JP2003322791A - Focus adjusting device, imaging device, and optical equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the quantity of light reaching an imaging element which picks up the image of a subject decreases when focus detection is carried out by branching luminous flux from a photographic optical system with a half-mirror. <P>SOLUTION: Provided are a wavelength-selective luminous flux separating means 11 which separates a luminous flux component at a wavelength position nearby the infrared range in the visible wavelength range or a luminous flux component outside the specified visible wavelength range from luminous flux from an objective optical system 1, a focus detecting means 12 which can detect the focus adjustment state of the objective optical system by a phase difference detection system, etc., by using the luminous flux component separated by the wavelength-selective luminous flux separating means, and a control means which adjusts the focus of the objective optical system according to the detection result of the focus detecting means. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a film camera,
The present invention relates to a focus adjustment device used for optical devices such as video cameras, digital cameras, and observation devices.

[0002]

2. Description of the Related Art Two types of TTL autofocus devices (focus adjusting devices) for cameras are known. One is generally called a contrast detection method (mountain climbing method or video AF method) and is mainly used as an autofocus device for a video camera.

The other is called a phase difference detection method, and is mainly used as an autofocus device for still cameras. Both types of autofocus devices will be described below.

The contrast detection method is a method in which a part of the photographing optical system is moved in a direction in which a high frequency component included in a video signal increases, or a relative distance between the photographing optical system and an image sensor is changed. When the maximum value of the high frequency component of the signal is obtained, it is determined that the focus is achieved. The autofocus device that uses this contrast detection method
Since the focus is evaluated using the video signal, the image on the image pickup element can be accurately focused on the corresponding subject.

Further, the image on the image pickup device is focused without providing an element dedicated to focus detection, which is advantageous in terms of cost. Therefore, it is mainly used as an autofocus device for video cameras.

The phase difference detection method has an image forming optical system different from the photographing optical system, and detects the shift of the focus (defocus amount) by the pupil division lens and the image pickup device placed at the focal point. Focusing is achieved by moving the photographing optical system so that the defocus amount becomes zero.

However, in the contrast detection method, it takes time to scan the lens from infinity to the closest distance in order to know the in-focus position, and therefore it is not suitable for a system which requires a quick AF operation. Further, since there is little change in the high-frequency component in the portion away from the in-focus position, it is difficult to know whether the focus shift is front focus or rear focus, and the time required for focusing may be extremely long.

Further, when the illuminance is low, the change in the high-frequency component is buried in the noise and the like, and it is difficult to know whether the focus shift is in the front focus or the rear focus. Similarly, the time required for focusing becomes extremely long. Sometimes.

The problem that it takes time to focus as described above leads to a possibility that a momentary shooting opportunity may be missed when news is collected when the autofocus device is used in a TV camera.

In this respect, in the phase difference detection method, focusing can be obtained more quickly than in the contrast detection method. However, the light flux is branched from the image pickup optical system that forms an image on the image pickup element, and it is evaluated whether the image on the image pickup element is in focus by using the image formed at a position different from the image pickup element surface. Therefore, there is a problem that it is difficult to focus accurately.

Therefore, in Japanese Unexamined Patent Publication (Kokai) No. 5-64056, a light flux from a photographing optical system is branched by a half mirror,
Guide the luminous flux to both the contrast detection type autofocus device and the phase difference detection type autofocus device,
An image pickup apparatus has been proposed that selects one of the two pieces of information to perform an AF operation.

That is, first, after the AF operation is performed quickly by the phase difference detection method, but with a certain degree of coarse accuracy, the AF operation is performed with high accuracy by the contrast detection method in the vicinity of the in-focus position, so that the focusing speed is improved. It is compatible with focusing accuracy.

Further, in Japanese Unexamined Patent Publication No. 10-13730, an infrared dichroic mirror divides a light beam into two parts, and an image pickup device for visible light and an image pickup device for infrared light are arranged on respective image forming planes. There has been proposed an image pickup apparatus which is provided with a means for illuminating a subject with infrared light and performs an AF operation by a contrast detection method using one of the image pickup elements.

In other words, when the contrast of visible light is low or the illuminance is low, infrared light is projected onto the subject so that the focusing speed does not decrease and the focusing accuracy does not decrease. The element is performing an AF operation by a contrast detection method.

