JPH11287946A - Focus adjusting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus adjusting device for a multi-plate type electronic camera which shortens a focusing time in contrast type automatic focusing without spoiling high picture quality. SOLUTION: At the time of focusing position detection, a parallel plate 22 is put in the luminous flux between the projection surface 4b of a prism 4 and a 2nd image pickup element 8. The integral value of the contrast when a focus lens is at each position in the optical axis is found by using the electric signal of a 1st image pickup element 5 and the electric signal of the 2nd image pickup element 8 corresponding to the luminous flux whose the optical path length is extended by putting the parallel plate 22 in and the focusing position is detected from the relation between the focus lens position and the contrast integral value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus adjusting device for an electronic camera, and more particularly to a focus adjusting device suitable for a multi-plate type electronic camera having a plurality of image pickup devices.

[0002]

2. Description of the Related Art Auto focus of an electronic camera (hereinafter referred to as A)
F) generally employs a so-called contrast method in which the detection of a high-frequency component of the contrast of a signal of an image pickup element for image capturing is performed. This contrast AF method does not require a distance measuring optical system separate from the photographing optical system as compared with a distance measuring AF method in which a distance to a subject is measured and a focus lens in the photographing lens system is moved according to the distance. So-called TT
Since it is an L (through the lens) AF, it is excellent in that the structure of the optical system can be simplified, parallax need not be considered, and the like.

On the other hand, since the image quality, particularly the resolution, of an electronic camera is governed by the number of pixels of the image sensor, a so-called multi-chip type image pickup system combining a plurality of image sensors is widely known in order to improve the resolution. ing. The multi-plate imaging system includes a prism optical system arranged at a rear portion of a photographing lens system to divide a light beam into a plurality of light beams, and an imaging element arranged at each emission surface of the prism optical system. Is done. Then, in the electronic camera having the multi-chip imaging system, an electric signal that has been photoelectrically converted by each imaging element is processed by an imaging processing circuit for each imaging element and then combined to create one image. Also in this multi-plate electronic camera, the AF is generally of the same contrast type as described above. For example, Japanese Patent Application Laid-Open No. H10-4517 discloses a method of detecting a focus position by a hill-climbing method using an image signal extracted from an arbitrary CCD in a three-chip image sensor (hereinafter, CCD) camera.

[0004] Also, Japanese Patent Application Laid-Open No. 5-64209 discloses that
Two CCDs are separately used for luminance and chroma, and the relative positions in the direction of the optical axis are shifted from each other. Defocus is detected from two signals having different optical path lengths.
A method of focusing only on a CD has been proposed.

[0005]

However, in a multi-panel electronic camera, for example, a general contrast type AF as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 10-4517 is disclosed.
Since the operation of comparing the captured images while moving the focus lens to calculate the in-focus position is repeated, it takes more time than the distance measurement method. Therefore, at the time of photographing, usually, a release button is pressed to perform an AF operation first, and A
After the completion of F, the actual photographing operation is performed by performing automatic exposure (AE) or the like. Therefore, if the AF operation takes a long time, there is a possibility that appropriate photographing cannot be performed with a moving subject.

On the other hand, in the technique described in the above-mentioned Japanese Patent Application Laid-Open No. 5-64209, two CCDs are arranged so that their focus positions are shifted from each other, and CCs at these different focus positions are arranged.
Since AF is performed by discriminating the front focus and the rear focus by comparing the signals obtained from D, one of the two CCDs is photographed with the out-of-focus state. The benefits of conversion are lost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a focus adjusting device for a multi-plate type electronic camera which shortens a focusing time in a contrast type autofocus and does not impair high image quality. The purpose is to provide.

[0008]

In order to solve the above problems, a focus adjusting apparatus according to a first aspect of the present invention passes through a focus lens for forming a subject image on an image pickup device and a photographing lens system including the focus lens. A beam splitter that divides a light beam into a plurality of light beams, a plurality of image sensors arranged to face each of the light beam emitting surfaces of the beam splitter, and at least one between the light beam emitting surface and the image sensor facing each other. An optical member arranged to change the optical path length between the focus lens and the imaging element; and an optical member moving unit that allows at least one of the optical members to advance and retreat to a light beam;
The in-focus position of the focus lens is calculated by processing an image signal of the image sensor corresponding to the light beam whose optical path length has been changed by entering or retracting at least one light beam of the optical member and an image signal of another image sensor. And a focus control means for moving the focus lens to the in-focus position.

