JP2002149329A - Optical digitizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical digitizer where an image pickup means can sufficiently takes in reflected light even in the case that the distance between a detection unit and a retroreflection member is not sufficient in comparison with the distance between a light source and an image forming lens. SOLUTION: The optical digitizer which detects the pointed position coordinates of an indicator 2 on a detection face 1 is comprised of a light source 11 which emits light, a retroreflection member 22 which is provided in at least three sides of the periphery of the detection face 1 and retroreflects light emitted from the light source 11, the image pickup means which detects the direction of a shadow generated by interception of retroreflected light from the retroreflection member 22 by the indicator 2, and the image forming lens which forms an image of retroreflected light from the retroreflection member 22 on the image pickup means, and the light source 11 is arranged in the horizontal direction to the detection face and on the right or/and the left of the image forming lens 9 in the vicinity of the image forming lens 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-blocking type optical digitizer for detecting a pointing position coordinate of a pointer on a detection surface, and more particularly, to a light source in a horizontal direction with respect to the detection surface. The present invention relates to an optical digitizer located near a lateral side of an imaging lens.

[0002]

2. Description of the Related Art In recent years, an optical digitizer having more accurate detection capability has attracted attention instead of a resistive film type or electromagnetic induction type digitizer. FIG. 6 shows an example of a conventional optical digitizer. FIG. 6 is a schematic plan view of the optical digitizer. When a pen 2 serving as an indicator is placed on the detection surface 1, an indication is made based on the principle of triangulation by two detection units 3 provided above the detection surface 1. This is for detecting position coordinates. The detection unit 3 includes an imaging lens 9 provided on a front surface of a linear image sensor 13 serving as an imaging unit.
The light source 11 such as an LED is disposed on the left and right of the device. When there is nothing blocking light on the detection surface 1, the light from the detection unit 3 that has passed through the detection surface 1 and entered the retroreflective member 22 passes through the reverse optical path and is detected by the detection unit 3.
Come back to. When the pen 2 or the like is placed on the detection surface 1,
A part of the light path of the light is blocked, and the light does not return to the detection unit 3. Since the shadow portion can be imaged by the image sensor 13, the direction in which the light is blocked can be detected by detecting the direction of the shadow. That is, if the direction in which the pen 2 exists can be detected by the detection units 3 and 3 at two different known positions, the pointing position coordinates of the pen 2 can be calculated based on the principle of triangulation. Further, in the optical digitizer, since the detection surface 1 can be constituted by a transparent glass surface or the like, even if the LCD is arranged below the detection surface 1, the light attenuation is smaller than that of the resistance film type or the like. Since the number is small, it is possible to provide a brighter and better touch panel display device. Further, since the detection surface is a glass surface, unlike a resistance film method or the like, the detection surface is not broken by a sharp pen or the like.

[0003] Although the demand for a small touch panel for a portable terminal such as a PDA or a portable telephone is increasing, the advantages of the above-mentioned optical digitizer such that the light from the LCD is less attenuated and the detection surface is not broken. The demand for optical digitizers that can be used for these small liquid crystals is also increasing. Therefore, miniaturization, downsizing, power saving, and the like of the optical digitizer are desired.

In an optical digitizer, it is most preferable that the optical axis of the light source coincides with the optical axis of the imaging lens.
There is also a conventional example in which the optical axis is adjusted using a half mirror or the like.
In this case, since the light source must be disposed above or below the imaging lens, the detection unit becomes thick, which may be disadvantageous in reducing the size of the device.
Also, when a half mirror is used, the amount of light from the light source is attenuated to １ ／ due to reflection and transmission.
For this reason, it is necessary to use a light source having a higher output, which may be disadvantageous from the viewpoint of power consumption. Further, the high-output light source has a large physical size, which hinders miniaturization. Therefore, if the light sources 11 are arranged on the left and right sides of the imaging lens 9 as in the conventional example shown in FIG. 6, the detection unit 3 can be made thinner.

