JP4151082B2 - Focus detection device and camera - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a focus detection device that performs focus detection in a plurality of areas of an object scene and a camera equipped with the focus detection device .
[0002]
[Prior art]
Conventionally, as this type of apparatus, an apparatus as described in JP-A-4-174408 has been known. As shown in FIG. 18 , this apparatus includes a movable mask 20 disposed in the vicinity of the primary image plane of the objective lens, a toric lens 23 having different refractive powers in the X direction and the Y direction, and an X direction. And a pair of cylindrical lenses 25a and 25b, and a pair of line sensors 26. Then, the position of the opening of the movable mask 20 is changed by moving the movable mask 20 in the X direction in the figure by a driving mechanism (not shown), and the light beam transmitted through the opening is passed through a pair of focus detection systems 25a and 25b. The focus of different areas in the object scene is detected by forming an image on the image sensor.
[0003]
An apparatus as described in JP-A-4-307506 is known. This apparatus is movable or variable in transmittance, and includes a mask 30 having three rectangular openings arranged vertically and horizontally, a field lens 33, an aperture mask 34, a re-imaging lens 35, and three pairs of line sensors 36. The focus detection is enabled in nine areas in the object field by moving the mask 34 or changing the transmittance of the mask 34.
[0004]
[Problems to be solved by the invention]
However, in the apparatus described in Japanese Patent Laid-Open No. 4-174408, the movable mask 20 moves only in the X direction and the length of the line sensor 26 in the Y direction is short. It has a problem that it can be set only in the direction, that is, in the X direction.
[0005]
Further, the apparatus described in Japanese Patent Application Laid-Open No. 4307506 requires a number of line sensor sets corresponding to the number of focus detection areas, so that the structure of the sensor becomes more complex as the number of focus detection areas increases. is doing.
In view of the above problems, the present invention allows a focus detection area to be arranged in an arbitrary area in the object field with a simple configuration, and does not complicate the light receiving element even when the number of focus detection areas is increased. The object is to provide a detection device.
[0006]
[Means for Solving the Problems]
In the present invention according to claim 1 in order to achieve the above object, while being disposed in the predetermined imaging plane near the pair objective lens (1), light transmitted through the light flux from the plurality of regions of the predetermined focal plane and a transmitting portion selectively formable mask (8), wherein is placed in a position substantially conjugate with the exit pupil of the objective lens, the light flux passing through the light transmitting portion, different in the exit pupil of the objective lens Two sets of optical systems (12) for re-imaging by dividing into light beams passing through the positions, and a plurality of light receiving portions for receiving the image of the light transmitting portion of the mask formed by the two sets of optical systems And an area sensor (13) configured by arranging the light receiving elements in a matrix , and a signal based on an image selected from the two sets of images received by the area sensor according to the position of the light transmitting portion in the mask focus to perform focus detection of the objective lens with And a detection device.
[0007]
Further, in the present invention according to claim 2, the area sensor (13) is rectangular, and at least one direction among the arrangement directions of the plurality of light receiving elements arranged in a matrix is a perpendicular line on the object field or The two optical systems (12) coincide with a horizontal line, and the optical axes of the optical systems of the two optical systems are in a plane perpendicular to the optical axis of the objective lens (1). A straight line (X ′ axis, Y ′ axis) connecting the two is arranged so as to substantially coincide with a perpendicular (Y ″ axis) or a horizontal line (X ″ axis) on the rectangular area sensor.
[0008]
In the present invention according to claim 3, the area sensor (13) is rectangular, and the two sets of optical systems (12) are in a plane perpendicular to the optical axis of the objective lens (1). The straight line (X ′ axis, Y ′ axis) connecting the optical axes of the two optical systems is perpendicular to the perpendicular (Y ″ axis) or horizontal line (X ″ axis) on the rectangular area sensor. Therefore, they are arranged so as to have an angle (θ) that is line-symmetric with each other.
[0009]
In the present invention according to claim 4, the mask (8) includes an optical element capable of selectively changing the transmittance of an arbitrary region.
Further, in the present invention according to claim 5, in the focus detection apparatus according to claim 4, the optical element is a liquid crystal optical element.
