JP2003241302A - Single-lens reflex camera and camera system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a subject image observed through a viewfinder becomes dark since subject light in the visible-wavelength range is divided and guided to both a finder optical system and a focus detection optical system. <P>SOLUTION: The single-lens reflex camera having an optical unit which can move into and out of an optical path of photography, and viewfinder optical systems 5 to 7 and a detection optical system 9 to which luminous flux is guided by the optical unit arranged in the optical path of photography, is characterized in that the optical unit is constituted by providing a 1st optical surface 2 which separates a luminous flux component below a wavelength range close to the infrared range of the visible-wavelength range or a luminous flux component in a specified visible-wavelength range from the luminous flux entering the optical path of photography and guides it to the finder optical systems and a 2nd optical surface 3 which guides the remaining luminous flux component after the luminous component is separated by the 1st optical surface to the detection optical system. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-lens reflex camera equipped with an optical unit that can move forward and backward with respect to a photographing optical path and guides a light beam to a finder optical system and a detection optical system while being arranged in the photographing optical path. It is a thing.

[0002]

2. Description of the Related Art A single-lens reflex camera is generally equipped with an autofocus function, and both a viewfinder optical system and a focus detection optical system for autofocus are provided before exposure to the image pickup surface. It is necessary to split and guide the subject light.

In a conventional single-lens reflex camera, a half mirror that is retracted outside the photographing optical path at the time of photographing is arranged behind the photographing optical system, and a part of the subject light in the visible wavelength range obtained by the reflection of the half mirror is arranged. The subject light guided to the finder optical system and transmitted through the half mirror is guided to the focus detection optical system by another mirror.

Since the subject light used in the finder optical system is the light that is directly observed by the observer, it is naturally necessary to set it in the visible wavelength range. On the other hand, the subject light used for imaging varies depending on the spectral sensitivity of the film or imaging device arranged on the imaging surface, but is considered to be light in the visible wavelength range that generally corresponds to the luminosity. Therefore, it is general that the subject light used in the focus detection optical system is also light in the visible wavelength range.

As described above, if the finder observation and the focus detection are performed using the subject light having substantially the same wavelength range, the focal position shift (that is, the focus shift) caused by the difference in the chromatic aberration of the photographing optical system is performed. Can be prevented in advance.

[0006]

However, in the above-mentioned most general configuration of the single-lens reflex camera,
Since the subject light in the visible wavelength range is divided and guided to both the finder optical system and the focus detection optical system, the subject image observed by the finder becomes dark.

In order to solve this problem, if the quantity of light guided to the finder optical system is increased, the quantity of light guided to the focus detection optical system becomes small, and it becomes difficult to detect the focus of a low-luminance object. .

Therefore, the present invention provides a single-lens reflex camera capable of observing a bright viewfinder image and at the same time capable of guiding a sufficient amount of subject light to a detection optical system such as a focus detection optical system. It is intended to be provided.

[0009]

In order to achieve the above-mentioned object, in the first invention of the present application, a luminous flux is generated by an optical unit capable of advancing and retreating with respect to a photographing optical path and the optical unit arranged in the photographing optical path. In a single-lens reflex camera having a finder optical system and a detection optical system to be guided, the optical unit is used to separate a light flux component having a wavelength of a visible wavelength range below a wavelength range near an infrared range from a light flux incident on a photographing optical path. Then, there is provided a first optical surface that guides the finder optical system and a second optical surface that guides the remaining light flux component separated by the first optical surface to the detection optical system.

[0010] Also. In the second invention of the present application, in a single-lens reflex camera having an optical unit capable of advancing and retracting with respect to a photographing optical path, and a finder optical system and a detection optical system in which a light beam is guided by the optical unit arranged in the photographing optical path, The optical unit has a first optical surface that separates a light beam component in a predetermined visible wavelength range from a light beam that has entered the photographing optical path and guides it to the finder optical system, and the remaining light beam component that has been separated by the first optical surface. And a second optical surface that guides the luminous flux component of to a detection optical system such as a focus detection optical system or a photometric optical system.

