Business Segments (Details) $ in Millions	12 Months Ended
Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)
Business segments
Number of business segments \| segment	1
Flat Panel Display Systems
Geographic Data
Concentration Risk Threshold Percentage	88.00%	80.00%	90.00%
Foreign Countries
Geographic Data
Net sales from outside the United States \| $	$ 8.4	$ 9.4	$ 7.5

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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+ Details