[0015]

However, the methods proposed in the above publications have the following problems. First, in the method proposed in Japanese Patent Laid-Open No. 5-64056,
Since the light flux from the shooting optical system is branched by the half mirror, the amount of light reaching the image sensor that captures the subject is reduced,
It may not be possible to image a bright subject. Further, particularly, when the illuminance of the subject is low, the amount of light reaching the light receiving element for focus detection is also reduced, and there is a possibility that an accurate AF operation cannot be performed.

Further, in the method proposed in Japanese Patent Laid-Open No. 10-13730, since the two AF devices are both contrast detection methods, focusing accuracy can be obtained, but the problem of slow focusing speed cannot be solved. .

[0017]

A focus adjusting device according to a first aspect of the present invention is a wavelength-selective light beam separating means for separating a light beam component in a wavelength region near the infrared region of a visible wavelength region from a light beam from an objective optical system. And a focus detection means for detecting the focus adjustment state of the objective optical system by using the light flux component separated by the wavelength selective light separation means, and the focus adjustment operation of the objective optical system based on the detection result by the focus detection means. And a control means for performing.

Further, the focus adjusting device of the invention of the second aspect of the present invention is a wavelength-selective light beam separating means for separating a light beam component in a wavelength range outside a predetermined visible wavelength range from a light beam from the objective optical system, and this wavelength selecting means. Phase-difference focus detection means for detecting the focus adjustment state of the objective optical system by the phase-difference detection method using the light-beam components separated by the characteristic light-beam separation means, and the objective based on the detection result by the phase-difference focus detection means. And a control means for performing a focus adjustment operation of the optical system.

According to these aspects of the invention, the luminous flux component near the infrared region of the visible wavelength range or a predetermined visible region is not significantly reduced in the luminous flux from the objective optical system without significantly reducing the light amount of the component in the visible wavelength range necessary for imaging an object. It is possible to perform the focus adjustment operation of the objective optical system using the luminous flux component having a sufficient light amount in the wavelength range outside the wavelength range.

In particular, by selecting the light flux component near the infrared region or the light flux component outside the predetermined visible wavelength range used for detecting the focus adjustment state between 650 nm and 750 nm, the objective optical system The detection error with respect to the focal position of the light flux component in the visible wavelength range, which is the actually used wavelength range, becomes small. When the amount of light in the visible wavelength range is sufficient, the amount of light in the wavelength range between 650 nm and 750 nm is also usually sufficient. Therefore, as compared with the case of using a component in the wavelength range of 750 nm or more (generally referred to as the infrared range), as a result, higher focusing accuracy can be obtained.

In the first and second aspects of the invention, an image pickup device for photoelectrically converting an image formed by a light beam component other than the light beam component separated by the wavelength selective light beam separating means, and an output from this image pickup device A contrast method focus detection means capable of detecting the focus adjustment state of the objective optical system by a contrast detection method using a signal is provided, and the control means is provided with at least one of a contrast method focus detection means and a phase difference method focus detection means. The focus adjustment operation of the objective optical system may be performed based on the detection result.

This enables quick focus adjustment using the phase difference detection method and high-precision focus adjustment using the contrast detection method.

In particular, after the focus adjustment operation of the objective optical system is performed based on the detection result of the phase difference focus detection means, the phase difference focus detection means detects based on the detection result of the contrast focus detection means. By performing the focus adjustment operation with a higher resolution than that based on the result, high-speed and high-precision focus adjustment is possible.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows a schematic configuration of a digital camera (image pickup apparatus) equipped with a focus adjusting device according to a first embodiment of the present invention.

In this figure, reference numeral 1 is a taking lens.
The taking lens 1 is attachable to and detachable from a camera body 13 having the focus adjusting device. The taking lens 1 is composed of a first lens group 2, a variable power lens group 3, a diaphragm 4, a third lens group 5, and a focus adjustment lens group 6.

The focus adjusting lens group 6 adjusts the focus of the taking lens 1 by moving in the optical axis direction by the driving force of the motor 7.

Reference numeral 11 denotes an infrared dichroic mirror fixed in the photographing optical path. Reference numeral 12 denotes a phase difference type focus detection unit for detecting the focus adjustment state of the photographing lens 1 by the phase difference detection method (hereinafter, simply referred to as focus detection). The phase-difference focus detection unit 12 includes a field lens 12a arranged near the image plane, a reflection mirror 12b,
12d, secondary imaging lens 12c, and diaphragm (not shown)
And a pair of line sensors 12e composed of a plurality of CCDs and the like, and performs focus detection of the taking lens 1 by a so-called phase difference detection method.

