JPS61167932A - Auxiliary lighting device for automatic focus detection - Google Patents

Abstract

PURPOSE:To perform automatic focus detection by providing a transparent mold member whose front surface is made into a spherical surface with fine recessed or projection parts where a pattern with contrast is projected and a projection lens arranged in front of the mold member. CONSTITUTION:The projection parts 38 and 40 are formed on the surface of the lens part 36a of the transparent resin mold in a spherical lens shape which faces the projection lens, and the projection parts 38 and 40 are thin and long at right angles to the paper surface crossing the optical axis 36X at right angles while made symmetrically about a plane perpendicular to the paper surface. Further, the breadthwise direction of those projection parts 38 and 40 coincides with the array direction of many photosensors of a CCD line sensor. The angle of total reflecting parts 38a and 40b is set to the angle at which a light beam L3 is reflected totally, and then the light beam is all reflected totally, so there is no light projected from the total reflecting parts, thereby projecting a contrast pattern on a focus detection area. Consequently, even when the contrast of a subject is low, precise focus detection is carried out while the contrast is increased.

Description

[Detailed Description of the Invention] [Production 1] Jsu1 Milk Tray 1 - This invention relates to an auxiliary lighting device for automatic focus detection used with an automatic focus detection device of a camera, and more specifically, to an auxiliary illumination device for automatic focus detection that performs focus detection under constant light. In addition, when the steady light is insufficient for focus detection, an auxiliary light is emitted from an auxiliary illumination device to illuminate the focus detection device 177, and an automatic focus detection device of the camera is capable of performing focus detection under the irradiation of this auxiliary light. The present invention relates to an auxiliary illumination device for automatic focus detection used with the present invention.

Obedience! Conventionally, two images are created by forming two images of the subject light beams that have passed through two areas of the photographic lens that are symmetrical to each other with respect to the optical axis, and the distance between these two images is A camera focus detection device is known that detects the deviation of the imaging plane of a photographing lens from a predetermined focal plane.

The optical system of such a focus detection device has a configuration as shown in Fig. w & 13, and includes a condenser lens at the planned focal plane (F) behind the photographing lens 7 (16) or at a position further behind this plane. (22), and further has re-imaging lenses (26) (2B) behind it, and the imaging plane of each re-imaging lens (26) (28) is equipped with a line sensor (30a) using COD, for example. (30b) is arranged. As shown in FIG. 14, the images on each sensor (30a) (30b) are mutually related to the optical axis (18
) side, and on the other hand, in the case of the rear bin, the optical axis (18
). When in focus, the distance between two corresponding points of the two images is a specific distance defined by the configuration of the optical system of the focus detection device.

Therefore, in principle, the focus state can be determined by detecting the distance between the two images. The following method is known as one of the methods for detecting this image interval.

This known method will be explained with reference to FIG.

In FIG. 15, fin sensors (30a) (30b)
each consists of, for example, 10 and 1716 7-otodiode cells al-alQ,b,~bus-
do. For convenience, it is assumed that the symbols attached to each cell also represent the output of each cell. Here, the line sensor (30b)
If we consider a set of 10 consecutive cells, seven sets B1, B2, . . . B7 are formed as shown in the figure. The focus state is determined by detecting which of these seven sets of images most closely matches the image of the line sensor (30a). For example, assume that the image of the line sensor (30a) matches the image of the group B of the line sensor (3ob). In other words, cells al, as, φ...φa
each output of le and cells b1, b2,...bl. al=bl, @, =l)2, e e e
It is assumed that the relationship e' @ Io = b r o holds true. In this case, 5l=Ial-bl l +
Ia2 b21 + ” '---za+o-1)
,. l=Q-(i), but S is smaller than similar calculation results for images of groups other than group B1, and is the smallest among the results of calculations for all images of groups. In order to find the slope that takes such a minimum value, the above calculation is first performed for each set of images. Next, an operation is performed to find the minimum value from among the obtained calculation results.

In this way, the focus state was detected.

However, in the above-described apparatus, the output of the light-receiving element decreases as the brightness of the object decreases, and if the focus detection object is too dark, focus detection becomes impossible or accuracy deteriorates. Therefore, when the subject is dark, it is conceivable to illuminate the focus detection target to increase its brightness. In other words, an illumination device for automatic focus detection is required. Such an auxiliary illumination device for automatic focus detection is disclosed, for example, in U.S. Pat. No. 4,150.8.
Various proposals have been made in the specification of No. 88 and Japanese Unexamined Patent Publication No. 73709/1988.

