GB2445386A

GB2445386A - Digital camera with flip down sensor

Info

Publication number: GB2445386A
Application number: GB0700015A
Authority: GB
Inventors: Terence Edward Weston
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-01-02
Filing date: 2007-01-02
Publication date: 2008-07-09
Also published as: GB0700015D0

Abstract

A digital camera 101 having a single axis straight through light path 103 to the viewfinder 105 has a hinged sensor 104 that is held clear of the light path until an image is captured when it drops down into the light path. The sensor may be held in an intermediate position not normal to the axis so that converging verticals may be corrected, or it may slide into position.

Description

2445386

Background to the invention

Single Lens Reflex (SLR) cameras are well known and used by professional and serious amateur photographers. The basic principle of operation is to use a mirror and 5 prism to project an image formed by the camera's lens system onto a viewing screen. The photographer uses the viewing screen to adjust focus and compose the image to be recorded. At the time the image is to be recorded, the mirror is flipped or moved away from the optical axis of the lens system to allow the image to be focussed onto a film or electronic sensor, and thus be recorded. The other main components of the 10 camera are the shutter and iris diaphragm. The advantages of SLR cameras include being able to "see" via the mirror and prism directly through the lens at the subject to be photographed, avoiding the parallax error that would otherwise occur if the viewing screen was not on the same axis as the lens. It also allows interchangeable lenses, filters, attachment to microscopes, telescopes and other instruments, whilst 15 allowing the exact view through the lens that will be focussed onto the sensor or film.

There are drawbacks however: the complexity of the optical components and mechanism for diverting the image onto the viewing screen results in higher cost ami greater size and weight. Furthermore, there is significant vibration caused when the mirror is flipped out of the optical pathway at the instant of taking the photograph, 20 and this results in a blurred image. For high quality photographs, it is necessary to lock the mirror out of the optical path before opening the shutter, thus avoiding mirror vibration. Some attempt were made to overcome this problem by partly silvering the mirror, so that some of the incoming light went to the viewer, and some to the film plane. These so-called pellicle cameras suffered from problems such as reduced light 25 availability for the film and the viewfinder, light scatter within the camera, and the need to keep the mirror very clean (dust on the mirror would be imaged onto the film).

The present invention seeks to overcome the drawbacks of SLR cameras by taking advantage of sensors used in the newer, so-called digital cameras, whereby the 30 traditional film is replaced by an electronic sensor. The sensor converts incoming light into electrical signals which are then processed and stored in digital form on a variety of media. In the original film cameras, it would have been extremely difficult i

to move the film away from the optical centre to allow the photographer to see directly through the lens - hence the mirror and prism solution. Digital SLR cameras have continued to use the mirror and prism principle.

My invention is to eliminate the mirror and prism, and instead, cause the sensor to 5 move, as follows. In the pre-recording mode, (that is, when the photographer is focussing and composing the image) the sensor is located away from the optical axis, so that the image is viewed directly through the lens, without the intervention of a prism and mirror. When the image is to be recorded, the sensor is caused to move into the optical axis at the image plane, so that the image is focussed thereon. Almost 10 simultaneously, the iris shutter and timing shutter operate to ensure the correct exposure as determined by the photographer. After the image is recorded, the sensor returns to the original positioa Thus there is no requirement for a mirror an prism. The low mass of the sensor permits the operation of a solenoid, electric motor, piezoelectric motor or other motors, including springs and spring-powered motors. The 15 electrical signal connections to the sensor may be made by flexible low-mass cable. Alternatively, the signal may be transmitted to the processor by wireless means.

Other benefits are that the movement of the sensor would be much quieter than that caused by moving the mirror, and the elimination of components in the optical path required for the viewing screen will result in less distortion and a brighter image on 20 the screen. Additionally, the camera would be smaller, lighter, and more cost-

effective. Conceptually, because the camera according to the present invention may be very much smaller than the traditional SLR, the camera will be attached to a lens, rather than the lens being attached to the camera.

The mass of the sensor is lower than many mirrors, and therefore any vibration caused 25 by its movement will be of high frequency and very short duration. However, damping means may be incorporated for very critical applications.

Description of the invention.

In a first preferred embodiment, there is provided a camera having a moveable sensor, 30 the sensor hinged so that it may be swung in to or out of the optical pathway, The movement may be caused by a solenoid or other electric motor, or clockwork.

2_

In a second preferred embodiment, there is provided a camera having a moveable sensor, whereby the sensor moves in a linear track to alternately intercept or avoid the image formed by a lens. The movement may be caused by a solenoid or other electric motor, or clockwork. This embodiment is not described in detail.

5 The first embodiment will now be described by reference to the following drawings.

Figure 1 is a schematic showing the light path through a typical modern SLR camera before taking the photograph.

Figure 2 is similar to figure 1, but shows the instant of taking the photograph

Figure 3 is a schematic showing a camera incorporating the present invention, before 10 taking the photograph, and figure 4 shows the same camera at the instant of taking the photograph.

In order to avoid unnecessary complicated drawings, the figures show simplified lenses - in typical cameras, there are many lenses combined to reduce chromatic aberration and other distortions, nor are the shutter and diaphragm shown. These are 15 fundamental components of all cameras, and well-known in the art. As a result, the light path is shown as a single line.

Referring to figure 1, the camera bodyl has a lens 2 which accepts incoming rays of light 3. The light passes through the lens 2 and is reflected by the mirror 4 so that it passes through and is refracted by the penta-prism S. The light 3 eventually passes 20 through the eyepiece 6 so that the user can see the object to be photographed. The light 3 may be focussed onto a screen so that the eyepiece 6 is focussed onto the screen. Typical screens may have data projected thereon referring to the camera settings, so that the user is better informed as to the conditions affecting the photograph before taking it. At the instant of taking the photograph, the mirror 4, 25. which may be hinged at A, is caused to swing out of the path of the light 3, so that the light 3 is focussed onto the film 7. After the photograph has been taken, the mirror 4 swings back to the position shown in figure 1, enabling another photograph to be taken. This is a broad description of a typical SLR camera, and such cameras have many additional features which are not shown.

30 Referring to figure 3, this shows a camera according to the present invention, with a body 101, wherein the light 103 passes through the lens 102 and straight through the eyepiece 105. Of course, there may be a screen in the light path, so that the viewer

sees the subject to be photographed focussed on the screen, as previously described At the instant of taking the photograph, the sensor 104, which is shown held out of the light path3 in figure 3, is caused to swing on pivot A into the position shown in figure 4. The light 3 thus fells on the sensor for the time predetermined by the shutter action, and the sensor 104 swings back out of the light path 3 to enable another photograph to be taken.

Figures 3 and 4 show a simple hinged sensor 104, but the sensor may be moved linearly in a slide for example, and achieve the same result. The choice of moving path and motive power will be dictated by the internal arrangement of the other components of the camera.

The signal generated as the result of the image falling on the sensor may be transmitted to the processing means by wire or by wireless means, or optical means-

Further benefits may be obtained if the sensor 104 is able to be stopped at a position other than normal to the light path, so that "converging verticals" may be corrected in architectural photographs.

Claims

A digital camera having an image sensor which is held clear of the light emitted by the subject to be photographed, and may be moved into the light path to sense the image.

A digital camera as in claim 1 wherein the image sensor is hinged.

A digital camera as in claim 1 wherein the image sensor is moved linearly.

A digital camera as in any preceding claim wherein the image sensor may be held in an intermediate sensing position with the sensor plane not normal to the axis of the image.

A digital camera as in any preceding claim where the viewing lens is substantially on the optical axis, so that he image of the subject passes directly through the objective lens and through the eyepiece lens.

A digital camera according to any preceding claim wherein the signal generated by the image falling on the sensor is transmitted to signal processing means by wire.

A digital camera according to any preceding claim wherein the signal generated by the image falling on the sensor is transmitted to signal processing means by wireless means.

A digital camera according to any preceding claim wherein the signal generated by the image falling on the sensor is transmitted to signal processing means by optical means.