JPH07301747A - Optical devices provided with focus detection device - Google Patents

Abstract

PURPOSE:To obtain a focus detection device by which focusing is attained by driving a lens once by correcting a lens driving amount error equivalent to a difference between the best focusing correction eigenvalue in the zone of a focus lens initial stopping position and the best focusing correction eigenvalue in the zone of an aimed focusing position. CONSTITUTION:A focusing difference between an arithmetically operated focusing position by an arithmetic means 19 and the best focusing position of a photographing lens corresponding to each focus zone, difference data between the focusing difference at an infinity end and the focusing difference at the closest-distance end, and the data on the moving amounts of all the lenses are stored in a ROM 22 as the characteristic data of the photographing lens. The means 19 transmits a data readout instruction to a control means 21 on a lens side, and the means 21 refers to output from a pulse counter 25, reads out the data on the focusing difference from the ROM 22 and transmits it to a readout means 19. The means 19 corrects the arithmetically operated focusing position by referring to the data and transmits it to the means 21 as a lens driving pulse. The means 21 drives a driving motor 23 corresponding to the lens driving pulse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device having a focus detecting device, and more particularly, to a secondary image of a focus position of a main imaging lens such as a photographing lens of a photographic camera or a video camera or other lens. The present invention relates to an improvement of an optical device having a focus detection device that automatically detects a positional relationship.

[0002]

2. Description of the Related Art Conventionally, various cameras having a focus detection device have been proposed. Among these, for example, Japanese Patent Laid-Open No. 63-
In Japanese Patent No. 172110, a field lens is arranged in the vicinity of a planned image forming surface of a main image forming lens such as a photographing lens or a position equivalent thereto, and a secondary image forming optical system is arranged behind the field lens. The object image formed in the vicinity of the equivalent position is further divided into a plurality of secondary images, and the plurality of secondary images are respectively received by a plurality of light receiving means, and on the light receiving means surface of the plurality of secondary images. In the focus detection device that obtains the focus position of the main imaging lens (amount of defocus from the planned image formation surface) by obtaining the positional relationship between the focus position calculated by the focus detection device and the best focus position of the main imaging lens. An optical device has been proposed in which the difference between the values is stored in the storage unit of the main imaging lens as unique information (unique data) of the main imaging lens, and the movement amount of the focus lens is corrected so that the focus position is optimal during shooting. Are

[0003]

In an optical device having such a focus detection device, if the stored information is unique information for a single subject distance in the entire focus range, for other subject distances. May not be the best focus position. Therefore, in order to solve this problem, an optical device has been proposed in which the focus position is divided into a plurality of pieces, and unique information is given to each focus zone so that the best focus can be obtained over the entire focus range.

Although this method improves the final focusing accuracy, it corrects only the amount of lens movement corresponding to the unique information of the focus zone at the position where the main imaging lens is stopped when the object is out of focus. The focus lens is being driven to the in-focus position. For this reason, the focus may deviate by an amount corresponding to the difference between the unique information of the focus zone at the target position and the unique information of the focus zone that was initially stopped, and it may become impossible to focus only by driving the lens once.

In particular, when the main imaging lens is a wide-angle system, the difference in the value of the unique information at each focus position becomes relatively large with respect to the maximum defocus amount of the lens system, so that only one lens drive is required. Focusing becomes difficult.

The present invention divides the focus position into a plurality of
In the main imaging lens that has an eigenvalue for the best focus correction for each focus zone, the best focus correction eigenvalue of the focus zone at the initial stop position of the focus lens and the best focus correction eigenvalue of the focus zone at the target focus position It is an object of the present invention to provide an optical device having a focus detection device capable of correcting a lens driving amount error corresponding to the difference between the above and the above and thereby focusing with one lens driving.

