the light receiving portion 31b by Δx, and the focus lens is focused by this amount. As described above, if part of the light receiving spot on the light receiving element is missing due to the contrast of the subject, the irradiation position of the infrared spot on the subject, the shape of the subject, etc. However, there is a problem in that the focused state cannot be obtained. Although it is possible to make the amount of blurring on the screen inconspicuous due to the distance measurement error by making the base line length sufficiently long, there is a problem that the automatic focusing device becomes large.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide an automatic focusing device capable of improving the accuracy of focusing determination even if the light receiving spot of the light receiving element is partially missing.

[Means for solving problems]

In order to achieve the above object, the present invention provides one set of a light projecting system including a light receiving element and a projection lens, while it includes a light receiving lens and a light receiving element and receives a reflected light beam from a subject. Two sets of system are provided.

[Action]

As described above, the position of the center of gravity of the light-receiving spot generated in the light-receiving element changes according to the distance to the subject,
The distance to the subject can be measured by detecting the position of the center of gravity. However, if the shape of the light receiving spot is partly lost, the position of the center of gravity also changes, which affects the distance measurement accuracy.

On the other hand, 2 on the same plane including the optical axis of the projection lens
When a pair of light receiving systems is provided, the barycentric position of the light receiving spots on the light receiving elements in each light receiving system is displaced by the same amount when the shape of the light receiving spots is partially lacking. From this, by using the detection signals of the two light receiving elements,
The distance to the subject can be obtained by canceling the shift amount of the position of the center of gravity.

〔Example〕

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

FIG. 1 is a block diagram showing an embodiment of an automatic focusing device according to the present invention, in which 1 is a light emitting element, 2 is a projection lens, 3 and 4 are light receiving lenses, 5 and 6 are plane parallel plates, and 5a, 6a is a mounting member, 6a, 6
b is an arm, 5c and 6c are cam followers, 7 and 8 are elastic members, and 9 and 1
0 is a light receiving element, 9a, 9b, 10a, 10b is a light receiving portion, 9c, 10c is a separation band, 11 is a focus ring, 11a, 11b is a cam, 11c is a worm wheel, 12 is an automatic focusing circuit, 13 is a motor, 14 is a wheel and 15 is a subject.

In the figure, a light receiving element 9 is provided on one side (upper side) and a light receiving element 10 is provided on the other side (lower side) with respect to the optical axis of the light emitting element 1. A projection lens 2 is provided in front of the light emitting element 1 so that the optical axis coincides with the light emission center. A parallel plane plate 5 and a light receiving lens 3 are provided in front of the light receiving element 9 along the optical axis thereof, and a parallel plane plate 6 and a light receiving element 4 are similarly provided in front of the light receiving element 10. . The above members are provided outside the imaging lens (not shown) including the focus ring 11.

Two cams 11a and 11b are provided on the end surface of the focus ring 11 opposite to the subject 15. An arm 5b is integrally attached to a transparent parallel flat plate 5 such as glass by a mounting member 5a, and a cam follower is attached to the tip of the arm 5b.
5c is formed. The plane-parallel plate 5 is rotatable about an axis (not shown) perpendicular to the plane of the sheet passing through the mounting member 5a,
The cam follower 5c is pressed against the cam 11a by the elastic member 7. Therefore, when the focus ring 11 rotates, the pressure contact point of the cam follower 5c with respect to the cam 11a changes, and the parallel plane plate 5 rotates accordingly. The same applies to the plane-parallel plate 6, the arm 6b is integrally attached by the mounting member 6a, and the cam follower 6c formed at the tip of the arm 6b is moved by the elastic member 8 to the cam 11.
Pressed against b. Therefore, as the focus ring 11 rotates, the plane-parallel plate 6 rotates about an axis (not shown) perpendicular to the plane of the drawing passing through the mounting member 6a. Where cam 11
b is more recessed than the cam 11a, and when viewed from the end face side of the focus ring 11, as shown in FIG.
The cam follower 5c is in pressure contact with the cam 11a, and the cam follower 6c is shorter than the cam follower 5c and only in contact with the cam 11b.