Further, the focus adjusting device according to the second aspect of the present invention
In the focus adjusting device according to the first aspect, the optical member moving means enters the light beam of the optical member,
The optical path length from the imaging element into which the optical member has entered to the focus lens is different from the optical path length from the imaging element to which the optical member has not entered into the focus lens.

[0010] The focus adjusting device according to a third aspect of the present invention includes:
In the focus adjusting apparatus according to the second aspect, an optical member is disposed between the image pickup device and an exit surface of another light beam except at least one between the exit surface of the light beam and the image pickup device facing each other. The optical path lengths to be changed by the optical members are set to be different from each other, and these optical members can be moved forward and backward by the optical member moving means.

[0011] The focus adjusting device according to a fourth aspect of the present invention includes:
In the focus adjusting device according to the first aspect of the present invention, the optical member moving means retracts the optical member from the light beam, so that the optical path length from the image pickup device to which the optical member is retracted to the focus lens is retracted. The optical path length from the image pickup element to the focus lens is different from the optical path length.

Further, the focus adjusting device according to a fifth aspect of the present invention comprises:
In the focus adjusting apparatus according to the fourth aspect, an optical member for equally changing the optical path length between the focus lens and the image sensor is disposed between the light emitting surface of the light beam and the image sensor opposite to each other. The optical member other than at least one of the optical members can be moved forward and backward by the optical member moving means.

[0013] The focus adjusting device according to a sixth aspect of the present invention includes:
In the focus adjusting apparatus according to the fourth or fifth aspect, the optical member is a low-pass filter.

[0014] The focus adjusting apparatus according to a seventh aspect of the present invention includes:
In the focus adjusting apparatus according to the fourth or fifth aspect, the optical member is an infrared cut filter.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 8 relate to a first embodiment of the present invention. FIG. 1 is a block diagram mainly showing an electric configuration of an electronic camera, and FIG. 2 is an optical path length between a focus lens and an imaging surface by inserting a parallel plate. Explanatory diagram showing the change of
FIG. 3 is an explanatory diagram showing an optical path length, FIG. 4 is a general characteristic diagram of a focus lens optical axis direction position and a contrast integrated value,
FIG. 5 is a characteristic diagram of the position of the focus lens in the optical axis direction and the contrast integrated value obtained by the first image sensor.
FIG. 7 is a characteristic diagram of the position corresponding to the optical axis direction of the focus lens obtained by the second image sensor and the contrast integrated value.
5 is a composite diagram of FIGS. 5 and 6, and FIG. 8 is a characteristic diagram of the position of the focus lens in the optical axis direction and the contrast integrated value.

The electronic camera shown in FIG. 1 has a photographic lens system 1 having a focus lens 1a for forming a subject image on an image sensor, and a low-pass for restricting passage of a high-frequency component of a light beam passing through the photographic lens system 1. A filter 2, an infrared cut filter 3 for restricting passage of an infrared component of a light beam passing through the photographing lens system 1, and a light beam passing through the photographing optical system 1, the low-pass filter 2, and the infrared cut filter 3 different from each other 2 A prism 4 serving as a beam splitter that splits the light into component light beams, and a subject image formed by the photographing lens system 1 disposed opposite to one of the emission surfaces 4a of the light beams split by the prism 4 to be photoelectrically converted. A first imaging element 5 for outputting an electric signal as an electrical signal, an imaging circuit 6 for performing predetermined image processing or the like on the output of the first imaging element 5, An A / D conversion circuit 7 for converting the output of the circuit 6 into a digital signal; and a subject image formed by the photographic lens system 1 and arranged opposite to the exit surface 4b of the other light beam split by the prism 4 A second imaging element 8 that photoelectrically converts the
An image pickup circuit 9 for performing predetermined image processing or the like on the output of the image pickup device 8, an A / D conversion circuit 10 for converting the output of the image pickup circuit 9 into a digital signal, and an output of the A / D conversion circuits 7, 10 , A memory 12 for storing the output of the image synthesis processing circuit 11, and the memory 12 in response to the operation of a release switch (not shown).
A compression / expansion circuit 13 for compressing digital image data stored in a memory card 14 and expanding the image data when reading out the compressed image data from a memory card 14 described later. A memory card 14 configured to store compressed image data.

Here, the first and second image pickup devices 5, 8
Is the optical path length from the focus lens 1a to the imaging surface 5a of the first image sensor 5 and the second image sensor 8
Are arranged so that the optical path lengths up to the imaging surface 8a are equal to each other.

