[go: up one dir, main page]

WO2015088468A1 - Dispositif pour représentation d'informations visuelles - Google Patents

Dispositif pour représentation d'informations visuelles Download PDF

Info

Publication number
WO2015088468A1
WO2015088468A1 PCT/UA2014/000116 UA2014000116W WO2015088468A1 WO 2015088468 A1 WO2015088468 A1 WO 2015088468A1 UA 2014000116 W UA2014000116 W UA 2014000116W WO 2015088468 A1 WO2015088468 A1 WO 2015088468A1
Authority
WO
WIPO (PCT)
Prior art keywords
eye
representation
visual information
points
revolution
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/UA2014/000116
Other languages
English (en)
Inventor
Mykhailo MOSKALENKO
Galyna POTAPOVA
Olav SANDNES
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of WO2015088468A1 publication Critical patent/WO2015088468A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01—Head-up displays
    • G02B27/0101—Head-up displays characterised by optical features
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/02—Catoptric systems, e.g. image erecting and reversing system
    • G02B17/06—Catoptric systems, e.g. image erecting and reversing system using mirrors only, i.e. having only one curved mirror
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01—Head-up displays
    • G02B27/017—Head mounted
    • G02B27/0172—Head mounted characterised by optical features
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01—Head-up displays
    • G02B27/0101—Head-up displays characterised by optical features
    • G02B2027/0123—Head-up displays characterised by optical features comprising devices increasing the field of view
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09B—EDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
    • G09B9/00—Simulators for teaching or training purposes
    • G09B9/02—Simulators for teaching or training purposes for teaching control of vehicles or other craft
    • G09B9/08—Simulators for teaching or training purposes for teaching control of vehicles or other craft for teaching control of aircraft, e.g. Link trainer
    • G09B9/30—Simulation of view from aircraft
    • G09B9/32—Simulation of view from aircraft by projected image
    • G09B9/326—Simulation of view from aircraft by projected image the image being transformed by optical means