The light-receiving elements 9 and 10 are, for example, two-divided light-receiving elements such as two-divided PIN photodiodes as shown in FIG.
Separation band 9c of the light receiving element 9 (corresponding to the separation band 32 in FIG. 10)
One light receiving section 9b (corresponding to the light receiving section 31b in FIG. 10) is divided by the light emitting element 1 side, and the other light receiving section 9a (corresponding to the light receiving section 31a in FIG. 10) is the opposite side. Placed in
Similarly, the light receiving portion 10a divided by the separation band 10c of the light receiving element is arranged on the light emitting element 1 side, and the other light receiving portion 10b is arranged on the opposite side.

In such a configuration, the light beam having a circular spot shape emitted from the light emitting element 1 passes through the projection lens 2 and the subject 15
Is irradiated. A part of the light beam reflected and diffused by the subject 15 is incident on the light receiving element 9 through the light receiving lens 3 and the plane parallel plate 5. As a result, a light receiving spot is formed on the light receiving element 9. Further, another part of the light beam from the subject 15 passes through the light receiving lens 4 and the plane-parallel plate 6 to receive the light receiving element 10.
Is incident on. As a result, a light receiving spot is formed on the light receiving element 10.

From the light receiving elements 9 and 10, signals corresponding to the light receiving spot positions of the light receiving elements 9 and 10 are obtained, whereby the automatic focusing circuit 12 forms a focus control signal. The focus control signal causes the motor 13 to rotate, the rotational force of the motor 13 is transmitted to the focus ring 11 via the wheel 14 and the worm wheel 11c, and the focus ring 11 rotates. As the focus ring 11 rotates, the plane parallel plates 5 and 6 rotate, the light beam is deflected, and the light receiving spot positions on the light receiving elements 9 and 10 change. When the light-receiving spots on the light-receiving elements 9 and 10 are set to the desired positions, they are in focus, the motor 13 stops, and the plane-parallel plates 5 and 6 are fixed.

Next, referring to FIG. 3, the projection lens 2 in this embodiment,
The positional relationship between the light receiving lenses 3 and 4 and the light receiving elements 9 and 10 and the operating principle will be described in more detail. In the figure, 16,1
6'is the projection spot on the subject 15, and 17 to 20 are the subjects 15
The same reference numerals are given to the portions corresponding to FIG.

In FIG. 3, the light receiving lenses 3 and 4 are arranged on the same plane perpendicular to the optical axis of the projection lens 2, and when the focal lengths of these light receiving lenses 3 and 4 are f, the light receiving elements 9 and 10 respectively. It is arranged at a distance f from the light receiving lenses 3 and 4. The optical axes of the projection lens 2 and the light receiving lenses 3 and 4 are parallel to each other, and the separation bands 9c and 10c of the two light receiving portions of the light receiving elements 9 and 10 are positioned on the optical axes of the light receiving lenses 3 and 4. There is. The light emission center of the light emitting element 1 is on the optical axis of the projection lens 2.

Now, it is assumed that the subject at a distance y from the light receiving lenses 3 and 4 is irradiated with the light beam from the light emitting element 1. If the subject has no contrast and the spot shape of the projection beam is circular, the projection spot 16 on the subject is circular. A part of the reflected light beam 17 from the projection spot 16 is applied to the light receiving element 9 through the light receiving lens 3, and another part of the reflected light beam 18 is applied to the light receiving element 10 through the light receiving lens 4. The shape of the light-receiving spots on 9 and 10 is circular. When the shift amounts of the centers of gravity of these light receiving spots from the separation zones 9c and 10c are x ₁ and x ₂ with respect to this distance y, the following relational expression is established.

However, the center of gravity of the light-receiving spot is the light-receiving amount on one side and the light-receiving amount on the other side of this dividing line when the light-receiving spot is divided by a line parallel to the separation bands 9c, 10c of the light-receiving elements 9, 10. Are points on the dividing line such that are equal to each other. For example,
As shown in FIG. 10 (a), when the light receiving spot 33 is circular, it is the center of the light receiving spot 33, and as shown in FIG. 10 (c), when the light receiving spot 33 is partially circular, , Separator
When the light receiving amounts of the light receiving portions 31a and 31b are equal to 32, the center of gravity of the light receiving spot 32 is the center on the separation band 32 in the light receiving spot 33.