Moreover, in this invention which concerns on Claim 6, it was set as the camera provided with the focus detection apparatus in any one of Claims 1-6.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing a schematic configuration of a focus detection apparatus according to a first embodiment of the present invention. FIG. 2 is a perspective view showing a schematic configuration of the focus detection optical system according to the first embodiment of the present invention. The focus detection optical system shown in FIG. It is a figure explaining the principle in an easy-to-understand manner. FIG. 3 is a schematic optical path diagram of the focus detection optical system according to the first embodiment of the present invention. 2 and 3, the same components as those in FIG. 1 are denoted by the same reference numerals.
[0011]
For the sake of convenience, the subject 14 in FIG. 2 has a size corresponding to the size of the object field, and the XY coordinates with the origin at the position through which the optical axis of the photographing lens 1 passes are set. . Further, the XY coordinates of the subject 14 corresponding to the object scene and the arrangement direction (X ″ Y ″ coordinates) of the light receiving elements of the area sensor 13 coincide with each other, and a straight line connecting the optical axes of the separator lenses 12a and 12b. , And 12c and 12d are arranged in parallel to the Y axis and X axis of the subject 14, respectively. Incidentally, in the present invention, it is assumed that the separator lenses 12 a to 12 d are arranged at an equal distance from the optical axis of the objective lens 1.
[0012]
A part of the light beam that has passed through the photographing lens 1 is reflected by a quick return mirror 2 that is at least partly composed of a half mirror, and is photographed through a diffusion screen 3, a condenser lens 4, a pentaprism 5, and an eyepiece 6. Reach the eyes of the other. On the other hand, a part of the light beam that has passed through the quick return mirror 2 is bent downward by the sub mirror 7 and enters the focus detection device (configuration from the mask 8 to the area sensor 13).
[0013]
Of the luminous flux emitted from the subject 14, the luminous flux incident on the focus detection device forms a primary image on the mask 8 by the photographing lens 1. That is, the mask 8 is disposed on the primary image plane (planned imaging plane) of the photographing lens 1. Of the primary image, only a light beam from an area corresponding to the focus detection area is selected by a mask 8 (described later) having a variable transmittance. A field lens 9 is disposed on the area sensor side near the mask 8, and the light beam that has passed through the mask 8 is condensed again on the diaphragm plate 11 via the field lens 9 and the total reflection mirror 10. The light beam that has passed through the diaphragm plate 11 is re-imaged on the area sensor 13 by the four separator lenses 12 a to 12 d arranged on the area sensor side near the diaphragm plate 11.
[0014]
Note that the mask 8 and the light receiving surface of the area sensor 13 are arranged at positions almost conjugate to the field lens 9 and the separator lenses 12a to 12d, and the exit pupil of the objective lens 1 and the aperture mask 11 are in the field. The lens 9 is disposed at a position substantially conjugate to each other.
For example, a light beam emitted from a point A on the subject 14 at a position where the optical axis AX of the objective lens 1 passes is imaged at a point A ′ on the mask 8 by the photographing lens 1. If the area on the mask 8 corresponding to the point A ′ is transparent, the light beam that has passed through the mask 8 is condensed by the field lens 9 and reaches the aperture plate 11. Respective light beams that have passed through the openings 11a to 11d of the diaphragm plate 11 are imaged on the area sensor 13 by the separator lenses 12a to 12d, respectively. At this time, of the light flux from the point A on the subject 14, the light flux that has passed through the exit pupil 1d of the photographing lens 1 is the same as the light flux that has passed through the exit pupil 1c to the aperture 11d of the aperture plate 11 by the field lens 9. Guided to the diaphragm plate 11c. That is, the four separator lenses 12a to 12d divide the light beam that has passed through the diaphragm plate 11 into light beams that pass through the region in the exit pupil of the photographing lens 1 corresponding to each of the separator lenses 12a to 12d. Re-image on top. Then, the output (light reception signal) from the area sensor 13 is calculated by a known method using a microcomputer (not shown), thereby calculating the defocus amount of the photographing lens 1.
