40 ILCS 5/5-158
A policeman whose disability continues beyond the maximum period of eligibility for disability benefit and who withdraws while still disabled and before age 50, shall receive annuity as can be provided from the amounts accumulated from salary deductions and sums contributed by the city for his retirement annuity. The annuity shall be computed as of the age of the policeman on the date of his withdrawal.
The annuity to which the wife of any such policeman has a right from the date of his death shall be fixed as of her age on the date of his withdrawal. It shall be the amount provided from the total to his credit for widow's annuity.
Upon the death of a policeman after he has entered upon annuity, any unmarried child under age 18 shall have a right to receive annuity as herein specified for a child of a policeman, subject to the limitations on amounts payable to the family of a policeman.
40 ILCS 5/5-158