JP3461130B2 - Auto iris adaptive small zoom lens - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solid-state image pickup device (C
The present invention relates to an auto-iris adaptive small-sized zoom lens suitable for use in a camera-integrated video tape recorder (video camera) equipped with a CD), a digital still camera, or the like.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional small-sized zoom lens mounted on a video camera. As shown in the drawing, it is composed of a first lens group to a fourth lens group in order from the light incident side. . Here, the first lens group is the front lens group 20, and the third lens group is the fixed master 22, both of which are fixed lenses.

On the other hand, the second lens group is the variator group 21, and it is possible to change the zoom magnification by moving in the optical axis direction. As shown in FIG. 7A, the state in which the variator group 21 is closest to the front lens group 20 is the wide state (W) in which the widest angle is obtained, and as shown in FIG.
The state closest to the fixed master 22 is the telephoto state (T) that is the most telephoto state. The fourth lens group is the moving master group 23, and moves in the optical axis direction to change the distance from the fixed master 22 to adjust the focus on the image plane of the CCD 24, as shown in FIG. ing.

[0004] Then, the variator group 21 and the fixed master 22
And an iris 25 for exposure control is provided between the iris 2 and the fixed master 22 at a position adjacent to the fixed master 22.
Reference numeral 5 controls exposure by adjusting the amount of light incident on the lens after the fixed master 22 under the control of a microcomputer (not shown).

[0005]

The conventional compact zoom lens constructed as described above is required to be further miniaturized as the video camera is miniaturized. However,
It is very difficult to further reduce the size of the zoom lens structure as described above.

[0006]

In order to solve the above problems BRIEF SUMMARY OF THE INVENTION, engagement LUZ Murenzu the present invention includes: a turn the front lens group from the object side, a variator group, and the fixed master group, and a moving master group In a zoom lens including an arrayed lens group and an aperture mechanism arranged between the variator group and the fixed master group and at a fixed position adjacent to the fixed master group, an anti-movement of the movable master group The lens group is arranged so that a light beam traveling toward the peripheral portion at the maximum image height away from the center of the subject image-forming surface formed on the image sensor provided on the subject side does not pass through the diaphragm center portion of the diaphragm mechanism in a predetermined zoom region. With the configuration, when the light beam heading for the peripheral portion does not pass through the diaphragm central portion of the diaphragm mechanism, the diaphragm mechanism does not block all of the light beam. Ri is characterized in that it has a control means for controlling the mechanism, further, the control means,
In addition to the control of the diaphragm mechanism, the charge storage time of the image sensor is controlled to keep the brightness level of the signal output from the image sensor constant, and the control means is further provided. In the wide-angle zoom area including a part or all of the predetermined zoom area, the brightness level of the signal output from the image sensor is adjusted by using the control of the aperture mechanism and the control of the image sensor together. On the other hand, in the zoom area other than the wide-angle zoom area, the brightness level of the signal output from the image sensor is maintained constant only by controlling the diaphragm mechanism while keeping the brightness constant.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the auto iris adaptive small-sized zoom lens according to the present invention, a light beam heading to the periphery of the image plane of the CCD provided in the rear stage of the zoom lens does not necessarily pass through the iris center. It is characterized by achieving a compact size by adopting a good zoom lens configuration, and performing iris control adaptively so that vignetting due to iris does not occur in the peripheral portion of the screen at that time.

[0008] FIG. 1 is a diagram showing an auto-iris adaptive small-sized zoom lens according to an embodiment of the present invention, in which the conventional small-sized zoom lens shown in FIG. Both are configured to be 8% smaller. The zoom lens according to the present invention thus miniaturized, like the conventional small zoom lens,
It comprises a first lens group to a fourth lens group, the first lens group is a front lens group 1, the second lens group is a variator group 2, the third lens group is a fixed master 3, and the fourth lens group is a movable master 4. Has become.

Here, the front lens group 1 and the fixed master 3 are both fixed lenses, and as shown in FIGS. 1A to 1E, the variator group 2 is fixed from the position closest to the front lens group 1 to the fixed master 3. The zoom process from the wide state (W) to the telephoto state (T) is realized by moving the zoom process to the position closest to. 1 (b) is a wide middle state (WM), FIG. 1 (c) is a middle state (M), and FIG.
(D) is a middle telephoto state (MT), and shows zoom positions between the wide state (W) and the telephoto state (T), respectively.

