JP2017219654A - Interchangeable lens, camera main body, and camera system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a camera system capable of accurately correcting with a simple configuration by using minimum information for correcting photometric output.SOLUTION: The camera system which has an interchangeable lens having a photographic system, which can be attached onto and detached from a camera main body, includes: storage means that stores information relevant to peripheral light quantity, focus distance, open F value, eye-relief of at least imaging lens; and calculation means that calculates an exit pupil shape of the imaging lens using the information.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an interchangeable lens, a camera body, and a camera system, and in particular, for photometry, which includes a light beam (hereinafter referred to as “subject light”) based on a subject image transmitted through a photographing system (photographing optical system). The luminance information of the subject is detected with a simple configuration with high accuracy by using a light receiving element and using an output signal obtained from the light receiving element.

  Conventionally, various devices have been proposed as camera photometry devices. For example, in a single-lens reflex camera using an interchangeable interchangeable lens, a TTL photometry method that uses a light beam itself that has passed through a photographing system is generally used in order to obtain luminance information of a subject.

  That is, in photometry in the TTL photometry method in a single-lens reflex camera, first, a light receiving element for photometry in which subject light that has passed through a photographing system to form an image on a planned focal plane is arranged at a position optically equivalent to the planned focal plane. Form an image on the surface. In general, the luminance information of the subject is calculated using the output signal obtained from the light receiving element, and the luminance information of the subject calculated here is used to determine the exposure amount of the camera. Met.

  FIG. 12 is a schematic diagram of a main part of a conventional general single-lens reflex camera. In this figure, 211 is an interchangeable lens, and 212 is a camera body. As shown in the figure, in the single-lens reflex camera, the subject light transmitted through the photographing optical system 201 is reflected upward by the quick return mirror 202. The reflected subject light is imaged on a focusing screen 204 having a focal plane at a position equivalent to the planned focal plane 203 on which the image sensor is arranged.

  The focusing screen 204 in the figure is a diffusing surface arranged so that one surface thereof is optically equivalent to the planned focusing surface 203, and the light beam transmitted through the focusing screen 204 is used on this surface. The imaging state of the subject image at can be observed. Further, the other surface of the focusing screen 204 is a surface having a light condensing function (light condensing surface), and has a function of condensing the light beam emitted from the exit pupil of the photographing optical system 201 to the observer's pupil. .

  The subject image formed on the focal plane of the focusing screen 204 is magnified by a finder optical system composed of a pentaprism 205 and an eyepiece lens 206, and is enlarged and observed from the pupil position 207 of the observer. It is configured to be.

  In the same figure, an eyepiece lens 206 and a photometric optical system (photometric means) arranged on the optical axis of the finder optical system are arranged behind the exit surface of the pentaprism 205. In order to avoid mechanical and optical interference, the photometric means is provided with a photometric optical system (photometric means) composed of a photometric lens 208 for photometry and a light receiving element 209 at a position away from the finder optical axis.

  In the drawing, a part of the subject light formed on the focal plane of the focusing screen 204 and transmitted through the focusing screen 204 is re-imaged on the surface of the light receiving element 209 by the photometric lens 208 and obtained from the light receiving element 209. The output signal is used to measure the luminance distribution of the subject.

  As described above, on the focusing screen 204, it is possible to observe the light-condensing surface having a function of condensing the light beam emitted from the exit pupil of the photographing system 201 to the pupil position 207 of the observer and the imaging state of the subject image. A diffusion surface is formed. Therefore, the subject light incident on the photometric lens 208 varies greatly depending on the characteristics of the diffusion surface and the position and diameter of the exit pupil of the imaging system 201.

  Since the general single-lens reflex camera photometric device as described above has the optical arrangement as described above, in order to calculate the luminance information of the subject, an image is taken with respect to the output of the light receiving element 209 for photometry. It was necessary to add various corrections according to the characteristics of the system 201. In particular, in a divided photometry device that divides an object scene into a plurality of regions and outputs luminance information for each region, this correction technique is essential for accurate luminance information output.

  As a conventional example of the most common single-lens reflex camera, the built-in photometry device is a camera that is supposed to measure subject brightness in the viewfinder observation state, and measures the brightness information around the center of the object field on average Can be mentioned. In such a conventional single-lens reflex camera, the output of the light-receiving element for photometry (hereinafter also referred to as “photometric output”) is corrected based on information on the focal length, open F value, and exit pupil position of the imaging system. The technique of doing was more commonly implemented than before.

  However, in addition to information on the focal length, open F value, and exit pupil position, the imaging system has a unique exit pupil shape for each interchangeable lens. Therefore, in order to correct the photometric output with high accuracy, it is necessary to consider the shape of the exit pupil, and various methods for taking this into account have been proposed (see Patent Documents 1 and 2).

  Patent Document 1 holds information about the focal length of an interchangeable lens, the open F value, the exit pupil distance, and the distribution of the incident angle of a light beam incident on each image height on the planned imaging plane from the imaging system. A camera system that corrects the photometric output by appropriately combining the information is disclosed.

  In Patent Document 2, in addition to the focal length, open F value, and exit pupil distance of the interchangeable lens, information on three apertures set corresponding to the interchangeable lens is held, and the exit pupil shape is determined from the aperture information. A TTL photometric device generated by calculation is disclosed.

JP 2005-352137 A JP-A-6-214285

  However, in the prior art disclosed in Patent Document 1 described above, the camera system holds information about the exit pupil shape at the entire image height, and the data capacity to be held by the camera system becomes enormous.

  In the prior art disclosed in Patent Document 2 described above, the exit pupil shape is calculated using the same aperture information at the entire image height. However, the aperture position that restricts the luminous flux of the interchangeable lens is different for each image height. If different interchangeable lenses are considered, the exit pupil shape cannot be calculated accurately. Further, if accurate aperture information for each image height is accurately maintained, the data capacity of the interchangeable lens increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a camera system capable of performing accurate correction with a simple configuration using minimum information for correcting photometric output.

In order to achieve the above object, a camera system according to the present invention includes:
In a camera system in which an interchangeable lens having a photographing system can be attached to and detached from the camera body, storage means for storing at least information relating to the peripheral light amount of the photographing lens, the open F value, and the exit pupil distance, and the luminous flux shape of the photographing lens using the information It has the calculating means which calculates.

  According to the present invention, it is possible to calculate the luminance information of subject light with high accuracy using a minimum amount of information for the camera system to correct the photometric output. It is possible to provide an interchangeable lens, a camera body, and a camera system that can output a good image by setting an appropriate exposure based on the calculated luminance information.

Schematic diagram of main parts of camera system (imaging device) Schematic diagram of changes in luminous flux shape due to the passage of the taking lens Schematic comparison of shape of peripheral and central beam Schematic showing the approximate shape of the luminous flux shape of FIG. Cross section of the main part of the photometric optical system of the camera body 2 Photometry output correction flowchart Schematic of the relationship between direct light and diffused light Schematic of calculation of luminous flux entering the photometric lens Schematic diagram of main parts of camera system (imaging device) Schematic diagram of phase difference focus detection device 91 Schematic of calculation of luminous flux entering the diaphragm surface of the phase difference focus detector Schematic diagram of the main parts of a typical single-lens reflex camera

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram of a main part of a camera system (image pickup apparatus) according to a first embodiment of the present invention. The camera system of this embodiment is effective for an interchangeable lens digital camera.

  In the figure, reference numeral 2 denotes a camera body, and 1 denotes an interchangeable lens (photographing lens body) that can be attached to and exchanged with the camera body 2. Reference numeral 11 denotes an imaging system (imaging optical system) that constitutes the interchangeable lens 1 and optically forms a subject image on the surface of the imaging element 13. Reference numeral 12 denotes a quick return mirror (QR mirror), and reference numeral 13 denotes an image pickup device arranged on a planned focal plane of the photographing system 11, which is composed of, for example, a CCD. Reference numeral 14 denotes a focusing screen, 15 denotes a pentaprism as an image inverting means, 16 denotes an eyepiece, 17 denotes an observer's pupil position, 18 denotes a photometric lens, and 19 denotes a photometric light receiving element (light receiving means).

  Reference numeral 3 denotes a lens microcomputer, which drives and controls each function of the interchangeable lens 1. The lens microcomputer 3 has lens information storage means (for example, ROM) that stores information related to the amount of light in the periphery of the photographing system 11. Reference numeral 4 denotes a camera microcomputer that controls driving of each member of the camera body 2. The camera microcomputer 4 has correction means for correcting the deviation between the luminance distribution of the subject and the illuminance distribution of the subject image by using information from the lens information means in the lens microcomputer 3 with respect to the signal from the light receiving means 19. ing.

  In this embodiment, by using each information from the lens information means, the correction means appropriately corrects the output signal of the light-receiving element 19 for photometry so that the luminance information of the subject can be obtained with high accuracy. In the single-lens reflex camera shown in the figure, the subject light transmitted through the photographing system 11 is on the surface of the image sensor 13 in which the image pickup surface is disposed on the planned focal plane in a state where the quick return mirror 12 is retracted from the photographing optical path. An image is formed.

  On the other hand, in the state where the quick return mirror 12 is arranged in the photographing optical path as shown in the figure, the subject light is imaged on the focusing screen 14 arranged so as to be optically equivalent to the planned focal plane. It is the composition which becomes.

  The focusing screen 14 is formed in a substantially flat plate shape as shown in the figure, and one surface thereof is a diffusing surface disposed so as to be optically equivalent to the planned focal plane of the imaging system 11, Using the light beam that has passed through the focusing screen 14, the imaging state of the subject image on this surface can be observed. Further, the other surface of the focusing screen 14 is a surface having a light condensing function (light condensing surface), and has a function of condensing the light beam emitted from the exit pupil of the photographing system 11 at the pupil position 17 of the observer. Yes.

  The subject image formed on the focal plane of the focusing screen 14 is magnified by a finder optical system composed of a pentaprism 15 and an eyepiece 16 and then enlarged and observed from the pupil position 17 of the observer. It is configured to be. Further, in the drawing, an eyepiece 16 and a photometric optical system (photometric means) arranged on the optical axis of the finder optical system are arranged behind the exit surface of the pentaprism 15. In order to avoid mechanical and optical interference, the photometric means is provided with a photometric optical system (photometric means) composed of a photometric lens 18 for photometry and a light receiving element 19 at a position away from the finder optical axis.

  In the drawing, a part of the subject light formed on the focal plane of the focusing screen 14 and transmitted through the focusing screen 14 is re-imaged on the light receiving element 19 surface by the photometric lens 18 and obtained from the light receiving element 19. The output signal is used to measure the luminance distribution of the subject.

  As described above, on the focusing screen 14, it is possible to observe the focusing state having a function of condensing the light beam emitted from the exit pupil of the photographing system 11 at the pupil position 17 of the observer and the imaging state of the subject image. And a diffusion surface. Therefore, the subject light incident on the photometric lens 18 varies greatly depending on the position and shape of the exit pupil of the imaging system 11.

[Example 1]
Hereinafter, with reference to FIG. 2, a method for calculating the light beam shape (exit pupil shape) after exiting the photographing lens will be described.

  FIG. 2 is a schematic diagram showing the relationship between the light beam shape before incidence of the photographing lens and the light beam shape after emission.

  Reference numeral 21 denotes a light beam shape (hereinafter referred to as a central light beam shape) that forms an image at the center position of the imaging surface before incidence of the photographing lens, and reference numeral 22 denotes a light beam shape that forms an image at the peripheral position of the imaging surface before incidence of the photographing lens (hereinafter referred to as peripheral). The light beam shape). Reference numeral 23 denotes a central light beam shape after exiting the photographing lens, and 24 denotes a peripheral light flux shape after exiting the photographing lens. As shown in FIG. 2, the shape of the central light beam is circular, but the peripheral light beam shape is not usually circular, and the light beam shape before incidence of the photographing lens and the light beam shape after emission are different.

  If we do not consider the transmittance of the taking lens now, the light quantity before and after the taking lens is constant from the principle of light beam reversal, that is, the relationship between the peripheral light quantities does not change. Here, the peripheral light amount E can be expressed as follows, assuming that the aperture efficiency V, the influence rate D due to distortion, and the incident angle of the peripheral lens when the central light beam is 0 degree are ω.

When the optical path as shown in FIG. 2 is assumed, the peripheral light quantity is constant before and after the photographing lens is incident, and therefore the following equation holds. V ₁ , D ₁ , and ω ₁ are the aperture efficiency when passing through the taking lens from the left side of FIG. 2, the influence rate due to distortion, and the incident angle, respectively, and V ₂ and ω ₂ are passed through the taking lens from the right side ( It represents the value when the ray was traced back.

The aperture efficiency is an area ratio between the central light beam and the peripheral light beam when the light beam is observed on a reference plane before the photographing lens is incident. Therefore, V ₁ here is the peripheral light beam before the photographing lens is incident. area ratio of the center light beam, V ₂ represents the area ratio of the peripheral light and central light beams after shooting lens exit. The fraction affected by the distortion is a value representing the ratio of longitudinal photographing lens incidence, it is not necessary to consider the D ₂ are in considering equation (2).

Since ω ₂ is a value determined by the distance from the planned imaging plane to the exit pupil, if the peripheral light amount value at a certain image height and the exit pupil distance are known from the formula (2), V ₂ corresponding to the area ratio of the peripheral luminous flux is obtained. For the central light beam, the shape of the light beam can be obtained only by the open F value of the photographic lens. Therefore, the peripheral portion on any surface after exiting the photographic lens is determined by the area ratio of the peripheral light flux after exiting the photographic lens obtained here. The area of the light beam passing through can be obtained. However, in this case, the exit pupil distance at a certain image height for obtaining the position of the light beam needs to be a value indicating the position of the center of gravity of the light beam.

  In addition, the shapes of the central light beam and the peripheral light beam of the photographing type usually differ depending on the vignetting characteristic of the photographing lens. FIG. 3 is a conceptual diagram showing the shape of a light beam observed on an arbitrary surface after passing through the taking lens. (A) shows the central light beam 31 and (B) shows the peripheral light beam 32. The peripheral luminous flux shape after passing through the photographing lens is thus a shape close to an ellipse.

Since the position of the light beam passing through the center of gravity of the light beam, the area of the light beam, and the approximate shape of the light beam are already known in the examination so far, the peripheral light beam after passing through the photographing lens can be inferred as an elliptical shape as shown in FIG. . (A), (B) is a light beam corresponding to FIG. 3, and represents the shape and position in the case where the solid line around the light beam is assumed to be an elliptical shape. At this time, if the diameter of the central light beam is 2R and the short diameter is 2V ₂ R, it is possible to calculate the peripheral light beam reflecting the area ratio and the approximate shape of the light beam. By considering in this way, the light beam shape, that is, the exit pupil shape of the photographing lens can be calculated by analogy from the area ratio in a form close to the actual light beam shape.

  Here, a method of using the calculated exit pupil shape for photometric output correction will be described.

  FIG. 5 is a cross-sectional view of the main part of the photometric optical system in the present embodiment.

As shown in the figure, the light beam that has passed through the photographing lens 11 forms an image on the focusing screen 14, and after diffusion, passes through the pentaprism 15. The diffused light is observed from the pupil position 17 and the photometric lens 18 of the observer. The photometric lens is arranged at a position inclined by θ _r from the optical axis so as not to block the light beam traveling toward the observer. At this time, θ _t is the angle range of the photometric lens as viewed from the focusing screen. The light beam that forms an image on the photometric sensor must be incident on the photometric lens, and in order to know the light beam that enters the photometric lens, it is necessary to know the behavior of direct light that is not diffused on the photometric lens surface 51.

  In order to correct the photometric output, the relationship between the light quantity ratio of the imaging surface and the photometric sensor must be known. If the information of the photographing lens is known, the distribution on the imaging surface is known, and the correspondence relationship between the light quantity ratios can be obtained by obtaining the light quantity distribution on the photometric sensor surface 51 at that time.

  FIG. 6 shows a photometric correction processing procedure in this embodiment.

In FIG. 6, in step s1, the camera body acquires the open F value of the photographing lens and the distance information of the exit pupil at each image height. In this photometric output correction, the exit pupil shape is not used directly. Although the exit pupil shape of the photographic lens is obtained by Equation (2), if it passes through another optical system after passing through the photographic lens, the light beam shape is calculated using the position after passing through the optical system and the angle ω _2. There is a need to. Therefore, in consideration of use for photometric output correction, the position and incident angle of the direct light beam when observed with the photometric lens surface 51 are required here.

Therefore, in step s2, first, the incident angle of the light beam on the focusing screen is obtained by using the distance information of the exit pupil of the lens. Based on this information, by tracking the light flux based on the focal length of the focusing surface of the focusing screen and the optical path information of the finder such as a pentaprism, information on the light flux passage position and the incident angle on the photometric lens surface 51 is obtained. calculate. By applying the incident angle obtained here to ω ₂ in Expression (2), the area ratio of the center lens beam to the peripheral beam when observed on the photometric lens surface 51 is obtained.

  In step s3, the shape of the central light beam of the photographing lens when observed on the photometric lens surface 51 and the shapes of the central light beam and the peripheral light beam shape are estimated using Equation (2) and calculated. Since the central luminous flux is obtained only from the F value and the information of the finder optical path, the peripheral luminous flux shape when observed on the photometric lens surface 51 from the central luminous flux shape and the area ratio of the peripheral luminous flux obtained in step s2 is shown in FIG. The analogy is as follows: B).

  In steps s1 to s3, direct light that is not diffused by the focusing screen is calculated. In step s4, the diffusion of the focusing screen is determined based on the light beam shape observed with the photometric lens surface 51 obtained in step s3. Find the diffused light when it is diffused by the surface. The diffused light is considered as shown in FIG.