If the above equations (1) and (2) are added, By transforming this, Therefore, the distance y from the shift amounts x ₁ and x ₂ to the subject 15 can be obtained.

On the other hand, if the subject 15 has a contrast, and for this reason a circular projection spot 16 'with a part missing is obtained, if the distance to the subject 15 is y equal to the above, the projection spot 16' The light-receiving spot on the light-receiving element 9 due to a part of the light-reflected beam 19 from is also a circular shape with a part missing, and its center of gravity is closer to the separation band 9c by Δx ₁ than when the light-receiving spot is circular. . On the other hand, in the light receiving element 10, the reflected light beam 20 from the projection spot 16 'is
As a result, the center of gravity of the light-receiving spot is further away from the separation band 10c by Δx ₂ than when the light-receiving spot is circular. Therefore, the distance y at this time is the same as above. Will be represented by.

However, now, the shift amount of the center of gravity of the projection Supotsuto 16, 16 'and [Delta] H, [Delta] x _1, when the [Delta] x ₂ geometrically determined, becomes completely equal as follows.

By substituting the equation (6) into the equation (5), the distance y is expressed as follows.

This equation (7) is equal to the equation (4) in the case of the circular light receiving spot. Therefore, by adding the amount of deviation of the center of gravity of the light-receiving spots from the light-receiving elements 9 and 10 from the separation bands 9c and 10c, the distance y to the subject can be accurately determined even if the shape of the light-receiving spots is defective. Obtainable.

Now, if the light-receiving spots on the light-receiving elements 9 and 10 are moved so that the center of gravity of the light-receiving spots on the light-receiving elements 9 and 10 coincides with the separation bands 9c and 10c, (x _1-
Δx ₁ ), (x ₂ + Δx ₂ ) can be measured, and the distance y to the subject can be obtained from the equation (5), that is, the equation (7).

In FIG. 1, the light receiving spots on the light receiving elements 9 and 10 are displaced by the rotation of the plane parallel plates 5 and 6, and their centers of gravity are made to coincide with the separation bands 9c and 10c. In this case, the plane parallel plate 5,
Although 6 rotates due to the rotation of the focus ring 11, the rotation of the focus ring 11 also displaces a not-shown focus lens in the optical axis direction. Even if the distance y to the subject 15 is any value, the focus lens is focused on the subject 15 when the center of gravity of the light receiving spots of the light receiving elements 9 and 10 is on the separation bands 9c and 10c. On the cam of Focus ring 11
11a and 11b are configured. In other words, the above formula (7) is calculated by the rotation of the plane-parallel plates 5, 6 by the cams 11a, 11b, and the subject 15 at the distance y is calculated based on the calculation result.
The position of the focus lens is set so as to focus on.

Here, when the subject 15 is at infinity (y = ∞), the center of gravity of the circular light-receiving spots on the light-receiving elements 9 and 10 is the separation bands 9c and 10c.
Parallel plane plates 5 and 6 and photo detectors 9 and 10
Are arranged. From the above, the rotation angle from the state when the object 15 of the plane-parallel plates 5 and 6 is at infinity corresponds to the distance y to the object 15 one to one. Therefore, the focus lens movement amount for focusing when the subject 15 is at infinity is Z, the center of gravity of the light receiving spot is the light receiving element 9 from the position when the subject 15 is at infinity,
In order to match the 10 separation bands 9c, 10c, the plane-parallel plates 5, 6
If the movement amount of the cam followers 5c and 6c for rotating the cam 11 by the angle α is Z ₀ , the list amount L _f of the cams 11a and 11b is L _f = Z ₀ −Z (8). However, when L is the length of the arms 5b and 6b (that is, the distance from the center of rotation of the plane parallel plates 5 and 6 to the center of the cam followers 5c and 6c), the movement amount Z ₀ is expressed as follows.