The electronic camera further includes a detection circuit 15 for extracting high-frequency components at respective inputs from the A / D conversion circuits 7 and 10 so as to perform focusing control by a so-called hill-climbing auto-focusing method. The detection circuit 15 corresponding to the electric signals obtained by the elements 5 and 8
An integration circuit 16 that digitally integrates the inputs from each other to obtain an integrated value of the contrast, calculates a focus position of the focus lens 1a based on the input from the integration circuit 16, and moves the focus lens 1a to the focus position. A system controller 17 having a function as focusing control means for performing movement control, and a parallel as an optical member which is disposed between the emission surface 4b of the prism 4 and the second imaging element 8 and changes the optical path length. A plate 22.

Here, the system controller 17
Is for performing overall control of the electronic camera, and drives a focus motor 19 via a focus motor drive circuit 18 to drive the focus lens 1.
a in the optical axis direction, and the drive circuit 20
And a function of driving a drive circuit 20 as an optical member moving means via the control member to control the forward / backward movement of the parallel plate 22 with respect to the light beam.

The parallel plate 22 is made of, for example, a glass plate, and is set so as to extend the optical path length by e when entering the light beam. That is, the parallel plate 22 enters into the light beam between the focus lens 1a and the image pickup device 8, and thereby the optical path length L between the focus lens 1a and the image pickup surface 8a of the image pickup device 8 (see FIG. 2).
(FIG. 2A) is extended to L + e (see FIG. 2B) without moving the focus lens 1a.
The optical path length e extended by the parallel plate 22 is determined by the refractive index n of the glass plate constituting the parallel plate 22 and the thickness d in the optical axis direction of the glass plate. = D (1- (1 / n)).

In general, in the hill-climbing auto focusing system, the focus lens is moved from an infinite position to a close position, and as shown in FIG. 4, the integrated value of the contrast at each position of the focus lens in the optical axis direction is obtained. (Eg, an integrated value of contrast for each optical path length changed at the same pitch 1), and a focus position is obtained from the relationship between the position of the focus lens in the optical axis direction and the integrated value of contrast. In this method, the position where the integrated value of the contrast is maximum is regarded as the focus position of the focus lens.

The focus control of the hill-climbing auto-focusing system by the focus adjusting device of the electronic camera according to the present embodiment will be described below. Here, the focus adjustment device moves the focus lens 1a from the infinity position to the closest position side on the optical axis, and the position of the focus lens 1a in the optical axis direction is set to an integral value of the contrast for every equal pitch e, for example, 10 points. The focus position is obtained by sampling.
The optical path length e extended by the parallel plate 22 is set to be の of the moving pitch of the focus lens 1a at the time of detecting a focus position described later.

When a release switch (not shown) is operated to start focusing control, the system controller 1
7 first drives the focus motor 19 via the focus motor drive circuit 18 to set the focus lens 1a
At the infinite position (the position indicated by (a1) in FIG. 3).

Next, the system controller 17
The motor 21 is driven via the drive circuit 20, and the parallel plate 22 is made to enter the light beam between the emission surface 4 b of the prism 4 and the imaging device 8. Then, the optical path length between the focus lens 1a and the imaging surface 8a of the second imaging device 8 is extended by e compared to the optical path length between the focus lens 1a and the imaging surface 5a of the first imaging device 5.

That is, when the parallel plate 22 enters, the second
As shown in FIG. 3B, the subject image formed on the image pickup device 8 is formed at a position where the focus lens 1a is moved closer to the optical axis position than the actually existing position by e. It becomes equivalent to the subject image.

Therefore, in this case, the first image sensor 5
As a result, an electric signal of the subject image at the infinite position (a1) of the focus lens 1a is obtained, and the position of the focus lens 1a in the optical axis direction at which the focus lens 1a moves from the infinity position to the closest side by e is obtained by the second image pickup device 8. An electric signal equivalent to the electric signal of the subject image in (b1) is obtained.

The electric signal obtained by the first image pickup device 5 is processed by the image pickup circuit 6, the A / D conversion circuit 7, the detection circuit 15, and the integration circuit 16, and the focus lens 1a is moved to the infinity position ( a1) is input to the system controller 17 as an integrated value of the contrast, and
The electric signal obtained by the second image sensor 8 is similarly
After processing by the imaging circuit 9, the A / D conversion circuit 10, the detection circuit 15, and the integration circuit 16, the focus lens 1a is moved from the infinity position to the close side by the distance e in the optical axis direction (b1
) Is input to the system controller 17 as the integrated value of the contrast.

