JPH0697299B2 - Auxiliary projector for focus detection - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary light projecting device for focus detection in a passive automatic focus detecting device used in still cameras, movie cameras and the like.

Conventional technology and its problems Active-type automatic focus detection equipment that projects infrared rays or ultrasonic waves on a subject and receives the reflection to detect the distance to the subject Since the range is greatly limited, in single-lens reflex cameras that also use lenses with long focal lengths, passive autofocus detection devices that directly detect the state of the image based on the external light are mainly used. There is.

However, in this passive type automatic focus detection device,
Focus detection may not be possible when the subject is dark or when the contrast of the subject is low.

Therefore, in order to make up for such a defect, it is conceivable to provide the subject with auxiliary light projection.

At this time, if auxiliary light is simply given as illumination light from a position close to the optical axis of the camera's photographing lens, this illumination light is reflected by the subject and strong specular reflection components and epidermal reflection components return to the camera, Therefore, an auxiliary light projecting device of a type in which a pattern of vertical stripes is projected on a subject and thereby positively contrasts the subject is generally used.

An example is shown in FIGS. 9 and 10.

What is shown here is a camera equipped with a TTL type AF system, and the taking lens 10 also serves as a lens of a focus detection system.

The projection lens 11 has an optical axis l ₁ l _{2 which} is the optical axis L _{1 of the} taking lens 10.
L ₂ is arranged so as to be parallel to the pattern plane 12 arranged in a direction perpendicular to the optical axis l ₁ l ₂ is offset by a predetermined amount upward from the optical axis l ₁ l _2.

A light source (not shown) is arranged behind the pattern surface 12, and the light emitted from the light source is emitted from the pattern surface 12 and the projection lens.
A pattern image 13 is formed at a position C ₁ on the optical axis L ₁ L ₂ via 11. In addition, in FIG. 9, 14 is a film surface.

However, in such a configuration, the subject pattern image 13 is clearly formed only in a very small range near the position C ₁ , and when the subject is out of the range, the pattern image is not formed.
13 becomes out of focus, and it becomes impossible to give contrast to the subject. In this case, F of the projection lens 11
It is possible to increase the focus range of the pattern image 13 by increasing the value and setting the depth of focus deeper, but this reduces the light amount of the pattern image 13 and therefore the focus detectable distance in terms of light amount. The range of is regulated.

In the method shown in FIGS. 9 and 10, the optical axis L ₁
Since L ₂ and the optical axis l ₁ l ₂ are separated, parallax occurs depending on the distance to the subject. Therefore, the actual focusing range is limited to the smaller one of the focusing range limited by the size of the pattern and the focusing range limited by the depth of focus.

Further, as shown in FIGS. 11 and 12, the optical axis l ₁ l ₂ of the light projecting lens 11 is crossed at a position C ₁ on the optical axis L ₁ L ₂ of the taking lens 10 and the pattern surface 13 is illuminated. Provided at a right angle to the axis l ₁ l ₂ , position C ₁
It is also conceivable to form a pattern image 13 that is inclined with respect to the optical axis L ₁ L _{2 at} .

However, in this configuration, the focus range is slightly wider than in the above-mentioned example, but the problem of blurring of the pattern image 13 outside the range still remains.

Therefore, actually, as shown in FIG. 13, a device having two sets of auxiliary light projecting devices of the system shown in FIG. 9 has been put into practical use. With such a configuration, the light emitted from the light source (not shown) forms the pattern image 13 at the position C ₁ on the optical axis L ₁ L ₂ via the pattern surface 12 and the light projecting lens 11, and similarly. light pattern surface 12 emanating from a light source, not Shimese ', the projection lens 11' for forming an pattern image 13 'to a position C ₂ on the optical axis L ₁ L ₂ through.

With this practical model, it is possible to supplement the parallax to extend the focus range to some extent, but this does not fundamentally solve the problem, and the focus positions are the depths of C ₁ and C ₂ as in the previous example. Limited to inside. Moreover, since two sets of light projecting devices are required, there is a limit to miniaturization, not the camera body,
For example, it had to be incorporated into an external strobe device.

In addition, for example, the TTL active AF system applied to the zoom lens for TV is listed in P.457 (47) of Optics Vol. .