The infrared dichroic mirror 11 is arranged at an angle of about 45 degrees downward with respect to the optical axis of the taking lens 1, and the phase difference type focus detection unit 12 has a wavelength range near the infrared range in the visible wavelength range ( It guides a luminous flux component in a wavelength range outside a predetermined visible wavelength range).

Here, in general, visible light is approximately 400
nm refers to light in the wavelength range of about 750 nm. Infrared light refers to near infrared from 750 nm to 2.5 μm and 2.5 μm.
The range from m to 50 μm is defined as mid-infrared, and the range of 50 μm or more is defined as far-infrared. The “wavelength range near the infrared range” referred to in the present embodiment means, of the visible wavelength range, a half-value wavelength 65 of an infrared cut filter generally used in an image pickup apparatus.
It means a wavelength range longer than 0 nm and shorter than the infrared wavelength, that is, a wavelength range included between 650 nm and 750 nm.

Reference numeral 14 denotes an infrared cut filter, which is arranged between the infrared dichroic mirror 11 and the image pickup device 8.

Reference numeral 15 is a low-pass filter,
It is arranged between the infrared dichroic mirror 11 and the image sensor 8. Here, the image pickup device 8 that performs photoelectric conversion of a subject image (that is, subject image pickup) is a CCD or a MOS.
It is composed of a solid-state imaging device such as a mold or an imaging tube such as a vidicon. The image sensor 8 is provided with an electronic shutter function and is not equipped with a mechanical shutter mechanism.

Reference numeral 9 denotes an electronic viewfinder for electrically displaying a subject image picked up by the image pickup device 8, which is configured to guide information of the subject image picked up by the image pickup device 8 to the eye 16 of the photographer. There is.

The electronic viewfinder 9 is an RG
LED consisting of B3 color LED light source and liquid crystal panel
The color display may be performed by illuminating in a time series. Further, it may be constituted by a cold cathode tube and a color liquid crystal panel. Alternatively, a color EL (electroluminescence) panel may be used.

Reference numeral 10 denotes an external liquid crystal monitor for displaying a subject image picked up by the image pickup device 8 outside the camera body 13 so that the photographer can confirm the photographed image or change or confirm the camera settings. Is displayed.

In the digital camera constructed as described above, 650n
A light flux component of a required light amount in a wavelength range included between m and 750 nm is reflected by the infrared dichroic mirror 11 and guided to the phase difference focus detection unit 12. A light flux component in the visible wavelength range of 650 nm or less mainly passes through the infrared dichroic mirror 11 and reaches the image sensor 8.

Here, FIG. 2 shows the spectral transmittance distribution of the infrared dichroic mirror 11 when it is incident at 45 degrees. In the infrared dichroic mirror 11, the transmittance half-value (50%) wavelength of the S-polarized component is about 700 nm, and the transmittance half-value wavelength of the P-polarized component is about 730 nm.

In FIG. 3, the infrared dichroic mirror 11 is shown.
3 shows the angle characteristics of the half-value wavelength of the spectral transmittance of the. As shown in this figure, when the incident angle on the infrared dichroic mirror 11 becomes smaller, the half-value wavelengths of both the S-polarized component and the P-polarized component shift to the short wavelength side.

FIG. 4 shows the spectral transmittance of the infrared cut filter 14. The infrared cut filter 14 has a half-value wavelength of 65, which is arranged perpendicular to the optical axis of the taking lens 1.
It is configured with a 0 nm dichroic filter. Although a dichroic filter is used as the infrared cut filter in this embodiment, blue glass that absorbs infrared light may be used.

In the digital camera of the present embodiment configured as described above, the phase difference type focus detection unit 12 is used by using the luminous flux components in the wavelength range between 650 nm and 750 nm reflected and separated by the infrared dichroic mirror 11.
The focus detection is performed, and the focus detection and the subject image pickup are performed by the contrast detection method mainly using the light flux components in the visible wavelength range that reach the image sensor 8.