Next, the system controller 17
The focus motor 19 is driven via the focus motor drive circuit 18 to move the focus lens 1a from the infinity position by 2e to the closest optical axis position (a2). Then, the system controller 17 obtains the integrated value of the contrast at the position (a2) on the optical axis of the focus lens 1a based on the electric signal of the subject image obtained by the first image sensor 5 and the second value. Image sensor 8
Based on the electric signal of the subject image obtained in step (1), the integrated value of the contrast at the optical axis direction position (b2) at which the focus lens 1a has moved from the optical axis direction position (a2) to the closest side by e is obtained.

Hereinafter, in the same procedure, the system controller 17 moves the focus lens 1a to
e at a pitch of each e.
An integrated value of the contrast based on the electric signals obtained by the second imaging elements 5 and 8 is obtained.

The integrated value of the contrast at each optical axis direction position of the focus lens 1a obtained in this manner is, as shown in FIGS.
Stored in And the system controller 1
In step 7, the integrated values of the contrasts are combined to obtain the relationship between the position of the focus lens 1a in the optical axis direction and the integrated value of the contrast for each equal pitch e (see FIG. 7).

Next, based on the relationship between the obtained position of the focus lens 1a in the optical axis direction and the integrated value of contrast, the system controller 17 determines the position of the focus lens 1a in the optical axis direction at which the integrated value of the contrast becomes maximum. And determine the in-focus position.

Next, the system controller 17 drives the focus motor 19 via the focus motor drive circuit 18 to move the focus lens 1a to the focus position and drives the motor 21 via the drive circuit 20. Then, the parallel plate 22 is connected to the exit surface 4 of the prism 4.
The light is retracted from the light beam between b and the second image sensor 8.

In the electronic camera, after the above-described focusing control is performed, an image is captured in response to the operation of a release switch (not shown).

As described above, according to the present embodiment, the parallel plate 22 enters the light beam between the exit surface 4b of the prism 4 and the second image pickup device 8 to change the optical path length when the focus position is detected. By doing so, each time the focus lens 1a is moved once, an integrated value of contrast in two different optical path lengths can be obtained, so that the in-focus position can be detected in a short time even with a contrast-type electronic camera. be able to. That is, the focus adjusting device of the electronic camera can effectively use the imaging devices 5 and 8 at the time of detecting the in-focus position, and can simultaneously obtain the integrated values of the contrast at the two types of focus lens optical axis positions.

The focus adjusting device of this electronic camera is:
The optical path length e to be changed by the parallel plate 22 is set to １ ／ of the moving pitch of the focus lens 1a when the focus position is detected.
, The first and second imaging elements 5 and 5
When data based on the electric signal obtained in step 8 is synthesized,
The position of the focus lens 1a in the direction of the optical axis in the composite data can be set as the movement position for every equal pitch e, and the focus position can be detected more effectively.

Further, at the time of photographing, by retracting the parallel plate 22 from the light beam, the optical path lengths of the focus lens 1a and the image pickup devices 5 and 8 can be made equal, thereby deteriorating the advantages of the multi-plate type image pickup system. There is no.

In the above-mentioned focus adjusting device, an example has been described in which the optical path length of the light beam extended by the parallel plate 22 is set to 1/2 of the moving pitch of the focus lens 1a at the time of detecting the in-focus position. For example, the optical path length of the light beam extended by the parallel plate 22 can be set to half the distance from the infinity position to the close position of the focus lens 1a. In such a case, at the time of detecting the in-focus position, the focus lens 1a is moved from the infinity position to an intermediate point between the infinity position and the closest position at a preset equal pitch.

Then, as shown in FIG. 8, based on the electric signal obtained by the first image pickup device 5, the system controller 17 moves the focus lens from the infinite position to the intermediate point between the infinite position and the closest position. In addition to obtaining the integral value of the contrast ((a1 to a4) in FIG. 8) for each equal pitch movement position of 1a, the intermediate point between the infinite position and the closest position based on the electric signal obtained by the second image sensor 8 , The integrated value of the contrast ((b1 to b4) in FIG. 8) at each equal pitch movement position of the focus lens 1a from the position to the closest position.