Z ₀ = Lsinα (9) Further, there is the following relationship between the rotation angle α of the plane parallel plates 5 and 6 and the movement amount x of the light receiving spot on the light receiving elements 9 and 10. .

However, t = thickness of the plane-parallel plates 5, 6 N = refractive index of the plane-parallel plates 5,6 θ = incident angle of the reflected light beam to the light-receiving lenses 3, 4 (tan ^-1 (for the light-receiving lens 3) l ₁ / y), and (tan ^-1 (l ₂ / y)) for the light-receiving lens 4, Therefore, when the distance y to the subject 15 is set variously, the movement amount x of the formula (10) becomes A rotation angle α that is equal to the equation (1) or the equation (2) is determined, and the movement amount Z ₀ of the cam followers 5c and 6c and the focus for focusing according to the equation (9) using the rotation angle α. Based on the lens movement amount Z, equation (8)
The lift amount L _{f of the} cam can be obtained from. Such a lift amount of the cam obtained by L _f, can be set each of the cam 11a of Fuokasu ring 11, and 11b shape.

A detection signal of a level corresponding to the amount of light received by the light receiving portions 9a, 9b of the light receiving element 9 and a detection signal of a level according to the amount of light received by the light receiving portions 10a, 10b of the light receiving element 10 are supplied to the automatic focusing circuit 12. . This automatic focusing circuit 12 detects the light receiving elements 9 and 10 from these detection signals.
Detects which direction the center of gravity of the light-receiving spot deviates from the separation bands 9c and 10c, forms a focus control signal corresponding to the direction of deviation, and supplies the focus control signal to the motor 13. As a result, the motor 13 rotates, and the center of gravity of the light receiving spot is set to the light receiving element.
Focus ring to match 9,10 separators 9c, 10c
11 is rotated to rotate the plane parallel plates 5 and 6.

Therefore, if the levels of the detection signals from the light receiving portions 9a and 9b of the light receiving element 9 are A and B, respectively, and the levels of the detection signals from the light receiving portions 10a and 10b of the light receiving element 10 are C and D, respectively, the light receiving spots will be described. Is circular and the center of gravity of the light-receiving spot coincides with the separation bands 9c and 10c of the light-receiving elements 9 and 10 when the subject 15 is at infinity, and part of the light-receiving spot is expressed by the formulas (5) to (7). Even if it is missing
The displacement of the center of gravity of the light receiving spot due to this chipping on the light receiving spots 9 and 10 is offset by adding the distances from the separation bands 9c and 10c of the center of gravity of the light receiving spots on the light receiving elements 9 and 10. Therefore, when (A−B) + (D−C) = (A + D) − (B + C) = 0 (11), the center of gravity of the light receiving spots on the light receiving elements 9 and 10 is the separation band.
It corresponds to 9c and 10c and is in focus.

On the other hand, when the subject 15 moves toward the image pickup lens side, in the light receiving elements 9 and 10, the light receiving amounts of the light receiving portions 9a and 10b are equal to the light receiving portions 9b and 10a.
Is larger than the received light amount of (A + D)-(B + C)> 0 (12), and the automatic focusing circuit 12 outputs the focus control signal so that the condition (10) is satisfied. . Further, when the subject 15 moves to the side opposite to the imaging lens, (A + D)-(B + C) <0 (13), and the automatic focusing circuit 12 moves in the direction opposite to that of the equation (12). A focus control signal for rotating 13 is output.

As described above, in this embodiment, even if a part of the light receiving spot is missing, the focus lens can be accurately focused on a subject at an arbitrary distance. According to this embodiment, since the two cams are provided on the focus ring, the number of one component is small, and the error due to the combination of the components can be reduced.

FIG. 4 is a block diagram showing another embodiment of the automatic focusing device according to the present invention, in which 21 is a slider plate, 21a, 21b and 21c are guide grooves, 22 is a cam follower, 23 and 24 are pins, and 25 is It is an elastic member, and the same reference numerals are given to the portions corresponding to FIG.

