Television – Camera – system and detail – Optics
Reexamination Certificate
1995-04-04
2002-06-18
Ho, Tuan (Department: 2612)
Television
Camera, system and detail
Optics
C348S360000, C396S071000
Reexamination Certificate
active
06407774
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an adapter for an interchangeable lens, for establishing a connection between a video signal processing system for a video camera capable of automatically controlling exposure and an interchangeable lens system for a still camera capable of automatically controlling exposure.
2. Related Background Art
Recently, there has been disclosed a lens system for a video movie system, which is different from an ordinary system composed of integrating a camera and a lens and which is capable of using a variety of interchangeable lenses. As an interchangeable lens system of the type described above, a system for a still camera such as a single-lens reflex camera has been known and a variety of lenses including special lenses for a variety of purposes have come into the market. However, since use of the interchangeable lens system is in the early stage and therefore its market has not been established yet, it is not practical that a variety of special lenses which characterizes the interchangeable lens system are manufactured in the early stage of the promotion of the video movie system. Therefore, it is effective to utilize the conventional interchangeable lenses for a still camera for a single-lens reflex camera. In a case where the video movie camera and the interchangeable lens for a still camera are connected to each other, a conversion adapter must be used because of the following reasons (a) to (c):
(a) Since the mount for the interchangeable lens system for the video movie and that for the interchangeable lens system for the still camera are different from each other, a proper adaptation means for them must be employed.
(b) Since the video movie camera and the still camera have different distances between the imaging surface and mount position, the difference in the optical passage must be aligned.
(c) Since the interchangeable lens system for the video movie and the interchangeable lens system for the still camera have different communication formats for transmitting/receiving various data required to perform the control and as well as the data format/control format are different, they must be adapted to each other.
The video movie camera and the still camera are respectively arranged to be significantly different from each other in their status, the imaging status and the functions. Therefore, also the AE (Automatic Exposure) control method is different between the video camera and the still camera. Then, the AE control method will now be described schematically.
First, the AE control method employed in a conventional camera integrated type VTR will now be described with reference to FIG.
1
. Imaging light made incident through a lens optical system
1
is first subjected to a light quantity adjustment in an iris diaphragm
2
before an image of a subject is formed on an image pickup element
3
, the image of the subject being then photoelectrically converted on the image pickup element
3
. A signal obtained from the image pickup element
3
is converted into a TV composite video signal by a camera signal processing circuit
4
and a camera encoder
5
before it is transmitted to outside. At this time, brightness signal Y&ggr; obtained from the camera signal processing circuit
4
is subjected to an integral process in an integrator
6
before a differential signal denoting the level difference from a reference level supplied from a reference value generating circuit
19
is generated by a calculator
18
. The differential signal thus-generated is, as an AE control signal, transmitted to a driver
13
so that the iris diaphragm (a diaphragm mechanism for adjusting exposure) is controlled via an actuator
14
.
Then, an AE control method employed in a VTR of an interchangeable lens method will now be described with reference to FIG.
2
. Referring to
FIG. 2
, a right portion with respect to a mount portion MT designated by a central alternate long and short dash line forms a camera unit CM, while the left portion forms a lens unit LS. An image of a subject formed on an imaging surface of the image pickup element
3
after it has passed through the iris diaphragm
2
is photoelectrically converted by the image pickup element
3
before it is transmitted as an image signal. The image signal supplied to the camera signal processing circuit
4
from the image pickup element
3
is subjected to a &ggr; (gamma) conversion or the like so that it is fetched as a video signal composed of color signal C and brightness signal Y&ggr; before it is, in the form of a composite video signal, transmitted outside from a camera portion via camera encoder
5
arranged to act in accordance with the NTSC method. The brightness signal Y&ggr; transmitted from the above-described camera signal processing circuit is supplied to the integrator
6
, an amplifier (AMP)
7
and a DC level shift circuit
8
which constitute an AE circuit so that the AE control signal for controlling the iris diaphragm
2
in such a manner that proper exposure can be obtained is generated. In the above-described AE circuit, the brightness signal Y&ggr; is integrated by the integrator
6
before it is amplified to a predetermined level by the amplifier
7
. Then, the amplified signal is made to be the above-described reference level by a DC level shift circuit
8
. A method of setting AE control data in accordance with the level difference from the above-described reference level is, as described later, arranged in such a manner that the amplifier
7
and the DC level shift circuit
8
are adjusted so as to generate communication data, for example, as shown in
FIG. 3
, in accordance with the brightness difference of the received signal. A signal generated in the AE circuit is converted into a digital signal by an A/D converter
9
before it is supplied to a microcomputer
10
for the camera so as to be transmitted to the lens unit LS as the AE control signal via a data communication passage
21
at predetermined timing. At this time, the data communication passage
21
is connected to a microcomputer
11
for the lens so that all of communication data items are received by the microcomputer
11
for the lens before the communication data is converted into an analog signal by a D/A converter
12
. Then, the analog signal is supplied to the driver circuit
13
. Then, the iris diaphragm
2
is controlled via the actuator
14
.
FIG. 3
is a table which illustrates representative value of AE control data to be transmitted to the lens unit LS which is assigned by, for example, 8 bits (256 steps). As shown in
FIG. 3
, each level difference is expressed by an EV (diaphragm) value such that an instruction is made in a case where the value is+1 EV to perform a diaphragm of 1 EV (so-called “for one diaphragm”) with respect to the optimum exposure. Furthermore, a reference value for the AE control is determined to be 32 in this case and the action of the iris is inhibited. In the portion including the lens, control data transmitted from the portion including the camera is again converted into an analog signal by the D/A converter
12
so as to drive the actuator
14
via the driver
13
. As a result, the iris diaphragm
2
is operated. As described above, the control signal including a control signal for stopping the operation of the iris in accordance with the level of the video signal is, as AE control information, formed into a digital code so as to be transmitted. Therefore, the apparent gain different of the camera can be neglected and as well as the difference in the dynamic range of the camera can be made to be regardless. Furthermore, since the reference values are unified in accordance with a predetermined code, compatibility can be maintained as desired.
Finally, the AE control method employed in a still camera will now be described with reference to FIG.
4
. Imaging light made incident upon the lens optical system
1
is first subjected to a process in which the quantity of light is adjusted by the iris diaphragm
2
similarly to the
Mabuchi Toshiaki
Ohta Seiya
Canon Kabushiki Kaisha
Ho Tuan
Robin Blecker & Daley
LandOfFree
Adapter device for interchangeable lens of camera which... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Adapter device for interchangeable lens of camera which..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Adapter device for interchangeable lens of camera which... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2973807