GB1592789A - Display apparatus - Google Patents

Description

PATENTS ACT 1949 SPECIFICATION NO 1592789 In pursuance of Section 8 of the Patents Act, 1949, the Specification has been amended in the following manner : Page l, delete 14 to 18 insert According to the invention display apparatus comprises a row of discrete light sources, a refractive prism for imaging the light sources, means for rotating the prism so that the images of the light sources are repetitively caused to trace parallel lines, and control means for controlling operation of the individual light sources to produce a desired visual display, said control means comprising means for selectively producing energisation signals for the light sources; gating means, conditioned by the energisation signals and through which those signals are supplied to the light sources; encoder means for producing signals indicative of the rotational position of the prism; and means for deriving from the rotational position signals gating signals for gating the energisation signals to the light sources, said gating signals being spaced non-uniformly so as to compensate for the non-linear relationship between the displacement of the virtual source and the rotational position of the prism so that the images trace the image lines at a substantially uniform speed.

Page 5, delete lines 12 to 29 insert 1. Display apparatus comprising a row of discrete light sources, a refractive prism for imaging the light sources, means for rotating the prism so that the images of the light sources are repetitively caused to trace parallel lines, and control means for controlling operation of the individual light sources to produce a desired visual display, said control means comprising means for selectively producing energisation signals for the light sources; gating means, conditioned by the energisation signals and through which those signals are supplied to the light sources; encoder means for produc- ing signals indicative of the rotational position of the prism; and means for deriving from the rotational position signals gating signals for gating the energisation signals to the light sources, said gating signals being spaced non-uniformly so as to compensate for the non-linear relationship between the displacement of the virtual source and the rotational position of the prism so that the images trace the image lines at a substantially uniform speed.

2. Display apparatus as claimed in claim 1, in which the encoder means comprise a timing disc driven in synchronism with the prism and carrying markings at non-uniform intervals corresponding to the non-uniform spacings of the required gating signals and a pulse generator for generating a succession of timing pulses respectively occurring at times related to the instants at which the mark ings pass a datum position.

3. Display apparatus as claimed in claim 2, in which the means for selectively producing energisation signals for the light sources comprise a counter incremented by the gating signals and a store addressed by predetermined counts of the counter and storing a digital representation of the matter to be displayed.

4. Display apparatus substantially as described with reference to the drawings.

(54) DISPLAY APPARATUS (71) We, INTERNATIONAL BUSINESS MACHINES CORPORATION, a Corporation organized and existing under the laws of the State of New York in the United States of America, of Armonk, New York 10504, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the mathod by which it is to be performed, to be particularly described in and by the following statement :- This invention relates to display apparatus.

In constructing displays there has been a tradeoff between costly high detail arrays wherein a separate light source is provided for each point and the use of a single line of light sources and a uniformly and continuously rotating mirror which, while it reduces the number of light sources needed, results in distortion from the rotating mirror which gives a concave appearance and a narrowness of the display field which limits the height of the object displayed.

According to the invention display apparatus includes a light source, a refractive prism, means for imparting relative motion between the light source and the refractive prism whereby the image of the source is repetitively caused to trace a line, and means for controlling operation of the light source whereby a desired visual pattern is displayed.

The invention will further be explained by way of example with reference to the accompanying drawings, in which: Fig. I is a functional schematic diagram of the relationship of an observer to the elements of the invention.

Figs. 2A, B and C are an illustration of the inter-relation of motion with switching"off'and"on"of the source in producing the appearance of light segments.

Fig. 3 is a schematic view of a rotating prism embodiment of the invention.

Fig. 4 is a schematic diagram of the relative timing employed in connection with Fig. 3.

Fig. 5 is a schematic diagram of the wiring involved in Fig. 3.

The invention employs the image retentive capacity of the human eye, the ability to rapidly turn on and off certain types of light sources and relative motion to provide to the human eye the appearance of a two-dimensional image. This is accomplished by providing motion in one dimension to the light from a light source that can be turned"off'and"on"rapidly and then turning the light off and on selectively during the motion cycle. The result is that a point of light traverses the appearance of a line and the line in turn is broken up into selectable segments.

Where a series of small light sources are positioned in a line orthogonal to the motion direction and then the lights are coordinated in their"on"and"off'times, a two-dimensional image will be displayed.

Referring to Fig. I there is shown a schematic of the elements of the invention.

In Fig. I a light source I is supplied with power so that it can be selectively interrupted through a control element 2. The light from the source) is caused to have the appearance to an observer 3 of moving linearly by the introduction of motion through element 4. Element 4 may be motion apparatus applied directly to the source itself, or in instances where it is desirable to have the light source stationary, the element 4 is a refractive member than bends the light beam so that when the refractive member goes through a motion cycle the source I appears to the observer 3 to traverse a line. A modulating means 5 is provided to corrclate the time"on"and"off"of the source I with the position of the motion cycle. The result is the capability to produce the appearance of selectively displayed segments of a line. the segments may be made to appear smaller and smallcr by shortening the relationship of the"on"and"ofr'times to the cycle of the motion.

The light source must be susceptible to being tumed"on"and-offl'with little afterglow so that only parts of the motion cycle can be illuminated and it should be physically small enough to pack in a line or in a quasi linear array that looks reasonably continuous. For example, a zig-zag line. A solid state light source such as a light emitting diode or electroluminescent device meets these criteria.

Referring next to Fig. 2 the role of a refractive member in the motion is illustrated in greater detail. Figs. 2A and 2B illustrate the operation of a prism 6 with the parallel faces. Fig. 2A shows three typical light rays Rl, R and R3 which are emitted from point source 7 and refracted at the left surface of prism 6 according to Snell's Laws of Optics. They traverse the prism and exit at the right face where they are again refracted. Each ray leaves with its original direction but displaced as shown. The emerging rays appear to originate at point 8 as iHustratcd by the dashed lines. Thus, the source will appear to observer 3 as a virtual image located at position 8. Although we have illustrated the optics with a point source, the method is correct for an extended source which may be considered to be made up of many point sources.

Fig. 2B illustrates the situation with the prism rotated about the axis 9 in Figs.

2A and 2B. The virtual image is now located at 8', which is seen to be displaced from the previous position. The latter is shown as point 8 in Fig. 2B for comparison.

The displacement is primarily in the vertical direction, the horizontal displacement being small in comparison for practical values of the refractive index. Equation I (below) gives the vertical displacement of image 8 with practical accuracy when the observer is located at a distance from the scanner which is large in comparison with the dimensions of the latter. Thus, turning the source at 7"on"and"off"as illustrated by the sequence of 3 pulses in Fig. 2C will produce the sequence of three line segments illustrated in that figure.

Some flexibility is available in the selection of the refractive member. It is necessary only that there be two sides with a geometric relationship such that there be a displacement of a beam of light passing in one and out the other. For a given overall diagonal dimension, a four-sided prism will provide the largest display field with the field becoming smaller as the number of prism sides increases.

It should also be noted that where rotation is used for the motion, the position of points in the line of the apparent image does not vary linearly with respect to degrees of rotation and hence provision must be made for this fact in the"on"and "off"switching of the light source.

Referring next to Fig. 3 a view is shown of a rotating light emitting diode display embodiment of the invention. The display is made up of an array of light emitting diode light sources IRA-IN mounted in closely adjacent relationship in a Ime. The solid state light emitting diode has a number of avantages as a light source in that it is sufficiently small that a number can be packed closely together thereby yielding better detail in the horizontal dimension of the display. The light emitting diode device also has the property that the transition from"off'to"on" and from"on"to"off'is very close to instantaneous. This quality permits greater detail in the vertical dimension of the display. The motion is provided by rotation of a four-sided refractive prism 6 wherein each beam of light from each light emitting diode lA-IN is caused to appear to the observer 3 as a line and that line can be interrupted. An example illustration is provided in the form of five light emitting diodes which produce the appearance of the alphabetic character Y.

In order to correlate the rotational motion with the light interruption it is necessary to provide a series of signals non-uniformly spaced in time as light passes through each face in turn. The rotation of the member 6 displaces the apparent location of the elements IA-IN in the vertical direction according to the relationship of Equation 1, when the entrance and exit faces are parallel. apparent that various extensions are possible in the light of the principles set forth.

For example, by such means as linear motion of light source or by appropriate choice of angle of prism faces with respect to axis of rotation of the refractor it is possible to have light sources appear as segments in several lines.

What has been described is a technique for imparting motion to the light from a single, small, rapid"ofF'and"on"response, light source to provide the appearance to an observer of a line of light, modulating"ofr'and"on"periods of the light source with the motion to produce the appearance of line of light segments and coordinating the output of a series of such light sources mounted in a line orthogonal to the line of motion to produce a display.

Claims (8)

1. WHAT WE CLAIM IS :- 1. Display apparatus including a light source, refractive prism, means for imparting relative motion between the light source and the refractive prism whereby the image of the source is repetitively caused to trace a line, and means for controlling operation of the light source whereby a desired visual pattern is displayed.
2. 2. Apparatus as claimed in claim 1, wherein the relative motion is imparted by motion of the refractive prism.
3. 3. Apparatus as claimed in claim 2, wherein the motion of the refractive prism is rotational.
4. 4. Apparatus as claimed in claim 3, wherein the rotational motion is oscillatory.
5. 5. Apparatus as claimed in any one of the preceding claims, wherein the light source is a point source.
6. 6. Apparatus as claimed in any one of claims I to 4, wherein the light source is a row of point sources.
7. 7. Apparatus as claimed in any one of claims) to 6, wherein the refractive prism is a square prism.
8. 8. Display apparatus substantially as described with reference to the drawings.