In FIG. 4, the end face of the focus ring 11 is one cam 11
constitutes a. The slider plate 21 has a substantially cross shape having two protrusions parallel to the intersecting axis of the light receiving lenses 3 and 4 and two protrusions substantially orthogonal to these protrusions. Of these projections, the projections parallel to the optical axes of the light receiving lenses 3 and 4 are provided with guide grooves 21b and 21c, respectively, and the guide grooves 21b and 21c are provided with pins 23 and 24 fixed to the imaging lens main body. It is inserted without rattling. As a result, the slider plate 21 becomes a light receiving lens.
It can slide smoothly in the 3 and 4 optical axis directions. In addition, the slider plate 2
1 is provided with one guide groove 21a across two protrusions in a direction substantially perpendicular to the optical axes of the light-receiving lenses 3 and 4, and the tip of an arm 5b integrally formed with the plane-parallel plate 5 is provided therein. The cam follower 5c and the cam follower 6c at the tip of the arm 6b integrally formed with the parallel flat plate 6 are slidably and slidably inserted. Furthermore, a cam follower 22 is press-fitted to the slider plate 21 at the tip of the protrusion on the focus ring 11 side of the protrusions parallel to the optical axes of the light receiving lenses 3 and 4, and the cam follower 22 is attached to the focus ring 11. The slider plate 21 is pressed by the elastic member 25 so as to be pressed against the cam 11a.

In such a configuration, the focus ring 11 is driven by the motor 13.
When is rotated, the slider plate 21 moves in parallel with the optical axes of the light receiving lenses 3 and 4, whereby the cam followers 5c and 6c also slide in the guide groove 21a and move in the same direction to move the parallel plane plate 5, 6
Rotates. Therefore, the light receiving spots are displaced on the light receiving elements 9 and 10. In this case, when the center of gravity of the light-receiving spots on the light-receiving elements 9 and 10 coincides with the separation bands 9c and 10c, the focus lens (not shown) focuses on the subject 15, so that the cam 11a and the guide groove 21a. The shapes and lengths of the arms 5b and 6b are set.

According to this embodiment, since the two parallel plane plates are rotated by the movement of one slider plate, only one cam is provided on the focus ring, so that the structure is relatively simple. .

FIG. 5 is a block diagram showing an example of an automatic focusing device by a method different from the previous embodiment, in which 26 and 27 are non-scanning type semiconductor position detecting elements (hereinafter referred to as PSD) and 28 is a potentiometer. Therefore, the same reference numerals are attached to the portions corresponding to FIG.

In this example, as shown in FIG. 5, PSDs 26 and 27 as light receiving elements are arranged on one side of the light emitting element 1. These PS
D26 and 27 respectively output detection signals according to the position of the center of gravity of the light receiving spot. On the other hand, the potentiometer 28 is a focus ring.
It is interlocked with the rotation of 28 and outputs a detection signal according to the position of a focus lens (not shown). Automatic focusing device
The reference numeral 12 obtains the position of the focus lens for focusing on the object 15 from the detection signals of the PSDs 26 and 27, and the focus control according to the difference between this position and the actual position of the focus lens by the detection signal of the potentiometer 28. Signal forming motor
Output to 13.

Next, the operating principle of this example will be described in more detail with reference to FIG. In the figure, parts corresponding to those in FIGS. 3 and 5 are designated by the same reference numerals.

In FIG. 6, the optical axes of the projection lens 2 and the light receiving lenses 3 and 4 are parallel to each other, and the light receiving lenses 3 and 4 are arranged on the same plane perpendicular to these optical axes. Assuming that the focal lengths of the light receiving lenses 3 and 4 are f, the PSDs 26 and 27 are provided at positions of a distance f from the light receiving lenses 3 and 4, respectively. Here, when the center of gravity of the light receiving spots on the PSDs 26, 27 when the subject is at infinity is points 26a, 27a, these points 26a, 27a are the light receiving lenses 3,
It is on the optical axis of 4. The light emission center of the light emitting element 1 is on the optical axis of the projection lens 2. Projection lens 2 and light receiving lens 3
Is ₁ and the distance between the projection lens 2 and the light receiving lens 4 is l ₂ .