In this method, the auxiliary projection is performed through the taking lens, so the focusing range is wide, but an imaging lens suitable for the taking lens must be placed in front of the light emitting element and the light receiving element. However, even if an attempt is made to divert it to a single-lens reflex camera, it has been difficult to use it in a device such as a single-lens reflex camera which is based on lens replacement.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned various problems, and provides a contrast to a subject over a wide distance range by expanding a focusing range of a pattern image projected on the subject. It is also an object of the present invention to provide an auxiliary light projecting device for focus detection which can be incorporated into a camera body by downsizing.

Means for Solving the Problems A first aspect of the invention is to tilt an optical axis of a light projecting lens with respect to an optical axis of a focus detection system and to tilt a pattern surface with respect to a surface orthogonal to the optical axis of the light projecting lens. According to the second aspect of the present invention, the pattern image plane which is conjugate with the pattern surface is formed substantially parallel to the optical axis of the lens of the focus detection system. Provided integrally with the light emitting surface of the light emitting element having a light emission intensity gradient, the optical axis of the light projecting lens is tilted with respect to the optical axis of the focus detection system, and the light emitting surface is formed with respect to the surface orthogonal to the optical axis of the light projecting lens. By tilting the structure, the pattern image plane conjugate with the light emitting surface is formed almost parallel to the optical axis of the lens of the focus detection system, and the light emitting element has a portion where the emission intensity is strong and a portion where the emission intensity is weak and a portion where the emission intensity is weak. Characterized by being arranged to illuminate a short distance

Examples Hereinafter, these inventions will be described with reference to the drawings.

<< First Invention >> FIG. 1 and FIG. 2 show an embodiment of an auxiliary light-projection device for focus detection according to the first invention, which is applied to a camera equipped with a TTL type AF system. Side view of the optical system shown,
FIG.

In both figures, reference numeral 1 is a photographing lens of a camera, which forms an image of a subject (not shown) on the film surface 2 in a focused state, and therefore, based on the focus detection result, the position from the solid line position to the two-dot chain line position or the broken line Driven to position.

The photographing lens 1 also has a function as a lens of a focus detection system, and a part of the light from the subject that has passed through the photographing lens 1 is guided to the focus detection device via a mirror (not shown). Has become. As the focus detection device, various methods such as a contrast detection method or a phase difference detection method can be adopted.

Above the above-mentioned taking lens 1, a light projecting optical unit 3 which constitutes an auxiliary light projecting device for focus detection is arranged.

The light projecting optical unit 3 is integrally composed of a light projecting lens 4, a pattern surface 5, a light source (not shown), and the like.
The respective parts are arranged and configured as follows.

First, the light projecting lens 4 is arranged so that its optical axis l ₁ l ₂ is tilted with respect to the optical axis L ₁ L _{2 of the} taking lens 1, and both axes intersect at a position C ₁ .

The pattern surface 5 is arranged so as to be inclined with respect to the surface 4a orthogonal to the optical axis l ₁ l ₂ of the light projecting lens 4, and the light projecting optical unit 3 constitutes a tilt optical system as a whole. Generally, when the object plane is tilted with respect to a plane orthogonal to the optical axis of the lens, the image plane is formed to be spatially tilted with respect to the object plane according to Shypreef's law. Therefore, also in the light projecting optical unit 3, the pattern image plane 5'which is conjugate with the pattern surface 5 is formed so as to be spatially inclined with respect to the pattern surface 5 as shown in FIG.

Moreover, in this example, since the optical axis L ₁ L ₂ of the taking lens 1 is located on the pattern image plane 5 ′,
The intersection position C ₀ on the extension of the surface 4a orthogonal to the optical axis l ₁ l ₂ and the pattern surface 5 is located on the optical axis L ₁ L ₂ of the taking lens 1.

Further, the pattern surface 5 is provided with a random vertical stripe pattern (dimensions shown) composed of transparent and opaque portions as shown in an enlarged view in FIG.

Then, P _{1 to} P ₄ on the pattern surface 5 are caused by light emitted from a light source (not shown) arranged behind the pattern surface 5.
Each image of P ₁ ′ to P ₄ ′ on the pattern image plane 5 ′,
Additional stripes are aligned with the optical axis L ₁ L ₂ direction on the pattern image surface 5 '.