[0007]

An optical device having a focus detecting device according to the present invention is an optical device in which a main imaging lens is detachable, and is composed of light beams passing through different parts of the pupil of the main imaging lens. Optical means for forming respective light distributions, light receiving means for receiving the light distributions, computing means for computing the focus position of the main imaging lens based on the positional relationship between the light distributions received by the light receiving means, the main imaging lens Focus lens position detection means provided in the, focus position calculated by the calculation means, and data regarding the focus difference between the best focus position of the main imaging lens and the focus difference and the close distance of the position according to the infinite distance. Storage means for storing data relating to the difference in focus between the corresponding positions, and data relating to the total amount of focus movement as unique data of the main imaging lens for each of the plurality of divided focus positions; Based on the focus position calculated by the calculation means and the signal from the focus position detection means, the movement amount of the focus lens for focusing is calculated by using the unique data read from the storage means. It is characterized in that a correcting means for correcting is provided.

[0008]

First, a method of moving the focus lens of the main imaging lens in the present invention will be described.

FIGS. 4A and 4B are schematic diagrams showing the structure of the focus detection device. As shown in FIG. 4 (A), the light flux that has passed through the pupil 1 when the main imaging lens is open forms an image on the planned image formation plane 2 when it is in focus. At this time
As shown in (B), the light fluxes that have passed through the two split pupils 3 and 4 form a subject image on the planned image forming plane 2 (at an equivalent position), and thereafter, in the vicinity of the planned image forming plane 2. A secondary image is formed on each of the light receiving elements 7 and 8 by the field lens 5 and the secondary image forming lens 6 which are arranged at.

When the main image forming lens is out of focus, the positional relationship of the secondary images on the light receiving elements 7 and 8 is different from the reference positional relationship when the focus is achieved.
The focus position (out-of-focus amount) can be calculated based on the phase shift of the image signal of No. 8.

By the way, in such a focus detecting apparatus, accurate focus position detection is established when the main imaging lens is an ideal aberration-free lens, and when the main imaging lens has aberrations. Is the calculated focus position,
There is a difference from the best focus position of the actual main imaging lens,
Even if the calculated focus position is aligned with the planned image formation plane 2, it may be slightly out of focus.

For example, as shown in FIG. 5, in the case of the main imaging lens in which the spherical aberration is not completely corrected, the spherical aberration corresponding to the diameter of the pupil 1 is a, and the divided pupil 3 or 4 is obtained.
Since the spherical aberration corresponding to the diameter of b is b, the focus positions at which the contrast is best differ from each other. This is because the spectral sensitivity characteristics of the photosensitive material used for general photographic lenses and the spectral sensitivity characteristics of the light receiving element used for the focus detection device are different, so that not only spherical aberration but also chromatic aberration is not completely corrected. The focus position may differ also in the imaging lens.

Therefore, the difference between the focus position corresponding to the spherical aberration a and the focus position corresponding to the spherical aberration b, including the difference in the focus position due to the influence of chromatic aberration, is used as the main image forming information of the main image forming lens. If it is stored in the storage unit of the lens, the best focus position can be obtained by calling this at the time of shooting and correcting the movement amount of the focus lens.

However, as shown in FIGS. 5A and 5B, when the spherical aberration (chromatic aberration) changes due to the difference in subject distances A and B, the focus position corresponding to the spherical aberration a becomes the spherical aberration b. It changes greatly compared to the corresponding focus position. Therefore, the difference between the focus positions corresponding to the spherical aberration a and the spherical aberration b also changes. If this difference is sufficiently within the allowable depth of field, there is no problem. However, this is a problem in a main imaging lens having a large variation of spherical aberration (chromatic aberration) or a main imaging lens having a large aperture and a shallow allowable image plane depth.

Therefore, in the present invention, in order to obtain the best focus regardless of the subject distance, the focus position is divided into a plurality of
A method is adopted in which the unique information is stored in the storage unit of the main imaging lens for each focus zone and is called at the time of shooting to correct the movement amount of the focus lens.