Now, when a light beam having a circular spot shape is emitted from the light emitting element 1 to a non-contrast object at a distance y, the projection spot 16 of this object is circular. A part of the reflected light beam 17 from the projection spot 16 is received by the light receiving lens 3.
The PSD 26 is radiated through the light source, and a circular light receiving spot is generated on the PSD 26. Similarly, the other part of the reflected light beam 18 from the projection spot 16 passes through the light receiving lens 4 and the PSD 27.
Then, a circular light receiving spot is generated on the PSD 27. Points 26a, 27a at the position of the center of gravity of the light receiving spot on PSDs 26, 27
Assuming that the deviation amounts from x are x ₁ and x ₂ , respectively, these are expressed by equations (1) and (2), as in the case of FIG. So, if you find the difference between these x ₁ and x ₂ , By transforming this, Therefore, the distance y to the subject is obtained.

On the other hand, if the subject has contrast and the projection spot 16 'on this subject is in the shape of a circle with a part missing, the reflected light beams 19, 20 from this projection spot 16' are
Irradiated to SD26 and 27, some light-receiving spots are generated. Assuming that the distance to the object is y, which is the same as in the above case, the center of gravity positions of these light receiving spots deviate in the same direction from the center of gravity positions when the light receiving spots are circular. PSD2
Assuming that the shift amounts of these barycentric positions at 6 and 27 are Δx ₁ and Δx ₂ , respectively, the above equation (15) for the partially missing light receiving spot is as follows.

Also in this case, the equation (6) described in FIG.
x ₁ = Δx ₂ Therefore, the equation (16) is Then it becomes equal to equation (15). In other words, even if the light receiving spots that occur on PSDs 26 and 27 have a circular shape with some parts missing,
By subtracting the amount of deviation of the barycentric position from the points 26a, 27a, the influence of the lack of a part of the light-receiving spot shape is offset, and the distance to the subject can be accurately obtained. Therefore, in FIG. 5, the automatic focusing circuit 12 includes a difference between the detection signals of the PSDs 26 and 27 and an equation (17) for this difference.
There are tables such as a table showing the correspondence relationship with the detection signal from the potentiometer 28 showing the position of the focus lens for focusing on the subject at the distance of
The focus control signal is obtained from the detection signal obtained from the table and the actual detection signal of the potentiometer 28 from the difference between the detection signals of, and the motor 13 is rotated to rotate the focus ring 11 to obtain the focus control signal from the table. The detection signal obtained and the detection signal actually obtained from the potentiometer 28 are made equal to each other. As a result, the focus lens focuses on the subject 15.

According to this example, since the non-scanning type light receiving element is used, there is no movable part, and accuracy and durability are further improved.

FIG. 7 is a block diagram showing an example of an automatic focusing device according to a method different from that of the previous embodiment, in which 29 is a light emitting element holder and 30 is a lens holder, and the same reference numerals are given to the portions corresponding to the above drawings. I am wearing. FIG. 8 is a front view showing a mounting state of the projection lens 2 and the light receiving lenses 3 and 4 in FIG. 1 on the lens holder 30.

In FIGS. 7 and 8, the lens holder 30 has a prismatic shape, a through hole is provided at the center of the side surface, and the projection lens 2 is fitted therein. Further, the light receiving lenses 3 and 4 are attached to both ends of the lens holder 30. The light receiving lenses 3 and 4 have the same relationship as that obtained by cutting out a symmetrical portion with respect to the center of a single lens. Therefore, the light receiving lenses 3 and 4 are arranged symmetrically with respect to the optical axis of the projection lens 2. A light emitting element holder 29 is also fixed to the lens holder 30 so as to face the through hole, and the light emitting element 1 is attached thereto. This light emitting element 1
Are arranged such that their light emission center is on the optical axis of the projection lens 2. The lens holder 30 is non-light transmissive and is painted black, for example.

