JP2600934B2 - Projection system for automatic focus detection - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a light projection system for automatic focus detection suitable for a photographic camera, a cine camera, a video camera, and the like. In passive and active automatic focus detection suitable for performing focus detection of a photographing system by projecting light and receiving the illumination light reflected from the object side, focus while expanding the distance measurement range. The present invention relates to a light projection system for automatic focus detection with improved detection accuracy.

(Prior Art) Conventionally, two types of focus detection systems have been used in photographic cameras, cine cameras, video cameras and the like.

One is a passive system proposed in, for example, JP-A-54-159259, and the other is a passive system proposed in, for example, JP-A-57-1542.
This is the active method proposed in Japanese Patent Publication No. 06 and the like.

Among them, the active method is a method in which focus detection is performed by projecting, for example, an infrared light beam from the camera side to the object side and receiving a reflected light beam from the object, and when the object side is dark, or when the object contrast is low. However, there is a feature that the focus can be accurately detected. However, when the subject is far away, there is a disadvantage that the amount of reflected light flux decreases and the focus detection accuracy decreases.

The passive method is a method of performing focus detection by detecting an image formation state of a subject image by a photographing system by a detection unit provided in a part of a camera, and relatively high-precision focus detection is performed even when a subject is far away. There is an advantage that can be done. However, when the subject side is dark or when the contrast of the subject is low, there is a disadvantage that the focus detection accuracy is reduced.

One method for remedying this drawback is described, for example, in JP-B-49-19810.
No. pp. 139 to 163. In this publication, a so-called pattern projection method in which a fixed pattern is projected from a camera side to a subject side by a projection system, and a focus detection of a photographing system is performed by detecting a reflection pattern image from the subject by a detection system on the camera side. Proposed an automatic focus detection device.

On the other hand, in recent automatic focus detecting devices, various types of so-called multi-point distance measuring type focus detecting devices that select an arbitrary one of a plurality of points in a shooting screen and perform distance measurement have been proposed. The above-described pattern projection method can be used as an effective method even in the focus detection device of the multipoint distance measurement method.

In general, in a focus detection device of the multipoint ranging system, it is necessary to simultaneously project a pattern onto a wide area on a subject.

(Problems to be Solved by the Invention) In general, there are various methods for simultaneously projecting a pattern onto a plurality of areas on a subject which are to be distance measuring points in a wide range.

For example, there is a method of projecting a large area using a light projection system using a large pattern.

However, in this method, a large light source must be used to illuminate the pattern so that there is no uneven illuminance, and the aberration of the light projecting system must be well corrected over a wide angle of view, and the entire light projecting system needs to be corrected. There was a problem that the size was increased.

There is also a method of projecting with a light projection lens having a short focal length and a wide angle of view using a fine pattern. However, in this method, first, it is difficult to create a fine pattern, and it is also difficult to enlarge the aperture of the light projecting lens. Therefore, the pattern is projected onto a distant subject with a sufficient amount of light. There was a problem that it was difficult.

In addition, it is difficult to project a pattern on a subject surface with a high resolution in any of the above-described methods. In particular, it is necessary to project a pattern with good optical performance over a wide angle of view while reducing the size of a projection lens. There is a problem that it is very difficult including aberration correction.

As a proposal for solving these problems, Japanese Patent Application Laid-Open No. 63-47710 proposes a method in which a plurality of illumination light sources of the above-described method for producing a large pattern image are used. However, such a configuration cannot solve the problem of the aberration correction of the light projecting lens described above.

In addition, as a light projection system for automatic focus detection which projects a pattern onto a wide area on a subject, the purpose is different, but for example, there is JP-A-62-247312.

In this publication, a light projecting lens is composed of a plurality of lens units whose optical axes are shifted so that a pattern can be favorably projected on a subject at a long distance and also on a subject at a short distance. The focus is detected by projecting a pattern onto a wide area on the subject.