According to the first and second inventions, most of the components of the light flux incident on the photographing optical path in the visible wavelength region can be guided to the finder optical system, and the remaining light flux components of sufficient light amount (for example, for example). , Components in the wavelength range between 600 nm and 750 nm) can be guided to the detection optical system.

Here, when the remaining light flux components are used for focus detection, only light fluxes that have passed through different parts of the exit pupil of the photographing optical system are extracted and recombined as in the phase difference detection method. In an optical system for forming an image, it is not always necessary to perform focus detection by using subject light in the visible range equivalent to that of a finder optical system, and focus detection using light outside a predetermined visible wavelength range as in the present invention. It is also possible to do However, since a wavelength band different from the wavelength band used for imaging is used, in general, various aberrations are not always well corrected.

Therefore, in the single-lens reflex camera having the structure of the present invention, as the interchangeable lens, a lens in which various aberrations are properly corrected up to the wavelength range of the remaining light beam component is used, or as a simple method, A means is conceivable in which correction information such as a shift amount of the focal position in the wavelength range of the remaining light flux component is stored in advance in a storage device in the interchangeable lens.

When used for photometry, the infrared reflectance of the subject is estimated by comparing with the subject light in the visible wavelength range that is separately extracted from the optical path of the finder optical system, and the subject itself is estimated. It may be used as a judgment material for estimating the illumination light source illuminating the subject.

By utilizing this result, it is possible to extract a portion that should be emphasized in the photometry of the subject light, and to set the white balance more appropriately in a single-lens reflex camera using an image pickup device. .

Here, in the case where the first optical surface is a dichroic mirror formed by forming a dielectric multilayer film on a thin plate, the normal line of the mirror surface of this dichroic mirror and the optical axis of the photographing optical system. Let θ1 be the angle formed by, let T1 be the transmittance with respect to a light beam having a wavelength of 600 nm whose incident angle to the dichroic mirror is 45 °, and T2 be a transmittance with respect to a light beam having a wavelength of 700 nm: 35 ° <θ1 <55 ° ... T1 It is preferable to satisfy the condition of <20% ... 70% <T2.

The conditional expression is that when the dichroic mirror is arranged in the photographing optical path, when the subject light is reflected in an appropriate direction and guided to the finder optical system, the normal line of the mirror surface of the dichroic mirror and the light of the photographing optical system. It is an expression showing an appropriate relationship that the angle formed with the axis should be satisfied. If the angle is set outside the range of this conditional expression, it is against the downsizing of the camera.

The conditional expressions (1) and (2) define the transmittance of the dichroic mirror at each wavelength by taking the wavelengths of 600 nm and 700 nm as typical values of the predetermined visible wavelength range and the wavelength range on the infrared side of the predetermined visible wavelength range. It is a conditional expression. Since the transmittance of the dichroic mirror changes depending on the incident angle of the light beam, the representative value is defined here when the incident angle is 45 °. 45 °
Represents a representative light ray corresponding to the incident angle of the light ray that is incident on the dichroic mirror in parallel with the optical axis of the photographing optical system when the value of θ1 in the conditional expression is 45 °.

As defined in these conditional expressions,
The first optical surface (dichroic mirror) of the present invention mainly reflects most of visible components of the subject light flux and transmits components near the infrared region.

Incidentally, it is generally known that the sensitivity of the eyes of a normal observer is such that it becomes strong with respect to light having a wavelength of about 450 nm to about 650 nm.
The above-mentioned conditional expression, is a typical value T1 of transmittance in a wavelength range where eye sensitivity is high and a typical value T1 of transmittance in a wavelength range where eye sensitivity is low.
2 shows the relationship with 2.

Further, the second optical surface is formed by forming a vapor deposition film on a thin plate, and the remaining luminous flux component is reflected in a direction different from the first optical surface with respect to the optical axis of the photographing optical system. In the case of the vapor deposition film mirror, the angle formed by the normal line of the mirror surface of the vapor deposition film mirror and the optical axis of the photographing optical system is θ2, and the angle of incidence on the vapor deposition film mirror is 45 ° with respect to a light beam of wavelength 700 nm. When the reflectance is R3, the condition of 25 ° <θ2 <50 ° ... 80% <R3 ... may be satisfied.