By setting the length of the optical path lengthened by the parallel plate 22 to be large as described above, the moving distance of the focus lens 1a at the time of detecting the in-focus position can be reduced to approximately half, and the in-focus position can be more efficiently obtained. Detection can be performed.

Further, the focus adjusting device according to the present embodiment can be applied to an electronic camera having three or more imaging devices. In this case, at the time of detecting the in-focus position, the emission of other light beams except at least one between the emission surface of each light beam of the beam splitter (prism) and the imaging device disposed to face the emission surface of this light beam, respectively. By injecting optical members (parallel plates) having different optical path lengths to be respectively extended into the light flux between the surface and the image pickup device, it is possible to obtain an integrated value of contrast in three or more types of plural optical path lengths at a time. it can. Therefore, the in-focus position can be detected in a shorter time than in the focus adjustment device applied to the above-described two-panel electronic camera. Of course, even in such a case, when the imaging is performed after the in-focus position detection is completed, the optical path length between the focus lens and each image sensor is made equal by retracting each optical member from each light beam. Thus, a high-quality image can be obtained without impairing the advantages of the multi-plate imaging system.

Here, when the focus position is detected by changing the optical path length by a plurality of optical members as described above, the optical path length by which one optical member changes the optical path length changed by each optical member. By making the pitch of the focus lens in the optical axis direction at the time of detecting the in-focus position an integral multiple of the optical path length changed by the first optical member,
An integrated value of contrast at each focus lens position can be obtained effectively.

Next, FIG. 9 relates to a second embodiment of the present invention, and FIG. 9 is a block diagram showing a main part of a focus adjusting device. In the present embodiment, as shown in FIG.
Instead of the parallel plate 22 as the optical member employed in the embodiment, a low-pass filter for limiting a high-frequency component of a light beam is also used as the optical member. The other configuration is substantially the same as that of the above-described first embodiment, and a description thereof will not be repeated.

In the focus adjusting device according to the present embodiment, each of the emission surfaces 4a and 4b of the prism 4 as a beam splitter for splitting the light beam passing through the photographing lens system 1 and the infrared cut filter 3 into two different component light beams, and Exit surface 4
a, 4b, image sensors 5, 8 disposed opposite to each other
And first and second low-pass filters 2a and 2b, respectively.

The first and second low-pass filters 2
a and 2b change the optical path length equally,
It is set so that when it enters the light beam, the optical path length is extended by e.

The first low-pass filter 2 a is fixed in the light beam between the light exit surface 4 a of the prism 4 and the first image pickup device 5.

On the other hand, the second low-pass filter 2b
Is disposed between the emission surface 4b of the prism 4 and the second image pickup device 8, and is movable forward and backward with respect to the light beam by a motor (not shown) as an optical member moving means.

When performing focusing in this focus adjusting device, first, the second low-pass filter 2b is used.
Is retracted from the light beam between the exit surface 4b of the prism 4 and the second image pickup device 8, thereby reducing the optical path length of this light beam by e.

Next, by performing substantially the same processing as in the first embodiment, the relationship between the position in the optical axis direction and the integrated value of the contrast when the focus lens 1a is moved for each distance e is obtained.

Next, the obtained focus lens 1a
From the relationship between the position in the optical axis direction and the integrated value of the contrast, the focus lens 1 having the maximum integrated value of the contrast
The position in the optical axis direction of “a” is obtained, and the focus position is determined.

Next, the focus lens 1a is moved to the in-focus position and the second low-pass filter
b into the light beam between the exit surface 4b of the prism 4 and the second image sensor 8, and the optical path length of the first image sensor 5 and the optical path of the second image sensor 8 with respect to the focus lens 1a. Match with the long.

According to such an embodiment, the following effects can be obtained in addition to the effects obtained in the first embodiment.

Since the second low-pass filter 2b also serves as an optical member for changing the optical path length of the light beam, it is not necessary to newly provide an optical member such as a parallel plate.

Further, since the second low-pass filter 2b is retracted from the light beam at the time of detecting the in-focus position, the resolution of the second image pickup device 8 is increased and the detection sensitivity is improved.

In the present embodiment, an example is shown in which the low-pass filter is also used as an optical member for changing the optical path length of a light beam. However, for example, an infrared cut filter may be used as the above-mentioned optical member.

Further, the focus adjusting device of the present embodiment
The present invention can be applied not only to a plate-type electronic camera but also to three or more plate-type electronic cameras.