An iris 5 for exposure control is provided between the variator group 2 and the fixed master 3 and at a position adjacent to the fixed master 3. The iris 5 is controlled by a microcomputer as described later. Exposure control is performed based on the signal. Then, the CCD 24 is provided at the subsequent stage of the moving master 4.
Is arranged, and the moving master 4 moves in the optical axis direction so that focusing is performed on the image plane of the CCD 24. The charge storage time and timing of the light receiving element on the image plane of the CCD 24 are controlled based on a shutter control signal from a microcomputer described later.

[0011] Next, with reference to FIG. 1 and FIG. 2, light ray passing paths of a light ray toward the center of the image forming surface of the CCD 24 and a light ray toward the peripheral portion of the image forming surface of the CCD 24 will be described. Here, FIG. 2 shows the image plane of the object in the CCD 24, where 24a indicates the center of the image plane and 24b indicates the peripheral area of the image plane, and the distance between 24a and 24b is the maximum image height h. There is.

[0012] The light ray directed to the image plane center portion 24a of the CCD 24 is indicated by A _W in the wide state shown in FIG. 1A, and the light ray directed to the image plane peripheral portion 24b of the CCD 24 is B.
_Indicated by _W. Further, in the zoom position of each in FIG. 1 (b) to (e), the light rays towards the image plane center unit _{24a, A WM, A M, A} MT, indicated by A _T, the imaging surface periphery 24b The rays going to are denoted by B _WM , B _M , B _MT , B _T.

[0013] Here, focusing on the light rays directed to the imaging surface peripheral portion 24b in the wide state (W), the middle wide state (MW), and the middle state (M) shown in FIGS. 1A to 1C, It can be seen that the lower rays of the rays B _W , B _WM and B _M pass above the center of the iris 5. That is, in the wide state (W), the middle wide state (MW), and the middle state (M), the light rays B _W , B _WM , and B _M traveling toward the image forming surface peripheral portion 24 b of the CCD 24 pass through the center of the iris 5. It is not.

[0014] As described above, the fact that the light beam heading for the image-forming surface peripheral portion 24b does not pass through the center of the iris 5 means that the light beam is incident on the image-forming surface peripheral portion 24b when the iris 5 is narrowed to the limit. Vignetting occurs at the periphery of the screen, which means that it does not reach.

[0015] Therefore, for example, in the wide state (W) shown in FIG. 1A, the lower ray of the light ray B _W directed to the peripheral portion 24b of the image plane is lowered to the lower side of the center of the iris 5 and the light ray B _W Considering that the light path is changed so that a part thereof passes through the center of the iris 5, it is necessary to increase the aperture of each lens in the variator group 2.

The variator group 2 includes a meniscus concave lens 2a,
Increasing the aperture of the meniscus concave lens 2a and the concave lens 2b, which is composed of the concave lens 2b and the convex lens 2c, leads to an increase in the distance between the meniscus concave lens 2a and the concave lens 2b at the same time. Further, when increasing the aperture of the convex lens 2c, there is no problem if the edge of the convex lens 2c has some margin, but if there is no margin, it is necessary to secure the edge for a predetermined length or more, so the lens thickness increases. .

As described above, in order to lower the lower ray of the light beam B _W directed to the imaging surface peripheral portion 24b to the lower side of the center of the iris 5, each lens in the variator group 2 is also moved in the aperture direction.
It is also necessary to increase the size in the optical axis direction.

On the other hand, the wide middle state (W
Also in M), the lower ray of the light beam B _WM directed to the peripheral portion 24 b of the image plane is lowered below the center of the iris 5, and the light ray passage path is changed so that a part of the light ray B _WM passes through the center of the iris 5. To do so, it is necessary to increase the aperture of each lens in the front lens group 12.

[0019] The front lens group 1 is composed of a meniscus concave lens 1a, a meniscus convex lens 1b, and a meniscus convex lens 1c. However, when the aperture of the meniscus concave lens 1a is increased, the mass of the lens 1a is significantly increased, and When the apertures of the meniscus convex lens 1b and the meniscus convex lens 1c are increased, it is necessary to secure the edge of a predetermined length or more, so that the thickness is increased.

