JPH05341166A - Lens-barrel - Google Patents

Abstract

PURPOSE:To make the quantity of light of a mirror lens continuously adjustable by disposing two polar screens in a photographing optical path, and rotating one of the screens by means of an actuator. CONSTITUTION:Two polar screens 9, 10 are disposed in the optical path of photographing lenses 6-8 and one of the screens is rotated so that quantities of light can be adjusted continuously; i.e., an image is formed on a CCD by turning on of the power switch of a camera main body and at the same time a signal indicating brightness is transmitted to the IC 14a of an electronic circuit board 14 in accordance with a signal input to an IC in the camera main body. The IC 14a carries out communications via the contact 1a of the camera main body in accordance with the signal and drives a motor 12, thus rotating the polar screen 9 via a gear 13. The direction of polarization of the polar screens 9, 10 can thus be changed relative to each other and as a result quantities of light can be adjusted continuously.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens barrel such as an interchangeable lens for a video camera.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional example of an interchangeable lens for a video camera. 1 is a mount to be attached to the camera body, 32 is a fixing member, 3 is a lens barrel having a threaded portion 3a at its tip, 4 is a distance ring for screwing the lens barrel 3 and holding the focusing lens 6,
5 is a light shielding member, 7 and 8 are lens groups, 34 is an IC 34a
, 34b are electronic circuit boards, and 34a and 34b are ICs that communicate with the ICs in the camera body. With the above configuration, when the lens is attached to the camera body, the lens and the camera communicate with each other through the contact 1a, and the camera body can identify the attached lens and operate properly. Further, it is possible to perform a focusing operation by rotating the distance ring 4.

[0003]

Generally, in the interchangeable lens as described above, it is difficult to adjust the light amount due to the change in area.
A light amount adjustment filter (generally referred to as an ND filter) 30 as shown in FIG. 9 is used to adjust the light amount. However, it is very difficult to make a proper selection with respect to the filter 30, and it is difficult to replace the filter 30 during shooting with a video camera, which makes it difficult to take a picture.

FIG. 10 shows a modification of the conventional example, which is an interchangeable lens in which a light quantity adjusting filter 40 is inserted from the side. The operability of this interchangeable lens is good, and the filter 40 can be quickly exchanged, but it is necessary to prepare a large number of filters, and it is very difficult to decide which filter to use.

Further, when switching the filters, the photographing is interrupted, which is very inconvenient.

An object of the present invention is to provide an improved lens barrel which does not require troublesome filter replacement work.

[0007]

In the lens barrel of the present invention, two polarizing filters are arranged in the optical path of the taking lens, and one of them is rotated so that the light quantity can be continuously adjusted. Is characterized by.

[0008]

1 is a sectional view of a lens barrel according to a first embodiment of the present invention. The members shown in FIG. 1 with the same reference numerals as those in FIG. 9 are the same as the constituent members of the conventional lens barrel, and the description thereof will be omitted. FIG. 2 is a cross sectional view.

In FIGS. 1 and 2, reference numeral 2 is a fixed portion which holds the polarizing filter 10 and the lens group 8. Reference numeral 11 denotes a filter holding member which holds the polarization filter 9 and which is rotated around the optical axis by the gear 13 and the motor 12. 1
Reference numeral 4 denotes an electronic circuit board on which the ICs 14a and 14b are mounted, and the ICs 14a and 14b communicate with the camera body via the contacts 1a to control the motor 12.

In the above structure, as shown in FIG. 3, when the power switch 17 of the camera body 20 is turned on, an image is formed on the CCD 21, and at the same time the I inside the camera body 20 is formed.
Based on the signal input to C14 ″, a signal indicating the brightness is transmitted to the ICs 14a and 14b in the lens body 19 through the contacts 1a and 20a. The rotation direction of the motor 12 and the increasing / decreasing direction of the light amount are It is defined.

The motor 12 is driven based on the above signal,
By rotating the polarization filter 9, the polarization directions of the filters 9 and 10 can be relatively changed. As a result, it becomes possible to continuously adjust the light amount. FIG. 4 shows a graph of the relative angle of the first and second polarization filters and the amount of transmitted light.