In this example, the light source described above is adapted to project light in the insensitive wavelength range (low visibility) of the human eye, for example, red light.

Design dimensions of each part related to the projection optical unit 3 shown in FIG.
The S ₁ , S ₂ , S ₃ and the angles θ ₁ , θ ₂ are as shown in the following table, for example.

In the above embodiment configured as described above, when the subject is located on the pattern image plane 5 ', a sharp pattern image with good contrast can always be projected regardless of the distance. Then, the pattern image plane 5 '
Can be enlarged by enlarging the size of the pattern surface 5, and when the illuminance of the light source is increased along with the enlargement, focus detection can be performed as far as the detection capability allows.

Focus detection is performed for a part of the area (distance measuring zone) within the photographing range, and this distance measuring zone is set near the optical axis of the photographing lens in this example. Therefore,
In the above-described embodiment, the optical axis L ₁ L ₂ is located on the pattern image plane 5 ′, which enables accurate focus detection and focus adjustment.

Further, according to the above embodiment, one projection optical unit 3
Since the subject at any position in the distance measuring range can be covered by the device, the device can be made compact, and the light projecting lens 4, the pattern surface 5, and the light source are unitized, and the present invention can be realized. It is also easy to incorporate it in the camera body so as to satisfy the arrangement condition relating to.

In the above embodiment, the projection optical unit 3 is arranged above the taking lens 1. However, this structure is not necessarily required to position the optical axis L ₁ L ₂ on the pattern image plane 5 ′. The same effect can be obtained by arranging the projection optical unit 3 right next to the taking lens 1 as shown in FIG. 5, and the position of the projection optical unit 3 can be arbitrarily set around the taking lens 1. is there.

In addition, as described above, the pattern image plane 5 ′ does not necessarily have to be along the optical axis L ₁ L ₂ , and if a detectable contrast can be given to the object in the distance measuring zone, the optical axis L ₁ L 2 _Even if it is configured so as to intersect with ₂ at one point, or even if it is configured so as to be parallel to the optical axis L ₁ L ₂ , substantially the same effect as the above-mentioned embodiment can be obtained. In this way, in order to change the position of the pattern image plane 5 ', the arrangement position of the light projecting optical unit 3 is changed or the light projecting lens 4 is arranged.
Various means such as changing the angle between the pattern surface 5 and the pattern surface 5 can be considered.

In the above embodiment, only the example in which the distance measuring zone is set in the vicinity of the optical axis L ₁ L ₂ has been described. However, when the distance measuring zone is set in a region other than this, the pattern image plane 5 ′ is used for this distance measuring. The same effect as described above can be obtained by configuring it so as to substantially coincide with the zone.

Further, in the above embodiment, an example in which the present invention is applied to a so-called automatic point-of-use detecting device of a still camera equipped with a TTL type AF system has been described, but it can be applied to a movie camera (TV camera) as well. It can also be applied to a camera in which a photographing optical system and an optical system for focus detection are provided independently.

Furthermore, in the above-mentioned embodiment, an example in which the pattern surface 5 and the light source are provided independently has been described, but it goes without saying that the pattern surface may be integrally formed on the light emitting surface of the light source.

<< 2nd invention >> Next, one Example of 2nd invention is described based on FIGS. 6-8. However, the same members as those of the first embodiment of the present invention described above are designated by the same reference numerals, and the duplicated description will be omitted.

In this optical system, the projection lens 4 is provided above the taking lens 1.
A light projecting optical unit 3 including a light emitting element 6 and an optical axis L ₁ L _{2 of} the taking lens 1 and an optical axis l ₁ l ₂ of the light projecting lens 4 are provided.
It is configured so that and intersect at position C ₁ .

The light emitting element 6 is a light emitting diode in which a pattern surface for forming a pattern image is integrally formed on the light emitting surface 6a, and this light emitting diode is a semiconductor chip as shown in FIG.
Electrode plates 22 and 23 are attached to both surfaces parallel to the PN junction of 21, respectively, and one electrode plate 22 side serves as a light emitting surface.

The light emitting surface 6a of the light emitting element 6 and the surface 4a orthogonal to the optical axis of the light projecting lens 4 are inclined with respect to each other, so that the pattern image plane 6'conjugated to the light emitting surface 6a is spaced from the light emitting surface 6a. It is similar to the above-described first embodiment of the present invention that it is formed to be inclined.