[0015]
1 and 3, only one pair of the aperture of the diaphragm plate 11 and the separator lens 12 are depicted, but in actuality, as shown in FIG. 2, in a direction orthogonal to FIGS. are 1 Taihai location will peach.
By the way, the mask 8 is composed of a member having a variable transmittance such as a liquid crystal optical element, and passes through the primary image plane by the objective lens 1 by changing the transmittance of an arbitrarily set region in the mask 8. The light beam to be selectively guided to a later focus detection optical system.
This plays a role in determining a region in the object scene where focus detection is performed. For example, as shown in FIG. 2, when focus detection is performed on the point A on the subject 14, the part of the point A ′ on the mask 8 corresponding to the point A is made transparent and the remaining part is shielded from light. To do. When focus detection is performed on the point B1 and the point B2 on the subject 14, the corresponding points B1 'and B2' on the mask 8 are made transparent and the remaining portions are shielded from light. do it.
[0016]
In this way, only a region on the mask 8 corresponding to a desired focus detection region is made transparent, and other regions are shielded to select a light beam guided to the subsequent optical system. It is possible to detect the focus of a plurality of points in the object scene.
FIG. 4 is a diagram showing the respective areas in the case where the focus detection areas are nine areas corresponding to the object scene observed on the finder of the camera. As shown in FIG. 4, the respective regions are provided with reference numerals (1, 1) to (3, 3) and will be described later.
[0017]
FIG. 5 is a view showing a light transmission region of the mask 8 corresponding to the focus detection regions (1, 1) to (3, 3) shown in FIG. The mask 8 is composed of a liquid crystal optical element. Of the focus detection areas shown in FIG. 4, only the areas 8a to 8i corresponding to the desired focus detection areas are selectively transmitted, and the other areas are blocked by blocking the light. Make the detection area selectable.
[0018]
FIG. 6 is a diagram showing the state of the mask 8 when the region existing on the optical axis of the photographing lens 1, that is, the focus detection region (2, 2) in FIG. 4 is selected. FIG. 10 is a schematic diagram showing a state of an image formed on the area sensor when the region 8e of the mask 8 is transparent. In the figure, constituent members having the same functions as those in FIG. The light beam emitted from the point A on the subject 14 is imaged on the mask 8 by a photographing lens (not shown). The mask 8 is transparent only in the area 8e near the optical axis, and the other areas are shielded from light. The light beam that has passed through the area 8a of the mask 8 forms four secondary images 13a to 13d on the area sensor 13 through the field lens 9 by the four openings 11a to 11d and the separator lenses 12a to 12d. To do.
[0019]
The reason for using the area sensor is as follows. That is, in order to select one area from the nine focus detection areas shown in FIG. 4, the light transmission area of the corresponding mask 8 is selected. Since the position on the area sensor where the secondary image can be formed differs depending on the transmission region of the selected mask 8, an image may be formed outside the sensor in the arrangement of the conventional line sensor as shown in FIG. 17 or FIG. Arise. Therefore, the light receiving area is increased by using an area sensor as the sensor, and a set of secondary images is formed somewhere on the area sensor when any focus detection region is selected.
[0020]
There are various types of area sensors, such as CCD, MOS, SIT, etc., and each has its characteristics. The CCD area sensor is the most commonly used sensor and has excellent performance such as transfer efficiency. The MOS type is relatively easy to manufacture, and can read out only necessary pixels. Therefore, the MOS type is excellent when it is desired to read out only a place having a secondary image as in the present invention. Since SIT can read stored data in a non-destructive manner, it has an excellent point that it can be stored halfway, read data once, and after the data size is confirmed, the storage can be continued. The number of light receiving elements of the area sensor is preferably about 100 to 1000 in both the X "direction and the Y" direction in the figure. However, the distribution state and focus detection of the required focus detection area on the object field are desirable. It may be adjusted according to accuracy.
