Range-based focus assistance for projection optics
A lighting system capable of providing automated focus assistance for a moving lighting fixture thereof. In one example, a distance-measurement device connected to the moving lighting fixture operates to measure a distance to the projection surface and transmits the measurement to an electronic controller. The electronic controller uses the measurement and a suitable algorithm to determine a focus parameter value for the projection optics. The determined focus parameter value is encoded in a control signal, which is then used to command a motor to move the corresponding component of the projection optics, thereby bringing and/or keeping in focus a pertinent edge of the illuminated area on the projection surface. An example method for automated focus assistance supports cue stack programming, single shot focus assistance, and continuous focus assistance.
1 . An apparatus, comprising:
an optical assembly to project a light beam generated with a first light source onto a projection surface, the optical assembly being movable with respect to the projection surface and including a first lens, a second lens, and a third lens arranged along an optical axis of the optical assembly, the second lens and the third lens being independently translatable with respect to the first lens to different positions along the optical axis;
a distance-measurement device configured to provide a measure of a distance between the optical assembly and the projection surface, the distance-measurement device being movable together with the optical assembly; and
a control circuit configured to determine an estimated position of the third lens with which an edge of an area illuminated by the light beam on the projection surface is in focus, the estimated position being determined based on the measure and further based on an axial position of the second lens,
wherein the distance-measurement device and the optical assembly are translatable together with respect to the projection surface.
2 . The apparatus of claim 1 , further comprising a first motor to translate the third lens along the optical axis,
wherein the control circuit is further configured to operate the first motor to place the third lens into the estimated position.
3 . The apparatus of claim 2 , further comprising:
a frame rotatably connected to a base;
a housing rotatably connected to the frame, with the optical assembly being mounted in the housing;
a second motor to rotate the frame with respect to the base about a first rotation axis; and
a third motor to rotate the housing with respect to the frame about a second rotation axis oriented at a nonzero angle with respect to the first rotation axis,
wherein the distance-measurement device is attached to the housing; and
wherein the control circuit is further configured to operate the second motor and the third motor to move the optical assembly with respect to the projection surface.
4 . The apparatus of claim 3 ,
wherein the base is translatable with respect to the projection surface.
5 . The apparatus of claim 3 ,
wherein the control circuit comprises an electronic controller located in the housing;
wherein the control circuit further comprises a control console configured to control a plurality of lighting fixtures; and
wherein one of the lighting fixtures includes the base, the frame, the housing, the optical assembly, the first motor, the second motor, the third motor, and the electronic controller.
6 . The apparatus of claim 3 , further comprising a movable rig or truss configured to provide two or three degrees of freedom for translating the base with respect to the projection surface.
7 . The apparatus of claim 1 , wherein the distance-measurement device comprises:
a second light source to emit a probe beam toward the projection surface;
a driver circuit to electrically drive the second light source to cause the probe beam to be pulsed, intensity-modulated, or frequency-modulated; and
an optical receiver to detect a returned beam formed by reflections of the probe beam from the projection surface,
wherein the distance-measurement device is configured to obtain the measure by comparing one or more characteristics of the probe beam and the returned beam.
8 . The apparatus of claim 7 ,
wherein the first light source is configured to emit visible light; and
wherein the second light source is configured to emit infrared light.
9 . The apparatus of claim 1 , wherein the distance-measurement device comprises a lidar ranging sensor.
10 . The apparatus of claim 1 , wherein the distance-measurement device is an acoustic distance-measurement device or an ultrasonic distance-measurement device.
11 . The apparatus of claim 1 , wherein the control circuit is configured to determine the estimated position using a lookup table addressable with a pair of values consisting of a distance value and a second-lens position value.
12 . The apparatus of claim 1 , wherein the control circuit is configured to determine the estimated position based on calibration data.
13 . The apparatus of claim 1 , wherein the control circuit is configured to determine the estimated position based on a numerical model of the optical assembly.
14 . The apparatus of claim 1 , wherein the control circuit is configured to determine the estimated position based on an analytical solution of a system of equations describing optical characteristics of the optical assembly.
15 . The apparatus of claim 1 ,
wherein the control circuit includes a multifunctional control console configured to control a plurality of lighting fixtures including a first lighting fixture, with controllable features of the first lighting fixture including a translation movement of the first lighting fixture with respect to the projection surface;
wherein the first lighting fixture includes the optical assembly; and
wherein the distance-measurement device is fixedly attached to the first lighting fixture.
16 . The apparatus of claim 1 , wherein the distance-measurement device is aligned with the optical assembly such that the measure corresponds to a peripheral edge of the area illuminated by the light beam.
17 . The apparatus of claim 1 , wherein the distance-measurement device is aligned with the optical assembly such that the measure corresponds to an interior edge within the area illuminated by the light beam.
18 . A method of providing focus assistance for a lighting fixture, the method comprising:
obtaining, with an electronic processor, a first parameter value representing an axial position of a second lens in an optical assembly including a first lens, the second lens, and a third lens arranged along an optical axis of the optical assembly, the second lens and the third lens being independently translatable with respect to the first lens to different positions along the optical axis;
obtaining, with the electronic processor, a measure of a distance between the lighting fixture and a projection surface, the measure being received from a distance-measurement device, wherein the distance-measurement device and the optical assembly are translatable together with respect to the projection surface; and
determining, with the electronic processor, a second parameter value representing an estimated position of the third lens with which an edge of an area illuminated by the lighting fixture on the projection surface is in focus, the second parameter value being determined based on the measure and further based on the first parameter value.
19 . The method of claim 18 , further comprising:
programming, with the electronic processor, the second parameter value or an adjusted value into a cue, the adjusted value being obtained by changing the second parameter value based on a user input; and
controlling, with the electronic processor, a motor configured to translate the third lens along the optical axis, said controlling causing the motor to place the third lens into a position corresponding to the second parameter value.
20 . A non-transitory computer-readable medium storing instructions that, when executed by at least one processor, cause the at least one processor to perform operations comprising the method of claim 18 .