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. 7A, when the light flux that has passed through the field lens 12a is focused on the planned focal plane S, a part of the light flux is generated by the secondary imaging lenses 12c1 and 12c2 by the line sensor. 12e
The image is again formed on 1, 12e2. Therefore, when the focus is on the planned focal plane, the two line sensors 12e
The two images captured by 1 and 12e2 are formed at substantially coincident positions on the line sensor as shown in FIG. 7B.

On the other hand, as shown by the alternate long and short dash line in FIG. 7A, two line sensors are used in the so-called rear focus state in which the light beam passing through the field lens 12a is focused before the planned focal plane S '. The positions of the two images captured by 12e1 and 12e2 are displaced as shown in FIG. 7C.

Further, in the so-called front focus state in which the light flux passing through the field lens 12a is focused after the planned focal plane, the two images which are picked up by the two line sensors 12e1 and 12e2 are located at the rear positions. Misalignment occurs in the direction opposite to the pin state.

Therefore, the line sensors 12e1 and 12e
The CPU 2 in the camera body 13 to be described later is detected by detecting the displacement direction and displacement amount of the two images captured in e2.
1 (see FIG. 9) can calculate the moving direction and the moving amount of the focus adjustment lens group 6 required for focusing on the planned focal plane.

Then, the CPU 21 sends a command signal to the photographing lens 1 to drive the focus adjustment lens group 6 by the calculated movement amount in the calculated movement direction, and drives the motor 7 to obtain the focus. In this phase difference detection method, the moving direction and the moving amount of the focus adjustment lens group necessary for focusing are directly calculated based on the direction and the amount of deviation between the two images picked up by the two line sensors, so that quick adjustment is possible. You can get the char.

Next, the principle of focus detection by the contrast detection method will be described with reference to FIG. FIG. 8 is a diagram for explaining the relationship between the level of the high frequency component of the image signal obtained by the image sensor 8 and the focus adjustment lens group 6.

In this contrast detection method, the output signal from the image pickup device 8 is converted into an image signal. This image signal can be considered to be formed by combining sine waves having a plurality of frequencies.

As shown in FIG. 8, the level of the high frequency component of the image signal becomes steeper as the sharpness of the image formed on the image sensor 8 increases, that is, as the focusing lens group 6 approaches the focal point A. To rise. Then, generally, when the image on the image sensor 8 is in focus, the level of the high frequency component of the image signal reaches a peak. Further, the peak of this level tends to become steeper as the frequency becomes higher.

On the other hand, the image forming performance of the lens and the S /
The N ratio becomes worse as the frequency becomes higher. Therefore, from the image signal, the imaging performance of the photographing lens 1 and the S /
A focus evaluation value is created by selectively extracting an appropriate high frequency component in consideration of the N ratio and observing the level of this frequency component at an appropriate sampling interval.

For example, when the level of the selected frequency component rises, it is evaluated that the focus adjustment lens group 6 is moving in the direction approaching the in-focus point. Further, when the level of the selected frequency component is lowered, it is evaluated that the focus adjustment lens group 6 is moving in the direction away from the in-focus point.

Then, when the level of the selected frequency component is within a predetermined range (ΔV) from the peak value, it is evaluated that the image on the image sensor 8 is in focus.

The CPU 21 refers to the focus evaluation values successively generated in this way, transmits a command signal to the photographing lens 1 to move the focus adjustment lens group 6 to a position determined to be in focus, and drives the motor 7. Let

In this contrast detection method, since the focus is evaluated using the image signal from the image sensor 8, the image on the image sensor 8 can be accurately focused on the corresponding subject.

The reason why the infrared cut filter 14 is inserted between the infrared dichroic mirror 11 and the image pickup device 8 will be described. The spectral transmittance of the infrared dichroic mirror 11 arranged at an angle of approximately 45 degrees with respect to the optical axis of the taking lens 1 is as shown in FIG. 2, and the half-value wavelength of the S polarization component and the P polarization component is about 26 nm. It will shift.

Since the spectral transmittance characteristics of the infrared cut filter 14 are vertically incident on the axial light flux, the S polarization component,
There is no difference in characteristics between P-polarized components. If the infrared cut filter 14 is not included, the amount of light that is transmitted differs depending on the polarized light, and the low-pass characteristics of the low-pass filter 15 are impaired.

Therefore, the infrared cut filter 14 is inserted between the infrared dichroic mirror 11 and the image pickup device 8,
By cutting light with a wavelength longer than 650 nm,
The light amounts of the S-polarized component and the P-polarized component are made uniform.