The present invention appropriately arranges each element of a light projecting system for projecting illumination light from a light source having a light emitting surface of a predetermined size toward a subject, and projects the illumination light in a good condition on a wide range of subjects. And
In particular, it is an object of the present invention to provide a light projection system for automatic focus detection that can measure a distance at a plurality of points on a subject with high accuracy.

(Means for Solving the Problems) A light projection system for automatic focus detection according to the present invention projects illumination light from a light source to a subject side by a light projecting means, and receives the illumination light reflected from the subject side. In a light projecting system for automatic focus detection which performs focus detection of a photographing system by receiving light by a system, the light projecting means includes n light projecting units arranged such that their optical axes are positioned on the same plane (substantially the same). n is an integer of 2 or more), the refractive power of the lens unit is φ _P , the distance between the vertices of the n lens units is d, the focal length of the light projecting unit is f, and the n When the length of the light emitting portion of the light source in the plane including the optical axes of the lens portions is S, 0.36 <φ _P × n × d {(a) φ _P × d <S / f} (B) The following condition is satisfied.

(Embodiment) FIG. 1 is a schematic view of a main part of an embodiment when the present invention is applied to a part of a photographing system, and FIG. 2 (A) is a perspective view of the light projecting system of FIG. FIG. 1 shows a case where the light projecting system according to the present invention is applied to a photographing system having an automatic focus detection device of a so-called phase difference detection system of a passive system.

In the figure, reference numeral 101 denotes a light projecting system, which has a configuration as described later when a subject is dark and a passive method cannot perform focus detection, and projects illumination light toward the subject, or when the subject is dark or dark. When the contrast is low, a predetermined pattern is projected on the subject side. Reference numeral 21 denotes a photographing lens (objective lens). The photographing lens 21 forms a subject image on the photosensitive surface 30 and irradiates a focus detection unit 102 having a configuration described later with a natural light such as sunlight through a semi-transmissive surface of the quick return mirror 22 and a sub-mirror 23. An image (in the case of the passive system) and an image illuminated with the illumination light projected on the subject by the light projecting system 101 or a pattern formed on the light emitting surface 200 of the light source projected on the subject surface by the light projecting system 101 2 (in the case of the active system).

FIG. 2 (A) shows a case where a predetermined pattern 2 is formed on the light emitting surface 200 of the light source and the pattern 2 is projected on the subject side.

In the present embodiment, when the illumination light is simply projected on the object side, the light emitting surface 200 having no pattern provided on the surface is used as a light source. Light emitting surface 200 provided with pattern 2
Is used.

The method of projecting illumination light having a predetermined angle of view on the subject side at the time of focus detection and using a subject image within a range illuminated by the illumination light is the same as the method of projecting a pattern on the subject side. Can be handled.

Therefore, in the following embodiment, the pattern 2 is formed on the light emitting surface 200 as shown in FIG.
Is projected on the object side, and an image of the pattern 2 is used.

As shown in FIG. 2 (A), the light projecting system 101 in this embodiment has a light emitting surface 200 constituting a light source on which a pattern 2 having a stripe pattern extending in the horizontal direction is formed, and a light emitting surface 200 on the light emitting surface 200. And a light projecting means (hereinafter also referred to as a "light projecting lens") 1 for projecting the formed pattern 2 on the object side.

FIG. 2 (B) is a style diagram showing an opening state when the light projecting lens 1 is viewed from the front. As shown in FIGS. 2A and 2B, the light projecting lens 1 has a lens unit 11 and a lens unit 12 having an optical axis 15 for forming a pattern image in the same direction as the optical axis of the photographing lens 21, and the photographing lens 21. Refraction of a lens portion 13 having an optical axis 16 for forming a pattern image in a direction different from the optical axis of the lens portion, and a lens portion 14 also having an optical axis 17 for forming a pattern image in a direction different from the optical axis of the taking lens 21 It has four lens sections with approximately equal forces. Of these, lens parts 11, 12
Have the same optical axis 15 and the same optical action. Further, the optical axes 15, 16, 17 of the respective lens portions exist in a plane parallel to the stripe direction of the pattern 2.