FIG. 1 is a schematic view of a main part of a first embodiment when a focus lens of a main imaging lens using this method is applied to a single-lens reflex camera as an optical device.

In the figure, a photographing lens composed of a focusing lens (focusing lens) 10 and an imaging lens 11 is
It corresponds to the main imaging lens according to the present invention. In the shooting, the light from the subject that has passed through these lenses 10 and 11 is the film surface 12
This is done by focusing on. Film side 1
2 corresponds to the planned image formation plane. The observation of the image field is the lens 10,
11, a reflection mirror 13, a condenser lens 14, a pentagonal prism 15, and an eyepiece lens 16.

For focus detection, the subject light that has passed through the focusing lens 10 and the imaging lens 11 and transmitted through a part of the anti-transmission part of the reflection mirror 13 and is reflected by the distance measuring mirror 17 is a field lens (not shown) and a secondary coupling. The image is separated by the image optical system, received by the light receiving element 18, the image signal of the light receiving element 18 is converted into a digital signal, and the calculation means 19 calculates the focus position (the amount of defocus from the film surface 12). The calculation means 19 corresponds to the calculation means of the present invention and also includes the correction means of the present invention.

On the photographing lens side, a lens side control means 21 connected to the camera side arithmetic means 19 by a contact point 20,
A ROM 22 corresponding to the storage means according to the present invention and a drive motor 23 for moving the focusing lens 10 in the optical axis direction are provided. The ROM 22 stores data on the focus position calculated by the calculation means 19 and the focus difference between the best focus position of the photographing lens corresponding to each focus zone, and the difference between the focus difference at the infinity end and the focus difference at the close end. Data of the total amount of lens movement is stored as unique data (specific information) of the taking lens.

The calculation means 19 sends a data read command to the lens-side control means 21 when calculating the focus position, and the lens-side control means 21 counts the pulses output from the pulse pattern formed on the helicoid 24. With reference to the output of the counter 25 (lens position detecting means), the focus difference data and the like are read from the ROM 22 and sent to the calculating means 19. The calculation means 19 corrects the calculated focus position with reference to the data, and sends it to the control means 21 as a lens drive pulse.

The control means 21 on the lens side drives the drive motor 23 in response to the lens drive pulse. Drive motor 2
The helicoid 24 is moved by the driving of No. 3, and the focusing lens 10 is moved accordingly, and the focusing is performed. The pulse counter 25 counts the pulses output from the pulse pattern formed on the helicoid 24,
When this count value matches the lens drive pulse,
The lens side control means 21 determines that the commanded amount of lens driving has been performed.

Next, referring to FIG. 2, the calculation contents of the calculation means 19 will be described in detail.

In step 1, the focus detection operation is started by turning on the photometric switch sw1 by half-pressing the shutter button (first stroke). In step 2, a data read command is transmitted to the control means 21 on the lens side. In step 3, the focus difference data (def) read from the ROM 22 and sent from the lens-side control means 21.
_A ) with the infinity focus difference and the near end focus difference data (Δdef _ABmax ) and the total lens movement amount data (x
_max ) is received and temporarily stored in the built-in memory of the calculating means 19.

In step 4, the light receiving element 18 is caused to perform photoelectric conversion of the secondary image for a predetermined time to accumulate the image. In step 5, the accumulated image signal is converted into a digital signal by the A / D converter. In step 6, the reference defocus amount (def _O ) is calculated based on this digital signal. In step 6a, the calculated reference out-of-focus amount (de
f _O) a by adding the focus difference (def _A), calculates a correction defocusing amount (def).

That is, def = def _O + def _A (1) is calculated.

In step 6b, def and Δdef
Lens drive amount of each focus of _ABmax (x, _{Δx ABmax)}
Convert.

That is, def → x Δdef _ABmax → Δx _ABmax is performed.