As described above, in order to lower the lower ray of the light beam B _WM directed to the peripheral portion 24b of the image plane to the lower side of the center of the iris 5, each lens in the front lens group 1 is also moved in the radial direction and the light. It is also necessary to increase the size in the axial direction.

[0021] As described above, in the zoom lens according to the present invention, at the zoom position from the wide state (W) to the middle state (M), the light beam originally directed to the image forming surface peripheral portion 24b of the CCD 24 is the iris 5. Where it should be configured to pass through the center, it was configured not to pass through the center of the iris 5. With such a configuration, it is possible to significantly reduce the size in the aperture direction and the optical axis direction as compared with the conventional zoom lens.

Next, shutter control of the CCD 24 and exposure control of the iris 5 will be described. FIG. 3 shows the CCD 24 in the auto iris adaptive zoom lens according to the present invention.
3 is a block diagram showing a control system of an iris 5. FIG. In the figure, 5 is the above-mentioned iris, and 24 is a CCD. Exposure control is performed by the iris 5 based on an iris control signal from the microcomputer 10, and a timing generator (TG) based on a shutter control signal from the microcomputer 10. ) 11 generates a timing signal, and the CCD signal is output from the CCD 24 based on this timing signal.

[0023] Then, 6 removes a noise component from the CCD signal output from the CCD 24 and outputs A from the microcomputer 10.
A CDS / AGC that automatically adjusts an input signal to a predetermined signal level based on a GC control signal, 7 is an A / D converter that converts a CCD signal adjusted to a predetermined level into a digital signal form, and outputs the converted signal. It is a DSP that performs a predetermined video process process on the CCD signal from the A / D converter and outputs the recording signal to the recording / reproducing unit 9.

[0024] Further, 10 exchanges control signals with the DSP 8 and the recording / reproducing unit 9, the iris 5 has an iris control signal, the TG 11 has a shutter control signal, and C
The DS / AGC 6 is a microcomputer that outputs an AGC control signal. Then, the TG 11 outputs a timing signal required when the CCD 24 outputs the CCD signal based on the shutter control signal from the microcomputer 10. Furthermore,
Information indicating the iris opening is fed back from the iris 5 to the microcomputer 10.

With the above-described configuration, the iris control in the iris 5 and the shutter control in the CCD 24 are performed, and the AGC control in the CDS / AGC 6 is performed as necessary.

FIG. 4 is a diagram showing iris control, shutter control, and AGC control performed by the microcomputer 10. The vertical axis represents the iris opening of the iris 5, the shutter speed of the CCD 24, and the AGC control amount of the CDS / AGC 6. In each case, the horizontal axis indicates the brightness of the subject. In addition, D
Information YL indicating the brightness of the signal input to SP8 is output to the microcomputer 10, and the microcomputer 10 performs each control by comparing the brightness information YL from the DSP 8 with the brightness target value YT.

[0027] First, the brightness information YL input from the DSP 8
Is less than the target value YT, the microcomputer 10 outputs an iris control signal for causing the iris 5 to open the iris. At this time, information indicating the opening degree of the iris is fed back from the iris 5 to the microcomputer 10, but the opening degree of the iris 5 is the full-open value E1 (for example, F1.8.
However, if the brightness information YL from the DSP 8 is still below the target value YT, the microcomputer 10 outputs an AGC control signal to the CDS / AGC 6 to turn on the AGC. That is, when the brightness of the subject imaged by the video camera is lower than the predetermined brightness Ev1, the brightness of the input signal of the DSP 8 is controlled by the electric gain adjustment by the CDS / AGC 6.

[0028] Then, when the brightness of the subject is changed to be between Ev1 and Ev2, that is, the microcomputer 10 causes C
AG to turn off AGC for DS / AGC6
Even if the C control signal is output, the brightness information Y from the DSP 8
When L exceeds the target value YT, the microcomputer 10 outputs an iris control signal to the iris 5 to close the iris.

In this state, the brightness information YL from the DSP 8
The opening of the iris 5 is controlled according to the difference between the target value YT and the target value YT, but the shutter speed of the CCD 24 is fixed to the limit value S1 (for example, 1/60 seconds) of the low speed shutter, and the CD
The AGC control in S / AGC6 is OFF.