And these four lens parts of the projection lens 1, 11, 12,
13 and 14, the pattern 2 is divided into three different areas on the subject, for example, as shown in FIGS.
33 is projected so that some parts overlap each other. Note that the pattern image 31 is an image formed by the lens units 11 and 12.

Next, a focus detection method by the focus detection unit 102 shown in FIG. 1 will be described with reference to FIG. Fig. 3 shows the first
FIG. 3 is an exploded perspective view of the optical system of the focus detection unit 102 shown in FIG. In FIG. 3, the mirror 26 shown in FIG. 1 is omitted.

In this embodiment, a focus detection device for multiple distance measurement capable of measuring a distance in a plurality of (three in the figure) regions of the subject image formed by the objective lens 21 is shown.

In the figure, reference numeral 24 denotes a field mask, which has openings 24a to 24c corresponding to a plurality of distance measurement areas, and is arranged in the vicinity of a predetermined imaging plane of the objective lens 21. Reference numeral 25 denotes a field lens, which is arranged in the vicinity of the planned image plane.

Reference numeral 28 denotes a secondary optical system, which comprises two lenses 28a and 28b symmetrically arranged with respect to the optical axis of the objective lens 21. Reference numeral 29 denotes a light receiving means, and a plurality of pairs of light receiving element rows (line sensors) 29a1, 29a2, and 29b1 corresponding to a plurality of distances disposed behind the two lenses 28a and 28b.
It has 29b2, 29c1 and 29c2.

Reference numeral 27 denotes a stop, which has two openings 27a and 27b disposed in front of the two lenses 28a and 28b.

The field lens 25 has openings 27a and 27b of the aperture 27.
Has an effect of forming an image on each area of the exit pupil of the objective lens, and the light flux transmitted through each area forms a light quantity distribution on the light receiving element array.

In the focus detection device shown in the present embodiment, when the image forming point of the objective lens 21 is in front of the predetermined image forming plane, for example, the object image or the pattern 2 formed on the two light receiving element rows 29b1 and 29b2, respectively. In the case where the light amount distributions of the images of the images are close to each other, and the image forming point of the objective lens 21 is behind the predetermined image forming plane, the light amounts formed on the two light receiving element arrays 29b1 and 29b2 respectively. The distributions are separated from each other. In addition, since the shift amount of the light amount distribution formed on each of the two light receiving element arrays 29b1 and 29b2 has a certain functional relationship with the out-of-focus amount of the objective lens 21, the shift amount is calculated by appropriate arithmetic means. The direction and amount of defocus of the lens 21 are detected.

4 and 5 show pattern images 31, 32, and 33 when a pattern 2 is projected onto a subject by the light projecting system 101 according to the present invention.
FIG. 9 is an explanatory diagram showing a positional relationship between the distance measurement field of view 34, 35, and 36.
FIG. 4 corresponds to the case where the photographing lens is a wide-angle lens or a zoom lens, and FIG. 5 corresponds to the case where the photographing lens is a telephoto lens or a zoom lens.

4 and 5, pattern images 31, 32, and 33 represent images of the pattern 2 by the lens units 11, (12), 13, and 14 of the light projecting lens 1, respectively. The distance measurement fields 34, 35 and 36 correspond to the openings 24a to 24c of the field mask 24 in FIG.

Usually, a single-lens reflex camera is equipped with photographing lenses having various focal lengths. For this reason, in a focus detection device that performs focus detection at a plurality of points in a shooting screen by using light rays that have passed through the shooting lens, the distance measurement field of view is fixed with respect to the shooting screen, but with respect to the subject, the distance of the shooting lens is not It changes according to the focal length.

On the other hand, in a light projecting system that projects a pattern onto a subject without passing through a photographic lens as in the present embodiment, the photographic range of the pattern is invariant to the focal length of the photographic lens. Therefore, the position of the distance measurement field with respect to the projected pattern image changes as shown in FIGS. 4 and 5 depending on the focal length of the photographing lens.