The conditional expression is that the dichroic mirror, which is the first optical surface, is arranged at a predetermined angle with respect to the optical axis of the photographing optical system, and the vapor deposition film mirror, which is the second optical surface, is efficiently arranged. This is an expression that defines the conditions that must be satisfied for placement. If the angle is set outside the range of the conditional expression, it is against the downsizing of the camera as in the case of the above conditional expression.

The conditional expression is a conditional expression which defines the reflectance of the vapor deposition film mirror at this wavelength, taking a wavelength of 700 nm as a representative value in the wavelength range near the infrared region.
Since the reflectance in this case also generally changes depending on the incident angle of the light beam as in the case of the dichroic mirror, the representative value is defined here at the incident angle of 45 °. 45 ° represents a typical light beam corresponding to the incident angle of the light beam that enters the vapor deposition film mirror in parallel with the optical axis of the photographing optical system when the value of θ2 in the conditional expression is 45 °.

Here, a general vapor deposition film mirror is used as the second optical surface, but it is also possible to use a metal reflection mirror whose reflectance characteristic varies little with wavelength, and it is also possible to use a metal reflection mirror near the infrared region. A dichroic mirror made of a dielectric multilayer film may be considered in order to guide only the subject light in a specific wavelength range.

Further, when the first optical surface is a dichroic mirror formed by forming a dielectric multilayer film on a thin plate, this dichroic mirror has a wavelength of 600 n.
It is also possible to provide a specific wavelength having a transmittance of 50% for a light ray having an incident angle of 45 ° between m and the wavelength of 750 nm, and the specific wavelength may be different in the mirror surface.

In particular, when placed in the photographing optical path, the specific wavelength of the portion of the dichroic mirror surface arranged on the side closer to the image pickup surface is λ1, and the specific wavelength of the portion arranged on the side farther from the image pickup surface. It is desirable to configure the dichroic mirror so that the specific wavelength continuously changes so that λ1> λ2 when λ2.

When using a dichroic mirror as in the present invention, it must be noted that its spectral transmittance or spectral reflectance characteristics change depending on the incident angle of a light beam. When the dichroic mirror is obliquely arranged in the shooting optical path, when the subject light emitted from the exit pupil of the shooting optical system at a finite distance is incident on the dichroic mirror, it is determined by the incident position on the surface of the dichroic mirror. The incident angle will be different. Therefore, if the spectral transmittance characteristics of the dichroic mirrors are made uniform, color unevenness will be observed in the subject image formed on the focusing screen of the finder optical system depending on the position in the finder screen.

The incident angle of the subject light is relatively large at the mirror portion arranged on the side closer to the image pickup surface, and conversely the incident angle of the subject light is relatively small at the mirror portion arranged on the side farther from the image pickup surface. Become. This change in the incident angle becomes larger as the position of the exit pupil of the photographing optical system becomes closer to the image pickup surface, and becomes almost 0 when the position of the exit pupil of the photographing optical system is arranged at a position infinitely far from the image pickup surface. .

When an interchangeable lens for a single-lens reflex camera is used as a photographing optical system, the position of the exit pupil is designed to be located within a finite predetermined range from the image pickup surface in order to downsize the photographing optical system. It is generally done. Therefore, although the position of the exit pupil changes depending on the shooting lens attached, assuming the most common position of the exit pupil,
It is preferable that the spectral characteristics of the dichroic mirror be different in advance on the mirror surface in consideration of changes in the spectral characteristics that change according to the incident position on the surface of the dichroic mirror.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows an optical configuration of a single-lens reflex camera which is a first embodiment of the present invention. In the figure, 1 is a taking lens that can be attached to and detached from the camera body, 2 is a first mirror that can move forward and backward with respect to the taking optical path, and 3 is arranged behind the first mirror 2, It is a second mirror that can move forward and backward with respect to the optical path for photographing together with the mirror 2. It should be noted that the first mirror 2 and the second mirror 3 constitute an optical unit that can move forward and backward with respect to the photographing optical path.

