Optical arrangement for compensation of thermally-induced astigmatism of lens

An apparatus, comprising:

• a sample stage region;
• an optical assembly including:
• an objective element providing a field of view, at least a portion of the sample stage region being within the field of view, the objective element having an astigmatism that is variable based on a temperature of the objective element,
• a tube lens, the tube lens being configured to receive light transmitted through the objective element and further transmit the light through an image space,
• a first compensating element in the image space, the first compensating element being configured to induce a second astigmatism,
• a second compensating element in the image space, the second compensating element being configured to induce a third astigmatism, the second and third astigmatisms being configured to cooperate to offset the variable astigmatism;
• and
• a camera assembly configured to receive light transmitted from the compensating assembly.

A method comprising:

• receiving light from a reaction site through an objective element, the objective element having an astigmatism, the light passing further through a compensation assembly, the compensation assembly providing a compensating astigmatism, the compensating astigmatism offsetting the astigmatism of the objective element;
• heating the objective element, the astigmatism of the objective element changing in response to the heating;
• and
• adjusting the compensation assembly to thereby change the compensating astigmatism, thereby offsetting the changing astigmatism of the objective element.