Then, the brightness of the subject further increases, the opening of the iris 5 becomes E2 (for example, about F11), and even in this state, the brightness information YL from the DSP 8 still exceeds the target value YT, The microcomputer 10 outputs a shutter control signal to increase the shutter speed of the CCD 24 while fixing the opening of the iris 5 to E2. That is, when the brightness of the subject is between Ev2 and Ev3, the brightness of the input signal of the DSP 8 is controlled by changing the shutter speed of the CCD 24.

[0031] After that, the brightness of the subject is further increased, and the CCD
The shutter speed at 24 becomes the limit value S2 of the high-speed shutter (for example, 1/250 seconds), and even in this state, D
If the brightness information YL from SP8 still exceeds the target value YT, the microcomputer 10 outputs an iris control signal to further close the iris 5 while fixing the shutter speed of the CCD 24 to S2.

By the control as described above, the brightness of the subject is E
If it is less than v1, AG by CDS / AGC6
The brightness of the input signal of the DSP 8 is controlled by C control, exposure control by the iris 5 from Ev1 to Ev2, and shutter speed control of the CCD 24 from Ev2 to Ev3.

As described above, the iris 5 is not narrowed down while the brightness of the subject is lower than Ev3, and the opening of the iris 5 is maintained at E2. Vignetting does not occur in the rays of light.

[0034] When the brightness of the subject exceeds Ev3, the iris 5 may be further narrowed down, and vignetting may occur in the light beam toward the peripheral part b of the image plane of the CCD 24.
Since the brightness of Ev3 is such a brightness as to directly image the sunlight, no problem arises in the case of normal imaging.

In the above embodiment, the opening degree of the iris 5 is E1.
When (F11), the radius from the center of the iris opening is 0.7 mm, and the iris 5 is further narrowed down to F13.
Is 0.6 mm, and F16 is 0.5 mm. On the other hand, in the wide state (W) shown in FIG. 1 (a), the lower ray of the beam B _W is 0.27 mm above the center of the iris 5, and in the wide middle state (WM) shown in FIG. 1 (b),
0.26mm above the central lower ray of the iris 5 of rays B _WM, the middle state (M) shown in FIG. 1 (c), light B _M
The lower ray passes through 0.15 mm above the center of the iris 5.

As described above, in the auto iris adaptive small-sized zoom lens according to the present embodiment, not only the vignetting that occurs in the peripheral portion of the screen is prevented, but also the decrease in the amount of light in the peripheral portion of the screen can be minimized. It has become a structure.

Next, an auto-iris adaptive small-sized zoom lens according to another embodiment of the present invention will be described. An auto-iris adaptive small-sized zoom lens according to another embodiment is characterized in that the CCD 24 and the iris 5 as described above are controlled only in a predetermined zoom position region close to the wide-angle side. Regarding the configuration and the control system block of CCD and iris,
This is as shown in FIGS. 1 and 3.

[0038] Fig. 5 shows changes in the effective image circle Y when the zoom position is changed in the zoom lens shown in Fig. 1. The horizontal axis represents the focal length at the changed zoom position, and the vertical axis represents the focal length. It shows the length of the effective image circle Y which shows how much radius the chief ray passing through the center of the iris 5 forms a circle on the image plane of the CCD 24 at each zoom position.

That is, the length of the effective image circle Y is the CCD shown in FIG.
In the zoom position region where the maximum image height h of 24 is exceeded, the light beam heading to the peripheral portion 24b of the image plane of the CCD 24 always passes through the center of the iris 5. Zoom position area (for example, 3 to 10 times zoom area)
In the above, even when the iris 5 is narrowed down to its limit, vignetting does not occur in the peripheral portion of the screen because the light rays reach the peripheral portion 24b of the image plane.

Therefore, in such a zoom position region, the brightness of the input signal of the DSP 8 is controlled without changing the shutter speed of the CCD 24 as shown in FIG.

On the other hand, in the zoom position area (for example, a zoom area of 1 to 3 times) shown in FIG. 5, the light beam does not reach the image formation surface peripheral portion 24b in a state where the iris 5 is narrowed down to the limit. Instead, vignetting may occur in the peripheral portion of the screen, so the iris control, shutter control, and AGC control shown in FIG. 4 are performed.