[0021]
FIG. 7 is a view showing a light shielding state of the mask 8 when the central upper region in FIG. 4, that is, the focus detection region (2, 1) is selected. FIG. 11 is a schematic view showing a state of an image formed on the area sensor when the region 8b of the mask 8 is made transparent. As described above, when the focus detection area is shifted upward from the central portion on the object field (the area 8b of the mask 8 is made transparent), the secondary image formed on the area sensor 13 is also shifted upward in the figure. It will be. At this time, since the size of the light receiving portion of the area sensor 13 is limited, by selecting a position other than the position through which the optical axis AX passes as the focus detection area, the four secondary images are connected outside the area sensor. There is a possibility that an image will appear. Therefore, when performing focus detection, focus detection is performed based on a light reception signal obtained from a set of images 13a and 13b by the separator lenses 12a and 12b or a set of images 13c and 13d by the separator lenses 12c and 12d. That is, in the case of FIG. 11, the image 13c is formed at a position farthest from the center of the area sensor. In such a case, focus detection may be performed based on the light reception signal obtained from the pair of images 13c and 13d so that the light reception signal obtained from the pair of images 13a and 13b is not used.
[0022]
In this way, by providing two sets of separator lenses that are not on the same straight line, the position where the secondary image can be formed by shifting the focus detection area outside the optical axis is from the center of the area sensor (the position through which the optical axis AX passes). Even in the case of deviation, focus detection can be performed based on the received light signal obtained from either one of the two sets of secondary images. Therefore, the light receiving area of the area sensor can be further reduced.
[0023]
Similarly, FIG. 8 is a diagram showing the light shielding state of the mask 8 when the right focus detection area (3, 2) in FIG. 4 is selected, and FIG. 12 shows the area 8f of the mask 8 made transparent. It is the schematic which shows the state of the image imaged on an area sensor in a case. In this case, of the four secondary images 13a to 13d on the area sensor 13, the image 13a is formed at a position farthest from the center of the area sensor. Therefore, if focus detection is performed based on the light reception signal obtained from the set of the secondary images 13c and 13d, it is possible to obtain a focus detection device that suppresses the area of the light receiving portion of the area sensor 13 to the minimum necessary.
[0024]
Further, FIG. 9 is a diagram showing a light shielding state of the mask 8 when the lower right focus detection region (3, 3) in FIG. 4 is selected, and FIG. 13 is a case where the region 8i of the mask 8 is made transparent. It is the schematic which shows the state of the image imaged on an area sensor. In this case, since both the secondary images 13a and 13d are imaged at a position further away from the center of the area sensor, one of the sets of the images 13a, 13b and 13c, 13d is first on the area sensor. You should avoid using the pair that falls outside.
[0025]
According to the first embodiment described above, at least one of the arrangement directions of the light receiving elements of the area sensor is matched with a vertical line or a horizontal line on the object field, and two sets of optical systems are arranged on the area sensor. By arranging so that it is almost coincident with the vertical line or horizontal line, the direction of the image formed on the area sensor and the arrangement direction of the light receiving elements of the area sensor can be matched, and the detection efficiency of the received light signal Is good.
[0026]
FIG. 14 is a diagram showing a focus detection apparatus according to the second embodiment of the present invention. In the figure, constituent members having the same functions as those in the first embodiment are denoted by the same reference numerals. In addition, constituent members not related to the description are omitted.
In the first embodiment, as shown in FIGS. 1 and 10, the horizontal axis (X axis) and the vertical axis (Y axis) on the object field, and the optical axes of the respective sets of the separator lenses are connected to each other. The connected X ′ axis and Y ′ axis and the arrangement directions X ″ and Y ″ of the area sensor 13 correspond to the axial directions of X, X ′, X ″ and Y, Y ′, Y ″, respectively. In the case of this embodiment, as shown in detail in FIG. 14B, the X ′ axis connecting the optical axes of the separator lenses 12a and 12b is θ1, and the optical axes of the separator lenses 12c and 12d are the optical axes of the separator lenses 12c and 12d. The connecting Y ′ axes are arranged with an angle of θ2 with respect to the X axis. In this embodiment, θ1 = θ2 = 45 °. Further, the arrangement directions X ″ and Y ″ of the light receiving elements of the area sensor 13 coincide with the X axis and the Y axis, respectively.