In step 7, each lens drive amount is calculated,
The final lens drive amount (x ') is obtained. That is,

[0029]

[Equation 1] Do.

In step 7a, the lens drive pulse (Px ') is converted to the final lens drive amount x'. That is, x ′ → Px ′ is performed.

If the lens driving pulse has a value within a predetermined range close to zero (within a range that can be regarded as in-focus), the focus detection operation is ended here. If the lens drive pulse has a value outside the range that can be considered to be in-focus, the lens drive pulse is transmitted to the lens-side control means 21 in step 8 to move the in-focus lens. When the lens drive end signal is received in step 9, the focus detection operation ends.

FIG. 3 shows a flow of the operation of the control means 21 on the lens side.

When the signal from the camera is received in step 10, the signal is discriminated in step 11. If it is a data read command, the position (zone) of the focus lens is detected in step 11a, and the process proceeds to step 12 and the focus difference data corresponding to the focus zone and the focus difference at infinity are approached from the ROM 22. The data on the difference in focus between the edges and the data on the movement of all lenses are read out. In step 13, the data and the lens state data are transmitted to the calculating means 19, and in step 14, control is passed to the camera side.

If the signal from the camera is a lens drive pulse, the process proceeds from step 11 to step 15 to energize the drive motor 23. When it is detected in step 16 that the pulse counter 25 has counted the number of pulses corresponding to the lens driving amount, the energization of the drive motor 23 is stopped. In step 17, a lens drive end signal is transmitted to the camera side, and in step 14, the operation ends.

Here, the correction means according to the present invention (2)
Regarding the equation, first, the case where the equation (2) is not corrected (conventional method) will be described. The focus lens has a focus position corresponding to the subject distance A, the subject is at the distance B, and the respective focus zones are the A zone and the B zone. Also, the shooting lens aims to obtain the best focus when the final point is focused, regardless of the subject distance,
It is assumed that the focus position is divided into a plurality of parts and at least the above-mentioned focus difference data is stored for each focus zone.

In the above state, after sw1 is turned on, the ROM
The focus difference data read from 22 is data corresponding to the A zone. Let this be def _A, and let the standard out-of-focus amount calculated by the focus detection device be def _O and the corrected out-of-focus amount be def. From equation (1), def = def _O + def _A , and the lens corresponding to def The focus lens moves by the drive amount (x).

At this time, considering the difference between the data def _A and the data def _B of the focus difference corresponding to the B zone, Δdef _AB = def _A −def _B , Δdef _AB = 0 or Δdef _AB is sufficiently within the depth of field. If the focus is within the set focus threshold value (the threshold value is usually set to 1/2 or less of the depth of field) for the focus determination, the focus lens is stopped by one drive x and the best focus is obtained. However, if the data Δdef _AB is outside the focus threshold value and Δdef _AB > 0, the focus lens outputs the data Δdef _AB.
The lens drive amount Δx _AB corresponding to def _AB is overshooted, and similarly, the data Δdef _AB is out of the focus threshold value, and if Δdef _AB <0, it is stopped by Δx _AB .

In either case, the focus detection device is def _O
= Δdef _AB, also when the data of the focus differences by the first stop zone and def _C, as def _A = def _C, performs the second drive, eventually focus difference B zone data def _B and any The lens is repeatedly driven and stopped until the difference between the focus difference data in the stop zone at the stop count and the stop threshold falls within the focus threshold value. In order to solve this problem, in the present invention, formula (2) is provided to enable focusing by driving the lens once.

That is, the amount of out-of-focus detected by the focus detection device and its drive amount conversion are as follows: def = def _O + def _A → x = x _O + x _A (3) The out-of-focus amount and the drive amount conversion for focusing by driving the lens are as follows: def ′ = def _O + def _B → x ′ = x _O + x _B (4) Equation (3) to (2) Substituting,

[0040]

[Equation 2] Since x _A << x _max , the final term can be considered to be 0.