By the way, the amount of light reflected and returned by the subject decreases in inverse proportion to the square of the distance to the subject. Therefore, when the emission intensity of the light emitting element 6 is constant over the entire surface, the distance increases. As a result, the focus detection capability is reduced. Therefore, in this case, the farthest point of the required detection distance is used as a reference, and the output of the light emitting element 6 must be set so as to provide the focus detectable contrast at this farthest point. Then, when set in this way, the loss of the light projection amount at a short distance becomes large.

Therefore, in the focus detection auxiliary light projecting device of the present invention, the light emitting element 6 is provided with a light emission intensity gradient depending on the position of the light emitting surface 6a,
In addition, the above problem is solved by arranging a portion having a high emission intensity to illuminate a long distance and a weak portion to illuminate a short distance. In order to give the light emitting element 6 a light emission intensity gradient, in this example, the current density between the electrode plates 24 and 25 is made different depending on the position of the light emitting surface 6a.

That is, the electrode plate 22 attached to one side of the semiconductor chip 21 is "comb-shaped" as shown enlarged in FIG.
In addition, the terminal 24 is provided on one end side of the electrode plate 22 in the longitudinal direction.
A lead wire 25 extending from is bonded. The electrode plate 23 on the opposite side is a full-scale electrode that is in full contact with one surface of the semiconductor chip 21, and is formed integrally with the terminal 26. In addition,
The size of the electrode plate 22 is shown in FIG. 8 as an example.

Then, these parts are molded with a transparent resin such as acrylic as shown by the chain double-dashed line in FIG. 7, and only a part of the terminals 24, 26 is projected to the outside. A condenser lens section 30 is formed on the exit side surface of this resin layer.

In the shipping diode configured as described above, the terminal 24,
The light emitted from the PN junction surface of the semiconductor chip 21 by applying a voltage to 26 is emitted from the surface of the semiconductor chip 21 on which the electrode plate 22 is provided, and the electrode plate 22 acts as a pattern surface and emits light. The light emitted from the diode is already patterned.

Further, in this light emitting diode, the current density between the electrodes 22 and 23 is different due to the uneven bonding position on the electrode plate 22 or the shape of the electrode plate 22. An intensity gradient occurs depending on the position of 6a.

According to the experimental data, the ratio of the light emission intensity between the brightest part (inside the broken line A in FIG. 8) and the darkest part (also inside the broken line B) is about 2: 1. It can be appropriately set by changing the shape of the plate 22, the bonding position of the lead wire 25, and the like.

By using such a light emitting diode as the light emitting element 6, the brightness of the pattern image plane 6 ′, that is, the brightness of the pattern image projected on the subject can be reduced at a short distance in the above-described auxiliary light projector for focus detection. It can be dark and bright at a long distance. Therefore, it is possible to efficiently utilize the light emission energy of the light emitting element 6 and save energy without lowering the focus detection capability. Moreover, since the light source and the pattern surface are integrated, the light projecting optical unit 3 can be made compact.

Further, by adjusting the light emission intensity gradient of the light emitting element 6 or the arrangement configuration of the light projecting optical unit 3, the contrast of the pattern image in the focus detection device that reads the pattern image on the subject through the taking lens 1 can be adjusted to the distance to the subject. Regardless of this, it can be kept substantially constant, and in this case, the detection accuracy of the focus detection device is made uniform, and the above energy saving is realized in an ideal form.

It should be noted that other actions, effects, and modified examples relating to the arrangement of the light projecting optical unit 3 are the same as those of the above-described first invention, and thus duplicated description will be omitted.

Effect As described above, according to the focus detection auxiliary light projecting device of the first invention, a clear pattern image can be projected onto a subject over a wide distance range, and the camera body is small in size. It can be easily incorporated into, and its effect is extremely large.

Further, according to the auxiliary light projecting device for focus detection according to the second aspect of the invention, in addition to the above effects, the light emission energy of the light emitting element can be efficiently utilized, and energy saving can be achieved. Furthermore, the light source and the pattern surface can be integrated to further reduce the size of the device.

