Field meter with adjustable lens

Abstract

The perimeter comprises a screen (2), a light source assembly (12), a projection optics (14), and an adjustable beam deflector (16). The projection optics (14) comprises an adjustable lens (26) having a focal length that can be changed by the device's control unit (18). The projection optics (14) further comprises a projection lens element (28). The focal length of the adjustable lens (26) is changed as a function of the position (L, L') of the stimulation light spot, thereby compensating for the position-dependent optical path length from the projection optics (14) to the screen (2). The distance between the projection lens element (28) and the adjustable lens (26) is equal to the focal length of the projection lens element (28), which makes the spot size independent of the position (L, L').

Description

[Technical Field]

[0001] The present invention relates to a perimeter and a method for operating the same.

[0002] In the context of this application, a perimeter is used to examine a patient's subjective visual field. [Background technology]

[0003] A perimeter, such as the one described in Patent Document 1 or 2, comprises a light source, an adjustable deflector, and a screen. The adjustable deflector is used to generate a stimulating light spot at a desired position on the screen for evaluating the sensitivity of the patient's visual field in a particular spatial direction.

[0004] Typically, this type of perimeter device faces the challenge that the optical path length of light depends on the coordinates of the stimulated light spot as it appears on the screen.

[0005] For example, in the case of a spherical screen as shown in Patent Document 1, the patient's eye is typically located at the center of the screen's sphere, and therefore the deflector, such as a set of movable mirrors, is positioned off-axis. Thus, the path length that light must travel from the light source through the deflector to the screen varies depending on the position of the selected screen.

[0006] On the other hand, the projection spot should have substantially the same brightness and size for all screen positions. Therefore, an adaptive optics system is required. For example, Patent Document 3 discloses the use of path length correction implemented using a displaceable mirror. However, this is mechanically complex, and furthermore, operating the mirror generates noise that may startle the patient with a new stimulus, which can in turn affect the accuracy of the examination. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] U.S. Patent No. 4561738 [Patent Document 2] U.S. Patent No. 7475987 [Patent Document 3] European Patent Application Publication No. 1380251

[0008] Therefore, the present invention aims to solve the problem of providing a perimeter and a method of the same that can correct the size of the stimulation light spot in a simple manner.

[0009] This problem is solved by the perimeter and method described in the independent claim.

[0010] Therefore, a perimeter includes at least the following elements: -Screen. This screen is used to receive the stimulating light spot for the patient. - Light source assembly. This light source assembly is adapted to generate visible light used for stimulation. - Projection optics. This projection optics is adapted to process light from a light source and project a stimulating light spot onto a screen. - Adjustable deflector. This adjustable deflector is adapted to deflect light to generate stimulating light spots at multiple selectable coordinates on the screen.

[0011] According to the present invention, the projection optical system comprises a tunable lens whose focal length is adjustable. This lens can be used to quickly and easily correct the focus of the stimulating light spot. Furthermore, it can be controlled as a function of the path length of light from the light source to the screen.

[0012] Advantageously, the projection optical system includes a projection lens element, which is arranged coaxially with the adjustable lens and at a distance from it. This lens element can support the imaging operation of the adjustable lens. Advantageously, it has a fixed focal length.

[0013] In particular, the projection lens element can be a positive lens element. This can, for example, allow a tunable lens to operate at a large focal length (whether positive or negative).

[0014] In such examples, the focal length of the projection lens element is advantageously equal to the axial distance between the adjustable lens and the projection lens element, within ±20%. As shown below, this ensures that the size of the stimulus light spot on the screen is substantially independent of the focal length used for the adjustable lens.

[0015] In other advantageous embodiments, the aperture of the projection optics and deflector combination is selected such that any light beam from the light source, crossing the adjustable lens, reaches the screen. This ensures that the total amount of light at the stimulus point does not change when the focal length of the adjustable lens is varied.

[0016] The light source assembly typically forms an aperture that defines the illumination area projected onto the screen by the projection optics. This aperture is advantageously illuminated uniformly (e.g., with uniformity greater than 25%). Thus, the diameter of this aperture, along with the magnification of the projection optics, determines the diameter of the stimulating light spot.

[0017] This aperture can be formed, for example, by a diaphragm in a Köhler illumination system. Alternatively, it may be formed, for example, by an exit aperture in a multimode light guide path that homogenizes light from a light source.

[0018] Advantageously, the diameter of the stop may be varied, for example by using an adjustable diaphragm to define the stop.