PSDs 26 and 27 have f as the focal lengths of the light receiving lenses 3 and 4,
The distance is set to (f + p) from the light receiving lenses 4 and 3. However, p is a positive or negative value distance with the focal point of the light receiving lenses 3 and 4 as the origin, and is preferably set to 5 to 15 mm. Further, these PSDs 26 and 27 are provided symmetrically with respect to the optical axis of the projection lens 2.

Now, when a light beam is emitted from the light emitting element 1, this light beam is applied to the subject 15 via the projection lens 2.
A part of the reflected light beam from the subject 15 is applied to the PSD 26 through the light receiving lens 3, and another part of the reflected light beam is applied to the PSD 27 through the light receiving lens 4. This makes PSD
The light receiving spots are generated at 26 and 27, and the detection signals representing the barycentric position of these light receiving spots obtained by PSDs 26 and 27 are supplied to the automatic focusing circuit 12, and the detection signal of the potentiometer 28 is further processed to perform focus control. A signal is formed and output to the motor 13.

Here, the operation principle of this example will be described in detail with reference to FIG.

Now, assuming that the projection spot 16 of AB occurs on the subject when the subject has no contrast, the reflected light beam that has passed through the light receiving lens 3 causes the PSD 26 to have a light receiving spot of the same shape as the projection spot 16. Occurs and the reflected light beam that passes through the light-receiving lens 4 causes PS
D27 has the same light receiving spot as the projection spot 16. Occurs. Here, the light receiving spot Let C ″, C ′ be the center of gravity of, and the distance between these center of gravity C ″, C ′
x ₁

Assuming that the subject at the same distance y has a contrast and a part of the projection spot 16 is cut off to generate a reflected light beam only from the point A, the points A ″ and A ′ are set as the centers of gravity on the PSDs 26 and 27, respectively. A light receiving spot is generated, where the center of gravity A ″, A ′
If the distance between them is x ₂ , then geometrically x ₂ = x ₁ . That is, if the distance y of the subject does not change, regardless of whether or not the subject has contrast (that is, whether or not the shape of the projection spot is partially missing), the distance between the light-receiving spots on the light-receiving elements 26 and 27 is reduced. The distance is constant.

Therefore, in FIG. 7, one of the PSDs 26 and 27, for example, PS
Assuming that the distance between the center of gravity of the light receiving spot of D26 and the optical axis of the projection lens 2 is x, this x is expressed by the following equation.

However, when h = incident height of reflected light beam at the light receiving lens 3, the equation (18) is modified, Then, by finding x, the distance y to the subject 15 is
Can be obtained.

In order to remove the influence of the lack of a part of the projection spot, the distance between the centers of gravity of the light-receiving spots on the PSDs 26, 27 should be obtained, but the light-receiving lenses 3, 4 should be symmetrical with respect to the optical axis of the projection lens 2. Since the PSDs 26 and 27 are arranged at the same distance from the light receiving lenses 4 and 3, the distance between the center of gravity of the light receiving spot on the PSDs 26 and 27 and the optical axis of the projection lens 2 is equal. Therefore, if the distance between the centers of gravity of the light-receiving spots on the PSDs 26, 27 is X, then the distance y to the object 15 is expressed as in the equation (18) as follows.

Similar to the automatic focusing circuit 12 in FIG. 5, the automatic focusing circuit 12 includes a focus lens for focusing the sum of the detection signals of the PSDs 26 and 27 and the subject at the distance of the formula (20) with respect to the sum. There is a table showing the correspondence with the detection signal from the potentiometer 28 showing the position of the PSD 26,
A detection signal is obtained from the sum of the detection signals of 27 by this table, and this is compared with the actual detection signal of the potentiometer 28 to form a focus control signal.