An image pickup surface 4 of the taking lens 1 is provided with an image pickup device such as a film or CCD.

Reference numeral 5 is a focusing screen, 6 is an optical member for forming an erect image, and 7 is an eyepiece lens, and these constitute a finder optical system. Reference numeral 8 is a pupil position of a photographer who observes the viewfinder, and 9 is a focus detection optical system.

In the camera of the present embodiment, the first mirror 2 and the second mirror 3 are:
As shown in FIG. 1, the normal line of the mirror surface is arranged in the photographing optical path between the photographing lens 1 and the photographing surface 4 so as to have an inclination of 45 ° with respect to the photographing optical axis.

The first mirror 2 reflects incident object light upward to form an image on the focusing screen 5, and guides it as an erect image to the eyepiece 7 by the optical member 6 for forming an erect image.
As a result, the subject image on the focusing screen 5 is enlarged and guided to the observer's pupil position 8 to observe the finder image.

Further, the second reflecting mirror 3 is arranged so that the normal line of its mirror surface makes an angle of 40 ° with the photographing optical axis, so that the subject light transmitted through the first mirror 2 is substantially formed. It is reflected downward and guided to the focus detection optical system 9, and the photographing lens 1
The focus adjustment state of is detected. Then, when the photographing operation is performed after the focus adjustment of the photographing lens 1 and the observation through the finder optical system are performed, the first mirror 2 and the second mirror 3 are moved from the photographing lens 1 to the imaging surface 4. It retracts to a position where it does not substantially interfere with the shooting light flux reaching to.

The present embodiment is a so-called general-purpose single-lens reflex camera, and is characterized by the characteristics of the first mirror 2 used here.

FIG. 2 shows the spectral transmittance characteristics of the first mirror 2 shown in FIG. 1 with respect to a light beam having an incident angle of 45 °. As shown in FIG. 2, the first mirror 2 of the present embodiment has a spectral transmission for a light beam in a wavelength range of 400 nm to 630 nm (a predetermined visible wavelength range) in a visible wavelength range of generally 400 nm to 750 nm. The ratio is set low, and the wavelength range is from about 660 nm to 750 nm (wavelength range near infrared in visible wavelength range) and about 750 nm.
The spectral transmittance for light rays in the wavelength range from nm to 800 nm (wavelength range in the near infrared region) is set high.

Therefore, most of the subject light reflected by the first mirror 2 in this embodiment and guided to the focal plane of the focusing screen 5 is light having a wavelength only in the predetermined visible wavelength range.

On the other hand, the first mirror 2 in this embodiment
The majority of the subject light that passes through is light having a wavelength longer than 660 nm. Here, generally, a wavelength range of approximately 750 nm or more (25,000 nm or less) is called a near infrared region. Then, the second mirror 3 of the present embodiment is configured to reflect at least such a light flux component in the wavelength region near the infrared region or in the near infrared region and guide it to the focus detection optical system 9. In this embodiment, the second mirror 3 is composed of an aluminum vapor deposition thin film and a dielectric thin film.

FIG. 3 shows the spectral reflectance characteristics of the second mirror 3 of this embodiment. As shown in FIG. 3, the second reflection mirror 3 sets a high reflectance for light in a wavelength range of at least a wavelength near the infrared range of 700 nm, and the red light transmitted through the first mirror 2 is red. Light near the outer region or in the near infrared region is guided to the focus detection optical system 9.

The focus detection optical system 9 is, as shown in FIG.
Condensing lens 10, reflecting mirror 11, secondary imaging lens 12
And a pair of light receiving elements 13. Second
The subject light reflected by the mirror 3 (light in the near infrared region or near infrared region) forms a subject image at a position substantially equivalent to the imaging surface 4.