[0019] The perimeter may further comprise a control unit. The control unit is connected to the adjustable lens and the adjustable deflector for controlling them.

[0020] This control unit is advantageously adapted to perform at least the following steps. - Positioning the stimulus light spot at a plurality of positions on the screen by adjusting the adjustable deflector. As described, the optical path length from the light source assembly to the position of the stimulus light spot varies between at least some of these positions. - Adjusting the focal length of the adjustable lens as a function of the path length.

[0021] This scheme provides automatic compensation for varying path lengths.

[0022] Advantageously, the control unit adjusts the focal length of the adjustable lens such that the projection optical system projects the field stop onto the screen for all of the above positions. In other words, the field stop and the screen are maintained in the conjugate plane of the projection optical system for the currently selected position.

[0023] In this example, the projection optical system is advantageously designed to have the same magnification with an accuracy within 20% for all of the above positions.

[0024] The adjustable deflector may advantageously comprise a mirror arranged radially offset from the central axis of the screen to provide the patient with a wide field of view.

[0025] In a simple design, the adjustable deflector features a mirror that can be tilted about a first axis and a second axis, which intersect each other. This allows for the use of only one mirror to adjust the position of the stimulation light spot on the screen in two dimensions.

[0026] Advantageously, for simple computational control, the first and second axes are orthogonal to each other and / or intersect.

[0027] In a simple design, an adjustable deflector includes the following: - A first rotary actuator, such as a stepping motor, having a first shaft that is rotatable about a first axis. - A second rotary actuator, such as a stepping motor, having a second shaft that is rotatable about a second axis. - A first coupler that connects the mirror to the first shaft. It rotationally locks the mirror to the first shaft for rotation around the first axis, but allows the mirror to tilt around a third axis that intersects the first axis. In other words, when the first shaft rotates, the mirror rotates with it, but the mirror can tilt around the third axis. - A second coupler connects the mirror to the second shaft. It rotates and fixes the mirror relative to the second shaft for rotation around the second axis, but allows the mirror to tilt around a fourth axis that intersects the second axis. In other words, when the second shaft rotates, the mirror rotates with it, but the mirror can tilt around the fourth axis.

[0028] In particular, the third axis rotates together with the first shaft around the first axis, and the fourth axis rotates together with the second shaft around the second axis.

[0029] In particular, the third axis is perpendicular to the first axis, and the fourth axis is perpendicular to the second axis.

[0030] The screen of a perimeter is typically rotationally symmetric with respect to the screen axis. To provide a wide field of view to the patient, the first and second rotational actuators are advantageously positioned radially (relative to the screen axis) outward from the mirror. That is, the mirror is closer to the screen axis than the first and second rotational actuators.

[0031] The present invention also relates to a method for operating such a perimeter. The method includes the step of positioning a stimulating light spot at multiple locations on a screen by adjusting an adjustable deflector.

[0032] Advantageously, as described, the optical path length from the light source assembly to the above-mentioned positions varies between at least some of the above-mentioned positions. In this example, the method advantageously includes the step of adjusting the focal length of the adjustable lens as a function of the path length.

[0033] In particular, for the reasons stated above, the method may include the step of adjusting the focal length of an adjustable lens so that the projection optical system projects the field aperture of the light source assembly onto the screen for all of the above positions. [Brief explanation of the drawing]

[0034] The present invention will be better understood and other purposes will become apparent when the following detailed description is considered. Such a description is provided by reference to the accompanying drawings.

[0035] [Figure 1] A schematic diagram of one embodiment of a perimeter and a patient using it is shown. [Figure 2] This shows a cross-sectional view of a perimeter along a vertical plane passing through the central axis of the screen. [Figure 3] This shows an optical element that generates a stimulating light spot on a screen. [Figure 4] This shows one embodiment of an optical deflector. [Figure 5] An embodiment of a light source assembly, an adjustable lens, and a projection lens element is shown. [Figure 6] This shows the distance between the field diaphragm, adjustable lens, projection lens element, and screen along the optical axis of the system. [Modes for carrying out the invention]

[0036] (definition) In this specification, "lens" refers to a single lens or a composite lens.

[0037] A "composite lens" includes multiple single lenses arranged coaxially, where the distance between the lenses is significantly smaller than the focal length of each lens. Advantageously, the single lenses of a composite lens are arranged adjacent to each other in the axial direction; that is, they may even be in contact. As is known to those skilled in the art, the single lenses of a composite lens may have different dispersion characteristics, for example, to produce the effect of an achromatic lens as a whole.