According to the present invention, in the automatic focus detection device as described above,
This was done in view of the drawback that focus detection becomes impossible or accuracy deteriorates not only when the brightness of the focus detection target is low, but also when the contrast of the focus detection target is low. Generally, the reflectance of an object tends to increase in the infrared wavelength range compared to the visible wavelength range, but conversely the contrast decreases as the infrared wavelength range approaches, so auxiliary illumination light is This problem of low contrast is particularly exacerbated when using light in the infrared wavelength range to avoid harmful effects. SUMMARY OF THE INVENTION An object of the present invention is to provide an auxiliary illumination device for automatic focus detection with a simple and compact configuration that enables automatic focus detection without deteriorating focus detection accuracy even when the contrast of the focus detection target is low. It is in.

In order to achieve the above object, the auxiliary lighting device for automatic focus detection according to the present invention includes a light emitting diode, a molded light emitting diode, and a pattern with contrast projected onto the focus detection area. The W feature is that it has a transparent mold member formed on the front surface of a spherical surface having a minute opening or convex portion, and a projection lens placed in front of the mold member.

Therefore, the light emitted from the light-emitting diode is projected onto the focus detection target via the mold member and the projection lens, and a fund last pattern corresponding to the shape of the four parts or convex parts of the mold member is projected onto the focus detection target. Therefore, even when the contrast of the focus detection object itself is low, highly accurate focus detection is possible. Since the contrast pattern is formed by the four parts or convex parts on the spherical surface of the mold member, there is no need to provide a separate member to project this contrast pattern, simplifying the configuration of the auxiliary illumination device for automatic focus detection. And it can be made compact.

K1 Ran Below, embodiments of the present invention will be described. FIG. 1 is a schematic diagram showing an automatic focus detection system in which an auxiliary illumination device for automatic focus detection according to an embodiment of the present invention is provided in an electronic flash device for flash photography. In Fig. 1, (C) is a camera body of a single-lens 7-lens camera with a main mirror (Ml), (EL) is a photographing lens that can be attached to and detached from the camera body (C), and (S) is the camera body (C). ) shows a removable electronic flash device. Electronic flash device (S
) is attached to the accessory rack (2) provided on the top surface of the camera body (C) with its legs (4), and is a known flash light emitting device 7? Along with the tube (6), an auxiliary illumination device (A S ) for automatic focus detection having a pair of light emitting diodes (8) (10) and a pair of projection lenses (12) (14), which will be described later, is built in.

Furthermore, the electronic flash device (S) includes a 7-flash flash circuit including a well-known booster circuit, main capacitor, and one tri-circuit, as well as an auxiliary lighting device for automatic focus detection (AS).
) is also provided with a circuit for causing the pair of light emitting diodes (8) (1'0) to emit light.

A circuit for causing the light emitting diodes (8) and (10) to emit light is configured to cause the light emitting diodes (8) to emit light during focus detection operation of the camera.
) (10) can be caused to emit light as necessary prior to the exposure operation (The details thereof are not related to the gist of the present invention and will not be described here. Note that the light emitting diodes (8) and (10) It is constructed to emit light in the infrared wavelength range so as not to irritate the human eye.

The camera body (C) has a main mirror (Ml) and a sub mirror (M2), and the lens system (1
6) passes through the light-transmitting portion of the main mirror (Ml), is reflected downward by the sub-mirror (M2), and enters the focus detection device (F). (18) indicates the optical axis of the photographic lens (EL).

FIG. 2 shows the optical arrangement of the focus detection device (F) within the camera body (C) of this embodiment. In Figure 2, (20
) is provided in the focus detection device (F) and the focus detection device (
(22) is a condenser lens, (24) is an optical path refraction mirror, (26) (2)
8) is a pair of re-imaging lenses, (30) is, for example, a COD
It is an integral type light-receiving element as shown in Fig. 13 and 1.
The line sensors (30a) and (30b) shown in FIG. 5 are integrated. (32) indicates the film surface. The developed view of the optical system of this focus detection device (F) is almost the same as that shown in FIG. 13, and the focus detection principle is also the same as that described above, so a description thereof will be omitted.

