GB2454522A - Improved Camera Lucida - Google Patents

Abstract

Disclosed is a Camera Lucida which includes exchangeable partial mirrors (4) and exchangeable optical filters (5). The optical filters may also be hand held (6). The optical filter opacity may also be mechanically adjusted (fig. 5 and fig. 6). The optical filter opacity may also be electrically or electronically adjusted. A Camera Lucida is an optical device that can be used as a drawing aid, it is arranged so an image of the subject is superimposed, or overlaid, on the drawing paper or board when viewed by a user, the user can then trace the image and in doing so can paint, sketch, draw or otherwise reproduce the view subject.

Description

Intellectual D pr'oerty Oi,ice or Fe, CreaI'sdy ne InnovaIen Application No. GB0722 127.8 RTM Date:30 October 2008 The following terms are registered trademarks and should be read as such wherever they occur in this document: Velcro UK Inlelleclual Property Office is an operating name of The Patent Office 1.

Improved Camera Lucida This invention solves problems with conventional Camera Lucida's; and adds features.

A conventional camera Lucida does not have a way to easily adjust the brightness of the image of the subject in relation to the brightness of the drawing board or paper. Typically the user has to adjust the lighting of the subject, or the shade of the paper surface to be drawn on. White paper has particular problems in this regard.

To overcome this, the present invention proposes interchangeable partial mirrors and a variable, or interchangeable optical filter. This optical filter is either fixed to the device, or can be on a separate handle for ease of use.

The advantage of this is that the camera lucida can be used in a wide variety of lighting conditions, and the artist can draw on the surface of choice, including white paper.

Preferably, the partial mirrors are easily changed, by attaching to the optical housing with Velcro'; magnets; or similar.

Preferably, the optical filter has a variable polarised filter or utilises electric or electronically controlled electrochromic material or similar; (sometimes called smart glass').

An example of the invention will now be described by referring to the accompanying drawings.

A camera lucida is an optical device arranged so that the user can see an image of the subject in front of them overlaid on the drawing paper or board enabling accurate tracing' of the subject.

Fig 1 shows a typical camera lucida with optical housing Fig 2 shows the optical housing with attachments.

Fig 3 shows the hand held filter.

Fig 4 shows optical fittings in the optical housing.

Fig 5 shows possible assembly of a variable poiarising filter.

Fig 6 shows possible variable filter optical housing.

An optical housing (1) is attached to an adjustable arm (2) which in turn is attached or clamped to a drawing board (3) 2.

The optical housing (Fig 2) has an exchangeable partial mIrror (4); (a partial mirror reflects only a percentage of the light striking it). Two or more partial mirrors with differing properties are supplied.

The partial mirrors (4) are attached by Velcro' ; magnets or similar to facilitate easy changing.

Optical filter (5) is attached to optical housing (1) by Velcro'; magnets or similar to facilitate easy changing. Two or more optical filters (5) with differing properties are supplied.

Hand held filter (Fig 3) with handle (6) is an alternative way of utilismg filter (5). The user interposes this between bottom of optical housing (1) and drawing board (3); when required to assist viewing the virtual image.

Fig. 4 shows the path of light in the optical housing (I). Light from the subject to be drawn (a) passes through partial mirror (4) and is reflected by normal mirror (7). This image is reflected back to partial mirror (4) and up to viewing aperture (8). Light from drawing surface at (b) passes through filter (5) through partial mirror (4) to viewing aperture (8). This leads to subject and drawing surface to be visible to viewer simultaneously, correctly oriented at (c).

Fig. 5 shows a possible arrangement of circular polarised filters (9) and (10) top filter (9) has a small handle (11) attached.

Fig. 6 Shows details of polansed filters (9) and (10). Filter (10) is fixed, filter (9) can rotate. By rotating filter (9) with handle (11) the amount of light transmitted through the combined filters is varied.

An alternative method of varying the optical filter (5) would be by utilising electrochromic material or similar; (sometimes called smart glass'). This is adjusted by varying the amount of electricity passed through the material. 3.

Claims (3)

Claims.

1. A Camera Lucida with replaceable partial mirrors and optical filters.

2. A Camera Lucida as in claim 1 which has a mechanically variable optical filter.

3. A Camera lucida as in claim I which has an electrically or electronically variable optical filter.