[0038] The term "lens element" can refer to a lens and / or curved mirror having transformation characteristics that can be approximated using the following types of ray matrices, where f is the focal length of the lens element.

[0039]

number

[0040] A controllable liquid lens is a lens whose focal length depends on the curvature of at least one liquid interface. This curvature can be altered by an electric field and / or mechanical means. Advantageously, this curvature can be altered by an electric field applied to the liquid.

[0041] The term "axial direction" refers to the center line from the light source assembly as the light beam travels through the projection optical system.

[0042] The term "axial distance" describes the distance between two components along the axis of a light beam.

[0043] (Overview of perimeter) Figures 1 and 2 show a perimeter having a screen 2 and a projection system 4 for projecting a stimulus light spot onto positions L and L' on the screen 2.

[0044] The perimeter further includes a chin rest or headrest 6 for positioning the patient's head, particularly the patient's eyes, in a predetermined position in front of the screen.

[0045] As is known to those skilled in the art, the screen 2 of a modern perimeter is typically curved to have a central axis 10 of the screen, and the patient's eye is advantageously positioned at a point close to or intersecting the screen axis 10.

[0046] Advantageously, screen 2 is spherical, and the screen axis 10 extends through the center point of the sphere defined by screen 2.

[0047] The projection system 4 comprises a light source assembly 12, a projection optical system 14, and an adjustable deflector 16. The control unit 18 controls the light source assembly 12, the projection optical system 14, and the beam deflector 16 to generate stimulation light spots at multiple positions L, L' on the screen 2.

[0048] To perform a visual field test, the control unit 18 sets the beam deflector 16 to a predetermined position L and adjusts the projection optical system 14 accordingly. This is described in more detail below. It then operates the light source assembly 12 to generate a stimulation light spot of desired brightness and size at position L. The brightness of the stimulation light is varied to determine the visibility threshold. This operation is repeated for multiple positions.

[0049] (Projection system) The projection system 4 is shown in more detail in Figures 3-5.

[0050] As stated, it includes a light source assembly 12 for generating a predetermined light spot. In this embodiment, the light source assembly 12 comprises a light source 20 for generating white light. The light source 20 may be a white LED. Light from the light source 20 is projected onto the field aperture 24 by a lens element 22. These elements advantageously form Köhler illumination, as is known to those skilled in the art.

[0051] The light intensity at the field aperture 24 is advantageously uniform in the sense that it varies within a range of less than 20% across the transparent area of ​​the field aperture 24.

[0052] The field diaphragm 24 is advantageously either an adjustable diaphragm or a revolver-type mechanism having multiple diaphragms of different diameters on a revolver carrier, and the control unit 18 is adapted to change its diameter as needed by the current examination. This makes it possible to present the patient with stimulation light spots of various sizes.

[0053] The projection optical system 14 is adapted to project the field aperture 24 onto the screen 2. That is, the field aperture 24 and the stimulus light spot on the screen 2 are in a conjugate plane with respect to the projection optical system 14 such that the stimulus light spot on the screen 2 is an image of the field aperture 24 and therefore has a well-defined diameter.

[0054] In this embodiment, the projection optical system 14 comprises an adjustable lens 26 and a projection lens element 28, the adjustable lens 26 being positioned between the light source assembly 12 and the projection lens element 28.

[0055] The adjustable lens 26 has an adjustable focal length, which can be controlled, for example, by a control voltage U or control current I generated by the control unit 18.

[0056] The adjustable lens 26 may be a controllable liquid lens. In such a case, the curvature of the liquid interface can be changed by an applied electric field or mechanical means. An example of a field-controllable liquid lens is described in European Patent Application Publication No. 167892, in which the curvature of the interface between two non-mixed liquids can be changed by an electric field.

[0057] In other embodiments, for example, a controllable liquid lens as described in European Patent Application Publication No. 2860555 may be used.

[0058] In further embodiments, lenses using electroactive polymers, such as those described in U.S. Patent No. 1,0007034, may be used.

[0059] For example, the adjustable lens 26 could be a Corning A-series variable-focus liquid lens.

[0060] Advantageously, the adjustable lens 26 does not contain a mechanical motor for quiet operation.

[0061] The projection lens element 28 is a positive lens element, that is, it is a condensing lens element.

