Waist level viewfinder

A waist level viewfinder for a camera arranged to permit direct observation from above a focusing plate of the image of an object formed on the focusing plate. The viewfinder includes a first light shielding tubular member which is attachable to and detachable from the camera and a second light shielding tubular member which is slidable relative to the first tubular member and which is provided with an eyepiece. The eyepiece is pivotally mounted so as to be capable of being retracted out of the viewing path of the reticle plate. The viewfinder is thus arranged to provide improved light shielding characteristics when it is in use and to have improved portability when not in use while also facilitating diopter correction.

The present invention relates to photographic equipment and more 
specifically to a waist level viewfinder for a single lens reflex camera. 
Waist level viewfinders of the type arranged to permit direct observation 
of the image of an object to be photographed which is formed on a focusing 
plate from above the focusing plate have been known in the art. However, 
conventional waist level viewfinders are usually composed of a hood which 
is arranged to be folded when the viewfinder is not in use. Therefore, in 
conventional viewfinders of this type, it has been found impossible to 
provide a sufficient distance between the focusing plate and the upper end 
face of the light shielding part thereof in order to secure good light 
shielding characteristics. 
In addition to this drawback, the conventional viewfinder of this type 
involves another disadvantage in that the image of the object to be 
photographed which is formed on the focusing plate is not easily 
observable due to conversely incident light from the upper end of the 
light shielding member. A further drawback of conventional viewfinders of 
this type is that, in the case of a camera having a light measuring 
mechanism disposed in the viewfinder optical system, the light measurement 
tends to exhibit errors. 
In determining the composition of a photograph of the object which is 
imaged on the focusing plate with a waist level viewfinder of the type 
discussed, this composition is determined directly by observing the image 
of the object. Then, in determining focal length, a focusing operation is 
effected generally by observation of an enlarged image on the reticle 
plate through a magnifying lens which is normally provided in the light 
shielding portions of the viewfinder. However, in the case of conventional 
waist level viewfinders, it has been found impossible to alter the 
distance between the focusing plate and the magnifying lens while the 
latter is in use. Therefore, it is impossible to correct diopter while the 
magnifying lens is in its operative position. This has been found to cause 
an additional problem. 
Accordingly, the present invention is directed toward providing a structure 
for a viewfinder dealing with the aforementioned problems and more 
particularly with a waist level viewfinder wherein a light shielding 
mechanism formed by a plurality of slidable tubes arranged to provide 
excellent portability and excellent light shielding effects are arranged 
to enable operation of the viewfinder with a magnifying lens without 
interfering with diopter correction. 
SUMMARY OF THE INVENTION 
Briefly, the present invention may be described as a viewfinder for a 
camera including a focusing plate adapted to permit from above the 
focusing plate direct observation on the focusing plate of an image of an 
object to be photographed comprising a first and a second tubular light 
shielding member defining a viewing path through which the focusing plate 
may be viewed, eyepiece means mounted on one of the first and second 
tubular members along the viewing path, said tubular members being mounted 
in generally concentric relationship and being adapted to be moved 
relative to each other, and pivot means for enabling the eyepiece means to 
be pivoted out of the viewing path in a retracted position to enable an 
image on the focusing plate to be viewed directly. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its use, reference 
should be had to the accompanying drawings and descriptive matter in which 
there are illustrated and described preferred embodiments of the invention 
.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows an overall assembly of a camera with a waist level viewfinder 
of the type to which the present invention relates wherein the viewfinder 
comprises first and second light shielding tubular members 2 and 3, the 
first light shielding member 2 having a lower end thereof arranged to be 
attachable to and detachable from a camera body 1. The second light 
shielding member 3 is slidably fitted on the first light shielding member 
2. On the outer circumferential face of the second member 3 there is 
provided a knurled part 4 to enable firm gripping of the equipment. 
A hood 5 is mounted on the upper end of the second light shielding member 3 
and a magnifying lens 8 serving as an eyepiece is secured to a supporting 
plate 6 through a fixing frame 7. The supporting plate 6 is secured to a 
shaft 11 which is rotatably carried by the second light shielding member 
3, as also seen in FIG. 2. As best seen in FIG. 2, the shaft 11 is urged 
to rotate in a counterclockwise direction by a spring 10. 
