Camera assembly providing optical image stabilization
A camera assembly comprises a support structure and an image sensor mounted on a carrier that is suspended on the support structure by at least one plain bearing that allows movement of the carrier and the image sensor relative to the support structure in any direction laterally to the light-sensitive region of the image sensor. An actuator arrangement comprising plural shape memory alloy wires is arranged to move the carrier and the image sensor relative to the support structure for providing optical image stabilisation of the image captured by the image sensor.
1. A camera assembly comprising:
a support structure;
an image sensor mounted on a carrier, the image sensor having a light-sensitive region;
at least one plain bearing comprising a bearing surface on each of the carrier and the support structure, which bearing surfaces bear on each other so as to suspend the carrier on the support structure and allow movement of the image sensor relative to the support structure in any direction laterally to the light-sensitive region of the image sensor;
an actuator arrangement arranged to move the image sensor relative to the support structure in any direction laterally to the light-sensitive region of the image sensor; and
a fluid disposed between the bearing surfaces, wherein:
the fluid is a grease; and/or
the fluid reduces the coefficient of friction between the bearing surfaces and/or improves the thermal contact between the bearing surfaces.
2. The camera assembly according to claim 1 , wherein:
the bearing surfaces are each planar; and/or
the bearing surfaces have a coefficient of friction of 0.2 or less.
3. A camera assembly comprising:
a support structure;
an image sensor mounted on a carrier, the image sensor having a light-sensitive region;
at least one plain bearing comprising a bearing surface on each of the carrier and the support structure, which bearing surfaces bear on each other so as to suspend the carrier on the support structure and allow movement of the image sensor relative to the support structure in any direction laterally to the light-sensitive region of the image sensor;
an actuator arrangement arranged to move the image sensor relative to the support structure in any direction laterally to the light-sensitive region of the image sensor, wherein the actuator arrangement comprises plural shape memory alloy actuator wires that are inclined relative to the light-sensitive region of the image sensor for applying a biasing force that biases the bearing surfaces together.
4. A camera assembly comprising:
a support structure;
an image sensor mounted on a carrier, the image sensor having a light-sensitive region;
at least one plain bearing comprising a bearing surface on each of the carrier and the support structure, which bearing surfaces bear on each other so as to suspend the carrier on the support structure and allow movement of the image sensor relative to the support structure in any direction laterally to the light-sensitive region of the image sensor;
an actuator arrangement arranged to move the image sensor relative to the support structure in any direction laterally to the light-sensitive region of the image sensor,
wherein:
at least one of the bearing surfaces is formed from a material and has a coating having lower friction and/or lower wear than the said material of the bearing surface; and/or
the actuator arrangement comprises plural shape memory alloy actuator wires connected between the support structure and the carrier in an arrangement capable, on selective driving thereof, of moving the image sensor relative to the support structure in any direction laterally to the light-sensitive region of the image sensor.
5. The camera assembly according to claim 4 , wherein:
the at least one plain bearing comprises plural plain bearings; and/or
the at least one plain bearing has a total area of contact that is at least 0.2 times the area of the light-sensitive region of the image sensor; and/or
the at least one plain bearing further allows rotation of the image sensor about an axis orthogonal to the light-sensitive region, and the actuator arrangement is further arranged to rotate the image sensor about said axis.
6. The camera assembly according to claim 4 , further comprising a lens assembly comprising at least one lens arranged to focus an image on the light-sensitive region of the image sensor, the lens assembly being mounted to the support structure, preferably wherein the light-sensitive region of the image sensor has a diagonal length of at most 12 mm.
7. The camera assembly according to claim 4 , further comprising a control circuit arranged to drive the actuator arrangement, and a vibration sensor arranged to generate output signals representative of the vibration of the camera assembly, the control circuit being arranged to drive the actuator arrangement in response to the output signals of the vibration sensor for driving movement of the image sensor to stabilise an image captured thereby.
8. A camera assembly comprising:
a support structure;
an image sensor mounted on a carrier, the image sensor having a light-sensitive region;
at least one plain bearing comprising a bearing surface on each of the carrier and the support structure, which bearing surfaces bear on each other so as to suspend the carrier on the support structure and allow movement of the image sensor relative to the support structure in any direction laterally to the light-sensitive region of the image sensor;
an actuator arrangement arranged to move the image sensor relative to the support structure in any direction laterally to the light-sensitive region of the image sensor; and
a biasing arrangement that biases the bearing surfaces together, wherein the biasing arrangement comprises at least one flexure, and the flexure supports electrical tracks connected to at least the image sensor.
9. The camera assembly according to claim 8 , wherein the support structure includes a support plate formed from sheet material, and the carrier includes a moving plate formed from sheet material, the plain bearing being provided between the support plate and the moving plate.
10. The camera assembly according to claim 9 , wherein:
either or both of the support plate and the moving plate is made of metal; and/or
the bearing surfaces are a surface of the support plate and a surface of the moving plate.
11. The camera assembly according to claim 9 , wherein:
the plain bearing includes a bearing member fixed to one of the support plate and the moving plate, one of the bearing surfaces of the plain bearing being a surface of the bearing member and the other of the bearing surfaces of the plain bearing is a surface of the other of the support plate and the moving plate; and/or
the plain bearing includes bearing members fixed to both of the support plate and the moving plate, the bearing surfaces of the plain bearing being a surface of each bearing member.