[0062] The projection system 4 may further include an auxiliary mirror 30 that projects light from the projection optical system onto the adjustable deflector 16 if the adjustable deflector 16 is not coaxially positioned with the adjustable lens 26 and the projection lens element 28.

[0063] (Adjustable deflector) The adjustable deflector 16 is best shown in Figures 3 and 4.

[0064] In the present embodiment, it comprises a tiltable mirror 36 that can be tilted about a first axis A1 and a second axis A2. As described above, axes A1 and A2 are transverse and intersect. Advantageously, they are perpendicular to each other.

[0065] The first rotary actuator 38-1 and the second rotary actuator 38-2 are provided for rotating the mirror 36. They may be, for example, stepping motors, and their rotational positions may be controlled by the control unit 18.

[0066] The first rotary actuator 38-1 has a first shaft 40-1 that is rotatable about a first axis A1. The first shaft 40-1 is connected to a mirror 36 via a first coupler 42-1. The first coupler 42-1 rotates the mirror relative to the first shaft 40-1 for rotation about the first axis A1, but allows the mirror 36 to tilt about a third axis A3 that intersects the first axis A1. The third axis A3 can be advantageously pivoted parallel to the second axis A2 by rotation about the first axis A1.

[0067] In the current embodiment, the first coupler 42-1 comprises a first arm 44-1a firmly connected to a first shaft 40-1, and a first arched section 44-1b firmly connected to the first arm 44-1a. The first arched section 44-1b is connected to the mirror 36 by one or two rotating bearings 46-1.

[0068] The second rotary actuator 38-2 has a second shaft 40-2 that is rotatable about a second axis A2. The second shaft 40-2 is connected to a mirror 36 via a second coupler 42-2. The second coupler 42-2 rotates the mirror relative to the second shaft 40-2 for rotation about the second axis A2, but allows the mirror 36 to tilt about a fourth axis A4 that crosses the second axis A2. The fourth axis A4 can be advantageously pivoted parallel to the first axis A1 by rotation about the second axis A2.

[0069] In the current embodiment, the second coupler 42-2 comprises a second arched section 44-2 that is firmly connected to the second shaft 40-2. The second arched section 44-2 is connected to the mirror 36 by one or two rotating bearings 46-2.

[0070] The first axis A1 and the second axis A2 are advantageously perpendicular to each other, thereby obtaining the best angular resolution of the mirror 36.

[0071] As shown in Figure 4, they are advantageously symmetrical with respect to the plane 48 of the screen axis 10, that is, with respect to the plane in which the screen axis 10 exists.

[0072] As shown in Figure 2, the mirror 36 can be tilted by rotary actuators 38-1 and 38-2 to guide light from the projection optical system 14 to various positions L and L' on the screen 2.

[0073] The mirror 36 is radially offset from the central axis 10 of the screen 2. Therefore, since it is not located at the center of the spherical screen surface, the path length of light from the projection optical system 14 to the screen 2 is not constant, but a function of positions L and L'. For this reason, the focal length of the adjustable lens 26 is adapted, as will be described in more detail in the following section.

[0074] As can be seen in Figure 2, the first actuator 38-1 and the second actuator 38-2 are positioned radially outward from the mirror 36 with respect to the central axis 10 of the screen 2 (i.e., they are positioned further away from the mirror 36 when viewed from the central axis 10) in order to avoid interference with the patient's field of view.

[0075] (Adjustment of path length) As mentioned in the previous section, the path length of light reaching screen 2 is not constant, but a function of positions L and L'.

[0076] For this reason, the control unit 18 controls the focal length of the adjustable lens 26 as a function of positions L, L' to generate a well-focused stimulation light spot for all positions L, L' on the screen 2. In addition, the projection optical system 14 is adapted to have a magnification independent of positions L, L' and a setting for the focal length of the adjustable lens 26. This will be explained in more detail below.

[0077] This section refers to Figure 6, which schematically shows the projection of the field aperture 24 onto the screen 2 by the adjustable lens 26 and projection lens element 28, and the optical axis 50 of the system is shown as a straight line (in reality, the optical axis 50 is bent by two mirrors 30, 36). The following parameters are used to describe the system. f1: The focal length of the adjustable lens 26. This distance is varied by the control unit 18 as a function of the position L of the stimulus light spot on the screen 2. f2: The focal length of the projection lens element 28. This distance is advantageously fixed. d1: The axial distance between the field aperture 24 and the adjustable lens 26. This distance is advantageously fixed. d2: The axial distance between the adjustable lens 26 and the projection lens element 28. This distance is advantageously fixed. d3: The axial distance between the projection lens element 28 and the screen 2. This distance is a function of position L.