Further, since the data of the focus difference is generally in a proportional relation to the moving amount of the focus lens,

[0042]

[Equation 3] In the end, x′≈ (x _O + x _A ) − (x _A −x _B ) = x _O + x _B , which satisfies the formula (4) and achieves the best focus with one lens drive. Is getting

In the present invention, when a lens whose focus position is not divided into a plurality of parts is mounted as the main imaging lens, the data Δdef _ABmax = 0 is stored in the storage part of the main imaging lens. good. Further, as the equation (2), the calculation may be performed after converting it into the number of lens drive pulses instead of calculating the lens drive amount. At this time, the data of the focus difference read from the storage unit may be the lens drive pulse or It may be stored as the lens drive amount.

Then, the data of Δdef _ABmax and x _max is the lens driving amount Δx corresponding to Δdef _{ABmax.
If ABmax} is _stored as Δx _ABmax / x _max as a ratio value, the storage unit can be effectively used and the calculation can be simplified.

In FIG. 1, the lens side control means 2 is provided on the lens side.
However, the control means 21 on the lens side may be removed from the lens side, and the control may be entirely performed on the camera side, or the drive motor 23 may be arranged on the camera side. Further, in this embodiment, the pulse counter is used as the lens position detecting means, but a gray pattern may be provided on the helicoid to read the pattern. Further, the difference between the focus difference at the infinity end and the focus difference at the close end may be calculated.

[0046]

As described above, according to the present invention, even if a lens is divided into a plurality of focus positions and each zone is provided with an eigenvalue for the best focus correction, the focus lens initial stop position is An optical device having a focus detection device that corrects a lens drive amount error corresponding to a difference between a best focus correction eigenvalue of a zone and a best focus correction eigenvalue of a zone at a target focus position to focus by one lens drive Can be achieved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the calculating means in the embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the lens side control means in the embodiment of the present invention.

FIG. 4 is a block diagram of a conventional pupil division type focus detection device.

5 is an explanatory diagram showing spherical aberration of the main imaging lens of the apparatus of FIG.

[Explanation of symbols]

 2 Planned image forming plane 3, 4 split pupils 5 Field lens 6 Secondary image forming lens 7, 8 Light receiving element 10 Focusing lens 11 Image forming lens 12 Film surface 18 Light receiving element 19 Calculation means 21 Lens side control means 22 ROM 23 Drive motor 25 pulse counter

Claims (5)

[Claims] 1. An optical device to which a main imaging lens is attachable / detachable, and optical means for forming a light distribution from light fluxes passing through different parts of a pupil of the main imaging lens, and a light receiving device for receiving the light distribution. Means, computing means for computing the focus position of the main imaging lens based on the positional relationship of the light distribution received by the light receiving means, focus lens position detection means provided in the main imaging lens, focus position computed by the computing means Data relating to the focus difference from the best focus position of the main imaging lens, data relating to the difference between the focus difference at the position corresponding to the infinite distance and the focus difference at the position corresponding to the closest distance, and the total focus movement amount. Storage means for storing data as the unique data of the main imaging lens for each focus position divided into a plurality of parts, and the focus position calculated by the calculation means and the focus position detection hand. A focus provided with a correction means for calculating the movement amount of the focus lens for focusing by performing an arithmetic operation using the unique data read from the storage means based on the signal from the stage. An optical device having a detection device. 2. The optical device having a focus detection device according to claim 1, wherein the unique data is stored as a focus amount. 3. The optical device having the focus detection device according to claim 1, wherein the unique data is stored as a lens driving amount. 4. The focus detection device according to claim 1, wherein the unique data is stored as a pulse number counted by a pulse counter for controlling a focus lens provided in the main imaging lens. Optical device. 5. The data concerning the difference between the focus difference at the infinite distance and the focus difference at the closest distance end and the data concerning the total lens movement amount are stored as a ratio value. Or an optical device having the focus detection device of 4.