As shown in FIGS. 4 and 5, in the present embodiment, a light projecting lens is provided with a plurality of lens units 11 and 11, as described above, in order to project a pattern onto a wide area on a subject corresponding to a plurality of ranging points.
(12) Composed of 13, 14 and multiple pattern images on the subject
31, 32, and 33 are formed so that good focus detection can be performed at a plurality of ranging points regardless of the focal length of the photographing lens.

In particular, in the present embodiment, the pattern 2 is a striped pattern in which lines having different widths are collected, and the light receiving means 29 is constituted by a one-dimensional light receiving element array (line sensor) such as a CCD. Then, the stripe direction of the pattern and the arrangement direction of the light receiving element rows are perpendicular to each other, thereby improving the accuracy of detecting the contrast of the subject in the direction in which the light receiving element rows are arranged.

In this embodiment, the three pattern images 31, 32, and 33 partially overlap each other on the subject, so that the distance measurement fields 35 and 36 overlap the pattern images 31 and 32, respectively, and the pattern image.
The focus detection accuracy is prevented from deteriorating even when the focus detection device is disposed in a portion where the focus detection device overlaps the reference characters 31 and 33. Then, two or more (two in this embodiment) pattern images are projected in substantially the same direction as the optical axis of the photographing system and on both sides thereof, so that the pattern images are formed near the center of the photographing screen where the main subject is likely to be located. They do not overlap each other.

And, in order to improve the imaging performance of the part where the pattern images 31, 32, and 33 overlap each other, high-precision focus detection can be performed even when the distance measurement field of view is located in the part where the pattern images 31, 32, and 33 overlap each other. As described above, the optical axes of the lens portions 11, 12, 13, and 14 constituting the light projecting lens 1 exist in a plane parallel to the stripe direction of the pattern, and the refractive power of each lens portion is substantially equal. I have to. This makes it possible to perform high-precision focus detection without causing a displacement of a pattern image or a displacement of an imaging magnification.

Further, in this embodiment, each lens unit 11, 12, 1
The aperture areas of 3, 14 are appropriately set, and the ratio of the light amounts of the pattern images formed in the central part and the peripheral part of the photographing screen is controlled so that the ratio of the reach distance of the pattern images becomes a desired value. .

Next, the structural features of each element of the light projecting system in this embodiment will be described.

As shown in FIGS. 4 and 5, the distance between the three distance measurement fields of view 34, 35, and 36 on the subject increases as the focal length of the photographing lens decreases. According to the present invention, when a photographing lens having a standard focal length commonly used for a single-lens reflex camera (hereinafter, referred to as a “standard lens”) is attached, a pattern image is projected onto substantially the entire area of a main part of a photographing screen. It is intended to improve the focus detection accuracy. For this purpose, a commonly used short focal length photographing lens (hereinafter, referred to as a “wide-angle lens”) requires a configuration capable of projecting a pattern image onto substantially the entire area of the main part of the photographing screen.

In this embodiment, in order to satisfy such a condition, the above-described two conditional expressions (a) and (b) in the configuration shown in FIG.
To be satisfied.

In the embodiment shown in FIG. 2, the aforementioned conditional expressions (a) and (b)
Shows a case where n = 3. The lens units 11 and 12 are counted as one to show the same optical action.

Conditional expression (a) is for appropriately defining the arrangement of the center position of the pattern image (illumination range for illumination light) on the subject, and conditional expression (b) is for defining a plurality of pattern images ( This is for continuously projecting an illumination range for illumination light.

Next, the technical contents of the conditional expressions (a) and (b) will be described with reference to FIGS. 6, 7, 8, and 9. FIG.

In FIG. 6, reference numerals 31 to 33 denote the pattern images shown in FIGS. 4 and 5, and reference numerals 15a, 16a, and 17a denote the optical axes of the lens portions 11 (12), 13, and 14 in FIG. Corresponding pattern image 31
33 indicates the center position, and 40 indicates the range of the shooting screen corresponding to the use of a wide-angle lens.