Another problem is that the incident angle on the infrared dichroic mirror 11 changes depending on the position of the exit pupil of the taking lens 1 between the on-axis light beam and the off-axis light beam. FIG. 5 shows the case where the exit pupil is at infinity.

In FIG. 5, reference numeral 40 is an axial light flux, 41 is an upper off-axis light flux, and 42 is a lower off-axis light flux. In this case, the incident angle on the infrared dichroic mirror 11 is constant at 45 degrees.

Next, FIG. 6 shows the case where the exit pupil is at a finite distance. In this case, for the on-axis light beam 40, the upper off-axis light beam 4
The incident angle of 1 on the infrared dichroic mirror 11 is smaller than 45 degrees, and the incident angle of the lower off-axis light beam 42 on the infrared dichroic mirror 11 is larger than 45 degrees. Then, the infrared dichroic mirror 1 shown in FIG.
From the angular characteristic of the half-value wavelength of the spectral transmittance of No. 1, it can be seen that the half-value wavelength shifts between the upper off-axis light beam 41 and the lower off-axis light beam 42.

That is, if the infrared cut filter 14 is not provided, the spectral distribution of light reaching the image pickup device 8 is different between the upper side and the lower side, and light amount unevenness and color unevenness occur.

Particularly in a zoom lens, the position of the exit pupil changes due to zooming, and this tendency becomes remarkable.
By inserting the infrared cut filter 14, it is possible to eliminate the difference in the half value wavelength of the spectral transmittance between the upper off-axis light beam 41 and the lower off-axis light beam 42, and to eliminate the uneven light amount and the uneven color.

FIG. 9 shows an electric circuit configuration of the digital camera of this embodiment. In FIG. 9, 1 is a taking lens, and 8 is an image pickup device for picking up a subject image formed by a light flux incident from the taking lens 1.

The CPU 21 in the camera body 13 drives the image pickup device 4 through the timing generator 28 and the driver 29 in conjunction with a shutter button (not shown).
Further, the timing generator 28 controls the analog processing circuit 24 and the A / D conversion circuit 25.

The signal charge (analog image signal) accumulated in the image pickup device 8 is discharged by the driver 29, and the AGC is performed.
Analog signal processing circuit 24 including circuits and CDS circuits
Entered in. The analog image signal subjected to analog processing such as gain control and noise removal by the analog signal processing circuit 24 is converted into a digital signal by the A / D conversion circuit 25.

The digitally converted image signal is, for example, A
The image data is guided to an image processing circuit 26 configured as an SIC, where image preprocessing such as white balance adjustment and gamma correction is performed to obtain image data.

The white balance detection processing circuit includes a white balance sensor 32 which is a color temperature sensor, an A / D conversion circuit 31 which converts an analog signal from the white balance sensor 32 into a digital signal, and a white color based on the digital color temperature signal. CPU 21 for generating a balance correction signal
It consists of and.

The white balance sensor 32 is composed of a plurality of photoelectric conversion elements having sensitivities to red R, blue B, and green G, for example, and extracts partial white, or eliminates the average light of all pixels. The light source color temperature is estimated as coloring. The CPU 21 calculates the R gain and the B gain based on the outputs of the plurality of photoelectric conversion elements. Further, although the white balance sensor 32 is a dedicated sensor, it can also serve as the image pickup element 8.

The image data subjected to the image preprocessing is further subjected to a format process for JPEG compression, and thereafter, the image data is temporarily stored in the buffer memory 33. Finally, the data is compressed in a predetermined ratio by the JPEG method and recorded in a storage medium (PC card) 30 such as a flash memory.

Further, the CPU 21 controls the display driver 34.
Through the electronic viewfinder 9 and the external liquid crystal monitor.

Reference numeral 50 is a contrast-type focus detection circuit for detecting the focus of the taking lens 1 by the above-mentioned contrast detection method.

Next, the operation sequence of the digital camera (mainly the CPU 21) of this embodiment will be described using the flowchart of FIG.

When the shutter button is pressed, the photographing sequence is started and the process proceeds to step S100.

In step S100, the shutter speed and the aperture value are determined so that the amount of light incident on the image pickup device 8 has a desired value, and a command signal is sent to the taking lens 1 so as to narrow the aperture 4.

