4. Goodwill and Intangible Assets

The changes in the carrying value of goodwill for the six month period ended December 31, 2018 are as follows (in thousands):


					Optoelectronics
					and
	Security		Healthcare		Manufacturing
	Division		Division		Division		Consolidated
Balance as of June 30, 2018	$	191,810	$	40,157	$	60,246	$	292,213
Goodwill acquired or adjusted during the period		6,541		—		7,415		13,956
Foreign currency translation adjustment		(65)		(102)		(838)		(1,005)
Balance as of December 31, 2018	$	198,286	$	40,055	$	66,823	$	305,164

Intangible assets consisted of the following (in thousands):


		June 30, 2018						December 31, 2018
	Weighted	Gross						Gross
	Average	Carrying		Accumulated		Intangibles		Carrying		Accumulated		Intangibles
	Lives	Value		Amortization		Net		Value		Amortization		Net
Amortizable assets:
Software development costs	9 years	$	28,174	$	(9,423)	$	18,751	$	29,215	$	(11,597)	$	17,618
Patents	19 years		8,401		(1,618)		6,783		8,243		(1,680)		6,563
Developed technology	10 years		52,780		(9,706)		43,074		54,582		(12,480)		42,102
Customer relationships/backlog	7 years		63,398		(17,891)		45,507		65,673		(20,494)		45,179
Total amortizable assets			152,753		(38,638)		114,115		157,713		(46,251)		111,462
Non-amortizable assets:
Trademarks and trade names			25,596		—		25,596		26,450		—		26,450
IPR&D			2,290		—		2,290		2,290		—		2,290
Total intangible assets		$	180,639	$	(38,638)	$	142,001	$	186,453	$	(46,251)	$	140,202

Amortization expense related to intangible assets was $4.5 million and $5.6 million for the three month periods ended December 31, 2017 and 2018, respectively. For the six months ended December 31, 2017 and 2018, amortization expense was $8.7 million and $10.9 million, respectively. .At December 31, 2018, the estimated future amortization expense was as follows (in thousands):


2019 (remaining 6 months)	$	9,960
2020		19,634
2021		19,281
2022		14,670
2023		13,448
Thereafter, including assets that have not yet begun to be amortized		34,469
Total	$	111,462

Software development costs for software products incurred before establishing technological feasibility are charged to operations. Software development costs incurred after establishing technological feasibility are capitalized on a product-by-product basis until the product is available for general release to customers at which time amortization begins. Annual amortization, charged to cost of goods sold, is the amount computed using the ratio that current revenues for a product bear to the total current and anticipated future revenues for that product. In the event that future revenues are not estimable, such costs are amortized on a straight line basis over the remaining estimated economic life of the product. Amortizable assets that have not yet begun to be amortized are included in Thereafter in the table above. For the three months ended December 31, 2017 and 2018, we capitalized software development costs in the amount of $0.2 million and $0.6 million, respectively. For the six month periods ended December 31, 2017 and 2018, we capitalized software development costs in the amount of $0.3 million and $1.0 million, respectively.