An operation knob 9 secured to the shaft 11 is provided to enable the shaft 
11 to be rotated so as to effect pivotal movement of the supporting plate 
6 and the magnifying eyepiece 8. 
With reference to FIG. 2, there is shown a photography lens 1a with the 
camera being arranged so that light from an object to be photographed will 
pass through the lens 1a and will be reflected upwardly by a reflecting 
mirror 1b so as thereby to produce an image of the object on a reticle 
plate 1c. In detecting the focal length for the object to be photographed, 
the image of the object and the focusing plate 1c are observed in an 
enlarged view through the magnifying eyepiece 8. 
Formed along the upper end of the outer circumferential face of the first 
light shielding tubular member 2 are a plurality of guide claws 2a which 
are adapted to engage in a groove 3b formed in the inner circumference of 
the second light shielding member 3. As best seen in FIG. 3, the groove 3b 
consists of groove parts 3b.sub.1 and 3b.sub.2 which are arranged to stop 
sliding movement of the second light shielding tube 3 by engagement with 
the guide claws 2a. The part 3b.sub.2 is arranged to allow the second 
light shielding member 3 to slide therealong by the engagement with the 
guide claws 2a. Furthermore, at the lower end of the second light 
shielding tube 3 there is provided an inwardly directed flange 3a which is 
in close contact with the outer circumferential face of the first light 
shielding member 2 and which contributes to the light shielding effect 
which is provided as well as to maintaining the assembly dustproof while 
also exhibiting antifriction characteristics. 
Provided on the lower end of each guide claw 2a is a plate spring (not 
shown) which is arranged to reduce play between the second light shielding 
tubular member 3 in the direction of the optical axis of the viewfinder 
when the guide claws 2a engage with the groove part 3b.sub.1 or with a 
groove part 3b.sub.3 of the groove 3b. 
FIG. 2 shows the viewfinder in the state when it is in use. In order to 
convert the viewfinder from its usable state to a state where it is not in 
use, the knurled part 4 provided on the second light shielding tube 3 is 
first held by the operator and the second light shielding tube 3 is 
rotated counterclockwise relative to the optical axis of the viewfinder to 
bring the guide claw 2a to the part 3b.sub.2 of the groove 3b (see FIG. 
3). Thereafter, the second light shielding member 3 is slidably moved 
along the guide claws 2a in order to have the first light shielding member 
2 set within the second light shielding member 3. Subsequently, the second 
light shielding member 3 is rotated clockwise relative to the optical axis 
of the viewfinder until the guide claw 2a comes into engagement with the 
part 3b .sub.3 of the groove 3b. In order to bring the viewfinder from 
this state into a condition where it is in use, the aforementioned 
operation is carried out in reverse order. The second light shielding 
member 3 is rotated counterclockwise and is then pulled upwardly along the 
groove part 3b.sub.2 which is formed to extend in a vertical direction. At 
a point where the upward sliding movement is restrained, the second light 
shielding member 3 is then turned clockwise in order to arrange the 
viewfinder in its condition of use. 
Provided on the free end side of the supporting plate 6 is a locking piece 
12 which is arranged to engage a locking member 13 provided in the lower 
part of the first light shielding tube 2 when the supporting plate 6 is 
rotated clockwise by means of the operation knob 9. The locking member 13 
is formed, for example, as a plate spring or the like having resilient 
characteristics in the direction of the viewfinder optical axis with the 
member 13 being free in the radial direction relative to the optical axis. 
When the magnifying eyepiece 8 is not used for determining the composition 
of a picture of the image of an object to be photographed formed on the 
reticle plate 1c, the supporting plate 6 is rotated against the force of 
the spring 10 until the locking piece 12 and the locking member 13 come 
into engagement. The magnifying eyepiece 8 is then maintained in a state 
out of use by this engagement. In order to use the magnifying eyepiece 8, 
the operation knob may be again rotated in a reverse direction in order to 
disengage the locking piece 12 and the locking member 13 by causing 
deformation of the locking member 13. The supporting plate 6 is then 
permitted to rotate by means of the force of the spring 10 in order to set 
the magnifying eyepiece in the position illustrated. 
In cases where the viewfinder stowing operation is effected with the 
magnifying eyepiece in its out-of-use position, since the engagement 
between the locking piece 12 and the locking member 13 is releasable by 
rotation of the second light shielding tube 3, as shown in FIGS. 4 and 5, 
the urging force of the spring 10 causes the supporting plate 6 to rotate 
in order to keep the magnifying eyepiece in its in-use state when the 
second light shielding tube 3 is rotated about the viewfinder optical 
axis. Therefore, a stowing operation for the viewfinder may also be 
smoothly effected even under such a condition. Additionally, in the case 
of the embodiment shown in FIG. 2, a screw 18 is provided at the second 
light shielding tube 3 in order to permit fixing of the second light 
shielding tube 3 relative to the first tube 2 halfway along its path of 
sliding movement. This enables the operator of the camera to determine the 
position for the magnifying eyepiece 8 at a point suitable for diopter by 
adjusting the length of the optical path from the focusing plate 1c to the 
magnifying lens 8. 
Another embodiment of the invention is depicted in FIG. 6. In this 
embodiment, magnetic means are used as the locking or holding means for 
the eyepiece unit. As shown in FIG. 6, elements which are the same as 
elements shown in the embodiment previously described in connetion with 
FIG. 2 are identified by the same reference numerals. A magnetic body 15 
which is composed of an iron member or the like is attached to the lower 
part of the first light shielding tube 2 through an elastic member 16 
which may be composed of soft foamed urethane. A magnet 17 is arranged so 
as to attract the magnetic body 15. When the supporting plate 6 is rotated 
against the force of the spring 10 by means of the operation knob 9, the 
magnetic body 15 will be attracted by the magnet 17 in order to keep the 
supporting plate 6 and the magnifying eyepiece 8 in its position out of 
use. The elastic member 16 is provided in order to bring the magnetic body 
15 and the magnet 17 into interfacing contact. In the embodiment of FIG. 
6, with the magnifying lens or eyepiece 8 in its out-of-use position, the 
second light shielding tube 3 is rotated on the viewfinder optical axis. 
As a result of this rotation, the contacting area between the magnetic 
body 15 and the magnet 17 will be decreased until the attracting force of 
the magnet 17 diminishes and becomes smaller than the urging force of the 
spring 10. As a result, the supporting plate 6 will be released from the 
holding action of the magnet 17. The supporting plate 6 is then turned by 
the force of the spring 10 and the magnifying lens 8 will be brought to 
its in-use position. Thereafter, the stowing operation for the viewfinder 
may be effected without difficulty. 
Thus, as will be seen in accordance with the foregoing description, the 
waist level viewfinder according to the present invention is arranged with 
the light shielding means thereof formed by a plurality of slidable light 
shielding tubes. Despite the highly simplified structural arrangement 
provided, the waist level viewfinder nevertheless offers excellent 
features, both from the point of view of portability and light shielding 
capability. The distance between the focusing plate and the magnifying 
lens is variable as desired and therefore, in accordance with a very 
advantageous feature of the invention, diopter can be corrected. The 
provision of the holding means for holding the magnifying lens in its 
unused position in combination with the arrangement for releasing the lens 
from the holding means in association with a stowing operation on the 
viewfinder enables the operator to bring the viewfinder into its stowed 
position always by means of the same stowing operation irrespective of 
whether the magnifying lens is in the held position or not. Operability of 
the viewfinder is therefore improved by the arrangement in accordance with 
the invention. 
Although the waist level viewfinder of the invention comprises two light 
shielding tubes in each of the aforementioned embodiments, it should be 
understood that the invention is not limited to such an arrangement of 
these specific embodiments but that the light shielding part of the 
viewfinder may be formed differently, for example, with three or more 
light shielding tubes. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the inventive principles, it 
will be understood that the invention may be embodied otherwise without 
departing from such principles.