Thus, also in this example, the focused state can be accurately obtained regardless of whether or not the subject has contrast. According to this embodiment, since the projection lens and the light receiving lens are integrated by the holder, the entire structure can be made compact.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, the first
In the embodiments shown in FIGS. 4 and 5, PSDs may be used instead of the two-divided light receiving elements 9 and 10. In this case, a reference point may be provided on the PSD, and the plane parallel plates 5 and 6 may be rotated so that the center of gravity of the light receiving spot coincides with the reference point. Also, in the embodiment of FIG. 1, the plane-parallel plates 5, 6,
The light receiving elements 9 and 10 and the light receiving lenses 3 and 4 may be arranged on the same side of the optical axis of the projection lens 2. In this case, it goes without saying that the difference between the detection signals of the light receiving elements 9 and 10 is used. Also, the fifth
In the illustrated example, the PSDs 26 and 27 may be provided on opposite sides with respect to the optical axis of the projection lens 2. In this case, PSD26,
It goes without saying that the 27 detection signals are added to form a focus control signal as in FIG.

〔The invention's effect〕

As described above, according to the present invention, even if a part of the spot shape of the reflected light beam due to the contrast of the subject is lost, the outputs of the two light receiving elements are simply calculated to achieve the accurate focus state. Can be obtained, the focusing performance can be significantly improved, and since such an error does not occur, the base line length can be shortened and the structure can be made compact.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an automatic focusing device according to the present invention, FIG. 2 is a front view showing a cam of a focus ring and a cam follower pressed against the cam of FIG. 1, and FIG. FIG. 4 is a diagram showing the principle of operation of the embodiment shown in FIG. 4, FIG. 4 is a block diagram showing another embodiment of the automatic focusing device according to the present invention, and FIG. 5 is a view showing the embodiment shown in FIGS. FIG. 6 is a configuration diagram showing an example of an automatic focusing device by a different method, FIG. 6 is a principle diagram of the operation of the example shown in FIG. 5, and FIG. 7 is a method different from the embodiment shown in FIGS. 1 and 4. A block diagram showing an example of an automatic focusing device according to
FIG. 8 is a front view showing how the projection lens and the light-receiving lens in FIG. 7 are attached to the holder, FIG. 9 is an operation principle diagram of the example shown in FIG. 7, and FIG. 10 is a conventional automatic focusing device. FIG. 6 is a diagram for explaining the problem of FIG. 1 ... Light emitting element, 2 ... Projection lens, 3,4 ... Receiving lens, 5,6 ... Parallel plane plate, 5b, 6b ... Arm, 5c, 6c ...
Cam followers, 9,10 ... Light receiving elements, 9a, 9b, 10a, 10b ..
Light receiving part, 11 ... Focus ring, 11a, 11b ... Cam, 12 ...
… Automatic focusing circuit, 13 …… Motor, 15 …… Subject, 21 ……
Slider plate, 21a, 21b, 21c …… Guide groove, 22 …… Cam follower, 23,24 …… Pin, 26,27 …… Light receiving element, 28 …… Potentiometer, 29 …… Light emitting element holder, 30 …… Lens holder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takesuke Maruyama Inventor Takesuke Maruyama 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside Home Appliances Research Laboratory, Hitachi, Ltd. (72) Inventor Takaki Kuda 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa (56) Reference JP-A-60-256112 (JP, A) JP-A-61-251809 (JP, A) JP-A-59-201009 (JP, A) JP-A-59 -202437 (JP, A) JP47-19391 (JP, B1) JP49-17548 (JP, B1)

Claims (1)

[Claims] 1. A light projecting system comprising a projection lens and a light emitting element, a light receiving lens and a light receiving element each having an optical axis parallel to the optical axis of the projection lens in a plane including the optical axis of the projection lens. A light beam is projected from the light projecting system onto a subject, the reflected light from the subject is received by each of the light receiving systems, and the light receiving element receives light according to the light receiving state of each of the light receiving elements. In an automatic focusing device configured to automatically perform focus adjustment by moving a focus lens, in each of the light receiving elements, a position where an optical axis of the light receiving lens passes is set as a center point of each of the light receiving elements, Each light receiving system is provided with a deflecting means for changing the position of the light receiving spot on the light receiving element caused by receiving the reflected light with the movement of the focus lens, and the output signal of the light receiving element for each light receiving system is calculated. A control means for driving the focus lens according to the calculation result and moving the focus lens by the deflection means until the center of gravity of the light receiving spot on each of the light receiving elements coincides with the center point of the light receiving element. An automatic focusing device characterized in that