[0078] In the following, the projection system is approximated by ray matrix analysis, where each element is described by its respective ray matrix.

[0079] As is well known to those skilled in the art, a ray matrix (or ABCD matrix) describes how a given element transforms a radial position and the beam angle between its input and output sides. See, for example, https: / / en.wikipedia.org / wiki / Ray_transfer_matrix_analysis.

[0080] The projection system in Figure 6 converts the beam angle α1 and radial position r1 at its input (within the plane of the field aperture 24) to the beam angle α2 and radial position r2 at its output (on the screen 2) as follows.

number

[0081] When the matrices on the right-hand side are multiplied together, they give the following:

[0082]

number

[0083] Here, in equation 3, B must be 0 if it is desired that the output plane be conjugate to the input plane; that is, the following equation must hold.

[0084]

number

[0085] This formula gives the following for the focal length f1 of the adjustable lens 26:

[0086]

number

[0087] The values ​​of f2, d1, and d2 are constant and known. The distance d3 along the optical axis between the projection lens element 28 and the screen 2 can be calculated from the position of the lens element 28, the positions of the mirrors 30 and 36, the position of the screen 2, and the current spot positions L and L'. Thus, the control unit 18 can calculate the focal length f1 of the adjustable lens 26 from equation 5 or an appropriate lookup table and set f1 accordingly. This ensures that the field aperture 24 is focused and projected onto the screen 2.

[0088] In equation 3, A is the magnification coefficient between the input plane and the output plane, that is, between the field diaphragm and the screen.

[0089]

number

[0090] As can be seen, the magnification coefficient A generally depends on the distance d3. Therefore, for the majority of f2, d1, and d2, the control unit 18 needs to adjust the diameter of the field aperture 24 as a function of the current spot positions L, L' to maintain a constant spot size on the screen 2. Furthermore, it also needs to adjust the brightness of the light source 20 to maintain a constant spot brightness. While these measurements are available, they are advantageously avoided.

[0091] Therefore, in a favorable embodiment, the magnification A is selected such that it is independent of d3, i.e., the derivative of A with respect to d3 should be 0.

[0092]

number

[0093] In other words, the following equation should hold true.

[0094]

number

[0095] Therefore, if the focal length f2 of the projection lens element 28 is chosen to be equal to the distance d2 between the projection lens element 28 and the adjustable lens 26, the magnification A of the projection optical system becomes independent of the distance d3.

[0096] Therefore, advantageously, f2 is selected to be equal to d2. In such a case, the control unit 18 only needs to maintain the focal length f1 given by equation 5 in order to produce a well-focused stimulation light spot having constant size and brightness at all positions L, L'.

[0097] The condition f2=d2 does not need to be strictly met. Slight deviations will result in changes in brightness and spot size. According to the ISO standard for visual field measurement, EN ISO 12886:1999 (Ophthalmic instruments-Perimeters), brightness is allowed to vary within the range of -20% to +25%, and spot size is allowed to vary within the range of -15% to +20%. Therefore, advantageously, the focal length f2 of the projection lens element is equal to the axial distance d2 within a range of ±20% of f2.

[0098] During operation, the distance d3 is the minimum value d over the positions L and L' used. 3,min and the maximum value d 3,max It changes between these two points.

[0099] d 3,min d 3,max The value of depends on the geometric shape of the device. Perimeters often use a Goldmann-type screen with a radius of R=300mm (see Figure 2). For the type of geometric shape shown in Figure 2, where the mirror 36 is offset by approximately 100mm from the central axis 10 and the incident light has an angle α of approximately 60° with respect to the central axis 10, the distance d3 typically varies between approximately 550mm and 750mm, as can be calculated.

[0100] For example, adjustable lenses of the type described above are usually best operated at a low curvature, that is, a large or infinite focal length, i.e., f1=∞.

[0101] In other words, the method advantageously comprises the step of setting the focal length of the adjustable lens 26 to be infinite for at least some of the positions L, L'.

[0102] f1=∞ holds when the denominator of Equation 5 is zero. The corresponding value of d3 is as follows.

[0103] [Equation]

[0104] Accordingly, advantageously, the components of the perimeter are configured such that d 3,inf is between d 3,min and d 3,max , that is, arranged such that the following holds.

[0105] [Equation]

[0106] In the case of the embodiment of Equation 8, that is, in the case of d2=f2, the following is obtained.