[0005] Here, the retroreflective member refers to a member having a reflection characteristic such that light incident thereon returns straight in the direction of incidence. As a typical retroreflective member, a retroreflective sheet in which a large number of small transparent glass beads are embedded, or a small corner cube prism arranged in an array can be used. Since their retroreflection characteristics are relatively excellent, most of the light incident thereon returns in the direction in which they are incident. Therefore, in the conventional example shown in FIG. 6, most of the reflected light of the light beam that has entered the retroreflective member 22 from the light source 11 returns to the light source 11, and a part of the reflected light is slightly shifted from the light source 11. 9 (more precisely, aperture 10). Therefore, in order to efficiently receive the light beam from the light source, it is necessary to bring the optical axis of the light source and the optical axis of the imaging lens as close as possible.

As means for bringing the optical axis of the light source and the optical axis of the imaging lens as close as possible, Japanese Patent Application No.
000-101831. This is, for example, by providing an imaging lens as a fan-shaped lens with a V-shaped cut so that the light incidence side is narrow and the imaging means side is wide, and the light source is provided close to the cut side plane. The aperture and the light source are made as close as possible.

[0007]

However, when a light source is arranged beside the imaging lens, it is desirable that the optical axis be as close as possible. Due to limitations such as the size of the lens, there is a limit in bringing the optical axis of the LED closer to the optical axis of the imaging lens. Therefore, when the distance between the detection unit 3 and the retroreflective member 22 is sufficiently large with respect to the distance between the light source 11 and the imaging lens 9 (correctly, the aperture 10), that is, the detection unit 3 has a relatively large detection surface. In the case of an optical digitizer, the imaging means 12 can sufficiently capture the reflected light even if the light source and the imaging lens are separated to some extent, but in the case of an optical digitizer having a relatively small detection surface, However, there is a limit to the distance between the light source and the imaging lens, and the reflected light from the retroreflective member returns to the light source but does not sufficiently enter the imaging lens. There was a problem that it was not possible to take in enough. If the reflected light cannot be taken in sufficiently, the shadow part of the pointer will not be clear, and the detection accuracy will also deteriorate.

Further, even if a fan-shaped imaging lens having a V-shaped cut is used, the optical axis shift at a level of several millimeters still occurs. Even if the deviation is a problem, the reflected light cannot be sufficiently taken into the imaging lens.

Therefore, as the detection surface becomes smaller, the reflected light does not sufficiently enter the imaging lens. Therefore, there is a limit to the reduction of the detection surface for application to a small LCD such as a portable terminal. there were. In addition, there is a problem that a light source having a high output must be used in order to sufficiently allow the reflected light to enter the imaging lens. In this case, there has been a problem from the viewpoint of power consumption. Further, even with an optical digitizer having a large detection surface, if the LED is physically large, the optical axis of the light source and the optical axis of the image forming lens are separated from each other.

The present invention has been made in view of the above circumstances, and has been developed in such a manner that even if the distance between the detection unit and the retroreflective member is not sufficiently large with respect to the distance between the light source and the imaging lens, the light is reflected by the imaging means. An object of the present invention is to provide an optical digitizer capable of sufficiently capturing light.

[0011]

In order to achieve the above-mentioned object of the present invention, an optical digitizer for detecting a pointing position coordinate of a pointer on a detection surface according to the present invention comprises: a light source for emitting a light beam; A retroreflective member provided at least on three sides around the detection surface and retroreflecting light rays emitted from the light source, and a direction of a shadow generated by the pointer blocking the retroreflected light from the retroreflective member. Imaging means for detecting, and an imaging lens for forming an image of the retroreflection light from the retroreflective member on the imaging means, the light source is in a horizontal direction with respect to the detection surface, and the In the lateral vicinity of the imaging lens, disposed on one of the left and right sides of the imaging lens, or on both sides so as to sandwich the imaging lens, further, the optical digitizer is a front surface of the retroreflective member Position and comprises a refractive scattering means for refracting scattered only in the horizontal direction and the reflected light from the incident light and the retroreflection member to the retroreflective member with respect to the detection surface.

Here, the refraction / scattering means may be a lenticular lens formed by arranging semi-cylindrical lenses in a one-dimensional array in the horizontal direction with respect to the detection surface.

Further, the refraction / scattering means may have a characteristic of a Fresnel beam splitter and a characteristic of a lenticular lens, and may be formed by a lens formed in a one-dimensional array in a horizontal direction with respect to the detection surface. .

Further, the refraction / scattering means and the retroreflective member may be an integrally molded product having a front surface formed by a lenticular lens and a rear surface formed by a corner cube prism array.

Further, the refraction / scattering means and the retroreflective member may be formed by a lens having a surface having both the characteristics of a Fresnel beam splitter and the characteristics of a lenticular lens, and the back surface may be formed by a corner cube prism array. .

Further, the optical digitizer according to the present invention may further include a display device for performing output display, and the display device may be arranged such that the detection surface and the display surface of the display device coincide with each other. .

According to the above-mentioned means, an effect is obtained that the light rays from the light source can be effectively guided to the image pickup means without being affected by the positional relationship between the light source, the imaging lens, and the retroreflective member. Accordingly, even if the optical axis of the light source and the optical axis of the imaging lens are slightly apart, the present invention can be applied to an optical digitizer having a small detection surface. Conversely, even in the case of an optical digitizer having a large detection surface, the present invention works effectively when the optical axis of the imaging lens is separated from the light source due to the use of a large LED or the like as the light source.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a preferred embodiment of the optical digitizer of the present invention. In the figure, portions denoted by the same reference numerals as those used in the conventional example represent the same components. The detection unit 3 has a configuration similar to that of the conventional example shown in FIG. Further, when the pointer 2 is placed on the detection surface 1, the process of detecting the coordinates of the indicated position is the same as in the related art. That is, when there is nothing blocking light on the detection surface 1, the detection unit 3 sends the detection surface 1
The light that has passed above and entered the retroreflective member 22 returns to the detection unit 3 through the opposite optical path. When the pen 2 or the like, which is an indicator, is placed on the detection surface 1, a part of the optical path of light is blocked, and the light does not return to the detection unit 3. The light receiving element 1 such as an image sensor of the detection unit 3
3 and the direction of the shadow is detected. This detection is performed by the detection units 3 and 3 at two different known positions, so that the coordinates of the indicated position of the indicator 2 are calculated based on the principle of triangulation.

As a feature of this embodiment, as shown in FIG. 1, a refraction / diffusion means 30 for refracting and diffusing a light beam in the horizontal direction with respect to the detection surface is provided on the front surface of the retroreflective member 22.
Is provided. As the refraction / diffusion means, for example, a lenticular lens is used. The lenticular lens 30 is formed by arranging an extremely thin and minute semi-cylindrical shape or a cylindrical lens optically equivalent thereto in a one-dimensional array, and refracts and diffuses light rays in the arranged direction. Refers to an optical lens having Due to the refraction and scattering characteristics, the light incident on the retroreflective member 22 and the light reflected therefrom are subjected to a refraction action according to the position (incident angle) of the light beam passing through the minute part of each cylindrical lens, and the entire array is captured. Are diffused in the direction in which they are arranged. Utilizing this feature, the lenticular lens 30 is connected to the retroreflective member 2 as shown in the drawing so that the light passing through the lenticular lens is refracted and scattered only in the horizontal direction with respect to the detection surface 1.
2 to the front.

Although FIG. 1 illustrates an example of a detection unit using two light sources, the present invention is not limited to this.
Of course, it is also possible to use one light source in order to realize an optical digitizer with lower power consumption. FIG. 2 is a schematic plan view of an optical digitizer according to the present invention using one light source for the detection unit. In the case of two light sources, the shadow seen from the light receiving element is the center of the indicator, but in the case of one light source, the light emitted from the light source 11 is blocked by the indicator 2 as shown in the figure. A difference occurs between the generated shadow and the original shadow which is a shadow as viewed from the light receiving element 13. If two shadows are formed, it is impossible to determine which is the original shadow. Therefore, the center between the shadow of the light source and the edge farthest from each of the original shadows is approximately processed as the center of the indicator 2. I do. By performing this processing by the left and right detection units 3 respectively, it is possible to approximately obtain the designated position coordinates of the pointer 2. By using one light source in this way, an optical digitizer with lower power consumption can be realized as compared with the case where two light sources are used.

The effect of the arrangement of the lenticular lens will be described with reference to FIG. FIG. 3A is a diagram for explaining a difference in light incident on the imaging lens depending on the distance between the retroreflective member and the detection unit, and a difference in light incident on the imaging lens depending on the presence or absence of the lenticular lens. FIG. 3B is a graph showing an illuminance value with respect to an observation angle. In FIG. 3A, the detection unit 3 has a long distance from the retroreflective member 22, and the detection unit 3 'has a short distance. Further, the reflected light from the retroreflective member 22 and the reflected light in the absence of the lenticular lens 30 is the reflected light 6, and the lenticular lens 30
The reflected light in the case where there is is the reflected light 7. For the sake of simplicity, it is shown that the detection unit and the retroreflective member face each other, and the light from the light source is incident on the retroreflective member at right angles. As can be seen from the figure, if the distance between the detection unit 3 and the retroreflective member 22 is long, the imaging lens 9 (more precisely, the diaphragm 10) can be used without the lenticular lens 30.
The reflected light 6 is incident on. However, as in the case of the detection unit 3 ′, as the distance from the retroreflective member becomes shorter, that is, as the detection surface becomes smaller, the imaging lens 9 (more precisely, the stop 1
0), the reflected light 6 does not enter. However, by arranging the lenticular lens 30 as the refraction / scattering means of the present invention on the front surface of the retroreflective member 22,
The light beam passing through the lenticular lens 30 is refracted and scattered in the horizontal direction with respect to the detection surface, and the light beam from the retroreflective member 22 spreads to the reflected light 7. Therefore, even when the distance between the retroreflective member and the detection unit is short,
Light from the light source can be efficiently guided to the imaging lens.

Further, even when the distance between the retroreflective member and the detection unit is long, when the distance between the light source and the imaging lens is large, for example, since the LED as the light source is large, it is necessary to approach the imaging lens. The lenticular lens works effectively even when there is a limit to the lens size. That is, it is possible to diffuse the reflected light in the horizontal direction so as to sufficiently enter the imaging lens. Therefore, a shadow portion generated when the pointer is placed on the detection surface becomes clear, and the detection accuracy of the pointer by the optical digitizer is increased.

As for the refraction / scattering means, it is of course possible to use a general diffuser or the like only for diffusing the incident light. Has spread to
Since the attenuation of the light returning to the detection unit is increased, a higher power light source must be used. Therefore, in order to efficiently perform refraction and scattering, it is desirable to use a unit that refracts and scatters only in the horizontal direction with respect to the detection surface, for example, the above-mentioned lenticular lens.

In the graph of FIG. 3B, the horizontal axis is the observation angle, and the vertical axis is the relative illuminance value of the reflected light at the position of the light receiving element. As can be seen from the graph, when there is no lenticular lens, the retroreflective member has a characteristic that the illuminance value sharply decreases as the observation angle increases. Specifically, it can be seen that the light incident on the imaging lens from the retroreflective member has such a characteristic that the illuminance value drops sharply when the observation angle is between 0 and 2 degrees. From this, it can be seen that when the imaging lens is slightly away from the light source, the amount of light incident on the imaging lens from the retroreflective member sharply decreases. Therefore, in the conventional optical digitizer, it is necessary to bring the light source and the imaging lens as close as possible, to use a light source of higher power, or to enlarge the detection surface. On the other hand, as can be seen from the graph, when the lenticular lens, which is a feature of the present invention, is located on the front surface of the retroreflective member, the illuminance value does not drop sharply and remains constant to some extent even when the observation angle is increased to some extent. Illuminance value is maintained. Specifically, the light incident on the imaging lens from the retroreflective member is
It can be seen that the characteristic is such that the illuminance value is kept almost constant when the observation angle is about 0 ° to about 2 °, and thereafter the illuminance value gradually decreases. That is, even if the imaging lens is separated from the light source to some extent, the light incident on the imaging lens from the retroreflective member does not decrease. Therefore, even if the light source and the imaging lens are separated to some extent, the retroreflected light will sufficiently enter the imaging lens, and even if the detection surface is made smaller and the detection unit and the retroreflection member are brought closer. ,
Since the observation angle can be increased to some extent, the retroreflected light sufficiently enters the imaging lens.

FIG. 4A is a partially enlarged view of the lenticular lens and the retroreflective member located around the detection surface as viewed from above. As shown, when a light beam from the light source enters the lenticular lens 30, it is first refracted in the horizontal direction (horizontal direction with respect to the detection surface) and then enters the retroreflective member 22. The retroreflective member is in the form of glass beads as shown in the figure, and the incident light returns inside the sphere after refraction. The optical path of the returning light ray is parallel to the optical path of the incident light ray, but is a separate optical path. Since the position of incidence on the lenticular lens differs as shown in the figure, the optical path of the refracted light ray there Is not parallel to the optical path of the light beam from the light source, but is refracted laterally and follows another optical path. By this effect, it is possible to diffuse the retroreflected light in the horizontal direction with respect to the detection surface. Note that the pitch of the lenticular lens 30 may be selected so that interference fringes (moire) do not appear in consideration of the pitch of the glass beads of the retroreflective member 22. Further, the greater the curvature of the lenticular lens 30, the greater the effect of diffusing the incident light in the horizontal direction. Therefore, the size of the detection surface, that is, the distance between the detection unit and the retroreflective member, or the connection with the light source. A curvature that efficiently diffuses may be selected according to the distance from the image lens.

Incidentally, the retroreflective member does not have perfect retroreflective characteristics, and therefore has poor retroreflective characteristics with respect to light incident at a shallow angle (large incident angle). Therefore, the angle of incidence of light incident on the retroreflective member farthest from the detection unit, ie, near the corner of the detection surface, becomes the largest, and the retroreflected light from around the corner becomes weak. Therefore, if an attempt is made to detect the pointer using the retroreflected light in the vicinity, the difference between the shadow portion and the retroreflected light portion is reduced, and the detection sensitivity is reduced. Therefore, by using the characteristics of the Fresnel beam splitter to refract incident light incident at a shallow angle so as to impinge on the retroreflective member at a deep angle, the corners where the amount of retroreflected light decreases. Also, it is possible to obtain good retroreflection light. In addition, the Fresnel beam splitter is formed by engraving a large number of parallel opposing small surfaces having the same angle. Thus, when light enters the retroreflective member near the diagonal of the detection unit, the incident light incident at a shallow angle is refracted by the Fresnel beam splitter and enters the retroreflective member at a deep angle. Therefore, excellent retroreflection light can be obtained even at a corner where the amount of retroreflection light has been reduced due to incidence at a shallow angle. These are as shown in Japanese Patent Application No. 2000-106063 by the present applicant.

FIG. 4B shows a lens having both the characteristics of the lenticular lens shown in FIG. 4A and the characteristics of the Fresnel beam splitter described above. As shown in the figure, this lens has a characteristic that a small surface (shown by a dotted line) of a Fresnel beam splitter has a curvature like a lenticular lens and is diffused in a horizontal direction with respect to a detection surface. It is a thing. By doing so, even when the detection surface is small, that is, the distance between the detection unit and the retroreflective member is short, and the distance between the light source and the imaging lens is long, the light beam from the light source is effectively used. Good retroreflected light that enters the imaging lens and is also obtained at the corners of the detection surface can be obtained.

Next, still another embodiment of the optical digitizer according to the present invention will be described with reference to FIG. In the present embodiment, a lenticular lens as a refracting and scattering means and a corner cube prism array as a retroreflective member are integrally formed. That is, as shown in FIG.
The surface on the side close to the lenticular lens surface is the detection surface 1
The surface farther from the surface is defined as a corner cube prism array surface. The integrally molded lens can be manufactured from plastic or the like. Here, as shown in FIG. 5B, the corner cube prism array is such that a plurality of very small corner cube prisms are arranged in an array, and the incident light is accurately reflected in the incident direction. It has characteristics. By integrally molding the refraction / scattering means and the retroreflective member in this manner, the same effects as those not obtained by the above-described integral molding can be obtained. It is also possible to manufacture an optical digitizer at a lower cost. Although a lenticular lens is shown as the refraction / scattering means, it is of course possible to use a lens having both the characteristics of a lenticular lens and the characteristics of a Fresnel beam splitter as shown in FIG. .

It should be noted that the optical digitizer of the present invention is not limited to the illustrated example described above, and it is needless to say that various changes can be made without departing from the spirit of the present invention.

Further, the optical digitizer according to the present invention is advantageous for miniaturization, so that it can be applied to a PDA, a touch pad of a notebook computer, and the like, and a display device such as an LCD is provided on the back surface. As a matter of course, it is of course possible to provide a display-integrated touch panel in which the display surface and the detection surface are arranged so as to coincide with each other.

[0031]

As described above, according to the optical digitizer of the present invention, the light beam from the light source can be effectively imaged without being affected by the positional relationship between the light source, the imaging lens, and the retroreflective member. An excellent effect of being able to be guided can be achieved. Further, by integrally molding the retroreflective member and the refraction / scattering means, it is possible to realize an optical digitizer which is easy to manufacture and inexpensive.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of an optical digitizer according to the present invention.

FIG. 2 is a schematic plan view of another optical digitizer according to the present invention.

FIG. 3 is a diagram for explaining the effect of the lenticular lens of the optical digitizer according to the present invention;
FIG. 7A is a diagram for explaining a difference in light incident on the imaging lens depending on a distance between the retroreflective member and the detection unit, and a difference in light incident on the imaging lens depending on the presence or absence of the lenticular lens. FIG. 3B is a graph showing the illuminance value with respect to the observation angle.

FIG. 4 is a partially enlarged view of a refraction / scattering unit and a retroreflective member. FIG. 4 (a) is a diagram showing a refraction characteristic of light incident on a lenticular lens, and FIG. FIG. 3 is a diagram illustrating a refraction characteristic of incident light of a lens having both characteristics of a lenticular lens and a Fresnel beam splitter.

FIG. 5 (a) is a schematic plan view of an integrally molded lenticular lens as a refraction / scattering unit and a corner cube prism array as a retroreflective member, and FIG. 5 (b) is a corner cube. It is a figure for explaining a prism array.

FIG. 6 is a schematic plan view of a conventional optical digitizer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Detection surface 2 Indicator 3 Detection unit 6 Reflected light in the absence of a lenticular lens 7 Reflected light in the presence of a lenticular lens 9 Imaging lens 10 Aperture 11 Light source 13 Image sensor 22 Retroreflective member 30 Lenticular lens

Claims (6)

[Claims] 1. An optical digitizer for detecting a pointing position coordinate of a pointer on a detection surface, wherein the optical digitizer is provided on at least three sides of a periphery of the detection surface. A retroreflective member that retroreflects a light beam emitted from a light source; an imaging unit configured to detect a direction of a shadow generated by the pointer blocking the retroreflected light from the retroreflective member; and the retroreflective member. An image forming lens for forming an image of the retroreflected light from the imaging means on the image pickup means, wherein the light source is in a horizontal direction with respect to the detection surface and in the lateral vicinity of the image forming lens, and Either the left or right of the image lens, or disposed on both sides so as to sandwich the imaging lens, further, the optical digitizer is located in front of the retroreflective member, and the incident light to the retroreflective member and An optical digitizer, comprising: a refraction / scattering unit for refracting / scattering light reflected from the retroreflection member only in a horizontal direction with respect to the detection surface. 2. The optical digitizer according to claim 1, wherein said refracting and scattering means comprises a lenticular lens formed by arranging a semi-cylindrical lens in a one-dimensional array in a horizontal direction with respect to said detection surface. An optical digitizer characterized by becoming. 3. The optical digitizer according to claim 1, wherein said refraction / scattering means has both a characteristic of a Fresnel beam splitter and a characteristic of a lenticular lens, and a one-dimensional array in a horizontal direction with respect to said detection surface. An optical digitizer comprising a lens formed in a matrix. 4. The optical digitizer according to claim 2, wherein said refraction / scattering means and said retroreflective member are integrally formed such that a front surface is formed by a lenticular lens and a back surface is formed by a corner cube prism array. An optical digitizer characterized by being an object. 5. The optical digitizer according to claim 3, wherein the refraction / scattering means and the retroreflective member are formed of lenses whose surfaces have both the characteristics of a Fresnel beam splitter and the characteristics of a lenticular lens. An optical digitizer characterized in that the back surface is an integrally molded product formed by a corner cube prism array. 6. The optical digitizer according to claim 1, further comprising a display device for performing an output display, wherein the display device includes the detection surface and the display device. An optical digitizer, which is arranged so as to coincide with a display surface.