[0027]
FIG. 14A shows a state of an image formed on the area sensor when the central focus detection region (2, 2) in FIG. 4 is selected (the region 8e of the mask 8 is made transparent). FIG. In this case, the figure connecting the centers of the secondary images 13a to 13d formed on the area sensor 13 by the separator lenses 12a to 12d is a square with the optical axis as the center, and each side of the square is an area. It becomes almost parallel to the sensor arrangement direction X ″ or Y ″. In this way, by tilting the X ′ axis and the Y ′ axis with respect to the arrangement direction of the light receiving elements of the area sensor (X ″ axis direction, Y ″ axis direction), the secondary image formed on the area sensor 13 The arrangement can be adjusted.
[0028]
FIG. 15 is a schematic diagram illustrating a state of an image formed on the area sensor when the upper center of the object scene is selected as the focus detection area, as in the case illustrated in FIG. 11. The secondary images 13a to 13d formed on the area sensor 13 are shifted from the center of the area sensor as in FIG. 11, but the distance of the secondary image 13c from the center of the area sensor 13 is larger than that in FIG. It is getting shorter. That is, the size of the area sensor can be further reduced with the configuration of the second embodiment.
[0029]
FIG. 16 is a schematic diagram showing a state of an image formed on the area sensor when the right central portion of the object scene is selected as the focus detection area, as in FIG. In this case, of the four secondary images, the images 13a and 13c are formed at the position farthest from the center of the area sensor, but both of them are closer to the center of the area sensor than the image 13a of FIG. Image.
[0030]
FIG. 17 is a diagram showing a state of an image formed on the area sensor when the lower right portion of the object scene is selected as the focus detection area, as in FIG. In this case, the secondary image 13a is farthest from the center of the area sensor, but since the direction is the diagonal direction of the area sensor 13, the image is formed without deviating from the area sensor. As described above, by appropriately adjusting the angles θ1 and θ2, focus detection using the light receiving portion of the area sensor 13 can be performed to the maximum extent possible. In particular, by setting θ1 = θ2, the figure formed by connecting the four secondary images 13a to 13d becomes a rectangle, so that the matching with the area sensor 13 having the same rectangular light receiving portion is improved. Further, it is most efficient and minimal if the angles θ1 and θ2 are set such that the rectangular aspect ratio formed by connecting the secondary images is the same as the rectangular aspect ratio of the light receiving portion of the area sensor 13. The focus detection area can be separated from the center of the object field by the light receiving area.
[0031]
【The invention's effect】
As described above, in the present invention according to the first aspect, the mask capable of selectively forming the light transmitting portion that transmits the light beams from the plurality of regions in the planned focal plane of the objective lens is provided in the vicinity of the planned imaging plane of the objective lens. The light transmitting portions are selectively used to selectively transmit light beams from a plurality of regions in the object field, and the light receiving elements are connected to an area sensor arranged in a matrix. a configuration for an image, for which to perform focus detection of the objective lens using the signal by the selected image according to the position of the inner light transmitting portion of the two sets of images received by the area sensor, reduce the light receiving area of d rear sensor It becomes possible to do.
[0032]
In the present invention according to claim 2, at least one arrangement direction of the light receiving elements of the area sensor is made to coincide with a vertical line or a horizontal line on the object field, and two sets of optical systems are perpendicular to the area sensor. Alternatively, by arranging so as to substantially coincide with the horizontal line, the direction of the image formed on the area sensor and the arrangement direction of the light receiving elements of the area sensor can be matched, and the detection efficiency of the received light signal is good.
[0033]
In the present invention according to claim 3, the area of the area sensor can be further reduced by arranging the two sets of optical systems at angles symmetrical to each other with respect to the perpendicular or horizontal line on the area sensor. The light receiving part can be used effectively.
In the present invention according to claim 4, it is not necessary to provide a mask drive mechanism for changing the focus detection area by selecting the focus detection area using an optical element having variable transmittance as a mask. A focus detection device with a simple structure can be realized.