[0107] [Equation]

[0108] In other words, the above components are advantageously arranged such that d1, d2, d 3,min , d 3,max satisfy the following.

[0109] [Equation]

[0110] Given d1=50mm and d2=160mm, assuming d2=f2, d3=d 3,min =550mm and d3=d 3,max To obtain a focal length of 750mm, the corresponding ranges of the focal length f1 are f1=200mm (+5 diopters) and f1=-328mm (-3 diopters), respectively. In this case, the adjustable lens 26 requires an adjustment range of approximately 8 diopters.

[0111] (Note) In the above embodiment, the deflector has only one mirror that can be tilted about two axes. Alternatively, two independently tiltable mirrors may be used.

[0112] In further embodiments, there may be no tiltable mirror, or the mirror may be tiltable about only a single axis. In such examples, the beam deflector may be implemented by a pivot mechanism that tilts the light source assembly and / or projection optics along at least one or both directions.

[0113] At least one mirror of the adjustable deflector is advantageously a flat mirror. However, it may be a curved mirror, or the mirror 30 may be curved. In such cases, the mirror is considered to form part of the projection optical system, in particular part of the projection lens element.

[0114] In the example above, the projection lens element 28 is a lens. Alternatively, it may be formed solely by a curved mirror, particularly by a curved mirror of an adjustable deflector.

[0115] While currently preferred embodiments of the present invention have been shown and described, it should be clearly understood that the present invention is not limited thereto and can be embodied and practiced in various ways within the scope of the following claims. Furthermore, this disclosure includes the following aspects: [Aspect 1] A perimeter, wherein the perimeter is Screen (2), Light source assembly (12), Projection optical system (14) and It is equipped with an adjustable deflector (16), The projection optical system (14) is a field meter comprising an adjustable lens (26) whose focal length can be adjusted. [Aspect 2] The perimeter according to embodiment 1, wherein the projection optical system (14) comprises a projection lens element (28), the projection lens element (28) being arranged coaxially with the adjustable lens (26) and at a distance from the adjustable lens (26). [Aspect 3] The perimeter according to embodiment 2, wherein the projection lens element (28) is a positive lens element. [Aspect 4] The field meter according to embodiment 3, wherein the focal length (f2) of the projection lens element (28) is equal to the axial distance (d2) between the adjustable lens (26) and the projection lens element (28) within ±20%. [Aspect 5] The perimeter according to any one of embodiments 2 to 4, wherein the adjustable lens (26) is positioned between the light source assembly (12) and the projection lens element (28). [Aspect 6] Equation 10 described herein holds true, d1 is the axial distance between the field aperture (24) of the light source assembly (12) and the adjustable lens (26), d2 is the axial distance between the adjustable lens (26) and the projection lens element (28), f2 is the focal length of the projection lens element (28), and, A perimeter according to any one of embodiments 2 to 5, wherein d3,min and d3,max are the minimum and maximum possible axial distances between the projection lens element (28) and the screen (2). [Aspect 7] A perimeter according to embodiments 4 and 6, wherein formula 12 described herein holds true. [Aspect 8] A perimeter according to any one of embodiments 1 to 7, wherein the apertures of the projection optical system (14) and the deflector (16) are selected to be large enough for any light beam from the light source assembly (12) across the adjustable lens (26) to reach the screen (2). [Aspect 9] The light source assembly (12) is equipped with a field diaphragm (24), and the projection optical system (14) projects the field diaphragm (24) onto the screen (2), according to any one of embodiments 1 to 8. [Aspect 10] The perimeter includes a control unit (18) connected to the adjustable lens (26) and the adjustable deflector (16), and The perimeter is adapted to position the stimulation light spot at multiple positions (L, L') on the screen (2) by adjusting the adjustable deflector (16), and the optical path length from the light source assembly (12) to the positions (L, L') varies between at least some of the positions (L, L'), and The perimeter according to any one of embodiments 1 to 9, further adapted to adjust the focal length of the adjustable lens (26) as a function of the path length. [Aspect 11] The perimeter according to embodiments 9 and 10, wherein the control unit (18) is adapted to adjust the focal length of the adjustable lens (26) so that the projection optical system (14) projects the field diaphragm (24) onto the screen (2) for all of the positions (L, L'). [Aspect 12] The perimeter according to embodiment 11, wherein the projection optical system (14) has the same magnification for all of the positions (L, L'). [Aspect 13] The perimeter according to any one of embodiments 1 to 12, wherein the adjustable deflector (16) includes a mirror (36) that is radially offset from the central axis (10) of the screen (2). [Aspect 14] The adjustable deflector (16) comprises a mirror (36) that can be tilted about a first axis (A1) and a second axis (A2), and the first axis (A1) and the second axis (A2) intersect each other, as described in any one of embodiments 1 to 13. [Aspect 15] The adjustable deflector (16) is A first rotary actuator (38-1) having a first shaft (40-1) that is rotatable about a first axis (A1), A second rotary actuator (38-2) having a second shaft (40-2) that is rotatable about the second axis (A2), A first coupler (42-1) connects the mirror (36) and the first shaft (40-1), wherein the first coupler (42-1) rotates and fixes the mirror (36) relative to the first shaft (40-1) for rotation around the first axis (A1), but allows the mirror (35) to tilt about a third axis (A3) that crosses the first axis (A1), and A second coupler (42-2) connects the mirror (36) and the second shaft (40-2), wherein the second coupler (42-2) rotates and fixes the mirror (36) relative to the second shaft (40-2) for rotation around the second axis (A2), but allows the mirror (36) to tilt around a fourth axis (A4) that crosses the second axis (A2), A perimeter according to embodiment 14, further comprising the above. [Aspect 16] The perimeter according to embodiment 15, wherein the first actuator (38-1) and the second actuator (38-2) are arranged radially outward from the mirror (36) with respect to the central axis (10) of the screen (2). [Aspect 17] The perimeter according to any one of embodiments 14 to 16, wherein the first axis and the second axis are symmetrical with respect to the plane of the screen axis (10). [Aspect 18] The perimeter according to any one of embodiments 1 to 17, wherein the adjustable lens (26) is a controllable liquid lens, and in particular an electric field controllable liquid lens. [Aspect 19] A method for operating a perimeter according to any one of embodiments 1 to 18, comprising the step of adjusting the adjustable deflector (16) to position a stimulation light spot at a plurality of positions (L, L') on the screen (2). [Aspect 20] The optical path length from the light source assembly (12) to the positions (L, L') varies between at least some of the positions (L, L'), and the method is as follows: The method according to embodiment 19, comprising the step of adjusting the focal length of the adjustable lens (26) as a function of the path length. [Aspect 21] The method according to embodiment 20, further comprising the step of adjusting the focal length of the adjustable lens (26) such that the projection optical system (14) projects the field aperture (24) of the light source assembly (12) onto the screen (2) for all of the positions (L, L'). [Aspect 22] The method according to any one of embodiments 19 to 21, wherein the method includes the step of setting the focal length of the adjustable lens (26) to infinity for at least some of the positions (L, L').