Next, in step S101, the phase difference type focus detection unit 12 is caused to detect the phase shift amount (defocus amount) of the two images formed on the pair of line sensors 12e. Here, the allowable value of the defocus amount by the phase difference type focus detection unit 12 (that is, the range regarded as the in-focus state, that is, the resolution) is, for example, 35 μm. If the defocus amount exceeds this allowable value, the process proceeds to step S103, and a command signal is sent to the taking lens 1 so that the motor 7 drives the focus adjustment lens group 6 by an amount corresponding to the defocus amount. Step S1
Return to 01. A CPU (not shown) provided in the taking lens 1 drives the motor 7 in response to the command signal.

In step S101, if the defocus amount detected by the phase difference type focus detection unit 12 is equal to or less than the above allowable value, the process proceeds to step S104 to cause the contrast type focus detection circuit 50 to perform focus detection. . Specifically, a high frequency component (contrast value) included in the image signal from the image sensor 8 is extracted, and the increase or decrease is determined by moving the focus adjustment lens group 6 by a very small amount of, for example, 10 μm, and defocusing is performed. Detect direction. In this step, wobbling may be performed in which the focus adjustment lens group 6 is slightly vibrated back and forth.

Then, in step S105, the focus adjustment lens group 6 is moved in the detected defocus direction by a predetermined amount of movement, for example, 5 μm, and focusing is performed when the contrast value peak is detected in step S106. Thus, the final exposure amount determination and focus adjustment are completed.

After focusing, an exposure operation is performed with the aperture value and shutter speed determined in step S100 to take out electric charges from the image sensor 8 and temporarily store them in the memory in the image taking-in storage circuit.

Next, image processing such as matrix processing, white balance processing, and gamma correction processing is performed on the image data captured in the memory of the image capturing storage circuit to compress the data formed as one color image. To do. In the present embodiment, JPEG compression that applies DCT and Huffman coding is performed.

Then, in the next step (not shown), the compressed data is written in the storage medium 30 for storage, and the photographing sequence is finished.

As described above, according to the present embodiment, quick focusing by the phase difference detection method can be performed without significantly reducing the light amount of the component of the visible wavelength range necessary for capturing a bright object in the light flux from the photographing lens 1. The adjusting action can be performed. In addition, after performing the focus adjustment operation with the coarse resolution of the photographing lens 1 by the phase difference detection method, the focus adjustment operation with the fine resolution by the contrast detection method is performed, so that the focus adjustment operation is performed at high speed and with high accuracy. be able to.

(Second Embodiment) FIG. 11 shows a second embodiment of the present invention.
6 is a flowchart showing an operation sequence of the digital camera according to the embodiment. Note that the configuration of the digital camera of this embodiment is the same as that of the first embodiment, and common components are assigned the same reference numerals as in the first embodiment.

In this embodiment, the error between the focus state (focus position) detected by the phase difference focus detection unit 12 and the focus position detected by the contrast detection system is stored as the best focus correction value (BP value). However, the focus position detected by the phase difference type focus detection unit 12 is configured to be corrected by the BP value.

Further, in this embodiment, in order to correct the focus position detected by the phase difference type focus detection unit 12, the BP value obtained by the previous error detection or the average value of the past several BP values is used. It is configured to remember. This is because when the taking lens 1 is replaced with another type of taking lens having different optical characteristics, the BP value changes, and even for lenses of the same type, the BP value changes due to variations in individual characteristics.

When a shutter button (not shown) is pressed, the photographing sequence is started and the process proceeds to step S200.

In step S200, the shutter speed and the aperture value are determined so that the amount of light incident on the image pickup device 8 becomes a desired value, and a command signal is sent to the taking lens 1 so that the aperture 4 is narrowed down.

Next, in step S201, the phase difference type focus detection unit 12 is caused to detect the defocus amount. At this time, the defocus amount is corrected by the BP value.

For example, when the BP value is -50 μm and the defocus detection amount is 200 μm, the corrected defocus amount is 150 μm.

The allowable value of the defocus amount by the phase difference type focus detection unit 12 (that is, the range regarded as the in-focus state, that is, the resolution) is, for example, 35 μm. Then, if the defocus amount exceeds this allowable value, the process proceeds to step S203, and the focus adjustment lens group 6 is driven by the motor 7 by an amount corresponding to the defocus amount.
A command signal is sent to the taking lens 1, and the process returns to step S201.