Definitions

  • the invention relates to devices for representation of visual information, mainly glasses virtual or augmented reality, or to on-helmet devices for representation of visual information.
  • a known device for representation of visual information currently in use in visualization systems of flight simulators featuring collimated image contains a spherical screen and a spherical mirror (refer, e.g., to Barry G. Blundell, 3D Displays and Spatial Interaction, Vol. I, ISBN: 978-0-473- 17702-7, « WALKER & WOOD», 2010).
  • Drawbacks of the known device for representation of visual information are the dependence of the formed observer's notion of his/her spatial position on the position of the observer's pupils of the eyes, because of the dependence of the observed image geometry on the location of the observation point, and the fact that the specified collimation of the observed image in such a device may be obtained solely for a single observation point.
  • a device for representation of visual information that is closest to the hereby claimed device for representation of visual information is the device containing a screen the diffusing surface of which is a surface of revolution, and a mirror the reflecting surface of which is a surface of revolution (refer, e.g., to Potapova G. K. and Moskalenko M. A., Correction of Geometrical Distortions of Images in Visualization Systems of Flight Simulators, Proceedings of the 7 th International Conference Applied Optics - 2006, Vol. 3. Computer Technologies in Optics. S. -Petersburg, 2006, p.p. 127- 132).
  • Said device for representation of visual information functions in the following manner.
  • a primary optical image is generated in some way or another, this primary optical image being the visual information subject to be transmitted as image to be perceived by the observer.
  • This image may be generated by means of direct or reciprocal projection of the respective image onto the screen. Beams emerging from points of the primary optical image are reflected by concave reflecting surface of the mirror and are reaching the observer's pupils of the eyes. At that, an image forms at the observer' s eye retinae, this image matching the primary optical image at the surface of the screen that reflects diffusively.
  • Drawbacks of the above-described known device for representation of visual information are the insufficient accuracy of the formed observer's notion of his/her spatial position, and the fact that in such a device, the specified collimation of the observed image can only be obtained for a single point of observation.
  • the purpose of the present invention is to provide a device for representation of visual information with enhanced accuracy of the formed observer's
  • the screen surface is a surface of revolution the axis of which coincides with the reflecting surface's revolution axis, while the generatrix thereof is a curve that approximates points, which optically conjugate with specified points of the meridional cross-section of the image observed by the eye.
  • the mirror is executed in a manner to be one-sidedly transparent in the direction towards the pupil of the eye.
  • a second identical device for representation of visual information Added to the device for representation of visual information is a second identical device for representation of visual information, in such a manner that optical surfaces of their elements are symmetrical to each other relative to the plane of symmetry of the observer's eyes.
  • the cause of the dependence of the observed image geometry on the location of the observer's pupils of the eyes in the prototype is that shifting of the observer's pupil of the eye in relation to its nominal position causes the distortion of the observed image geometry (refer to Aerospace Systems for Monitoring and Control: Materials of the VI International Scientific and Technical Conference "AVIA-2004”. - Vol. 2.-K. : NAU, 2004, p.p. 23-54, Fig. 2 - 5).
  • the reflecting surface of the mirror and the surface of the screen are executed as surfaces of revolution with common axis that passes through the center of revolution of the eye
  • the configuration of the device for representation of visual information's optical system in relation to pupils does not change, and therefore, both the collimation and the geometry of the image observed by the eye, are kept unchanged.
  • this feature serves to assure higher accuracy of the formed observer's notion of his/her spatial position and the specified collimation of the observed image, at least in the process of horizontal shifting of the observer's pupil (pupils) of the eye (eyes).
  • Fig. 1 shows a layout drawing of the invention: the monocular device for representation of visual information: the virtual reality for the left eye, according to claim 1 of the formula of the invention.
  • the device features screen 1 and spherical mirror 2. Reflecting surface 3 of mirror 2 is generated by revolution of circular arc 4 round vertical axis 5 that passes through the center of revolution 6 of eye 7. Within the field of vision 8, image 9 observed by eye 7 is determined by the aggregate of points thereof ⁇ P'i ⁇ .
  • Fig. 1 one of the specified points ⁇ ', ⁇ is shown: the central point 10 of image 9 observed by eye 7. Point 10 optically conjugates with point 1 1 .
  • Point 1 1 is determined as the point of convergence of bundle of beams 12 reflected by surface 3 of mirror 2 (in reciprocal direction) that emerge from pupil 1 3 of eye 7 and are directed towards point 10.
  • Point 1 1 is the preimage of point 10.
  • All points ⁇ Pi ⁇ optically conjugated with specified points [P'i] of image 9 observed by eye 7, are determined.
  • Points ⁇ Pi ⁇ are preimages of the respective points ⁇ P'i ⁇ .
  • Diffusing surface 14 of screen 1 is the surface that approximates points ⁇ Pi ⁇ optically conjugated with specified points ⁇ P'i ⁇ of image 9 observed by eye 7.
  • Fig. 2 shows a layout drawing of monocular device for representation of visual information: the virtual reality for the left eye, according to claim 2 of the formula of the invention. It features screen l and spherical mirror 2.
  • Reflecting surface 3 of mirror 2 is generated by revolution of circular arc 4 round vertical axis 5 that passes through the center of revolution 6 of eye 7.
  • image 9 observed by eye 7 is determined by the aggregate of points ⁇ P ⁇ of its meridional cross-section 1 5.
  • three of the specified points ⁇ P ⁇ are shown: central point 1 0 and extreme points 16 and 17 of the meridional cross-section 15 of image 9 observed by eye 7.
  • Points 1 0, 16 and 17 optically conjugate with points 1 1 , 1 8 and 19, respectively.
  • Points 1 1 , 18 and 19 are determined as the points of convergence of bundles of beams 12, 20 and 21 reflected by surface 3 of mirror 2 (in reciprocal direction) that emerge from pupil 13 of eye 7 and are directed towards points 10, 1 6 and 17, respectively.
  • Points 1 1 , 18 and 19 are the preimages of points 10, 16 and 17, respectively.
  • Points ⁇ Pj ⁇ optically conjugated with specified points ⁇ P ⁇ of meridional cross-section 1 5 of image 9 observed by eye 7, are determined.
  • Points ⁇ Pj ⁇ are preimages of the respective points ⁇ P' j ⁇ .
  • Diffusing surface 22 of screen 1 is the surface of revolution the axis of which coincides with the axis 5 of revolution of the reflecting surface 3 of mirror 2.
  • Generatrix 23 of diffusing surface 22 of screen 1 is a curve, in this particular case, a circular arc with center in point 24, that approximates points ⁇ Pj ⁇ optically conjugated with specified points ⁇ P'j ⁇ of meridional cross-section 1 5 of image 9 observed by eye 7.
