EP1835223A1

EP1835223A1 - Light projector for dynamically changing the apparent shape of moving subjects

Info

Publication number: EP1835223A1
Application number: EP07005149A
Authority: EP
Inventors: Carlo Alberto Paterlini
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-03-16
Filing date: 2007-03-13
Publication date: 2007-09-19
Also published as: ITMN20060018A1

Abstract

A light projector for dynamically changing the apparent shape of moving subjects, comprising a light source (LA1, LF1, LF2) for lighting moving subjects. The particularity of the invention resides in that it comprises, between the light source (LA1, LF1, LF2) and the subjects, variation means (R2, DF1, SP1, TS1) for varying the space lit by each flash of light emitted toward the subjects with respect to the preceding flash of emitted light.

Description

The present invention relates to a light projector for dynamically changing the apparent shape of moving subjects.
As is known, lamps, generally of the xenon type, are already commercially available which, when triggered repetitively with a frequency which can vary from approximately 1 Hz to 15 Hz, allow to freeze the movements of moving subjects, so as to create particular effects.
These effects, commonly termed stroboscopic effects, arise from the fact that the duration of the light pulse of the lamps is on the order of a few tens of microseconds, and therefore any object, even if it is moving very rapidly, appears completely motionless to the human eye, as occurs for example in the case of the flash used for still cameras.
The rapid succession of these flashes yields a stepwise movement whose extent is inversely proportional to the scanning frequency used.
These solutions have been found to be improvable by providing a light projector which allows to change in practice dynamically the apparent shape of the moving subjects, where the term "subject" references any moving element which, by being lit in a particular manner, is "deformed" according to a logic criterion which can be changed in each instance, depending on the type of lighting that is used.
Within this aim, an object of the invention is to be able to vary within broad margins the type of effects that can be obtained.
Another object of the present invention is to provide a light projector for dynamically changing the apparent shape of moving subjects which, thanks to its particular constructive characteristics, is capable of giving the greatest assurances of reliability and safety in use.
Still another object of the present invention is to provide a light projector which can be obtained easily starting from commonly commercially available elements and materials and is also competitive from a merely economical standpoint.
This aim and these and other objects which will become better apparent hereinafter are achieved by a light projector for dynamically changing the apparent shape of moving subjects, according to the invention, which comprises a light source for lighting moving subjects, characterized in that it comprises, between said light source and said subjects, variation means for varying the space lit by each flash of light emitted toward said subjects with respect to the preceding flash of emitted light.
Further characteristics and advantages will become better apparent from the description of some preferred but not exclusive embodiments, illustrated by way of nonlimiting example in the accompanying drawings, wherein:

Figure 1 is a schematic view of the principle for dynamically changing the apparent shape;
Figure 2 is a schematic view of a projector with flash generation performed mechanically;
Figure 3 is a plan view of a rotating disk for creating a flash effect;
Figure 4 is a schematic plan view of a disk for producing an alternation of the lit regions;
Figure 5 is a view of a projector with the flash effect generated by means of the light source controlled by an optical sensor;
Figure 6 is a view of the alternation disk with the optical sensor applied thereto;
Figure 7 is a view of a light projector with two alternating light sources for creating the flash effect;
Figures 8 and 9 are views of a projector with two light sources which can be activated selectively to produce the alternation of the lit regions.

With reference to the figures, the light projector for dynamically changing the apparent shape of moving subjects is based on the criterion of emitting flashes, i.e., in practice, a luminous effect of extremely short duration, on the order of microseconds, so that the space is changed at each flash of emitted light, so that each successive flash does not light the space already lit by the preceding flash.
In practice, an alternation of images is provided which never light the space occupied by the preceding shape.
Considering by way of example the simplest solution, which projects flashes shaped like vertical bands, as shown schematically in Figure 1, the light source, which can be of any kind, emits vertical strips of light F1, F2, F3,... F7 and F8, which for example have identical dimensions.
At each successive flash, light and shadow are swapped; the repetition time between the various flashes is set to approximately 30 milliseconds.
The region a) of Figure 1 illustrates a rod T which is made to oscillate rapidly so as to assume the position shown in the region b) of Figure 1.
At the instant a), the rod T is lit by the flash in the regions F1, F3, F5, F7; after 30 milliseconds, the moving rod T is in the position of the region b) and is made visible by the subsequent flash, but this time the lit regions of the rod T are F2, F4, F6, F8.
It should be noted that the human eye has, in the central region of the retina, an image persistence of approximately 30-40 milliseconds, so that if the two images are viewed alternately at a frequency of 25 frames per second or more, the human eye perceives them as "continuous", i.e., seamless.
The way in which the human eye perceives the image of the moving rod T is the one shown in the region c) of Figure 1, so that the rod appears to be split in the points that coincide with the shapes of the flashes.
Moreover, by forcing a succession of the flashes of less than 50 milliseconds, the image is perceived in a "natural" manner, i.e., rather continuously, making the effect even more effective, differently from the traditional stroboscopic effect, which is typically jerky or stepwise.
Another variation is determined by the intrinsic duration of each flash.
In the example given earlier, an instantaneous light period of a few tens of microseconds has been assumed, but in practice, by increasing this period to a few milliseconds one obtains a softer effect, similar to a motion-blurred photograph.
With the solution described above, it can be said that the projector according to the invention, differently from any light effect created up to now, dynamically changes the apparent shape of the lit moving subjects, seen by a viewer and in real time.
The light projector according to the invention is therefore based on the use of flashes of light which can be obtained both by means of a mechanical action and by means of an electrical action.
Analyzing the embodiment shown in Figure 2, a light source LA1 is provided which can be constituted for example by a discharge lamp which is capable of emitting continuous light.
To create the emitted flashes of light, a first disk R1 is used which is provided with two mutually opposite openings AS 1 and AS2, which can have variable dimensions in order to vary the duration of the flashes.
The disk R1 is connected to a motor MR1, which turns the first disk R1 at a rate of for example 1000 rpm.
The motor MR1 that drives the first disk R1 can be connected directly to a second disk R2 which has, for example, 300 slits FT arranged radially, so that by producing a rotation which is 300 times slower than the rotation of the disk R1, at each half-tum of R1 the position of the slits of R2 is swapped with the position of the opaque regions, producing an alternation of light and shadow which is synchronized with the passage of the openings AS 1-AS2 in front of the beam of light.
The adjustable openings AS1, AS2 provided on the first disk R1 produce the sequence of flashes having a period of approximately 30 milliseconds.
It is further possible to provide a lens L1, with a suitable focal length, which transfers the image of R2 toward the moving subjects to be lit.
It should be noted that the final effect can produce just flashes with a minimum duration of a few milliseconds, and therefore the "deformation" of the moving subjects is softer than obtainable with flash effects having a shorter duration.
Considering for example what is shown in Figure 5, a light source LF1 is provided which is constituted for example by a xenon lamp which is triggered with very high voltage pulses to emit a flash which lasts 10-20 microseconds.
The sequential flashes must be synchronized with the movement of the slitted contour provided by the disk, which is again designated by R2.
To achieve synchronization, an optical sensor SO1 is used which is sensitive to the passage of opaque subjects which are interposed between it.
Such sensor is provided with an emitter LED and with a receiving photodiode, which face each other.
The disk R2, during its rotation, through its slits, which are for example 300 in number, interrupts or allows the passage only of the beam of light generated by the LED of SO1.
As shown in the drawing, the receiving photodiode of SO1 thus generates a square waveform, as shown in box DF1, and in particular it reflects the behavior of the passage of the slits during a rotation of R2.
At this point one can say that at each change of state of the square wave, the lamp LF 1 emits a flash, which is indicated in the lower part of box DF 1.
It should be noted that in order to change the repetition rate of the flashes it is sufficient to vary the rotation rate of the disk R2 by means of its control motor, designated by the reference sign M2.
A rotation of approximately 3 rpm generates 30 flashes per second, thus achieving the aim of the invention.
With reference to Figure 7, it is possible to achieve, without particular problems, the generation of 30 flashes per second.
In this case, in addition to the lamp LF 1 there is a second lamp LF2, so that the lamps provide two separate light sources which are advantageously both constituted by xenon lamps triggered by high-voltage pulses.
The beam of such lamps is conveyed in the correct and same direction through an optical prism PR1.
Differently from the example given previously, the signal generated by the optical sensor, again designated by SO1, is divided into two separate signals, as shown in box SP 1.
The second signal is simply formed by inverting the original signal.
By doing so, the 30 pulses per second required for correct operation of the invention are sent alternately to the two light sources LF1 and LF2, which thus receive only 15 pulses per second.
At this driving frequency, any xenon lamp is able to work correctly without any problem.
With reference to Figures 8 and 9, it is possible to use the two light sources, again designated by LF1 and LF2, which advantageously are xenon lamps triggered by very high voltage pulses (2-3 kV) and emit an intense but extremely short flash lasting 10-20 microseconds.
In this case, a simple astable multivibrator generates a pulse every 30 milliseconds.
With reference to box TS1, it can be seen that the pulses are distributed alternately toward LF1 and LF2, so that each lamp receives one pulse every 60 milliseconds.
This ensures an operating frequency for each lamp which is acceptable in terms of dissipation.
The lamps LF1 and LF2 are aligned and mutually opposite, and the light beams are sent to mirrors, designated by SP1 and SP2, which have mutually different inclinations, so as to divert the respective light beam upwardly, as shown in Figures 8 and 9.
Figure 8 illustrates the step in which the lamp LF 1 emits its flash.
It can be seen that the beam of light passes through the grating G1, splitting into many narrow beams, so that the regions designated by A1, A3, A5, A7, A9, A11 and A13 of the drawing are lit.
Figure 9 illustrates the next instant, in which the light source LF2 is activated and the mirror SP2 sends its flash, which through the grating G1 is split into many narrow beams constituted by the regions A2, A4, A6, A8, A10, A12 and A14, which in practice are alternated and complementary with respect to the preceding ones.
It is evident that the split beams of the instant shown in Figure 8 light regions which do not coincide, but indeed alternate with respect to those of the instant shown in Figure 9.
Finally, all the split beams, as they exit from the projector, light the subjects providing light and shadow, thus creating the effect sought by the invention.
In this example, the light exits directly without the aid of any lens, and therefore the size of the two sources on the corresponding mirrors determines only the distance of the subjects, the sharpness of the contours of the output images, and in particular, the more the source is pointlike, the more the contours of the subjects will be sharp.
From what has been described above it is therefore evident that the invention achieves the proposed aim and objects, and in particular the fact is stressed that a light projector is provided which, by alternating in practice the regions lit by the emitted flashes, allows to provide a particular and innovative effect which differs distinctly from the traditional stroboscopic effect.
Moreover, the alternation of lighting of spaces can be obtainable by using different colors, for example mutually complementary colors.
The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept.
All the details may further be replaced with other technically equivalent elements.
In practice, the materials used, so long as they are compatible with the specific use, as well as the contingent shapes and dimensions, may be changed according to requirements.
The disclosures in Italian Patent Application no. MN2006A000018 , from which this application claims priority, are incorporated herein by reference.
Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

A light projector for dynamically changing the apparent shape of moving subjects, comprising a light source for lighting moving subjects, characterized in that it comprises, between said light source and said subjects, variation means for varying the space lit by each flash of light emitted toward said subjects with respect to the preceding flash of emitted light.
The projector according to claim 1, characterized in that said variation means are of the mechanical type.
The projector according to the preceding claims, characterized in that said variation means of the mechanical type comprise, at a fixed light source, a first disk, with at least one opening, which is turned at a preset rate, and a second disk, with a plurality of radially arranged openings, which is turned at a rate which is correlated to the rotation rate of said first disk in order to position in succession said slits with respect to said at least one opening for the alternation of lights and shadows synchronized with the passage of said at least one opening.
The projector according to one or more of the preceding claims, characterized in that said openings have an extent which is adjustable in order to vary the duration of said flashes.
The projector according to one or more of the preceding claims, characterized in that it comprises a light source which is adapted to emit flashes with a preset duration toward said second disk provided with said slits, which can be detected by an optical sensor which drives said light source to emit flashes which are synchronized with the rotation of said second disk.
The projector according to one or more of the preceding claims, characterized in that it comprises a first light source and a second light source for the emission of flashes of emitted light toward said second disk with slits, said optical sensor being further provided for detecting said slits for the selective synchronization of the operation of said first and second light sources.
The projector according to one or more of the preceding claims, characterized in that it comprises a first light source and a second light source for the emission of a flash toward a respective mirror for redirection toward a grating with openings for producing single beams of light to illuminate in succession different regions of space with respect to the preceding flash.
The projector according to one or more of the preceding claims, characterized in that it comprises, downstream of said second disk, in the light propagation direction, a lens for concentrating the light beam.
The projector according to one or more of the preceding claims, characterized in that the space lit by one flash is complementary to the space lit by the preceding flash.