The condenser lens 10 is equivalent to the image pickup surface 4
It is arranged in the vicinity of the next image forming surface and collects the light flux so as to form an image of the exit pupil of the photographing lens 1 on the lens surface of the secondary image forming lens 12.

The secondary imaging lens 12 has at least a pair of lens parts, and these lens parts are the photographing lens 1.
Are configured to correspond to different parts on the exit pupil surface of the. At least a pair of lens portions of the secondary imaging lens 12 form a subject image on the pair of light receiving elements (line sensors) 13, respectively.

Then, by determining the relative positions of the two subject images formed on the pair of light receiving elements 13 (by the so-called phase difference detection method), the taking lens 1
The focus adjustment state of can be detected.

Here, the principle of focus detection by the phase difference detection method will be described with reference to FIG. As shown by the solid line in FIG. 6A, when the light flux that has passed through the condenser lens 10 is focused on the planned focal plane S, a part of the light flux is generated by the secondary imaging lens 1
An image is formed again on the line sensors 13a and 13b by 2a and 12b. Therefore, when the focus is on the planned focal plane, the two line sensors 13a and 13b take images 2
The two images are formed at substantially the same position on the line sensor as shown in FIG.

On the other hand, as shown by the alternate long and short dash line in FIG. 6A, in the so-called rear focus state in which the light flux passing through the condenser lens 10 is focused before the planned focal plane S ', two lines are formed. The positions of the two images captured by the sensors 13a and 13b are displaced as shown in FIG. 6 (c).

Further, in the so-called front focus state in which the light flux passing through the condenser lens 10 is focused after the planned focal plane, the two image positions picked up by the two line sensors 13a and 13b are: Misalignment occurs in the direction opposite to the rear pin state.

Therefore, the line sensors 13a, 13b
By detecting the deviation direction and the deviation amount of the two images imaged in, it is possible to calculate the movement direction and the movement amount of the focus adjustment lens necessary for focusing on the planned focal plane.

The reflecting mirror 11 is used to bend the detection optical path in order to reduce the overall size of the focus detection optical system 9.

The focus detection optical system 9 of the present embodiment is thus a general secondary imaging optical system, and the light receiving element 1
The phase difference between at least one pair of subject images formed on the image pickup device 3 is detected. At this time, the subject image formed on the light receiving element 13 is different from the subject image formed on the imaging surface 4 because the wavelength range of the subject light is different.

However, in the phase difference detection type focus detection optical system, in order to calculate the shift amount of the focus position of the photographing lens from the shift amount of the pair of images formed on the light receiving element 13, a light beam used for focus detection is obtained. Since it is indispensable to perform some kind of correction calculation because the light flux used for shooting and the light flux used for shooting are not equal, it is possible to cope with the difference in the wavelength range used by adding a similar correction calculation. is there.

That is, to drive the focus adjusting lens included in the taking lens 1 so that the focus can be adjusted accurately in the wavelength range used in the photographing optical system from the shift signal in the wavelength range used in the focus detecting optical system. It may be set in advance so as to perform a predetermined correction on the information.

At this time, since the aberration correction state varies depending on the attached photographing lens, the difference in the correction amount caused by the difference in the wavelength range used differs. Such information may be stored in advance and used appropriately.

As described above, in the present embodiment, the first mirror 2 has a wavelength of 600 nm and a wavelength of 750 nm.
A dichroic mirror having a transmittance of 50% at a specific wavelength between is used. For this reason, most of visible light can be guided to the finder optical system, and the photographer can observe a bright finder image as compared with the conventional case of using a half mirror that divides light in the visible wavelength range evenly. it can. Further, since the second mirror 3 can also guide a sufficient amount of light to the light receiving element 13 which generally has high sensitivity to the wavelength region on the infrared side, the accuracy of focus detection does not deteriorate.

Here, in the present embodiment, the angles formed by the normals of the mirror surfaces of the first mirror 2 and the second mirror 3 to the photographic optical axis are 45 ° and 40 °, respectively. The structure satisfies the expressions and.