  • Fig. 3 shows a layout drawing (top view) of binocular device for representation of visual information: virtual or augmented reality, according to claim 4 of the formula of the invention. It features two monocular devices for representation 25 and 26 for the left and right eyes, respectively.
  • the monocular device 25 for representation of visual information features screen 1 with diffusing surface 22 and mirror 2 with reflecting surface 3.
  • the monocular device for representation 26 features screen 27 with diffusing surface 28 and mirror 29 with reflecting surface 30.
  • Diffusing surfaces 22 and 28 of the screens and reflecting surfaces 3 and 30 of mirrors 2 and 29, are pairwise symmetrical in relation to planes of symmetry 3 1 of the observer's eyes 7 and 32. Plane 3 1 passes through the median point of the line segment linking centers of revolution 6 and 33 of the observer's left and right eyes, and is perpendicular to said line segment.
  • each of mirrors 2 and 29 can be made both transparent and non-transparent in the direction towards pupils 13 and 34 of a left-eyed and right-eyed observer.
  • the device for representation of visual information the mirrors 2 and 29 of which are executed as non-transparent in the direction towards pupils 13 and 34, can be used as a binocular device for representation of virtual reality.
  • the device for representation featuring even one of the mirrors 2 or 29 executed to be transparent in the direction towards the respective pupil can be used as a device for representation of augmented reality.
  • a primary optical image is formed by whatever method.
  • screen 1 can be a screen of direct (or reciprocal) projection, a non-flat liquid-crystal display. Beams from the primary. optical image at the diffusing surface 14 of screen 1 , reach the reflecting surface 3 of mirror 2, are reflected by it, and reach pupil 1 3 of the observer's eye 7.
  • Coordinates of any of the points ⁇ Pi ⁇ can be calculated, e.g., as coordinates of intersection point (in general case, convergence point) of two beams reflected by surface 3 of reflecting mirror 2, these beams emerging from the upper and lower edges of pupil 13 of the observer's eye 7 and directed to the respective point among the specified points ⁇ P'i ⁇ of image 9 observed by eye 7.
  • the number of specified points ⁇ />', ⁇ may vary depending on the required accuracy of collimation of image 9 observed by eye 7. For example, calculations of coordinates of 25 points ⁇ Pi ⁇ optically conjugated with 25 points ⁇ P'i ⁇ of image 9 observed by eye 7, at a spherical surface 100 meters in diameter, with center in the center of revolution 6 of eye 7, with the 0.072 meter diameter of the reflecting spherical surface 3 of mirror 2, the center of which is located 0.033 meter above the center of revolution 6 of eye 7, yield the following results: 0.04119 0.04104 0.04107 0.04128 0.04166
  • X, Y, and Z are the coordinates of the right-hand rectangular system of coordinates, with axes X and Z located in the plane of symmetry of the observer's eyes, with horizontal position of axis Z in the direction of view, axis X directed up, and axis Y directed horizontally from left to right.
  • the diffusing surface 14 of screen 1 described by an equation obtained with polynomial interpolation, passes precisely via points used in the interpolation, the virtual image in mirror 2, based on the principle of reciprocity of geometrical optics, will be perceived at the specified distance.
  • the diffusing surface 1 4 of screen 1 may be spherical.
  • the device for representation of visual information functions in a manner similar to that of the device for representation of visual information in the configuration shown in Fig. 1.
  • the generatrix 23 of the diffusing surface 22 of screen 1 is a plane curve that approximates points ⁇ Pj ⁇ (including points 1 1 , 18 and 19) optically conjugated with the specified points ⁇ Pj ⁇ (including with points 10, 16 and 17) of the meridional cross-section 1 5 of image 9 observed by eye 7.
  • each of the points ⁇ Pj ⁇ of generatrix 23 of the diffusing surface 22 is determined as the convergence point of the bundle of beams (in reciprocal direction) reflected by reflecting surface 3 of mirror 2 that emerge from pupil 1 3 of eye 7 and are directed towards the respective point ⁇ P'j ⁇ of the meridional cross-section 15 of image 9 observed by eye 7.
  • points 1 1 , 18 and 19 are optically conjugated with points 1 0, 1 6 and 17 of the meridional cross-section 15 of image 9 observed by eye.
  • Diffusing surface 22 of screen 1 is executed as the surface of revolution of the generatrix 23 round the axis 5 of revolution of the reflecting surface 3 of mirror 2.
  • the device for representation of visual information according to claim 3 of the formula of this invention functions in a manner similar to that of the device for representation of visual information in the configurations shown in Fig. 1 and 2, differing in that, additionally, beams from the surrounding space of objects within the field of vision 8 pass through mirror 2 which is made one-sidedly transparent in the direction towards pupil 1 3, and reach pupil 13 of the observer's eye 7. At that, the observer sees in mirror 2 not just the virtual image of the primary optical image at the diffusing surface 14 or 22 of screen 1 , but also the real image of surrounding objects within the field of vision 8.
  • the device for representation of visual information according to claim 3 of the formula of this invention is a monocular device for representation of augmented reality.
  • the device for representation of visual information 26 added to the device for representation of visual information 25, functions in exactly the same manner as the device for representation of visual information 25, the only difference being that it generates image of virtual or augmented reality for the observer's another eye, the right eye 32.
  • the cause-and-effect relation between the aggregate of the substantial features of the proposed technical solution and the achieved technical result consists in the following.
  • the cause of the dependence of the observed image geometry on the location of the observer's pupils of the eyes in the prototype is that shifting of the observer's pupil of the eye in relation to its nominal position causes a distortion of the observed image geometry (refer to Potapova G. K. and Moskalenko M. A., Correction of Geometrical Distortions of Images in Visualization Systems of Flight Simulators, Proceedings of the 7 International Conference Applied Optics - 2006, Vol. 3. Computer Technologies in Optics. S. -Petersburg, 2006, p.p. 127- 132).
  • the reflecting surface of the mirror and the surface of the screen are executed as surfaces of revolution with common axis that passes through the center of revolution of the eye, when the pupil moves, at least, in the plane of vision (when the pupil revolves around the common axis of the reflecting mirror and the screen surface), the configuration of the device for representation of visual information's optical system in relation to pupils does not change, and therefore, both the collimation and the geometry of the image observed by the eye, are preserved unchanged. That is why, owing to the reduction of the dependence of the observed image geometry on the position of the observer's pupil (pupils) of the eye (eyes), the observer can have more precise perception of his/her spatial position.
  • the invention may be used in devices for representation of visual information, mainly glasses virtual or augmented reality, or to on-helmet devices for repre ' sentation of visual information.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)