FIG. 7 is an explanatory diagram for explaining the arrangement of the optical axis of each lens unit of the light projecting system. In the figure, reference numerals 15a to 17a denote center positions of the pattern images 31, 32, and 33 in FIG. 6, 40 denotes the range of the photographing screen, 41 denotes the lens units 11 and 12, and 42 denotes the lens unit 1 in FIG.
Reference numerals 3 and 43 denote thin lenses corresponding to the lens unit 14. Reference numeral 44 denotes a virtual image formed by the optical members existing after the thin lenses 41 to 43, and is a virtual image of the light emitting unit 200 of the illumination light source on which the pattern 2 shown in FIG. 1 is formed. When the light projection system is composed only of the lens units 11 to 14 and an optical member having no refractive power, the virtual image 44 is transmitted from the lens units 11 to 14 to the light emitting unit 200 of the illumination light source on which the pattern 2 is formed. They are arranged at positions separated by the converted optical path length.

Thin lens 41 and the thin lens 42 in FIG. 7, the distance between the thin lens 41 and the thin lens 43 (the vertex distance) d, and the refractive power of the thin lens 41-43 and phi _P, the light projecting system is normally pattern sufficiently distance of the virtual image 44 of the light emitting portion 200 to form a thin lens 41-43 and pattern 2 to be configured to image on a distant subject can be expressed as approximately 1 / phi _P. If the angle between the optical axes 15 and 16 and the optical axes 15 and 17 of the lens unit is θ _P , the following relationship holds between d, φ _P , and θ _P.

tanθ _{P =} φ _P × d ‥‥‥ addition, the when the 6 view to the focal length of the taking lens and F _W, the photographing optical axis borders of the photographic screen size is 36mm So horizontal horizontal direction of the photographing screen The following relationship holds between the angle θ _W and the focal length F _W , assuming that the angle formed by θ _W is θ _W.

tan θ _W = 18 / F _W ‥‥‥ Now, a pattern image is continuously projected on a subject by a light projecting lens composed of lens units having n optical axes separated by a distance d on the same plane. case, the boundary between the projection range tan .theta _a assuming that is sufficiently small overlap of the image of the pattern for the angle theta _a projection optical axis of the projection range of the entire pattern image tan on the position of the center of the pattern of formula
The following relationship holds because becomes n / 2 times the θ _P.

tanθ _A = φ _P × n × d / 2 ‥‥‥ Therefore, if the ratio of the main part in the horizontal direction of the photographing screen is x% of the whole screen, the main part of the photographing screen is obtained when a wide-angle lens is used as the photographing lens. In order to project a pattern image on almost the entire area of the section, it is necessary to configure the light projecting system so as to satisfy the following relationship from the equation.

In the above-mentioned conditional expression (a), the focal length of the photographing lens is _Fw = 50 mm, and the ratio of the main part of the photographing screen is x = 50%.
It was obtained as. The focal length of 50 mm is a focal length generally regarded as a standard lens in a 35 mm version of a single-lens reflex camera, and is determined to be a telephoto lens at a focal length on the telephoto side. A light projection system that projects a pattern image onto substantially the entire area of the main part of the shooting screen cannot be achieved. Also, the ratio of the main part of the shooting screen may be set so as to include a plurality of distance measurement fields arranged in the shooting screen. In the embodiment, the value of x is set to 50%. In a range narrower than this range, the effect of the distance measuring device that measures the distance at a plurality of points in the shooting screen is weakened.

FIG. 8 is an explanatory diagram for explaining a conditional expression (b) for continuously projecting a pattern image on a subject. In the figure, reference numerals 15 to 17, 15a to 17a, and 40 to 45 are the same as those in FIG. Numerals 31 to 33 correspond to the projection range of the pattern image shown in FIG.