Claims

1. A perimeter, wherein the perimeter is Screen (2), Light source assembly (12), A projection optical system (14) is provided, which is configured to process light from the light source assembly (12) and project a stimulating light spot onto the screen (2). It is equipped with an adjustable deflector (16), The projection optical system (14) is An adjustable lens (26) in which the focal length can be adjusted, The system comprises a projection lens element (28), the projection lens element (28) being arranged coaxially with the adjustable lens (26) and at a distance from the adjustable lens (26), The projection optical system (14) projects the field aperture (24) of the light source assembly (12) onto the screen (2), The projection lens element (28) is a positive lens element, and the focal length (f) of the projection lens element (28) ２ ) is the axial distance (d) between the adjustable lens (26) and the projection lens element (28). ２ ) are equal within ±20%, and The adjustable lens (26) is positioned between the light source assembly (12) and the projection lens element (28) in a field meter.

2. A perimeter, wherein the perimeter is Screen (2), Light source assembly (12), A projection optical system (14) is provided, which is configured to process light from the light source assembly (12) and project a stimulating light spot onto the screen (2). It is equipped with an adjustable deflector (16), The projection optical system (14) is An adjustable lens (26) in which the focal length can be adjusted, The system comprises a projection lens element (28), the projection lens element (28) being arranged coaxially with the adjustable lens (26) and at a distance from the adjustable lens (26), The projection optical system (14) projects the field aperture (24) of the light source assembly (12) onto the screen (2), and the following equation holds true: d １ This is the axial distance between the field aperture (24) and the adjustable lens (26) of the light source assembly (12), d ２ This is the axial distance between the adjustable lens (26) and the projection lens element (28), f ２ This is the focal length of the projection lens element (28), and, d ３，ｍｉｎ and d ３，ｍａｘ A field meter in which the minimum and maximum possible axial distances are between the projection lens element (28) and the screen (2). [Math 1]

3. The focal length of the projection lens element (28) (f ２ ) is equal to the axial distance (d between the adjustable lens (26) and the projection lens element (28) ２ ) within ±20%, and The perimeter according to claim 2, wherein the following formula holds true. [Math 2]

4. The perimeter according to claim 1 or 2, wherein the apertures of the projection optical system (14) and the adjustable deflector (16) are selected to be large enough for any light beam from the light source assembly (12) across the adjustable lens (26) to reach the screen (2).