  FIG. 7 is a schematic view of the relationship between the direct light 71 incident on the focusing screen and the diffused light beam 72 emitted from the focusing screen. (A), (B), and (C) show diffused light when the range of direct light is different, and the diffused light is obtained depending on the beam width of the direct light. This diffused light can be calculated by calculating in the system from the light beam shape obtained by s3.

  However, since the relationship between direct light and diffused light can be expressed by a fixed function, the camera body holds functions of diffused light corresponding to multiple light beam widths in advance according to the width of the light beam shape. Calculation can be simplified.

  Next, in step s5, the amount of light incident on the photometric lens is obtained.

FIG. 8 shows the diffused light beam 72 and the photometric lens 18, and θ _r and θ _t have the same values as in FIG.

Since the amount of light received by the photometric sensor is equal to the amount of light that has passed through the photometric lens, the amount of light on the photometric sensor can be obtained by calculating the integral value of the function of the diffused light within the range overlapping the photometric lens. Assuming that the function of diffused light is P _F (θ), the amount of incident light on the photometric lens surface is

Can be calculated as These θ ₁ and θ ₂ are variables indicating angles in the vertical direction and depth direction of FIG.

  In the above steps s1 to s5, the light quantity distribution on the photometric sensor in the photographing system under a certain condition can be obtained. As a result, the light quantity ratio between the imaging surface and the photometric sensor can be obtained, and the photometric output correction value can be calculated in step s6.

[Example 2]
In the above embodiment, the photometric output is corrected using the calculated photographing lens beam. However, the application of the present invention is not limited to this, and it may be used by being incorporated in a system that requires the shape of the photographing lens beam. For example, in an automatic focus detection device of a camera, vignetting correction can be performed by knowing the reach of the light beam to the focus detection element.

  FIG. 9 is a schematic diagram of a main part of the camera system in the present embodiment.

  In a general single-lens reflex camera, a phase difference focus detector is incorporated for focus detection, and the focus detection unit 91 often receives the light beam reflected by the sub mirror 92 at the lower part of the camera body. FIG. 10 is a schematic diagram of the phase difference focus detector 91. The photographing lens light beam reflected by the sub mirror passes through the temporary imaging surface 101, the field lens 102, and the diaphragm surface 103 and is focused on the focus detection element 105 by the secondary imaging lens 104.

  In such a phase difference focus detector, the amount of light entering the secondary imaging lens can be efficiently calculated by obtaining the light beam incident on the diaphragm surface 103. FIG. 11 shows a light beam shape as seen on the diaphragm surface of the phase difference detector, and the expression (2) can also be applied to this calculation. In this case, ω2 is an incident angle to the focus detection element, which can be calculated from the distance information of the exit pupil and the optical path information of the focus detection unit as in the case of the first embodiment. Since the photographic lens beam shape on the focus detection element is obtained by these calculations, the phase difference focus detection device can calculate the photographic lens beam incident on the diaphragm surface, that is, the amount of light reaching the focus detection element. It becomes.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

1 interchangeable lens, 2 camera body, 3 lens microcomputer, 4 camera microcomputer,
11 imaging system, 12 QR mirror, 13 image sensor, 14 focusing screen,
15 pentaprism, 16 eyepiece, 17 observer's pupil position, 18 photometric lens,
19 Light-receiving element for photometry, 31 Center beam of the taking lens, 32 Peripheral beam of the taking lens

Claims (7)

In a camera system in which an interchangeable lens having a photographing system can be attached to and detached from the camera body,
Storage means for storing information on at least the peripheral light amount of the photographing lens, the open F value, and the exit pupil distance;
A camera system comprising a calculation means for calculating a light flux shape of the photographing lens using the information. A light receiving means for receiving a light beam that has passed through the photographing system;
The camera system according to claim 1, further comprising a correction unit that corrects a deviation between a luminance distribution of the subject and an illuminance distribution of the subject image based on a signal obtained by the light receiving unit. The camera system according to claim 1, wherein the calculating unit that calculates the light beam shape of the photographing lens performs an operation by analogy that the light beam shape is elliptical. The camera system according to claim 1, wherein the correction unit performs correction using information stored in the storage unit and a calculation result of the calculation unit. The camera system according to claim 1, further comprising storage means for storing information relating to the camera body. 6. The storage means stores information on a focal length of a lens provided on the focusing screen, diffusion characteristics of the focusing screen, and information on an optical system between the focusing screen and the light receiving means. The memory | storage means as described in. The camera system includes a correction unit that performs correction using information in a storage unit that stores information on the camera body.