In FIG. 8, the horizontal direction of the virtual image 44 of the light emitting section 200 of the illumination light source provided with the pattern 2 (the stripe direction of the virtual image of the pattern)
Is the size of S _o . The projection range of the pattern image by the thin lens 41 that projects the pattern image near the optical axis of the photographing lens is considered only by the light beam passing through the center of the thin lens 41, and the angle between the horizontal boundary line of the pattern and the optical axis is θ. When represented by _C , it can be expressed by the following relational expression.

tanθ _C = (S _o / 2) / (1 / φ _P ) ‥‥‥ Now, the refracting power of a plurality of lens units constituting the light projecting lens,
That is, since the refractive power of the thin lenses 41 to 43 in FIG. 8 is substantially the same, the center position 15a of the virtual image 44 of the light emitting unit 200 on which the pattern image 2 is formed by the thin lenses 41 to 43 is formed.
The projection is performed on a range 31 to 33 having substantially the same size around 1717a.

Since the pattern images 31 to 33 are projected around the center positions 15a to 17a of the pattern images as shown in FIG. 8, the above-described angle is required to project these three pattern images 31 to 33 onto the subject. θ _P and θ _C may be set so as to satisfy the following relational expression.

tan θ _P <2tan θ _Cす る と When the equation and the equation are substituted into the equation, the following is obtained.

φ _P × d <S _o / (1 / φ _P ) れ ば If a light projecting system that satisfies the condition of the formula is formed, it is possible to continuously project the pattern images 31 to 33 onto the subject. Become.

In order to achieve the object of the present invention, a light projecting means is constituted by only a light projecting lens having an aperture divided into a plurality of lens portions having substantially the same refractive power, and a light projecting lens and another positive or negative light source. A combination of a lens having a negative refractive power to shorten the focal length of the entire light projecting means and further increase the pattern projection magnification is also applicable. The above conditional expression (b) is derived by modifying the expression, assuming such a light projecting means.

FIG. 9 shows an embodiment in which the light projecting means according to the present invention is constituted by combining a light projecting lens having a plurality of lens portions having substantially the same refractive power and one lens having a positive refractive power. It is a schematic diagram. FIG. 3 shows a projection range of the pattern 2 projected from one lens unit 41. In the figure, 41, 4
4 correspond to the respective elements in FIG. In FIG. 9, the thin lenses 41 to 43 corresponding to the plurality of lens portions of the light projecting lens shown in FIG. 8 represent only the thin lens 41 for simplicity. In FIG. 9, reference numeral 46 denotes a lens having a positive refractive power, which is shown as a thin lens constituting a light projecting means in combination with the thin lens 41. Reference numeral 200 denotes a light emitting portion of the illumination light source provided with the pattern 2 corresponding to FIG. 44
Is a virtual image of the light emitting unit 200 of the illumination light source provided with the pattern 2 by the thin lens 46. The above equation is a relational expression regarding the angle θ _C between the horizontal boundary of the pattern and the optical axis when only the light beam passing through the center of the thin lens 41 is considered. The position and size of the virtual image 44 of FIG.

Here, the same relational expression will be expressed using the position and size of the light emitting section 200 of the illumination light source provided with the pattern 2 in FIG.

In FIG. 9, reference numeral 47 denotes an image-side principal point position of the entire light projecting means represented by the thin lens 41 and the thin lens 46. Since the light projecting means is generally configured to project a pattern image on a sufficiently distant subject, the distance from the rear principal point position 47 to the light emitting unit 200 provided with the pattern 2 is the focal length f of the entire light projecting means. Is set almost equal to Therefore the ninth
As shown in the drawing, when the horizontal size of the light emitting unit 200 of the illumination light source provided with the pattern 2 is S, the projection range of the pattern image by the thin lens 41 that projects the pattern image near the optical axis of the taking lens Can be expressed by modifying the equation for the angle θ _C between the horizontal boundary of the pattern and the optical axis when only the light passing through the center of the thin lens 41 is considered.

tanθ _C = (S / 2) / f す る と When the equation and the equation are substituted into the equation, the following is obtained.

φ _P × d × S / f ‥‥‥ That is, the above-mentioned conditional expression (b) is obtained.

If the expression, that is, conditional expression (b) according to the present invention is not satisfied, an area where the pattern image is not projected occurs between the plurality of pattern images projected on the subject, and the focal point of the mounted photographing lens. Depending on the distance, when the distance measurement field of view is arranged in such an area, the focus detection accuracy decreases.

