Convertion of angular distance measured by a camera to perpendicular distance

Good day All

My camera displays 2D array with each pixel value reflecting a distance from the sensor to the corresponding point on the target.

The camera is mounted at 45 degrees to a flat target, thus, the distance measured in the upper pixels appear larger compared to the ones at the lower pixels due camera angulation.

Is there any way that I can convert the distance readings to refelect as if the camera is at 90 degree to the target such that all the pixel values are approximealy the same since the target is flat.

I tried using trigonometry but it seem not correct for all rows

Thanks