Fig. 3 is a perspective view showing the main parts of the auxiliary illumination device (A S ).
are arranged parallel to each other and spaced apart. (8) and (10) are projection lenses (12) respectively.
(14) A light emitting element placed behind the optical axis (8).
X) (IOX) is the distance # from the projection lens (12) (14)
They are arranged so as to intersect with each other at positions separated by lL. That is, the light emitting elements (8) and (10) each have a mold part (8a) (10 m) having a spherical surface on the front surface,
The center of the spherical surface is the projection lens optical axis (12X) (14X)
However, they are separated by a distance d in opposite directions. If the radii of curvature of the spherical surfaces of the mold parts (8a) and (10a) are r and 2, respectively, then r+ > r2.In the vertical direction of the figure (direction perpendicular to the optical axis of the photographic lens), , the center of both spherical surfaces is the difference in radius of curvature δ(=rl−r2
) and are arranged so that the lower ends of both spherical surfaces coincide with each other. Therefore, the illumination area (A) by the light emitting element (8) and the illumination area (B) by the light emitting element (10)
As shown in the figure, the upper ends always coincide with each other, and the illumination area (B) is included in the illumination area (A).

On the front of the mold parts (8a) (10a), respectively,
A pair of minute four parts (9) (11), (13) (
15) are integrally formed. This will be detailed later.

Figure 4 shows these illumination light fluxes and the optical axis of the photographing lens (18).
FIG. In the figure, φN represents the light flux emitted from the light emitting element (8) having a spherical surface with a radius of "1", and φF represents a light flux emitted from the mold portion (8a) having a spherical surface with a radius of "r2".
10a) shows the luminous flux emitted from the light emitting element (10). As described above, since the lower ends of both spherical surfaces are made to coincide, the upper ends of the illumination light beams φN1 to φF are made to coincide with each other. And since rl > r2, the luminous flux φN
The spread of is larger than the spread of the luminous flux φF. Therefore, the lower ends of both light beams φN and φF are shifted from each other.

That is, the light flux φN illuminates the focus detection area (Y) whose distance in the optical axis (18) direction from the illumination device is farther than 18, while the light flux φF illuminates the focus detection area (Y) whose distance in the direction of the optical axis (18) from the illumination device is farther than IF. Area (Y) is illuminated.

Therefore, the focus detection area (Y) further away than IF is illuminated by both light beams φN1φF, and the focus detection area (Y) from IN to IF is illuminated only by the light beam φN. In this way, when the focus detection target is located at a relatively long distance and the amount of light incident on the focus detection device (F) tends to be small, the focus detection target can be detected using strong light that is the superposition of both light beams φN1φF. When the focus detection target is under relatively close pressure @ (darkness from IN to IF), where the amount of light entering the focus detection module (8) tends to be relatively large as well as illuminating, the focus detection target is Since the illumination is performed with only a weak light beam φN, the focus detection target can be well illuminated and accurate focus detection can be performed regardless of whether the focus detection target is located at a short distance or a long distance.

! Figure @5 is a sectional view of main parts showing the configuration of the light emitting elements (8) and (10). In the same figure, (34) is (8) (10
), in which (36) is a mold molded from colorless and transparent epoxy resin, etc., and the above-mentioned mold parts (8a) and (10a) are shown in the front part.
A lens portion (36a) having a spherical surface corresponding to the spherical surface is formed. On this spherical surface, a pair of contrast pattern projection projections (
38) and (40) are integrally formed. Seven frames (not shown) are fixed inside the mold (36), and four conical parts (42) are formed on the front surface of the frame.

A highly reflective material such as gold or silver is deposited on the inner surface of the recess (42) to increase the reflectance.

When this frame is fixed to the mold (36), the fourth part (42) is attached to the optical axis (36X) of the lens part (36a).
) is located at a rotationally symmetrical position with respect to Further, this recess (42) has a conical shape with a narrower bottom.

At the bottom of this fourth part (42) is a lens part (36a).
) A light emitting diode (44) is fixed so as to be located on the optical axis (36X) of the light emitting diode (44). The light emitting diode (44
) emits light from its top surface (44a) and side surface (44b), and is attached to the bottom of the four parts (42) with a tape or the like. (46) is the above-mentioned (12)
) This is a projection lens that corresponds to (14).

By configuring in this way, light emitting diodes (4
4) Efficiently illuminate the focus detection target by projecting not only the light emitted from the top surface (44a) (hereinafter referred to as top light) but also the light emitted from the side surface (44b) (hereinafter referred to as side light) can do.

FIG. 6 is an enlarged partial sectional view of the light emitting element (34).