FIG. 5 is a sectional view of the second embodiment of the present invention. In general, when the spectral transmittance when two polarizing filters are superposed is not uniform as shown in FIG. 6a, an appropriate color tone may not be expressed only by the adjustment function (generally white balance adjustment) of the camera body. In FIG. 5, reference numeral 16 is a filter having a spectral transmittance opposite to that of FIG. 6a, as shown in FIG. 6b. Others are the same as the above-mentioned embodiment. With the above configuration, it is possible to continuously adjust the light quantity with an optical system that can express an appropriate color tone.

Further, when photographing in a dark state, one polarizing filter dims the light. Therefore, when the light quantity becomes insufficient, the first and second polarizing filters may be retracted from the optical path. Good.

FIG. 7 shows a third embodiment. The magnet 1 is attached to the filter holding member 11 'that rotates around the optical axis.
1'a is provided, and the Hall element 2'a is fixed to the fixed portion 2 '. The other structure is the same as that of the first embodiment. With the above configuration, the relative angle between the polarization directions of the polarization filters 8 and 9 can be known by the voltage generated in the Hall element 2'a, and the desired transmittance can be reached quickly.

It is also possible to uniquely set the light quantity set value intended by the photographer (generally, manual light quantity adjustment). Obviously, similar control can be performed by using an optical sensor, a brush and a pattern instead of the Hall element and the magnet. The relationship between the voltage of the Hall element and the transmittance of the two filters is shown in the graph of FIG.

Further, as a method for promptly adjusting the light quantity without providing the position detecting means, the motor may be controlled by comparing the rotation quantity of the motor with the light quantity change quantity incident on the CCD 21. Good. For example, when the light amount of the CCD 21 changes while the motor is stopped, the motor may be rotated in a predetermined direction and by a predetermined amount. Further, when the outdoor brightness changes while the motor is rotating, the amount of rotation of the motor and the change in the amount of light of the CCD 21 are compared and calculated, and the number of rotations of the motor may be changed based on the result. Further, in the above, when the change in the light amount is not stable, the motor may be temporarily stopped, and a delay circuit may be provided to drive the motor after the amount of change in the outdoor brightness is stabilized.

[0017]

As described above, in the lens barrel of the present invention, two polarizing filters are arranged in the photographing optical path and one of them is rotated by the actuator to continuously adjust the light amount of the mirror lens. Made possible.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a lens barrel according to a first embodiment of the present invention.

2 is a cross-sectional view of the lens barrel shown in FIG.

FIG. 3 is a schematic diagram showing an electrical configuration of both when the lens barrel of FIG. 1 is attached to a camera body.

FIG. 4 is a graph showing the relationship between the relative rotation angle of the polarizing filter and the transmittance in the first embodiment of the present invention.

FIG. 5 is a vertical sectional view of a lens barrel of a second embodiment of the present invention.

FIG. 6A shows the transmittance of a polarizing filter of the lens barrel of the second embodiment, and b shows the transmittance of another polarizing filter of the lens barrel.

FIG. 7 is a transverse sectional view of a lens barrel of a third embodiment of the present invention.

8 is a diagram showing the relationship between the output of the Hall element and the transmittance of the polarization filter in the embodiment of FIG.

FIG. 9 is a cross-sectional view of a conventionally known interchangeable lens barrel for a video camera.

FIG. 10 is a longitudinal sectional view of another conventionally known interchangeable lens barrel.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Mount 2,22,42 ... Fixed part 3 ... Lens barrel 4 ... Distance ring 5 ... Light-shielding cylinder 6,7,8 ... Lens group 9,10 ... Polarization filter 11 ... Filter holding member 12 ... Motor 13 ... Gear 14 ... Electronic circuit board

Claims (5)

[Claims] 1. A first polarizing filter provided in the optical path of a taking lens, and a first polarizing filter rotatably provided around the optical axis of the taking lens at a position in front of or behind the first polarizing filter. A second polarizing filter and an actuator for rotationally driving the second polarizing filter,
Control means for suppressing rotation of the actuator,
A lens barrel having: 2. The lens barrel according to claim 1, wherein the first and second polarizing filters are configured to be retractable from the optical path of the taking lens. 3. The lens barrel according to claim 1, further comprising detection means for detecting a rotation amount, a rotation position, and a rotation direction of the second polarizing filter. 4. The control means has a function of controlling the rotation of the second polarization filter based on the change in the amount of incident light passing through the taking lens and the rotation amount of the second polarization filter. The lens barrel according to claim 1, wherein: 5. The lens barrel according to claim 1, further comprising a spectral characteristic correction filter.