In step S201, if the defocus amount corrected by the phase difference focus detection unit 12 and corrected by the BP value is less than or equal to the above allowable value, the process proceeds to step S204, and the contrast focus detection circuit 50.
Let focus be detected. Specifically, a high frequency component (contrast value) included in the image signal from the image sensor 8 is extracted, and the increase or decrease is determined by moving the focus adjustment lens group 6 by a very small amount of, for example, 10 μm, and defocusing is performed. Detect direction. In this step, wobbling may be performed in which the focus adjustment lens group 6 is slightly vibrated back and forth.

Then, in step 205, the focus adjustment lens group 6 is moved by a predetermined amount in the detected defocus direction,
For example, a command signal is transmitted to the taking lens 1 so as to move by 5 μm, and focusing is performed when the contrast value peak is detected in step S206. Thus, the final exposure amount determination and focus adjustment are completed.

Next, in step S207, the deviation between the defocus value detected by the phase difference focus detection unit 12 in step S201 and the defocus value detected by the contrast detection method in step S204 is calculated, and a new value is calculated. It is stored as a BP value.

After focusing, an exposure operation is performed at the aperture value and shutter speed determined in step S200 to take out electric charges from the image sensor 8 and temporarily store them in the memory in the image taking-in storage circuit.

Next, image processing such as matrix processing, white balance processing and gamma correction processing is performed on the image data captured in the memory of the image capturing storage circuit to compress the data formed as one color image. To do. In the present embodiment, JPEG compression that applies DCT and Huffman coding is performed.

Then, in the next step (not shown), the compressed data is written in the storage medium 30 for storage, and the photographing sequence is ended.

By correcting the BP value as in this embodiment, it is possible to improve the detection accuracy of the phase difference type focus detection unit 12 and minimize the focusing process by the contrast detection method. . Therefore, as compared with the first embodiment, it is possible to further improve the focusing speed and the focusing accuracy.

In each of the above embodiments, the interchangeable lens type digital camera has been described. However, the present invention can be applied to a lens integrated type digital camera, and also to an observation device such as a video camera or binoculars. Can be applied.

[0096]

As described above, according to the present invention,
Of the luminous flux from the objective optical system, the luminous flux component near the infrared region of the visible wavelength range or the wavelength range outside the predetermined visible wavelength range is sufficiently reduced without significantly reducing the light amount of the visible wavelength range component necessary for imaging the subject. It is possible to perform the focus adjustment operation of the objective optical system using the luminous flux components of various light amounts. Therefore, it is possible to capture a bright subject image and the like, and it is possible to prevent the accuracy of focus adjustment from being lowered under low illuminance.

Further, after the focus adjustment operation of the objective optical system is performed based on the detection result of the phase difference type focus detection means, the detection by the phase difference type focus detection means is performed based on the detection result of the contrast type focus detection means. If the focus adjustment operation is performed with a resolution higher than that based on the result, the focus adjustment can be performed at high speed and with high accuracy.

[Brief description of drawings]

FIG. 1 is a sectional view of a digital camera that is a first embodiment of the present invention.

FIG. 2 is a graph showing a spectral transmittance of an infrared dichroic mirror used in the digital camera of the first embodiment.

FIG. 3 is a graph showing half-value angle characteristics of the infrared dichroic mirror.

FIG. 4 is a graph showing the spectral transmittance of the infrared cut filter used in the digital camera of the first embodiment.

FIG. 5 is a diagram illustrating an incident angle to an infrared cut filter when the exit pupil of the digital camera of the first embodiment is infinity.

FIG. 6 is a diagram illustrating an incident angle to the infrared cut filter when the exit pupil of the digital camera of the first embodiment is finite. Description of the first embodiment, when the exit pupil has a distance

FIG. 7 is an explanatory diagram of the principle of the phase difference detection method.

FIG. 8 is an explanatory diagram of the principle of a contrast detection method.

FIG. 9 is a block diagram showing an electric circuit configuration of the digital camera of the first embodiment.

FIG. 10 is a flowchart showing an operation sequence of the digital camera of the first embodiment.

FIG. 11 is a flowchart showing an operation sequence of the digital camera which is the second embodiment of the present invention.