Abstract

Dans le dispositif de la présente invention pour représentation d'informations visuelles contenant un écran et un miroir, dont la surface réfléchissante est une surface de révolution, selon la présente invention, l'axe de révolution de la surface réfléchissante de miroir passe par le centre de révolution de l'œil, et la surface d'écran est une surface qui approxime des points qui sont optiquement conjugués à des points spécifiés de l'image observée par l'œil. Ceci étant, la surface d'écran est une surface de révolution dont l'axe coïncide avec l'axe de révolution de surface réfléchissante, alors que la génératrice associée est une courbe qui approxime des points, qui se conjuguent optiquement à des points spécifiés de la section transversale méridionale de l'image observée par l'œil. De plus, le miroir est mis en œuvre de manière à être transparent d'un côté dans la direction vers la pupille de l'œil. Un second dispositif identique pour représentation d'informations visuelles est ajouté au dispositif pour représentation d'informations visuelles, d'une telle manière que des surfaces optiques de leurs éléments sont symétriques les unes aux autres par rapport au plan de symétrie des yeux de l'observateur.
PCT/UA2014/000116 2013-12-09 2014-10-23 Dispositif pour représentation d'informations visuelles Ceased WO2015088468A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
UA2013014413 2013-12-09
UAA201314413 2013-12-09

Publications (1)

Publication Number Publication Date
WO2015088468A1 true WO2015088468A1 (fr) 2015-06-18

Family

ID=52007254

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/UA2014/000116 Ceased WO2015088468A1 (fr) 2013-12-09 2014-10-23 Dispositif pour représentation d'informations visuelles

Country Status (1)

Country Link
WO (1) WO2015088468A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110308560A (zh) * 2019-07-03 2019-10-08 南京玛克威信息科技有限公司 Vr设备的控制方法
US10782453B2 (en) 2015-01-21 2020-09-22 Tesseland, Llc Display devices with reflectors

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3784742A (en) * 1971-05-12 1974-01-08 Redifon Ltd Ground-based flight simulating apparatus
US5134521A (en) * 1990-06-01 1992-07-28 Thomson-Csf Wide-angle display device for compact simulator
FR2718855A1 (fr) * 1994-04-18 1995-10-20 Boisse Serge Lunettes de réalité virtuelle à miroir.
US20100123880A1 (en) * 2008-11-18 2010-05-20 Barco N.V. Collimated visual display with elliptical front projection screen
US20100271698A1 (en) * 2009-04-24 2010-10-28 David Kessler Pupil-expanded volumetric display
UA101444C2 (uk) * 2011-12-06 2013-03-25 Александра Михайловна Москаленко Спосіб юстирування системи візуалізації тренажера