In the same figure, (36a) is a transparent I in the shape of a spherical lens.
f The upper molded lens part has convex parts (38) and (40) shaped as shown in the figure on its surface facing the projection lens.
is provided. The convex portions (38) and (40) are aligned with the optical axis (36).
They are symmetrical to each other with respect to a plane perpendicular to the plane of the paper and are elongated in the direction perpendicular to the plane of the paper.

Furthermore, the width direction (horizontal direction in the figure) of the convex portions (38) and (40) corresponds to the array direction of a large number of CCD line sensors (7-r) arranged in the focus detection device (F) of the camera. Match. The convex portions (38) and (40) are, respectively, light transmitting portions (38a) (40a) consisting of flat surfaces and total reflection portions (38b) (38c) (40b) consisting of inclined surfaces.
) (40c). Reference numeral (44) denotes a light emitting diode which is a light source, and from its top and side surfaces light of a wavelength determined by its material is emitted.

(L,) is the optical axis (
36X If the angle between the normal line of the total reflection part (40b) of 40) is θ, the angle α measured from the axis (P) perpendicular to the optical axis (36X) of the total reflection part (40b) is α= It is expressed as θ+β1. Here, the light #i (L,) is reflected at the total reflection part (4
Ob) When determining the conditions for total reflection, when the dimensions of each part are determined as shown in Figure 6, and when the refractive index N' of the transparent resin mold is 1.5, θ≧42°. .

On the other hand, (L2) is emitted from the most end of the upper surface of the light emitting diode (44), and the convex portion (38)
The figure shows the light rays incident on the total reflection section (38b) of FIG. Among the light rays emitted from the upper surface of the light emitting diode (44), the θ of this light M (L2) is the smallest. (L3) is emitted from the side of the light emitting diode (44), and is emitted from the four parts (44).
2) and enters the total reflection part (38b) of the convex part (38) at an angle that maximizes the angle β3 between the axis parallel to the optical axis (36X), and at this time θ becomes the smallest.

Here, as is clear from the figure, there is a relationship β, 〉β2〉β1. Therefore, if the angles of the total reflection parts (38b) and (40b) are set at such an angle that the light ray (L) is totally reflected, all other light rays as mentioned above will also be totally reflected. No light rays are emitted from this total reflection part, and this part when observed through the projection lens appears as a dark line, that is, a contrast pattern is projected onto the focus detection area.

As an example, the width of the chip of the light emitting diode (44) in the direction perpendicular to the optical axis is 400 μm, and the width of the recess (4
2) The length to the reflective part is 500 μm, and the light emitting diode (
44) The length from the top surface to the apex of the lens part (36a) is 1.9 mm, and the radius of curvature of the spherical surface of the lens part is ILI1.
16, and when calculating the conditions for total reflection when the dimensions of the convex portions (38) and (40) are as shown in the figure, β, = 23.5°, and α≧42° + 23,5 °=65.5°.

FIG. 7 shows a projected image formed by the optical system of FIG. 6. (50) is the spread of the entire projected image, which includes the slopes (total reflection part (38b)) of the convex parts (38) and (40) formed on the front surface of the lens part (36a).
(38c), (40b), and (40c)), dark lines (52) and (54) are formed.

(52) is a dark line corresponding to the total reflection part (38c), and (54) is a dark line corresponding to the total reflection part (38b). (56) is the bright part of the opening, which corresponds to the light transmitting part (38a).

FIG. 8 shows another embodiment in which the number of convex portions is further increased in order to increase the number of main dark lines. In this example, four convex parts (
58), (60), (62), and (64) are formed symmetrically about the optical axis (X). The total reflection part of the convex part (58) is (
ssb) and the total reflection portion of the convex portion (62) is (62b), then (62b) is formed to be closer to parallel to the optical axis (X). This depends on the total internal reflection conditions mentioned above. On the other hand, the angle (corresponding to α) of the total reflection part and its height (indicated by 11 in the figure) determine the width of the dark line when projected, so they can be designed as necessary. The dimensions of each part of this example are shown in the figure.

FIG. 9 is an enlarged sectional view showing still another embodiment of the present invention. In the same figure, (66) to (78) are a plurality of protrusions formed along the surface of the lens part (36a) so that the cross-sectional shape becomes a semicircle, and the semicircle is the same as that of the lens part. Total reflection occurs near the intersection with the surface of (36 m), producing the same effect as the previous embodiment. FIG. 10 shows a front view of the light emitting device of FIG. 9.