FIG. 10 is an explanatory diagram showing a specific configuration of the embodiment shown in FIG. In the figure, reference numeral 200 denotes a light emitting portion of the light source provided with the pattern 2, and reference numerals 41 and 46 denote lenses having a positive refractive power corresponding to the thin lenses of FIG. Reference numeral 49 denotes a transparent resin in which the light emitting unit 200 of the light source for illumination is sealed.

The embodiment shown in FIG. 10 has a feature that it is easy to shorten the focal length of the entire light projecting system and expand the projection range of the pattern (illumination range in the case of illumination light).

As described above, according to the present invention, the light projecting means is configured to have a plurality of optical axes in the same plane and to have a plurality of lens portions having substantially the same refractive power, and to have a predetermined rear part of the light projecting means. By arranging a light source having a light emitting surface of a size or a predetermined pattern pattern and a light source for illumination, and setting each element so as to satisfy the conditional expressions (a) and (b), for example, A light projecting system that can project illumination light or a pattern image onto substantially the entire area of a main part of a photographing screen when a photographing lens is attached to a single-lens reflex camera is achieved.

In addition, the light emitting portion of the illumination light source provided with the pattern 2 of the present invention.
200 can be easily achieved by forming electrodes arranged on a light emitting element surface such as an LED in a predetermined pattern.

Although the case where the predetermined pattern 2 is applied to the light emitting unit 200 of the illumination light source has been described above, this pattern is used when the present invention is used in combination with a passive focus detection device such as a single-lens reflex camera. This is particularly effective. Further, the present invention can be sufficiently applied to the case where a light source having a light emitting surface on which no pattern is applied is used as described above.

(Effects of the Invention) According to the present invention, by setting each configuration such as the pattern of the light emitting portion pattern of the light source for illumination and the lens portion of the light projecting means as described above, it is possible to shoot while having good optical performance. Illumination light or a pattern can be projected onto substantially the entire area of the main part of the screen, and a light projection system for automatic focus detection that can perform high-precision focus detection at a plurality of points on the shooting screen can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a first embodiment when the present invention is applied to a part of a photographing system, FIG. 2 (A) is a perspective view of the light projecting system of FIG. 1, and FIG. ) Is a front view of the light projecting means of FIG. 2 (A), FIG. 3 is a schematic view of the focus detection unit of FIG.
FIG. 5 is an explanatory diagram of a pattern image projected on the subject side by the light projecting system of the present invention, FIG. 6 is an explanatory diagram showing a range of a photographing screen and a projecting range of a pattern in the present invention, and FIGS. Is an explanatory view of an optical system of a light projecting means showing the features of the present invention, FIG.
The figure is an explanatory diagram of a specific optical system in FIG. In the figure, 101 is a light projecting system, 102 is a focus detecting unit, 1 is a light projecting means, 2 is a pattern, 200 is a light emitting surface, 11 to 14 are lens units, 15 to 17 are optical axes, 21 is a photographing lens, 22 Is a quick return mirror, 31 to 33 are pattern images, 34 to 36 are distance measurement fields,
30 is a photosensitive surface.

Claims (2)

(57) [Claims] An automatic focus detection system for projecting illumination light from a light source to a subject side by a light projecting means and detecting a focus of a photographing system by receiving the illumination light reflected from the subject side by a light receiving system. In the light projecting system, the light projecting means is disposed such that the optical axis is located on the same plane, and has substantially the same refractive power.
(N is an integer of 2 or more) lens units, the refractive power of the lens units is φ _P , the vertex interval between the n lens units is d, the focal length of the light projecting unit is f, which satisfies the n-number of the lens portion of _{0.36 <φ P × n × d} φ P × d <S / f following condition when the length of the light emitting portion of the light source is S in a plane including the optical axis A special light projection system for automatic focus detection. 2. A light projecting system for automatic focus detection according to claim 1, wherein a predetermined pattern is formed on a light emitting portion surface of said light source.