The illumined mind becomes purified and reflects objects exactly as they are.

Verse 4.22

चितेरप्रतिसंक्रमायाः तदाकारापत्तौ स्वबुद्धि संवेदनम् ॥२२॥

citeḥ apratisaṃkramāyāḥ tat-ākāra-āpattau sva-buddhi-saṃvedanam ||22||

The essence of knowledge (the Purusa) being un-changeable, when the mind takes its form, it becomes conscious.

Through the accomplishment of pure consciousness comes knowledge of the unchangeable seer who rests on his own intelligence and nowhere else.

When consciousness no longer fluctuates, then its pure nature surfaces to comprehend itself. 

 Mind has two facets, one pure, divine and immutable, the other changeable, transient and exhibitive. It has no light of its own but acts as a medium or agent between the seer and the objects seen. Due to ignorance, it does not realize that it is impersonating the seer. But the seer knows the movements of the mind.

When one facet of mind ceases to operate, it ends its contact

with the external world and stops collecting impressions. The other facet is drawn to the seer, and the two unite. Intelligence and mind merge in their abode - the atman, and the soul comes face to face with itself.

A dirty mirror obscures reflection, a clean mirror reflects objects clearly.

The illumined mind becomes purified and reflects objects exactly as they are. The reflector is called bimba-pratibimba vada, or the exposition of double reflection. 

There is no difference between the source object and the reflected image. The soul reflects the soul. It is the fulfilment of yoga.

Citta is identified with the seer. This is svabuddhi samvedanam or intuitive understanding of the inner voice.

PATANJALI YOGA SUTRAS