FIG. 11 is a sectional view of a main part showing an example in which the angle a of the total reflection part of each protrusion (80) to (96) is 90°, and is intended to project a large number of thin dark lines. . Therefore,
The tip surfaces (light transmitting parts) of each of the protrusions (80) to (96) are in contact with a circle having a radius R2 larger than the radius of curvature R1 of the lens part (36g). In this case, the width of each protrusion in the direction perpendicular to the optical axis (X) is preferably about 0.11 to 0.2 mm.
Such minute protrusions can be easily manufactured by making a mold using electrical discharge machining. FIG. 12 is a front view of the light emitting element of this example.

In all of the above embodiments, a protrusion or a convex part was integrally formed on the lens part for projecting a contrast pattern, but the present invention is not limited to this. It may be configured such that a contrast pattern is projected by forming four parts in the area.Furthermore, in the above embodiment, the configuration is such that a contrast pattern in the form of a combination of light and dark is projected onto all focus detection areas. However, the present invention is not limited to this, and the contrast pattern projected on the focus detection area may be determined according to the characteristics of the focus detection device.

As described in detail above, the present invention provides an auxiliary lighting device for automatic focus detection for illuminating a focus detection area viewed by an automatic focus detection device provided in a camera, which includes a light emitting diode and a light emitting diode. In addition to molding the diode, a transparent mold member having a spherical surface having minute convex portions or four parts formed on its front surface for projecting a contrasting pattern onto a focus detection area, and a transparent mold member placed in front of the mold member. With this configuration, even when the contrast of the subject is low, the contrast can be increased to enable accurate focus detection. For this purpose, it is only necessary to integrally provide a minute convex or concave portion on the spherical surface of the molded member of the auxiliary illumination device for the object illumination m, so the configuration is simple, and another member is required for contrast projection. Since there is no need to arrange the auxiliary lighting device, the configuration of the auxiliary lighting device itself can be made compact. Furthermore, according to the present invention, even when projecting light in the infrared wavelength range toward a subject so as not to irritate human clothing, it is possible to increase the contrast of the subject detected by the automatic focus detection device. It is possible to widen the distance range in which focus can be detected and lower the limit of low contrast.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the arrangement of the point detection optical system of a camera system in which an auxiliary illumination device for automatic focus detection according to an embodiment of the present invention is built into an electronic flash device, and FIG. 3 is a sectional view showing the arrangement of an optical system for automatic focus detection according to an embodiment of the present invention. 4 is a schematic diagram showing the illumination luminous flux, FIG. 5 is a sectional view showing the auxiliary lighting device according to the first embodiment of the present invention, and FIG. 6 is a diagram showing the light emitting element of the auxiliary lighting device. FIG. 7 is a schematic diagram showing the projected contrast pattern; FIG. 8 is a schematic diagram showing the essential parts of the light emitting element of the second embodiment of the present invention; FIG. 9 is a schematic diagram showing the main part of the light emitting element of the second embodiment of the present invention FIG. 10 is a front view thereof, FIG. 11 is a sectional view showing essential parts of a light emitting device according to a fourth embodiment of the present invention, and FIG. Its front view, FIG. 13 is a schematic diagram for explaining the arrangement of the focus detection optical system of the automatic focus detection device used in the camera system of the embodiment of the present invention, and FIG. 14 is a schematic diagram for explaining the principle thereof. ,tjS15
The figure is a schematic diagram showing the CCD sensor. (8a) (10a) (36); Mold member, (9ri (
11) (13) (15) (38) (40) (58) IQ
A, 11ry t=yry 0110 rsl/Q
9) IQ A ltΩa) (88) (90) (92) (
94) (96); Minute convex or concave portion, (12) (14) (46); Projection lens, (36a);
Spherical surface of mold member (44); Light emitting diode. Applicant Minolta Camera Co., Ltd. Figure 3 L cL Figure 5 Figure q Figure 2 Figure 6 Figure 9 Figure 70 *++ Figure 12 Figure 13 Figure 74

Claims (1)

[Claims] 1. An auxiliary lighting device for automatic focus detection for illuminating a focus detection area viewed by an automatic focus detection device provided in a camera, comprising: a light emitting diode; A transparent mold member having a front surface formed with a spherical surface having minute convex portions or concave portions for projecting a contrasting pattern onto a detection area, and a projection lens disposed in front of the mold member. An auxiliary illumination device for automatic focus detection featuring: 2. A patent claim characterized in that the convex portion or the concave portion has a total reflection surface that totally reflects the light from the light emitting diode and a light transmission surface that transmits the light from the light emitting diode and guides it to the projection lens. The auxiliary illumination device for automatic focus detection according to item 1.