5. The perimeter includes a control unit (18) connected to the adjustable lens (26) and the adjustable deflector (16), and The control unit (18) is adapted to position the stimulation light spot at a plurality of positions (L, L') on the screen (2) by adjusting the adjustable deflector (16), and the optical path length from the light source assembly (12) to the positions (L, L') varies between at least some of the positions (L, L'), and The field meter according to claim 1 or 2, wherein the control unit (18) is further adapted to adjust the focal length of the adjustable lens (26) as a function of the path length.

6. The perimeter includes a control unit (18) connected to the adjustable lens (26) and the adjustable deflector (16), and The control unit (18) is adapted to position the stimulation light spot at a plurality of positions (L, L') on the screen (2) by adjusting the adjustable deflector (16), and the optical path length from the light source assembly (12) to the positions (L, L') varies between at least some of the positions (L, L'), and The control unit (18) is further adapted to adjust the focal length of the adjustable lens (26) as a function of the path length, and The perimeter according to claim 1 or 2, wherein the control unit (18) is adapted to adjust the focal length of the adjustable lens (26) such that the projection optical system (14) projects the field diaphragm (24) onto the screen (2) for all of the positions (L, L').

7. The perimeter according to claim 6, wherein the projection optical system (14) has the same magnification for all of the positions (L, L').

8. The perimeter according to claim 1 or 2, wherein the adjustable deflector (16) includes a mirror (36) that is radially offset from the central axis (10) of the screen (2).

9. The adjustable deflector (16) comprises a mirror (36) that can be tilted about a first axis (A1) and a second axis (A2), wherein the first axis (A1) and the second axis (A2) intersect each other, as described in claim 1 or 2.

10. The adjustable deflector (16) is A first rotary actuator (38-1) having a first shaft (40-1) that is rotatable about the first axis (A1), A second rotary actuator (38-2) having a second shaft (40-2) that is rotatable about the second axis (A2), A first coupler (42-1) connects the mirror (36) and the first shaft (40-1), wherein the first coupler (42-1) rotates and fixes the mirror (36) relative to the first shaft (40-1) for rotation around the first axis (A1), but allows the mirror (36) to tilt about a third axis (A3) that crosses the first axis (A1), A second coupler (42-2) connects the mirror (36) and the second shaft (40-2), wherein the second coupler (42-2) rotates and fixes the mirror (36) relative to the second shaft (40-2) for rotation around the second axis (A2), but allows the mirror (36) to tilt around a fourth axis (A4) that intersects the second axis (A2), The perimeter according to claim 9, further comprising:

11. The perimeter according to claim 10, wherein the first rotary actuator (38-1) and the second rotary actuator (38-2) are arranged radially outward from the mirror (36) with respect to the central axis (10) of the screen (2).

12. The perimeter according to claim 9, wherein the first axis and the second axis are symmetrical with respect to the plane of the central axis (10) of the screen (2).

13. The perimeter according to claim 1 or 2, wherein the adjustable lens (26) is a controllable liquid lens.

14. A method for operating a perimeter according to any one of claims 1 to 13, comprising the step of adjusting the adjustable deflector (16) to position a stimulation light spot at a plurality of positions (L, L') on the screen (2).

15. The optical path length from the light source assembly (12) to the positions (L, L') varies between at least some of the positions (L, L'), and the method is as follows: The method according to claim 14, comprising the step of adjusting the focal length of the adjustable lens (26) as a function of the path length.

16. The method according to claim 15, further comprising the step of adjusting the focal length of the adjustable lens (26) such that the projection optical system (14) projects the field aperture (24) of the light source assembly (12) onto the screen (2) for all of the positions (L, L').

17. The method according to claim 14, further comprising the step of setting the focal length of the adjustable lens (26) to infinity for at least some of the positions (L, L').

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