[0034]
According to the fifth aspect of the present invention, a focus detection device having a simple configuration can be provided by using a liquid crystal optical element as a mask.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a focus detection apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic configuration of a focus detection optical system according to the first embodiment of the present invention. FIG. 3 is a schematic optical path diagram of the focus detection optical system according to the first embodiment of the present invention. FIG. 4 is an observation of each area on the camera finder when the focus detection area is 9 areas. FIG. 5 is a diagram showing a light transmission region of a mask corresponding to the focus detection region shown in FIG. 4. FIG. 6 is an optical axis of the photographing lens as the focus detection region. FIG. 7 is a diagram showing a mask state when a region existing in FIG. 4 is selected. FIG. 7 is a diagram showing a mask light shielding state when a central upper region in FIG. 4 is selected as a focus detection region. When the right center area in FIG. 4 is selected as the detection area FIG. 9 is a diagram showing the light shielding state of the mask. FIG. 9 is a diagram showing the light shielding state of the mask when the lower right area in FIG. 4 is selected as the focus detection region. FIG. Fig. 11 is a schematic diagram showing the state of an image formed on the area sensor. Fig. 11 is a schematic diagram showing the state of an image formed on the area sensor when the mask region 8b is transparent. FIG. 13 is a schematic diagram showing a state of an image formed on the area sensor when the region 8f of the mask is made transparent. FIG. 13 shows a state of an image formed on the area sensor when the region 8i of the mask is made transparent. FIG. 14 is a diagram showing a focus detection device according to a second embodiment of the present invention. FIG. 15 is an image formed on an area sensor when the upper center of the object scene is selected as a focus detection region. FIG. 16 is a schematic diagram showing the state of an image to be displayed Schematic diagram showing the state of the image formed on the area sensor when the right center part of the object scene is selected as the exit area. FIG. 17 shows the case where the lower right part of the object scene is selected as the focus detection area. FIG. 5 is a diagram showing an optical system of the second embodiment. FIG.
FIG. 18 is a diagram showing a schematic configuration of a conventional focus detection apparatus. FIG. 19 is a diagram showing a schematic configuration of a conventional focus detection apparatus.
DESCRIPTION OF SYMBOLS 1 Shooting lens 8 Mask 8a-8i Light transmissive part 9 Field lens 11, 11a-11d Diaphragm plate 12, 12a-12d Separator lens 13 Area sensor 14 Subject

Claims (6)

While it is disposed in the predetermined imaging plane near the pair objective lens, and selectively formable mask the light transmitting portion for transmitting light beams from a plurality of regions of the predetermined focal plane,
Wherein is placed in a position substantially conjugate with the exit pupil of the objective lens, the light flux passing through the light transmitting portion, two for reimaging each divided into light beams passing through the different positions in the exit pupil of the objective lens A pair of optical systems;
An area sensor configured by arranging a plurality of light receiving elements in a matrix to receive an image of the light transmitting portion of the mask formed by the two sets of optical systems ;
A focus detection apparatus that performs focus detection of the objective lens using a signal based on an image selected in accordance with a position of the light transmission portion in the mask, out of two sets of images received by the area sensor . The area sensor is rectangular, and at least one direction among the arrangement directions of the plurality of light receiving elements arranged in a matrix coincides with a perpendicular line or a horizontal line on the object field,
In the two sets of optical systems, in a plane perpendicular to the optical axis of the objective lens, straight lines connecting the optical axes of the optical systems of the two sets of optical systems are perpendicular to the rectangular area sensor. The focus detection apparatus according to claim 1, wherein the focus detection apparatus is arranged so as to substantially coincide with a horizontal line.  The area sensor is rectangular, and the two sets of optical systems have a straight line connecting the optical axes of the optical systems of the two sets of optical systems in a plane perpendicular to the optical axis of the objective lens. The focus detection apparatus according to claim 1, wherein the focus detection apparatus is arranged at an angle symmetrical to each other with respect to a perpendicular line or a horizontal line on the rectangular area sensor.  The focus detection apparatus according to claim 1, wherein the mask includes an optical element capable of selectively changing the transmittance of an arbitrary region.  The focus detection apparatus according to claim 4, wherein the optical element is a liquid crystal optical element. A camera comprising the focus detection device according to claim 1.

Images