[Explanation of symbols]

1 Shooting lens 2 First lens group 3 zoom lens groups 4 aperture 5 Third lens group 6 Focus adjustment lens group 7 motor 8 image sensor 9 Electronic viewfinder 10 External LCD monitor 11 Infrared dichroic mirror 12 Phase difference type focus detection unit 13 camera body 14 infrared cut filter 15 Low-pass filter 16 Photographer's eyes 19 lens ROM 20 Infrared cut filter, low-pass filter 21 CPU 40 On-axis light flux 41 Upper off-axis light flux 42 Lower off-axis light flux 50 Contrast type focus detection circuit

Front page continuation (51) Int.Cl. ⁷ identification code FI theme code (reference) G02B 7/36 G02B 7/11 C G03B 13/36 D H04N 5/232 G03B 3/00 A F term (reference) 2H011 BA23 BA31 BB01 DA00 2H044 DA01 DC02 2H048 FA09 FA12 FA22 2H051 AA01 BA04 BA45 DA02 DA35 DA36 DA39 5C022 AA07 AA13 AB29 AB43 AC42 AC54 AC55 AC69 AC74

Claims (12)

[Claims] 1. A wavelength-selective light beam separating means for separating a light-beam component from a light beam from an objective optical system into a light-wave component in a wavelength region near the infrared region of a visible wavelength region, and a light-beam component separated by the wavelength-selective light beam separating device. And focus control means for detecting the focus adjustment state of the objective optical system by using, and control means for performing the focus adjustment operation of the objective optical system based on the detection result by the focus detection means. Focus adjustment device. 2. The wavelength region near the infrared region is 650 nm
The focusing device according to claim 1, wherein the focusing device is included in the range from 1 to 750 nm. 3. A wavelength-selective light beam separating means for separating a light beam component in a wavelength range outside a predetermined visible wavelength range from a light beam from an objective optical system, and a light beam component separated by the wavelength-selective light beam separating means. Phase difference type focus detecting means for detecting the focus adjustment state of the objective optical system by the phase difference detecting method, and control means for performing the focus adjusting operation of the objective optical system based on the detection result by the phase difference type focus detecting means. And a focus adjusting device. 4. The wavelength range outside the predetermined visible wavelength range is 6
The focus adjusting device according to claim 3, wherein the focus adjusting device is included between 50 nm and 750 nm. 5. An image pickup device for photoelectrically converting an image formed by the light beam components separated by the wavelength selective light beam splitting means, and an output signal from the image pickup device is used to perform a contrast detection method of the objective optical system. A contrast-type focus detection unit capable of detecting a focus adjustment state; and the control unit, based on the detection result of at least one of the phase-difference-type focus detection unit and the contrast-type focus detection unit. The focus adjusting device according to claim 1, wherein the focus adjusting operation is performed. 6. The control means performs a focus adjustment operation of the objective optical system based on the detection result of the phase difference focus detection means, and then based on the detection result of the contrast focus detection means. The focus adjusting apparatus according to claim 5, wherein the focus adjusting operation is performed with a higher resolution than that based on the detection result of the phase difference type focus detecting means. 7. The focus of the objective optical system based on the detection result of the phase difference type focus detection means when the detection result of the phase difference type focus detection means is larger than a predetermined defocus amount. After performing the adjustment operation, the focus adjustment operation is performed based on the detection result by the contrast method focus detection means, and when the detection result by the phase difference method focus detection means is the predetermined defocus amount or less, The focus adjusting apparatus according to claim 5, wherein the focus adjusting operation of the objective optical system is performed based on the detection result of the contrast type focus detecting means. 8. The control means compares the detection result of the phase difference type focus detection means with the detection result of the contrast type focus detection means, and based on these differences, the phase difference type focus detection means. The focus adjustment device according to claim 5, wherein the detection result is corrected. 9. The focus adjusting device according to claim 1, wherein the wavelength-selective light beam splitting means is configured to have a dichroic surface. 10. A focus adjusting device according to claim 1, wherein the focus adjusting device performs a focus adjusting operation of a photographing optical system as the objective optical system, and the wavelength selective light beam separation. An image pickup device for picking up an image of a subject using a light flux component other than the light flux component separated by the means. 11. The image pickup apparatus according to claim 10, wherein an infrared cut filter is arranged between the wavelength selective light beam splitting means and the image pickup element. 12. An optical apparatus comprising the focus adjusting device according to claim 1. Description: