JPH0677100B2 - Illumination optical system for focus detection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention projects illumination light onto a subject and focuses on the reflected light when automatic focus detection is not possible due to insufficient light amount from the subject such as at night. The present invention relates to an illumination optical system for focus detection that enables detection.

[Problems to be Solved by the Invention] As an illumination optical system for focus detection of this type, US Pat.
In JP 150,888, an illumination optical system for projecting a relatively narrow illumination beam is arranged at a predetermined distance from the optical axis of the taking lens, and the beam is short-distance from the far side on the optical axis of the taking lens. Alternatively, it has been proposed to swing in the opposite direction. In this configuration, in order to secure the beam intensity on the far side, the light beam is condensed relatively thinly, and when it is condensed thinly, it is not illuminated as it is. However, in addition to the need for a mechanism for oscillating the light beam, a mechanism for interlocking with the taking lens is also required, and the mechanism is inevitably complicated, and it is not possible to support various interchangeable lenses. There is a problem that it is extremely difficult, if not possible.

Further, U.S. Pat. No. 4,394,077 proposes a system in which an illumination optical system is arranged in a photographing lens barrel of a camera and the direction of a projection beam is changed according to the extension of the photographing lens.

Even in this structure, the interlocking mechanism between the illumination optical system and the extension of the taking lens is still necessary, and since the illumination optical system must be built in for each interchangeable lens, the interchangeable lens does not have to be large in diameter or complicated. There is a problem that the cost cannot be increased.

By the way, in order to avoid the problems of the conventional focus detection illumination optical system, it is sufficient to always project the distance measurement area from a fixed direction without shaking the illumination light.
In order to effectively illuminate the far distance side, it is necessary to make the light source too bright or to narrow down the illumination beam.The former is difficult due to the restrictions of the power source, etc. Since the side is not illuminated, focus detection on the near side cannot be performed. In particular, in the case of a structure such as a single-lens reflex camera in which the taking lens barrel is largely projected forward with respect to the camera body, it is not possible to block the illumination light by the lens barrel when the above-mentioned illumination optical system is built in the camera body side. Because it is difficult, even if it is arranged, it will be located far from the optical axis of the shooting lens, so it will be installed on the strobe device side, but in that case, the distance from the optical axis of the shooting becomes large. The above limitation on the short distance side becomes a big problem.

[Means for Solving the Problem] The present invention can illuminate a far-distance side effectively without swinging illumination light, and illuminates a near-distance side so that focus detection can be performed to a sufficiently short distance. To provide an illumination optical system for illumination detection which is capable of
Including the focus detection area of the focus detection system built into the camera, the illumination light is projected with a vertical spread that is sufficiently larger than the vertical width of the focus detection area, and an intensity distribution is given to the projected illumination light itself. The basic feature is that the intensity distribution providing means is provided in the illumination optical system.

The intensity distribution providing means has a configuration for providing intensity distribution that gradually increases from the short distance side to the long distance side to the illumination light projected from the long distance side to the short distance side.

With the above configuration, even if the spread of the illumination light is relatively large, most of the light energy can be concentrated on the far distance side, so even if the light energy is not so large, the far distance subject can be efficiently illuminated. In addition, the incident intensity of the reflected light from the subject can be substantially equalized on the long distance side and the short distance side.

[Examples] Examples of the present invention will be specifically described below together with the background of the present invention.

FIG. 4 shows the overall configuration of the system, which should be called the background of the present invention, in which the focus detection module 3 receives an object image incident from the taking lens 2 supported on the front surface of the camera body 1, When an auxiliary illumination optical system 5 for focus detection is provided in a strobe device 4 attached to a camera having a built-in automatic focus detection device that performs focus detection based on received light data, and the subject light amount is insufficient at night In addition, it has a basic configuration in which the illumination light is projected from the auxiliary illumination optical system 5 onto a subject, and focus detection can be performed by the reflected light.

The detection module 3 has a distance measuring area defined by two solid lines Su and Sl that are symmetrical with respect to the optical axis OA of the taking lens 2, and focus detection can be performed within this distance measuring area.

On the other hand, the auxiliary illumination optical system 5 is supported at a position separated from the optical axis OA of the taking lens 2 by a distance B while the strobe device 4 is set in the camera, and its optical axis OB is aligned with the optical axis OA of the taking lens 2. On the other hand, they are set so that they intersect at a relatively small angle θ. The luminous flux of the illumination light is the dotted line Ru, R
It has a divergence angle defined by l.

As a result of the above basic configuration, as shown schematically in FIG.
The optical axis OA of the taking lens 2 and the optical axis OB of the auxiliary illumination optical system 5 intersect at the point Lmean from the focal plane of the camera, and the divergence angle of the illumination light is defined by Su, S1 that defines the distance measurement area. Distances Lmax and Lmin to the positions where the specified Ru and Rl intersect, respectively.
In the range of distance (Lmax-Lmin = 1), the distance measuring area and the illumination light overlap. Therefore,
If the distance range of approximately Lmin to Lmax is a range that can be illuminated by the illumination light, and the intensity of the illumination light is sufficient over the entire range, focus detection within this range is possible.

The distances Lmin, Lmean, L are shown in FIGS. 6 (a), (b) and (c).
The relationship with the spread 7 of the illumination light in the distance measuring area 6 at max is shown as a schematic sectional view. As is clear from these figures, the distance measuring area 6 overlaps the lower side of the illumination light spread 7 at the distance Lmin, whereas the distance measuring area 6 spreads the illumination light spread 7 at the distance Lmax. Shows a distance dependence such that the wrap position changes in the vertical direction according to the distance, whereas the two do not eccentric in the horizontal direction. Therefore, in order to sufficiently secure the distance range l (= Lmax-Lmin) in which distance measurement is possible, it is necessary to increase the spread of the illumination light in the vertical direction, and the spread shape of the illumination light (in a certain vertical cross section). Is most preferably a vertically long rectangular shape, and by this shape,
It is understood that the distance range 1 capable of distance measurement can be secured while maintaining the lap state in the left-right direction with the minimum expansion area.

By the way, if B is 108 mm, Lmin = 0.6 m, Lmax = 7 m, and the spread of the distance measurement area 6 is upper / lower ± 0.2 °, left / right ± 1.3 °, the illumination light 7 spreads left and right. It is ± 1.5 °, but upper and lower ± 4 ° are required.

On the other hand, as is well known, the intensity of the illumination light decreases with the square of the distance from the light source. Therefore, as shown in FIG. 6C, the distance measurement area 6 and the illumination light 7 are at the distance Lmax. Even if it is possible to secure the wrap with the above, if the light intensity in the lap portion is not sufficient, the amount of light reflected from the subject is insufficient and effective focus detection cannot be performed. Certainly, if the light source has a large output, such a problem does not occur, but the power source built in the strobe device 4 consumes a large amount of power each time the strobe emits light. There is no power available.

In consideration of such power restrictions, the illumination light is given an intensity distribution as shown by the curve I in FIG.
In ax, it is most preferable to overlap the distance measuring area 6 at the portion where the intensity of the illumination light reaches its peak.

Summarizing the above, it can be understood that the most efficient illumination light is one that exhibits a vertically long rectangular spread and has an intensity distribution having a peak at the upper portion in the up and down direction.

FIG. 1 shows an embodiment of an auxiliary illumination optical system suitable for the present invention.

In FIG. 1, 8 is a light source, 9 is a projection lens, 10 is a transparent panel for protection arranged in front of the projection lens 9, and a prism 11 is integrally formed on a part thereof. The light source 8 preferably has a structure in which a light emitting diode (LED) that emits visible light having a long wavelength (for example, about 700 nm) is molded with a transparent resin, and a hemispherical lens 8a is provided in a portion facing the projection lens 9. Has been formed. The projection lens 9 is adjusted in the optical axis direction so as to form an image of the hemispherical lens 8a at a distance of 5 m, for example. The position indicated by a virtual line 12 in the figure is the conjugate position corresponding to the distance of 5 m. The light emitted from the light source 8 is condensed by the hemispherical lens 8a, refracted by the projection lens 9, and the protective panel 10 is provided.
It is projected on the subject side through the parallel part of. Ray e _u ~ e _l
The range of is the range of its spread. In addition, the projection lens 9
After transmitting refracting, light incident on the prism 11 is deflected downward by the prism action is projected to the object side in the spread of f _u ~f _l. Since the light intensity of the spread from f _{u to} f _l is determined by the area of the prism 11, it can be set to be weaker than the intensity of the light passing through the parallel portion of the protection panel 10 by adjusting it appropriately.

FIG. 2 shows an optical path diagram of a projection light beam by the auxiliary illumination optical system of FIG. 1, and shows respective light rays e _u , e _l , f _u ,
f _l has a one-to-one correspondence with those in FIG. Prism 11
The rays f _l deflected by the rays do not pass through the prism 11, that is, the rays e _u that have passed through the parallel part of the panel 10 and 1 m
It intersects in the vicinity, and is deflected so that it overlaps above it.

FIG. 3 is a sectional view of the luminous flux of FIG. 2 at a distance of 1 m,
Reference numeral 13 is an optical image of light transmitted through the parallel portion of the protection-like panel 10, and 14 is a light source of light transmitted through and refracted by the prism 11. The light image center of the hemispherical lens (8a) formed by the light polarized by the prism 11 can be located below the light image 13 by V, but only the crescent-shaped portion (area indicated by width v) is projected for the reason described later. , It becomes a light image of the shape as shown in the figure.

Therefore, by using the prism 11 as the deflecting member, as the actual illumination light, the light image 13 by the light flux emitted from the entire area of the hemispherical lens 8a and passing through the parallel portion of the protective panel 10 and the hemispherical lens 8a. The light image 14 emitted from a part of the light and transmitted and refracted through the prism 11 has a superposed spread, and the vertical direction (vertical direction) is longer than the horizontal direction, and the upper side that is involved in illumination on the far distance side. Illumination light having an intensity distribution in which the light intensity of the portion 13 is higher than the light intensity of the lower portion 14 involved in the illumination on the short distance side is obtained.

FIG. 7 is a detailed optical path diagram for explaining the above phenomenon.
Rays emitted from LED15 is light is bent in the direction of the projection lens 17 in the hemispherical lens 16, but now, the prism portion 19 of the panel 18 as shown in FIG. 8 is the projection lens 17 from the optical axis of H _{Y Suppose} that the light is formed with a width of h _{X in} the horizontal direction and h _{Y in} the vertical direction, and consider a ray that passes through this portion. LED15
Consider the light emitted from a point on the optical axis of. Ray a _H is prism 19
Among the light rays that pass through, the light ray that passes through the uppermost part of the spherical surface portion of the hemispherical lens 16, and the light ray a _L is the light ray that passes through the lowermost surface side of the spherical surface portion among the light rays that pass through the prism 19. Similarly, for light emitted from a point at a distance Y from the optical axis, b _H is a ray passing through the uppermost part of the spherical portion of the hemispherical lens 16 and b _L is passing through the lowermost side of the spherical portion of the hemispherical lens 16. Is a ray. LE
The size of D15 is sufficiently smaller than the diameter of the hemispherical lens 16 (the actual size of the chip is at most about 0.5 mm), and it is relatively close to the center of the hemispherical lens (taken out from the projection lens 17). If you try to maximize the amount of light that can be obtained, it will be such a dimension.) Even if you consider points other than the optical axis, the light that passes through the prism 19 passes through part of the hemispherical lens 16 (approximately the upper half in the figure). It is limited to the light.
Light that has passed through the lower side of the hemispherical lens 16 like the light ray c is a prism
I can't enter 19. Therefore, the light beam projected to the subject side through the prism 19 is a hemispherical lens 16 as shown by 14 in FIG.
The shape corresponds to a part of.

FIG. 8 is a diagram showing the positional relationship between the projection lens 17 and the prism 19, which is set to be sufficiently longer than the horizontal width h _X and vertical h _Y of the prism 19 and the hemispherical lens 16 in the horizontal direction. It is possible to capture light that has passed through all parts in the width direction.

FIG. 9 shows an embodiment in which the prism 19 is displaced in the direction perpendicular to the optical axis in FIG. 7 (H _Y = 0) in order to explain the relationship between the position of the prism 19 and the optical image. Similarly to FIG. 7, the light ray a _H is the light passing through the prism 19 and passes through the uppermost side of the hemispherical lens 16, and the light ray a _L passes through the lowermost side thereof. Of entirely same for light emitted from the Y point outside the optical axis, b _H passes through the uppermost hemispherical lens 16, b _L is a light beam passing through the lowermost hemispherical lens 16. The light beam passage area on the hemispherical lens is slightly lower than that in FIG.

10 (a), (b), and (c) respectively show the position of the prism 19 in the direction perpendicular to the optical axis (vertical position) and the optical image 14 formed by the prism 19 (for example, in FIG. FIG. 10 (a) to (c) shows the optical image as the position H _{Y of the} prism 19 is lowered.
Move like. The state of FIG. 10 (a) corresponds to the case of FIG. 7 (H _Y > 0), and the state of FIG. 10 (b) corresponds to the case of FIG. 9 (H _Y = 0). The state of FIG. 7C corresponds to the case where H _Y <0.

FIG. 11 (a) shows the relationship between the prism and the optical image in the case of the moistening model shown in FIG. 11 (b), in which the vertical center position D of the prism and its vertical width d are changed. 9 is a graph showing a change of an effective area (range of passing a prism) on a hemispherical lens surface due to the above. Rmax is a ray that passes through the uppermost side on the hemispherical lens surface, Rmin is a ray that passes through the lowermost side, and the area between them is the effective area.

FIG. 12 (a) shows the angle α of the prism shown in FIG. 12 (b).
4 is a graph showing the relationship between the deviation angle θ (corresponding to V in FIG. 3). As explained in FIG. 2, if it is decided at what distance (if the closest distance is determined) at which the light flux passing through the prism and the light flux not passing therethrough are overlapped,
It is possible to determine the angle, size, and position of the prism from the graphs of FIG. (A) and FIG. 12 (a).

FIG. 13 shows another embodiment of the present invention. In the figure, 20 is a resin-molded LED, 21 is a projection lens, and 22 is a protective panel. The protective panel 22 has a prism 23 having an angle α and a prism 24 having an angle β smaller than that, which are formed in two stages in the vertical direction as shown in the drawing. FIG. 14 shows an optical path diagram of projection light in that case. Rays Pu and Pl are the spread range of the light flux transmitted through the parallel area of the panel, and the rays qu and
ql is the spread range of the light beam transmitted through the prism 23 and deflected, and the light beams su and sl are the spread range of the light beam transmitted through the prism 24 and deflected. Since the angle α of the prism 23 is larger than the angle β of the prism 24, the light transmitted through the prism 23 is bent more largely and is directed to illuminate the closer side. Projector 21 with prisms 23 and 24
FIG. 15 illustrates the size relationship when projected onto the screen.
In this case, the area of the lower prism 24 is set larger than the area of the upper prism 23 so that the intensity of light transmitted through the prism 24 is higher than the intensity of light transmitted through the prism 23. . With this setting, it is possible to increase the intensity of the distance range illuminated by the light transmitted through the prism 24 with respect to the intensity of the distance range illuminated by the light transmitted through the prism 23.

FIG. 16 shows an optical image when the optical system of FIG. 13 is cut along the BB cross section of FIG. 25 for protective panel 22
Image of the spread of light rays Pl ~ Pu transmitted through the parallel part of
Is a light image of the spread of light rays su to sl transmitted through the prism 24, and 27 is a light image of spread of the light rays qu to ql transmitted through the prism 23. The optical image 26 is, for example, as shown in FIG.
27 has a shape corresponding to, for example, FIG. 10 (a).
In terms of light intensity, there is a relationship of light image 25> light image 26> light image 27. That is, as a whole, it has a large spread in the vertical direction,
In addition, illumination light having high, medium, and low intensity distributions can be obtained in order from the upper side.

FIG. 17 shows still another embodiment according to the present invention. In FIG. 17, 28 and 29 are the same LEDs, which are condensed by the projection lenses 30 and 31, and are inclined with respect to each other so that their optical axes intersect at a distance of 4 m, for example. Reference numeral 32 denotes a protective panel, in which a prism 33 made of a parallel plate is formed at the position in the optical path of the projection lens 31, and the position of the light flux emitted from the projection lens 31 by the prism 33 is as described above. Deflection to the near side. That is, at a relatively distant distance, the light emitted from the projection lens 30 and the light emitted from the projection lens 31 and then passing through the parallel portion of the protection panel 32 are superposed to become a strong light, and at the near distance side, by the prism 33. It is configured to illuminate with a weak polarized light.

FIG. 18 shows another embodiment of the prism shape. 34
Is a projection lens, and the protection panel placed in front of it is a total of three small prisms 35, 3 with a space in the lateral direction.
6 and 37 are formed. The prisms 35, 36 and 37 have the same angle but are arranged at the positions shown in the figure.
This is because when the lateral length of the prism is shortened in order to weaken the amount of light deflected by the prism, the phenomena shown in FIGS. 10 (a), (b) and (c) also occur in the lateral direction. However, since it is inconvenient, they are arranged at appropriate intervals as shown in the figure.

FIG. 19 shows an embodiment in which a reflector 38 is used instead of the projection lens. A discharge tube 39 is used as the light source instead of the LED.

FIG. 20 shows an embodiment in which a cylindrical lens 41 is formed on the protective panel 40 instead of the prism, and in this case, the light is diverged toward the short distance side to weaken the intensity. It is also possible to use an aspherical lens instead of the cylindrical lens.

In the above embodiments, the deflecting member is provided on the protective panel, but the deflecting member may be provided between the light source and the projection lens as long as it can provide the spread and the intensity distribution as described above. Etc. can be arranged at any position.

Further, although the auxiliary illumination system is incorporated in the strobe device in the above embodiment, it may be provided separately from the strobe device.

[Effects of the Invention] As is apparent from the above description, according to the present invention, focus detection is possible even in a wide range from a long distance to a short distance without shaking illumination light, and power is not wastefully consumed. It is possible to perform efficient illumination, and it is possible to make the reflected light intensity far from the subject and even the near sides.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a structural explanatory view of an embodiment of an auxiliary illumination optical system according to the present invention, FIG. 2 is an optical path diagram of a projection light beam by the auxiliary illumination optical system of FIG. 1, and FIG. 2 is a cross-sectional explanatory view of a light beam in the AA cross section, FIG. 4 is an overall explanatory view of a focus detection system in which an auxiliary illumination optical system is incorporated in a strobe device, and FIG. 5 is an optical path of the focus detection system shown in FIG. Figures and 6 show (a), (b),
(C) is an enlarged cross-sectional explanatory view of an optical image at Lmin, Lmean, and Lmax in FIG. 5, FIG. 7 is an optical path explanatory diagram for explaining an optical image formed by a prism, and FIG. 8 is FIG. 9 is a front view of the projection lens showing the shape and position of the prism, FIG. 9 is an explanatory view of the optical path corresponding to FIG. 7 when the prism position is lowered, and FIGS. 10 (a), (b) and (c) are prisms, respectively. Fig. 11 (a) is a cross-sectional explanatory view showing the optical image formed by the prism when the position is changed to up, middle, and down, and Fig. 11 (a) shows the light passing through the prism when the vertical width of the prism is changed. Fig. 11 (b) is an explanatory diagram for defining various quantities used in the graph of Fig. 11 (a), and Fig. 12 (a) is a graph showing the change of the tilt angle α of the prism. FIG. 12 (b) is a graph showing the change of the change angle θ when the above-mentioned changes are made. FIG. 13 is a cross sectional explanatory view showing another embodiment of the present invention, FIG. 14 is an optical path explanatory view of FIG. 13, and FIG. 15 is a projection lens for showing the shape and position of the prism of FIG. A front view, FIG. 16 is an enlarged sectional explanatory view in a BB sectional view of FIG. 14 of an optical image obtained by the embodiment of FIG. 13, FIG. 17 is a sectional explanatory view showing still another embodiment of the present invention, FIG. 18 is a front view of a projection lens showing another example of the prism, FIG. 19 is a sectional explanatory view showing an embodiment in which a discharge umbrella is used as a light source, and FIG. 20 shows a cylindrical lens as a deflecting member. It is a section explanatory view showing an example used. 8,15,39… Light source, 9,17,21,30,31… Projection lens, 11,19,2
3,24,33,35,36,37 ... Prism, 41 ... Cylindrical lens.

Claims (1)

[Claims] Claim: What is claimed is: 1. An illumination light having a vertical spread, which is sufficiently larger than the vertical width of the focus detection area, is projected from a direction forming a predetermined angle with respect to a photographing optical axis from the camera to the camera. In the illumination optical system for illuminating the focus detection area of the built-in focus detection system, an intensity distribution is added to the illumination light that gives a gradually increasing intensity distribution from the lower part corresponding to the near distance side to the upper part corresponding to the far distance side. An illumination optical system for focus detection, comprising: