WO2002001321A2

WO2002001321A2 - Method of calibrating the physical pixel size of a display monitor

Info

Publication number: WO2002001321A2
Application number: PCT/US2001/020436
Authority: WO
Inventors: Kiesel Richard; K. Maloney Robert; Rubin David
Original assignee: Visionrx, Inc.
Priority date: 2000-06-27
Filing date: 2001-06-27
Publication date: 2002-01-03
Also published as: WO2002001321A3

Abstract

The present invention is a method for calibrating the physical pixel size of a display monitor (152). The physical pixel size calibration is based on the pixel size of a calibration window (170) with respect to an external object of known dimensions provided by the user, such as a 3.5' diskette, CD jewel case or dollar bill. In the preferred embodiment, the user holds a selected external object up against the calibration window, and then resizes the calibration window to the physical size of the external object. Physical pixel size is calculated on the basis of the known physical dimensions of the external object, and the pixel size coordinates of the boundaries of the resized calibration window.

Description

METHOD OF CALIBRATING THE PHYSICAL PIXEL SIZE OF A DISPLAY MONITOR

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to co-pending application

U.S. Serial No. 09/425,065, entitled "Interactive Method and

System For Attracting and Targeting Prospective Clients In The

Medical Care Field," filed October 21, 1999, which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the field of computer display systems and, more particularly, to a method for calibrating the physical pixel size of a display monitor used in conducting eye examinations over an Internet web site.

BACKGROUND OF THE INVENTION

In the above identified co-pending application, an interactive method and system is disclosed for medical care providers, namely eye care providers, to more effectively target and attract prospective clients by, among other things, affording them eye examinations over an Internet web site. To conduct such an examination, stimuli of different shape, size, speed, frequency, location, color, contrast and/or intensity are displayed on the user's display monitor. One of the most important factors, however, is the physical pixel size of the display monitor. This is so, because when conducting an eye examination, stimuli of a known dimension or size must be displayed to the observer to test for specific visual deficiencies. However, display monitors are not of the same size, varying, for example, from 13" to 21". Nor, are they are of the same resolution setting. Thus, without calibration, stimuli of the same pixel size are, however, of a different physical size. For example, a stimulus on a display monitor at a resolution of 640 x 480 may have a vertical size of about 4 cm, whereas on a the same display monitor at a resolution of 1024 x 768, it is only about 2.4 cm.

Accordingly, it would be desirable to have a method for readily calibrating the physical pixel size of a display monitor, particularly for conducting eye examinations, wherein stimuli of a known dimension or size are displayed to an observer.

SUMMARY OF THE INVENTION

The present invention provides a method for calibrating the physical pixel size of a display monitor. The physical pixel size calibration is based on the pixel size of a calibration window with respect to an external object of known dimensions provided by the user, such as a 3.5" diskette, CD jewel case, or US dollar bill.

In a preferred embodiment, the user holds a selected external object up against the calibration window, and then resizes the calibration window to the physical size of the external object. To resize the calibration window, a mouse pointer is moved over a point (xPι,yPι) on a horizontal boundary of the calibration window until the pointer is displayed as a two-headed arrow, and then "dragged" while depressing the mouse button to a new point (xpι,yp₂), such that the corresponding inner part of the calibration window is the same size as the selected external object along the y-axis. Similarly, the mouse pointer is next moved onto a point (xp₃,yp₃) over a vertical boundary of the window, and then dragged to a new point (xp₄,yp₃), again such that the corresponding inner part of the window again is the same size as the external object along the x-axis. Physical pixel size is then calculated on the basis of the known physical dimensions of the external object, and the pixel coordinates of the boundaries of the resized calibration window. In this manner, objects can be displayed on the monitor by scaling the objects on the basis of the calculated physical pixel size such that the displayed object has the desired physical dimensions .

BRIEF DESCRIPTION OF THE DRAWINGS The features and advantages of the present invention will become more readily apparent from the following detailed description of the invention in which like elements are labeled similarly and in which:

Fig. 1 is a schematic block diagram of an integrated telecommunication system capable of conducting eye examinations over the Internet, useful for illustrating the present calibration method of the present invention;

Fig. 2 is an enlarged depiction of the display monitor of Fig. 1;

Fig. 3 is an exemplary depiction of the primary window associated with the calibration program of the present invention;

Fig. 4 is an exemplary depiction of a calibration window displayed over a portion of the primary window;

Fig. 5 is a depiction of the resized calibration window, with the pixel coordinates of the boundaries thereof;

Fig. 6 is a depiction of a stimulus illustrated using normalized world coordinates; and Fig. 7 is a depiction of the mapping of a stimulus defined using normalized world coordinates into the pixel coordinate system of the display monitor of Fig. 2. DETAILED DESCRIPTION

The present invention provides a method for calibrating the physical pixel size of a display monitor, particularly useful when conducting eye examinations over the Internet, as embodied in the system of Fig. 1, referred herein to as the VisionRx system. However, although the present invention is embodied for use with the VisionRx system, it should be clearly understood, that the present invention is also applicable for use with other systems and application programs wherein an important factor is calibrating the physical pixel size of the display monitor.

Referring to Fig. 1, there is shown - in schematic block diagram - the Vision Rx system 100, including an integrated telecommunication network 105, such as the Internet. Users connect to the Vision Rx system 100 through the use of a modem 110 or network interface card 115 installed in their personal computer 120. Any standard browser 125, such as the Netscape Navigator or Microsoft Internet Explorer, can be used to remotely access Vision Rx web site 130 established by Vision Rx server (s) 135. Web site 130 preferably includes the use of text, digital images, audio and/or video, developed using conventional software tools and languages, such as C++, Java and/or HTML, among others.

To effect user interaction, a user input device, such as a mouse 140, or keyboard 145 can be used, to respond to the observed test stimuli. Various computerized eye examinations are provided to the user using web browser 125, including, for example, unaided visual acuity tests; corrected visual acuity tests; contrast sensitivity tests; color vision tests; visual field tests; and neurologic tests, among others. Such computerized eye examinations can be readily stored as portable software modules 150, such as Java applets, and then downloaded and executed locally on user's personal computer 120, or, alternatively, executed on a computer or computers located at a central facility. Each Vision Rx software module 150 tests for a desired visual deficiency by displaying to the user test objects and stimuli of different shape, size, speed, frequency, location, color, contrast and/or intensity on a display monitor 152, and then by recording and comparing what the user reports seeing with what is presented by the computer.

Such stimuli are represented by pixels and are sent from a video controller (not shown) within computer 120 to display monitor 152 having a viewable area 155 representing the surface where the pixels are output, as illustrates in Fig 2. Viewable area 155 is defined using pixel coordinates (xp,yp), ranging from (0,0) at the lower left corner to (xp_raax, yp_raax) at the upper right corner. The actual display format of the stimuli, however, is controlled by the graphical user interface (GUI) of the operating system, such as the Microsoft Windows 95 operating system. When conducting an eye examination, stimuli of a known physical size must be displayed to the observer on viewable area 155, with its position defined in terms of pixel coordinates. As indicated above, without calibration, stimuli of the same pixel size, will be of a different physical size due to the varying physical size of the display monitors, and its current resolution setting.

The present invention affords a method for readily calibrating the current physical pixel size of display monitor 152. Incorporated into software modules 150 is a calibration program 160 for determining the physical pixel size of the display monitor. When the user indicates via keyboard 145 or mouse 140 that an eye examination is to be performed, the operating system executes calibration program 160 to determine the physical pixel size of the display monitor. As will be discussed herein below, the calibration program determines physical pixel size based on the pixel size of a calibration window with respect to an external object of known dimensions provided by the user, such as a 3.5" diskette, CD jewel case or US dollar bill. Software modules 150 then displays test objects and stimuli based on the physical pixel size calculated by calibration program 160.

Computer 120 is understood to execute calibration program 160 so as to provide a primary window 165 within viewable area 155 in which information associated therewith is displayed and which window is operative to receive commands, such as by pointing, clicking, or selecting. This window mechanism is readily employed in programs running under Microsoft Windows operating system available from Microsoft Corporation, Redmond, Washington. A similar X-windows mechanism is also available in the Macintosh operating system available from Apple Computer, Inc. Shown in Fig. 3 is primary window 165 accessed through web site 130, which contains the title, menu bar and tool bars related to the window, along with instructions informing the user on how to perform the calibration. Preferably, primary window 165 is the full size of viewable area 155, with a minimum supported resolution of 800 x 600.

Referring to primary window 165, a user places an "insert point" before the Dollar Bill, 3.5" Diskette or CD Jewel Case to select which external object will be used in the calibration process. After making the selection, the user then clicks on the box labeled Adjust, which then causes a calibration window 170 of predetermined pixel size (x_cw pixels by y_cw pixels) to be displayed over a subarea of primary window 165, as illustrated in Fig. 4. Associated with calibration window 170 is a resizing program 175 concurrently executed that allows a user to interactively resize the calibration window using the operations of the mouse pointer. Note that calibration window 170 is substantially smaller than primary window 165, and includes instructions for resizing calibration window 170 to match the physical size of the selected external object by either increasing or decreasing its size, as explained below.

In accordance with the principles of the invention, the user holds the selected external object, e.g., a 3.5" diskette, up against calibration window 170. Referring to Fig. 5, to resize calibration window 170, the mouse pointer is moved over a point (xpι,y ι) on a horizontal boundary 175 of calibration window 170 until the pointer is displayed as a two-headed arrow, and then "dragged" while depressing the mouse button to a new point (xpι,yp₂), such that the corresponding inner part of the calibration window is the same size as the selected external object. Similarly, the mouse pointer is next moved onto a point (xp₃,yp₃) over a vertical boundary 180 of the window, and then dragged to a new point (xp₄,yp₃), again such that the corresponding inner part of the window again is the same size as the external object. Clicking on the box labeled Done terminates resizing program 175, and also removes calibration window 170 from viewable area 155.

The coordinates (xp_x,yp_x), (xp_x,yp₂), (xp₃,yp₃), and (xp₄,yp₃) - expressed in terms of pixel coordinates - are passed from the operating system to resizing program 175 during the mouse pointer operations, specifically, the "drag" function. Note that these pixel coordinates are illustrated in Fig. 5. Also, recall that the pixel coordinates, ranging from (0,0) to

(^χP_maf yPmax) ' define a point on the viewable area of the monitor. Importantly, the physical pixel size can now be readily calculated on the basis of the known physical dimensions of the external object, and the pixel coordinates of the points (xp_x, yp_x) , (xp_x, yp₂) , (xp₃, yp₃) , and (xp₄,yp₃). More particularly, the horizontal physical pixel size (H_PIXEL) and the vertical physical pixel size (V_PIXEL) , expressed in unit length per pixel (e.g., inches per pixel), are given as follows:

V SIZE V PIXEL = y_cw + yp₂ -yp₁

H PIXEL = ^{H SIZE} x_cw + xp. -xp^

where V_SIZE and H_SIZE are the known vertical and horizontal dimensions of the selected external object, respectively, expressed in terms of unit length, e.g., inches, centimeters, millimeters, etc. It is noteworthy that y_cw + yp₂-ypι and x_cw + xp₄-xp₃ are the vertical and horizontal pixel size of the calibration window, respectively.

The results of the above calibration process can be readily transferred to the Vision Rx system using, for example, TCP/IP protocols, along with any other desired user information. Alternatively, since the pixel coordinates of the boundaries of the resized calibration window are known, the physical horizontal pixel size (H_PIXEL) and the physical vertical pixel size (V_PIXEL) can also be expressed as follows:

V _{PIXEL =} -Σ IZE yp₅ - yp₉

H PIXEL = -^^IZE xp, - xp.

where yp₅ is the y pixel coordinate of a point (xp₅,yp₅) on the other horizontal boundary 185 of the resized calibration window, and xp₆ is the x pixel coordinate of a point (xp₆,yp₆) on the other vertical boundary 190 of the resized calibration window, as illustrated in Fig. 5. In this latter case, however, yp₅ - yp₂ and xp₆ - xp₄ are the vertical and horizontal pixel size of the calibration window, respectively.

Recall that each Vision Rx software module 150 tests for a desired visual deficiency by displaying to the user test stimuli of a precise known size. The desired stimuli, such as a character (E) 177, can be defined within a normalized Cartesian coordinate system (xw,yw) , known as normalized world coordinates (in the range of 0 to 1) , as illustrated in Fig. 6. Mapping these world coordinates into the pixel coordinates (xp,yp) of the display monitor requires scaling the stimuli to a desired physical size. Fig. 7 illustrates the mapping of character 177 from the normalized world coordinates to the pixel coordinates of viewable area 155. On the basis of pixel size, a stimulus of normalized world coordinates ∑(xw₁,yw₁), such as character 177, can be displayed on the monitor with the desired physical dimensions of x__size x y_size by a scaling transformation that multiples the normalized world coordinates (xw^y j by the scaling factors sx and sy to produce the transformed pixel coordinates (xp^yp :

xp =xw -sx

where _x_size sx = H PIXEL xwmax ~x^■"^■w"mm

y_s±ze sy V_PIXEL

^■* max J mir and xw_raax - xw_mιn , and yw_max-yw_mιn are the maximum width and length of the stimulus or character 177, respectively.

Of course, stimuli can be displayed on the monitor at different positions by adding appropriate translation distances to the original pixel coordinates so as to move the stimuli to a position (xp',yp'). Also, various other transformation mechanisms can be used for mapping the stimuli within viewable area 155, such as rotation, scaling transformation using a fixed-point position, and clipping, among others. Such transformation mechanisms are discussed in, for example, in Hearn et al., Computer Graphics, Prentice Hall (1997). Note that in performing such transformation mechanisms, the stimuli must be likewise scaled on the basis of the determined pixel size to maintain the desired physical dimensions on the viewable area of the display monitor.

Accordingly, the present invention provides a method for calibrating the pixel size of a display monitor, particularly useful when conducting eye examinations over the Internet.

Although, the method is embodied in a system employing the

World Wide Web, the present calibration method is also equally applicable for use in computerized eye examinations conducted on stand alone personal computers. As such, the embodiment discussed herein above is merely illustrative of the principles of the invention. Various modifications will become apparent to those skilled in the art from the foregoing description and accompanying figures. Such modifications are intended to fall within the scope of appended claims.

Claims

CLAIMS :

1. In a computer system having a user input device and a display monitor having a viewable area representing the surface where the pixels are output, a method for calibrating the physical pixel size of the display monitor, comprising the steps of: displaying a calibration window within a region of the viewable area; selecting an external object of known physical dimensions; holding the external object against the calibration window; in response to commands received through the user input device, resizing the calibration window to be the same physical size as the external object; and calculating the physical pixel ^■ size of the display monitor on the basis of the pixel dimensions of the resized calibration window, and the physical dimensions of the external object.

2. The method of claim 1 wherein said calibration window comprises an active window of an application program for displaying information and/or receiving user commands through the user input device for resizing the calibration window.

3. The method of claim 1 further including a primary window comprising an active window of an application program for displaying information and/or receiving user commands through the user input device for calibrating the physical pixel size of the display monitor.

4. The method claim 3 wherein the calibration window is displayed within an area of the primary window.

5. The method of claim 1 wherein said step of resizing includes dragging a horizontal boundary and a vertical boundary of the calibration window for the calibration window to match the physical dimensions of the external object.

6. The method of claim 1 wherein the steps of displaying, selecting, resizing and calculating are conducted over the Internet .

7. The method of claim 1 further comprising the step of calculating the pixel coordinates of selected points on a horizontal boundary and on a vertical boundary of the resized calibration window, wherein the pixel size of the resized calibration window is calculated from the pixel coordinates of the selected points.

8. The method of claim 1 further comprising the step of displaying predetermined objects of a desired physical dimension on the viewable area of the display monitor on the basis of the calculated physical pixel size of the display monitor.

9. The method claim 1 wherein the predetermined objects are defined in normalized world coordinates.

10. The method of claim 9 further comprising the step of mapping the normalized world coordinates of the predetermined objects into pixel coordinates of the viewable area.

11. The method of claim 10 wherein the step of mapping includes scaling the normalized world coordinates on the basis of the calculated physical pixel size of the display monitor such that the predetermined objects have a desired physical dimension.

12. The method of claim 1 wherein the physical pixel size of the display monitor is along two directions.

13. In a computer system having a user input device and a display monitor having a viewable area representing the surface where the pixels are output, a method for calibrating the physical pixel size of the display monitor, comprising the steps of: displaying a calibration window within a region of the viewable area, said calibration window having a pixel dimension of x_cw horizontal pixels by y_cw vertical pixels; selecting an external object of known physical dimensions, said external object having physical dimensions of H_SIZE x V_SIZE; holding the external object against the calibration window; in response to commands received through the user input device, dragging a point (xpχ,ypι) on a horizontal boundary of the calibration window to a new point (xPι,yp₂) such that the corresponding inner part of the calibration window is the same physical size as the external object, and then dragging a point (xp₃,yp₃) on a vertical boundary of the calibration window to a new point (xp₄,yp₃) such that the corresponding inner part of the calibration window is the same physical size as the external object; and calculating the physical pixel size of the display monitor on the basis of the pixel dimensions of the resized calibration window, and the physical dimensions of the external object.

14. The method of claim 13 wherein the physical horizontal pixel size (H_PIXEL) and the physical vertical pixel size (V_PIXEL) of the display monitor are given as follows : V PIXEL = ^{V SIZE} y_cw + yp₂-yp_x

H PIXEL = ^{H SIZE} x_cw + xp₄~xp₃ o

where y_cw + yp₂-yp_ι and x_cw + xp₄-xp₃ are the vertical and horizontal pixel size of the calibration window, respectively.

0 15. The method of claim 13 wherein the physical horizontal pixel size (H_PIXEL) and the physical vertical pixel size (V_PIXEL) are given as follows:

V PIXEL = ^V-^SIZE yp^ - yp₉ 5

H PIXEL = ^H-^SIZ£ ^χPz xp.

where yp₅ is the y pixel coordinate of a point (xp₅,yp₅) on the 0 other horizontal boundary of the resized calibration window, and xp₆ is the x pixel coordinate of a point (xp₆,yp₆) on the other vertical boundary of the resized calibration window, and Y ₅ ^~ YP₂ ^and xp₆ - xp₄ are the vertical and horizontal pixel size of the calibration window, respectively. 5

16. The method of claim 13 wherein said calibration window comprises an active window of an application program for displaying information and/or receiving user commands through the user input device for resizing the calibration 0 window.

17. The method of claim 13 further including a primary window comprising an active window of application program for displaying information and/or receiving user commands through the user input device for calibrating the physical pixel size of the display monitor.

18. The method of claim 17 wherein the calibration window is displayed within an area of the primary window.

19. The method of claim 13 wherein the steps of displaying, selecting, dragging and calculating are conducted over the Internet.

20. The method of claim 13 further comprising the step of displaying on the viewable area of the display monitor a predetermined object of physical dimensions x_size x y_size on the basis of the calculated physical pixel size of the display monitor.

21. The method claim 20 wherein the predetermined object is defined in normalized world coordinates ∑(xw_i,yw_i) having a horizontal and vertical pixel size of xw_max - xw_rain , and yw_max- yw_min, respectively.

22. The method of 21 wherein the pixel coordinates ^∑(^χPiΛYPi) of the predetermined object on the viewable area are given by: xp .=xw.-sx

yp_±=yw.-sy wherein the scaling factors sx and sy are given by:

x size

H PIXEL sx = ■ = xw max -xw mm .

y_sιze _{sy =} V = PIXEL γw max - ^Jγw mi .n