For example, when this focus adjusting device is applied to a three-plate type electronic camera, each of the exit surfaces of a prism serving as a beam splitter for dividing a light beam passing through a photographing lens system into light beams of three different components, and each of the exit surfaces A low-pass filter and an infrared cut filter are arranged between the image sensors arranged opposite to each other. One of the low-pass filters and the infrared cut filter is fixed in the light beam, the other low-pass filter or the infrared cut filter is allowed to advance and retreat with respect to the light beam, and the remaining low-pass filter and the infrared cut filter are converted into the light beam. On the other hand, by making it possible to move forward and backward, integral values of contrast in three different optical path lengths can be obtained at the same time.

[0057]

As described above, according to the present invention,
It is possible to provide a focus adjusting device of a multi-panel electronic camera that shortens a focusing time in contrast type autofocus and does not impair high image quality.

[Brief description of the drawings]

FIGS. 1 to 8 relate to a first embodiment of the present invention, and FIG. 1 is a block diagram mainly showing an electric configuration of an electronic camera;

FIG. 2 is an explanatory diagram showing a change in an optical path length between a focus lens and an imaging surface due to insertion of a parallel plate;

FIG. 3 is an explanatory diagram showing an optical path length;

FIG. 4 is a general characteristic diagram of a focus lens optical axis direction position and a contrast integrated value,

FIG. 5 is a characteristic diagram of a focus lens optical axis direction position and a contrast integrated value obtained by a first image sensor,

FIG. 6 is a characteristic diagram of a position corresponding to a focus lens optical axis direction obtained by a second image sensor and a contrast integrated value;

FIG. 7 is a composite diagram of FIGS. 5 and 6,

FIG. 8 is a characteristic diagram of a position of a focus lens in an optical axis direction and a contrast integrated value,

FIG. 9 is a block diagram showing a main part of a focus adjustment device according to a second embodiment of the present invention;

[Explanation of symbols]

Reference Signs List 1 photographic lens system 1a focus lens 2 low-pass filter (optical member) 3 infrared cut filter (optical member) 4 prism (beam splitter) 4a output surface 4b output surface 5 first image sensor (imaging) 8) Second imaging element (imaging element) 17 ... System controller (focusing control means) 21 ... Motor (optical member moving means) 22 ... Parallel plate (optical member)

Claims (7)

[Claims] A focus lens that forms a subject image on an image sensor; a beam splitter that divides a light beam that has passed through a photographing lens system including the focus lens into a plurality of light beams; and a light exit surface of each light beam of the beam splitter. A plurality of image sensors arranged to face each other; an optical member arranged at least at one between the light-emitting surface of the opposing light beam and the image sensor to change the optical path length between the focus lens and the image sensor; An optical member moving means for allowing at least one of the members to freely advance and retreat to a light beam; an image signal of an image sensor corresponding to the light beam whose optical path length has been changed by entering or retreating the at least one light member of the optical member, and another image pickup The focus position of the focus lens is calculated by calculating the image signal of the element, and the focus lens is moved to the focus position. Focusing apparatus characterized by comprising: a focus control means. 2. The optical member moving means enters the light beam of the optical member, and the optical path length from the image pickup element into which the optical member has entered to the focus lens changes from the image pickup element into which the optical member has not entered into the focus lens. The focus adjusting device according to claim 1, wherein the focus adjusting device is configured to be different from the optical path length up to. 3. An optical member is disposed between an image pickup device and an exit surface of another light beam excluding at least one between the light exit surface of the light beam and the image pickup device facing each other, and an optical path changed by these optical members. 3. The focus adjusting device according to claim 2, wherein the lengths are set to be different from each other, and these optical members can be moved forward and backward by the optical member moving means. 4. An optical member moving means for retreating an optical member from a light beam causes an optical path length from the retracted image pickup element of the optical member to the focus lens to be changed from an image pickup element of the optical member not retracted to the focus lens. The focus adjusting device according to claim 1, wherein the focus adjusting device is configured to be different from the optical path length up to. 5. An optical member for equally changing the optical path length between the focus lens and the image sensor is disposed between the light-emitting surface of the light beam and the image sensor opposite to each other. 5. The focus adjusting device according to claim 4, wherein the optical member can be moved forward and backward by the optical member moving means. 6. The focus adjusting device according to claim 4, wherein the optical member is a low-pass filter. 7. The focus adjusting device according to claim 4, wherein the optical member is an infrared cut filter.