As the first mirror 2 and the second mirror 3, the first mirror having the spectral characteristic shown in FIG. 2 and the second mirror having the spectral characteristic shown in FIG. 3 are used. Therefore, the above conditional expressions and are satisfied.

Further, in the present embodiment, as shown in FIG. 4, if the distance from the image pickup surface 4 to the exit pupil of the photographing lens 1 is P and the length of the image pickup surface 4 in the short side direction is 2H, the focusing screen is shown. When projecting the entire range of the image pickup surface onto the image pickup surface 5, the incident angle to the first mirror 2 of the light ray that exits from the center of the exit pupil of the photographing lens 1 and reaches the upper end of the center of the image pickup surface 4 is θH. The angle of incidence of a light ray that exits from the center of the exit pupil of the lens 1 and reaches the center of the imaging surface 4 on the first mirror 2 is θM, and exits from the center of the exit pupil of the taking lens 1 and the center of the imaging surface 4 When the incident angle of the light beam reaching the lower end on the first mirror 2 is θL, θH, θM, and θL are respectively expressed as follows.

.Theta.M = .pi. / 4 ... .theta.H = .theta.M + tan-1 (H / P) .apprxeq..pi. / 4 + H / P ... .theta.L = .theta.M-tan-1 (H / P) .apprxeq..pi. / 4-H / P. The incident angle of the light ray incident on the mirror 2 of 1 is
In the center line portion of the image pickup surface 4, it changes by approximately ± H / P radians above and below the image pickup surface 4.

The first mirror 2 of this embodiment is a dichroic mirror that mainly reflects light in the visible wavelength range and transmits light in the near infrared wavelength range or near infrared wavelength range, as described above. In this case, the characteristics as shown in FIG. 2 are generally realized by utilizing the interference effect of the dielectric multilayer film. However, in this case, a phenomenon occurs in which the spectral characteristics change according to the change in the incident angle of the light beam.

In FIG. 5, incident angles 45 °, 35 ° and 55 ° are applied to the first mirror 2 having the spectral characteristics shown in FIG.
Shows the spectral transmittance characteristics when a light beam is incident. In FIG. 5, a represents the spectral transmittance characteristics when the incident angle is 45 °, b represents the incident angle of 35 °, and c represents the spectral transmittance characteristics when the incident angle is 55 °.

As shown in this figure, in the first mirror 2 of this embodiment, the wavelength 60 is changed according to the change of the incident angle of the light beam.
The spectral transmittance is 50 in the range of 0 nm to 750 nm.
The specific wavelength that becomes% changes.

In the present embodiment, the object image is observed from the finder optical system using the reflected light from the first mirror 2, but the spectral characteristics of the object light reaching according to the upper and lower positions of the screen are as described above. Since they are different, when the amount of light of the wavelength related to the sensitivity of the observer's eyes changes, a phenomenon occurs in which the color of the subject looks different.

It is generally known that the sensitivity of the human eye strongly reacts in the wavelength range of 400 nm to 650 nm, and it is perceived as a color change when the amount of light in a predetermined wavelength range of this wavelength range changes. Become. For example, the first
Of the wavelength 6 by the incident angle dependence of the spectral characteristic of the mirror 2 of
If the amount of light near 50 nm is different on the upper and lower sides of the screen, it will be perceived by the viewer as color unevenness in the vertical direction of the screen.

In order to prevent such a problem from occurring, it is sufficient that the incident angle dependence of the spectral reflectance of the first mirror 2 is reduced, but in the dichroic mirror utilizing the interference of the dielectric multilayer film. It is extremely difficult in reality.

As another solution, the spectral transmittance is 5
It is also conceivable to set a specific wavelength of 0% to a wavelength range that does not affect the sensitivity of the eyes so that the incident angle dependence of the spectral characteristics is not substantially recognized as color unevenness on the screen. However, with such a configuration, the first
The mirror 2 causes a large amount of light of unnecessary wavelength to be reflected by the viewfinder optical system, further reducing the amount of light guided to the focus detection optical system, which causes a problem in the focus adjustment function under low illuminance. Occurs. Therefore, it is preferable to adopt the second embodiment described below.