[Brief description of drawings]

1 to 5 show an embodiment of an auxiliary light projecting device for focus detection according to the first invention. FIG. 1 is a side view showing the configuration of an optical system, and FIG. 1 is a perspective view of the optical system shown in FIG. 1, FIG. 3 is an enlarged view showing a basic pattern of the pattern surface shown in FIG. 1, and FIG. 4 is an explanation of specific design numerical examples of the optical system shown in FIG. FIG. 5 is a side view of the optical system shown in FIG. 1, and FIG. 5 is a perspective view showing a modification of the optical system shown in FIG. FIGS. 6 to 8 show an embodiment of the auxiliary light projecting device for focus detection according to the second invention. FIG. 6 is a side view showing the configuration of the optical system, and FIG. FIG. 6 is a perspective view of the light emitting element shown in FIG. 6, and FIG. 8 is a plan view of a light emitting surface of the light emitting element. 9 to 13 show a conventional focus detecting auxiliary light projecting device. FIG. 9 is a side view of an optical system showing a first example thereof, and FIG. 10 is shown in FIG. 11 is a perspective view of the optical system shown.
FIG. 12 is a side view of the optical system showing the second example, FIG. 12 is a perspective view of the optical system shown in FIG. 11, and FIG. 13 is a perspective view of the optical system showing the third example. 1 ... Shooting lens (focus detection system lens) 4 ... Projection lens 5 ... Pattern surface 5 ', 6' ... Pattern image plane 6 ... Light emitting element 6a ... Light emitting surface

Claims (9)

[Claims] 1. A focus detection auxiliary light projecting device having a projection lens for projecting a pattern image onto a subject and a pattern surface for forming a pattern image, and projecting the pattern image onto a detection target of a focus detection system, comprising: The optical axis of the light projecting lens is tilted with respect to the optical axis of the focus detection system, and the pattern surface is tilted with respect to a surface orthogonal to the optical axis of the light projecting lens. An auxiliary light projecting device for focus detection, wherein a flat pattern image plane is formed substantially parallel to the optical axis of the lens of the focus detection system. 2. The auxiliary light projecting device for focus detection according to claim 1, wherein the optical axis of the lens of the focus detection system is located at the pattern image plane or in the vicinity thereof. 3. The auxiliary light projecting device for focus detection according to claim 1, wherein the pattern image plane substantially coincides with a distance measuring zone defined by the focus detection system. . 4. The pattern image is formed by a light source that emits light in a wavelength range insensitive to human eyes or a wavelength range in which sensitivity is low, and a pattern surface on which a required vertical stripe pattern composed of a transparent portion and an opaque portion is formed. The auxiliary light projecting device for focus detection according to claim 1, wherein 5. The focus detecting auxiliary light projecting device according to claim 4, wherein the pattern surface is integrally formed with a light emitting surface of the light source. 6. The light source, the pattern surface, and the light projecting lens constitute a set of optical units, according to claim 4 or 5. Auxiliary projector for focus detection. 7. A lens according to claim 1, wherein the lens of the focus detection system is a photographing lens of a camera.
The auxiliary light projecting device for focus detection according to any one of items 6. 8. A focus detection auxiliary light projecting device having a light projecting lens for projecting a pattern image surface onto a subject and a pattern surface for forming a pattern image, and projecting a pattern image onto a detection target of a focus detection system. The pattern surface is integrally provided on a light emitting surface of a light emitting element having a light emitting intensity gradient depending on the position of the light emitting surface, and the optical axis of the light projecting lens is tilted with respect to the optical axis of the focus detection system,
By forming the light emitting surface by inclining with respect to the surface orthogonal to the optical axis of the light projecting lens, a pattern image plane conjugate with the light emitting surface is formed substantially parallel to the optical axis of the lens of the focus detection system. Further, the auxiliary light projecting device for focus detection is characterized in that the light emitting element is arranged such that a portion having a high emission intensity illuminates a long distance and a portion having a weak emission intensity illuminates a short distance. 9. The light-emitting element is a light-emitting diode in which electrode plates are attached to both surfaces parallel to the PN junction of a semiconductor chip, and one electrode plate side is a light-emitting surface. 9. The auxiliary light projecting device for focus detection according to claim 8, wherein the current densities of the two are different from each other.