As described above, the control shown in FIG. 4 and the control shown in FIG. 6 are switched according to the zoom position area, and the control shown in FIG. 6 is performed in the zoom position area close to the telephoto side to image the subject. At that time, the depth of field does not become shallow, and it becomes easy to focus at the time of close-up imaging in which a flower or a fine object is enlarged in close proximity.

In the above embodiments, the example in which the CCD 24 is arranged in the rear stage of the moving master 4 is shown. However, for example, a prism is arranged in the rear stage of the moving master 4, and light dispersed by the prism is distributed to a plurality of CCDs. It may be configured to form an image.

[0044]

According to the engaging Luz Murenzu the present invention, the maximum image height away <br/> periphery from the center of the object image plane to be formed on the image sensor provided in the counter-object side of the mobile master The zoom lens is configured so that the light beam that goes toward does not pass through the aperture center of the aperture mechanism in the predetermined zoom area,
When the light beam does not pass through the center part of the diaphragm, the diaphragm means controls not to block all of the light beam,
It has become possible to greatly reduce the size of the zoom lens in both the optical axis direction and the aperture direction.

[Brief description of drawings]

FIG. 1 is a diagram showing a lens configuration of an auto-iris adaptive small-sized zoom lens according to the present invention.

FIG. 2 is a diagram showing an image plane of an object on a CCD.

FIG. 3 is a block diagram showing a control system for a CCD and an iris.

FIG. 4 is a diagram showing iris control, shutter control, and AGC control by a microcomputer.

FIG. 5 is a diagram showing changes in effective image circle length in the auto-iris adaptive small-sized zoom lens according to the present invention.

FIG. 6 is a diagram showing another example of iris control, shutter control, and AGC control by a microcomputer.

FIG. 7 is a diagram showing a lens configuration of a conventional compact zoom lens.

[Explanation of symbols]

1, 20 ... Front lens group 2, 21 ... Variator group 3, 22 ... Fixed master 4, 23 ... Moving master group 5, 25 ... Iris 6 ... CDS / AGC 7 ... A / D converter (A / D) 8 ... DSP 9 ... recording reproducing unit 10 ... microcomputer 11 ... timing generator (TG) 24 ... solid-state imaging device (CCD) 24a ... of the subject in the image plane center 24b ... CCD 24 of the subject in the CCD 24 image plane peripheral portion a _W, a _WM , A _M , A _MT , A _T ... Rays of light B _W , B _WM , B _M , B _MT , B _T ... Heading toward the image plane center 24 a ... High Y ... Effective image circle radius

Front page continuation (51) Int.Cl. ⁷ identification code FI H04N 5/235 H04N 5/235 (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 7/10 G03B 7/095 G03B 9 / 00-9/70 G03B 19/02 H04N 5/225 H04N 5/235

Claims (3)

(57) [Claims] 1. A lens group formed by arranging a front lens group, a variator group, a fixed master group, and a moving master group in order from the subject side, between the variator group and the fixed master group, and In a zoom lens including the fixed master group and an aperture mechanism arranged at a fixed position adjacent to the fixed master group, a maximum image from a center of a subject image forming surface formed on an image sensor provided on the side opposite to the subject of the moving master group.
The lens group is configured such that a light beam heading toward a peripheral portion at a high distance does not pass through the diaphragm center portion of the diaphragm mechanism in a predetermined zoom region, and a light beam traveling toward the peripheral portion does not pass through the diaphragm center portion of the diaphragm mechanism. At this time, the zoom lens is provided with a control means for controlling the diaphragm mechanism so that the diaphragm mechanism does not block all of the light rays. 2. The control means keeps the brightness level of a signal output from the image sensor constant by controlling the charge accumulation time of the image sensor in addition to the control of the diaphragm mechanism. The zoom lens according to claim 1. 3. The control means uses the control of the aperture mechanism and the control of the image sensor in combination in a wide-angle zoom area including a part or all of the predetermined zoom area to control the image sensor. While maintaining the brightness level of the signal to be output constant, in a zoom area other than the wide-angle zoom area, the brightness level of the signal output from the image sensor is maintained constant only by controlling the diaphragm mechanism. The zoom lens according to claim 2.