(Second Embodiment) In the second embodiment of the present invention, the spectral characteristics of the dichroic mirror provided in the first mirror 2 are set in the screen position in consideration of the incident angle dependency of the dichroic mirror as described above. It is configured to be continuously different according to. That is, the spectral characteristic of the dichroic mirror of the first embodiment is determined in consideration of the fact that the spectral characteristic of the dichroic mirror of the first embodiment changes as shown in FIG. 5 according to the incident angle of a light beam.

Specifically, when the dichroic mirror is placed in the photographing optical path, the wavelength of 600 nm and the wavelength of 700 are set.
The dichroic mirror is configured to have a transmittance of 50% for a light ray having a specific wavelength between nm and an incident angle of 45 ° on the optical axis.

At this time, in the portion of the mirror surface of the dichroic mirror that is arranged on the side closer to the image pickup surface 4,
The transmittance of the light of the specific wavelength having the incident angle smaller than 45 ° is 50%, and conversely, the transmittance of the light having the specific wavelength of the incident angle larger than 45 ° is arranged in the portion arranged farther from the imaging surface 4. Is configured to be 50%. As a result, it is possible to eliminate color unevenness in the screen due to the incident angle dependency of the dichroic mirror that is the first mirror 2.

By the way, in order to have such an optical effect, the dichroic mirror is set to a wavelength of 600.
nm and a wavelength of 700 nm have a specific wavelength having a transmittance of 50% with respect to a light ray having an incident angle of 45 °, and are arranged on the side closer to the image pickup surface 4 when arranged in the photographing optical path. When the specific wavelength is λ1 and the specific wavelength of the portion arranged on the side far from the imaging surface is λ2, the specific wavelength may be continuously changed so that λ1> λ2.

As shown in the above equations, the angle of incidence of the light ray incident on the first mirror 2 is approximately dependent on the position on the image pickup surface 4 and the distance from the image pickup surface 4 to the exit pupil of the taking lens 1. Since it is determined, when the position of the exit pupil of the taking lens 1 changes, the incident angle of the light ray changes. Here, the color unevenness of the screen is minimized at intermediate positions among the exit pupil positions of various photographing lenses.

In the first and second embodiments described above, the second mirror 3 is a reflecting mirror formed by thin film vapor deposition on aluminum, and almost all the light rays transmitted through the first mirror 2 are focus detecting optical systems. Although the case of leading to 9 is described, in order to reduce an error caused by chromatic aberration that occurs during focus detection, a dichroic mirror that does not reflect a long wavelength longer than a predetermined wavelength so as to further limit the wavelength range used for focus detection. May be Of course, for the same purpose, a filter for blocking infrared light may be separately provided in the focus detection optical system 9.

The light receiving element 13 for focus detection in each of the above-described embodiments mainly receives subject light in the near-infrared wavelength region or near-infrared wavelength region. The subject image obtained here is, for example, a finder optical system. Whether the subject to be photographed is a subject that reflects light in the near infrared region or near infrared region by comparing with the subject image in the visible wavelength range from the photometric optical system configured to separately extract the light flux from It is possible to This makes it possible to assist in estimating the type of subject.

[0073]

As described above, according to the present invention,
Most of the luminous flux components in the visible wavelength range of the luminous flux incident on the shooting optical path can be guided to the finder optical system, and the remaining luminous flux components of sufficient light quantity can be guided to the detection optical system.
It is possible to perform highly accurate focus detection and the like even under low illuminance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a single-lens reflex camera that is a first embodiment of the present invention.

FIG. 2 is a graph showing a spectral transmittance characteristic of a first mirror (dichroic mirror) used in the single-lens reflex camera of the first embodiment.

FIG. 3 is a graph showing a spectral reflectance characteristic of a second mirror (a vapor deposition film mirror) used in the single-lens reflex camera of the first embodiment.

FIG. 4 is an explanatory diagram of an incident angle of a light ray on the first mirror of the first embodiment.

FIG. 5 is a graph illustrating the incident angle dependence characteristic of the spectral transmittance characteristic of the first mirror of the first embodiment.

FIG. 6 is a diagram illustrating the principle of focus detection by a phase difference detection method.

[Explanation of symbols]

1 Shooting lens 2 first mirror 3 second mirror 4 Imaging surface 5 Focus plate 6 Optical member for erect image formation 7 eyepiece 8 Pupil position. 9 Focus detection optical system

Claims (10)

[Claims] 1. A single-lens reflex camera having an optical unit capable of moving forward and backward with respect to a photographing optical path, and a finder optical system and a detection optical system in which a light beam is guided by the optical unit arranged in the photographing optical path, The optical unit separates a light flux component having a wavelength equal to or shorter than a wavelength range near infrared in the visible wavelength range from a light flux incident on a photographing optical path, and guides the separated light flux component to the finder optical system; A single-lens reflex camera having a second optical surface for guiding the remaining light flux component separated from the light flux component by the second optical surface to the detection optical system. 2. A single-lens reflex camera having an optical unit capable of moving forward and backward with respect to a shooting optical path, and a finder optical system and a detection optical system in which a light beam is guided by the optical unit arranged in the shooting optical path, The optical unit separates a luminous flux component in a predetermined visible wavelength range from a luminous flux incident on a photographing optical path and guides it to the finder optical system, and a luminous flux component is separated by the first optical surface. A single-lens reflex camera having a second optical surface for guiding the remaining luminous flux component to the detection optical system. 3. The single-lens reflex camera according to claim 1, wherein the detection optical system is a focus detection optical system for detecting a focus adjustment state of the photographing optical system. 4. The single-lens reflex camera according to claim 1, wherein the detection optical system is a photometric optical system for detecting the brightness of a subject. 5. The wavelength range of the remaining luminous flux component is 600
The single-lens reflex camera according to claim 1 or 2, wherein the single-lens reflex camera includes at least a part of the wavelength range from nm to 750 nm. 6. The first optical surface is a dichroic mirror formed by forming a dielectric multilayer film on a thin plate, and a normal line of a mirror surface of the dichroic mirror and an optical axis of a photographing optical system. Assuming that the angle formed is θ1, the transmittance for a light beam having a wavelength of 600 nm whose incident angle to the dichroic mirror is 45 ° is T1, and the transmittance for a light beam having a wavelength of 700 nm is T2, then 35 ° <θ1 <55 ° T1 < The single-lens reflex camera according to claim 1 or 2, wherein a condition of 20% 70% <T2 is satisfied. 7. The second optical surface is formed by forming a vapor deposition film on a thin plate, and the remaining light flux component is directed in a direction different from that of the first optical surface with respect to the optical axis of the photographing optical system. The angle formed by the normal line of the mirror surface of the vapor deposition film mirror and the optical axis of the photographing optical system is θ2, and the incident angle to the vapor deposition film mirror is 4
The reflectance for a light beam having a wavelength of 700 nm, which is 5 °, is R3.
The single-lens reflex camera according to claim 1 or 2, wherein the following condition is satisfied: 25 ° <θ2 <50 ° 80% <R3. 8. The first optical surface is a dichroic mirror formed by forming a dielectric multilayer film on a thin plate, and the dichroic mirror has a wavelength of 600 nm and a wavelength of 7 nm.
The single eye according to claim 1 or 2, wherein a specific wavelength having a transmittance of 50% with respect to a light ray having an incident angle of 45 ° is provided between the wavelength and 50 nm, and the specific wavelength is different in a mirror plane. Reflex camera. 9. In the dichroic mirror, the specific wavelength is set to λ1 in a portion of a mirror surface in a state of being arranged in a photographing optical path, which is closer to an image pickup surface, and a mirror surface on a side farther from the image pickup surface is set. 9. The single-lens reflex camera according to claim 8, wherein the specific wavelength continuously changes such that λ1> λ2, where λ2 is the specific wavelength. 10. A camera system including the single-lens reflex camera according to claim 1 and a taking lens that is detachable and replaceable with respect to the camera.