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3784742A (en) * 1971-05-12 1974-01-08 Redifon Ltd Ground-based flight simulating apparatus
US5134521A (en) * 1990-06-01 1992-07-28 Thomson-Csf Wide-angle display device for compact simulator
FR2718855A1 (fr) * 1994-04-18 1995-10-20 Boisse Serge Lunettes de réalité virtuelle à miroir.
US20100123880A1 (en) * 2008-11-18 2010-05-20 Barco N.V. Collimated visual display with elliptical front projection screen
US20100271698A1 (en) * 2009-04-24 2010-10-28 David Kessler Pupil-expanded volumetric display
UA101444C2 (uk) * 2011-12-06 2013-03-25 Александра Михайловна Москаленко Спосіб юстирування системи візуалізації тренажера

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
BARRY G. BLUNDELL: "3D Displays and Spatial Interaction", WALKER & WOOD, vol. I, 2010
K.: NAU: "Aerospace Systems for Monitoring and Control: Materials of the VI International Scientific and Technical Conference", AVIA-2004, vol. 2, 2004, pages 23 - 54
POTAPOVA G. K.; MOSKALENKO M. A.: "Correction of Geometrical Distortions of Images in Visualization Systems of Flight Simulators", PROCEEDINGS OF THE 7 INTERNATIONAL CONFERENCE APPLIED OPTICS, vol. 3, 2006, pages 127 - 132
POTAPOVA G. K.; MOSKALENKO M. A.: "Correction of Geometrical Distortions of Images in Visualization Systems of Flight Simulators, Proceedings of the 7 International Conference Applied Optics", COMPUTER TECHNOLOGIES IN OPTICS, vol. 3, 2006, pages 127 - 132

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10782453B2 (en) 2015-01-21 2020-09-22 Tesseland, Llc Display devices with reflectors
CN110308560A (zh) * 2019-07-03 2019-10-08 南京玛克威信息科技有限公司 Vr设备的控制方法
CN110308560B (zh) * 2019-07-03 2022-09-30 南京玛克威信息科技有限公司 Vr设备的控制方法

Similar Documents

Publication Publication Date Title
KR102600432B1 (ko) 홀로그램 초해상도를 위한 인코딩된 광 에너지 가이딩 요소
KR102077105B1 (ko) 사용자 인터랙션을 위한 디스플레이를 설계하는 장치 및 방법
US9077973B2 (en) Wide field-of-view stereo vision platform with dynamic control of immersive or heads-up display operation
CN103995356B (zh) 一种真实立体感的光场头盔显示装置
CN104007552B (zh) 一种真实立体感的光场头盔显示系统
CN103472589B (zh) 可便携的三维图像显示系统和方法
US9632406B2 (en) Three-dimension light field construction apparatus
CN104094162A (zh) 动态控制沉浸或抬头显示操作的宽视场3d立体视觉平台
CN103261943A (zh) 采用一个或多个菲涅尔透镜的头戴式显示装置
KR20140101385A (ko) 3차원 가상 및 증강 현실 디스플레이 시스템
CN105068659A (zh) 一种增强现实系统
JP5632245B2 (ja) 眼鏡の視野画像表示装置
US20130135310A1 (en) Method and device for representing synthetic environments
US20160165223A1 (en) Light-restricted projection units and three-dimensional display systems using the same
JP6624513B2 (ja) ３次元像表示装置及び３次元像表示方法
CN111751988B (zh) 一种景深调节方法、装置及双目近眼显示设备
WO2015088468A1 (fr) Dispositif pour représentation d'informations visuelles
EP4356181A1 (fr) Composant optique à double réflecteur
CN205103763U (zh) 一种增强现实系统
US20230087464A1 (en) Head up or head mounted display arrangement and a method for presenting at least one image via at least one surface element of a head up or head mounted display arrangement
Viertler et al. Dynamic registration of an optical see-through HMD into a wide field-of-view rotorcraft flight simulation environment
RU2598788C2 (ru) Выполненный с отгибом дисплей для трехмерного представления динамического отображения
CN104598015A (zh) 一种基于智能眼镜的信息共享系统及方法
JP6379474B2 (ja) 眼鏡レンズ評価方法、眼鏡レンズ製造方法および表示方法
JP4790547B2 (ja) 視覚表示装置

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 14806749

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 14806749

Country of ref document: EP

Kind code of ref document: A1