GB2435525A - A viewfinder unit for a camera - Google Patents

Abstract

A viewfinder unit comprising a light source utilises the existing mirror and lens of a camera to project a frame onto the object to be photographed. The viewfinder unit may comprise the following: an image focussing cue unit (e.g. an infra-red dispersal system), a holographic (e.g. laser) raster scan system, light exposure reading equipment. The unit may be self powered. The unit may be shut off by an internal mechanism.

Description

<p>Light Projective viewfinder system.</p>

<p>This invention relates to a projective viewfinder system for non-rangefinder photographic cameras, either Single or Twin Lens Reflex.</p>

<p>In classic portrait photography, the aim of the photographer demands that he or she be constantly aware of the scene the camera will expose. This is usually done by means of sight through a viewfinder system (either directly onto a screen, creating a reversed image, or through a prism, creating an orientated image). Through this, the photographer assesses several key quantities, chiefly focus.</p>

<p>Research has shown that this may not always benefit subject andlor photographer insofar as acquiring desirable results. It has been found that if the photographer maintains a more positive eye contact with his or her subject -be it still life or portrait in nature, greater control over the framed shot can be achieved.</p>

<p>This invention describes a concept which projects a frame through the camera lens and consequently gives a visual cue to the photographer as to what picture will be taken at a specific given point in time.</p>

<p>The diagram shows a cross-section of a typical camera. For the purposes of explanation only, the diagram represents a typical 6cm medium-format camera system though can be applied to a variety of camera designs.</p>

<p>The example described herein is a multifunction unit. Straddling atop the camera (shown as the internal camera, body and mirror array (ICBMA)) is the projector unit itself. A light source (LS) projects light onto a fixed mirror (FM) through a collimator and focussing unit (CFU) optimised for equal length of light travel from lens to mirrors as from lens to exposure media, which as described, can be optionally tripartisised for integration of other components. The mirror is held in place with pre-positioned guides, the upper part of which is housed in the upper mirror house (UMH).</p>

<p>Light from the fixed mirror travels down and is reflected through the primary camera lens (PCL) by means of the camera's primary mirror (PM). It is then projected forward to the photographed target (PT).</p>

<p>When in use, the light travels through a focus screen (FS) which can overlay a projeetive visual aid to assist the photographer in focussing the camera, example a split-prism screen. The camera is adjusted within the boundaries of the frame so projected and the shutter release is fired when the desired photograph is achieved.</p>

<p>With this concept, the primary mirror will travel upward. In this concept, this motion activates a electrical shut off micro switch (ESOMS) that serves to switch the projection unit off while the film back device (FBD) or sensor is being exposed to the light reflected off the subject so as to eliminate any risk of the projection light itself interfering or fogging the camera's proper operation. Returning the primary mirror to its original state resets the projector.</p>

<p>This concept also includes additions to the projector unit which are included in the inventory claims. The projector unit also houses exposure computation cells (ECEquip) at strategic points that feed to the projector central microprocessor unit (PCMPU). Compensated for the inherent light generated by the projector itself, the unit is enabled to take exposure readings of the subject. An incident light cell (ILC) can also be used to take similar readings and is interfaced similarly. An optical infrared focussing array (OIRFA) enables the projection of invisible infrared radiation through the system and is optically calibrated, by means of an internal lens set and the collimator to give annunciation when infrared return is at minimal dispersion i.e. at prime focus. The PCMPU can also control the projection of the concept's chief design advancement from a simple light is a multi raster scan laser array (RSLA). The RSLA is a high-speed, micro laser (or equivalent) array which serves to project a near holographic visual aid on the subject examples being crosshairs, exposure reading, framing and focussing aids. This system is powered by a powercell which can be designed to be removable and rechargeable and is embedded within the UMH.</p>

Claims (3)

1. <p>Claims 1. A viewfinder unit which can be attached to a camera which

   projects a view identical to the taking view of the relative image frame of the camera by utilising the existing minor and lens units of the existing camera, relying on no other projective ability (in comparison to patent US674 1809)
2. 2. A viewfinder unit according to claim I which can integrate an image focusing cue unit by means of an infra-red dispersal system.</p>

   <p>3. A viewfinder unit according to claim 1 which can integrate a holographic (laser or otherwise) raster scan system to provide a high-resolution targeting cue so as to aid the nature of projection as described in claim 1.</p>

   <p>4. A viewfinder unit according to claim I which can integrate direct and indirect light exposure reading equipment, the output of which can be displayed by equipment according to claim
3. 3.</p>

   <p>5. A viewfinder unit according to claim 1 that has the ability to be self-powered.</p>

   <p>6. A viewfinder according to claims 1, 2, 3, 4 and 5 which is fully integrated.</p>

   <p>7, A viewfinder unit according to claim 1 which has the ability to be shut off by an internal mechanism.</p>

   <p>8. A viewfinder unit according to claim 1, 2, 3, 4, 5, 6, 7 and 8 which can be subsequently utilised in any potential design of single-lens reflex camera (in comparison to patent EP1022608)</p>